Search Our Scientific Publications & Authors

Magn Reson Med 2019 Apr 21. Epub 2019 Apr 21.

Department of Biomedical Engineering, University of Virginia Health System, Charlottesville, Virginia.

Purpose: To develop a continuous-acquisition cardiac self-gated spiral pulse sequence and a respiratory motion-compensated reconstruction strategy for free-breathing cine imaging.

Methods: Cine data were acquired continuously on a 3T scanner for 8 seconds per slice without ECG gating or breath-holding, using a golden-angle gradient echo spiral pulse sequence. Cardiac motion information was extracted by applying principal component analysis on the gridded 8 × 8 k-space center data. Read More

Magn Reson Med 2019 Apr 22. Epub 2019 Apr 22.

Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada.

Purpose: Subject motion in MRI remains an unsolved problem; motion during image acquisition may cause blurring and artifacts that severely degrade image quality. In this work, we approach motion correction as an image-to-image translation problem, which refers to the approach of training a deep neural network to predict an image in 1 domain from an image in another domain. Specifically, the purpose of this work was to develop and train a conditional generative adversarial network to predict artifact-free brain images from motion-corrupted data. Read More

Magn Reson Med 2019 Apr 21. Epub 2019 Apr 21.

School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom.

Purpose: To achieve 3D T w imaging of the prostate with 1-mm isotropic resolution in less than 3 min.

Methods: We devised and implemented a 3D T -prepared multishot balanced steady state free precession (T prep-bSSFP) acquisition sequence with a variable density undersampled trajectory combined with a total variation regularized iterative SENSE (TV-SENSE) reconstruction. Prospectively undersampled images of the prostate (acceleration factor R = 3) were acquired in 11 healthy subjects in an institutional review board-approved study. Read More

Magn Reson Med 2019 Apr 19. Epub 2019 Apr 19.

Department of Diagnostic and Interventional Radiology, Medical Faculty, Heinrich Heine University Düsseldorf, Dusseldorf, Germany.

Purpose: To characterize the proton exchange in aqueous urea solutions using a modified version of the WEX II filter at high magnetic field, and to assess the feasibility of performing quantitative urea CEST MRI on a 3T clinical MR system.

Methods: In order to study the dependence of the exchange-rate constant of urea as a function of pH and T, the WEX-spectra were acquired at 600 MHz from urea solutions in a pH range from 6.4 to 8. Read More

Magn Reson Med 2019 Apr 19. Epub 2019 Apr 19.

Institute of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Germany.

Purpose: To mitigate inhomogeneity in quantitative CEST MRI at ultra-high magnetic field strengths (B ≥ 7 Tesla) using a parallel transmit system.

Methods: Multiple interleaved mode saturation employs interleaving of 2 complementary phase sets during the saturation pulse train. Phase differences of 45° (first mode) and 90° (second mode) between 2 adjacent transmitter coil channels are used. Read More

Magn Reson Med 2019 Apr 19. Epub 2019 Apr 19.

Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany.

Purpose: 4D flow MRI permits to quantify non-invasively time-dependent velocity vector fields, but it demands long acquisition times. 2D-selective excitation allows to accelerate the acquisition by reducing the FOV in both phase encoding directions. In this study, we investigate 2D-selective excitation with reduced FOV imaging for fast 4D flow imaging while obtaining correct velocity quantification. Read More

Magn Reson Med 2019 Apr 16. Epub 2019 Apr 16.

Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel.

Purpose: To design and implement a multislice MRSI method for fast spectroscopic imaging, using a modified version of echo planar spectroscopic imaging (EPSI) that offers higher spectral width and/or shorter scan time.

Methods: Echo planar spectroscopic imaging suffers from inconsistencies between readout lines acquired with gradients of opposite signs, which has typically been addressed by reconstructing the "positive" and "negative" data sets separately and averaging the two. Nevertheless, consistency between the readout lines of each phase encode can be achieved by interposing the EPSI readouts with alternating "blipped" phase-encode gradients. Read More

Magn Reson Med 2019 Apr 16. Epub 2019 Apr 16.

Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.

Purpose: To demonstrate the feasibility of mapping gas exchange with single breath-hold hyperpolarized (HP) Xe in humans, acquiring parametric maps of lung physiology. The potential benefit of acceleration using parallel imaging for this application is also explored.

Methods: Six healthy volunteers were scanned with a modified spiral-IDEAL sequence to acquire gas exchange-weighted images using a single dose of Xe. Read More

Magn Reson Med 2019 Apr 16. Epub 2019 Apr 16.

DZHK, German Center for Cardiovascular Research, Berlin, Germany.

Purpose: Myocardial blood-flow simulation based on laws of fluid mechanics is a valuable tool for understanding tissue behavior. Our aim is to evaluate the ability of a porous-media flow model approach to reflect disturbed washout of contrast media (CM) from the myocardium as observed by cardiovascular MR.

Methods: A coupled advection-diffusion model is used to describe the CM flow in the vascular and extravascular space as separate compartments. Read More

Magn Reson Med 2019 Apr 16. Epub 2019 Apr 16.

National Magnetic Resonance Research Center (UMRAM), Bilkent University, Bilkent, Ankara, Turkey.

Purpose: In contrast to conventional linear gradients, gradient coil arrays with arbitrary spatial dependency might experience strong mutual coupling. Although conventional gradient power amplifiers with feedback loop might compensate the effect of coupling, required voltages for the compensation are generally unknown and has to be considered beforehand to ensure that amplifier voltage limits are not exceeded. A first-order circuit model is proposed to be used as a feedforward model which enables analytical formulas of required voltages to drive the mutually coupled gradient coil arrays. Read More

Magn Reson Med 2019 Apr 10. Epub 2019 Apr 10.

Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Collaborative Innovation Center of Chemistry for Life Sciences, Wuhan Institute of Physics and Mathematics-Wuhan National Laboratory for Optoelectronics, Chinese Academy of Sciences, Wuhan, People's Republic of China.

Purpose: CEST has become a preeminent technology for the rapid detection and grading of tumors, securing its widespread use in both laboratory and clinical research. However, many existing CEST MRI agents exhibit a sensitivity limitation due to small chemical shifts between their exchangeable protons and water. We propose a new group of CEST MRI agents, free-base porphyrins and chlorin, with large exchangeable proton chemical shifts from water for enhanced detection. Read More

Magn Reson Med 2019 Apr 8. Epub 2019 Apr 8.

Biomedical Engineering, Stony Brook University, Stony Brook, New York.

Purpose: Radiomics allows for powerful data-mining and feature extraction techniques to guide clinical decision making. Image segmentation is a necessary step in such pipelines and different techniques can significantly affect results. We demonstrate that a convolutional neural network (CNN) segmentation method performs comparably to expert manual segmentations in an established radiomics pipeline. Read More

Magn Reson Med 2019 Apr 8. Epub 2019 Apr 8.

Department of Radiology, The Ohio State University Wexner Medical Center, Columbus, Ohio.

Purpose: Noninvasive measurement of mechanical properties of brain tissue using magnetic resonance elastography (MRE) has been a promising method for investigating neurologic disorders such as multiple sclerosis, hydrocephalus, and Alzheimer's. However, because of the regional and directional dependency of brain stiffness, estimating anisotropic stiffness is important. This study investigates isotropic and anisotropic stiffness as a function of age as well as the correlation between isotropic and anisotropic stiffness. Read More

Magn Reson Med 2019 Apr 7. Epub 2019 Apr 7.

Department of Radiology, National Taiwan University College of Medicine, Taipei, Taiwan.

Purpose: The purpose of this study was to investigate the feasibility of in vivo imaging of human pancreatic ductal cells by OATP1B3 reporter gene under MRI.

Methods: A human cell line (PANC-1) derived from the pancreatic ductal epithelium was used in this study. After transduction of OATP1B3, the cellular physiological functions and the ability of intracellular uptake of the MRI contrast medium (Gd-EOB-DTPA) were examined. Read More

Magn Reson Med 2019 Apr 7. Epub 2019 Apr 7.

University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute for Diagnostic and Interventional Radiology, Cologne, Germany.

Purpose: Respiration induces temporal variations of the main magnetic field B along the spinal cord. These variations are typically not compensated for in velocity quantifications using phase-contrast MRI. The goal of this study was to analyze errors caused by respiration-induced B variations in real-time phase-contrast echo planar imaging (PCEPI) of cervical cerebrospinal fluid (CSF) velocity measurements and to evaluate this effect for various sequence parameters using numerical simulations. Read More

Magn Reson Med 2019 Apr 7. Epub 2019 Apr 7.

High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.

Purpose: To improve the receive (Rx) performance of a human head transceiver (TxRx) array at 9.4T without compromising its transmit (Tx) performance, a novel 16-element array was developed, constructed, and tested.

Methods: We designed and constructed a phased array, which consists of 8 TxRx surface loops placed in a single row and circumscribing a head, and 8 Rx-only short folded dipole antennas. Read More

Magn Reson Med 2019 Apr 5. Epub 2019 Apr 5.

Division of MRI Research, Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts.

Purpose: To improve image quality and spatial coverage for abdominal perfusion imaging by implementing an arterial spin labeling (ASL) sequence that combines variable-density 3D fast-spin-echo (FSE) with Cartesian trajectory and compressed-sensing (CS) reconstruction.

Methods: A volumetric FSE sequence was modified to include background-suppressed pseudo-continuous ASL labeling and to support variable-density (VD) Poisson-disk sampling for acceleration. We additionally explored the benefits of center oversampling and variable outer k-space sampling. Read More

Magn Reson Med 2019 Apr 1. Epub 2019 Apr 1.

High Field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria.

Purpose: Inhomogeneities in the static magnetic field (B ) deteriorate MRSI data quality by lowering the spectral resolution and SNR. MRSI with low spatial resolution is also prone to lipid bleeding. These problems are increasingly problematic at ultra-high fields. Read More

Magn Reson Med 2019 Mar 29. Epub 2019 Mar 29.

Division of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany.

Purpose: Relaxation-compensated CEST-MRI (i.e., the inverse metrics magnetization transfer ratio and apparent exchange-dependent relaxation) has already been shown to provide valuable information for brain tumor diagnosis at ultrahigh magnetic field strengths. Read More

Magn Reson Med 2019 Mar 29. Epub 2019 Mar 29.

King's College London, School of Biomedical Engineering and Imaging Sciences, London, United Kingdom.

Purpose: To develop a framework for respiratory motion-corrected 3D whole-heart water/fat coronary MR angiography (CMRA) at 3T with reduced and predictable scan time.

Methods: A 3D dual-echo acquisition and respiratory motion-corrected reconstruction framework for water/fat CMRA imaging was developed. The acquisition sequence integrates a 2D dual-echo image navigator (iNAV), enabling 100% respiratory scan efficiency. Read More

Magn Reson Med 2019 Mar 30. Epub 2019 Mar 30.

Center of Functionally Integrative Neuroscience, Aarhus University, Denmark.

Purpose: Some advanced RF pulses, like multidimensional RF pulses, are often long and require substantial computation time because of a number of constraints and requirements, sometimes hampering clinical use. However, the pulses offer opportunities of reduced-FOV imaging, regional flip-angle homogenization, and localized spectroscopy, e.g. Read More

Magn Reson Med 2019 Mar 29. Epub 2019 Mar 29.

Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco.

Purpose: To compare the performance of an 8-channel surface coil/clamshell transmitter and 32-channel head array coil/birdcage transmitter for hyperpolarized C brain metabolic imaging.

Methods: To determine the field homogeneity of the radiofrequency transmitters, B + mapping was performed on an ethylene glycol head phantom and evaluated by means of the double angle method. Using a 3D echo-planar imaging sequence, coil sensitivity and noise-only phantom data were acquired with the 8- and 32-channel receiver arrays, and compared against data from the birdcage in transceiver mode. Read More

Magn Reson Med 2019 Mar 29. Epub 2019 Mar 29.

Advanced Imaging Research Center, Oregon Health & Science University, Portland, Oregon.

Magn Reson Med 2019 Mar 28. Epub 2019 Mar 28.

High Field MR Center, Department of Biomedical Imaging and Image-Guided Therapy, Medical University Vienna, Vienna, Austria.

Purpose: To assess the performance, in the presence of scanner instabilities, of three dynamic correction methods which integrate ∆B mapping into the chemical exchange saturation transfer (CEST) measurement and three established static ∆B -correction approaches.

Methods: A homogeneous phantom and five healthy volunteers were scanned with a CEST sequence at 7 T. The in vivo measurements were performed twice: first with unaltered system frequency and again applying frequency shifts during the CEST acquisition. Read More

Magn Reson Med 2019 Mar 28. Epub 2019 Mar 28.

Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee.

Purpose: To measure the transverse relaxation time in healthy human cervical spinal cord gray matter (GM) and white matter (WM) at 3T.

Methods: Thirty healthy volunteers were recruited. Axial images were acquired using an averaged multi-echo gradient-echo (mFFE) -weighted sequence with 5 echoes. Read More

Magn Reson Med 2019 Mar 28. Epub 2019 Mar 28.

Department of Radiology, Northwestern University, Chicago, Illinois.

Purpose: This study evaluated the feasibility of using 4D flow MRI and a semi-automated analysis tool to assess the hemodynamic impact of intracranial atherosclerotic disease (ICAD). The ICAD impact was investigated by evaluating pressure drop (PD) at the atherosclerotic stenosis and changes in cerebral blood flow distribution in patients compared to healthy controls.

Methods: Dual-venc 4D flow MRI was acquired in 25 healthy volunteers and 16 ICAD patients (ICA, N = 3; MCA, N = 13) with mild (<50%), moderate (50-69%), or severe (>70%) intracranial stenosis. Read More

Magn Reson Med 2019 Mar 28. Epub 2019 Mar 28.

Erwin L. Hahn Institute for MR Imaging, University of Duisburg-Essen, Essen, Germany.

Purpose: A 16-channel receive (16Rx) radiofrequency (RF) array for 7T ultra-high field body MR imaging is presented. The coil is evaluated in conjunction with a 16-channel transmit/receive (16TxRx) coil and additionally with a 32-channel transmit/receive (32TxRx) remote body coil for RF transmit and serving as receive references.

Methods: The 16Rx array consists of 16 octagonal overlapping loops connected to custom-built detuning boards with preamplifiers. Read More

Magn Reson Med 2019 Mar 28. Epub 2019 Mar 28.

Department of Radiology and Biomedical Imaging, University of California, San Francisco, California.

Purpose: Image-guided prostate biopsies are routinely acquired in the diagnosis and treatment monitoring of prostate cancer, yielding useful tissue for identifying metabolic biomarkers and therapeutic targets. We developed an optimized biopsy tissue culture protocol in combination with [1,6- C ]glucose labeling and quantitative high-resolution NMR to measure glycolysis and tricarboxcylic acid (TCA) cycle activity in freshly acquired living human prostate biopsies.

Methods: We acquired 34 MRI-ultrasound fusion-guided prostate biopsies in vials on ice from 22 previously untreated patients. Read More

Magn Reson Med 2019 Mar 28. Epub 2019 Mar 28.

Molecular and Clinical Sciences, St George's University of London, London, England.

Proton MRS ( H MRS) provides noninvasive, quantitative metabolite profiles of tissue and has been shown to aid the clinical management of several brain diseases. Although most modern clinical MR scanners support MRS capabilities, routine use is largely restricted to specialized centers with good access to MR research support. Widespread adoption has been slow for several reasons, and technical challenges toward obtaining reliable good-quality results have been identified as a contributing factor. Read More

Magn Reson Med 2019 Mar 28. Epub 2019 Mar 28.

Ming Hsieh Department of Electrical and Computer Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, California.

Purpose: To demonstrate a tagging method compatible with RT-MRI for the study of speech production.

Methods: Tagging is applied as a brief interruption to a continuous real-time spiral acquisition. Tagging can be initiated manually by the operator, cued to the speech stimulus, or be automatically applied with a fixed frequency. Read More

Magn Reson Med 2019 Mar 22. Epub 2019 Mar 22.

Advanced Imaging Research Center, Oregon Health & Science University, Portland, Oregon.

Purpose: The desire to quantitatively discriminate the extra- and intracellular tissue H O MR signals has gone hand-in-hand with the continual, historic increase in MRI instrument magnetic field strength [B ]. However, recent studies have indicated extremely valuable, novel metabolic information can be readily accessible at ultra-low B . The two signals can be distinguished, and the homeostatic activity of the cell membrane sodium/potassium pump (Na ,K ,ATPase) detected. Read More

Magn Reson Med 2019 Mar 21. Epub 2019 Mar 21.

Department of Radiology and Nuclear Medicine, Radboud university medical center, Nijmegen, The Netherlands.

Purpose: To demonstrate a H/ P whole human brain volume coil configuration for 3 Tesla with separate P transmit and receive components that maintains H MRS performance and delivers optimal P MRSI with H decoupling.

Methods: We developed an 8-channel P receive array coil covering the head to be used as an insert for a commercial double-tuned H/ P birdcage transmit-receive coil. This retains the possibility of using low-power rectangular pulses for H-decoupled 3D P MRSI (nominal resolution 17. Read More

Magn Reson Med 2019 Mar 21. Epub 2019 Mar 21.

School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom.

Purpose: To develop a motion-corrected 3D flow-insensitive imaging approach interleaved T prepared-inversion recovery (iT prep-IR) for simultaneous lumen and wall visualization of the great thoracic vessels and cardiac structures.

Methods: A 3D flow-insensitive approach for simultaneous cardiovascular lumen and wall visualization (iT prep) has been previously proposed. This approach requires subject-dependent weighted subtraction to completely null the arterial blood signal in the black-blood volume. Read More

Magn Reson Med 2019 Mar 20. Epub 2019 Mar 20.

Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom.

Purpose: Phosphorus spectroscopy can differentiate among liver disease stages and types. To quantify absolute concentrations of phosphorus metabolites, sensitivity calibration and transmit field ( ) correction are required. The trend toward ultrahigh fields (7 T) and the use of multichannel RF coils makes this ever more challenging. Read More

Magn Reson Med 2019 Mar 18. Epub 2019 Mar 18.

Centre for Medical Image Computing and Department of Computer Science, University College London, London, United Kingdom.

Purpose: A combined diffusion-relaxometry MR acquisition and analysis pipeline for in vivo human placenta, which allows for exploration of coupling between and apparent diffusion coefficient (ADC) measurements in a sub 10-minute scan time.

Methods: We present a novel acquisition combining a diffusion prepared spin echo with subsequent gradient echoes. The placentas of 17 pregnant women were scanned in vivo, including both healthy controls and participants with various pregnancy complications. Read More

Magn Reson Med 2019 Mar 18. Epub 2019 Mar 18.

Radiology, Medical College of Wisconsin, Milwaukee, Wisconsin.

Purpose: Due to host-mediated adverse reaction to metallic debris, there is an increasing need for noninvasive assessment of the soft tissue surrounding large joint arthroplasties. Quantitative mapping can be beneficial for tissue characterization and early diagnosis of tissue pathology but current mapping techniques lack the capability to image near metal hardware. A novel multi-spectral mapping technique is proposed to address this unmet need. Read More

Magn Reson Med 2019 Mar 18. Epub 2019 Mar 18.

Institute of Neuroscience and Medicine (INM-4), Forschungszentrum Jülich, Jülich, Germany.

Purpose: To overcome existing challenges in dynamic B shimming by implementing a shim optimization algorithm which limits shim current amplitudes and their temporal variation through the application of constraints and regularization terms.

Theory And Methods: Spherical harmonic dynamic B shimming is complicated by eddy currents, ill-posed optimizations, and the need for strong power supplies. Based on the fact that eddy current amplitudes are proportional to the magnitude of the shim current changes, and assuming a smoothness of the B inhomogeneity variation in the slice direction, a novel algorithm was implemented to reduce eddy current generation by limiting interslice shim current changes. Read More

Magn Reson Med 2019 Mar 18. Epub 2019 Mar 18.

Helen Wills Neuroscience Institute, University of California, Berkeley, California.

Purpose: To develop a novel, simultaneous multi-slice (SMS) reconstruction that extends an inter-slice leakage constraint to intra-slice aliasing with a virtual slice concept for artifact reduction.

Methods: Inter-slice leakage constraint has been used for SMS reconstruction that mitigates leakage artifacts from the adjacent slices. In this work, the leakage constraint is extended to more general framework that includes SMS and parallel MRI as special cases by viewing intra-slice aliasing artifacts from undersampling as virtual slices while imposing data fidelity to ensure the measurement consistency. Read More

Magn Reson Med 2019 Mar 18. Epub 2019 Mar 18.

Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, Republic of Korea.

Purpose: To propose a novel 3D ultrafast gradient echo-based MRI method, dubbed RASE, using quadratic-phase encoding.

Theory And Methods: Several characteristics of RASE, including spin behaviors, spatial resolution, SNR, and reduction of susceptibility-induced signal loss, were analytically described. A way of compensating for TE variation was suggested in the quadratic phase-encoding direction. Read More

Magn Reson Med 2019 Mar 18. Epub 2019 Mar 18.

Medical Imaging, University of Arizona, Tucson, Arizona.

Purpose: To design a pulse sequence for efficient 3D T2-weighted imaging and T2 mapping.

Methods: A stack-of-stars turbo spin echo pulse sequence with variable refocusing flip angles and a flexible pseudorandom view ordering is proposed for simultaneous T2-weighted imaging and T2 mapping. An analytical framework is introduced for the selection of refocusing flip angles to maximize relative tissue contrast while minimizing T2 estimation errors and maintaining low specific absorption rate. Read More

Magn Reson Med 2019 Mar 18. Epub 2019 Mar 18.

Center for Image Sciences, University Medical Center Utrecht, Utrecht, the Netherlands.

Purpose: For free-breathing renal perfusion imaging using arterial spin labeling (ASL), retrospective image realignment has been found essential to reduce subtraction artifacts and, independently, background suppression has been demonstrated to reduce physiologic noise. However, negative results on ASL precision and accuracy have been reported for the combination of both. In this study, the effect of background suppression -level in combination with image registration on free-breathing renal ASL signal quality, with registration either on ASL-images themselves or guided by additionally acquired fat-images, was investigated. Read More

Magn Reson Med 2019 Mar 18. Epub 2019 Mar 18.

Center for Brain Imaging Science and Technology, Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrumental Science, Zhejiang University, Hangzhou, Zhejiang, China.

Purpose: To develop a fast, sub-millimeter 3D magnetic resonance fingerprinting (MRF) technique for whole-brain quantitative scans.

Methods: An acquisition trajectory based on multi-axis spiral projection imaging (maSPI) was implemented for 3D MRF with steady-state precession and slab excitation. By appropriately assigning the in-plane and through-plane rotations of spiral interleaves in a novel acquisition scheme, an maSPI-based acquisition was implemented, and the total acquisition time was reduced by up to a factor of 8 compared to stack-of-spiral (SOS)-based acquisition. Read More

Magn Reson Med 2019 Mar 15. Epub 2019 Mar 15.

Perspectum Diagnostics Ltd, Oxford, United Kingdom.

Purpose: To develop a postprocessing algorithm for multiecho chemical-shift encoded water-fat separation that estimates proton density fat fraction (PDFF) maps over the full dynamic range (0-100%) using multipeak fat modeling and multipoint search optimization. To assess its accuracy, reproducibility, and agreement with state-of-the-art complex-based methods, and to evaluate its robustness to artefacts in abdominal PDFF maps.

Methods: We introduce MAGO (MAGnitude-Only), a magnitude-based reconstruction that embodies multipeak liver fat spectral modeling and multipoint optimization, and which is compatible with asymmetric echo acquisitions. Read More

Magn Reson Med 2019 Mar 15. Epub 2019 Mar 15.

Michigan State University, Department of Radiology, East Lansing, Michigan.

Purpose: While rodents are the primary animal models for contrast agent evaluation, rodents can potentially misrepresent human organ clearance of newly developed contrast agents. For example, gadolinium (Gd)-BOPTA has ~50% hepatic clearance in rodents, but ~5% in humans. This study demonstrates the benefit of chimeric mice expressing human hepatic OATPs (organic anion-transporting polypeptides) to improve evaluation of novel contrast agents for clinical use. Read More

Magn Reson Med 2019 Mar 13. Epub 2019 Mar 13.

Centre for Computational Imaging & Simulation Technologies in Biomedicine (CISTIB) and Leeds Institute for Cardiac and Metabolic Medicine (LICAMM), School of Computing & School of Medicine, University of Leeds, Leeds, United Kingdom.

Purpose: Biophysical tissue models are increasingly used in the interpretation of diffusion MRI (dMRI) data, with the potential to provide specific biomarkers of brain microstructural changes. However, it has been shown recently that, in the general Standard Model, parameter estimation from dMRI data is ill-conditioned even when very high b-values are applied. We analyze this issue for the Neurite Orientation Dispersion and Density Imaging with Diffusivity Assessment (NODDIDA) model and demonstrate that its extension from single diffusion encoding (SDE) to double diffusion encoding (DDE) resolves the ill-posedness for intermediate diffusion weightings, producing an increase in accuracy and precision of the parameter estimation. Read More

Magn Reson Med 2019 Mar 12. Epub 2019 Mar 12.

Department of Biomedical Sciences, Seoul National University, Seoul, Korea.

Purpose: To develop a robust method for brain metabolite quantification in proton magnetic resonance spectroscopy ( H-MRS) using a convolutional neural network (CNN) that maps in vivo brain spectra that are typically degraded by low SNR, line broadening, and spectral baseline into noise-free, line-narrowed, baseline-removed intact metabolite spectra.

Methods: A CNN was trained (n = 40 000) and tested (n = 5000) on simulated brain spectra with wide ranges of SNR (6.90-20. Read More

Magn Reson Med 2019 Mar 12. Epub 2019 Mar 12.

Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China.

Purpose: To develop a method based on fat-water transition region extraction (TREE) for robust fat-water separation and quantification in challenging scenarios, including low signal-to-noise ratio (SNR), fast changing B field, and disjointed anatomies.

Theory And Methods: In TREE method, the phasor solutions of each pixel were categorized into fat-dominant and water-dominant groups. The fat-water transition region was then extracted by detecting sudden changes in the phasor maps. Read More

Magn Reson Med 2019 Mar 12. Epub 2019 Mar 12.

Psychotic Disorders Division, McLean Hospital, Harvard Medical School, Belmont, Massachusetts.

Purpose: Glutamate (Glu) is the most abundant neurotransmitter in the human central nervous system and glutamatergic neurotransmission has been implicated in many common and severe neuropsychiatric disorders. In vivo MRS techniques have been developed to measure brain Glu concentration to investigate the pathophysiology of various brain disorders. However, it is difficult to interpret Glu signal changes because Glu plays multiple roles in the brain and is found in multiple microenvironments including cytosolic, vesicular, and extracellular. Read More

Magn Reson Med 2019 Mar 12. Epub 2019 Mar 12.

Department of Biomedical Engineering, Tel Aviv University, Tel Aviv, Israel.

Purpose: Multi-echo spin-echo (MESE) protocol is the most effective tool for mapping T relaxation in vivo. Still, MESE extensive use of radiofrequency pulses causes magnetization transfer (MT)-related bias of the water signal, instigated by the presence of macromolecules (MMP). Here, we analyze the effects of MT on MESE signal, alongside their impact on quantitative T measurements. Read More

Magn Reson Med 2019 Mar 12. Epub 2019 Mar 12.

Department of Electrical and Computer Engineering, The University of Iowa, Iowa City, Iowa.

Purpose: To introduce a novel framework to combine deep-learned priors along with complementary image regularization penalties to reconstruct free breathing & ungated cardiac MRI data from highly undersampled multi-channel measurements.

Methods: Image recovery is formulated as an optimization problem, where the cost function is the sum of data consistency term, convolutional neural network (CNN) denoising prior, and SmooThness regularization on manifolds (SToRM) prior that exploits the manifold structure of images in the dataset. An iterative algorithm, which alternates between denoizing of the image data using CNN and SToRM, and conjugate gradients (CG) step that minimizes the data consistency cost is introduced. Read More