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Traditional
Poster Session - Pulse Sequences & Reconstruction B |
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Off-Resonance Artifact Correction
Click on
 to view
the abstract pdf. Click on 
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
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Exhibition Hall |
16:00 - 18:00 |
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2405. |
Fast, Variable System
Delay Correction for Spiral Trajectories
Payal Sharad Bhavsar1, Nicholas Ryan Zwart1,
and James Grant Pipe1
1Neuroimaging Research, Barrow Neurological
Institute, Phoenix, Arizona, United States
Spiral encoding methods may exhibit image artifacts due
to system delays and eddy current. This papers extends a
previous approach to estimate time-varying system delays
for stack-of-spirals based trajectories, reducing the
computational time by a factor of 30. The proposed
method is very fast, easy to implement, includes
gradient coupling effects, is robust to off-resonance,
and estimates delays for each gradient channel over the
data acquisition time.
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2406. |
k-Space Shift Correction
Using an Alternating Gradient Readout Acquisition for
Improved Radial Fat-Water MRI
Xuelin Cui1, John C. Gore2, and E.
Brian Welch2
1Biomedical Engineering, Vanderbilt
university, Nashville, TN, United States, 2Radiology
and Radiological Sciences, Vanderbilt University,
Nashville, TN, United States
A primary challenge associated with the radial MRI
sampling trajectory is the imperfect alignment of each
sampled diagonal with the center of k-space. Gradient
imperfections and timing delay errors cause the sampled
trajectory to shift from the intended trajectory.
Methods exist to align miscentered k-space samples for
alternating radial readouts to the center of k-space by
comparing neighboring radial lines that have nearly
opposite readout direction. In this work, an alternating
readout direction phase correction algorithm for radial
MRI is tested on a conventional single gradient echo
acquisition and a multiple fast field echo (mFFE)
acquisition used for fat-water imaging.
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2407. |
Evaluation of chemical
shift based fat suppression using 2DRF pulses
Rainer Schneider1,2, Thorsten Speckner1,
Jens Haueisen2, and Josef Pfeuffer1
1Siemens Healthcare, Erlangen, Germany, 2Institute
of Biomedical Engineering and Informatics, TU Ilmenau,
Ilmenau, Germany
Custom-designed spatial spectral pulses (SPSP) have been
shown to suppress fat signal effectively by taking
advantage of chemical shift along the fast direction.
However, the proper design of such SPSP pulses depends
on many variables and their performance was never
evaluated so far. In this work, a simplified
implementation of this approach and a detailed
performance evaluation is done. Reduced FOV
diffusion-weighted images subject are acquired in
phantom and human and compared to two other
state-of-the-art fat suppression techniques. In
conclusion, the proposed approach demonstrated here can
offer the best compromise regarding residual fat signal
and acquisition speed.
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2408. |
Through-Plane Chemical
Shift Correction in Rf-Power Reduced Sequences at High Field
Strength
Mathias Nittka1, Vladimir Jellus1,
and Lars Lauer1
1Siemens Healthcare, Erlangen, Germany
Application of low power, low bandwidth rf-pulses in
slice selective sequences at high field strength may
lead to severe through-plane chemical shift artifacts of
fat signal. The presented methods uses a fat/water
separating DIXON turbo spin echo sequence to generate
through-plane chem. shift corrected images.
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2409. |
Chemical-shift selective
multislice imaging using the gradient reversal technique
Yeji Han1, Yoojin Lee1, ChangHyun
Oh1, and HyunWook Park1
1Department of Electrical Engineering, Korea
Advanced Institute of Science and Technology, Daejeon,
Korea
The chemical shift phenomenon can produce severe
artifacts of geometric shift or blurring in MRI. Instead
of treating the chemical shift phenomenon as a source of
artifact, many imaging technologies, including the
gradient reversal (GR) technique, have been developed to
acquire separate sets of images from tissues of
different resonance frequencies. Although the GR method
has not been widely used, recent reports have confirmed
the effectiveness of this method for fat suppression at
3.0T and higher field. In this abstract, we expand the
concept of the GR technique to acquire multislice
chemical-shift selective images.
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2410. |
An Investigation of
Fundamental Pitfall in SSGR
Axel Hartwig1, and Stefan Skare1
1Clinical Neurosience, Karolinska Institute,
Stockholm, Sweden
SSGR is a time efficient and robust fat suppression
technique that achieves fat suppression by displacing
fat during slice-selection. Fat suppression is achieved
by displacing excitation and refocusing pulses in
opposite directions. This work shows how, depending on
slice-selection direction, displaced excitations and
refocusing pulses may interact and form an unwanted echo
during acquisition of latter slices. The birth of the
echo is investigated and two methods to eliminate it are
discussed.
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2411. |
Global and spatially
varying B0 drifts
due to gradient system heating
Karl-Heinz Herrmann1, Martin Krämer1,
and Jürgen R Reichenbach1
1IDIR I, Medical Physics Group, Jena
University Hospital, Jena, Germany
EPI is sensitive to B0 drifts
and especially if the phase encoding direction changes
as in PROPELLER EPI, images can suffer from severe blur
if B0 shifts
are not compensated. However, heating up the gradients
during DTI or fMRI scans causes not only global drifts
of B0, which are easy to compensate once
known, but also spatially varying B0changes
of up to 30Hz.
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2412. |
An automatic real-time
feedback calibration of RF phase cycling by off-resonance
weighted imaging sequence
Yu-Wei Tang1, Teng-Yi Huang1,
Ming-Long Wu2, and Cheng-Wen Ko3
1Electrical Engineering, National Taiwan
University of Science and Technology, Taipei, Taiwan, 2Computer
Science and Information Engineering, National Cheng Kung
University, Tainan, Taiwan, 3Computer
Science and Engineering, National Sun Yat-sen
University, Kaohsiung, Taiwan
The adjustment of system frequency or RF phase-cycling
has demonstrated able to avoid dark-band artifact of
bSSFP imaging. The optimal frequency can be detected by
a sweep scan of bSSFP imaging. In this study, we
proposed a new sequence named off-resonance weighted
imaging (OWI) for accomplishing the frequency
calibration. For higher accuracy and efficiency, an
automatic real-time feedback optimization system was
introduced. According to the results, the automatic
real-time feedback system shows able to calibrate
frequency accurately and rapidly. It is potential to
serve as a pre-scan for bSSFP imaging or blood
oxygenation sensitive SSFP (BOSS) fMRI.
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2413. |
Deblurring of spiral
images in the presence of fat and rapidly varying B0
Eric Aboussouan1, and James G. Pipe1
1Neuroimaging Research, Barrow Neurological
Institute, Phoenix, Az, United States
Spiral imaging with long acquisition windows is
efficient but highly susceptible to off-resonance
blurring artifacts. Iterative approaches to deblurring
in the presence of fat and/or rapidly varying field are
presented. Deblurring results of real and synthesized
images are compared favorably to results of a common
non-iterative deblurring approach.
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2414. |
Off-resonance Correction
for 3D Cones Imaging Using Multifrequency Interpolation
Wendy W Ni1,2, Holden H Wu1,3, and
Dwight G Nishimura1
1Department of Electrical Engineering,
Stanford University, Stanford, California, United
States, 2Department
of Radiology, Stanford University, Stanford, California,
United States, 3Department
of Cardiovascular Medicine, Stanford University,
Stanford, California, United States
In this study, we extended the multifrequency
interpolation (MFI) algorithm to three dimensions (3D)
and performed off-resonance correction for the 3D cones
trajectory. Using an emulated low-resolution field map
of isotropic 5 mm resolution, we have demonstrated the
feasibility of MFI in both phantom and in vivo data of
isotropic 1 mm resolution, achieving significant
improvements in image contrast and detail.
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2415. |
A Simple Acquisition
Strategy to Remove Off-Resonance Blurring in Spiral Imaging
Samuel Fielden1, Xue Feng1, and
Craig Meyer1,2
1Biomedical Engineering, University of
Virginia, Charlottesville, Virginia, United States, 2Radiology,
University of Virginia
Spiral imaging has been hampered by off-resonance
blurring since its inception. Here we show that
redundant spiral-in/spiral-out trajectories naturally
correct for the most severe off-resonance artifacts in a
simple way.
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2416. |
An XS-Guided Solution for
bSSFP Banding Artifact Correction with Reduced Scan Time
Michael Nicholas Hoff1, and Qing-San Xiang1,2
1Physics, University of British Columbia,
Vancouver, British Columbia, Canada, 2Radiology,
University of British Columbia, Vancouver, British
Columbia, Canada
bSSFP imaging is plagued by banding and general signal
modulation stemming from off-resonance-induced phase
accumulation. The geometric cross-solution (XS)
eliminated all these artifacts using four phase cycled
datasets; here a weighted solution of two phase cycled
datasets coupled with weighting guide data is proposed.
Weights are found by minimizing the regional
differential energy of the solution from a low
resolution XS guide. Weighting guided by 25% of the XS
k-space phase encodes yields excellent signal
demodulation, and uses a scan time comparable to the
acquisition of only 2.5 regular bSSFP images.
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2417. |
Signal Demodulation of
bSSFP Imaging with a Two-Point Algebraically Weighted
Solution
Michael Nicholas Hoff1, and Qing-San Xiang1,2
1Physics, University of British Columbia,
Vancouver, British Columbia, Canada, 2Radiology,
University of British Columbia, Vancouver, British
Columbia, Canada
Banding and general signal modulation disturb the
diagnostic viability of bSSFP imaging. Previous
algebraic and geometric techniques have shown that
complete signal demodulation is possible with four phase
cycled bSSFP images. Here a two-image algebraic solution
is employed to demodulate signal and to guide an
improved Algebraically Weighted Solution (AWS). The AWS
uses regional least squares processing to reduce
residual banding. Relative to a gold standard reference
image, the AWS exhibits 60% or less error than a
two-image complex sum in all scenarios tested. AWS
represents a viable bSSFP demodulation solution which is
especially valuable for time-sensitive imaging.
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2418. |
View Angle Tilting for
Distortion Compensated EPI: Effects of RF Pulse Width on
Image Blurring and Slice Profile
Cheng Li1, Felix Wehrli1, and Hee
Kwon Song1
1Radiology, University of Pennsylvania,
Philadelphia, PA, United States
This work describes the implementation of the VAT
methodology for EPI sequences as a means to eliminate
in-plane distortions. Results demonstrate that a
relatively long RF pulse, on the order of the duration
of the total EPI readout period, is necessary to
minimize image blurring. However, the reduced in-plane
blurring is achieved at the cost of increased slice
profile distortion.
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2419. |
Combination of VAT and
Z-shimming in Echo Planar Imaging for Distortion Correction
and Signal Recovery
Sinyeob Ahn1, and Xiaoping Hu1
1Biomedical Engineering, Georgia Institute of
Technology/Emory University, Atlanta, GA, United States
Image distortion and signal loss are detrimental
artifacts caused by field inhomogeneity in gradient-echo
EPI (GE-EPI). This work describes the combination of
view angle tilting (VAT) with z-shimming to address both
artifacts in GE-EPI. VAT was implemented with parallel
imaging to make it practical for EPI. VAT corrects
in-plane distortion in the phase-encoding direction
while z-shimming reduces signal loss. The combined
sequence was used to generate images with improved
quality, particularly in the frontal and inferior
orbito-frontal regions of human brain.
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2420. |
Comparison of EPI
geometric distortion correction using Field mapping and
forward/reverse phase encoding directional EPI scans
Wanyong Shin1, Erik Beall1, Ken
Sakaie1, and Mark Lowe1
1Radiology, Cleveland Clinic, Cleveland, OH,
United States
Since EPI images with forward (for.)/reverse (rev.)
phase encoding (PE) directions provide voxel shifts in
opposite directions, several approaches have been
proposed to calculate voxel displacement (VD) map in PE
direction using the two, in short, 2PE method here.
Since both field map (FM) and 2PE methods generate VD
maps, the direct voxel-wise comparison of VD maps
between FM and 2PE method would provide the
comprehensive insight of pros/cons of 2PE. In this
study, we compare VD maps from FM and 2 PE methods, and
demonstrate their performance and limitation.
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2421. |
Distortion correction
using the susceptibility based field map estimation in echo
planar imaging reconstruction
Hiroyuki Takeda1, and Boklye Kim1
1Radiology, University of Michigan, Ann
Arbor, MI, United States
Reconstructed EPI images suffer from geometric
distortion often due to the magnetic field inhomogeneity
and significantly undermine the performance of activity
analyses. In this work, we focus on a fundamental
approach of the susceptibility-induced magnetic field
inhomogeneity map to retrospectively recover the spin
density map for EPI image reconstruction. By modeling
the acquisition process, we identify the effect of the
field inhomogeneity to the EPI reconstruction, and then
obtain distortion-free density images using a
regularized least-square method. Result shows that our
approach works effectively for recovering the original
undistorted image with an accurate estimate of the field
map.
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2422. |
Application of k-space
energy spectrum analysis to artifact correction in PROPELLER
EPI
Zhengguo Tan1, and Nan-kuei Chen2
1Department of Biomedical Engineering, Duke
University, Durham, North Carolina, United States, 2Brain
Imaging and Analysis Center, Duke University, Durham, NC
- North Carolina, United States
The sequence that integrates PROPELLER and EPI has
proven valuable for studies that require high throughput
and tolerance to subject motion. However, the PROPELLER-EPI
quality is usually degraded by distortions resulting
from background susceptibility field gradients. Although
the distortion can potentially be corrected through B0
mapping, it is not easy to use a conventional B0 mapping
procedure to quantify the field inhomogeneities that may
change from blade to blade due to subject motion. The
goal of this study is to characterize the B0 field
inhomogeneity patterns directly from each blade of the
PROPELLER-EPI data using the k-space energy spectrum
analysis.
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2423. |
Identification of
over-estimated diffusion coefficients obtained with very
high b-values in diffusion MRS
Vaclav Brandejsky1, Roland Kreis1,
and Chris Boesch1
1Depts Clinical Research and Radiology,
University of Bern, Bern, Switzerland
Eddy currents are prohibitive for high b-value diffusion
measurements in vivo. A method for quantitation of the
eddy current effects on balanced diffusion gradient
pairs is presented. Both the remaining eddy currents and
the signal drop due to suboptimal rephasing can be
assessed.
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2424. |
Correction of in-plane
intra-voxel dephasing effects in gradient echo images.
Peter van Gelderen1, Jacco A de Zwart1,
and Jeff H Duyn1
1Advanced MRI Section, LFMI, NINDS, National
Institutes of Health, Bethesda, MD, United States
Macroscopic B0 field gradients may result in signal
dropouts in gradient echo images obtained at high field,
and obscure the information reflecting local tissue
structure and composition. While several methods exist
to correct for these dropouts, we demonstrate that
improved correction is possible with a simple method
that better takes into account the effects of in-plane
dephasing effects.
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2425. |
Correction of gradient
echo images for first and second order macroscopic signal
dephasing using phase derivative mapping
Hendrik de Leeuw1, and Chris J.G. Bakker1
1Image Sciences Institute, Utrecht, Utrecht,
Netherlands
Gradient Echo MRI is frequently applied for its inherent
sensitivity to mesoscopic field inhomogeneities, which
reflect local tissue properties. Unfortunately,
macroscopic field inhomogeneities, such as
inhomogeneities invoked by air cavities, interfere with
the mesoscopic effects. Compensation methods typically
lack flexibility (need precise, object dependent, scan
adjustments), lengthen data acquisition (additional
reconstructions, acquisitions) or is not generally
applicable (multi-echo only). Herein a generally
applicable (single, multi-echo) post-processing method
is presented which compensates for first and second
order macroscopic phase incoherences, while preserving
mesoscopic effects. The method is demonstrated on a
phantom containing mesoscopic field disturbers and the
head of a volunteer.
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2426. |
A comprehensive Gaussian
Process framework for correcting distortions and movements
in diffusion images
Jesper L. R. Andersson1, Junquian Xu2,
Essa Yacoub2, Edward Auerbach2,
Steen Moeller2, and Kamil Ugurbil2
1FMRIB, Oxford, Oxfordshire, United Kingdom, 2Center
for Magnetic Resonance Research (CMRR), University of
Minnesota, Minnesota, Minneapolis, United States
Registration based approaches to correcting for eddy
current distortions and movements are complicated by the
images containing different information. Possible
solutions to this is i) To collect pairs of dwis with
opposite polarity diffusion gradients, ii) To collect
pairs of dwis with opposite polarity phase-encoding or
iii) To register observed dwis to model based
predictions. We present a method that include any and
all of those sources of information depending on how the
data was collected. It utilises Gaussian Processes to
predict dwis and to predict eddy currents for one
acquisition given other acquisitions.
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2427. |
Segmented Trajectory
Correction for Non-Cartesian Imaging with Ramp-up
Acquizaiton
Zhang Qiong1, Weng De he1, and Liu
Wei1
1Siemens, Shen Zhen, Guang Dong, China
Eddy currents can be a significant impediment for
application of oblique non-Cartesian techniques In
permanent MRI system, In our work, eddy current
distorted k-space was divided into two segments, and an
effective approach to align peripheral k-space segment
has been presented, which use physical gradient delays
to counteract trajectory errors accumulated in oblique
period. After that, eddy current induced trajectory
errors were restricted in center non Lineal area, and
the aligned peripheral k-space segment shows isotropic
density, which makes the entire image reconstruction
more stable and further saving time.
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2428. |
Static Magnetic Field
Inhomogeneity Correction of Radial MRI Using an Alternating
Gradient Readout Acquisition
Xuelin Cui1, John C. Gore2,3, and
E. Brian Welch2,3
1Biomedical Engineering, Vanderbilt
university, Nashville, TN, United States, 2Radiology
and Radiological Sciences, Vanderbilt University,
Nashville, TN, United States, 3Institute
of Imaging Science, Vanderbilt University, Nashville,
TN, United States
Static magnetic field (B0) inhomogeneity is one of the
major causes of artifacts in MRI. Although numerous
correction methods have been implemented for Cartesian
k-space, relatively little investigation has been
conducted for radial MRI. B0 inhomogeneity can cause
signal displacement in image space along the frequency
encode direction. In this work, a previously described
reverse gradient method (Fitzpatrick JM et al., IEEE TMI,
1992) is applied to correct radial MRI data without
prior knowledge of the B0 inhomogeneity.
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2429. |
Field-Corrected MP-SWIRLS
for 3D Isotropic High-Resolution T1-weighted Brain Imaging
Yunhong Shu1, Joshua D Trzasko2,
Armando Manduca2, and Matt Bernstein2
1Radiology, Mayo Clinic, Rochester, MN,
United States, 2Mayo
Clinic
We demonstrate that off-resonance correction (ORC) can
help mitigate image blurring that arises from the long
readout of the MP-SWIRLS technique. An in vivo
experiment suggests that MP-SWIRLS with ORC can provide
robust and efficient 3D isotropic high-resolution
T1-weighted brain imaging.
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Traditional
Poster Session - Pulse Sequences & Reconstruction B |
|
Metal Artifact Correction
Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
|
Exhibition Hall |
16:00 - 18:00 |
|
|
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2430. |
Pure phase encode MRI in
the vicinity of metal structures
Hui Han1,2, Igor Mastikhin1, Bryce
MacMillan1, and Bruce Balcom1
1MRI Centre, Department of Physics,
University of New Brunswick, Fredericton, NB, Canada, 2Brain
Imaging and Analysis Center, Duke University Medical
Center, Durham, NC, United States
The presented work shows the robustness of pure phase
encode MRI to B0 field inhomogeneity by showing 3D
SPRITE phantom images of samples with significant metal
content. The paper also outlines the robustness of
SPRITE to the gradient eddy currents induced by
switching pulsed field gradients, which has enabled new
high pressure MRI study inside metallic containers at
variable temperature and pressure condition. An eddy
current self-compensated SPRITE sequence allows us to
acquire geometrically correct images inside highly
conductive cylindrical metal containers.
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2431. |
Spectrally Resolved Fully
Phase-Encoded 3D Fast Spin-Echo for Metal Artifact Reduction
and Spectroscopic Imaging
Nathan S Artz1, Diego Hernando1,
Valentina Taviani1, Kevin Johnson2,
Jean H Brittain3, and Scott B Reeder1,2
1Department of Radiology, University of
Wisconsin, Madison, WI, United States, 2Department
of Medical Physics, University of Wisconsin, Madison,
WI, United States, 3Global
Applied Science Laboratory, GE Healthcare, Madison, WI,
United States
The purpose of this work was to develop a
spectrally-resolved, fully phase-encoded 3D fast
spin-echo technique that eliminates all
frequency-encoding-related shift artifacts and permits
spectral data sampling at each spin-echo. A sphere
containing gadolinium was placed in water and imaged
with both this method and conventional 3D-FSE. Signal
modeling produced distortion-free proton density and B0
maps with the proposed method, in contrast to the
conventional 3D-FSE images. Dipole effects were also
visible both in the estimated B0 map and the
spectroscopic images. Lastly, a hip prosthesis was well
visualized without distortion while conventional 3D-FSE
demonstrated severe distortion artifacts.
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2432. |
MR Imaging near metallic
implants using Selective Multi-Acquisition with Variable
Resonances Image Combination
Chiel J. den Harder1, Ulrike A. Blume1,
and Clemens Bos2
1MR Advanced Solutions, Philips Healthcare,
Best, Netherlands, 2MR
Clinical Science, Philips Healthcare, Best, Netherlands
With a substantial part of the population having metal
implants, there is a clear need for MR imaging resistant
to metal artifacts. SEMAC and MAVRIC have been shown to
significantly reduce susceptibility artifacts, at the
cost of increased scan time. MAVRIC, especially, has
been described as spatially non-selective with
clinically unacceptable long scan times depending on
anatomy size. This work proposes a spatially selective
MAVRIC variant (sMAVRIC) that retains the well-defined
spectral selectivity of spectral bins, and enables scan
time reduction, without the risk of back-folding.
Spatial and spectral selectivity are determined by
sequence parameters and independent of implant material.
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2433. |
Comparison of 2D
Spin-Echo, Spin-Echo Multi-Spectral Imaging, and Ultra-wide
Bandwidth 3D Radial Techniques for Imaging near Metal
Kevin M Koch1, Kevin F King1,
Michael Carl2, and Graeme C McKinnon1
1Applied Science Laboratory, GE Healthcare,
Milwaukee, WI, United States, 2Applied
Science Laboratory, GE Healthcare, San Diego, CA, United
States
Imaging near metal hardware has become a routine
clinical need in the MR community. There are a variety
of factors that dictate which techniques can succeed in
performing this task with acceptable levels of image
artifact. Here, we compare standard high-bandwidth 2D
spin echo approaches with two alternative methods,
spin-echo Multi-Spectral Imaging (MSI), and
ultra-high-bandwidth zero-TE 3D-radial imaging. Images
were acquired on a gridded total hip replacement phantom
at 3T. It is shown that spin-echo MSI techniques are
able to substantially reduce artifacts compared to 2D
spin-echo, but the 3D-radial techniques suffer from
substantial image artifacts due to the severe warping of
encoded projections
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2434. |
MR Imaging Near Metal With
3D UTE-MAVRIC Sequences
Michael Carl1
1GE Healthcare, San Diego, CA, United States
The potential of using a MAVRIC-like combination of
images obtained at different spectral frequencies with
UTE sequences rather than FSE sequences for imaging in
the presence of metal was investigated. Phantom and
in-vivo studies were performed. UTE-MAVRIC sequences
were able to significantly reduce typical artifacts near
metal implants and detect very short T2 signals not seen
with clinical pulse sequences. Thus, UTE-MAVRIC may
further improve the diagnostic capability MR near metal
implant, by visualizing short T2 tissues such as
tendons, ligaments and cortical bone.
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2435. |
Local Gradient Effects on
Spectral Binning of 3D Multi-Spectral Images Near Metal
Implants
Kevin M Koch1, Pauline Worters2,
and Brian A Hargreaves2
1Applied Science Laboratory, GE Healthcare,
Milwaukee, WI, United States, 2Department
of Radiology, Stanford University, Stanford, CA, United
States
3D Multi-Spectral Imaging (MSI) methods can
substantially reduce MR susceptibility artifacts
commonly found near metal implants. MSI techniques
excite and independently encode a multitude of spectral
"bins" or, spectral-spatial volumes, and then add these
bins together to form a composite image. MSI techniques
must carefully choose spectral bin windowing strategies
to provide a smooth composite image. Near metal, regions
are often encountered that possess strong gradients that
disrupt encoding processes applied even in MSI
techniques. Here, we address the effect of these strong
gradients on MSI spectral binning strategies.
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2436. |
Multi-Spectral Imaging
Near Metal: Understanding Performance Differences Between
1.5T and 3.0T
Kevin M Koch1, Matthew F Koff2,
and Hollis G Potter2
1Applied Science Laboratory, GE Healthcare,
Milwaukee, WI, United States, 2Department
of Radiology and Imaging, Hospital for Special Surgery,
New York, NY, United States
Initial clinical investigations have focused on applying
Multi-Spectral Imaging (MSI) techniques near metal at
1.5T. Recent clinical probes applying MAVRIC-SL MSI
technique at 3.0T have also shown encouraging results.
Here, we demonstrate the performance impact of MAVRIC SL
at 1.5T vs 3.0T. The observed performance difference
between the two field strengths is explained, and a
modification to MAVRIC-SL is proposed to improve
performance at 3T. The results indicate that MAVRIC-SL
substantially reduces susceptibility artifacts and can
be applied effectively at both field strengths. However,
the image quality of MAVRIC-SL, or any MSI technique,
will consistently be better at 1.5T compared to 3T
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2437. |
Quantification of Image
Distortion of Orthopedic Materials in Magnetic Resonance
Imaging
Matthew F Koff1, Parina Shah1,
Kevin M Koch2, and Hollis G Potter1
1Department of Radiology and Imaging - MRI,
Hospital for Special Surgery, New York, New York, United
States, 2Applied
Science Laboratory, General Electric Healthcare,
Waukesha, Wisconsin, United States
Susceptibility artifacts occur when performing MRI
around orthopedic hardware. This study evaluated the
magnitude of in-plane and through plane image distortion
produced by a variety of orthopaedic implant materials
in standard-of-care 2D fast-spin-echo (FSE) images and
multi-acquisition variable-resonance image combination (MAVRIC)
images. Metal test samples produced the largest
distortion fields, with the largest distortions closest
to the sample. MAVRIC scans reduced the in-plane and the
through plane image distortions as compared to FSE
scans. This study quantitatively evaluated the
significant image distortion reduction capabilities of
MAVRIC imaging.
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|
Traditional
Poster Session - Pulse Sequences & Reconstruction B |
|
Artifacts & Correction: Misc.
Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
|
Exhibition Hall |
16:00 - 18:00 |
|
|
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2438. |
A 3D Parametric Model for
Imaging Normalization
Tiejun Zhao1, and Kwan-Jin Jung2
1Siemens Healthcare USA; Siemens Medical
Solutions USA, Inc., Pittsburgh, PA, United States, 2Psychology,
Carnegie-Mellon University, Pittsburgh, PA, United
States
Multi-channel receiving (Rx) coils have become a
standard asset of routine MR imaging due to its improved
signal-to-noise ratio and the parallel imaging
capabilities. However, the image intensity variations
from the receiving profile could be problematic for
tissue segmentations and various quantification
analyses. While the pre-scan normalization that acquires
additional data using body coil provided a popular
approach for removing this imaging shading artifact, a
retrospective normalization can still be invaluable
especially when the extra data is not available due to
various reasons (e.g., the original protocol did not
include a pre-scan for normalization or a uniform body
coil is not available for some head only scanners or
current most 7T scanners.) In this abstract, we proposed
and demonstrated a simple 3D parametric model for
modeling and removing the smooth image intensity
variations presented in images acquired with
multi-channel Rx coil.
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2439. |
Evaluation of MR Image
Intensity Inhomogeneity Correction Algorithms
Jinghua Wang1, Lili He2, and
Zhong-lin Lu3
1Center for Cognitive and Behavioral Brain
Imaging, The Ohio State Univeristy, Columbus, Ohio,
United States, 2Center
for Perinatal Research, Nationwide Children's Hospital,
Columbus, Ohio, United States, 3Center
for Cognitive and Behavioral Brain Imaging, The Ohio
State University, Columbus, Ohio, United States
MR image intensity inhomogeneity has rendered
quantitative MRI analysis in anatomical studies a major
challenge. Various methods for performing inhomogeneity
correction have been proposed. Evaluation of these
methods has often relied on subjective assessment
because of the lack of the ground truth. Here, we
present a new method to evaluate four popular
inhomogeneity correction methods based on both uniform
phantom and in vivo brain images. We found that the
field map method outperformed the others. This method
can be used to guide parameter optimization for existing
correction methods, improve bias field modeling, and
evaluate and optimize new correction methods.
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2440. |
3D Variable Flip Angle
Fast-Low-Angle-Shot Experiments in the Presence of B1
Inhomogeneity and Slab-Select Gradient
Kelly C McPhee1, and Stefan A Reinsberg1
1Physics and Astronomy, University of British
Columbia, Vancouver, BC, Canada
Variable Flip Angle (VFA) Fast-Low-Angle-Shot (FLASH)
experiments are commonly used for T1 and B1 mapping. Due
to the effect of non-ideal pulse shape on signal
intensities, 3D experiments are often used in place of
2D experiments. We show the effects of this assumption
through both simulations and experimental data. The
shape of the VFA curve is altered, and a zero-crossing
will only be observed in the real part of the signal –
not in the magnitude – of a FLASH VFA curve. We compare
T1 and flip angle map results to a VFA experiment with
no slab-select-gradient, and find large T1 errors.
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2441. |
Software-based automated
measurement of susceptibility artifacts on magnetic
resonance images
Andreas Heinrich1, and Felix Guettler1
1Department of Radiology, University Hospital
Jena, Jena, Thuringia, Germany
A platform independent software system (SAM) for rapid,
objective and reproducible measurement of susceptibility
artifacts, complying with ASTM F2119-07, was developed.
The artifact of a defined titanium cylinder was imaged
in a Siemens Magnetom Avanto. For evaluation purposes 13
probands determined the greatest artifact, manually with
a ruler (Osirix) and with the SAM software, which could
reduce the dispersion of the results by more than 80%.
Furthermore, the SAM software safes 50% of MR
measurement time, since the required ASTM reference
images without test object are no longer necessary.
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2442. |
FreeSurfer Parcellation of
Brains Containing Large Infarcts
Niharika Gajawelli1, Sinchai Tsao1,
Darryl Hwang1, Bryce Wilkins1,
Stephen Kriger2, and Manbir Singh1
1Radiology and Biomedical Engineering,
University of Southern California, Los Angeles,
California, United States, 2Center
for Imaging of Neurodegenerative Diseases, VA Medical
Center, San Francisco, California, United States
FreeSurfer parcellation of the T1 weight human brain
often fails in the presence of cerebral infarcts. This
study presents a method of using voxels from the
contralateral hemisphere to fill-in the cerebral
infarct. The technique relied on SPM normalization
including the normal and the hemispherically flipped
versions of the brain, without any manual intervention
other than an initial masking. A novel validation
methodology was developed based on comparing ratios of
FreeSurfer parcellated regions in a simulation study
where the ground truth was known. Results show
successful processing of 16 stroke subjects after
filling, whereas processing in half failed before
filling.
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2443. |
A semi-automatic k-space
despiking algorithm for the removal of striping artefacts in
MR images
Adrienne E Campbell1,2, Oliver Josephs3,
Mark F Lythgoe1, Roger J Ordidge4,
and Dave L Thomas5
1Centre for Advanced Biomedical Imaging,
Division of Medicine and Institute of Child Health,
University College London, London, United Kingdom, 2Department
of Medical Physics and Bioengineering, University
College London, London, United Kingdom, 3University
College London and Birkbeck College, London, United
Kingdom, 4Centre
for Neuroscience, University of Melbourne, Melbourne,
Australia, 5Department
of Brain Repair and Rehabilitation, UCL Institute of
Neurology, University College London, London, United
Kingdom
Striping artefacts are a common in MR images and are
caused by RF noise spikes in k-space. We present a
semi-automatic post-processing algorithm for the removal
of RF spikes from k-space, while preserving quantitative
information. The algorithm detects spikes by taking
advantage of their brief duration and random appearance.
Then, removal of this anomalous data and replacement
with suitable substitute data takes place, while
protecting the centre of k-space. This algorithm was
found to effectively remove RF spikes, improving image
quality and retaining quantitative information.
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2444. |
Simple Method for
Attenuation of Streaking Artifacts from Peripheral Intensity
Accumulation
Kai Tobias Block1, and Matthias Fenchel2
1Department of Radiology, NYU Langone Medical
Center, New York, NY, United States, 2Siemens
AG Healthcare Sector, Erlangen, Germany
Images acquired with radial k-space sampling frequently
suffer from mild or severe streaking artifacts even if
the Nyquist sampling requirements are fulfilled. Often,
the streaking artifacts arise from high-intensity signal
spots in the periphery of the field-of-view. This work
describes a simple method to attenuate such
long-distance streaks by constraining the image
contributions from each coil element to only those areas
where the element is known to have sufficient
sensitivity. The method works fully automatic, does not
affect the SNR or prolong the scan time, and achieved
clear improvement of the image quality in volunteer
studies.
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2445. |
Towards real-time 4D field
shift predictions: optimizing Fourier-based calculations of
the susceptibility induced perturbation of the magnetic
field
J. G. Bouwman1, J. S. van Gorp2,
P. R. Seevinck3, and C. J.G. Bakker3
1Image Sciences Institute - Radiology, UMC
Utrecht, Utrecht, Netherlands, 2UMC
Utrecht, Netherlands, 3UMC
Utrecht
Upspeeding the Fourier-Based calculation of the
suceptibility induced field. A higher level of
efficiency can be gained if the alias prevention by
zero-padding is decoupled from the actual field
calculation. This can be done by afterwards estimating
this aliasing in a lower resolution. This 'virtual'
zero-padding is more than three times faster compared to
conventional zero-padding, with only minor accuracy
loss. This algorithm is especially applicable in dynamic
field shift calculations.
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2446. |
Improved
diffusion-weighted body imaging using high-order eddy
current correction and smart combination
ZHIQIANG LI1, Dan Xu2, and Kenichi
Kanda1
1MR Engineering, GE Healthcare, Waukesha, WI,
United States, 2Applied
Science Laboratory, GE Healthcare, Waukesha, WI, United
States
Single-shot DW-EPI of the liver has the drawback in
signal loss due to cardiac motion. Smart combination has
been proposed to mitigate this issue, but requires
double spin-echo diffusion to avoid mis-registration
between the individual source images acquired with
single spin echo (SSE) diffusion, with the trade-off in
SNR. High-order eddy-current (HOEC) correction has been
presented to minimize the mis-registration in data
acquired with SSE. In this work, we apply both HOEC
correction and smart combination on SSE DW-EPI to
demonstrate the feasibility of generating liver image
with high SNR, minimal signal loss and mis-registration.
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2447. |
PROPELLER-EPI improved by
2D phase cycled reconstruction
Hing-Chiu Chang1,2, Nan-Kuei Chen3,
Tzu-Chao Chuang4, Chun-Jung Juan5,
Ming-Long Wu6,7, and Hsiao-Wen Chung2,5
1Global Applied Science Laboratory, GE
Healthcare, Taipei, Taiwan, 2Institute
of Biomedical Electronics and Bioinformatics, National
Taiwan University, Taipei, Taiwan, 3Brain
Imaging and Analysis Center, Duke University, Durham
North Carolina, United States, 4Electrical
Engineering, National Sun Yat-sen University, Taiwan, 5Department
of Radiology, Tri-Service General Hospital, Taipei,
Taiwan, 6Institute
of Medical Informatics, National Cheng Kung University,
Taiwan, 7Department
of Computer Science and Information Engineering,
National Cheng Kung University, Taiwan
PROPELLER-EPI consists of EPI signal readout, where the
phase inconsistencies between odd and even echoes
generate oblique N/2 ghost artifact in each rotating
blade. A 2D phase-cycled reconstruction for inherent
correction of N/2 ghost without any extra reference scan
has been reported recently. In this work, we integrate
an improved version of the 2D phase-cycled
reconstruction to PROPELLER-EPI, and compare the result
to that reconstructed using the 2D reference-based
method. 2D phase-cycled reconstruction is particularly
suitable for correcting oblique ghost in PROPELLER-EPI
without any need of extra reference scan, and thus may
broaden the clinical use of the PROPELLER-EPI technique.
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2448. |
PROPELLER with Echo
Stabilization
ZHIQIANG LI1, Dawei Gui1, Ajeet
Gaddipati1, and Xiaoli Zhao1
1MR Engineering, GE Healthcare, Waukesha, WI,
United States
PROPELLER has been widely used in the clinic, but also
experiences the violation of the Carr-Purcell-Meiboom-Gill
condition as in FSE, which degrades the signal. FSE
employs phase correction to measure the phase error and
adjust the data acquisition accordingly. However, its
direct application in PROPELLER is not feasible since
measurement at all blade angles leads to unacceptable
increase in scan time. In this work, a model based on
physical gradient is proposed so that the phase error
can be predicted from measurement at a few blade angles.
This reduces scan time, helps the application of
PROPELLER in body/MSK imaging.
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2449. |
Rician Noise Removal in
Diffusion Kurtosis Imaging
Nanjie Gong1, Chun Sing Wong1, Sau
May Wong2, and Bart ter Haar Romeny2
1Diagnostic Radiology, The University of Hong
Kong, Hong Kong, China, 2Biomedical
Engineering, University of Technology Eindhoven,
Netherlands
In the past decade, many denoising algorithms have been
proposed for MR images. Most often the Gaussian filter
is used for this purpose. However it has already been
proven that noise on the magnitude MR images is not
Gaussian, but Rician distributed. Gaussian filters are
used in general for the reason that the noise
distribution of magnitude MR images with high
signal-to-noise ratio (SNR) can be well approximated
with a Gaussian distribution. Diffusion Kurtosis Imaging
(DKI), an extension of Diffusion Tensor Imaging (DTI),
generates images with a lower SNR compared to images
obtained with DTI due to the need of larger and more
b-values. Subsequently the noise distribution in
obtained DKI MR images can no longer be treated as
Gaussian distributed. In this study, two Rician filters,
namely the non-local mean Rician filter (NLM) and the
non-local maximum likelihood filter (NLML), and Gaussian
filter are investigated on their denoising performance
on DKI MR images. Results obtained from the simulations
show more accurate derived parameters from DKI images
denoised with the Rician filters than those from images
denoised with the Gaussian filter. In addition,
regarding the parameters� value derived from real human
data, there are significant differences between those
from data filtered with the Rician filters and those
from data filtered with Gaussian filter.
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2450. |
MRI-Based Attenuation and
Background Correction in Nuclear Projection Imaging
Mark Jason Hamamura1, Seunghoon Ha1,
Werner W Roeck1, James Hugg2, Dirk
Meier3, Bradley E Patt2, and Orhan
Nalcioglu1,4
1Tu & Yuen Center for Functional
Onco-Imaging, University of California, Irvine, CA,
United States, 2Gamma
Medica, Inc., Northridge, CA, United States, 3Gamma
Medica, Inc., Fornebu, Norway, 4Department
of Cogno-Mechatronics Engineering, Pusan National
University, Pusan, Korea
Accurate radiotracer quantification in nuclear
projection imaging requires both attenuation and
background corrections. In this study, we acquired MR
and nuclear projection images of a phantom using a novel
MR-SPECT system. The MRI was then used to facilitate
correction of the nuclear projection data. The results
demonstrate improved accuracy for radiotracer
quantification using data acquired from simultaneous
imaging.
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2451. |
A data-driven framework
for removing physiological noise in fMRI
Nathan Churchill1, and Stephen Strother2
1Medical Biophysics, University of Toronto,
Toronto, Ontario, Canada, 2University
of Toronto / Rotman Research Institute, Toronto,
Ontario, Canada
We have developed a multivariate, data-driven framework
to estimate and control physiological noise in
functional MRI. This model (1) identifies and
down-weights sources of pulsatile flow (e.g. arteries,
sinuses and ventricles), based on a map of
high-frequency spectral power, correlated with an atlas
of potential artifact regions. It then (2) regresses out
physiological noise present in grey matter, using an
adaptation of Canonical Correlation Analysis and the
spatial weights derived from Step (1). This denoising
procedure consistently reduces activation false
positives, and increases both prediction accuracy and
reproducibility of activation maps in subsequent
analyses.
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2452. |
A Robust Algorithm
Framework for Small DTI Samples
Ivan Maximov1, Farida Grinberg1,
and N. Jon Shah1,2
1Institute of Neuroscience and Medicine 4,
Forschungszentrum Juelich GmbH, Juelich, Germany, 2RWTH
Aachen University, Department of Neurology, Faculty of
Medicine, JARA, Aachen, Germany
Low redundancy DTI data sets are a rather complicated
problem for diffusion tensor estimation, especially in a
clinical human brain imaging. The diffusion signal
attenuations are frequently corrupted by a physiological
noise such as a cardiac pulsation, bulk head motion,
respiratory motion, etc. As a consequence, diffusion
tensor estimation becomes unstable and very poor. We
have developed fitting algorithms based on the least
trimmed squares and the median absolute deviation robust
estimators in order to improve the tensor assessment in
small DTI samples.
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2453.
 |
A modified variable fip
angle using a predefiend slice profile in a consecutive
interleaved EPI
Dae-Hun Kang1, Jun-Young Chung1,
Da-Eun Kim1, Young-Bo Kim1, and
Zang-Hee Cho1
1Neuroscience Research Institute, Gachon
University of Medicine and Science, Incheon, Korea
We re-calculated a VFA considering a predefined slice
excitation profile without changing RF excitation pulse
by a computer simulation. By applying a modified VFA to
consecutive interleaved multi-shot EPI (ciEPI) schemes,
a intersegment magnitude variation was reduced and a SNR
of images was improved.
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2454. |
Fat Fraction Bias
Correction using T1 estimates
and Flip Angle Mapping
Issac Y. Yang1, Yifan Cui2, Curtis
N. Wiens2, Trevor P. Wade1, and
Charles A. McKenzie1,2
1Medical Biophysics, University of Western
Ontario, London, Ontario, Canada, 2Physics
and Astronomy, University of Western Ontario, London,
Ontario, Canada
Fat fraction quantification with IDEAL requires the use
of small flip angles to minimise T1 bias
and therefore has reduced SNR. We employed rapid flip
angle mapping to improve T1 bias
correction for high flip angle acquisitions in the
estimation of spinal bone marrow fat fraction in
volunteers. We compared fat fraction estimation with 2
and 8 degree flip angles, with and without bias
correction based on flip angle mapping. The results show
the fat fractions corrected for high flip angle induced
T1 bias
have improved accuracy and precision compared to a low
flip angle acquisition.
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2455. |
Spike noise removal in MR
images using over sampling
Yongchuan Lai1, and Xiaocheng Wei1
1GE Healthcare, Beijing, China
MR images are reconstructed from K space raw data.
Sometimes K space raw data can be corrupted with high
amplitude value noise, resulting gross striation
artifact. This noise is referred as spike noise. The
causes of these spikes can be arcing, loose connection
or other electrical/mechanical problems in system. Spike
noise is difficult to diagnosis and usually it is cost
and time consuming job to fix a spike noise issue.
Over-sampling is widely used in current MR products.
Usually, over-sampled data are directly filtered to
avoid alias artifact in frequency direction. In method
of this abstract, over-sampled data are used not only to
avoid alias but also to find spike noise.
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2456. |
Characterization of NIST/ISMRM
MRI System Phantom
Stephen E Russek1, Michael Boss1,
Edward F Jackson2, Dominique L Jennings3,
Jeffrey L Evelhoch4, Jeffrey L. Gunter5,
and A. Gregory Sorensen6
1NIST, Boulder, CO, United States, 2M
D Anderson Cancer Center, Houston, TX, United States, 3Massachusetts
General Hospital, United States, 4Merck
Research Laboratories, 5Mayo
Clinic, Rochester, MN, United States, 6Siemens
Healthcare, United States
An MRI system phantom has been developed through
collaboration between the ISMRM ad-hoc committee on
Standards for Quantitative Magnetic Resonance and the
National institute of Standards and Technology (NIST).
This will be the first system phantom with SI-traceable
components and the first to be monitored by NIST for
stability and accuracy. The system phantom consists of
the following elements: fiducial , T1, T2, proton
density arrays; resolution, slice profile, and SNR
insets. The system phantom is designed to assess scanner
performance and quantitative mapping protocols and to
easily compare performance with other scanners across
the world. The system phantom has been imaged
extensively at Mass General Hospital and M D Anderson
Cancer Center in a variety of 1.5 and 3T scanners.
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Traditional
Poster Session - Pulse Sequences & Reconstruction B |
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Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
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Exhibition Hall |
16:00 - 18:00 |
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2457. |
Enhanced Motion Correction
Combining PROPELLER and Parallel Imaging
Yi Guo1, Xiaoke Wang2, Sheng Fang3,
Kui Ying4, Hua Guo5, and Shi Wang4
1Dept.of Electrical Engineering, Tsinghua
University, Beijing, Beijing, China, 2Dept.of
Biomedical Engineering, Tsinghua University, 3Institute
of nuclear and new energy technology, Tsinghua
University, 4Dept.of
Engineering Physics, Tsinghua University, 5Center
for Biomedical Imaging Research, Tsinghua University
In this study we proposed a method to combine parallel
imaging (PI) with PROPELLER to correct non-rigid motion
in addition to rigid motion either within a blade or
between blades. Instead of using PI techniques to speed
up MR acquisition, here the data redundancy in fully
sampled PI is exploited to detect and eliminate corrupt
k-space lines, thus to correct a variety of motion. We
use CG-PROPELLER to reconstruct the image from
multi-coil PROPELLER data, and then split back to
original k-space blades. By comparing the difference
between the regenerated and original lines for all
blades, corrupt lines are detected and discarded. The
final image is then reconstructed from the under-sampled
data using CG-PROPELLER. Both phantom and in-vivo
results show the feasibility of enhanced non-rigid
motion correction.
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2458. |
Motion Correction of a new
T1-w Propeller Sequence (SE-prop)
Stefan Skare1
1Dept of Clinical Neuroscience, Karolinska
Institutet, Stockholm, Sweden
A new propeller sequence is presented for motion-robust
imaging with T1-w contrast, SE-prop. In SE-prop, the
core sequence is the same as the Cartesian Spin-Echo,
with one phase encoding line of a given blade read out
per TR. While motion between the blades can be corrected
using image realignment similar to other propeller
sequences, motion may now also occur within a blade.
Means to overcome this is presented.
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2459. |
High Temporal Resolution
3D Motion Correction of MP-RAGE with Cylindrical Sampling
and Parallel Reconstruction
Wei Lin1, Qin Qin2,3, Feng Huang1,
and Randy Duensing1
1Invivo Corporation, Philips Healthcare,
Gainesville, Florida, United States, 2Department
of Radiology, The Johns Hopkins University, Baltimore,
Maryland, United States, 3F.M.
Kirby Research Center, Kennedy Krieger Institute,
Baltimore, Maryland, United States
A self-navigated method for motion correction in
multicoil imaging applications, involving both data
collection and reconstruction, is presented. The
cylindrical k-space is collected using multiple pairs of
orthogonal view planes with a bit-reversed radial angle
ordering scheme. A rapid self-calibrated parallel
imaging method, generalized GRAPPA Operator for Wider
readout Lines (GROWL), facilitates both motion detection
and image reconstruction. Full 3D rigid-body motion
detection is achieved at a temporal resolution of every
two consecutive view planes (2-6 seconds). The efficacy
of the proposed technique is demonstrated in healthy
volunteers using a magnetization-prepared rapid gradient
echo (MP-RAGE) sequence.
|
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2460. |
Respiratory Gated VIBE
Sequence
Alto Stemmer1, MunYoung Paek2,
Jeong Min Lee3, and Berthold Kiefer1
1Healthcare Sector, Siemens AG, Erlangen,
Germany, 2Siemens
Ltd. Seoul, Korea, 3Seoul
National University, Korea
The aim of this work is to describe a recently developed
navigator gated 3D spoiled gradient echo sequence (VIBE)
for high resolution liver imaging during the uptake
phase of hepatobiliary contrast media. Radial phase
encoding allows a flexible choice of the number of TR
intervals per navigator/fat suppression pulse and hence
temporal resolution of the respiratory curve. An
extended PAWS gating algorithm is used to ensure
robustness in the case of a varying breathing pattern.
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2461. |
Blind Retrospective Motion
Correction of MR Images
Alexander Loktyushin1, Hannes Nickisch2,
Rolf Pohmann3, and Bernhard Schölkopf1
1Max Planck Institute for Intelligent
Systems, Stuttgart, Germany, 2Philips
Research Laboratories, Hamburg, Germany, 3Max
Planck Institute for Biological Cybernetics, Tübingen,
Germany
Patient motion in the scanner is one of the most
challenging problems in MRI. We propose a new
retrospective motion correction method for which no
tracking devices or specialized sequences are required.
We seek the motion parameters such that the image
gradients in the spatial domain become sparse. We then
use these parameters to invert the motion and recover
the sharp image. In our experiments we acquired 2D TSE
images and 3D FLASH/MPRAGE volumes of the human head.
Major quality improvements are possible in the 2D case
and substantial improvements in the 3D case.
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2462.
|
Non-rigid Motion
Correction in 3D Using Autofocusing with Localized Linear
Translations
Joseph Y. Cheng1, Marcus T. Alley2,
Charles H. Cunningham3,4, Shreyas S.
Vasanawala2, John M. Pauly1, and
Michael Lustig5
1Electrical Engineering, Stanford University,
Stanford, California, United States, 2Radiology,
Stanford University, Stanford, California, United
States, 3Medical
Biophysics, University of Toronto, Toronto, Ontario,
Canada, 4Imaging
Research, Sunnybrook Health Sciences Centre, Toronto,
Ontario, Canada, 5Electrical
Engineering and Computer Science, University of
California, Berkeley, California, United States
MR scans are sensitive to motion effects due to the scan
duration. On a sufficiently small spatial-scale, the
complex non-rigid motion can be well approximated as
simple linear translations. This formulation allows for
a practical autofocusing algorithm that locally
minimizes a given motion metric -- more specifically,
the proposed localized gradient-entropy metric. To
reduce the vast search space for an optimal solution,
possible motion paths are limited to motion measured
from multi-channel Butterfly navigation data. The
correction scheme is applied to free-breathing abdominal
patient studies. A reduction in artifacts from non-rigid
motion is observed.
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2463. |
Reduction of Breathing
Motion Artifacts in Shoulder Imaging using an Orbital
Navigator as Motion Sensor
Tim Nielsen1, Chiel den Harder2,
Clemens Bos3, and Peter Börnert1
1Philips Research, Hamburg, Germany, 2Philips
Healthcare, Best, Netherlands, 3University
Medical Centre, Utrecht, Netherlands
A breathing motion artifact reduction method is
demonstrated which can be applied to a clinical shoulder
imaging protocol and 1.) uses an orbital navigator (onav)
signal to sense the breathing motion and 2.) uses a
reconstruction from a reduced dataset to improve image
quality. The motion signal from the navigator is used to
control which data are used in the reconstruction. Using
only the sub-set of data where motion is minimal can
significantly reduce ghosting and blurring.
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2464. |
On moving coil encoding
and calibration in dynamic imaging
Johannes F.M. Schmidt1, Peter Boesiger1,
and Sebastian Kozerke1
1Institute for Biomedical Engineering,
University and ETH Zurich, Zurich, Switzerland
Image reconstruction of multi-channel coil data is based
on sensitivity maps for receive coils retrieved from
either a pre-scan or by autocalibration of sensitivities
from the scan itself. The implications of moving objects
and moving coils on reconstruction performance with
static coil sensitivity maps are shown on basis of
simulated free-breathing contrast enhanced myocardial
perfusion imaging.
|
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2465. |
Adaptive respiratory
triggering for high spatial and temporal resolution 3D DCE-MRI
in the mouse.
Alexandr Khrapichev1, Veerle Kersemans1,
Danny Allen1, and Sean Smart1
1Oxford University, Oxford, Oxfordshire,
United Kingdom
A method for performing high temporal and spatial
resolution imaging for DCE-MRI in the mouse is
presented. Respiration triggering is used to reduce
motion artefact, and dummy scans are used to regenerate
the T1 steady state following each breath. Both the rate
and depth of the breathing change over the duration of a
typical DCE-MRI scan so the numbers of dummy and imaging
acquisitions per breath may need to vary in order to
maximise data capture rate whilst avoiding motion. 3D
gradient echo scans with an isotropic resolution of ca.
400 micron and a temporal resolution of 5 s (untriggered)
and 8-9 s (triggered) is achieved. Respiratory gated and
non gated scans of the mouse abdomen and thorax were
acquired sequentially during the uptake from a single
bolus injection of Gd contrast agent. Improvements to
signal-to-noise and image fidelity are shown when using
triggering.
|
2466.
|
Multimodal non-rigid
motion artifact correction with concurrent ultrasound
Jihan Kim1, and Dosik Hwang1
1School of Electrical and Electronic
Engineering, Yonsei University, Seoul, Korea
This abstract provides a novel multi-modal imaging
framework to compensate complicated motion artifacts in
MR. Results prove the feasibility of our proposed
method. This method can correct non-rigid and
non-periodic motion even in a single k-space dataset
(without repetitive acquisition for multiple cycles,
without gating).
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2467. |
Self-adjusting
multi-channel UWB radar for cardiac MRI
Olaf Kosch1, Steffen Schneider1,
Bernd Ittermann1, and Frank Seifert1
1Physikalisch-Technische Bundesanstalt (PTB),
Berlin, Germany
We have extended our motion detection by contactless
multi-channel UWB radar for cardiac MRI navigator to a
4x8 channel system to make the application more robust.
The new system is insensitive to a not well placed
antenna configuration related to the position of the
monitored person. Additionally a method for rejecting
noisy channels was implemented to avoid average effects.
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2468. |
Prospective motion
correction using NMR probes.
Saikat Sengupta1, John C. Gore1,
and E. Brian Welch1
1Radiology and Radiological Sciences,
Vanderbilt University, Nashville, TN, United States
Motion is one of the primary sources of artifacts in MRI
and improved motion correction is especially useful in
high-resolution imaging. Nuclear magnetic resonance
probes have recently been employed successfully in rigid
body motion correction at 1.5 Tesla. In this work, real
time prospective head motion correction based on proton
NMR probes at ultra high field (7T) is presented.
Simulated motion on a phantom is used for system
validation and testing of real time motion correction
algorithm.
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2469. |
Motion-tracking: Fast
high-resolution 2D motion quantification and depiction of
shivering
Eberhard Eduard Munz1, Andreas Johannes
Hopfgartner1, Sairamesh Raghuraman2,
Titus Lanz3, and Peter Michael Jakob1
1Experimental Physics 5, University of
Würzburg, Würzburg, Germany, 2MRB
Research Centre, Würzburg, Germany, 3Rapid
Biomedical GmbH, Rimpar, Germany
In hand imaging the "superman position" is stressful for
the patient and therfore prone to image artifacts. In
this study we used the method of cross-correlation in
order to detect a contrast agent-filled sphere attached
to the patient's hand. Detecting the marker very
accurately and hence quantificating the amount of motion
caused by three different hand-positions we identified
the least stress-causing position for the patient.
Herefrom it is possible to reduce the patient's
shivering to a minimum and furthermore enhance image
quality in high-field (7T) MR-Imaging.
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|
2470. |
Subject specific
respiratory motion correction accounting for hysteresis
Ian Burger1, Ernesta Meintjes1,
David Firmin2,3, and Jennifer Keegan2,3
1Human Biology, University of Cape Town, Cape
Town, Western Cape, South Africa, 2Imperial
College, London, United Kingdom, 3CMR
Unit, Royal Brompton Hospital Trust, London, United
Kingdom
In this study we investigated a non-rigid subject
specific respiratory motion model in cardiac MRI that
accounts for hysteresis. The model is constructed of an
ellipse superimposed on a straight line. Nine healthy
volunteers participated in a study in which a navigator
sample and a 2D image of the heart were acquired in each
cardiac cycle for 90 cycles. The results show that this
model performed significantly better than a linear
affine model. Further, we have demonstrated that a
pre-scan of about 25 seconds (~25 cardiac cycles) is
sufficient to construct the model.
|
|
2471. |
Motion Correction:
MRI-based ultra-fast high-resolution 3D tracking
Andreas Johannes Hopfgartner1, Eberhard Munz1,
Florian Fidler2, and Peter Michael Jakob1
1Experimental Physics 5, University of
Würzburg, Würzburg, Germany, 2Research
Center Magnetic-Resonance-Bavaria, Würzburg,
Deutschland, Germany
For high-resolution MR imaging a simple, flexible, fast
and robust 3D motion tracking method was searched.
Optical devices applications in motion correction suffer
from the drawback that the devices have to be
synchronized in time and space with the MRT hardware.
The proposed method tracks marker spheres without
additional equipment and uses scanner information only.
Two alternatingly and rapidly measured “2D projection
images” from small objects include the position
information. The method allows a high-resolution
(accuracy of  40µm
and 0.1°)
and ultra-fast (170ms) measurement for 3D motion
correction and can be built in in every sequence as
navigator block.
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|
2472. |
Fast Inter-scan Motion
Detection and Compensation
Tim Nielsen1, Peter Börnert1, and
Julien Sénégas1
1Philips Research, Hamburg, Germany
In a typical MRI exam multiple scans are performed. The
geometry of these scans is planned on a survey. If the
patient moves after the acquisition of the survey, the
scanned location is different from the planned location.
We present a fast method to detect and correct for
motion between individual scans of an exam using sets of
three orthogonal slices with low resolution to determine
and track the head position. This tracking method is a
simple, reliable and efficient approach to cope with
inter-scan motion. It requires no user interaction and
does not interfere with the clinical workflow.
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|
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|
Traditional
Poster Session - Pulse Sequences & Reconstruction B |
|
Intensity/Distortion Correction
Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
|
Exhibition Hall |
16:00 - 18:00 |
|
|
|
2473. |
Estimating Phase Maps from
Partial K-Space Data
Tom Depew1, and Qing-San Xiang1,2
1Physics & Astronomy, University of British
Columbia, Vancouver, BC, Canada, 2Radiology,
University of British Columbia, Vancouver, BC, Canada
Phase can be used to encode information about numerous
MRI properties such as magnetic field strength, motion
or flow, and temperature. Phase maps are typically
obtained by comparing two complex images in which the
relative phase is sensitized to the physical quantity of
interest. In situations where the phase can be assumed
to change smoothly, the two images can be reconstructed
from central k-space data to reduce scan time. Here we
investigate the effect of truncation artifact associated
with this approach and the feasibility of obtaining
phase maps by fitting a convolution kernel to various
partial k-space coverage patterns.
|
|
2474. |
Efficient concomitant
field artifacts reduction using a hybrid space-frequency
domain formulism
Yi-Cheng Hsu1, Panu T. Vesanen2,
Jaakko O. Nieminen2, Koos C. J. Zevenhoven2,
Juhani Dabek2, I-Liang Chern3,
Risto J. Ilmoniemi4, and Fa-Hsuan Lin3,5
1National Taiwan University, Taipei, Taiwan, 2Aalto
University, Finland, 3National
Taiwan University, Taiwan, 4Aalto
University, Taiwan, 5Massachusetts
General Hospital, United States
To mitigate the challenge of reconstructing MRI data
deteriorated by concomitant fields, we develop a hybrid
space-frequency (x-f) domain method to i) accurately
describe the dynamics of spatially encoded magnetization
allowing arbitrary directions of initial magnetization
and phase/frequency encoding magnetic fields, and (ii)
reconstructed images using combined fast Fourier
transform and a linear equation solver. We demonstrate
this method in ultra-low-field MRI reconstruction when
the largest concomitant field is as strong as B0.
|
|
2475. |
Selfcalibrated DCE MRI
using Multi Scale Adaptive Normalized Averaging (MANA)
Thord Andersson1,2, Thobias Romu1,2,
Bengt Norén2,3, Mikael Fredrik Forsgren2,4,
Örjan Smedby2,3, Stergios Kechagias5,6,
Sven Almer6,7, Peter Lundberg2,4,
Magnus Borga1,2, and Olof Dahlqvist Leinhard2,4
1Dept of Biomedical Engineering (IMT),
Linköping University, Linköping, Sweden, 2Center
for Medical Image Science and Visualization (CMIV),
Linköping University, Linköping, Sweden, 3Dept
of Medical and Health Sciences (IMH), Div of
Radiological Sciences, Linköping University, Linköping,
Sweden, 4Dept
of Radiation Physics, Linköping University and Radiation
Physics, UHL County Council of Ostergotland, Linköping,
Sweden, 5Dept
of Medical and Health Sciences (IMH), Div of
Cardiovascular Medicine, Linköping University, Linköping,
Sweden, 6Dept
of Endocrinology and Gastroenterology, UHL County
Council of Ostergotland, Linköping, Sweden, 7Dept
of Clinical and Experimental Medicine (IKE), Div of
Gastroenterology and Hepatology, Linköping University,
Linköping, Sweden
In conventional analysis of DCE MRI time series,
constant sensitivity of the MR-scanner during the
experiment usually is assumed. However, patient movement
and other effects may affect the sensitivity during the
time series. The Multi Scale Adaptive Normalized
Averaging (MANA) method has been proposed to correct
intensity inhomogeneity in fat-water MRI using Dixon
imaging, and to provide reference scaling in DCE MRI
time series. In this work, we validate statistically the
correctness of MANA compared to conventional scaling.
The results show that MANA provides more consistent
intensities and successfully can recreate scaling
information directly from the data.
|
|
2476. |
Guided Multi-channel Blind
Deconvolution Coil Intensity Correction for Improved
Uniformity and Contrast Fidelity
Dominic M Graziani1, Stephen J Garnier2,
Ek T Tan1, and Christopher J Hardy1
1GE Global Research, Niskayuna, NY, United
States, 2GE
Healthcare, Waukesha, WI, United States
We report on an iterative reconstruction technique for
image-based intensity correction of phased-array images
using multi-channel blind deconvolution (MBD) and
homomorphic filtering. This combined method produces
images with better bias field correction and higher
contrast fidelity than either technique on its own. The
algorithm is relatively insensitive with respect to the
choice of adjustable parameters, and reasonably fast,
taking around 2 seconds per slice in Matlab. We
demonstrate the effectiveness of this technique by
correcting spine images acquired with an 8 channel
single-sided array with good resulting uniformity and
contrast.
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|
2477. |
COMPARISON STUDY OF
INTENSITY NON UNIFORMITY CORRECTION METHODS FOR 3DT1 MRI
ACQUISITIONS
Nicolas Vibet1,2, François De Guio2,3,
Aurélien Monnet4, Nadine Girard5,
Stéphane Lehéricy2,6, Sophie Pérusat7,
Carole Dufouil8, Christine Delmaire2,4,
Cyril Poupon2,9, and Marie Chupin1,2
1CRICM, UPMC URMR_S975, INSERM U975, CNRS
UMR7225, ICM, Paris, France, 2CATI,
multicentre neuroimaging platform, Paris, France, 3LNAO,
Neurospin, CEA, Gif-sur-Yvette, France, 4Department
of Neuroradiology, AP–HP, Lille, France, 5Department
of Neuroradiology, Hopital Timone, Marseille, France, 6CRICM
& CENIR, UPMC/CNRS/INSERM/ICM, Paris, France, 7U593,
INSERM, Bordeaux, France, 8U897,
INSERM, Bordeaux, France, 9LRMN,
Neurospin, CEA, Gif-sur-Yvette, France
Intensity non-uniformity is often largely visible in
3DT1 acquistions; it can lead to difficulties in
advanced data analysis. Several methods are available,
from manufacturers or post processing tools, but their
use in multicentre study has yet to be evaluated; we
compared the performances of manufacturers intensity non
uniformity correction tools with two available post
processing methods (BrainVISA and SPM) for three
scanners (Siemens 1,5T and 3T, Philips 3T). This
analysis is based on four quality indices computed on
the image and its itensity histogram. In the framework
of multicentre analyses, post-processing methods appear
to be better adapted and perform satisfactorily.
|
|
2478. |
Correcting geometric
distortions of Echo Planar Imaging using demons and reversed
phase encoding
M. Lyksborg1,2, H. Lundell2, N.
Reislev2, H. R. Siebner2, R.
Larsen1, and T. B. Dyrby2
1Technical University Of Denmark, Kgs. Lyngby,
Denmark, 2Danish
Research Centre for Magnetic Resonance, Hvidovre,
Denmark
Correcting for geometric distortions of Echo Planar
Imaging (EPI) is extremely important for anatomical
fidelity. Based on the acquisition of 2 EPI’s with
reversed gradient polarity, we suggest using an
efficient non parametric image registration method to
estimate the geometric distortion field. We demonstrate
the method on 5 subjects and compare it with a minimally
distorted structural image. The method achieves results
similar to that of the field map and point spread
function method.
|
|
2479. |
Correcting slice
selectivity in hard pulse sequences
David Manuel Grodzki1,2, Peter Jakob1,
and Bjoern Heismann2,3
1EP5, University of Wuerzburg, Wuerzburg,
Bavaria, Germany, 2Magnetic
Resonance, Siemens AG, Erlangen, Germany, 3Friedrich-Alexander-University,
Erlangen, Germany
Many MRI sequences use non-selective hard pulse
excitation in the presence of imaging gradients. In this
work, we investigate possible artefacts due to unwanted
slice-selectivity in hard pulse sequences. A correction
algorithm is proposed that eliminates the influence of
the excitation profile. Phantom as well as in-vivo
measurements prove that enhanced image quality can be
obtained as long as the first minimum of the excitation
profile lies outside the imaged object.
|
|
|
|
|
Traditional
Poster Session - Pulse Sequences & Reconstruction B |
|
|
Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
|
Exhibition Hall |
16:00 - 18:00 |
|
|
|
2480. |
Iterative Decomposition of
Water and Fat with Echo Asymmetric and Least-Squares
Estimation (IDEAL) Compared to T1-weighted Spin Echo in the
Evaluation of Vertebral Body Lesions
Behroze Adi Vachha1, Subhendra Sarkar1,
Robert Greenman1, and David Hackney1
1Radiology, Beth Israel Deaconess Medical
Center, Harvard Medical School, Boston, MA, United
States
We compared the effectiveness of Iterative Decomposition
with Echo Asymmetric and Least-Squares Estimation
(IDEAL) fat-selective images to conventional T1-weighted
spin-echo (SE) images for depiction of vertebral body
lesions with reduced or increased fat content. We
computed signal intensity ratios of lesions to adjacent
vertebrae with both sequences. IDEAL showed
significantly higher contrast between vertebral lesions
and adjacent vertebral bodies than T1 SE images, ratios
were 0.58 (T1 weighted), and 0.25 (IDEAL fat-selective)
for reduced fat lesions and 1.47 (T1 weighted) and 1.83
(IDEAL fat-selective) for increased fat lesions; p<0.05
for both lesion types. IDEAL also displays significantly
higher fat/water contrast, p<0.001.
|
|
2481. |
Joint Inference of Field
Inhomogeneities with Fat Likelihood Estimation from Three
Echoes
Wenmiao Lu1, and Yi Lu2
1Beckman Institute, University of Illinois,
Urbana-Champaign, Illinois, United States, 2Electrical
and Computer Engineering, University of Illinois,
Urbana-Champaign, Illinois, United States
This work presents a joint inference algorithm which
effectively combines the field map smoothness constraint
and the fat likelihood estimated from three echoes. This
technique is potentially useful for motion-sensitive
applications, such as liver fat quantification.
|
|
2482. |
Field Map Error Location
and Correction for Fat/Water Separation Methods
Sreenath Narayan1, Satish Kalhan2,
and David Wilson1
1Department of Biomedical Engineering, Case
Western Reserve University, Cleveland, OH, United
States, 2Department
of Molecular Medicine, Case Western Reserve University,
Cleveland, OH, United States
We have shown that error correction can be used to
reliably and automatically decompose fat and water at
7T, with minimal human interference. When combined with
FLAWLESS, a previously published technique, we were able
to avoid complete swaps of fat and water, while
preventing partial swaps from appearing in 99.7% of our
134 images.
|
|
2483. |
Image-based determination
of the fat signal model for Dixon water and fat imaging
Tze Yee Lim1, and Jingfei Ma1
1University of Texas MD Anderson Cancer
Center, Houston, TX, United States
Accurate modeling of the fat signal is important for
Dixon water and fat imaging. However, many confounding
factors (e.g., pulse sequence, scan parameters) of the
fat signal cannot be accounted for even when the complex
fat spectrum is accurately known. In this work, we
present a method that can extract the amplitude and
phase dependence of the fat signal directly from the
different images by the Dixon acquisition. These results
can then be used for processing data of the same pulse
sequence and similar scan parameters from different
patients.
|
|
2484. |
Fast and Robust Separation
of Multiple Chemical Species from Arbitrary Echo Times with
Complete Immunity to Phase Wrapping
Yun Jiang1, Mark Griswold1,2, and
Jeffrey Tsao3
1Department of Biomedical Engineering, Case
Western Reserve University, Cleveland, Ohio, United
States, 2Department
of Radiology, Case Center for Imaging Research,
University Hospitals of Cleveland and Case Western
Reserve University, Cleveland, Ohio, United States, 3McKinsey
& Company, Boston, Massachusetts, United States
We report a fast and robust method, hierarchical IDEAL,
which has been extended to separate multiple chemical
species from images acquired at three or more arbitrary
echo times. The new method is completely immune to phase
wrapping issues, and the optimized algebraic formulation
allows for high computational efficiency. Representative
results from human ankle and knee images are shown to
demonstrate its performance.
|
|
2485. |
Phase Combination for
Multi-channel RF Coils with a Dual-echo Scan in Water-Fat
Imaging
Zhongxu An1,2, Rui Li1, Haining
Liu1, Chun Yuan1,3, and Hua Guo1
1Center for Biomedical Imaging Research,
Department of Biomedical Engineering, School of
Medicine, Beijing, China, 2Department
of Electronic Engineering, Beihang University, Beijing,
China, 3Department
of Radiology, University of Washington, Seattle, WA,
United States
Owing to the phase offset existing among different
channels, phase images from multi-channel coils are
difficult to combine. In this work, a new Multi-Channel
Phase Combination with In-Out phase time (MCPC-IO) is
proposed and verified by phantom studies. It is also
applied in six-point IDEAL water-fat separation. The
mean value of fat fraction calculated with MCPC-IO is
closer to the true value than with the conventional
method. Phase unwrapping is not needed in MCPC-IO, and
it can also be simply applied to phase combination in
susceptibility weighted imaging.
|
|
2486. |
Multi-channel T2*
IDEAL for Water Fat Separation with Prior Optimized Phase
Haining Liu1, Zhongxu An2, Xinwei
Shi3, Chun Yuan4, and Hua Guo1
1Center for Bio-Medical Imaging Research,
Tsinghua University, Beijing, Beijing, China, 2Beihang
University, Beijing, Beijing, China, 3Tsinghua
University, Beijing, Beijing, China,4Department
of Radiology, University of Washington, Seattle, WA,
United States
Since traditional multicoil water-fat separation methods
process data for each channel individually, they are
computation intensive and have poor noise resistance
performance. This work aims to investigate a new method
which can combine multichannel phase images optimally
before performing the complex-fitting based water-fat
separation. Compared with the traditional method, our
method can not only significantly shorten the
calculation time but also improve the quantification
accuracy and noise resistance. And this method is not
limited by in- or out-phase echo times.
|
|
2487. |
Correction of slice
profile deformations and estimation of optimal flip angles
to enable accurate T1/T2 mapping
using 2D variable flip angle techniques
Matthias Alexander Dieringer1,2, Michael
Deimling1,3, Florian von
Knobelsdorff-Brenkenhoff1,2, Andreas Greiser3,
Jeanette Schulz-Menger1,2, and Thoralf
Niendorf1,2
1Berlin Ultrahigh Field Facility,
Max-Delbrueck Center for Molecular Medicine, Berlin,
Germany, 2Experimental
and Clinical Research Center (ECRC), Charité Campus
Buch, Humboldt-University, Berlin, Germany, 3Siemens
Healthcare, Erlangen, Germany
DESPOT1/2 uses 3D acquisitions for T1/T2 quantification.
For 2D acquisitions, however, short repetition times
evoke T1 and
flip angle dependent saturation phenomena that deform
the slice profile and hence bear the potential to deem T1/T2 quantification
inaccurate. Therefore, this study examines the impact of
slice profile deformations on 2D T1/T2 quantification
using variable flip angles in simulations, phantoms, and
in-vivo in the brain. A correction method to facilitate
accurate quantification of T1/T2 using
2D DESPOT1/2 along with a flip angle optimization
algorithm are presented.
|
|
2488. |
Calalyzing the Refocused
TSE Echo Train Facilitates Phase-Detection for Fat-Water
Separation
Samuel Fielden1, John Mugler, III1,2,
and Craig Meyer1,2
1Biomedical Engineering, University of
Virginia, Charlottesville, Virginia, United States, 2Radiology,
University of Virginia
Catalyzation techniques are common for bSSFP sequences.
Here we apply a linear catalyzation ramp to the
refocused TSE sequence in order to force the phase
behavior of the spins rapidly into a steady state in
order to support phase detection for fat/water
separation based on simple phase detection.
|
|
2489. |
Water Fat Separation with
BLADE Based on Two Points Dixon Technique
Dehe Weng1,2
1Beijing MRI Center for Brain Research,
Institute of Biophysics, Chinese Academy of Sciences,
Beijing, China, 2Siemens
Shenzhen Magnetic Resonance Ltd, Shenzhen, Guangdong,
China
BLADE based on two points Dixon is proposed, two echoes
are acquired to create time dependent phase shifts
caused by water fat chemical shift, they are called
in-phase and out-of-phase images. The in-phase image is
reconstructed with re-gridding, while the out-of-phase
image is reconstructed by using all blades from in-phase
image for phase correction. Sign detection based on
region growing is used to correct the out-of-phase image
before the calculation of water and fat images, making
this method insensitive to inconsistent error or eddy
current.
|
|
2490. |
Making SENSE of Chemical
Shift: Separating Species in Single-Shot EPI using Multiple
Coils
Martin Uecker1, and Michael Lustig1
1Electrical Engineering and Computer Science,
University of California Berkeley, Berkeley, CA, United
States
We present a method for separating chemical shift in
single-shot EPI using multiple coils. Chemical shift
causes severe artifacts in long echo-train EPI. This
artifact is inconsistent with the coil sensitivities.
For example, fat would have shifted sensitivity maps
with respect to water. By finding a solution consistent
with these two sets of maps, separation is achieved.
Results are presented using maps obtained from a
pre-scan showing high quality images without the need of
knowing the field inhomogeneity. In addition, we present
a fully automated joint estimation scheme based
nonlinear inversion that does not require prior
knowledge of the sensitivities.
|
|
2491. |
Simultaneous EPI-based T1,
T1, and T2' mapping
Daniel L Shefchik1, Andrew S Nencka1,
Andrzej Jesmanowicz1, and James S Hyde1
1Biophysics, Medical College of Wisconsin,
Milwaukee, WI, United States
The accelerated gradient-recalled echo, asymmetric
spin-echo pulse sequence was developed to produce
relaxivity maps with the same EPI readouts used in
functional studies. The sequence had the ability to
calculate T1, T2 and T2* voxel-wise relaxivity maps from
a single excitation utilizing echo pairs. These echo
pair calculations led to systematic errors due to low
SNR for T2 and T2* echo pairs and the inaccuracy of the
flip angles. A new non-linear model was developed which
greatly increase the accuracy of the EPI collected
relaxivity maps, while maintaining the ability to
provide precise dynamic time series T2 and T2* maps.
|
|
2492. |
A general analytical
solution for optimized fat-suppression calculation
Caixia Fu1, Stephan Kannengiesser2,
Dominik Nickel2, Xiaodong Zhou1,
Berthold Kiefer2, and Dehe Weng1
1Siemens (Shenzhen) Magnetic Resonance Ltd.,
Shenzhen, Guangdong, China, 2MR
Applications Development, Siemens AG, Healthcare Sector,
Erlangen, Germany
This abstract proposes a general analytical solution for
optimized fat-suppression calculation: Firstly, the
magnetization expressions of fat with spoiled GRE
sequence are derived from Bloch equation. And two
boundary conditions including steady state of fat signal
and optimized fat suppression condition are described.
Secondly, a closed analytical equation for fat
suppression calculation is derived Based on the
magnetization expression of fat and 2 conditions, and
the solution to calculate the flip angle for FatSat and
TI fill time or TR fill time for SPAIR is described.
Finally, In-vivo test result shows that the proposed
solution is working well for both FatSat and SPAIR.
|
|
|
|
|
Traditional
Poster Session - Pulse Sequences & Reconstruction B |
|
|
Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
|
Exhibition Hall |
16:00 - 18:00 |
|
|
|
2493. |
Spin Echo and Adiabatic
Spin Echo Motion Compensated Spiral functional MRI
Priti Balchandani1, John M. Pauly2,
Daniel M. Spielman1, and Gary H. Glover1
1Radiology, Stanford University, Stanford,
California, United States, 2Electrical
Engineering, Stanford Universiy, Stanford, California,
United States
We have developed spin echo and adiabatic spin echo
motion compensated spiral fMRI sequences to isolate the
small blood vessel contribution to the BOLD signal. The
sequences provide improved immunity to B0-inhomogeneity
and motion artifacts. The adiabatic version of the
sequence utilizes matched phase adiabatic SLR pulses to
provide a B1-insensitive spin echo. 3T
phantom and in
vivo functional
scans show more uniform signal-to-fluctuation-noise
ratio and higher resolution functional maps are achieved
by the spin echo sequences when compared to a
conventional gradient echo spiral fMRI sequence.
|
|
2494. |
Further acceleration of
Partial Fourier-FOCUSS using Bunched Phase Encoding
Hisamoto Moriguchi1, Kohki Yoshikawa2,
Morio Shimada2, Shin-ichi Urayama3,
Yutaka Imai1, Manabu Honda4, and
Takashi Hanakawa4
1Radiology, Tokai University, Isehara,
Kanagawa, Japan, 2Radiological
Sciences, Komazawa University, Tokyo, Japan, 3Human
Brain Research Center, Kyoto University, Kyoto, Japan, 4Functional
Brain Research, National Center of Neurology and
Psychiatry, Tokyo, Japan
Bunched Phase Encoding (BPE) has significant potential
for fast data acquisition in MRI. In BPE, k-space data
are acquired along zigzag trajectories to reduce the
scan time. Partial Fourier-FOCUSS (PF-FOCUSS) has been
proposed as a new reconstruction method for PF imaging
in standard Cartesian data acquisition. Images
reconstructed using PF-FOCUSS are generally of high
quality. In this study, BPE acquisition method is taken
advantage of in PF-FOCUSS to further accelerate data
acquisition while quality of the image is maintained.
The newly proposed method is referred to as eBPE-PF-FOCUSSf.
BPE-PF-FOCUSS can usually achieve reduction factor 4
with no significant noise amplification.
|
|
2495. |
FMRI Using 3D PRESTO-CAN -
A Novel Method Based on Golden Angle Hybrid Radial-Cartesian
Sampling of K-Space
Maria Magnusson1,2, Olof Dahlqvist Leinhard2,3,
Helene van Ettinger-Veenstra3,4, and Peter
Lundberg2,3
1Electrical Engineering, Linköping
University, Linköping, Sweden, 2Radiation
Physics, Linköping University, Linköping, Sweden, 3Center
for Medical Image Science and Visualization (CMIV),
Linköping University, Linköping, Sweden, 4Medical
Radiology, Linköping University, Linköping, Sweden
We have shown that it is possible to detect neural
activity using fMRI and PRESTO-CAN, a previously
developed MRI reconstruction method based on golden
angle hybrid radial-Cartesian sampling of k-space. The
neural activity appears to be comparable with what can
be obtained using a 3D PRESTO Cartesian sequence.
However, we have not yet utilized all the facilities of
PRESTO-CAN, such as the hourglass filter. The PRESTO-CAN
sequence investigated here is able cover the whole brain
for fMRI examinations with sufficient temporal
resolution.
|
|
2496. |
Indirect Measurement of
Echo Peak Shift for Half Echo Ultrashort TE (UTE) Imaging
with Radial Sampling
Masahiro Takizawa1, Hikaru Hanada1,
Kuniharu Oka1, and Tetsuhiko Takahashi1
1MRI system division, Hitachi Medical
Corporation, Kashiwa, Chiba, Japan
UTE sequence based on half echo radial sampling is very
sensitive to small k-space trajectory errors. Many kind
of gradient waveform approximation were developed for
correcting these k-space trajectory errors. The
remaining echo peak shift after applying the gradient
waveform approximation causes image degradation. Because
UTE sequence acquires only half the echo signal, it is
difficult to detect echo peak position directly. We
developed indirect echo peak detection algorithm
dedicated for half echo signal by using pre-scan. The
results shows that this indirect method works well and
makes it possible to effectively minimize the error in
the k-space trajectory.
|
|
2497. |
Selective TOF MRA using
Beam Saturation pulse
Takashi Nishihara1, Hiroyuki Itagaki1,
Chikako Moriwake2, David A. Lampman3,
Tetsuhiko Takahashi1, Yosuke Hirata4,
Kohsuke Kudo5, and Makoto Sasaki5
1MRI System Division, Hitachi Medical
Corporation, Kashiwa, Chiba, Japan, 2Marketing
Division, Hitachi Medical Corporation, Tokyo, Japan, 3Development
Center of America, Hitachi Medical Systems America,
Inc., Twinsburg, OH, United States, 4Center
for Radiological Sciences, Iwate Medical University
Hospital, Morioka, Iwate, Japan, 5Division
of Ultrahigh Field MRI, Institute for Biomedical
Sciences, Iwate Medical University, Morioka, Iwate,
Japan
We investigated use of a 2D beam excitation pulse (Beam
Sat pulse) to saturate the ICA, to realize selective TOF
MRA. Beam shape stability was evaluated for B0
inhomogeneity. When B0 inhomogeneity was less than 50Hz,
an expansion of FWHM from specification was less than
10%. The position and direction of the Beam Sat pulse
were evaluated. As the results, one side ICA was
saturated selectively. Saturation effect of signal
intensity in the artery was evaluated. For 7 volunteers,
the signal intensity from ICA to MCA-M4 was saturated.
The Beam Sat pulse is able to saturate the ICA
selectively.
|
|
2498. |
Simultaneously FAT and
WATER suppression by interleaved VAPOR, SPAIR and OVS for 1H
Spectroscopy at 7T
Baolian Yang1
1BU MR, Philips Healthcare, Cleveland, OH,
United States
Water and/or fat suppression is an essential part of
pulse sequence in order to get high quality 1H
spectroscopy of brain. But it is very difficult to get
high water and fat suppression factors in the same time
for 1H spectroscopy using the tradition techniques such
as dual-band or sequential suppression due to
non-uniform B1 field, especially at ultra-high field
(>=7T). In this work, an interleaved VAPOR and SPAIR
sequence is developed to accomplish simultaneously water
and fat suppression with improved suppression factors.
OVS pulses can also be added into the sequence to
further improve water or fat suppression. The sequence
is insensitive to B1 distribution and applicable to both
short echo and long echo spectroscopy sequences.
|
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2499. |
Multiband Velocity EPI
David Feinberg1,2, Liyong Chen1,2,
and An Vu1,2
1Helen Wills Neuroscience Institute,
University of California, Berkeley, CA, United States, 2Advanced
MRI Technologies, Sebastopol, CA, United States
A new velocity imaging pulse sequence is evaluated by
incorporating velocity phase encoding into the multiband
simultaneous multi-slice EPI sequence. Six simultaneous
images at different levels through the brain were
acquired in time series at 100ms TR frame rate to
measure CSF, brain motion and arterial velocities
without cardiac gating and without combining signals
recorded in different cardiac cycles. The technique can
be further extended with greater slice coverage for 3D
spatial maps in each time frame.
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|
2500. |
Very low SAR imaging of
the lower leg using variable angle for uniform signal
excitation (VUSE) and balanced SSFP without RF phase cycling
Subashini Srinivasan1,2, J Paul Finn1,3,
and Daniel B Ennis1,2
1Department of Radiological Sciences,
University of California, Los Angeles, California,
United States, 2Biomedical
Engineering Interdepartmental Program, University of
California, Los Angeles, California, United States, 3Biomedical
Physics Interdepartmental Program, University of
California, Los Angeles, California, United States
Variable flip angle for uniform excitation (VUSE) has
been used recently for bSSFP with RF phase alternation
to generate constant transverse magnetization during
transient imaging. Here, we present the calculation of
the flip angle train and simulation for bSSFP without RF
phase cycling (VUSEnoalt). The simulation results show
that the required flip angle train is very low in
magnitude with high off-resonance sensitivity. 2D
multi-slice interleaved, segmented images of the lower
leg were acquired and the SNR of different tissues were
compared with bSSFP and VUSEbSSFP. The results show that
the low SAR property of VUSEnoalt may be useful
especially when scanning patients with implanted devices
or for non-contrast arterial angiography due to the good
artery-vein contrast.
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2501. |
Low power adiabatic T1rho
imaging
Ovidiu Cristian Andronesi 1, Himanshu Bhat 2,
Helena Leitao 3, Alexander Guimaraes 4,
and Peter Caravan 5
1Martinos Biomedical Imaging Center, MGH,
Charlestwon, MA, United States, 2Martinos
Center, Siemens Medical Solutions USA, Charlestwon, MA,
United States, 3Coimbra
University, Portugal, 4Radiology,
MGH, 5MGH |
|
2502. |
Midbrain nuclei
visualization improved by susceptibility-enhanced 3D
inversed Double Echo Steady State (iDESS) imaging
Ming-Long Wu1,2, Hing-Chiu Chang3,4,
Tzu-Cheng Chao1,2, Pei-Hsin Wu5,
and Nan-Kuei Chen6
1Institute of Medical Informatics, National
Cheng Kung University, Tainan, Taiwan, 2Department
of Computer Science and Information Engineering,
National Cheng Kung University, Tainan, Taiwan, 3Global
Applied Science Laboratory, GE Healthcare, Taipei,
Taiwan, 4Institute
of Biomedical Electronics and Bioinformatics, National
Taiwan University, Taipei, Taiwan, 5Department
of Electrical Engineering, National Taiwan University,
Taipei, Taiwan, 6Brain
Imaging and Analysis Center, Duke University, Durham,
North Carolina, United States
Imaging anatomical structures in human midbrain is
important for investigating Parkinson¡¦s Disease (PD).
Conventionally, T2* gradient echo method with long echo
time (> 20ms) can be used to visualize small nuclei in
midbrain. However, clear visualization of midbrain
nuclei remains challenging using SPGR due to limited
contrast and suboptimal efficiency. In this study, we
show that susceptibility-enhanced 3D inversed Double
Echo Steady State (iDESS) can be used to efficiently
obtain high contrast images for visualization of
midbrain nuclei. Results from 1.5 Tesla MRI also
demonstrate that iDESS has high potential to improve
Deep Brain Stimulation (DBS) guidance in PD.
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|
2503. |
Highly Accelerated
Single-Slab 3D GRASE with Phase-Independent Image
Reconstruction
Hahnsung Kim1, Dong-Hyun Kim1, and
Jaeseok Park2
1Electrical and Electronic Engineering,
Yonsei University, Seoul, Korea, 2Brain
and Cognitive Engineering, Korea University, Seoul,
Korea
Single-slab 3D turbo/fast spin echo imaging with short
non-selective pulses and variable flip angles in the
refocusing pulse train has been recently introduced to
increase echo train length and thus enhance imaging
efficiency. It has been efforts to further prolong echo
train length for high-resolution 3D brain imaging.
However, this approach is highly energy-intensive and
drops out SNR and CNR within permissible ranges of SAR.
To enhance imaging efficiency while retaining SAR limit
at high field, in this work we develop highly efficient
single-slab 3D GRASE imaging, incorporating: 1) multiple
echo planar imaging readouts into a framework of
turbo/fast SE imaging and thereby reducing the number of
refocusing pulses and 2) parallel imaging assisted
phase-independent image reconstruction to remove phase
discontinuity related artifacts.
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Traditional
Poster Session - Pulse Sequences & Reconstruction B |
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|
Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
|
Exhibition Hall |
16:00 - 18:00 |
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2504. |
Fast Simultaneous B0/B1 Mapping
by Bloch-Siegert Shift with Improved Gradient Scheme and
Pulse Design
Qi Duan1, Peter van Gelderen1, and
Jeff H. Duyn1
1Advanced MRI section, LFMI, NINDS, National
Institutes of Health, Bethesda, MD, United States
This abstract investigates fast simultaneous B0/B1 mapping
by Bloch-Siegert shift. Based on investigation of the
source of the SAR limitation, it proposes several
modifications from the original scheme to reduce such
limitation while maintaining same sensitivity to the B1 field.
Simultaneous B0 mapping
is added into the sequence to further improve the
accuracy by compensating the increased B0 sensitivity
due to reduced frequency offset. The newly proposed
scheme is compared to the original scheme both via
simulation and in vivo demonstration.
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|
2505. |
Simultaneous B1+
and B0 mapping
using Dual-Echo Bloch-Siegert (DEBS) sequence.
Paulo Loureiro de Sousa1,2, Alexandre Vignaud3,
and Jean-Paul Armspach1
1Université de Strasbourg, CNRS, Laboratoire
d'Imagerie et de Neurosciences Cognitives (LINC),
Strasbourg, France, 2Institut
de Myologie, Paris, France, 3Siemens
Healthcare, Saint Denis, France
There is increasing interest in using quantitative
magnetization transfer imaging (qMTI) for investigation
of the myelin integrity. Because qMTI results obtained
from pulsed saturation experiments rely on an accurate
knowledge of the power and offset frequency of RF
saturation, inhomogeneities of the transmit (B1+) and/or
the static field (B0), such as those observed in high
field NMR imaging (≥ 3T), will lead to systematic errors
in qMTI indices. In this work we investigate the
feasibility of fast and simultaneous assessment of B0
and B1+ using a dual-echo Bloch-Siegert sequence (DEBS).
In vivo results of field mapping using DEBS are
presented.
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|
2506. |
Accurate B0 mapping with
an adaptive algorithm integrating KESA, PRELUDE, and
time-domain phase unwrapping
Pei-Hsin Wu1, Hsiao-Wen Chung1,2,
and Nan-Kuei Chen3
1Department of Electrical Engineering,
National Taiwan University, Taipei, Taiwan, 2Institute
of Biomedical Electronics and Bioinformatics, Taipei,
Taiwan, 3Brain
Imaging and Analysis Center, Duke University Medical
Center, Durham, NC, United States
The accuracy of B0 mapping in dual-TE data is dominated
by the decision of the phase accumulation time (ΔTE).
Specifically, the pronounced phase wrap-around effects
and the susceptibility-induced intravoxel signal loss
lead to degradation of B0 map with large ΔTE. In this
study, an improved approach is proposed for high
quantitative accuracy B0 mapping, where the phase
unwrapping for phase accumulation map is accomplished by
exploiting information from k-space energy spectrum
analysis (KESA) accompanying with the appropriate use of
the mask in the initial KESA estimation.
|
|
2507. |
Shim component analysis
for dynamic shimming of the breast
Eunhae Joe1, Yoonho Nam1, Min-Oh
Kim1, and Dong-Hyun Kim1
1Electrical and Electronic Engineering,
Yonsei University, Seoul, Korea
Respiratory motion can induce fluctuation of magnetic
field causing artifacts in magnetic resonance
spectroscopy (MRS) and proton resonance frequency shift
(PRFS) MR thermometry in the breast. It has been
reported that the magnitude of respiratory-induced B0
shift in the breast is ten times greater than in the
brain and varies in location. It is therefore important
to determine the regional and temporal variation of B0
fluctuation during respiration. The aim of this study is
to estimate and analyze the respiratory-induced temporal
B0 fluctuation in different location of breast in a
three dimensional volume.
|
|
2508. |
Robust Field Map
Estimation using VARPRO and Multi-labeling Continuous
Max-Flow
Abraam S. Soliman1,2, Jing Yuan2,
Karl Vigen3, James A. White2,4,
Terry M. Peters1,2, and Charles A. McKenzie1,5
1Biomedical Engineering, University of
Western Ontario, London, Ontario, Canada, 2Imaging
Research Laboratories, Robarts Research Institute,
University of Western Ontario, London, Ontario, Canada, 3Department
of Radiology, University of Wisconsin-Madison, Madison,
WI, United States, 4Division
of Cardiology, Department of Medicine, University of
Western Ontario, London, Ontario, Canada, 5Medical
Biophysics, University of Western Ontario, London,
Ontario, Canada
Field map estimation has been the primary obstacle for
obtaining robust water/fat separation. A novel two-stage
approach is proposed to estimate the field
inhomogeneities. The first stage applies a convex
optimization based algorithm called Continuous Max-Flow
that can reliably achieve a global minimum solution. The
output is used in the second stage to initialize the
well-known IDEAL method to estimate the field map, and
hence, water and fat components. Our approach was tested
on cardiac images of normal subjects, and has shown to
be faster and more robust that existing field map
estimation methods.
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|
2509. |
Analytical examination on
asymmetric distributions of transmission and reception RF
fields by a quadrature coil at high magnetic field
Hidehiro Watanabe1
1Center for Environmental Measurement and
Analysis, National Institute for Environmental Studies,
Tsukuba, Ibaraki, Japan
Maps of the transmission field B1t+ and
the reception filed B1r- by
a quadrature coil differ and show mirror symmetry in
human brain at high field. This is similar to a feature
in a linear coil. We analytically examined the source of
this mirror symmetry in a quadrature coil. We found that
B1t+ and
B1r- differ
in the sign of the sinusoidal phase difference. This
relationship is similar to that in a linear coil. We
also examined maps of magnitude and phase components in
the laboratory frame computed from B1t+ and
B1r- maps
of human brains at 4.7 T.
|
|
2510. |
Experimental Validation of
FDTD Magnetic Field Modeling in the Human Head at 7T
Priscilla Chan1, Mohammad Mehdi Khalighi2,
and Brian K Rutt3
1Electrical Engineering Department, Stanford
University, Stanford, California, United States, 2Global
Applied Science Lab, GE Healthcare, Menlo Park,
California, United States,3Stanford
University, Stanford, California, United States
The trend toward higher performance computing means that
numerical EM modeling of coil/patient interactions is
becoming much more practical and useful, especially for
high field. Using realistic body models of the Virtual
Family, provided by IT’IS Foundation, the magnetic and
electric fields induced by a quadrature birdcage head
coil were simulated using the commercial FDTD package
SEMCAD X throughout the human head at 7T. B1+ fields
created by driving the coil in single-channel or
quadrature modes were compared to experimental
measurements. The close match between these B1+ field
distributions provides strong evidence of the accuracy
of these simulation tools.
|
|
2511. |
Experimental demonstration
of the proportionality of RF reception field to B1-* in
a complex vector space
Hidehiro Watanabe1
1Center for Environmental Measurement and
Analysis, National Institute for Environmental Studies,
Tsukuba, Ibaraki, Japan
The proportionality of the RF reception field to B1-* was
demonstrated straightforwardly in the NMR experiments at
4.7 T. Maps of the reception field and B1- of
a saline phantom were examined in magnitude and phase.
After the reception field map was measured, the RF coil
with the sample was rotated 180 degrees around the
vertical axis and we measured the transmission field
map, which corresponds to B1- in
the original configuration. We also examined phases of
the reception field maps in the original and inverted
configurations. From these results we conclude the
proportionality of the reception field to B1-*.
|
|
2512. |
Regularized Estimation of
Magnitude and Phase of Multiple-Coil B1 Field via Bloch-Siegert
B1 Mapping
Feng Zhao1, Jeffrey A. Fessler2,
Jon-Fredrik Nielsen1, Daehyun Yoon2,
and Douglas C. Noll1
1Biomedical Engineering, University of
Michigan, Ann Arbor, MI, United States, 2Electrical
Engineering, University of Michigan, Ann Arbor, MI,
United States
Bloch-Siegert (BS) B1 mapping is a promising method for
multi-coil B1 mapping, but it may produce B1 maps with
low SNR in low magnitude regions. Furthermore,
estimation of relative B1 phase maps of multi-coil
systems needs another set of scans. In this work, we
propose a regularized method to jointly estimate the
magnitude and (relative) phase of multi-coil B1 maps
from BS B1 mapping data without using additional scans
for the phase estimation. By utilizing the prior
knowledge of B1 maps, the regularization terms for
magnitude and phase can help improve quality of the B1
maps in low magnitude regions.
|
|
2513. |
Practical SAR Constraints
of the Bloch-Siegert B1 Mapping Method at 3T
Daniel J. Park1, Ahsan Javed1,
Neal K. Bangerter1,2, Joshua Kaggie3,
and Glen R. Morrell2
1Department of Electrical and Computer
Engineering, Brigham Young University, Provo, UT, United
States, 2Department
of Radiology, University of Utah, Salt Lake City, UT,
United States, 3Department
of Physics, University of Utah, Salt Lake City, UT,
United States
The recently-introduced Bloch-Siegert shift (BSS) method
of B1 mapping has several advantages over existing B1
mapping methods. However, a major limitation of the BSS
method is the high specific absorption rate (SAR) caused
by the BSS pulse. The BSS pulse generates phase which is
proportional to B12, and the accuracy of the
method increases with increasing amplitude of the BSS
pulse. Since SAR of this pulse is proportional to B12,
SAR constraints place limits on the performance of the
BSS method. This study investigates the tradeoff between
SAR limits and BSS pulse area.
|
|
|
|
|
Traditional
Poster Session - Pulse Sequences & Reconstruction B |
|
|
Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
|
Exhibition Hall |
16:00 - 18:00 |
|
|
|
2514. |
Assessment of stiffness
changes in the ex vivo porcine aortic wall using magnetic
resonance elastography
Lei Xu1,2, Jun Chen1, Meng Yin1,
Kevin J Glaser1, Qingshan Chen3,
David A Woodrum1, and Richard L Ehman1
1Radiology Department, Mayo Clinic,
Rochester, MN, United States, 2Radiology
Department, Beijing Anzhen Hospital, Capital Medical
University, Beijing, China, 3Orthopedics
Biomechanics Lab, Mayo Clinic
MRE is a noninvasive phase-contrast technique for
estimating the mechanical properties of tissues. In this
study, we hypothesize that changes in arterial wall
stiffness, experimentally induced by formalin fixation,
can be measured using MRE in ex vivo porcine aortas. In
agreement with our hypothesis, the significant stiffness
increase after sample fixation were clearly demonstrated
by MRE and confirmed by mechanical testing. The results
indicate that MRE can be used to examine the stiffness
changes of the aorta. This study has provided evidence
of the effectiveness of using MRE to directly assess the
stiffness change in aortic wall.
|
|
2515. |
Rayleigh Damped based
Brain Magnetic Resonance Elastography
Andrii Petrov1, Elijah E. W. Van Houten2,
Matthew D. J. McGarry3, Peter Latta4,
and Marco Gruwel4
1Centre for Bioengineering, University of
Canterbury, Christchurch, New Zealand, 2Mechanical
Engineering, University of Canterbury, Christchurch, New
Zealand, 3Thayer
School of Engineering, Dartmouth College, Hanover, NH,
United States, 4Institute
for Biodiagnostics, National Research Council of Canada,
Winnipeg, Canada
This research study focuses on application of the
subzone based Magnetic Resonance Elastography (MRE)
using Rayleigh damped (RD) material model to quantify
shear stiffness, damping behavior and elastic energy
attenuation mechanism of the intracranial tissue in the
in vivo healthy brain. The octahedral shear strain (OSS)
SNR calculation confirmed significant attenuation of the
shear strain waves in the deeper brain region. The
measurement of brain viscoelastic properties revealed
that ventricles exhibits much lower elasticity (0.8 kPa)
than the surrounding white and gray matter (2.6 kPa). We
conclude that RD MRE show promise for potential in vivo
determination of different brain tissue types, and the
possibility of providing additional diagnostic tools.
|
|
2516. |
Repeatability of healthy
subjects using intrinsically-activated MR elastography
Adam J Pattison1, Matthew DJ McGarry1,
John B Weaver1,2, and Keith D Paulsen1,3
1Thayer School of Engineering, Dartmouth
College, Hanover, NH, United States, 2Radiology,
Dartmouth-Hitchcock Medical Center, Lebanon, NH, United
States, 3Norris
Cotton Cancer Center, Lebanon, NH, United States
Intrinsically-activated MR elastography has been shown
to give reasonable results for brain tissue and detect
differences between normal and hydrocephalic patients.
However, natural changes in metabolism and blood
pressure over time can change the mechanical property
signature of a healthy subject. The aim here is to see
if intrinsic activation is sensitive to changes in a
healthy subject over time and, also, sensitive to
changes amongst a healthy population. Results indicate
that this technique detects a slightly larger mechanical
property variation over time and has a much smaller
variation for a single subject than among a group of
healthy subjects.
|
|
2517. |
High-Resolution Multi-Shot
MR Elastography of the Brain with Correction for
Motion-Induced Phase-Errors
Curtis L. Johnson1,2, Matthew D.J. McGarry3,
Armen A. Gharibans1, John B. Weaver4,
Keith D. Paulsen3,4, Bradley P. Sutton2,5,
and John G. Georgiadis1,2
1Mechanical Science and Engineering,
University of Illinois at Urbana-Champaign, Urbana, IL,
United States, 2Beckman
Institute for Advanced Science and Technology,
University of Illinois at Urbana-Champaign, Urbana, IL,
United States, 3Thayer
School of Engineering, Dartmouth College, Hanover, NH,
United States, 4Radiology,
Dartmouth-Hitchcock Medical Center, Lebanon, NH, United
States, 5Bioengineering,
University of Illinois at Urbana-Champaign, Urbana, IL,
United States
Recently, MR Elastography (MRE) sequences using
multi-shot readouts have been used for higher resolution
acquisitions. However, multi-shot MRE is prone to
significant phase errors between shots due to
inconsistencies in applied motion, resulting in phase
cancellation and signal loss. In this work, a
multi-shot, variable-density spiral sequence is used,
which allows for phase offsets to be estimated for each
shot and registered across shots. Results are presented
which demonstrate the improvement in image quality,
octahedral shear strain-based SNR, and estimated shear
modulus estimates. We present 2mm isotropic
high-resolution brain MRE data with mechanical estimates
obtained with the iterative NLI algorithm.
|
|
2518. |
Brain MR Elastography
using Optimized Mechanical Vibration of the Patient Table
Mikio Suga1,2, Takayuki Obata2,
Hajime Ikeda1, Shinya Ozawa1,
Atsuhisa Koyama1, Tetsuya Wakayama3,
and Riwa Kishimoto2
1Chiba University, Chiba, Chiba, Japan, 2National
Institute of Radiological Sciences, Chiba, Japan, 3GE
Healthcare, Tokyo, Japan
According to a previous study, the vibrations of the
patient table that result from the impulse of an imaging
gradient lobe could be used as a mechanical driving
mechanism for MR elastography (MRE). However, the
vibration frequency must be optimized so that high
spatial resolution and accurate storage-modulus maps (elastogram)
can be obtained. In this study, we add sinusoidally
switching gradients before a conventional MRE pulse
sequence and measure the amplitude of the patient table
as it vibrates during acquisition. To evaluate the
elasticity of the brain using the specific mechanical
resonance frequencies of the patient table,
heterogeneous phantom and in-vivo brain experiments are
performed. The results suggest that the proposed method
will enable accurate measurement of the brain
elasticity.
|
|
2519. |
Analysis of Viscoelastic
and Poroelastic Behavior in MR elastography
Matthew Mcgarry1, Adam Pattison1,
Elijah van Houten2, Curtis Johnson3,
Bradley Sutton3, John Georgiadis3,
John Weaver4, and Keith Paulsen1,4
1Thayer School of Engineering, Dartmouth
College, Hanover, NH, United States, 2Université
de Sherbrooke, Sherbrooke, QC, Canada, 3University
of Illinois at Urbana-Champaign, Urbana, IL, United
States, 4Dartmouth-Hitchcock
Medical Center, Lebanon, NH, United States
The applicability of using viscoelastic and poroelastic
material models as a basis for MR elastography (MRE)
reconstruction algorithms is investigated for two
variants of in vivo brain MRE: Standard external
actuation, where motion is provided at ~50Hz by an
external source, and intrinsic actuation, where motion
from the natural pulsatility of the brain due to the
cardiac pressure cycle is measured and used to calculate
the stiffness distribution. Numerical experiments using
viscoelastic and poroelastic finite element models offer
an explanation for the observed performance of MRE using
each of the two material models for each actuation type.
|
|
2520. |
Multi-Resolution
Reconstruction of Mechanical Properties using Non-Linear
Inversion MR Elastography.
Matthew Mcgarry1, Elijah van Houten2,
Curtis Johnson3, Bradley P Sutton3,
John G Georgiadis3, John Weaver4,
and Keith Paulsen1,4
1Thayer School of Engineering, Dartmouth
College, Hanover, NH, United States, 2Université
de Sherbrooke, Sherbrooke, QC, Canada, 3University
of Illinois at Urbana-Champaign, Urbana, IL, United
States, 4Dartmouth-Hitchcock
Medical Center, Lebanon, NH, United States
MR elastography has proven useful for diagnosing various
diseases (such as liver fibrosis), through quantitative
images of the storage modulus. Images of alternative
parameters such as the viscoelastic loss modulus or
level of anisotropy are also available; however, their
utility is hampered by higher image noise levels. An
important factor determining noise in an MRE parameter
image is the sensitivity of the displacements to changes
in the parameter value. Low sensitivity will lead to
more image noise. This work investigates using different
resolutions for each reconstructed parameter type to
improve reconstructions of low sensitivity parameters.
|
|
2521. |
3D MR Elastography of
in-vivo prostate cancer and correlation with histology:
preliminary results
Ramin Sahebjavaher1,2, Philippe Garteiser2,
Ralph Sinkus2, Louis O. Gagnon3,
Ali Baghani1, Silvia Chang3, Simon
Chatelin2, Edward C. Jones4, Chris
Nguan3, Larry Goldenberg3, Piortr
Kozlowski5,6, Mehdi Moradi7, and
Septimiu Salcudean1
1Electrical and Computer Engineering,
University of British Columbia, Vancouver, BC, Canada, 2Hôpital
Beaujon, Centre de Recherche Biomédicale Bichat Beaujon
(CRB3), Paris, France, 3Department
of Urologic Sciences, University of British Columbia,
Vancouver, BC, Canada, 4Department
of Pathology & Laboratory Medicine, University of
British Columbia, Vancouver, BC, Canada, 5Faculty
of Medicine, University of British Columbia, Vancouver,
British Columbia, Canada, 6The
Prostate Centre, Vancouver General Hospital, Vancouver,
British Columbia, Canada, 7Department
of Radiology, Harvard Medical School, Cambridge, MA,
United States
We present our first in-vivo prostate cancer case using
the trans-perineal MR elastography (MRE) method. An
improved rapid imaging sequence is used to acquire waves
in 3D in the entire prostate gland. The mechanical waves
efficiently transferred to the entire prostate via the
perineum at 70Hz. The results show that the tumours are
clearly distinguishable in the viscoelastic maps and
that they correlate closely with histopathology. To the
best of our knowledge, this is the first in-vivo
prostate cancer MRE study where the viscoelastic maps
are compared to whole-mount histopathology. These
results show the potential for MRE to improve staging of
prostate cancer tumours.
|
|
2522. |
MR Elastography of Hepatic
Fibrosis: Elastogram Analysis Strategies
David John Lomas1, Edmund Godfrey1,
Andrew Patterson1, Richard Black1,
Susan Davies2, Ilse Joubert1,
Ashley Shaw1, Anant Krishnan1,
Michael Allison3, Graeme Alexander3,
Andrew Priest1, and Martin Graves1
1Radiology, Addenbrooke's Hospital &
University of Cambridge, Cambridge, Cambridge, United
Kingdom, 2Pathology,
Addenbrooke's Hospital & University of Cambridge,
Cambridge, Cambridge, United Kingdom, 3Hepatology,
Addenbrooke's Hospital & University of Cambridge,
Cambridge, Cambridge, United Kingdom
MR elastography is a promising new biomarker for
quantifying liver fibrosis. This work investigates
several ROI placement strategies for the analysis of MRE
elastogram data, including a wave detection confidence
method, and whether they improve correlation of the
stiffness estimates with established histopathological
grading schema and semiautomated collagen analysis with
Sirius Red staining. These data indicate that using more
sophisticated analysis strategies based on mean
stiffness region of interest values makes no discernible
difference to the correlation with liver biopsy grading.
|
|
2523. |
Effect of stretching and
compression on the dynamic shear modulus using MRE
Remy Blanchard1, Yogesh K. Mariappan2,
Richard L. Ehman2, Denis Grenier1,
Elisabeth Brusseau1, and Olivier Basset1
1Université de Lyon, CREATIS ; CNRS UMR5220 ;
Inserm U1044 ; INSA-Lyon ; Université Lyon 1, Lyon,
France, 2Department
of Radiology, Mayo Clinic, Rochester, Minnesota, United
States
The goal of this study was to analyze the effect of
controlled compression and tension on the dynamic shear
modulus for the two directions of wave propagation
orthogonal to the particle motion. These mediums were a
100% PVC phantom and an ex vivo specimen of bovine
liver. For both the phantom and the specimen, the
measured shear modulus in both directions increases with
the absolute value of the axial strain under both
compression and tension. This data provide motivation to
further investigate the effects of pre-strain and their
clinical utility to improve the information obtained
from MRE.
|
|
2524. |
MR Elastography with
Improved Coverage Using 3D Gradient-Echo Based EPI
WeiRui Cai1,2, WenHui Huang1, Hui
Wang2, Chao Zou1, ChengZhi Zeng1,
LiJuan Zhang1, HaiRong Zheng1, and
Yiu-Cho Chung1
1Paul C. Lauterbur Research Center for
Biomedical Imaging, Shenzhen Institutes of Advanced
Technology, shenzhen, guangdong, China, 2College
of Electrical and Information Engineering, Hunan
University, Changsha, Hunan, China
MRE is useful in the diagnosis of various diseases such
as liver cirrhosis. Multiple breathholds are needed for
coverage when 2D gradient echoes are clinically used.
EPI techniques previously proposed shorten acquisition
time but reduce image SNR. Here, we propose 3D gradient
echo based EPI for speed and coverage improvement and
compared it with 2D gradient echo MRE sequence. Using
the same scan time, we found that, the 3D technique
gives slightly higher SNR than the 2D technique; it
covers 6 slices instead of one; and there was no obvious
difference between the stiffness maps from the two
methods.
|
|
2525. |
MR elastography of the
prostate using an endorectal coil for actuation: feasibility
in a phantom and porcine prostate
Gregor Thörmer1, Martin Reiss-Zimmermann1,
Josephin Otto1, Nikita Garnov1,
Michael Moche1, Thomas Kahn1, and
Harald Busse1
1Dept. of Diagnostic and Interventional
Radiology, Leipzig University Hospital, Leipzig, Saxony,
Germany
MRE is an emerging technique that measures the
propagation of mechanical waves to noninvasively
determine the viscoelastic tissue properties. As such,
it provides complimentary information to common
morphological and functional MRI data, has already been
evaluated in the breast and liver, and holds promise to
improve prostate diagnostics as well. Previous prostate
MRE work was partially limited by a suboptimal coupling
of the mechanical waves into the prostate gland. This
work describes a new concept for endorectal MRE at 3T
and presents preliminary results in a phantom and a
porcine prostate.
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2526. |
Design and Fabrication of
a Driver for MR Elastography of the Head and Neck: Initial
Results
David K.W. Yeung1, Kunwar Bhatia2,
Yolanda Lee1, Ann D King2, Ralph
Sinkus3, and Anil T Ahuja2
1Imaging and Interventional Radiology, Prince
of Wales Hospital, Shatin, HKSAR, Hong Kong, 2Imaging
and Interventional Radiology, The Chinese University of
Hong Kong, Shatin, HKSAR, Hong Kong, 3Department
of Radiology and IPMA, Beaujon University Hospital,
Clichy, France
MR elastography is a technique that allows the
assessment of mechanical properties of tissues that may
be affected by disease processes. We designed and tested
a new driver to allow MRE to be performed in the head
and neck using a commercially available transducer,
headrest moulds and piston extensions. This new driver
design was simple to implement and comfortable to use.
Our initial results showed that the performance of the
driver was satisfactory and provided reproducible
results for the normal parotid glands. This simple
driver may allow a more widespread application of this
technique to study head and neck pathologies.
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2527. |
Finite Element Simulations
of acoustic radiation contrast in magnetic resonance using
open source software
Anna-Lisa Kofahl1, Sebastian Theilenberg1,
Deniz Ulucay1, Judith Wild1,
Saskia Paul1, Karl Maier1, and
Carsten Urbach1
1HISKP, University of Bonn, Bonn, NRW,
Germany
Investigating the displacement caused by the ARF via MR
phase images offers a new access to the viscoelastic
properties of tissue and has been successfully tested on
phantoms. For a better understanding of the measurements
finite element (FE) simulations have been developed with
special regard to the influence of boundary conditions.
These show an immense influence on the simulation and
the measurements and have to be considered when carrying
out more quantitative investigations. The open source FE
software that is used performs as satisfactorily as
commercial software.
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2528. |
Measured elasticity and
its frequency dependence are sensitive to tissue
microarchitecture in MR Elastography
Simon CHATELIN1, Simon LAMBERT1,
Lauriane JUGE1, Xing CAI2, Sven
Peter NASHOLM2, Valérie VILGRAIN1,
Bernard E Van BEERS1, Xavier MAITRE3,
Lynne E BILSTON4, Bojan GUZINA5,
Sverre HOLM2, and Ralph SINKUS1
1U773-CRB3, INSERM, Paris, France, 2Dept.
of Informatics, University of Oslo, Oslo, Norway, 3UMR
8081-CNRS, Université Paris-Sud, Orsay, France, 4Neuroscience
Research Australia, University of New South Wales, New
South Wales, Australia, 5Dept.
of Civil Engineering, University of Minnesota,
Minneapolis, MN, United States
Understanding the effects of micro-obstacles on wave
propagation is an essential part when trying to extract
micro-structural information from MR-Elastography (MRE)
data from tissue abnormalities such as small metastases
or neovascularization. To date, the effects of wave
scattering on mechanical properties measurements remain
poorly understood. Nevertheless, scattering plays a
major role in linking the architectural properties of a
biological tissue to its mechanical properties measured
by MRE. In this study, the influence of microparticle
size distribution on wave scattering frequency
dependence is investigated from a theoretical and
numerical approach. This study shows for the first time
the feasibility of linking size distribution and
stiffness of micro-particles to the macroscopically
observed elasticity.
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Traditional
Poster Session - Pulse Sequences & Reconstruction B |
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Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
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Exhibition Hall |
16:00 - 18:00 |
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2529. |
High Resolution EPR
Imaging and T2-based Oximetry Using a Combination
of Spin-Echo and Single Point Imaging
Sankaran Subramanian1, Nallathamby
Devasahayam1, Shingo Matsumoto1,
and Cherukuri M Krishna1
1National Cancer Institute, National
Institutes of Health, Bethesda, Maryland, United States
Time-domain Electron Spin Resonance Imaging at RF
frequency (300 MHz) has been developed for mapping
oxygen distribution in mouse models of tumor. Oximetry
is based on the relaxivity of in vivo pO2 on trityl
radicals infused intravenously into the animals. A
combination of spin echo and single point
(constant-time) imaging (SPI) leads to highly resolved
images with T2-weighting and generates quantitaive
sptailly resolved oxygen ditribution maps.
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2530. |
Fast Gated EPR Imaging of
the Beating Heart: Spatiotemporally-Resolved 3D Imaging of
Free Radical Distribution during the Cardiac Cycle
Zhiyu Chen1, Levy A. Reyes1, David
H. Johnson1, Murugesan Velayutham1,
Changjun Yang1, Alexandre Samouilov1,
and Jay L. Zweier1
1Davis Heart and Lung Research Institute,
Ohio State University Medical Center, Columbus, OH,
United States
In vivo or ex vivo electron paramagnetic resonance
imaging (EPRI) is a powerful technique for determining
the spatial distribution of free radicals and other
paramagnetic species in living organs and tissues.
However, applications of EPRI have been limited by long
projection acquisition times and the consequent fact
that rapid gated EPRI was not possible. Hence in vivo
EPRI typically provided only time-averaged information.
In order to achieve direct gated EPRI, a fast EPR
acquisition scheme was developed to decrease EPR
projection acquisition time down to 10 – 20 ms, along
with corresponding software and instrumentation to
achieve fast gated EPRI of the beating heart with
submillimeter spatial resolution in as little as 2 to 3
minutes. Reconstructed images display the temporal and
spatial variations of the free radical distribution,
anatomical structure, and contractile function of a rat
heart during the cardiac cycle.
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2531. |
Temporal Tomographic
Imaging By Greedy Feteke and Golden Means Sampling
David H Johnson1, Zhiyu Chen1,
Rizwan Ahmad1, Alexandre Samouilov1,
and Jay L Zweier1
1Davis Heart and Lung Research Institute,
Ohio State University, Columbus, OH, United States
A new sampling strategy is proposed and evaluated for
tomographic imaging when temporal information is
critical. Typical Electron Paramagnetic Resonance
Imaging (EPRI) sampling strategies assume a static
object and require a priori knowledge about its spatial
distribution to produce reconstructions with few streak
artifacts and accurate intensities. The new sampling
strategy, Greedy Feteke (GF), was compared to a sampling
strategy from the MRI projection acquisition literature,
Golden Means (GM). A dynamic "washout" phantom was
imaged by EPRI using both GF and GM, and GF was found to
have superior temporal resolution to GM. The extension
to 4D spectral-spatial EPRI is straightforward and
compelling for GF sampling, and we anticipate a
significant improvement in temporal cardiac EPRI.
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Traditional
Poster Session - Pulse Sequences & Reconstruction B |
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Electromagnetic Tissue Property Mapping
Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
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Exhibition Hall |
16:00 - 18:00 |
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2532. |
Breast Permittivity
Imaging
Selaka Bandara Bulumulla1, and Ileana Hancu1
1GE Global Research, Niskayuna, New York,
United States
Malignant breast tissue has been found to have higher
permittivity and conductivity relative to healthy tissue
ex-vivo, generating interest in non-invasive methods to
image breast tissue electrical properties. While
non-invasive imaging of electrical properties using B1+
maps has been demonstrated for the brain, the method has
not been extended to other anatomical parts, partly due
to lack of transmit-receive coils to obtain accurate B1+
maps. We investigate the feasibility of breast
permittivity imaging using an eight channel, receive
only breast coil array and demonstrate permittivity
image consistent with adipose dominated breast tissue as
well as fat suppressed anatomical image.
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2533. |
Quantification Error in
MREPT due to B1 Map Inaccuracy
Jaewook Shin1, Joonsung Lee1, Jin
Keun Seo2, and Dong-Hyun Kim1
1Electrical & Electronic Engineering, Yonsei
University, Seoul, Korea, 2Computational
Science & Engineering, Yonsei University, Seoul, Korea
Magnetic Resonance Electrical Property Tomography (MREPT)
is recently introduced to noninvasively image the
distribution of electric conductivity and permittivity
in the human body at the Larmor frequency. Over
homogeneous regions, the relationship between the
electric properties and magnetic fields can be
simplified as a Helmholtz equation of B1+. In this work,
the methods using B1+ maps generated by EM simulations
on numerical phantoms with two tissues were proposed to
investigate and evaluate how the error in the
conductivity estimates using the Helmholtz equation of
B1+ is related to the SNR of B1+ and the size of the
tissue.
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2534. |
Feasibility of
Submillimeter Resolution MREIT Conductivity Imaging:
Preliminary Phantom Study
Hyung Joong Kim1, Woo Chul Jeong1,
Young Tae Kim1, Munish Chauhan1,
and Eung Je Woo1
1Biomedical Engineering, Kyung Hee
University, Yongin, Gyeonggi, Korea
Recent experimental MREIT studies demonstrated
conductivity image reconstructions of in vivo animal and
human subjects with a few millimeter pixel size. Such a
resolution could be sufficient to distinguish different
human tissues for certain applications. In order to
visualize a conductivity distribution within a tissue or
a small animal, it is necessary to develop a
high-resolution MREIT technique. The experimental
results using a 4.7 T research MRI scanner with a
multi-echo ICNE pulse sequence and high-performance RF
coils demonstrate that we can distinguish two different
anomalies in reconstructed conductivity images with a
pixel size as small as 400 ¥ìm.
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Traditional
Poster Session - Pulse Sequences & Reconstruction B |
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|
Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
|
Exhibition Hall |
16:00 - 18:00 |
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2535. |
A Novel Method for Coil
Array Synthesis and Application to Breast MRI
Anderson Nnewihe1,2, Bruce L Daniel1,
Deqiang Qiu1, Jafi Lipson1,
Jarrett Rosenberg1, Debra Ikeda1,
Sung H Kim1,3, Jennifer Kao1, and
Brian A Hargreaves1
1Radiology, Stanford University, Stanford,
California, United States, 2Bioengineering,
Stanford University, Stanford, California, United
States, 3Radiology,
Seoul St. Mary's Hospital, The Catholic University of
Korea, Seoul, Korea
The primary purpose of this work is to introduce and
validate a method of synthesizing image data for an RF
coil array given data from a second array. This would
enable future studies comparing two coil arrays (source
and reference arrays) for situations where it is not
practical to acquire data with both such as breast
contrast-enhanced MRI. For the future studies, the
synthesized images would be used as a proxy for the
reference coil array data. In a survey of experienced
breast radiologists, we showed equivalence of the
overall preference between the synthesized and reference
coil array images.
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2536. |
Vessel-Mimicking Mask for
Improved Unfolding in SENSE-Accelerated CE-MRA
Eric G. Stinson1, Casey P. Johnson1,
and Stephen J. Riederer1
1MR Research Laboratory, Mayo Clinic,
Rochester, Minnesota, United States
Masking in SENSE unfolding is known to reduce noise
amplification and preserve SNR. Further, in
contrast-enhanced MR angiography (CE-MRA), the final
volume of interest is often a difference volume where,
in the ideal case, signal is only present in the
vasculature. The purpose of this work is to investigate
the feasibility of improving the performance of 2D SENSE
in 3D CE-MRA by masking all non-vascular voxels prior to
performing the SENSE unfolding of a difference
angiogram. Thigh CE-MRA exams were unfolded with
conventional and vessel-mimicking masks and compared
with respect to maximum intensity projection
contrast-to-noise ratio and mean g-factor.
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2537. |
An Inexpensive Iterative
Reconstruction for Under-sampled PROPELLER MRI
Jyh-Miin Lin1,2, Tzu-Chao Chuang2,
Hing-Chiu Chang3,4, Wen-Chau Wu5,
and Hsiao-Wen Chung4,6
1Department of Radiology, Duke University
Medical Center, Durham, NC, United States, 2Department
of Electrical Engineering, National Sun Yat-sen
University, Kaohsiung, Taiwan, 3Global
Applied Science Laboratory, GE Healthcare, Taipei,
Taiwan, 4Institute
of Biomedical Electronics and Bioinformatics, National
Taiwan University, Taipei, Taiwan,5Graduate
Institute of Oncology, National Taiwan University,
Taipei, Taiwan, 6Department
of Electrical Engineering, National Taiwan University,
Taipei, Taiwan
Previously researchers had shown the possibility to use
iterative reconstruction to process PROPELLER images. In
this study, an economic algorithm named image space
reconstruction algorithm (ISRA) is implemented for
under-sampled PROPELLER MRI. Based on generalized
inverse, the algorithm is fast and inexpensive, which is
useful for dynamic or volumetric imaging. We performed
phantom study with under-sampled PROPELLER images, in
which the image qualities were restored by ISRA.
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2538. |
Automatic Regularization
Parameter Selection for Iterative Nonlinear MRI
Reconstruction
Sathish Ramani1, Jon-Fredrik Nielsen2,
and Jeffrey A. Fessler1
1EECS, University of Michigan, Ann Arbor,
Michigan, United States, 2fMRI
Laboratory, University of Michigan, Ann Arbor, Michigan,
United States
MRI reconstruction from undersampled sampled k-space
data requires regularization to reduce artifacts.
Nonquadratic regularization (e.g., l1 or TV) can be used
to restore image quality, but its successful application
depends on proper selection of the regularization
parameter. In this work, we demonstrate the
applicability of generalized cross validation (GCV) and
an estimate of a mean-squared error (MSE)-type measure
for quantitative selection of the regularization
parameter for MRI reconstruction using the iterative
split-Bregman algorithm with nonquadratic
regularization. GCV and the MSE-type estimate require
the Jacobian matrix of the reconstruction with respect
to the data that we evaluate analytically for the SB
algorithm. We illustrate with experiments on real MR
(phantom) data that GCV and the MSE-type estimate lead
to near-optimal reconstruction results.
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2539. |
Faster and More Robust MRI
Using Sharable Information Among Images With Different
Contrasts
Feng Huang1, Yu Li2, Wei Lin1,
George Randy Duensing1, and Arne Reykowski1
1Invivo Corporation, Gainesville, FL, United
States, 2Radiology
Department, Cincinnati Children's Hospital Medical
Center
A typical clinical MR examination is composed of a
number of scans to acquired images with different
contrasts, such as T1w, T2w and DWI. Currently, the
acquisition and reconstruction schemes of these scans
are independent to each other. In the presented work, we
propose to jointly optimizing the acquisitions and
reconstructions of a multi-scan MRI examination for
faster and more robust MRI. The theory behind this
concept is that the information such as B0 field,
optimized acquisition trajectory, reconstruction
parameters, etc, can be shared among all scans for
different contrasts since the same subject is scanned in
the same system using the same RF coil. This idea is
fundamentally different from previous method that using
one set of acquisition to artificially produce images
with different contrast.
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2540. |
Improving SNR and
Sensitivity of 3D Fluorine Imaging With a
Side-Information-Constrained Regularized Reconstruction
Samuel Fielden1, Alexander Klibanov1,2,
Yaquin Xu1, Frederick Epstein1,3,
Brent French1,3, and Craig Meyer1,3
1Biomedical Engineering, University of
Virginia, Charlottesville, Virginia, United States, 2Medicine,
University of Virginia, 3Radiology,
University of Virginia
Second color, or hot spot, fluorine imaging benefits
from 3D acquisition from both a signal localization
point of view and a desire to maximize signal
sensitivity. Here we show fluorine nanoparticle-labeled
macrophage infiltration into infarcted myocardium using
a gated 3D turbo spin echo sequence, and improve the SNR
and sensitivity using a regularized reconstruction
technique which utilizes side information obtained from
proton scout images.
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2541. |
Vessel Adapted
Regularization for Iterative Reconstruction in MR
Angiography
Jana Hutter1,2, Robert Grimm1,
Christoph Forman1,2, Joachim Hornegger1,2,
and Peter Schmitt3
1Pattern recognition lab, Universität
Erlangen-Nürnberg, Erlangen, Germany, 2Erlangen
graduate school in avanced optical technologies,
Erlangen, Germany, 3MR
Application & Workflow Development, Siemens AG,
Healthcare Sector, Erlangen, Germany
Iterative methods such as Compressed Sensing involve
regularization terms to stabilize and accelerate the
optimization. Smoothness and sparsity assumptions are
widely used as regularization, but the special structure
of angiographic data is not yet part of the
regularization. Our new method takes the localization
and brightness of vessels, adapted to each individual
vessel, into account. The information is extracted using
an ellipsoid-based segmentation approach and included
into the reconstruction with a modified Gaussian penalty
map. This approach proved to be beneficial for the
reconstruction time as well as for the general image
quality.
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2542. |
GRAPPA Operator Shift
Correction for Non-Cartesian Imaging Trajectories
Anagha Deshmane1, Nicole Seiberlich1,
Jeffrey Duerk1,2, and Mark A. Griswold1,2
1Dept. of Biomedical Engineering, Case
Western Reserve University, Cleveland, OH, United
States, 2Dept.
of Radiology, University Hospitals of Cleveland,
Cleveland, OH, United States
Gradient timing delays can cause deviations from the
ideal trajectory in non-Cartesian imaging. The proposed
method aims to correct for trajectory errors and
determine the signal at the center of k-space. Paths
between points acquired along mis-centered radial
projections and the true center of k-space are traced by
a gradient ascent algorithm which iteratively applies a
GRAPPA operator to shift k-space data while continually
evaluating an estimate of the echo peak signal. This
method can be used to perform trajectory measurement
without field monitoring or extra acquisitions, and
signal at the true k-space center can be used for
retrospective self-gated imaging.
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2543. |
Inter-slice artifact
reduction for slice-GRAPPA reconstruction of simultaneous
multi-slice (SMS) acquisitions
Stephen F Cauley1, Kawin Setsompop1,2,
Jonathan R Polimeni1,2, and Lawrence L Wald1,3
1A. A. Martinos Center for Biomedical
Imaging, Dept. of Radiology, MGH, Charlestown, MA,
United States, 2Harvard
Medical School, Boston, MA, United States, 3Harvard-MIT
Division of Health Sciences and Technology, MIT,
Cambridge, MA, United States
For full-brain coverage simultaneously acquiring
multiple slices can significantly improve acquisition
time. Controlling the unaliasing process is extremely
important given the presence of noise and artifacts in
fMRI and diffusion. In this work we test a constrained
optimization technique that reduces inter-slice
artifacts by more than 10 fold. The improved kernels can
be used in both fMRI and diffusion weighting studies for
increased accuracy. The convex model ensures optimal
solutions given the constraints and is implemented
easily using readily available optimization packages.
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2544. |
Partial Fourier
accelerated spiral SENSE imaging using magnetic field
monitoring
Bertram Jakob Wilm1, Christoph Barmet1,
Lars Kasper1, Max Haeberlin1,
Benjamin Emanuel Dietrich1, and Klaas Paul
Pruessmann1
1Institute for Biomedical Engineering, ETH
Zurich and University of Zurich, Zurich, Switzerland
A combination of spiral MRI with partial Fourier phase
constrained imaging could allow decreasing the
acquisition duration, and thus to increase the
achievable temporal resolution in MRI. However, accurate
knowledge about the image phase that is required for
partial Fourier imaging is hard to establish, since
spiral imaging is very sensitive to any encoding
deficiencies, such as gradient delays, eddy currents,
concomitant fields and static B0 inhomogeneity. To
overcome this problem, an accurate model of the dynamic
field encoding is obtained by using dynamic field
monitoring. The performance and the sensitivity against
inaccuracy of the phase estimate are evaluated in vivo.
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2545. |
Multi-Coil Imaging with
Algebraic Reconstruction
Christoph Juchem1, Terence W Nixon1,
and Robin A de Graaf1
1Yale University School of Medicine, New
Haven, CT, United States
Today’s MR imaging methods use low-order SH shapes or
combinations thereof. Here we show that MR imaging does
not rely on SH shapes and can also be achieved with
random magnetic field shapes when analyzed by algebraic
reconstruction. Magnetic fields for spatial encoding
were generated with the multi-coil (MC) approach by a
matrix of simple, circular coils.
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2546. |
A Density Compensation
Function using Kaiser-Bessel Regridding
Lawrence Dougherty1, and Gamaliel Isaac1
1Radiology, University of Pennsylvania,
Philadelphia, PA, United States
A rapid density compensation function (DCF) was
developed and tested for reconstruction of non-Cartesian
sampled data. Sampling locations were gridded onto a map
in the same manner as the MR data. This creates a
density map that is used to compensate for the irregular
sampling. Phantom images were reconstructed using the
gridded DCF from data acquired with a Golden-angle
radial sequence and showed good performance as compared
to a Ram-Lak filter or density computed from K-space
area. The method is rapid and flexible, requiring only
the knowledge of each sample’s position in K-space and
is simple to implement.
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2547. |
Sampling Density
Compensation Function Estimation by Regularized Conjugate
Gradient Iteration with a Reduced Oversampling Ratio
Sen Jia1, and Ran Yang1
1School of Information Science and
Technology, Sun Yat-Sen University, Guang Zhou, Guang
Dong, China
The iterative convolution based estimation of
non-Cartesian sampling density compensation function (DCF)
typically employs an intermediate Cartesian grid
oversampled by a ratio of two to achieve high
convergence accuracy and this increases the memory and
computational burden heavily when processing data of
large size or of high dimension. And the iteration
converges stably but saturates easily which limits the
capacity to achieve higher estimation accuracy. In this
work, an iterative procedure based on the Conjugate
Gradient (CG) method is introduced to reduce the
oversampled grid size while achieving higher DCF
estimation accuracy without increasing computational and
storage burden. Further the DCF estimated by the
original method is employed as a regularization term to
form a bi-criterion optimization problem to stabilize
the CG iteration to achieve fast convergence with a
reduced oversampling ratio.
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2548. |
Generalized Conjugate
Gradient Image Reconstruction – Combination of SENSE/SPIRiT,
Chemical Shift Imaging and Multi-Frequency Interpolation
Jonathan I. Sperl1, Florian Wiesinger1,
and Rolf F. Schulte1
1GE Global Research, Garching n. Munich, BY,
Germany
Image Reconstruction in MRI is addressed by a variety of
techniques depending on the specific data acquisition
scheme and the information one wants to resolve. This
work proposes a general Conjugate Gradient
reconstruction framework that can be applied to a wide
range of MRI data sets. In more detail, we propose a
generalized SENSE or SPIRiT type of reconstruction
combining chemical shift imaging, e.g. to resolve
different metabolites in vivo, and Multi-Frequency
Interpolation for B0-correction. The method is applied
to a severely B0-distorted 1H data set as well as to a
13C phantom experiment.
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2549. |
Generating synthetic DIR
images using multi-parameter maps: application to lesion
detection in MS
Riddhi Rajgor1, Nils Muhlert2,
Antoine Lutti3, Matteo Atzori4,5,
Nikolaus Weiskopf3, Claudia AM
Wheeler-Kingshott2, Xavier Golay1,
Alan J Thompson4, Olga Ciccarelli4,
and David L Thomas1
1Department of Brain Repair and
Rehabilitation, UCL Institute of Neurology, London,
United Kingdom, 2NMR
Research Unit, Department of Neuroinflammation, UCL
Institute of Neurology, London, United Kingdom, 3Wellcome
Trust Centre for Neuroimaging, UCL Institute of
Neurology, London, United Kingdom, 4NMR
Research Unit, Department of Brain Repair and
Rehabilitation, UCL Institute of Neurology, London,
United Kingdom, 5Department
of Neurology, University of Padova, Padova, Italy
DIR brain imaging is widely applied to patients with
multiple sclerosis, to suppress the signals from white
matter and CSF and facilitate the visualisation of
lesions. However, DIR is an inherently inefficient
technique, since long inversion and repetition times are
required to allow the desired contrast to evolve. The
aim of this work was to investigate the potential of
using FLASH-based multi-parameter mapping to generate
synthetic DIR images with equivalent image SNR and
contrast. It was found that synthetic DIR images
suppress unwanted tissue signals well, but do not
demonstrate grey matter lesions as clearly as acquired
DIR images.
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Traditional
Poster Session - Pulse Sequences & Reconstruction B |
|
Computational Implementation & Tools
Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
|
Exhibition Hall |
16:00 - 18:00 |
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2550. |
More IMPATIENT: A
Gridding-Accelerated Toeplitz-based Strategy for
Non-Cartesian High-Resolution 3D MRI on GPU
Jiading Gai1, Joseph Lee Holtrop2,
Xiao-Long Wu3, Fan Lam3, Maojing
Fu3, Justin P. Haldar4, Wen-mei W.
Hwu3, Zhi-Pei Liang3, and Bradley
P. Sutton2
1Beckman Institute, University of Illinois at
Urbana-Champaign, Urbana, IL, United States, 2Department
of Bioengineering, University of Illinois at
Urbana-Champaign, Urbana, IL, United States, 3Electrical
and Computer Engineering, University of Illinois at
Urbana-Champaign, Urbana, IL, United States, 4Electrical
Engineering, University of Southern California, Los
Angeles, CA, United States
We further accelerate the Illinois Massively Parallel
Acceleration Toolkit for Image reconstruction with
ENhanced Throughput in MRI (IMPATIENT MRI) package to
approach clinically- acceptable times while still taking
advantage of a variety of advanced image acquisitions
and reconstruction techniques. The improved IMPATIENT
implemented a faster Toeplitz-based iterative image
reconstruction method, whose computation time is further
reduced by an optimally tuned, GPU- accelerated gridding
implementation. We demonstrate that the Toeplitz code
running on a NVIDIA Tesla C1060 (field- corrected,
SENSE) can reduce a one-week long, non-Cartesian 3D 1mm3
high-resolution, whole brain DTI reconstruction
(4-channel acquisition) to 4.3 hours. These improvements
will enable advances in 3D non-Cartesian sequences, such
as cones and stacks of spirals.
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2551. |
High-Performance Gridding
on Modern x86-based Multi-core Systems for 3D Non-Cartesian
MRI
Dhiraj D. Kalamkar1, Joshua D. Trzasko2,
Srinivas Sridharan1, Mikhail Smelyanskiy3,
Daehyun Kim3, Yunhong Shu4, Matt
A. Bernstein4, Bharat Kaul1,
Pradeep Dubey3, and Armando Manduca2
1Parallel Computing Lab, Intel Labs,
Bangalore, KA, India, 2Mayo
Clinic, Rochester, MN, United States, 3Parallel
Computing Lab, Intel Labs, Santa Clara, CA, United
States,4Department of Radiology, Mayo Clinic,
Rochester, MN, United States
With increasing usage of higher-resolution acquisitions,
more receiver channels, and iterative reconstruction
strategies, the ability to quickly and accurately
transform an image to and from k-space, known as
“reverse gridding” and “gridding”, is crucial for
non-Cartesian MRI applications. In practice, both of
these operations are typically realized via the
non-uniform fast Fourier transform (NUFFT). In this
work, we propose a novel preprocessing and
parallelization strategy for both the forward and
adjoint NUFFT targeted for x86 architectures. We
demonstrate that this implementation strategy, which is
based on a variable-size geometric partitioning along
with a barrier-free task queue, and selective
privatization, is substantially faster than contemporary
x86 implementations, and computationally competitive
with state-of-the-art GPU implementations.
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2552. |
Parallel-Computing
Reconstruction for Parallel Encoding with Parallel Imaging
Ethan M Johnson1, and John M Pauly1
1Electrical Engineering, Stanford University,
Stanford, CA, United States
Recent innovation in MRI has tended to realise
improvements to image quality or reduction of
acquisition time by 'supplementing' the innate Fourier
encoding of magnetic resonance imaging. This typically
complexifies the data-image relationship, such that
reconstruction can become computationally expensive.
Within this class of innovations are techniques which
attempt to 'parallelise' the acquisition, with multiple
receiver coils and non-bijective encoding fields. In
these cases, reconstruction computations naturally
exhibit parallelism that can be exploited to reconstruct
images very quickly.
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2553. |
GPU-Accelerated Radial
Image Reconstruction with an Improved Parallel Gridding
Method
Jiangsheng Yu1, Yiqun Xue1, Xia
Zhao1, Ping Wang1, Walter Witschey1,
and Hee Kwon Song1
1University of Pennsylvania, Philadelphia,
PA, United States
Graphic processing units (GPU) have recently been
utilized to accelerate radial MR image reconstruction.
One of the challenges of gridding using GPU is the issue
of synchronization, and several approaches have been
reported to address this issue. This work presents a
simple and effective solution for avoiding this
synchronization problem by utilizing a
divide-and-conquer strategy that ensures that the
gridded points are non-overlapping. Performance tests on
the reconstruction of a DCE-MRI data set demonstrates
that an acceleration factor of 67 can be achieved on an
Nvida Tesla C2050 GPU system.
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2554. |
Low-Latency Radial GRAPPA
Reconstruction using Multi-Core CPUs and General Purpose GPU
Programming
Haris Saybasili1,2, Daniel A. Herzka2,
Nicole Seiberlich3, and Mark Griswold1,3
1Department of Radiology, Case Western
Reserve University, Cleveland, OH, United States, 2Biomedical
Engineering, Johns Hopkins University School of
Medicine, Baltimore, MD, United States, 3Biomedical
Engineering, Case Western Reserve University, Cleveland,
OH, United States
Real-time imaging using non-Cartesian trajectories
permits very high acceleration rates with parallel
imaging. However, image reconstruction from undersampled
non-Cartesian datasets is computationally demanding, and
leads to long reconstruction times .We present a hybrid
(CPU- and GPU-based), fully auto-calibrated, fast
reconstruction implementation for radial GRAPPA that
uses RT-GROG to grid radial data prior to FFT. Radial
GRAPPA and RT-GROG calibrations were performed on the
CPU, while image reconstruction was performed
asynchronously on the GPU. Our implementation was tested
on healthy volunteer cardiac data for different
parameters. Images from 12 coil, 144x256, R=9 data were
reconstructed in 33ms/frame (acquisition time
42ms/frame).
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2555. |
Gridding: Exploring an
Efficient Numerical Algorithm for 0-th Order Prolate
Spheroidal Wave Function Evaluation as Convolution Kernel
Laurent Lamalle1
1RMN biomédicale et Neurosciences — SFR UJF,
Inserm, Grenoble, Isère, France
An algorithm recently described for the efficient
numerical evaluation of Prolate Spheroidal Wave
Functions (PSWFs) was implemented in order to explore
the possibility of using the 0-th order PSWF as
convolution kernel in gridding reconstruction, instead
of its Kaiser-Bessel approximation. The problem of
evaluating the compensation function necessary after FFT
of the samples interpolated by convolution with the
kernel is addressed.
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2556. |
Fast l1-SPIRiT Compressed
Sensing Parallel Imaging MRI: Scalable Parallel
Implementation and Clinically Feasible Runtime
Mark Murphy1, and Miki Lustig2
1EECS UC Berkeley, Berkeley, CA, United
States, 2EECS
UC Berkeley
We describe the algorithmic and parallelization
implementation decisions that lead to fast runtimes in
l1-SPIRiT combined Parallel Imaging and Compressive
Sensing reconstruction.
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2557. |
System for Real-time
Reconstruction and Interactive Table Motion in Multi-Station
3D CE-MRA Exams
Eric A. Borisch1, Casey P. Johnson1,
Roger C. Grimm1, and Stephen J. Riederer1
1MR Research Laborary, Mayo Clinic,
Rochester, MN, United States
A system is described that enables multi-station
interactive bolus-chase CE-MRA examinations. The system
consists of: a custom pulse sequence with network
connectivity, interactive graphical interface for the
operator, and high-performance reconstruction software
and hardware. Reconstructions of the imaged 3D
time-series (acquired with 2.5s update times) are
completed and displayed to the operator within 110ms
while the examination is proceeding, enabling sufficient
time for the operator to visualize bolus transit to
determine if the current station is complete. The system
has been used successfully for three-station lower
extremity examinations.
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2558. |
StimFit: A toolbox for
robust T2 mapping with stimulated echo compensation
R. Marc Lebel1
1Department of Electrical Engineering,
University of Southern California, Los Angeles, CA,
United States
Quantitative T2 mapping provides an absolute measure of
transverse relaxation that is independent of other
confounding factors; however, heterogeneous transmit
fields and shaped RF pulses preclude the use a mono- or
multi-exponential fit to measure T2. We present a freely
available toolbox for robust quantitative T2 mapping
with stimulated echo compensation based on recently
published work. The toolbox enables accurate mono- or
multi-component analysis despite heterogeneous transmit
fields and slice-selective refocusing; the toolbox can
be obtained from http://mrel.usc.edu/.
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2559. |
A Digital Perfusion
Phantom for T1-weighted DCE-MRI
R. Grimm1, J. Churt2, A.
Fieselmann1, K. T. Block3, B.
Kiefer4, and J. Hornegger1
1Pattern Recognition Lab, University of
Erlangen-Nuremberg, Erlangen, Germany, 2Technical
University Munich, Munich, Germany, 3Department
of Radiology, NYU Langone Medical Center, New York, NY,
United States, 4MR
Application & Workflow Development, Siemens AG,
Healthcare Sector, Erlangen, Germany
Novel reconstruction techniques such as Compressed
Sensing promise high acceleration factors at a low noise
level but do not guarantee to preserve the correctness
of image intensities. This, however, is a prerequisite
for quantitative evaluations in Dynamic
Contrast-Enhanced MRI. To study these effects, an
analytical phantom is proposed that allows the
simulation of contrast agent kinetics in T1-weighted
imaging. It is based on the Shepp-Logan phantom and
supports sampling along arbitrary k-space trajectories.
Contrast enhancement in tissue is computed according to
the Tofts model, while for the arterial enhancement, the
Parker and Weinmann functions or user-defined time
curves can be used.
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Traditional
Poster Session - Pulse Sequences & Reconstruction B |
|
|
Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
|
Exhibition Hall |
16:00 - 18:00 |
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2560. |
Artificial neural networks
in radiological predictive models
Nikolaos Dikaios1, Taiki Fujiwara2,
David Atkinson3, and Shonit Punwani2
1Department of Medical Physics and
Bioengineering, University College London, London,
Greater London, United Kingdom, 2Department
of Radiology, University College London Hospital, 3University
College London, Centre for Medical Imaging
Predictive models are being increasingly employed in
radiology as diagnostic aids for cancer detection. A
variety of model types exist. Linear discriminant
analysis (LDA) models assume linearity, normality and
that the input variables are independent, assumptions
which may affect classification accuracy. Neural
networks (NN) whilst less intuitive, do not make these
assumptions and can detect complex non-linear
relationships between the input variables. Both LDA and
NN are prone to over-fitting. In this work we compared
the performance of multilayer perceptron (MLP)
artificial NN and LDA models for prediction of
transition zone (TZ) prostate cancer (based on
quantitative multi-parametric MRI variables) using a
leave-one-out (LOO) and a 2-fold cross validation
analysis.
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2561. |
Method for Improving
Segmentation of Multispectral brain MRI by a Supervised
Hybrid Classifier
Jyh-Wen Chai1, Clayton Chi-Chang Chen1,
Hsian-Min Chen2, Yaw-Jiunn Chiou3,
Shih-Yu Chen4, Yi-Ying Wu1, Chih-Ming
Chiang1, Ching-Wen Yang5, Yen-Chieh
Ouyang6, San-Kan Lee1, and Chein_I
Chang4
1Department of Radiology, Taichung Veterans
General Hospital, Taichung, Taiwan, 2Department
of Biomedical Engineering, HungKung university,
Taichung, Taiwan,3Department of Electrical
Engineering, National Chung Hsing University, 4Department
of Computer Science and Electrical Engineering,
University of Maryland, Baltimore County, Baltimore, MD, 5Computer
Center, Taichung Veterans General Hospital, Taichung,
Taiwan, 6Department
of Electrical Engineering, National Chung Hsing
University, Taichung, Taiwan
A hybrid classifier, derived from iterative Fisher¡¦s
linear discriminant analysis coupled with the volume
sphering analysis and support vecter machine, was
developed to effectively segment multi-slice data of
multispectral brain MRI by using only one set of
training samples. The proposed method has several
advantages. One was a reduction of computational cost in
data processing since it only needs one set of training
samples to process the entire multislice images.
Besides, the same saving is also applied in minimizing
operator burden. The uppermost benefit is to avoid
operator interferences from selecting training samples
and improve the reproducibility.
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2562. |
Performance of an
automated segmentation algorithm for MR renography
Artem Mikheev1, Jeff L Zhang2,
Tariq Gill1, Marta Heilbrun2,
Stella Kang1, Hersh Chandarana1,
Henry Rusinek1, and Vivian S Lee2
1Radiology, NYU School of Medicine, New York,
NY, United States, 2Radiology,
University of Utah School of Medicine, Salt Lake City,
UT, United States
A key prerequisite for analysis of MR renography (MRR)
data is the ability to segment MRI images. We have
developed and validated a new semi-automated renal
segmentation technique based on edge-constrained region
growing. The segmentation error is 7.6 ± 6.5 cm3 and the
interobserver disparity 5.4 ± 4.5 cm3, a significant
improvement over graph-cut method. The new algorithm
achieves a ten-fold improvement in user processing time,
from >20 min to 2.1 ± 0.7 min per kidney. With expedited
image processing, MRR has the potential to expand our
knowledge of renal function and to help diagnose
different types of renal insufficiency.
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2563. |
A fully automated,
hierarchical classification method for detecting white
matter lesions in Multiple Sclerosis
Marco Battaglini1, Nicola De Stefano1,
and Mark Jenkinson2
1Neurological and behavioral sciences,
University of Siena, Siena, Tuscany, Italy, 2FMRIB
Centre, Nuffield Department of Clinical Neurosciences,
University of Oxford
A novel hierarchical classification method for
segmenting lesions in Multiple Sclerosis is described.
It uses two stages: (1) a standard voxel-wise classifier
followed by (2) a novel cluster-wise classifier.
Features used for the cluster-wise classifier consist of
ratios of statistics extracted from within the
first-level clusters (across several different image
modalities), to those from the exterior borders of the
clusters or from all Grey Matter or White Matter voxels.
Results on images from a multi-site clinical dataset
showed large reductions in False Positives (for voxel-based
and lesion-based metrics), with minimal reductions in
True Positives, demonstrating great potential for this
approach.
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2564. |
Multi-Atlas Corpus
Callosum Segmentation with Adaptive Atlas Selection
Babak A. Ardekani 1,2, Toshikazu Ikuta 3,4,
Alvin Bachman 1, and Philip R. Szeszko 3,4
1Center for Advanced Brain Imaging, Nathan
Kline Institute for Psychiatric Research, Orangeburg,
NY, United States, 2Department
of Psychiatry, New York University School of Medicine,
New York, NY, United States, 3Feinstein
Institute for Medical Research, Manhasset, NY, United
States, 4Psychiatry
Research, The Zucker Hillside Hospital, Glen Oaks, NY,
United States |
|
2565. |
Automatic segmentation of
breast lesions in dynamic contrast-enhanced MR images
Jonathan Arvidsson1, Fredrik Johansson1,
Andrew Mehnert1,2, Darryl McClymont3,
and Dominic Kennedy4
1Signals and Systems, Chalmers University of
Technology, Gothenburg, Sweden, 2MedTech
West, Gothenburg, Sweden, 3ITEE,
The University of Queensland, Brisbane, Queensland,
Australia, 4Queensland
X-Ray, Greenslopes, Queensland, Australia
A novel method for automatically segmenting 3D lesions
in dynamic contrast-enhanced breast MRI data is
proposed. It is based on assigning a “suspiciousness”
score to each voxel using features extracted from its
time series, and then computing the spatial
co-occurrence of this score in a 3D neighborhood about
the voxel. In this way both the spatial and temporal
variation in contrast enhancement are characterized. An
empirical evaluation of the efficacy of this technique
versus a competing method based on multispectral
co-occurrence is also presented.
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2566. |
Fusion of electrical
impedance tomography data with MRI
Ross A Little1, John L Davidson2,
Josephine H Naish1, Paul Wright2,
Ron Kikinis3, Hugh McCann2, and
Geoff J Parker1
1Imaging Sciences, Manchester Academic Health
Sciences Centre, University of Manchester, Manchester,
United Kingdom, 2School
of Electrical and Electronic Engineering, University of
Manchester, United Kingdom, 3Surgical
Planning Laboratory, Brigham and Women's Hospital,
Harvard Medical School, Boston, MA, United States
We are interested in fusing electrical impedance
tomography (EIT) data with MRI, to give temporally and
anatomically resolved functional lung imaging. We have
progressed this using gel-based phantoms using the
Confeitir (CONverter of Functional Electrical Impedance
Tomography Images for Registration) software and the 3D
Slicer package. EIT data were captured using fEITER, a
biomedical EIT instrument operating at 100 frames per
second. 3D Slicer was used to import and align the
images, which show good correspondence between the two
modalities. We intend to use similar methods to jointly
visualise human lung data acquired using both EIT and
MRI.
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2567. |
A rigid Registration
Method for automated Scan Planning in Follow-up
Examinations: Retrospective Analysis from Volunteer and
Patient Neuro Scans
Julien Sénégas1, Torbjoern Vik1,
Jens von Berg1, Peter Koken1,
Juergen Gieseke2,3, Vincent Denolin4,
Roy König3, and Stefan Sunaert5
1Philips Research Laboratories, Hamburg,
Germany, 2Philips
Healthcare, Best, Netherlands, 3Radiology,
University of Bonn, Bonn, Germany, 4Philips
Healthcare, Brussels, Belgium, 5Medical
Imaging Center, Radiology, Catholic University of
Leuven, UZ Leuven, Leuven, Belgium
MRI based monitoring of cerebral diseases such as brain
tumors and multiple-sclerosis requires a precise
comparison of the signal intensity and structure between
baseline and follow-up exams. To minimize visual changes
due to variations in patient positioning and scan
planning, an accurate replication of the baseline
acquisition geometry is desired. If done manually by
visual inspection of the baseline images, this is a very
tedious, time-consuming procedure with limited accuracy.
In this work, we propose a general approach for
automated scan planning in follow-up exams that only
requires the baseline diagnostic images as input, with
no further restrictions on the baseline exam as far as
types of MR sequences, of MR scanner (vendor, field
strength) or of planning (automated or manual) are
concerned. Results from a preliminary study based on a
retrospective analysis of volunteer and patient scans
are presented.
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2568. |
A Model-Based Method for
Registration of Ex Vivo to In Vivo Prostate MRI Using
Elastography
Guy Nir1, Ramin S. Sahebjavaher1,
Piotr Kozlowski2, Ralph Sinkus3,
and Septimiu E. Salcudean1
1Electrical and Computer Engineering,
University of British Columbia, Vancouver, BC, Canada, 2MRI
Research Centre, University of British Columbia,
Vancouver, BC, Canada,3Centre de Recherche
Biomédicale Bichat-Beaujon (CRB3), Paris, France
We propose a novel method for registration of an ex vivo
3D model of a prostate to an in vivo MRI volumetric
image. Such method may be employed to generate
probability maps for prostate cancer distribution. The
in vivo scan is followed by an MR elastography scan,
from which the true elasticity parameters can be
extracted and assigned to each voxel of the in vivo
image. This allows a realistic regularization of a
non-rigid registration method in order for it to produce
physical and accurate deformation maps. Experiments on
both synthetic and clinical data show promising results.
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2569. |
Automatic Template-based
Breast Segmentation on MRI Using Nonrigid Registration
Algorithms
Muqing Lin1, Jeon-Hor Chen1,2,
Orhan Nalcioglu1, and Min-Ying Lydia Su1
1Tu & Yuen Center for Functional Onco
Imaging, University of California, Irvine, California,
United States, 2Department
of Radiology, China Medical University Hospital,
Taichung, Taiwan
The purpose is to develop an automatic breast
segmentation method in MRI. The new algorithm is based
on template matching of chest region using nonrigid
registration. The body landmarks defined on the template
can be transformed to subject’s space for performing
v-shape cut to determine the posterior boundary of the
lateral breasts. The chest wall mussel is excluded using
Bezier curve fitting. The results show that this
template-based segmentation method can accurately
segment different types of breasts. This tool can help
developing computer-aided-diagnosis method for detection
of breast cancer, as well as quantitative analysis of
breast density for risk management.
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2570. |
Population-based human
brain MRI atlas with sharp contrast and its application in
image registration
Yajing Zhang1, Jiangyang Zhang2,
Michael I. Miller1,3, and Susumu Mori2
1Department of Biomedical Engineering, Johns
Hopkins University, Baltimore, MD, United States, 2Department
of Radiology, Johns Hopkins University School of
Medicine, Baltimore, MD, United States, 3Center
of Imaging Science, Johns Hopkins University, Baltimore,
MD, United States
An MR based brain atlas is a key component in modern
image analysis process. In this study, a
population-based brain atlas with preserved image
resolution was generated from normal aged control and
age-matched AD datasets, using a continuous fluid
dynamic model. This so-called VTE atlas presents a group
averaged shape that minimize its anatomical bias while
preserves sharp contrast for accurate image mapping. The
characteristics of the new atlas were examined with
respect to single subject atlases and group averaged
atlases. The registration accuracy by using the new
atlas was compared with commonly used single subject
atlas through kappa analysis.
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|
|
Traditional
Poster Session - Pulse Sequences & Reconstruction B |
|
|
Click on
to view
the abstract pdf. Click on
to view
the poster (Not all posters are available for viewing.)
Wednesday 9 May 2012
|
Exhibition Hall |
16:00 - 18:00 |
|
|
|
2571. |
Investigation of the
Resolution Dependence of White Matter Structure Analysis by
Means of Variography
Fabian Keil1, Daniel Brenner1,
Ana-Maria Oros-Peusquens1, and N. Jon Shah1,2
1Institute of Neuroscience and Medicine - 4,
Forschungszentrum Jülich, Jülich, Germany, 2JARA
- Faculty of Medicine, RWTH Aachen University, Aachen,
Germany
Variography is a novel method for the quantification of
heterogeneities and spatial correlations in 3D MP-RAGE
images of white matter. This abstract investigates the
resolution dependence of variographic analyses applied
to MR images. The change of the variogram is
demonstrated and analysed by means of a digitised,
high-resolution photograph of a human brain slice. A
method for the correction of resolution-based changes is
introduced and applied to the low resolution variograms.
The estimated correlation parameters of corrected,
uncorrected and native variograms are compared and
evaluated.
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2572. |
Quantitative comparison of
the informational content of T2*-weighted
magnitude, phase and SWI 7T MR data by means of texture
analysis of the cortical ribbon in elderly subjects
N. T. Doan1, S. van Rooden2,3, M.
J. Versluis2, A. G. Webb2, J. van
der Grond3, M. A. van Buchem3, J.
H. C. Reiber1, and J. Milles1
1LKEB - Department of Radiology, Leiden
University Medical Center, Leiden, Zuid Holland,
Netherlands, 2CJ
Gorter Center - Department of Radiology, Leiden
University Medical Center, Leiden, Zuid Holland,
Netherlands, 3Department
of Radiology, Leiden University Medical Center, Leiden,
Zuid Holland, Netherlands
The aim of this work is to investigate and compare the
information content of T2*-weighted magnitude, phase and
SWI data by means of texture analysis. Textural features
of the cerebral cortex on magnitude, phase or SWI images
were derived based on Gray Level Co-occurrence Matrix.
Subsequently, classification using respectively
magnitude-based, phase-based and SWI-based features was
carried out with a Fisher linear discriminant classifier
and a leave-one-out cross-validation approach. The
results suggest that, from a texture information
perspective, phase images have higher information
content than either magnitude or SWI images.
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2573. |
Comparing Anisotropic
Diffusion Filters: Enhancement of 23Na
MRI of Human Kidney
Frank G Zoellner1, Christoph M Decker1,
Simon Konstandin1, and Lothar R Schad1
1Computer Assisted Clinical Medicine,
Heidelberg University, Mannheim, Germany
In-vivo MR imaging of sodium is limited due to its
electro-physiological characteristics. A logical step
forward is to enhance image intensity by applying
post-processing filters while Gibb’s ringing could also
be suppressed. The increase in signal-to-noise ratio (SNR)
by linear filters as previously proposed is paid by a
loss in resolution (blurring). Filters that preserve
contours while removing noise are anisotropic diffusion
filters (AND). The aim of this study was to compare
different anisotropic filters for enhancing sodium MR
images of the kidney.
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2574. |
Comparison of single ROI
Vs whole liver determination of liver steatosis
A F Alsalihi1,2, G J Cowin1, J R
Jonsson3, E E Powell3, A D
Clouston3, M Benson4, and G J
Galloway1
1Centre for Advanced Imaging- The University
of Queensland, Brisbane, QLD, Australia, 2Pysics
Department, Education College, Basrah University, Basrah,
Basrah, Iraq,3School of Medicine, The
University of Queensland, Brisbane, QLD, Australia, 4Department
of Radiology, Princess Alexandra Hospital, Brisbane, QLD,
Australia
Purpose This study compares whole liver estimation of
liver steatosis with defined region of interest methods.
Methods Liver fat was measured by liver biopsy, MRS and
MRI using IP/OP and ±fat sat. Analysis methods:
Correlations were investigated between the following:
whole liver IP/OP and ±fat sat, single ROI liver IP/OP
and ±fat sat, MRS, biopsy results. Results All methods
tested for the determination of liver fat were highly
correlated. Conclusion These results suggest a single
ROI does not increase the error in the estimation of
liver steatosis using imaging methods
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