Kartiga Selvaganesan¹, Yonghyun Ha², Basong Wu², Kasey Hancock³, Charles Rogers III², Sajad Hosseinnezhadian², Gigi Galiana², and Todd Constable^2
1Biomedical Engineering, Yale University, New Haven, CT, United States, ²Radiology and Biomedical Imaging, Yale University, New Haven, CT, United States, ³Electrical Engineering, Yale University, New Haven, CT, United States

The ability to form an image without using spatial encoding gradients allows for cheaper MRI manufacturing costs, particularly in small low field devices suitable for point-of-care imaging. The Bloch-Siegert shift effect provides an RF alternative to spatial encoding with gradient coils. This work presents a new approach to evaluate and optimize nonlinear RF encoding schemes generated by transmit phased arrays. From thousands of possible encoding patterns, the algorithm finds the set that minimizes correlations between spatial patterns while maximizing the spatial encoding. Simulated images demonstrate that the nonlinear spatial encodings provided by Bloch-Siegert RF pulses can provide high image quality.

Efraín Torres^1,2, Taylor Froelich², Lance DeLaBarre², Michael Mullen², Gregory Adriany², Alberto Tannús³, Daniel Cosmo Pizetta³, Mateus Jose Martins³, and Michael Garwood^2
1Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States, ²Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ³Centro de Imagens e Espectroscopia por Ressonância Magnética - CIERMag - Sao Carlos Physics, São Carlos, Brazil

Gradient coils reduce available bore space, incur costs, and create acoustic noise, but their encoding ability requires them to be present in MRI. The encoding strategy introduced here (FREE) removes the reliance on these coils by using a B₁-gradient to create a spatially-dependent nutation frequency. Double spin-echoes created with adiabatic full-passage pulses generate magnetization phase proportional to the difference in their time-bandwidth products (R). Modulating the R-value of one of these π pulses traverses k-space similar to standard MRI. Adiabatic pulses make this approach highly tolerant to B₀ and B₁ inhomogeneity. A family of new sequences using FREE is presented.

Céline Marquet^1,2,3, Jihye Jang^1,2,4, Andrew J. Powell^1,2, and Mehdi H. Moghari^1,2
1Department of Pediatrics, Harvard Medical School, Boston, MA, United States, ²Department of Cardiology, Boston Children's Hospital, Boston, MA, United States, ³Department of Informatics, Technical University Munich, Munich, Germany, ⁴Philips Healthcare, Boston, MA, United States

We developed a novel MRI pulse sequence RAS-Q T₁T₂ for the simultaneous quantification of T₁ and T₂ of the myocardium using transient bSSFP imaging with a variable flip angle scheme. RAS-Q T₁T₂ was systematically analyzed based on a numerical simulation, as well as phantom and patient studies. We show that RAS-Q T₁T₂ yields accurate T₂ estimates for the myocardium with a trade-off in precision compared to state-of-the-art methods, reducing scan time to less than 4s. The estimated T₁ values reveal lower accuracy and precision than clinically established methods and need further improvements.

Jaeyong Yu^1,2, Seulki Yoo^1,2, Jae-Kyun Ryu³, Seung-Kyun Lee^1,2,4, and Jang-Yeon Park^1,2,3
1Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Korea, Republic of, ²Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, Korea, Republic of, ³Biomedical Institute for Convergence at SKKU, Sungkyunkwan University, Suwon, Korea, Republic of, ⁴Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, Korea, Republic of

Equal-TE Rapid Acquisition with Sequential Excitation (ERASE) is a 3D ultrafast gradient-echo-based Spatiotemporal Encoding (SPEN) imaging technique with a constant TE and  high tolerance to main magnetic field () inhomogeneity. However, misregistration of spin isochromat can occur due to large magnetic susceptibility-induced gradients in the prefrontal brain region. Here, we propose that  shim improvement by chin-up head tilting can effectively mitigate misregistration in ERASE to realize fast prefrontal brain imaging with much higher image quality than conventional EPI.

Naoharu Kobayashi¹ and Michael Garwood^1
1CMRR, Radiology, University of Minnesota, Minneapolis, MN, United States

Flip angle and RF pulse phase in 3D MP-SSFP were optimized to maximize SNR. Optimal flip angle and pulse phase were estimated by numerically maximizing the steady-state magnetization in MP-SSFP with SAR penalty. The estimated optimal flip angle and phase were experimentally validated with an agar gel phantom at 3T. The optimal RF pulse setting improved SNR up to 41% under the fixed SAR conditions, depending on MP-SSFP sequence parameters. Finally, in vivo human brain imaging was conducted to demonstrate image contrasts in MP-SSFP images with the optimal flip angle and pulse phase.

Max H. C. van Riel^1,2, Niek R. F. Huttinga¹, and Alessandro Sbrizzi^1
1Department of Radiotherapy, Computational Imaging Group for MR diagnostics and therapy, UMC Utrecht, Utrecht, Netherlands, ²Department of Biomedical Engineering, Medical Image Analysis, Eindhoven University of Technology, Eindhoven, Netherlands

Measuring in vivo dynamics can yield valuable information about the cardiovascular or musculoskeletal system. MRI shows severe limitations when dealing with motion at high spatial and temporal resolutions. We propose spectro-dynamic MRI for the characterization of dynamics directly from k-space data. The sampling pattern is adjusted to achieve a temporal resolution of a few milliseconds. A measurement model, relating the measured data to the displacements, is combined with a dynamical model, introducing prior knowledge about the dynamics. Preliminary results show that spectro-dynamic MRI allows estimation of motion fields and dynamical system parameters from heavily undersampled data on a millisecond timescale.

Johannes Fischer¹, Ali Caglar Özen^1,2, Matthias Echternach³, Louisa Traser⁴, Bernhard Richter⁴, and Michael Bock^1
1Dept.of Radiology, Medical Physics, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany, ²German Consortium for Translational Cancer Research Freiburg Site, German Cancer Research Center (DKFZ), Heidelberg, Germany, ³Division of Phoniatrics and Pediatric Audiology, Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University, Munich, Germany, ⁴Institute of Musicians' Medicine, Freiburg University Medical Center, Germany Faculty of Medicine, University of Freiburg, Freiburg, Germany

Single point imaging with rapid encoding (SPIRE) can dynamically image the oscillations of the vocal folds in the coronal plane with sub-milisecond temporal resolution. To add spatial encoding in the third dimension, a slower frequency encoding gradient was applied in slice direction, where motion is minimal. Electroglottography and projection navigators are used to detect shifts in the larynx position, which are corrected during reconstruction. The velocity of the mucosal wave is estimated from the images.

Hanna Frantz¹, Thomas Huefken¹, Patrick Metze¹, Kilian Stumpf¹, Tobias Speidel¹, and Volker Rasche^1
1Department of Internal Medicine II, Ulm University Medical Center, Ulm, Germany

Zero echo time (ZTE) imaging is an established approach for three-dimensional imaging of tissues and materials with ultrashort T₂* relaxation times. An intrinsic disadvantage of this approach are missing data points within the center region of k-space due to hardware limitations. These missing points are often retrospectively interpolated or subsequently acquired using single-point imaging approaches or additional ZTE acquisitions with decreased resolutions. This abstract presents an approach that relies on the interleaved combination of ZTE read-outs with different resolutions combined with a Compressed Sensing reconstruction, to acquire more information around the k-space center, for high-quality ZTE without prolonged acquisition times.

Edwin Eduard Gert Willem ter Voert¹, Florian Wiesinger², Graeme McKinnon³, Mathias Engström⁴, Jose Fernando de Arcos⁵, Marlena Hofbauer¹, Ronny R Buechel¹, and Philipp A Kaufmann^1
1Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland, ²GE Healthcare, Munich, Germany, ³GE Healthcare, Milwaukee, WI, United States, ⁴GE Healthcare, Stockholm, Sweden, ⁵GE Healthcare, Little Chalfont, Amersham, United Kingdom

Calcifications in atherosclerotic plaques are possibly associated with worsened clinical prognosis. In contrast to the often-used CT for diagnosis, calcifications cannot easily be detected with MRI. As PET becomes a major complementary modality for MRI in plaque imaging, and as integrated PET/MR scanners become increasingly available, PET/MR based calcification screening methods are desired. With zero TE (ZTE) MR imaging it is possible to image short T2 tissues like bone. In the current study we demonstrate that ZTE imaging on PET/MR, combined with Deep Learning reconstructed ZTE, can likely be applied to detect calcifications in peripheral vasculature.

Serhat Ilbey¹, Johannes Fischer¹, Michael Bock¹, and Ali Caglar Ozen^1,2
1Dept. of Radiology, Medical Physics, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany, ²German Consortium for Translational Cancer Research Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg, Germany

PETRA is a combination of a radial zero-TE and single point imaging (SPI) acquisition, which is very silent and which can efficiently acquire MR signals with short T₂^*. In PETRA, the acquisition of SPI data constitutes a major part of the acquisition time especially for high-resolution protocols. To accelerate the SPI section while preserving the image quality, we combine SPI with compressed sensing (cs). csPETRA enables 3D imaging with isotropic sub-millimeter resolution within only a few minutes, e.g., for (0.5 mm)³ voxel-size with (20 cm)³ field-of-view, which is demonstrated with different acceleration factors for high-resolution imaging of the knee.

Sairam Geethanath^1
1Columbia MR Center, Columbia University, New York, NY, United States

This work introduces a reconstruction-only approach, dubbed “single echo reconstruction” (SER) to demonstrate (i) the first, rapid 128 x 128 MRI  without phase encoding using a 64-channel coil; (ii) significant reduction of RF power, PNS, and gradient noise; (iii) using only a commercially available coil with no external sensors (iv) comparison with gold-standard 2D spin-echo (SE) and accelerated acquisitions for $$$ T_2 $$$ weighted imaging as an application. For imaging 11 slices with TE = 80ms, the acquisition time was 1.8s with 10.8W total RF deposition, 12.09% peripheral nerve stimulation and no blurring artifacts.

Felix Glang¹, Kai Buckenmaier¹, Jonas Bause¹, Alexander Loktyushin¹, Nikolai Avdievich¹, and Klaus Scheffler^1,2
1High-field Magnetic Resonance Center, Max-Planck Institute for Biological Cybernetics, Tübingen, Germany, ²Department of Biomedical Magnetic Resonance, Eberhard Karls University Tübingen, Tübingen, Germany

In this work, it is assessed how electronically modulated time-varying receive sensitivities can improve parallel imaging reconstruction at 9.4T. The required sensitivity modulation is achieved by introducing variable capacitance diodes (varactors) in the receive loops that can be independently adjusted to modify B₁^- profiles. A prototype 4 channel receive array was built, and measured and simulated receive profiles were compared. Additionally, simulations were conducted regarding potential for g-factor improvement. It was found that potential improvements strongly depend on the B₁^- switching patterns during k-space acquisition, where strongest improvements are to be expected from fast B₁^- modulations.

Samuel Perron¹, Matthew S. Fox^1,2, Hacene Serrai¹, and Alexei Ouriadov^1,2,3
1Physics and Astronomy, The University of Western Ontario, London, ON, Canada, ²Lawson Health Research Institute, London, ON, Canada, ³School of Biomedical Engineering, The University of Western Ontario, London, ON, Canada

To produce high-SNR images, MRI systems usually employ many signal averages, expensive high field-strength coils, and/or expensive contrast agents. The proposed sampling and reconstruction method, requiring no hardware modifications, would produce images with higher SNR without increasing scan times. Nine under-sampled images are averaged for every combination of images, and the resulting SNR vs. averages function is fitted according to the Stretched-Exponential Model (SEM). The resulting reconstructed image yielded higher SNR than the original image for all three imaging schemes (FGRE, x-Centric, FE-Sectoral), demonstrating the feasibility of the proposed method for the first time.

Nicolas Arango¹, Molin Zhang¹, Jason Stockmann^2,3, Jacob White¹, and Elfar Adalsteinsson^1,4
1Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, ²A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ³Harvard Medical School, Boston, MA, United States, ⁴Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, United States

Reduced FOV imaging using ∆B₀ control is limited by magnetostatics, but careful tracking of aliasing enables the vast reduction in the deselection volume required. A 2-sided spectral approach for the deselection enables the combination of strong linear gradients and adaptable multicoil shim array ∆B₀ fields to perform selective excitation in concert. Simulations indicate potential for central volume rFOV where prior work in ∆B₀-based rFOV imaging was limited to peripheral volumes.
 

Guanhua Wang¹, Douglas C. Noll¹, and Jeffrey A. Fessler^2
1Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States, ²Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, United States

Optimization-based k-space sampling pattern design often involves the Jacobian matrix of non-uniform fast Fourier transform (NUFFT) operations. Previous works relying on auto-differentiation can be time-consuming and less accurate. This work proposes an approximation method using the relationship between exact non-uniform DFT (NDFT) and NUFFT, demonstrating improved results for the sampling pattern optimization problem.

Annalena Erbrecht¹, Enrico Pannicke¹, and Christoph Dinh^1
1Otto-von-Guericke University, Magdeburg, Germany

We want to present a CUDA based RF-receiver for a 1,5 T MRI consisting of an inverse quadrature modulation and the decimation step. We compared different decimation techniques based on a moving average, a CIC and an FIR filter. The filters were compared regarding their noise attenuation, their processing effort and their group delays. We conclude that the CIC filter is the optimal filter for our usage, because this filter provides the best compromise between noise attenuation and processing effort.

Ka-Loh Li¹, Daniel Lewis², David J Coope³, Federico Roncaroli³, Omar N Pathmanaban², Andrew T King², Sha Zhao¹, Erjon Agushi¹, Alan Jackson¹, Timothy Cootes¹, and Xiaoping Zhu^1
1Division of Informatics, Imaging and Data Sciences, The University of Manchester, Manchester, United Kingdom, ²Department of Neurosurgery, Salford Royal NHS Foundation Trust, Manchester, United Kingdom, ³Division of Neuroscience and Experimental Psychology, The University of Manchester, Manchester, United Kingdom

This study sought to evaluate the feasibility of using a low gadolinium-based contrast agent (GBCA) dose protocol with a newly developed analysis technique, the LEGATOS method, for deriving whole-brain, high-spatial resolution pharmacokinetic parameters from dual-temporal resolution (DTR) DCE-MRI. Through Monte Carlo simulations and an in vivo study incorporating histopathological data the accuracy of pharmacokinetic parameters derived using a low-dose interleaved protocol and LEGATOS was assessed.  Our results demonstrate that this approach permitted the derivation of accurate, tissue-validated high-spatial resolution kinetic parameter estimates following a single low-dose injection, representing in some patients a greater than 80% reduction in GBCA dose.

Shahrokh Abbasi-Rad¹, Martijn Cloos^1,2, Jin Jin³, Kieran O'Brien³, and Markus Barth^1,2,4
1Centre for Advanced Imaging, University of Queensland, Brisbane, Australia, ²ARC Training Centre for Innovation in Biomedical Imaging Technology, The University of Queensland, Brisbane, Australia, ³Siemens Healthcare Pty Ltd, Brisbane, Australia, ⁴School of Electrical Engineering and Information Technology, The University of Queensland, Brisbane, Australia

Ultra-high field scanners offer a potential signal-to-noise ratio (SNR) improvement for Diffusion weighted Imaging (DWI). However, the application of DWI at 7T is hindered by several technical challenges. In particular, B1+ inhomogeneity can lead to signal dropouts that degrades image quality in the temporal lobes and base of the skull. In this work, we show that embedding time-resampled frequency offset corrected inversion pulses (TR-FOCI) in a twice-refocussed spin echo DWI sequence can recover the signal in these brain areas.

Adam Berrington¹, Penny Gowland¹, and Richard Bowtell^1
1Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom

The simultaneous acquisition and separation of signals from multiple voxels using receive sensitivities can accelerate MRS acquisition. However, separation is ill-conditioned when signals are acquired from voxels with similar receive-coil sensitivities.  We propose a new approach which improves reconstruction using the transmitted RF to modulate the signals from different voxels. Simulations showed that for a small number of encoding steps, M, the g-factor of the reconstruction problem was reduced (~3-fold, M=2 for 5 regions). Reconstructed phantom data from two-voxels, acquired using phase-modulation, were of higher SNR than coil-encoding, indicating the potential of the proposed method for multi-voxel measurement in MRS.

S. T. Claus¹, Y. Eti², and E. S. Terbuny^3
1Dept. of Presents, North Pole Research Agency, Rovaniemi, Finland, ²Atopof Amountain, Himalaya, Bhutan, ³Dept. for Sweets, Greenfield Institute, Ostereistedt, Germany

Detecting  Easter bunnies is a task that is difficult to impossible for humans - thus, the use of artificial intelligence is more than warranted. In this work we present a confounded nut-work noisette (CNN) algorithm based on extended, accelerated systematic tracking in experi­mental radiology with encephalo-graphic generation (EASTER-EGG). Using this method we demonstrate that chocolate is a volatile resource especially when hungry researchers are present.