Adam Maunder¹, Mojgan Daneshmand¹, Pedram Mousavi¹, B. Gino Fallone², and Nicola De Zanche^2
1Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada, ²Oncology, University of Alberta, Edmonton, Alberta, Canada

Despite its impact on array coupling and design, especially for higher frequencies, capacitance between coils has not been studied quantitatively. The proposed capacitive coupling circuit model is shown to accurately predict simulated and measured impedance changes, as well as measured noise correlations. An important application is the reduction or elimination of both reactive and resistive coupling with appropriate adjustments of inter-element capacitance. This model includes mutual inductance and resistance, and quantifies the effect and amount of parasitic capacitive coupling.

Pei-Shan Wei¹, Scott B. King^1,2, Michael J. Smith², Jarod Matwiy², and Christopher P. Bidinosti^3
1Departmentof Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada, ²National Research Council of Canada, Winnipeg, Manitoba, Canada, ³Department of Physics, University of Winnipeg, Winnipeg, Manitoba, Canada

An accurate modeling of a constructed coil contains resistive and mutual inductance coupling and preamplifier de-coupling information in realistic electromagnetic fields and is important for optimization of SNR and g-factor. Noise correlation analysis and current ratio of induced current relative to the primary current at different angular position representing different coupling have been used to evaluate the perturbation in the B/E- field distribution. Our results suggest that incorporating a preamplifier circuit into the coil model can accurately simulate decoupling and is suitable for phased array coil optimization.

Zohaib Mahmood¹, Bastien Guérin², Elfar Adalsteinsson^1,3, Lawrence L. Wald^2,3, and Luca Daniel^1
1Dept of Electrical Engineering & Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, ²Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, United States, ³Harvard-MIT Division of Health Sciences Technology, Cambridge, Massachusetts, United States

In this paper we present an algorithm to automatically design a decoupling matrix for pTx arrays with many channels. The algorithm optimally selects the decoupling matrix based on the constraints defined on network such as reciprocity, passivity and the network being lossless. We show that our algorithm converges and the decoupling matrix achieves ideal decoupling. We explore various useful features of the decoupling network by analyzing L-curves and singular values. However the problem of realizing the optimal decoupling matrix using practical circuits is still open and is currently work in progress.

Russell Lagore¹, Al-Karim A. Damji¹, Alan H. Wilman¹, and Nicola De Zanche^2
1Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada, ²Department of Oncology, University of Alberta, Edmonton, Alberta, Canada

Gallium Arsenide (GaAs) and Silicon Germanium (SiGe) semiconductor devices behave differently in terms of gain and noise figure as B₀ field strength increases and orientation varies. SiGe devices are essentially immune to B₀ field variation while the more common GaAs devices are highly sensitive.

Wei Zhao¹, Boris Keil¹, Jonnathan R. Polimeni¹, James N. Blau¹, Azma Mareyam¹, Thomas Witzel¹, Elfar Adalsteinsson², and Lawrence L. Wald^1,3
1A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States, ²Electrical Engineering and Computer Science, MIT, Cambridge, MA, United States, ³Division of Health Sciences and Technology, Harvard-MIT, Cambridge, MA, United States

Ultra-high field MRI can potentially improve diagnostic power using a coil setup consisting of a pTx array and a separate multi-channel Rx array. 32-channel receive arrays have been widely used in 7T brain MRI for improving sensitivity and parallel imaging performance. The use of simultaneous reception with multiple coils to speed-up encoding, has proven to be a requirement for obtaining high spatial resolution fMRI at 7T. Therefore, for improving the image quality of the pTx system, we combined a 16-channel transmit array and a 32-channel receive array with the ability for highly accelerated encoding and to perform parallel transmit excitations.

Kyoung-Nam Kim¹, Gyu Cheol Han², Phil Heo¹, Hongbae Jeong¹, Suk-Min Hong¹, Joshua Haekyun Park¹, Myung-Kyun Woo¹, Young-Bo Kim¹, and Zang-Hee Cho^1
1Neuroscience Research Institute, Gachon University, Incheon, Korea, ²Department of Otolaryngology-HNS, Gachon University, Incheon, Korea

The cochlear and the vestibular system play important roles in sound perception and maintaining the body equilibrium by sensing body movements and sending signals to the brain through mechanoelectric transduction. In order to use MRI for diagnosing inner ear diseases, improvement in the sensitivity of MRI and the development of an optimized special RF coil system and proper sequence protocol are needed. We presented preliminary results for visualization of the inner ear for the first time using only a customized RF coil and without the use of a contrast medium at 7 T.

Kyoung-Nam Kim¹, Phil Heo¹, Gyu Cheol Han², Hongbae Jeong¹, Suk-Min Hong¹, Myung-Kyun Woo¹, Myung-Kyun Woo¹, Joshua Haekyun Park¹, Young-Bo Kim¹, and Zang-Hee Cho^1
1Neuroscience Research Institute, Gachon University, Incheon, Korea, ²Department of Otolaryngology-HNS, Gachon University, Incheon, Korea

To achieve ultra-structural magnetic resonance imaging (MRI) of inner ear, hybrid radiofrequency (RF) coils and their integrated RF circuitries was employed at 7 T MRI and targeted to allowing the feasibility of small anatomical imaging. The coil configuration of hybrid RF coils for inner ear MR imaging was consist of two parts of 8-channel volume transmit/receive (Tx/Rx) and planar type of dual 4-channel Rx-only coil for simultaneous RF signal acquisition at 7 T. In in-vivo inner ear MR imaging, the hybrid RF coils showed improvement of SNR in the inner ear included cochlear, semicircular canal, and other organs was achieved and thus coverage to allow adequate observation of the encompassed anatomy of inner ear.

Jiaming Cui¹, Ivan E. Dimitrov^2,3, Sergey Cheshkov^2,4, Mary P. McDougall^1,5, Craig R. Malloy^2,4, and Steven M. Wright^1,5
1Electrical and Computer Engineering, Texas A&M University, College Station, Texas, United States, ²Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States, ³Philips Medical systems, Cleveland, Ohio, United States, ⁴Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, United States, ⁵Biomedical Engineering, Texas A&M University, College Station, Texas, United States

Breast imaging and spectroscopy are of interest at 7T. In this abstract, a 7T Forced Current Excited (FCE) bilateral breast coil, which can be electronically switched to unilateral excitation mode, was developed. The coil was designed to provide the large field-of-view needed for bilateral breast imaging, while allowing unilateral mode when higher excitation fields are needed. Extending the forced current approach to two Helmholtz pairs avoided any difficulties with mode splits due to coupling between the closely spaced coils. The coil was tested at a 7T scanner using phantoms, demonstrating highly effective mode switching and excellent homogeneity.

Samantha By¹, Joseph Rispoli¹, Jiaming Cui², Sergey Cheshkov^3,4, Ivan E. Dimitrov^3,5, Craig R. Malloy^3,4, Steve Wright^1,2, and Mary P. McDougall^1,2
1Biomedical Engineering, Texas A&M University, College Station, TX, United States, ²Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States, ³Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States, ⁴Radiology, University of Texas Southwestern Medical Center, Dallas, TX, United States, ⁵Philips Medical Systems, Cleveland, OH, United States

B1 inhomogeneities associated with high fields make effective imaging and hardware design challenging. "Forced current excitation" (FCE) provides homogeneous excitation and ease of tuning, irrespective of asymmetric loading, but the necessary incorporation of transmission line lengths in the resonant structure decreases SNR. This work presents the combined use of a FCE transmit breast coil with a 16-channel receive array insert to increase the receive sensitivity while taking advantage of the benefits of FCE during transmission. Breast imaging results indicate an improvement in SNR of up to six times from the insert as compared to the FCE coil in T/R mode.

Michel Italiaander¹, Ingmar Voogt¹, Irene van Kalleveen¹, Bertine L. Stehouwer¹, Tijl van der Velde¹, Peter R. Luijten¹, Vincent Oltman Boer², and Dennis W.J. Klomp^1
1UMC Utrecht, Utrecht, Utrecht, Netherlands, ²University Medical Center Utrecht, Utrecht, Utrecht, Netherlands

In the detection of breast cancer strong T1 weighting in contrast-enhanced MRI is essential, requiring a high density of strong flip angles, that generally will be limited due to SAR constrains particularly at 7 Tesla. Therefore we propose the use of efficient quadrature surface arrays to maximize contrast-enhanced MRI efficiency at 7 Tesla in the breast (bilateral). With B1 compensating RF pulses in one dimension and B1 shimming in the second dimension uniform flip angles can be obtained. Combined with 30 receivers, we demonstrate uniform and strong T1 weighting in a volunteer and in a patient with breast cancer.

Francesca Galassi¹, John McGinley¹, Mihailo Ristic¹, Nandita M. deSouza², and Djordje Brujic^1
1Imperial College, London, UK, United Kingdom, ²Institute of Cancer Research, The Royal Marsden Hospital, London, UK, United Kingdom

MRI Transrectal prostate biopsy requires updating of the targeted lesions while tracking the biopsy needle. Reliable tracking and fast, high resolution imaging require an optimized receiver. A novel external receive coil was designed to ensure higher signal from the prostate and from markers placed into a probe. The design was based on volunteer subjects and optimised for use with an MRI compatible manipulator. The sensitivity of the coil and the RF field homogeneity were evaluated. The results indicated significant improvements in sensitivity over the region of interest, with consequent improvements in needle tracking and imaging of the targets.

Mark Schuppert¹, Boris Keil², Bastien Guérin², Stefan Fischer¹, Laura Maria Schreiber¹, and Lawrence L. Wald^2,3
1Section of Medical Physics, Department of Diagnostic and Interventional Radiology, Johannes Gutenberg University Medical Center, Mainz, Germany, ²Department of Radiology, A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ³Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, United States

We analyze several different geometrical arrangements of coil elements in a 64-channel phased-array cardiac coil for optimized SNR and g-factor values in the heart using magnetic field simulations (Biot-Savart law). The final coil pattern comprises 40 coil elements on the chest and 24 coil elements on the back each exhibiting a diameter of 75mm. Lateral arrangement of coil elements wrapping around the body is important and results in a homogeneous SNR distribution and low g-factor values in the heart simultaneously.

Haoqin Zhu¹, Mehran Fallah-Rad¹, and Labros Petropoulos^1
1R&D, IMRIS Inc, Winnipeg, MB, Canada

A novel wireless endorectal phased array coil design was presented. It has shown that this coil can greatly improve image quality in terms of SNR and signal penetration on the prostate gland by 7.5 fold in average with the combination of both wireless endorectal coil and 8 channel flex phased array coil. When compared with an external cabled 8 channel flex phased array coil only. In addition to the SNR improvements, the wireless phased array endorectal coil design is lightweight, enhances patient comfort and set up workflow and can be made to be a disposable device. Besides the significant improvement in SNR, the proposed phased array design of the coil provides significant coverage over the prostate gland.

Iain P. Bruce¹, L. Tugan Muftuler^2,3, and Daniel B. Rowe^1,2
1Department of Mathematics, Statistics, and Computer Science, Marquette University, Milwaukee, Wisconsin, United States, ²Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States, ³Department of Neurosurgery, Medical College of Wisonsin, Milwaukee, Wisconsin, United States

In fcMRI, a significant dependence is placed on developing models and processing operations to rid the acquired data of artifacts at the neglected expense of altering the statistical properties of the acquired data. The alleviation of artifacts at a fundamental level, when the data is first acquired, would provide an appreciable advantage for specific fcMRI studies. Optimal RF coil designs can be achieved by minimizing a cost function in which both the g-factor is reduced to lower the amplification of coil related noise in a ROI, and the correlation induced by SENSE reconstruction is minimized to avoid type-I&II errors.

Gregor Adriany¹, Scott Schillak², Matt Waks², Brandon Tramm², Alard Roebroeck³, Elia Formisano³, Federico DeMartino³, Essa S. Yacoub¹, and University of Minnesota University of Minnesota Vaughan^1,2
1Center for MR Research, University of Minnesota, Minneapolis, MN, United States, ²Life Services LLC, Minneapolis, MN, United States, ³Maastricht University, Maastricht, Netherlands

A dedicated 7 Tesla coil array for bilateral high-resolution fMRI of the temporal lobe is presented. 4 transceiver and 12 receiver-only loop coils were realized within a slim FDM molded housing. Excellent decoupling between the transceiver and receiver arrays was achieved allowing for on coil preamplifiers.

Shinya Handa¹, Matthew Finnerty¹, Craig I. Lawrie¹, Tsinghua Zheng¹, Xiaoyu Yang¹, Joseph Herczak¹, Hiroyuki Fujita^1,2, John A. Carrino³, Filippo Del Grande³, Guarav K. Thawait³, and Sahar J. Farahani^3
1Quality Electrodynamics, Mayfield Village, Ohio, United States, ²Department of Physics, Case Western Reserve University, Cleveland, Ohio, United States, ³Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University, Baltimore, Maryland, United States

A transmit and 16 channel receive array coil for hand/wrist imaging at 3.0 Tesla was constructed and tested. The coil consists of an elliptical 8 rung birdcage coil for transmitting and an array of 16 independent loops for receiving. Initial phantom and volunteer imaging results demonstrated that the coil had excellent image quality, coverage of FOV, and required significantly less transmit power than an existing receive only coil.

Nabraj Sapkota^1,2, Josh Kaggie^1,2, J. Rock Hadley², and Eun-Kee Jeong^2,3
1Dept. of Physics and Astronomy, University of Utah, Salt Lake City, Utah, United States, ²Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, United States, ³Dept. of Radiology, University of Utah, Salt Lake City, Utah, United States

In this work, a Cervical Spinal Cord (CSC)-dedicated 8-channel phased array coil is developed with its layout and the dimension optimized using computer simulation. The performance of phased array coil depends on its shape, size and number of elements. The sensitivity of a phased array coil depends on the magnetic field of the coil perpendicular to the static magnetic field. The magnitude and direction of the RF magnetic field (B1) in 3-dimensional space is calculated using the Bio-Savart’s law and the shape and size of the surface coil is optimized. MRI experiments are performed to confirm the numerical simulation.

Graham C. Wiggins¹, Bei Zhang¹, Martijn A. Cloos², Riccardo Lattanzi¹, Gang Chen¹, Karthik Lakshmanan¹, Gillian Haemer¹, and Daniel Sodickson^1
1Center for Biomedical Imaging, NYU Medical Center, New York, NY, United States, ²Center for Biomedical Imaging, New York University School of Medicine, New York, NY, United States

Analysis of the ideal current patterns corresponding to the Ultimate Intrinsic SNR show that for large objects at high field there can be a substantial contribution from electric dipole-like currents. For a body sized cylindrical phantom at 7T the Ultimate Intrinsic SNR for the center of the object is 23% higher for electric dipole-like (curl free) currents compared to loop-only (divergence free) currents, and is 54% higher if a combination of current patterns is allowed. Lesser but still substantial benefits are demonstrated in both simulation and experiment in a coil design combining loops and electric dipoles.

Natalia Gudino¹ and Mark A. Griswold^1,2
1Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, ²Department of Radiology, Case Western Reserve University, Cleveland, OH, United States

A multi-turn transmit surface coil design is presented to improve B1 efficiency when driven by on-coil current source amplification. Benchtop and 1.5 T MRI experiments showed a three-fold increase in B1 at same amplifier output current and without increasing heat dissipation in the amplifier. This gain in B1 allowed the use of lower power rated FETs that present lower port capacitances which could improve the overall performance of the on-coil current source transmitter and its multiple-channel implementation.

Hoby P. Hetherington¹, Nikolai I. Avdievich¹, and Jullie Pan^1
1Neurosurgery, Yale University, New Haven, CT, United States

At 7T, decreasing T2, T2* and increasing SAR and T1 can limit the number of slices acquired or acquisition time. RF multiplexing enables coil dense transceiver arrays (more coils than independent RF channels) to be used; which improves SNR (more optimal coil size and number) and B1 homogeneity and coverage. RF multiplexing inherently generates simultaneous multiple bands of excitation for slice selective pulses. The aliasing generated by the multiple bands of excitation can be removed by deconvolution with the receiver sensitivity matrix to regenerate three independent slices, thereby reducing SAR and increasing imaging speed by acquiring three slices per excitation.

Yigitcan Eryaman^1,2, Bastien Guérin³, Elfar Adalsteinsson^4,5, and Lawrence L. Wald^2,5
1Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, United States, ²Martinos Center for Biomedical Imaging, Dept. of Radiology, MGH, Charlestown, MA, United States, ³Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ⁴Dept. of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, ⁵Harvard-MIT Health Sciences and Technology, Cambridge, MA, United States

We calculated a lower bound for peak 10 g local SAR that can be obtained with an arbitrary transmit coil in a uniform cylindrical phantom. For that purpose we used cylindrical basis expansion to express an arbitrary EM field in the phantom. Then the optimum least square RF shimming or pTx pulse solutions are calculated for the cylindrical modes with an explicit constraint to minimize local SAR. To make this optimization computationally possible the local SAR matrices are compressed using the VOP method. The result is the trade-off (L-curve) between the excitation fidelity and the lowest possible local SAR afforded by an arbitrary transmit array. The ultimate L-curves can be used as a figure of merit for the SAR performance of modeled or constructed pTx coils.

Bastien Guérin¹, Matthias Gebhardt², Peter Serano¹, Elfar Adalsteinsson³, Michael Hamm², Josef Pfeuffer², Juergen Nistler², and Lawrence L. Wald^1
1Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ²Siemens Healthcare, Erlangen, Germany, ³Electrical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States

Little theoretical work has been done optimizing pTx array geometries and number of Tx channels. We simulate eight 3T body pTx arrays with varying number and distribution of Tx channels. We design transverse and coronal RF shimming and 2-spoke pulses subject to local SAR constraint. We show that adding Tx channels improves the local SAR vs. fidelity tradeoff however at the cost of increased power. For arrays with at least 8 Tx channels per row, it is beneficial to add channels in the z-direction as opposed to only in the transverse direction, especially for imaging in the coronal orientation.

Giorgos Katsikatsos¹ and Klaas P. Pruessmann^1
1Institute for Biomedical Engineering, Zurich, ZH, Switzerland

A closed-loop controlled matching for Tx-arrays in ultra-high field has been implemented as an autonomous system to react to load changes in various stages of an MR experiment. Building blocks of the system are the L-matching networks, built from custom low-loss capacitors actuated by piezoelectric motors and controlled by an external computer. The feedback is provided by a network analyzer which triggers the re-matching procedure. The matching algorithm is based on previous knowledge about the matching circuit connected to the array and uses common objective functions to detect the best matching settings for arbitrary loads.

Graeme A. Keith¹, Christopher T. Rodgers¹, Aaron T. Hess¹, Carl J. Snyder², University of Minnesota University of Minnesota Vaughan², and Matthew D. Robson^1
1Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, Oxfordshire, United Kingdom, ²Center for Magnetic Resonance Research, Minneapolis, MN, United States

A novel method for tuning and matching an eight channel cardiac RF array for parallel transmit at 7 Tesla is presented. Piezoelectric stepping motors were used to allow automation of the process and remove the need for tuning by hand. S₁₁ profiles for each channel were gathered showing the ratio between reflected and forward power across all of 2-D tune/match space. For both a phantom and in vivo these plots show a clear peak where the maximum S₁₁ occurs. Auto-tuning at 7T was used in vivo to quickly and effectively to maximise the B₁⁺.

Neal Hollingsworth¹, Katherine Moody², Jon-Fredrik Nielsen³, Douglas C. Noll³, William A. Grissom⁴, and Steven Wright^1
1Electrical Engineering, Texas A&M University, College Station, TX, United States, ²Biomedical Engineering, Texas A&M University, College Station, TX, United States,³Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States, ⁴Biomedical Engineering, Vanderbilt University, Nashville, TN, United States

Parallel transmit allows for acceleration of spatially selective RF pulses using multiple, independently modulated channels. We have developed an improved, stand alone, multichannel vector modulation system to support work with multi-dimensional RF transmit pulses. The modulators are integrated with an existing MRI system by connecting the RF input to the power amplifier and a digital trigger to them. Scaling to high channel counts is straight forward due to a modular design. Further, they can be used with systems at virtually all field strengths by replacing a simple filter located on a daughter board.

Aaron T. Hess¹, Carl J. Snyder², Graeme A. Keith³, Christopher T. Rodgers³, Stefan Neubauer³, University of Minnesota University of Minnesota Vaughan⁴, and Matthew D. Robson^3
1University of Oxford, Oxford, Oxon, United Kingdom, ²University of Minnesota - Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ³University of Oxford Centre for Clinical Magnetic Resonance Research, Oxford, Oxon, United Kingdom, ⁴University of Minnesota - Center for Magnetic Resonance Research, Minneapolis, MN, United States

The effectiveness of using MRI signal from turbo flash images to tune and match a four element transmit receive transverse electromagnetic (TEM) coil is assessed. The complete range of the tune and match capacitors is assessed over a 30x32 grid using piezoelectric controlled actuators. The measure was repeated in four coil elements in a phantom and two subjects. The maximum MRI signal fell within -10 dB reflected/forward power (S₁₁) for the four elements. We conclude that MRI is a suitable metric for tuning and matching a TEM coil but less sensitive around the optimum than the S₁₁ metric.

Jinfeng Tian¹, Lance DelaBarre¹, John Strupp¹, Jay Zhang², Josef Pfeuffer³, Michael Hamm³, Juergen Nistler³, Kamil Ugurbil¹, and University of Minnesota University of Minnesota Vaughan^1
1Center for Magnetic Resonance, University of Minnesota, Minneapolis, Minnesota, United States, ²Cardiology, University of Minnesota, Minneapolis, Minnesota, United States,³Siemens Healthcare, Erlangen, Germany

Short RF wavelengths in high field MRI result in less homogeneous |B1+| field and severe SAR gradients in body. To investigate possible solutions, B1 and SAR contours were calculated for ten different 3T whole-body coils. Referenced to a high-pass birdcage body coil, new design permutations included multi-channeled TEM and loop arrays with elements distributed in x, y, and z. RF fields were configured by circular polarization and by B1 shimming. Results showed all arrays with B1 shimming could greatly improve the RF homogeneity while the TEM 2x8 array provides optimal performance based on |B1+| homogeneity, peak SAR and power efficiency.

Andreas Graessl¹, Michael Schwerter¹, Maximilian Muhle¹, Jan Rieger^1,2, Celal Oezerdem¹, Abdullah Ok¹, Davide Santoro¹, Darius Lysiak^1,2, Oliver Stachs³, Soenke Langner⁴, Paul-Christian Krueger⁴, and Thoralf Niendorf^1,5
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck-Center for Molecular Medicine, Berlin, Germany, ²MRI.TOOLS GmbH, Berlin, Germany, ³Department of Ophthalmology, University of Rostock, Rostock, Germany, ⁴Institute for Diagnostic Radiology and Neuroradiology, University of Greifswald, Greifswald, Germany, ⁵Experimental and Clinical Research Center, Berlin, Germany

In vivo imaging of the spatial arrangement of eye segments and their masses is an emerging MRI application and ultimately aims at performing MR image-based biometry. For this purpose, a six-element transceiver eye coil array (f=298 MHz) which uses loop elements is proposed. Our EMF simulations and experimental results indicate that the use of multiple surface coil transceiver loop elements yields an excellent SNR for eye imaging, affords uniform signal intensity across the eyes, and facilitates the depiction of anatomical details of the eye.

Christoph Leussler¹, Peter Vernickel¹, Christian Findeklee¹, Daniel Wirtz¹, Peter Börnert², and Kay Nehrke^1
1Philips Technologie GmbH, Hamburg, Germany, ²Philips Research Laboratory, Hamburg, Germany

A dual mode Tx/RX coil is presented. In a first mode, the coil acts as a receive only coil array in combination with the conventional transmit body coil. In the 2nd mode, the coil is used as local Tx/Rx array with the mentioned advantages. While in the first mode the required SENSE reference information is generated, this information is used to accelerate the acquisition of the B1+ maps based on the DREAM technique in the second mode. Using both modes sequentially, we obtain all information required for exact B1+ mapping and fast RF shimming.

Gillian Haemer¹, Martijn A. Cloos², and Graham Wiggins^1
1The Bernard and Irene Schwartz Center for Biomedical Imaging, NYU Medical Center, New York, NY, United States, ²The Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, NY, United States

We describe here an 8-channel Transmit-Receive (TxRx) array, consisting of 8 loop elements, placed with dodecahedral symmetry at a safe distance from the average human head. The design was modeled after a previously proposed coil (ref) which was designed to allow for full brain coverage as well as variation along all three directions, x, y, and z. It has been modified here to better fit around the head and to balance all areas of each element at a precise distance from the subject.

Yoshihisa Soutome¹, Yosuke Otake¹, Masayoshi Dohata¹, Hisaaki Ochi¹, and Yoshitaka Bito^1
1Central Research Laboratory, Hitachi Ltd., Kukubunji, Tokyo, Japan

We have designed a 4-channel body coil with ladder-shaped coils and demonstrated its characteristics at 3T using numerical simulations. The designed coil can increase bore size in the right-left and anterior-posterior directions because of the increase in space between nearest neighbor coils. The designed ladder-shaped coils were decoupled from each other very well. The designed body coil also showed good B₁ uniformity of 7.6% in the region-of interest of 40 cm and the same transmission efficiency as the birdcage coil in the loaded condition. Simulation results suggest that the designed coil can be used as a multi-channel transmit body coil

Ed B. Boskamp¹, Masahiro Fujimoto¹, and Michael Edwards^1
1GE Healthcare, Waukesha, WI, United States

In MRI systems, receive coil connectors are part of the patient cradle for easy access. The patient cradle and coil cables travel through the bore of the system, and thus through the RF body coil. The electric fields generated by the body coil induce voltages and currents in the shielding of this cable bundle. These common mode currents are usually stopped by applying baluns on the cable shield. This research investigates coil symmetry perturbation due to the presence and motion of the cable and baluns. FEM simulation and lab measurements were performed to study the effect.

Joseph Vincent Rispoli¹, Samantha By¹, and Mary P. McDougall^1,2
1Biomedical Engineering, Texas A&M University, College Station, Texas, United States, ²Electrical & Computer Engineering, Texas A&M University, College Station, Texas, United States

The need for RF shields increases with increasing field strengths in regards to handling patient safety concerns and optimizing coil stability. Through electromagnetic modeling and bench measurements, this work presents design guidelines for co-planar RF shields to reduce specific absorption rate while maintaining effective B1.

Steven M. Wright¹, Ivan E. Dimitrov^2,3, Sergey Cheshkov², Mary P. McDougall⁴, and Craig R. Malloy^2
1Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States, ²Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States, ³Philips Medical Systems, Cleveland, OH, United States, ⁴Biomedical Engineering, Texas A&M University, College Station, TX, United States

In addition to B1 homogeneity, searching for the most efficient (true quadrature) B1+ is desirable for a number of applications, especially those that require high power, e.g. proton decoupled spectroscopy. This abstract discusses a simple method for calibration of the drive phases in a two channel transmit system. Setting the phases for reverse circular polarization (anti-quad) provides greater sensitivity for the validation of the phase calibration for ‘steering’ to a point of interest. In addition to its general applicability for coil calibration, this method may find application in steering the zero effective field needed for catheter-tracking based on reverse polarization.

Karthik Lakshmanan¹, Martijn A. Cloos², Graham C. Wiggins¹, and Ryan Brown^1
1NYU, Newyork, Newyork, United States, ²New York University School of Medicine, Newyork, Newyork, United States

Circularly polarized volume coils have been for B1 excitation in head imaging at 7.0 Tesla. However the excitation in head apex produced by CP Volume coil is usually poor. In this work we improved the excitation in Head Apex by combining a crossed dipole Antenna pair with a Birdcage coil. With this setup we were also able to manipulate the excitation pattern in the center of the Head.

Debra S. Rivera^1,2 and Turner Robert^2
1Univercity Medical Center, Utrecht, Netherlands, ²Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany

For transmit elements, mismatch in phase or amplitude of signal delivered to the two sides of a coil element cause common-mode current losses. Using 3-port mixed-mode scattering parameters, the authors compare common-mode rejection (CMR) and insertion loss (IL) of lattice and wire-wound baluns. Transmit efficiency of the different baluns, and a through were compared for a 7T head transmit array. All baluns were tuned to CMR <-20 dB, and provided >20% improbed power efficiency, indicating the severity of common-mode losses for 7T. Transmit efficiency correlated with IL, favoring wire-wound baluns.

Yukio Kaneko¹, Yoshihisa Soutome¹, Hideta Habara¹, and Yoshitaka Bito^2
1Hitachi Ltd., Central Research Laboratory, Kokubunji, Tokyo, Japan, ²Hitachi Ltd., Hitachi, Ltd., Kokubunji, Tokyo, Japan

The B1 inhomogeneity in a human body increases as the strength of a static magnetic field increases. Previous studies showed the effect of the number of RF transmit channels in RF shimming for the entire region of the torso. However, the effect for a partial region of the torso in 3T has not yet been investigated. In this study, numerical simulation has been used to investigate the effect of the number of RF transmit channels for regional RF shimming in the torso region in 3T. The results show that 4-channel and 8-channel RF shimming can contribute to improving the B1 inhomogeneity in a partial region.

Debra S. Rivera^1,2, Thomas Siegert³, Carsten Koegler^2,4, Andreas Schaefer², Markus Nikola Streicher³, and Robert Turner^2
1Univercity Medical Center, Utrecht, Netherlands, ²Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany, ³Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany, ⁴RAPID Biomedical, Rimpar, Germany

The authors present a 7T head transmit array made of interlocking printed circuit boards (PCBs). The two-stage prototyping process, focused on minimizing radiation losses and coil asymmetries. A transparent mesh shield was used which suppresses eddy-currents and allows line-of-sight to the region of interest. Data was collected with a cylindrical phantom for the hand-built prototype, and for the PCB array with two different shields. The greatest symmetry and power transmitted to the phantom was observed for the PCB array with the transparent shield. Anatomical phantom or brain data is projected to be available for the conference.

Jinfeng Tian¹, Devashish Shrivastava¹, Gregor Adriany¹, John Strupp¹, Scott Schillak², Jay Zhang³, Kamil Ugurbil¹, and University of Minnesota University of Minnesota Vaughan^1
1Center for Magnetic Resonance, University of Minnesota, Minneapolis, Minnesota, United States, ²Virtumed, LLC, Minneapolis, Minnesota, United States, ³Cardiology, University of Minnesota, Minneapolis, Minnesota, United States

Previous research has demonstrated feasibility of 3D RF arrays in mitigating RF inhomogeneities for ultra-high field MRI applications. Three RF coil designs were simulated to investigate their relative |B1+| and SAR performance in 7T whole-head MRI. A 16-ch 2D TEM reference coil was compared to a 30-channel, 3D TEM array, and a 32 channel, 3D loop array. All coils were circularly polarized in this initial study by numerical simulation. The 3D loop array exhibited a higher |B1+| on the central trans-axial slice, together with higher mean SAR on all three central slices, and higher peak 1gram and 10gram SAR across the whole head. Advantages of these 3D arrays will be further explored through B1+ shimming models.

Stephan Orzada^1,2, Stefan Maderwald¹, Sören Johst^1,2, Andreas K. Bitz^1,2, Klaus Solbach³, and Mark E. Ladd^1,2
1Erwin L. Hahn Institute for MRI, Essen, NRW, Germany, ²Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, NRW, Germany, ³High Frequency Engineering, Department of Electrical Engineering, University of Duisburg-Essen, Duisburg, NRW, Germany

In today’s high-field systems, severe problems regarding the homogeneity of the transmission field are encountered. Most of the methods proposed to tackle these problems are multichannel methods. Recently, Time-Interleaved Acquisition of Modes (TIAMO) has been proposed to cope with B1 inhomogeneity in ultra-high-field imaging. In this work we present a simple and inexpensive hardware setup which makes it possible to use TIAMO on any single-channel Tx system while making use of the vendor-provided single-channel RF safety system. We show that with this setup 7 Tesla spin echo imaging of the pelvis is possible without severe signal dropouts.

Wolfgang Loew¹, Jean A. Tkach¹, Ronald G. Pratt¹, Barret R. Daniels¹, Randy O. Giaquinto¹, Stephanie L. Merhar¹, Beth M. Kline-Fath¹, Kim M. Cecil¹, and Charles L. Dumoulin^2
1Imaging Research Center, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, United States, ²Imaging Research Center, Cincinnati Children's Hospital, Cincinnati, Ohio, United States

In this abstract we present the development of a dedicated 1.5T neonatal MR system for Neonate Intensive Care Units (NICUs). This novel system utilizes a small footprint magnet with advanced imaging capabilities and a dedicated patient handling system. A systems overview is given including the workflow of the patient handling. Clinical relevant spectroscopy scans and an in-vivo imaging scan were acquired on neonates.

Yasuhiko Terada¹, Kazunori Ishizawa¹, Shinya Inamura¹, and Katsumi Kose^1
1Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan

A portable wrist MRI system for skeletal age assessment without special RF shielding was developed. The system consisted of a small 0.3 T permanent magnet of 135 kg weight, which is readily portable and can be placed anywhere. Despite the small magnet gap (8 cm), the B0 and B1 homogeneities and the gradient nonlinearity were high over 8 cm × 8 cm × 4 cm diameter ellipsoidal volume. The portable system provided wrist images with high quality that are as reliable as those provided by a compact hand MRI system with a 0.3 T permanent magnet of 700 kg weight.

Mikayel Dabaghyan¹, Eric Frederick², Iga Muradyan^3,4, Alan Hrovat¹, Michael Hrovat¹, Samuel Patz^3,4, and Mirko I. Hrovat^1
1Mirtech Inc., Brockton, MA, United States, ²Physics, University of Massachusetts, Lowel, Lowell, MA, United States, ³Radiology, Brigham and Women's Hospital, Boston, MA, United States, ⁴Harvard Medical School, Boston, MA, United States

Here we describe a system of monohedral permanent magnets that make up a part of a device for uni-lateral portable NMR. The magnets generate a focused region with a uniform magnetic field, located several centimeters above the surface of the magnet. The surface of the magnet is placed on the posterior portion of the chest allowing the homogeneous field region to be located inside the lung. The device can measure a proton signal, as well as that of hyperpolarized Xe, in order to measure lung density and ventilation respectively.

Karen J. Mullinger¹, Muhammad E.H. Chowdhury¹, and Richard W. Bowtell^1
1SPMMRC, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom

EEG data recorded simultaneously with fMRI acquisition are contaminated by large voltages generated by the time-varying magnetic field gradients. Previous work suggested changing the EEG cap lead layout and cable bundle position could reduce the gradient artefact (GA). Here, through simulations and experiments, we show that a reduction of the GA can be achieved through the suggested modifications. Using a modified cap, we experimentally demonstrate significant reduction in the GA amplitude over the temple regions using a standard EPI sequence. Different lead configurations could be explored to minimise the GA for other electrodes depending on the cortical areas of interest.

Sara Assecondi^1,2, Paolo Ferrari¹, and Jorge Jovicich^1
1Functional Neuroimaging Laboratory, Center for Mind/Brain Sciences (CIMeC), University of Trento, Trento, Italy, ²School of Psychology, University of Birmingham, Birmingham, United Kingdom

We describe the setup for simultaneous EEG-fMRI experiments used in our institution with a 4T MR-scanner. In our laboratory a compact setup was devised, in which the EEG cables are shortened and the amplifiers placed closer to the MR (RX/TX) coil and stabilised on a wooden form-fitting extension moving with the MR-bed. We found that a careful design of the EEG-fMRI workplace, tailored to the laboratory-specific needs, not only improves the quality of EEG data during simultaneous EEG-fMRI, but might also have an impact on important aspects such as safety, ergonomics and reproducibility of the setup across sessions and laboratories.

Karl-Heinz Herrmann¹, Norman Pfeiffer^1,2, Ines Krumbein¹, Lutz Herrmann², and Jürgen R. Reichenbach^1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany, ²Ernst-Abbe-Fachhochschule Jena, Jena, Germany

A cost efficient system to acquire a respiratory and cardiac monitoring signal for small animals like mice and rats is presented. The motion detection is based on a small pressure pad and the signal is converted and processed by an analog amplifier and filter circuit. The output in the range of Volts allows any kind of further visualization or sophisticated post-processing in hard- or software. Exemplarily the improved image quality of T2 weighted MR images are shown using the generated respiratory trigger in comparison to the untriggered images.

Christos Bergeles¹, Panagiotis Vartholomeos¹, Lei Qin², and Pierre E. Dupont^1
1Boston Childrens Hospital, Harvard Medical School, Boston, MA, United States, ²Dana-Farber Cancer Research, Harvard Medical School, Boston, MA, United States

MRI-powered motors may allow the design of interventional medical robots that are powered, imaged, and control by MRI-scanners. Closed-loop control of an MRI-powered motor is necessary for maximum energy transfer and stability. This abstract presents a real-time tracking methodology based on RF-selective excitation that allows closed-loop control of an MRI-powered motor.

In-Tsang Lin¹, Hong-Chang Yang², and Jyh-Horng Chen^3
1Interdisciplinary MRI/MRS Lab, Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, ²Department of Physics, National Taiwan University, Taipei, Taiwan, ³National Taiwan University, Taipei, Taiwan

In this work, a compact temperature-stable high temperature superconducting (HTS) cryo-system for keeping animal rectal temperature at 37.4 ºC for more than 3 hours was successfully implemented. The proton resonant frequency (PRF) method was used to monitor the frozen effect. The signal-to-noise ratio (SNR) of the HTS surface coil at 77 K is higher than that of a professionally-made copper coil at 300 K with the same geometry and the SNR gain is 3.79 folds.

John Arthur Benson Mates¹, Michael A. Boss¹, Hsiao Mei Cho¹, Gene C. Hilton¹, and Kent D. Irwin^1
1National Institute of Standards and Technology, Boulder, CO, United States

We constructed phantoms for the characterization of ultra-low field (~100 uT) MRI systems and measured them at 132 uT, 1.5 T, and 3 T. The phantoms permit characterization of resolution, PD accuracy, and T1 accuracy. The phantoms can serve as common references and guide ultra-low field scanner development.

Michael A. Martens¹, Tanvir Baig¹, Mihai Cara¹, Robert W. Brown¹, David Doll², and Michael Tomsic^2
1Case Western Reserve University, Cleveland, OH, United States, ²Hyper Tech, Columbus, OH, United States

Superconducting MRI magnets are dominantly made with NbTi wire cooled below 4.2K using liquid helium. As helium costs have more than tripled in the last decade, there is a need for a cryogen-free conduction-cooled alternative. A key reason for pursuing MgB2 superconductor wire in the design of MRI magnets is its superior critical current compared to NbTi over a temperature range of 10-15K. We present a 3T whole body actively shielded main magnet design assuming second-generation multifilament MgB2 wire using an improved functional approach. Trade-offs for the reduction of any given parameter are analyzed.

Zhenyu Zhang¹ and Weijun Shen^1
1GE Healthcare, Florence, South Carolina, United States

A major constrain of MRI superconducting magnet design is the cost and it becomes increasingly important given the dynamics in global market. Shimming system, an essential subsystem in MRI magnets, is one of the areas where constant efforts have been put down to make it more cost-effective. In this paper, a novel magnet coil design scheme, which minimizes B0 inhomogeneity through micro-adjustments of main coil currents, is presented. This design could substantially reduce system cost in comparison to traditional designs such as a set of standalone shimming coils.

Daiki Tamada^1,2, Takashi Nakamura^1,2, and Katsumi Kose^1,2
1Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan, ²RIKEN, Wako, Saitama, Japan

A high critical temperature superconducting bulk magnet is a novel magnet for magnetic resonance imaging which has the advantage of its compactness. However, it is a difficult to achieve a homogeneous magnetic field sufficient for MRI because of the complicated magnetization process. In this study, we clarified the magnetization process by measuring the magnetic field distribution of the bulk magnet using a phase method based on 3D spin echo sequences.

Cristen D. LaPierre^1,2, Mathieu Sarracanie^1,2, Lawrence L. Wald^1,3, and Matthew S. Rosen^1,2
1Department of Radiology, Mass General Hosptial, A.A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, ²Department of Physics, Harvard University, Cambridge, MA, United States, ³Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, United States

Parallel imaging in the Johnson noise dominated regime is a new regime; optimal parameters are not available in the literature. In this study, an eight-coil receive only array for 6.5 mT was constructed and SENSE was used to accelerate images. An 8 channel receive only array was constructed from 8 cm, 30 turn, 24 gage wire inductive coils. The correlation coefficient matrix was almost the identity matrix. SENSE with a reduction factor of 2 was simulated and then acquired and images were successfully reconstructed. Future work will attempt higher reduction factors and combine SENSE with random undersampling.

Myung-Kyun Woo¹, Randall B. Stafford², Suk-Min Hong¹, Se-Hong Oh², Young-Bo Kim¹, Jongho Lee², and Zang-Hee Cho^1
1Neuroscience Research Institute, Incheon, Korea, ²Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States

Arterial Spin Labeling (ASL) at ultra-high field benefits from increased spin polarization and blood T1 and has potential to improve perfusion maps. However, one needs to overcome the challenges of increased specific absorption rate (SAR), B0 and B1 inhomogeneity. Particularly, SAR is an important hurdle for continuous or pseudo-continuous ASL due to the use of long RF labeling. To address this challenge, we have developed a new RF coil system that has separate labeling coils. This approach allows us to reduce SAR by removing RF for the control condition.

Dasong Zhu¹, Yuki Mori¹, and Yoshichika Yoshioka^1
1Biofunctional Imaging Lab, Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan

MRI is playing an increasingly important role in the evaluation of cardiovascular disease. How to improve signal-to-noise rate (SNR) of cardiac imaging is one of the important factors for cardiovascular research. Usually Transmit/receive arrays are used in the 1.5T, 3T and 7T MRI for decreasing RF inhomogeneities and increasing SNR. Strengthening the effect of transmitting radio frequent(RF) can improve SNR under the ruled specific absorption rate(SAR). In this work, a novel shield circuit is proposed to strengthen transmitting magnetic field(B1) and we got much higher SNR from our experiment results.

Gameel Saleh¹, Klaus Solbach¹, Daniel Erni², and Andreas Rennings^2
1High Frequency Technique (HFT), University of Duisburg-Essen, 47048, Duisburg, Germany, ²General and Theoretical Electrical Engineering (ATE), University of Duisburg-Essen, and CENIDE - Center for Nanointegration Duisburg-Essen, 47048, Duisburg, Germany

In this paper, a multilayer offset EBG structure is introduced as a high surface impedance ground plane to maximize the magnetic field intensity inside the phantom, by suppressing the anti-phase currents on the metallic ground plane. The proposed structure works as a Soft surface with higher surface impedance in the longitudinal direction (like a perfect magnetic conductor PMC), and lower surface impedance in the transversal direction (like a perfect electric conductor PEC). The MRI strip-line coil backed by our EBG structure is successful in exhibiting a stronger H/E field ratio (amounts to 58 %) inside the phantom than the original design using a (PEC) ground plane for the coil.

Kyle M. Gilbert¹, Matthew R. DiPrimio¹, Sarah Hughes¹, Kathryn Y. Manning¹, and Ravi S. Menon^1
1Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada

A 16-channel whole-brain receive coil and 7-channel local receive coil was developed for imaging non-human primates. This coil system will allow for high-resolution imaging of the peripheral cortex with the ability to co-register to a whole-brain image. Performance metrics of the two coil arrays are provided.

Anne-Laure Perrier¹, Jean-Christophe Goebel¹, Astrid Pinzano², Emilie Roeder², Pierre Gillet², Denis Grenier¹, and Olivier Beuf^3
1Creatis, Villeurbanne, France, ²PPIA, Vandoeuvre-les-Nancy, France, ³CREATIS, Villeurbanne, France

An equivalent electrical circuit of a four-channel NMR surface coil based on common conductor decoupling technique was proposed. The topology allowed good matching and good decoupling between elements without the use of additional low input impedance preamplifier and without additional capacitive network. The design of a four-channel surface coil with a particular wave-like topology for the simultaneous two rat knees imaging was realized at 300 MHz. The capacitor adjustments permit to obtain decoupling better than -17 dB between all element pairs. To our knowledge, this coil represents the first four-channel NMR surface coil based on common conductor not using the preamplifier decoupling technique. Performance of the coil was proved through the simultaneous HR-MRI of both knees joint of a rat. Voxel size of 49x49x98 µm3 was obtained for a 1h22min acquisition time.

Daniel Papoti¹, Cecil Chern-Chyi Yen¹, Julie Mackel¹, Hellmut Merkle¹, and Afonso C. Silva^1
1NINDS, NIH, Bethesda, Maryland, United States

We have previously devised a helmet restraint system to allow MRI/fMRI experiments of conscious, awake marmosets in a completely non-invasive and comfortable manner. The present work describes the development of a whole-brain 8-channel receive-only surface array for conscious, awake marmosets. Improved SNR is obtained by placing the coil elements on the inner surface of the helmet, to minimize the distance between the array elements and the cortical brain surface. The coil elements are built using flat and flexible conductors and are connected to low input impedance preamplifiers. Results show excellent brain coverage, good coil-to-coil isolation and high sensitivity.

Maximilian N. Voelker¹, Alexander M. Koenig¹, Steve Braun¹, Andreas H. Mahnken¹, and Johannes T. Heverhagen^2
1Diagnostic Radiology, Philipps University, Marburg, Hessen, Germany, ²University Institute of Diagnostic, Interventional and Pediatric Radiology, Inselspital, Bern University Hospital, Bern, Switzerland

A PIN-diode switched Birdcage coil for MRI on mice at 7T had been developed. PIN-diodes are used directly on the end rings of a high pass birdcage to add a second/parallel capacitor line to a 1H-tuned Birdcage coil. Therefore the resonance frequency can be changed between proton and phosphor frequencies. The intended usage is proton imaging and spectroscopy with phosphor spectroscopy as an Add-on. The coil is easy to match and tune and shows superior SNR to a 4-Ring-BC of similar size in proton imaging, but lower SNR on phosphor resonance mode.

Yu Li¹, Ewald Weber¹, Ivan Hughes¹, Stuart Crozier², Peter Ullmann³, Johannes Schneider³, and Sven Junge^3
1School of ITEE, The University of Queensland, Brisbane, Select, Australia, ²The University of Queensland, Brisbane, Select, Australia, ³Bruker BioSpin MRI GmbH Ettlingen Germany, Ettlingen, Germany

To benefit from the advantages of Parallel Excitation (PEX)/Transmit SENSE and Spatially Selective Excitation (SSE) imaging, a dedicated 9.4T phased-array for rat head MRI was developed. An 8-channel transceive array coil was modelled /simulated and a prototype was constructed and tested in a Bruker 9.4T Biospec MRI system. Preliminary experimental results presented herein demonstrate the potential of the work.

Eun-Kee Jeong^1,2, Nabraj Sapkota³, Joshua Kaggie³, and Xian-Feng Shi^4
1Radiology, University of Utah, Salt Lake City, UT, United States, ²Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, UT, United States, ³Dept. of Physics, University of Utah, Salt Lake City, UT, United States, ⁴Dept. of Psychiatry, University of Utah, Salt Lake City, UT, United States

This work presents a novel acquisition method that simultaneous measures both ³¹P and ¹H MR spectroscopies at the exactly same sampling window within the same acquisition, at a clinical MRI system that is equipped with a time-sharing second RF channel. The high frequency ¹H NMR signal is down-converted to the carrier ³¹P frequency, using additional RF components, which includes PIN-diode driven RF switches, preamplifier for ¹H frequency, a precision synthesizer, a mixer, and low-pass filter, and measured at one of the ³¹P receive channels. The residual water signal is used to identify and correct the phase-error on both ¹H and ³¹P spectra. Pulse sequence manipulates both spin systems within the same acquisition using time-shared RF transmission.

Elmar Laistler^1,2, Sigrun Goluch^1,2, Andre Kuehne^1,2, Martin Meyerspeer^1,2, Albrecht Ingo Schmid^1,2, Jürgen Sieg^1,2, Tim Herrmann³, Johannes Mallow³, Johannes Bernarding³, and Ewald Moser^1,2
1Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ²MR Centre of Excellence, Medical University of Vienna, Vienna, Austria,³Institut für Biometrie und Medizinische Informatik, Otto von Guericke University, Magdeburg, Germany

We show first results with an 3ch 31P/2ch 1H RF coil providing both increased sensitivity and an enlarged sensitive volume, as compared to commonly available single surface coils. Together with the higher transverse magnetization available at 7T, this will enable measurements of muscle metabolism in the human calf with unprecedented accuracy.

Seunghoon Ha¹, Harry Friel², Marijn Kruiskamp³, and Orhan Nalcioglu^1,4
1Tu & Yuen Center for Functional Onco-Imaging, University of California Irvine, Irvine, California, United States, ²Philips Healthcare, Highland Heights, Ohio, United States, ³Philips Healthcare, Best, Netherlands, ⁴Department of Cogno-Mechatronics Engineering, Pusan National University, Pusan, Korea

The common scheme of using trap circuits for dual-tuned operation results in increased coil losses as well as problems in obtaining optimal tuning and matching at both frequencies. Against these reserved problems, the duel tuned RF coil combined with strip-line coils array and a birdcage coil has proven their performance at 7T. However, a loop coil generates more uniformed B1- field and has better coil sensitivity than a strip-line coil at 3T. In the study, we construct the dual coil combined with a H1 loop coils array and a Na23 birdcage coil as well as evaluate decoupling methods to solve inter loop coupling.

Jing-Huei Lee¹, Mathew Norris¹, Elizabeth M. Fugate¹, Nikolai I. Avdievich², and Hoby P. Hetherington^2
1University of Cincinnati, Cincinnati, OH, United States, ²Yale University, New Haven, CT, United States

The development and implementation of the CMRO₂ imaging approach based on high-field ¹⁷O magnetic resonance spectroscopic (MRS) imaging, combined with brief inhalation of¹⁷O-isotope-enriched oxygen gas, has received increased interest. However, the low sensitivity of ¹⁷O MR signal has limited the potential of this technique. In this work, we introduced a novel double tuned ¹H/¹⁷O head volume coil, in which the ¹H coil is driven in quadrature mode and the ¹⁷O coil utilizes phased array approach.

Xiaoyu Yang¹, Shinya Handa¹, Tsinghua Zheng¹, Craig I. Lawrie¹, Matthew Finnerty¹, Joseph Herczak¹, Hiroyuki Fujita^1,2, Wolfgang Bogner^3,4, Olgica Zaric³, Stefan Zbýn³, and Siegfried Trattnig^3
1Quality Electrodynamics, Mayfield Village, OH, United States, ²Physics, Case Western Reserve University, Cleveland, OH, United States, ³Department of Radiology, Medical University Vienna, Vienna, Austria, ⁴Department of Radiology, Harvard Medical School, Boston, ma, United States

A Dual-Tune Sodium/Proton Tx/Rx 14-channel Sodium and 2-channel Proton Array Breast Coil at 7T was constructed and tested. The coil was built using nested approach without using lossy traps or PIN diodes. The coil has a three-layer structure. Initial volunteer imaging results demonstrated that the coil had promising image quality on both sodium and proton.

Sigrun Goluch^1,2, André Kühne^1,2, Ewald Moser^1,2, and Elmar Laistler^1,2
1Center of Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ²MR Centre of Excellence, Medical University of Vienna, Vienna, Austria

NMR spectroscopy benefits from higher sensitivity, increased spectral resolution and shorter relaxation times at 7T. To gain sensitivity it is common practice to use phased arrays. This technique leads to mutual coupling between array elements. In this work we compare three different decoupling schemes for a three channel 31P array using 3D electromagnetic simulation.

Hai Lu¹, Xiaotong Sun¹, Yu Shao¹, Nouha Salibi², Bernd Stoeckel², Thomas Stewart Denney Jr.¹, Ronald J. Beyers¹, and Shumin Wang^1
1Auburn University, Auburn, AL, United States, ²Siemens, Malvern, PA, United States

Early stages of heart failure are characterized by reduction in energy reserve with impairment of myocardial contractility and/relaxation. The Pcr/ATP ratio obtained from 31P MRS is a metabolic parameter to assess myocardial energetic reserves. In this study, we propose to develop a four-channel 1H/31P dual-tuned transceiver array for cardiac spectroscopy at 7 Tesla. A unique coil design was employed to achieve decoupling of neighboring coils at multiple frequencies simultaneously. Static B1 shimming with both phase and magnitude was further applied at 7T to ensure that no intensity fallout occurs in the heart region. Phantom test results confirmed the design principle.

Gunthard Lykowsky¹, Flavio Carinci¹, Peter M. Jakob^1,2, and Daniel Haddad^1
1MRB Research Center, Würzburg, Bavaria, Germany, ²Department of Physics 5, University of Würzburg, Würzburg, Bavaria, Germany

Although sodium imaging has shown promising results for years, sodium MR is still intrinsically challenging because of the low sensitivity of the 23Na nucleus, low in vivo concentrations, fast transverse relaxation times and the requirement for dual tuned RF coils. Several dual tuning approaches with specific advantages and drawbacks have been proposed over the years, e.g. LC traps, PIN diodes or additional rungs. In this study we use an alternate rung concept to build a 1H/23Na quadrature birdcage and evaluate its performance in regards of SNR and B1 homogeneity.

Phillip D. Bishop¹, Jason W. Sidabras¹, Andrzej Jesmanowicz¹, Rupeng Li¹, and James S. Hyde^1
1Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States

A 400 MHz (9.4 T) site-specific surface coil was developed to image the rat forepaw barrel subfield at the cortical column level for functional MRI BOLD studies. To pinpoint this activation to a specific cortical column, the signal-to-noise ratio (SNR) must be appreciably high with a very small voxel size. A low-noise-amplifier was used to overcome losses along the signal path. Images with resolution under 200 micron cubic are now possible. SNR values comparing different voxel sizes are tabulated and compared to the traditional Bruker Surface Coil.

Dominik Berthel¹, Michael Neumaier², Titus Lanz¹, Thomas Kaulisch², and Detlef Stiller^2
1Rapid Biomedical GmbH, Rimpar, Germany, ²In-Vivo Imaging Unit, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach, Germany

Positioning the muscle fibers along the main magnetic field (B0) is important to obtain well-resolved and undistorted lipid MR-spectra. For qualified 1H-MR spectroscopy (1HMRS) of intra-myocellular lipids (IMCL) we present a positioning and fixation setup for the mouse calf combined with an optimized and highly sensitive two channel RF receive coil. By the use of this setup fast positioning of the in vivo objects are assured, incorrect voxel-positions will be avoided and so a high throughput of IMCL-studies can be achieved.

Seunghoon Ha¹, Se-Ho Lee², Mark Jason Hamamura¹, Keum-Shik Hong², and Orhan Nalcioglu^1,2
1Tu & Yuen Center for Functional Onco-Imaging, University of California Irvine, Irvine, California, United States, ²Department of Cogno-Mechatronics Engineering, Pusan National University, Busan, Busan, Korea

The high resolution multinuclear imaging in animal study has been highly demanded to research cancer therapies, neurodegenerative diseases and metabolic disorders. Although dual-tuned RF coil provide anatomical and functional MRI without subject’s repositioning issued from the use of two separate tuned RF coils, it causes SNR loss due to adding trap circuit or PIN diode. Against this reserved problems, we suggest the exchangeable single tuned RF coil configuration on the fixed couch frame without subject’s repositioning in the study. We prepare a dual tuned RF coil and two single tuned RF coils as well as evaluate SNR of separate coils with scanned animal MR images.

Norman B. Konyer^1,2, Alexey A. Tonyushkin^3,4, Andrew J.M. Kiruluta^3,4, and Michael D. Noseworthy^1,2
1Imaging Research Centre, St. Joseph's Healthcare, Hamilton, Ontario, Canada, ²Electrical and Computer Engineering Dept., McMaster University, Hamilton, Ontario, Canada,³Radiology Dept., Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, ⁴Physics Dept., Harvard University, Cambridge, MA, United States

Patch antenna is a typical choice for a transmit/receive probe for a traveling wave MRI (TW-MRI) on 7T preclinical scanners. We demonstrate an alternative circularly polarized coil that is more ideally suited for TW-MRI in systems, where the diameter-to-critical-wavelength ratio is small. The coil consists of two orthogonal loop-coils that are driven in quadrature. We used our coil for TW-MRI in a clinical 3T system to image a long dielectric rod filled with saline, and a bottle of saline adjacent to the rod. The SNR from this coil is significantly improved over previous linear coils developed for TW-MRI and tested on 3T system. With these improved coils, it is possible to apply far-field imaging concepts to a clinical 3T system.

Daniel Hernandez¹, Marlon Perez¹, and Soo Yeol Lee^1
1Bio-medical Engineering, Kyung Hee University, Yongin-si, Gyeonggi-do, Korea

In a helmet-style head array coil consisting of loop-coil elements, some coil elements are nearly vertical to the z-axis making a blind region around the central axis of the loop coil. We propose a surface coil structure that consists of two parallel conductor planes to be placed vertically to the z-axis. We use the B1 components parallel to the conductor planes at one side of the coil. The vertical planar coil does not produce a blind region near it. Through phantom and human brain imaging experiments, we compared the imaging performances between a conventional loop coil and the proposed coil.

Patrick Bollgrün¹, Dario Mager¹, Michael Bock², and Jan G. Korvink^1,3
1Department of Microsystems Engineering, University of Freiburg - IMTEK, Freiburg, Germany, ²Department of Radiology, University Hospital Freiburg, Freiburg, Germany,³Freiburg Institute for Advanced Studies - FRIAS, University of Freiburg, Freiburg, Germany

In this work, a flexible magnetic flux guide which consists of a series of inductively coupled electric resonators on an elastic carrier structure is used to guide the magnetic flux created during signal reception in a magnetic resonance system and overcome unwanted geometric constraints on applications such as interventional MRI. An RF signal travels through the waveguide by inductive coupling between the individual resonators, thus transmitting the magnetic flux over a considerable distance even when the structure is bent. Magnetic resonance imaging was successfully performed, which indicates that such waveguides could become a valuable alternative to conventional receive coil arrangements.

Daniel Gogola¹, Ladislav Valkovic¹, Tomáš Dermek¹, Martin Škrátek², Vladimír Juráš¹, and Ivan Frollo^1
1Department of Imaging Methods, Institute of Measurement Science, Bratislava, Slovakia, ²Department of Magnetometry, Institute of Measurement Science, Bratislava, Slovakia

It has been demonstrated that a receiving coil designed from HTS material with a dedicated preamplifier can significantly improve SNR of the obtained image at low fields, thus time-demanding signal averaging is no longer needed. From the obtained results, the HTS materials appear to be suitable materials for the construction of complex receiving coils for low field scanners and can also find utilization also in micro imaging at high field scanners.

Simon Auguste Lambert¹, Marie Poirier-Quinot¹, Ludovic De Rochefort², Jean-christophe Ginefri², and Luc Darrasse^1
1UMR 8081, IR4M, Univ Paris Sud, CNRS, Orsay, Paris, France, ²UMR 8081, IR4M, Univ Paris-Sud, Orsay, Paris, France

For field strengths of 4.7 T and above, cryocooled probes based on normal coil conductors at 30 K have been commercially developed and afford SNR gain factors of 2-4. Only few studies relate sensitivity improvement using superconducting coil above 3 T. A particularly challenging issue with HTS coils for in vivo applications at high field is the design of sub-centimeter coils in order to achieve SNR gains overcoming the limits of normal conducting cryocooled probes. This is the first report of in vivo imaging using a subcentimeter cryocooled HTS 6 mm mean diameter surface coil at 4.7 T.

Christopher Michael Collins¹ and Qing X. Yang^2
1Radiology, New York University Medical Center, New York, NEW YORK, United States, ²Radiology, The Pennsylvania State University, Hershey, PA, United States

Using numerical simulations, we explore the potential of a high-dielectric head coil former to improve MRI at 7T. A helmet-shaped former consisting of several sections was modeled and dielectric properties were optimized in a manual process. The resulting former greatly improved transmit efficiency to the head for both a large volume array and a patch antenna. The ability to perform RF shimming array was not adversely affected by the presence of the high-dielectric former. The former also improved efficiency, homogeneity, and penetration depth of surface coils placed on its outer surface. Results thus far are promising and warrant further investigation.

Alexey A. Tonyushkin^1,2, Norman B. Konyer^3,4, Michael D. Noseworthy^3,4, and Andrew J.M. Kiruluta^1,2
1Radiology Dept., Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, ²Physics Dept., Harvard University, Cambridge, MA, United States,³Imaging Research Centre, St. Joseph's Healthcare, Hamilton, Ontario, Canada, ⁴Electrical and Computer Engineering Dept., McMaster University, Hamilton, Ontario, Canada

Recent developments in ultra-high field MRI have allowed researchers to explore the traveling wave regime. Traveling wave MRI holds promise in a future to solve various RF transmission issues, however, the traveling wave approach is forbidden for clinical MR systems due to their much lower field, and therefore, hard-to-fulfill cut-off requirements. Here, we demonstrate a quasi-static field regime allowing traveling wave concept to be applied in 3T clinical system. We demonstrate MR images of phantoms and human leg with large field of view that are comparable to the ones obtained in ultra-high field scanners (>7T) using traveling wave approach.

Hong Shang¹, Wei Bian¹, Daniel B. Vigneron^1,2, and Xiaoliang Zhang^1,2
1UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, CA, United States, ²Radiology&Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States

Travelling Wave MRI is an emerging method for large FOV imaging at ultrahigh fields. In this work, we investigate parallel imaging performance in traveling wave MRI using simple microstrip transceiver arrays. The two-element arrays were placed orthogonally at the end of the bore of a 7 Tesla whole body MR scanner for excitation and reception. MR experiment was performed demonstrating sufficient spatial diversity of B1 fields of each transceiver channel and good quality of parallel accelerated images.

Wyger M. Brink¹ and Andrew Webb^1
1Radiology, Leiden University Medical Center, Leiden, Netherlands, Zuid-Holland, Netherlands

High permittivity pads are shown to improve the B1 homogeneity to a level similar to that of an eight-channel system, however without the penalty of reducing the transmit efficiency. The best transmit setup for 3T body imaging is shown to be the two-channel system with high permittivity pads.

Sebastian A. Aussenhofer¹ and Andrew Webb^1
1Department of Radiology Leiden University Medical Center, CJ Gorter Center for High Field MRI, Leiden, South Holland, Netherlands

A dielectric resonator made from a high permittivity low loss barium strontium titanate has been designed to operate in degenerate quadrature HEM11 modes at 298.1 MHz (7 Tesla). The compact resonator was designed for high resolution imaging of human digits with a high filling factor and patient comfort. New methods of double tuning such a resonator to proton/fluorine are also presented.

Zhipeng Cao¹, Wei Luo², Christopher T. Sica², Sukhoon Oh³, Sebastian Rupprecht², Giuseppe Carluccio³, Christopher Michael Collins³, and Qing X. Yang^2
1Radiology, Pennsylvania State University, Hershey, PA, United States, ²Radiology, The Pennsylvania State University, Hershey, PA, United States, ³Radiology, New York University, New York City, NY, United States

A simulation analysis of the effect of high dielectric materials on receive efficiency and g-factor for a phantom within an 8-channel head sized array is performed using numerical calculations. Results indicate that strategic use of high dielectric materials can provide notable improvement in parallel imaging performance for a given sample with standard coil setup.

Hyeokwoo Son¹, Ahryum Kim², Jinyoung Choi¹, Youngki Cho¹, and Hyoungsuk Yoo^2
1School of Electronics Engineering, Kyungpook National University, Daegu, Korea, ²School of Electrical Engineering, University of Ulsan, Ulsan, Korea

Magnetic Resonance Imaging (MRI) systems have good intrinsic SNR (signal-to-noise ratio) and are used an important instrument for diagnosis. Recently, transceive phased array coils using transmission lines in MRI systems have been studied for parallel imaging[1-3], RF shimming[4] and RF homogenization[5]. These coils are composed of several RF resonators that are independently controlled by adjusting the amplitude and phase of the excitation. Microstrip, one of most widely used transmission lines, is used to design a transceive array coil element. The RF resonators using microstrip operate at a Larmor frequency of 128 MHz (3T). In this paper, we introduce four different RF resonators and a slot loaded RF resonator shows better RF efficiencies than other three RF resonators.

Jorge Fernandez Villena¹, Amit Hochman², Luis Miguel Silveira¹, Elfar Adalsteinsson^2,3, Lawrence L. Wald^3,4, Jacob K. White², and Luca Daniel^2
1INESC ID Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento, Lisbon, Portugal, ²Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, ³Harvard-MIT Division of Health Sciences Technology, Cambridge, Massachusetts, United States, ⁴Department of Radiology, Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, United States

We propose a fast electromagnetic (EM) simulation of RF coils operating in the presence of realistic human body models (RHBM), based on frequency-domain integral equation methods. We introduce the RHBM Green’s functions (GF), which mimic the effect of the RHBM inside an EM field due to coil’s currents. This RHBM GF needs to be precomputed only once for a given complex body model, and then it can be combined with traditional Boundary Element Methods that only discretize the coil surface. This scheme generates smaller models that are very fast to solve, allowing for efficient coil design exploration.

Zhipeng Cao¹, Christopher T. Sica², Wei Luo², Sukhoon Oh³, and Christopher Michael Collins^3
1Radiology, Pennsylvania State University, Hershey, PA, United States, ²Radiology, The Pennsylvania State University, Hershey, PA, United States, ³Radiology, New York University, New York City, NY, United States

A method for generating simulated MR images (starting with knowledge of only pulse sequence, receiver bandwidth, and distributions of sample properties and field distributions through space) with realistic levels of noise is described and demonstrated with comparison to experimentally-measured SNR.

Zhipeng Cao¹, Christopher T. Sica², Giuseppe Carluccio³, and Christopher Michael Collins^3
1Radiology, Pennsylvania State University, Hershey, PA, United States, ²Radiology, The Pennsylvania State University, Hershey, PA, United States, ³Radiology, New York University, New York City, NY, United States

A method for simulating intra-voxel dephasing in Bloch-based MRI simulation that is a hybrid of existing methods is introduced and compared to its predecessors. Results indicate much greater accuracy than either of the prior methods with little increase in computational resources.

Necip Gurler¹, Fatih Suleyman Hafalir¹, Omer Faruk Oran¹, and Yusuf Ziya Ider^1
1Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey

An accurate method and a software tool for the capacitance calculation of low-pass and high-pass birdcage coils using a Finite Element Method (FEM) based optimization algorithm is presented. For the verification of the algorithm, 8-leg low-pass and high-pass birdcage coils are constructed and capacitance values used in the experiments are compared with the capacitance values calculated using our algorithm and also with the capacitance values obtained by the widely used software BirdcageBuilder which is based on a lumped element circuit model. Results show that our algorithm is more accurate than the lumped element circuit models especially at higher frequencies.

Changheun Oh¹, Yeji Han¹, and HyunWook Park^1
1Electrical engineering, Korea Advanced Institute of Science and Technology, Daejeon, Daejeon, Korea

the coupling of RF noise between electronics in the PET system and RF coil of the MRI system can degrade the MR image quality. In addition, the center frequency of the RF coil may experience shifting due to the PET insert. In order to solve the RF noise coupling and frequency shifting problems, an appropriate RF shield should be used. For an MRI-PET fusion system with an add-on/off type PET insert, a gold-mesh tape shield is proposed for the RF coil in this study.

Changheun Oh¹, Yeji Han², and HyunWook Park^1
1Electrical engineering, Korea Advanced Institute of Science and Technology, Daejeon, Daejeon, Korea, ²Korea Advanced Institute of Science and Technology, Daejeon, Daejeon, Korea

In the integrated MRI-PET system, the coupling of RF noise between electronics in the PET system and RF coil of the MRI system, and frequency shifting of RF coil can be main problems that can deteriorate MR image quality. In this study, we propose an MRI-PET fusion system, which can simultaneously acquire MRI and PET images by using an add-on/off type PET insert, and a gold-mesh tape shield is used to improve the MR image quality.

Stephan Biber¹, Ralf Ladebeck¹, David Faul², and Yvonne Candidus^1
1Siemens Healthcare Magnetic Resonance Imaging, Erlangen, -, Germany, ²Siemens Healthcare Molecular Imaging, Knoxville, TN, United States

With the introduction of integrated MR-PET systems both for preclinical animal studies as well as full sized human scanners, the question of PET attenuation originating from MR hardware (MR-HW) which is located between the patient and the PET camera, has been a topic of increasing interest for research. Prvious studies have identified mechanical structures for the patient table, the housings of local coils as well as the electronics and antenna structures within these housings as the major contributions to PET signal attenuation. This attenuation map needs to be included in the PET reconstruction. The goal of this paper is to evaluate the feasibility and the potential advantages of MR-HW attenuation correction based on 3D data coming from a LINAC instead of a CT, which has been used for measurement of hardware attenuation in earlier studies. The advantage of a LINAC based scan can be the reduced level of artifacts, as the LINAC provides a radiation beam with photons of much higher energy than the CT.

Christian Stehning¹, Michael Helle², Stefanie Remmele³, and Melanie Kotys-Traughber^4
1Philips Research Europe, Hamburg, Germany, ²Philips Research Laboratories, Hamburg, Germany, ³Hochschule Landshut (FH), Landshut, Germany, ⁴Philips Healthcare, Cleveland, Ohio, United States

MR-based radiation therapy planning (RTP) and hybrid PET/MR systems require a complete segmentation of bone, soft tissue, and air for attenuation correction. Conventional MRI sequences cannot reliably differentiate between air and bone. While promising results for cortical bone were obtained with 3D ultrashort echo time imaging (UTE) in the knee and head, UTE bone imaging in the pelvis is more demanding due to the significantly larger FOV. A UTE Dixon sequence and reconstruction workflow is presented, which provides good in vivo image quality and reliable bone segmentation over a 400mm FOV. This is an integral component of emerging application such as MR-based therapy planning, and hybrid PET/MR systems.

Daniel H. Paulus¹, Harald Braun¹, and Harald H. Quick^1
1Institute of Medical Physics, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany

In hybrid PET/MR imaging local receiving RF coils, placed in the FOV, attenuate and scatter PET annihilation photons thus affecting PET quantification. Flexible RF surface coils are yet omitted in PET attenuation correction (AC), because they can vary in position and geometry. Several CT-based attenuation maps (µ-map) of the RF coil were used for PET AC to evaluate the effect of different parameters. Furthermore small shifts and rotations of the µ-map simulating misregistration or motion of the patient were analyzed. Depending on the PET reconstruction algorithm the shifts can cause artifacts or just a bias of the activity concentration.

Bassim Aklan¹, Daniel H. Paulus¹, David Fual², Christian Geppert³, Eric E. Sigmund⁴, Amy Melsaether⁵, Evelyn Wenkel⁶, Harald Braun¹, Susanne Ziegler¹, and Harald H. Quick^1
1Institute of Medical Physics, University of Erlangen-Nuernberg, Erlangen, Germany, ²Siemens Medical Solutions, New York, NY, United States, ³Siemens Medical Systems, New York, NY, United States, ⁴Department of Radiology for Biomedical Imaging NY Langone Medical Center, New York, NY, United States, ⁵Breast Imaging Section, Department of Radiology Medical Center, New York, NY, United States, ⁶Institute of Radiology, University Hospital Erlangen, Erlangen, Germany

Simultaneous PET/MR breast imaging requires the RF breast coil necessary for MR data acquisition to be located in the FoV of the PET detector thus attenuating PET signals and reducing PET quantification accuracy. Integration of a commercial 4-channel RF breast coil on an integrated PET/MR hybrid system resulted in local PET signal attenuation of 4-16% in systematic phantom experiments. Application and registration of a CT-based attenuation map of this coil resulted in successful attenuation correction (AC). First PET/MR studies in breast cancer patients demonstrate successful integration of the RF breast coil into the new application of PET/MR breast imaging.

Daniel H. Paulus¹, Harald Braun¹, Bassim Aklan¹, and Harald H. Quick^1
1Institute of Medical Physics, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Bavaria, Germany

In simultaneous PET/MR imaging, local receiving RF coils are positioned in the FOV of the PET detectors and attenuate the PET signal. Flexible RF surface coils vary in position and geometry and are thus omitted in PET attenuation correction (AC). In a phantom experiment and a patient scan, local deviations of up to 15% in the PET emission images were observed, when the coil is omitted in PET AC. It is demonstrated that with CT-based AC of the RF coil, where markers were used for image registration of MR and CT, the PET signal attenuation could mostly be corrected.

Bharath K. Navalpakkam¹, Harald Braun², Joachim Hornegger¹, Torsten Kuwert³, and Harald H. Quick^2
1Pattern Recognition Lab, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Bavaria, Germany, ²Institute of Medical Physics, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Bavaria, Germany, ³Clinic of Nuclear Medicine, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Bavaria, Germany

An MR-based attenuation correction approach for PET/MR that includes cortical bone information is proposed. An epsilon insensitive Support Vector Regression model is trained and validated on head regions for five patients. The reconstructed PET data is evaluated for the proposed approach (PETMRAC) against other approaches that include (PETboneAC) and disregard bone class (PETnoboneAC). For the complete brain, PETMRAC yielded a mean absolute error of 2.40±3.59%, 10.15±3.31% for PETnoboneAC and 3.96±3.71% for PETboneAC. For atlas segmented landmarks, the errors for the same were 2.16±1.77%, 11.03±2.26% and 4.22±3.91%, respectively. An initial result of an MR-based pseudo-CT for a whole-body application is illustrated.

Jonathan D. Thiessen¹, Eric Berg², Chen-Yi Liu^1,3, Daryl Bishop⁴, Piotr Kozlowski^5,6, Fabrice Retière⁴, Vesna Sossi⁶, Greg Stortz⁶, Christopher J. Thompson⁷, Xuezhu Zhang¹, and Andrew L. Goertzen^1,3
1Radiology, University of Manitoba, Winnipeg, Manitoba, Canada, ²Biomedical Engineering, University of California, Davis, Davis, California, United States, ³Physics & Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada, ⁴Detector Development Group, TRIUMF, Vancouver, British Columbia, Canada, ⁵Radiology, University of British Columbia, Vancouver, British Colubmia, Canada, ⁶Physics & Astronomy, University of British Columbia, Vancouver, British Columbia, Canada, ⁷McConnell Brain Imaging Centre, Montreal Neurological Institute, Montreal, Quebec, Canada

An MR-compatible PET detector module featuring a silicon photomultiplier coupled to a dual-layer LYSO scintillator crystal array and using an HDMI cable for supplying power and bias as well as transmitting analog signals was tested in a 7 T Bruker MRI. Performance of the PET detector was evaluated inside the MRI as was performance of the MRI with the PET detector present and operating. Given the limited interactions between the operating PET detector module and MRI, the current PET detector design appears to be a viable first step in creating an MR-compatible full-ring PET system.

Susanne Ziegler¹, Harald Braun¹, Philipp Ritt^2,3, Carsten Hocke², Torsten Kuwert², and Harald H. Quick^1
1Institute of Medical Physics, University of Erlangen-Nuremberg, Erlangen, Germany, ²Clinic for Nuclear Medicine, University Hospital Erlangen, Erlangen, Germany, ³Pattern Recognition Lab, University of Erlangen-Nuremberg, Erlangen, Germany

Simultaneous PET/MR hybrid imaging of fluid-filled phantoms can be problematic. Pure water can cause inhomogeneous RF excitation when imaging large sized phantoms at high field strength. Oil, as alternative fluid, does not mix well with the standard PET radiotracer ¹⁸F-FDG. In this study three different approaches of fluid and radiotracer selection were considered and systematically evaluated with respect to their usability for simultaneous PET/MR phantom imaging. Alternative fluids as a compromise for both imaging modalities and workarounds for improving the use of standard fluids are presented. Additionally an alternative radiotracer to ¹⁸F-FDG is proposed and evaluated in PET/MR measurements.

Harald Braun¹, Susanne Ziegler¹, and Harald H. Quick^1
1Institute of Medical Physics, University of Erlangen-Nürnberg, Erlangen, Germany

In simultaneous whole-body PET/MR imaging, data is usually acquired in a multi-station (step-and-shoot) approach. In contrast, an acquisition paradigm with continuous table motion that was introduced recently allows for seamless whole-body coverage and greater flexibility in the planning workflow. To allow the use of continuous table motion acquisitions in clinical protocols, it must be evaluated which impact table motion speed has on MR and PET image quality. This was performed for the available MR protocols that support continuous table motion (FLASH 2D, FLASH 3D, TSE, HASTE, BLADE) and for PET imaging for several different table speeds.

Jens Groebner^1,2 and Michael Bock^1
1Dept. of Radiology / Medical Physics, University Medical Center Freiburg, Freiburg, BW, Germany, ²Dept. of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, BW, Germany

The EU announced that the directive 2004/40/EC will be replaced by a proposal of the European Commission (EC). In this work the EC limit values and the 2004/40/EC’s limit values are compared to MR exposure data. 37 MR workers were asked to wear a field probe in the magnet room (up to 7T). Results show that the new limits (both peak and average) can be exceeded during routine work. With an optic/acoustic response system the EC’s proposal can help reducing transient effects like vertigo or magnetophosphenes.

Ian C. Atkinson¹, Wesley McClain¹, Neil Pliskin², and Keith R. Thulborn^1
1Center for MR Research, University of Illinois at Chicago, Chicago, IL, United States, ²Psychiatry, University of Illinois at Chicago, Chicago, IL, United States

Current FDA guidelines classify MR devices operating at up to 8 Tesla as insignificant risk. Vital sign and cognitive performance data supporting the safety of performing non-proton MR imaging of the human brain at 9.4 Tesla in healthy and for-cause volunteers are presented. These data add to the growing body of results that suggest ultra-high field MR imaging can be safely performed up to 9.4 Tesla.

Jens Groebner^1,2, Reiner Umathum², and Michael Bock^1
1Dept. of Radiology / Medical Physics, University Medical Center Freiburg, Freiburg, BW, Germany, ²Dept. of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, BW, Germany

The EU directive 2004/40/EC is currently under review and will be replaced in future. In this study a wireless MR exposure monitoring probe is presented for exposure monitoring. A magnetic field probe consisting of three Hall sensors and induction coils is worn at the head of a volunteer. The exposure data (B₀, dB/dt, dB/dt_rot+trans*) is recorded on a SD memory card. Six measurements were performed in the vicinity of a 7T MR system. The new limits would only be exceeded during measurements in a frequency range of 0.6-1Hz and if the ICNIRP definition of dB/dt_rot+trans is used.*according to ICNIRP

Chad Tyler Harris¹, William B. Handler¹, and Blaine A. Chronik^1,2
1Physics and Astronomy, Western University, London, Ontario, Canada, ²Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada

The ability to accurately calculate the induced current distribution, caused by gradient switching, over arbitrary thin conducting surfaces is extremely useful for the design and MR safety evaluation of medical devices and interventional robotics. In this abstract we present an integral method to calculate these induced currents. The method is applied to predict the average heating rate of a thin conductor and then extended to calculate the spatial distribution of power deposition over the conductor surface and subsequent spatially varying heating rate.

Di Qian^1,2, AbdEl-Monem M. El-Sharkawy³, Paul A. Bottomley^2,3, and William A. Edelstein^1
1Radiology, Johns Hopkins School of Medicine, Baltimore, MD, United States, ²Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, United States,³Radiology, Johns Hopkins University, Baltimore, MD, United States

We have developed an RF dosimeter for independent measurement of average whole-body RF exposure at 3T. The dosimeter includes an RF transducer with two tuned, orthogonal resistive loops and a lossless phantom. The loop impedances are adjusted so that the power deposited in the transducer is equivalent to that for an average human subject while minimizing B1-interference with the scanner. The deposited RF power is measured by sampling the current in the transducer loops. The dosimeter is tested on multiple GE, Philips, and Siemens MR systems, and can be used independent of make or model for a given MR frequency.

Sukhoon Oh¹, Yeun-chul Ryu², and Christopher Michael Collins^1
1Center for Biomedical Imaging, School of Medicine, New York University, New York, New York, United States, ²Center for NMR Research, Radiology, College of Medicine, The Pennsylvania State University, Hershey, Pennsylvania, United States

In this study, we report the effect of a surface coil close to the subject on SAR and temperature increase. We observed notable effect on both SAR and temperature distribution near the surface coil.

Peter Vernickel¹, Christoph Leussler¹, Daniel Wirtz¹, and Ingmar Graesslin^1
1Philips Research Laboratories, Hamburg, Germany

MR imaging demands an exact control of the SAR to ensure patient safety. Dedicated hard- and software is used to measure the complex coil currents I, coil quality factor Q, or reflection coefficient Sxx to ensure that the scan runs within allowed limits. However, uncertainties may exist when relying on the verification of one of the mentioned quantities, because this can lead to ambiguous results when characterizing the complex arrangement of coil and load. This abstract demonstrates an example for a situation in which measuring I, Q or S11 while slightly modifying arrangement of coil and load leads to misleading results for SAR monitoring.

Wolfgang Görtz¹, Nicolas Fülle¹, Gerrit Schönwald¹, Susanne Matthey¹, and Gregor Schaefers^1
1MR:comp GmbH, Germany, Gelsenkirchen, NRW, Germany

RF-heating tests as described in ASTM F2182 have been performed in a 1.5 Tesla MR scanner and additionally in a 64 MHz RF laboratory workbench system. A comparison of the results of the detected temperature increases shows a good agreement between both systems. Based on this finding it can be concluded that the laboratory system is an alternative to usually used clinical MR systems for RF heating test on medical implants following ASTM F2182.

Frank Seifert¹ and Bernd Ittermann^1
1Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany

Local SAR prediction in pTX MRI based on real-time multi-channel driving voltage measurements with directional couplers are prone to model variations even when the ‘worst case’ values for different models a similar. Hence, when aiming to go beyond, i.e. below, ‘the worst case’ scenario for patient safety in pTx MRI, even the careful validation of simulation results including the variability ‘real life applications’ is already a challenging task.

Devashish Shrivastava¹, Lynn Utecht¹, Jinfeng Tian¹, Rachana Visaria², John Hughes¹, and University of Minnesota University of Minnesota Vaughan^1
1University of Minnesota, Minneapolis, MN, United States, ²MR Safe Devices, Burnsville, MN, United States

Radiofrequency (RF) heating during head imaging with a transmit body coil is unknown and a safety concern. To better understand this heating, the heating was simulated by solving the new, analytical generic bioheat transfer model (GBHTM) and the ‘gold standard’ empirical Pennes bioheat transfer equation in a digital pig with the pig head in the isocenter of a 3T, birdcage, transmit body coil. The simulations were validated by direct fluoroptic measurements in anesthetized swine. The GBHTM simulations as well as the measurements showed that in vivo temperatures may change significantly due to the power deposition from a body coil.

Klaus M. Huber¹, Joerg Roland², Johanna Schoepfer¹, Stephan Biber², and Sebastian Martius^1
1Corporate Technology, Siemens, Erlangen, Germany, ²Healthcare, Siemens, Erlangen, Germany

Monitoring local and global SAR is one of the major challenges on the way to the clinical use of parallel TX arrays. Usually, SAR estimations are based on numerical simulations with 3D-EM-tools which are rather sophisticated and tend to deliver erroneous results in case of unprecise inputs. PRF-based MR thermometry might be a powerful tool to determine spatial temperature maps and thus cross-check SAR simulations. The motivation of this study is to examine the feasibility and quantitative accuracy of MR thermometry for SAR and temperature monitoring of local transmit antenna arrays based on existing hardware.

Mikhail Kozlov¹, Gunamony Shajan², and Robert Turner^1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany, ²Max Planck Institute for Biological Cybernetics, Tuebingen, Germany

For an already constructed 9.4T dual row array, excited in CP and other transmit modes, we investigated peak SAR averaged over 10 grams (SAR10g) for different tuning conditions, and different head positions with three scaling factors. For a given array, the tuning condition significantly affected SAR10g, while the influence on SAR10g of head position and scaling factor was relatively small.

Amit Hochman¹, Jorge Fernandez Villena², Luis Miguel Silveira², Elfar Adalsteinsson^1,3, Lawrence L. Wald^3,4, Jacob K. White¹, and Luca Daniel^1
1Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, United States, ²INESC ID Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento, Lisbon, Portugal, ³Harvard-MIT Division of Health Sciences Technology, Cambridge, MA, United States, ⁴Department of Radiology, Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States

We propose a method for combining electromagnetic field solutions obtained for a small set of excitations so as to approximate the solutions for nearby excitations. This work is relevant for coil and excitation design.

Mélina Bouldi¹ and Jan M. Warnking^1,2
1Grenoble Institut des Neurosciences - UJF, Grenoble, Rhône-Alpes, France, ²Inserm U836, Grenoble, Rhône-Alpes, France

Understanding the risks of overheating due to the presence of active implants requires a rigorous simulation of experimental conditions. We built a numerical elliptical birdcage model of the whole body transmit coil in a Philips Achieva TX® system, using the SEMCAD X software (Speag®). The resonator was tuned to 128MHz. The simulated current density distribution, B1 map and temperature changes qualitatively agree with the theoretically predicted and experimentally observed behavior. Quantitative differences remain. Our method of validation, permits to assess the validity of the resonator model, and paves the way for a realistic numerical elliptic resonator model.

Yu Shao¹, Peng Zeng², Joseph Murphy-Boesch³, Jeff H. Duyn³, Alan P. Koretsky³, and Shumin Wang^1
1Electrical and Computer Engineering, Auburn University, Auburn, AL, United States, ²Mathematics and Statistics, Auburn University, Auburn, AL, United States, ³LFMI/NINDS/NIH, Bethesda, MD, United States

Local specific absorption rate analysis is critical to the safety of high-field human MRI studies. In order to address the inter-subject variability in head dimensions and the variability in the relative position of the human body to the RF coil, applying the conventional Monte Carlo method would require a fairly large number of simulations. In order to dramatically improve the efficiency of statistical simulations, we propose a new approach based on the Latin Hypercube Sampling (LHS). The LHS can achieve the same accuracy with much smaller run size than conventional Monte Carlo sampling because it guarantees that the selected runs uniformly spread across the domain of each input variable. We demonstrate that with a few sampling points (17 samples), the expectation, the standard deviation and sensitivity to changes in conditions, such as the head geometry and its relative position, can be accurately computed when six random variables were considered. This approach appears uniquely suited for RF safety assessment.

Toru Yamamoto¹ and Minghui Tang^2
1Faculty of Health Sciences, Hokkaido University, Sapporo, Hokkaido, Japan, ²Graduate School of Health Sciences, Hokkaido Univrsity, Sapporo, Hokkaido, Japan

Prediction of the RF burning that may occur during an MRI examination is one of the key issues in MR safety. Although several methods have been developed for mapping the specific absorption rate (SAR), few practical methods for predicting RF burning have been demonstrated because of the difficulty in actualizing RF burning in a phantom study. In this study, we developed a method of mapping high-SAR areas using a low-RF power scan and demonstrated the prediction of RF burning in a phantom study using an elaborate setup of an RF resonant loop.

Muhammad Hassan Chishti¹, Zhangwei Wang², and Desmond Yeo^1
1GE Global Research Center, Niskayuna, New York, United States, ²GE Healthcare, Waukesha, Wisconsin, United States

The ability to accurately predict Specific Absorption Rate (SAR) is a key to patient safety during RF exposure in MR scans. SAR is highly dependent on accurate values of the tissues’ electrical properties. In this work, we investigate the errors in EM-modeling-based SAR prediction when incorrect electrical conductivity and relative permittivity values are applied. In the 7T human body model simulations performed, results show that the maximum deviation (from nominal) of the ratio of peak SAR10g to the whole head average SAR is -7.83% and occurs when both electrical conductivity and relative permittivity of the tissues are reduced by 20%.

Alan Leewood¹, David Gross¹, Jeff Crompton², Sergei Yushanov², Orlando P. Simonetti³, and Yu Ding^3
1MED Institute, Inc., West Lafayette, IN, United States, ²AltaSim Technologies, LLC, Columbus, OH, United States, ³The Ohio State University, Columbus, OH, United States

MR safety of electrically conductive passive implants is directly related to localized heating of tissue when the device is subjected to RF powered E-fields. Current MR Safety methodology relies primarily on experimental methods (ASTM F2182), which use a gel phantom and produce conservative estimates of temperature rise for vascular devices due to lack of blood-flow. Ultimately, this raises the issue that clinically indicated MRI scans may be inappropriately withheld from patients because RF heating concerns were based on inappropriately conservative test methods. This work is an investigation of the effects of including vascular flow on the cooling of passive implants.

Rupam Kumar Das¹ and Hyoungsuk Yoo^1
1Department of Biomedical Engineering, School of Electrical Engineering, University of Ulsan, Ulsan, Korea

The RF coils in Magnetic Resonance Imaging (MRI) systems induce scattered electric field in the medical implant, and the principal bio effect is tissue heating. In this work, a noble design to reduce the scattered field has been proposed. In this proposed design, metal nails have been placed along the length of the medical lead. The scattered electric field is calculated near the lead tip at 64 MHz for a model implant by using Ansoft HFSS. By using this method, a significant decrease in the scattered electric field has been observed. Key Word : MRI,pacemaker,implantable device,lead,RF heating

Craig I. Lawrie¹, Xiaoyu Yang¹, Tsinghua Zheng¹, Matthew Finnerty², Shinya Handa², and Hiroyuki Fujita^2,3
1Quality Electrodynamics, LLC, Mayfield Village, Ohio, United States, ²Quality Electrodynamics, Mayfield Village, Ohio, United States, ³Department of Physics, Case Western Reserve University, Cleveland, Ohio, United States

The use of a local transmitter coil to reduce local SAR heating is evaluated with regards to MRI imaging in the presence of long conductive media. Simulation results indicate that a local transmitter coil has an SAR advantage due to both smaller electric fields and the ability to fine-tune geometric positioning.

Lukas Winter¹, Davide Santoro¹, Alexander Müller¹, Wolfgang Renz^1,2, Celal Özerdem¹, Andreas Graessl¹, Valeriy Tkachenko³, Jeanette Schulz-Menger^3,4, and Thoralf Niendorf^1,3
1Berlin Ultrahigh Field Faciltiy (B.U.F.F.), Max-Delbrück Center for Molecular Medicine, Berlin, Germany, ²Siemens Healthcare, Erlangen, Germany, ³Experimental and Clinical Research Center (ECRC), a joint cooperation between Charité Medical Faculty and Max-Delbrück Center for Molecular Medicine, Berlin, Germany, ⁴Department of Cardiology and Nephrology, HELIOS Klinikum Berlin-Buch, Berlin, Germany

This study examines RF induced heating, which potentially can be caused by an electrically conductive coronary stent in combination with RF fields applied at ultrahigh field (UHF) MR. EMF simulations, phantom experiments and MR thermometry were performed and show that in a careful evaluated setup, RF induced heating due to the presence of a coronary stent may not be significant versus the baseline heating induced by a cardiac optimized transmit/receive RF coil at 7.0T.

Christopher W. Ellenor¹, Pascal P. Stang¹, John M. Pauly¹, and Greig C. Scott^1
1Electrical Engineering, Stanford University, Stanford, CA, United States

In a simple phantom study, we compare the use of two techniques for the visualization of dangerous currents in implanted wires. The phantom is imaged using the reverse-polarization method, twister gradients, or a combination of the two, and the conspicuity of the current-carrying wire is determined by measuring image contrast. We find that gradient spoiling can achieve results similar to reverse polarization. We also employ a numerical model to attempt to extrapolate these results to 3T and 7T systems, where we find very similar results at 3T, and a reduction in effectiveness of reverse polarization at 7T.

Daniel G. Wakeman¹, Boris Keil¹, Bill McSwain², Maria Ida Iacono¹, Catherine Poulsen², and Giorgio Bonmassar^1
1A.A. Martinos Center for Biomedical Imaging, Harvard Medical School, Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ²Electrical Geodesics, Inc., Eugene, OR, United States

We show safety testing of a new 256 channel EEG device at 7T. Previous studies have shown that high density EEG caps in high field strength MRI (3 & 7T can generate high SAR. We performed SAR simulations and Temperature measurements on a conductive phantom to test the risk of heating.

Michael C. Steckner¹ and Emanuel Kanal^2
1TMRU, Mayfield Village, OH, United States, ²Department of Radiology, University of Pittsburgh Medical Center, Pittsburgh, PA, United States

Laser based tattoo removal techniques are growing in popularity, but conductive ink constituents remain. Thus the MRI safety profile of tattoos may remain unchanged or even more complex. With the increasing number of tattoos and tattoo removals, caution is needed to identify all existing or partially removed tattoos, either decorative or cosmetic, during the patient screening process.