10,873 results match your criteria Magnetic Resonance in Medicine[Journal]


A new electron paramagnetic resonance device to measure transcutaneous oxygen in humans.

Magn Reson Med 2019 Feb 13. Epub 2019 Feb 13.

Sports Medicine, University Hospital Center of Angers, Angers, France.

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http://dx.doi.org/10.1002/mrm.27618DOI Listing
February 2019

Application of SPOT chip for transcutaneous oximetry.

Magn Reson Med 2019 Feb 13. Epub 2019 Feb 13.

Departments of Radiology, Geisel School of Medicine, Dartmouth College, Lebanon, NH.

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http://dx.doi.org/10.1002/mrm.27667DOI Listing
February 2019

Patient specific prospective respiratory motion correction for efficient, free-breathing cardiovascular MRI.

Magn Reson Med 2019 Feb 14. Epub 2019 Feb 14.

Biomedical Engineering, The Ohio State University, Columbus, Ohio.

Purpose: To develop a patient-specific respiratory motion correction technique with true 100% acquisition efficiency.

Methods: A short training scan consisting of a series of single heartbeat images, each acquired with a preceding diaphragmatic navigator, was performed to fit a model relating the patient-specific 3D respiratory motion of the heart-to-diaphragm position. The resulting motion model was then used to update the imaging plane in real-time to correct for translational motion based on respiratory position provided by the navigator. Read More

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http://dx.doi.org/10.1002/mrm.27681DOI Listing
February 2019

Radial streak artifact reduction using phased array beamforming.

Magn Reson Med 2019 Feb 12. Epub 2019 Feb 12.

Department of Electrical and Computer Engineering, University of Arizona, Tucson, Arizona.

Purpose: A new method for streak artifact reduction in radial MRI based on phased array filtering.

Theory: Radial imaging in applications that require large fields-of-view can be susceptible to streaking artifacts due to gradient nonlinearities. Coil removal methods prune the coils contributing the most to streaking artifacts at the expense of signal loss. Read More

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http://dx.doi.org/10.1002/mrm.27689DOI Listing
February 2019

Radiofrequency phase encoded half-pulses in simultaneous multislice ultrashort echo time imaging.

Magn Reson Med 2019 Feb 12. Epub 2019 Feb 12.

Department of Medicine, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii.

Purpose: To describe a simultaneous multislice (SMS) ultrashort echo time (UTE) imaging method using radiofrequency phase encoded half-pulses in combination with power independent of number of slices (PINS) inversion recovery (IR) pulses to generate multiple-slice images with short T * contrasts in less than 3 min with close to an eightfold acceleration compared with a standard 2D approach.

Theory And Methods: Radiofrequency phase encoding is applied in an SMS (N = 4) excitation scheme using "sinc" half-pulses. With the use of coil sensitivity encoding (SENSE) and controlled aliasing in parallel imaging (CAIPI) in combination with a gradient echo 2D spiral readout trajectory and IR PINS pulses for contrast enhancement a fast UTE sequence is developed. Read More

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http://dx.doi.org/10.1002/mrm.27693DOI Listing
February 2019

Measurement of microvascular cerebral blood volume changes over the cardiac cycle with ferumoxytol-enhanced T MRI.

Magn Reson Med 2019 Feb 12. Epub 2019 Feb 12.

Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.

Purpose: This feasibility study investigates the non-invasive measurement of microvascular cerebral blood volume (BV) changes over the cardiac cycle using cardiac-gated, ferumoxytol-enhanced MRI.

Methods: Institutional review board approval was obtained and all subjects provided written informed consent. Cardiac gated MR scans were prospectively acquired on a 3. Read More

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http://dx.doi.org/10.1002/mrm.27670DOI Listing
February 2019

Cerebral blood volume mapping using Fourier-transform-based velocity-selective saturation pulse trains.

Magn Reson Med 2019 Feb 8. Epub 2019 Feb 8.

Department of Radiology, Zhujiang Hospital, Southern Medical University, Guangzhou, China.

Purpose: Velocity-selective saturation (VSS) pulse trains provide a viable alternative to the spatially selective methods for measuring cerebral blood volume (CBV) by reducing the sensitivity to arterial transit time. This study is to compare the Fourier-transform-based velocity-selective saturation (FT-VSS) pulse trains with the conventional flow-dephasing VSS techniques for CBV quantification.

Methods: The proposed FT-VSS label and control modules were compared with VSS pulse trains utilizing double refocused hyperbolic tangent (DRHT) and 8-segment B1-insensitive rotation (BIR-8). Read More

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http://doi.wiley.com/10.1002/mrm.27668
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http://dx.doi.org/10.1002/mrm.27668DOI Listing
February 2019
2 Reads

Dynamic P spectroscopic imaging of skeletal muscles combining flyback echo-planar spectroscopic imaging and compressed sensing.

Magn Reson Med 2019 Feb 8. Epub 2019 Feb 8.

School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada.

Purpose: Dynamic phosphorus MR spectroscopic imaging ( P-MRSI) experiments require temporal resolution on the order of seconds to concurrently assess different muscle groups. A highly accelerated pulse sequence combining flyback echo-planar spectroscopic imaging (EPSI) and compressed sensing was developed and tested in a phantom and healthy humans during an exercise-recovery challenge of the lower leg muscles, using a clinical 3T MRI.

Methods: A flyback EPSI readout designed to achieve 2. Read More

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http://doi.wiley.com/10.1002/mrm.27682
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http://dx.doi.org/10.1002/mrm.27682DOI Listing
February 2019
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A black-blood ultra-short echo time (UTE) sequence for 3D isotropic resolution imaging of the lungs.

Magn Reson Med 2019 Feb 8. Epub 2019 Feb 8.

Adult CF unit, Neuchatelois-Pourtales Hospital, Neuchatel, Switzerland.

Purpose: Ultra-short echo time MRI is a promising alternative to chest CT for cystic fibrosis patients. Black-blood imaging in particular could help discern small-sized anomalies, such as mucoid plugging, which may otherwise be confused with neighboring blood vessels, particularly when contrast agent is not used. We, therefore, implemented and tested an ultra-short echo time sequence with black-blood preparation. Read More

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http://dx.doi.org/10.1002/mrm.27679DOI Listing
February 2019
1 Read

Absolute quantitative MR perfusion and comparison against stable-isotope microspheres.

Magn Reson Med 2019 Feb 8. Epub 2019 Feb 8.

Department of Radiology, University of Chicago, Chicago, Illinois.

Purpose: This work sought to compare a quantitative T bookend dynamic susceptibility contrast MRI based perfusion protocol for absolute cerebral blood flow (qCBF) against CBF measured by the stable-isotope neutron capture microsphere method, a recognized reference standard for measuring tissue blood flow, at normocapnia, hypercapnia, and in acute stroke.

Methods: CBF was measured in anesthetized female canines by MRI and microspheres over 2 consecutive days for each case. On day 1, 5 canines were measured before and during a physiological challenge induced by carbogen inhalation; on day 2, 4 canines were measured following permanent occlusion of the middle cerebral artery. Read More

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http://dx.doi.org/10.1002/mrm.27669DOI Listing
February 2019
1 Read

Development and clinical implementation of SeedNet: A sliding-window convolutional neural network for radioactive seed identification in MRI-assisted radiosurgery (MARS).

Magn Reson Med 2019 Feb 8. Epub 2019 Feb 8.

Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, Texas.

Purpose: To develop and evaluate a sliding-window convolutional neural network (CNN) for radioactive seed identification in MRI of the prostate after permanent implant brachytherapy.

Methods: Sixty-eight patients underwent prostate cancer low-dose-rate (LDR) brachytherapy using radioactive seeds stranded with positive contrast MR-signal seed markers and were scanned using a balanced steady-state free precession pulse sequence with and without an endorectal coil (ERC). A sliding-window CNN algorithm (SeedNet) was developed to scan the prostate images using 3D sub-windows and to identify the implanted radioactive seeds. Read More

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http://dx.doi.org/10.1002/mrm.27677DOI Listing
February 2019

A method for correcting breathing-induced field fluctuations in T2*-weighted spinal cord imaging using a respiratory trace.

Magn Reson Med 2019 Feb 8. Epub 2019 Feb 8.

Wellcome Centre for Integrative Neuroimaging, FMRIB, Department of Clinical Neurosciences, University of Oxford, Oxford, UK.

Purpose: Spinal cord MRI at ultrahigh field is hampered by time-varying magnetic fields associated with the breathing cycle, giving rise to ghosting artifacts in multi-shot acquisitions. Here, we suggest a correction approach based on linking the signal from a respiratory bellows to field changes inside the spinal cord. The information is used to correct the data at the image reconstruction level. Read More

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http://dx.doi.org/10.1002/mrm.27664DOI Listing
February 2019

Accuracy and precision of electrical permittivity mapping at 3T: the impact of three mapping techniques.

Magn Reson Med 2019 Feb 8. Epub 2019 Feb 8.

Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands.

Purpose: To investigate the sequence-specific impact of amplitude mapping on the accuracy and precision of permittivity reconstruction at 3T in the pelvic region.

Methods: maps obtained with actual flip angle imaging (AFI), Bloch-Siegert (BS), and dual refocusing echo acquisition mode (DREAM) sequences, set to a clinically feasible scan time of 5 minutes, were compared in terms of accuracy and precision with electromagnetic and Bloch simulations and MR measurements. Permittivity maps were reconstructed based on these maps with Helmholtz-based electrical properties tomography. Read More

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http://doi.wiley.com/10.1002/mrm.27675
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http://dx.doi.org/10.1002/mrm.27675DOI Listing
February 2019
1 Read

Sparsity and locally low rank regularization for MR fingerprinting.

Magn Reson Med 2019 Feb 5. Epub 2019 Feb 5.

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

Purpose: Develop a sparse and locally low rank (LLR) regularized reconstruction to accelerate MR fingerprinting (MRF).

Methods: Recent works have introduced low rank reconstructions to MRF, based on temporal compression operators learned from the MRF dictionary. In other MR applications, LLR regularization has been introduced to exploit temporal redundancy in local regions of the image. Read More

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https://onlinelibrary.wiley.com/doi/abs/10.1002/mrm.27665
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http://dx.doi.org/10.1002/mrm.27665DOI Listing
February 2019
1 Read

Evaluation of principal component analysis image denoising on multi-exponential MRI relaxometry.

Magn Reson Med 2019 Feb 5. Epub 2019 Feb 5.

Champalimaud Centre for the Unknown, Lisbon, Portugal.

Purpose: Multi-exponential relaxometry is a powerful tool for characterizing tissue, but generally requires high image signal-to-noise ratio (SNR). This work evaluates the use of principal-component-analysis (PCA) denoising to mitigate these SNR demands and improve the precision of relaxometry measures.

Methods: PCA denoising was evaluated using both simulated and experimental MRI data. Read More

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http://dx.doi.org/10.1002/mrm.27658DOI Listing
February 2019

Echo planar time-resolved imaging (EPTI).

Magn Reson Med 2019 Feb 3. Epub 2019 Feb 3.

Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts.

Purpose: To develop an efficient distortion- and blurring-free multi-shot EPI technique for time-resolved multiple-contrast and/or quantitative imaging.

Methods: EPI is a commonly used sequence but suffers from geometric distortions and blurring. Here, we introduce a new multi-shot EPI technique termed echo planar time-resolved imaging (EPTI), which has the ability to rapidly acquire distortion- and blurring-free multi-contrast data set. Read More

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http://dx.doi.org/10.1002/mrm.27673DOI Listing
February 2019

Automated selection of myocardial inversion time with a convolutional neural network: Spatial temporal ensemble myocardium inversion network (STEMI-NET).

Magn Reson Med 2019 Feb 3. Epub 2019 Feb 3.

Department of Radiology, University of California, San Diego, California.

Purpose: Delayed enhancement imaging is an essential component of cardiac MRI, which is used widely for the evaluation of myocardial scar and viability. The selection of an optimal inversion time (TI) or null point (TI ) to suppress the background myocardial signal is required. The purpose of this study was to assess the feasibility of automated selection of TI using a convolutional neural network (CNN). Read More

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http://dx.doi.org/10.1002/mrm.27680DOI Listing
February 2019
1 Read

Low-rank plus sparse compressed sensing for accelerated proton resonance frequency shift MR temperature imaging.

Magn Reson Med 2019 Jan 31. Epub 2019 Jan 31.

Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee.

Purpose: To improve multichannel compressed sensing (CS) reconstruction for MR proton resonance frequency (PRF) shift thermography, with application to MRI-induced RF heating evaluation and MR guided high intensity focused ultrasound (MRgFUS) temperature monitoring.

Methods: A new compressed sensing reconstruction is proposed that enforces joint low rank and sparsity of complex difference domain PRF data between post heating and baseline images. Validations were performed on 4 retrospectively undersampled dynamic data sets in PRF applications, by comparing the proposed method to a previously described L and total variation- (TV-) based CS approach that also operates on complex difference domain data, and to a conventional low rank plus sparse (L+S) separation-based CS reconstruction applied to the original domain data. Read More

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http://dx.doi.org/10.1002/mrm.27666DOI Listing
January 2019

The effect of flow on blood oxygen level dependent ( ) MRI of orthotopic lung tumors.

Magn Reson Med 2019 Jan 30. Epub 2019 Jan 30.

Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas.

Purpose: Blood oxygen level dependent (BOLD) MRI based on measurements can provide insights into tumor vascular oxygenation. However, measurements are susceptible to blood flow, which may vary accompanying a hyperoxic gas challenge. We investigated flow sensitivity by comparing measurements with and without flow suppression (fs) in 2 orthotopic lung xenograft tumor models. Read More

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http://dx.doi.org/10.1002/mrm.27661DOI Listing
January 2019
4 Reads

Improved chemical exchange saturation transfer imaging with real-time frequency drift correction.

Magn Reson Med 2019 Jan 30. Epub 2019 Jan 30.

Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China.

Purpose: To investigate the effects of frequency drift on chemical exchange saturation transfer (CEST) imaging at 3T, and to propose a new sequence for correcting artifacts attributed to B drift in real time.

Theory And Methods: A frequency-stabilized CEST (FS-CEST) imaging sequence was proposed by adding a frequency stabilization module to the conventional non-frequency-stabilized CEST (NFS-CEST) sequence, which consisted of a small tip angle radiofrequency excitation pulse and readout of three non-phase-encoded k-space lines. Experiments were performed on an egg white phantom and 26 human subjects on a heavy-duty clinical scanner, in order to compare the difference of FS-CEST and NFS-CEST sequences for generating the z-spectrum, magnetization transfer ratio asymmetry (MTR ) spectrum, and amide proton transfer weighted (APTw) image. Read More

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http://dx.doi.org/10.1002/mrm.27663DOI Listing
January 2019
3.571 Impact Factor

Improved stimulated echo in diffusion magnetic resonance imaging: introducing a π pulse for SNR enhancement.

Magn Reson Med 2019 Jan 29. Epub 2019 Jan 29.

CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, China.

Purpose: Anomalous diffusion in biological tissues can be examined by diffusion MRI for various applications, including tumor diagnosis and measurement of brain fiber pathways. However, the measurement of anomalous diffusion requires high b-values for the diffusion gradient in MRI, and current MRI methods cannot provide a high SNR. This study aimed to improve on the standard stimulated echo (STE) to enhance the SNR in diffusion MRI with high b-values. Read More

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http://dx.doi.org/10.1002/mrm.27653DOI Listing
January 2019
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Optimization of steady-state pulsed CEST imaging for amide proton transfer at 3T MRI.

Magn Reson Med 2019 Jan 29. Epub 2019 Jan 29.

Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea.

Purpose: To optimize a steady-state imaging sequence for maximizing the amide proton transfer effects in pulsed-CEST (pCEST) imaging.

Method: The steady-state pCEST (SS-pCEST) sequence is a fast CEST imaging scheme that applies repetitive short RF pulses for generating CEST and acquiring MR imaging signal alternately. To maximize the obtainable amide proton transfer effects, the SS-pCEST scheme is analyzed and optimized with respect to not only the imaging parameters but also the imaging schemes of the signal acquisition part. Read More

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http://dx.doi.org/10.1002/mrm.27674DOI Listing
January 2019

Magnetic resonance elastography of the human brain using a multiphase DENSE acquisition.

Magn Reson Med 2019 Jan 29. Epub 2019 Jan 29.

Department of Neurology, Medical University of Graz, Graz, Austria.

Purpose: In magnetic resonance elastography (MRE), a series of time-shifted images is acquired at specific phase offsets in relation to an induced mechanical excitation. To efficiently gather the set of phase offset images and to overcome limitations due to prolonged TEs and related susceptibility artifacts at low-frequency MRE, we developed an improved displacement encoding with a stimulated echoes (DENSE) method.

Methods: The proposed multiphase DENSE-MRE acquisition scheme allows full sampling of the wave propagation in 1 encoding direction during each TR using multiple readouts at specific phase offsets. Read More

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http://dx.doi.org/10.1002/mrm.27672DOI Listing
January 2019

Use of dielectric padding to eliminate low convective field artifact in cr-MREPT conductivity images.

Magn Reson Med 2019 Jan 29. Epub 2019 Jan 29.

Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey.

Purpose: Convection-reaction equation-based magnetic resonance electrical properties tomography (cr-MREPT) provides conductivity images that are boundary artifact-free and robust against noise. However, these images suffer from the low convective field (LCF) artifact. We propose to use dielectric pads to alter the transmit magnetic field (B ), shift the LCF region, and eliminate the LCF artifact. Read More

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http://doi.wiley.com/10.1002/mrm.27648
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http://dx.doi.org/10.1002/mrm.27648DOI Listing
January 2019
6 Reads

Simultaneous T and T measurements using inversion recovery TrueFISP with principle component-based reconstruction, off-resonance correction, and multicomponent analysis.

Magn Reson Med 2019 Jan 28. Epub 2019 Jan 28.

Magnetic Resonance and X-ray Imaging Department, Fraunhofer Development Center for X-Ray Technology (EZRT), Würzburg, Germany.

Purpose: To improve the reconstruction quality for quantitative T and T measurements using the inversion recovery (IR) TrueFISP sequence and to demonstrate the potential for multicomponent analysis.

Methods: The iterative reconstruction method takes advantage of the high redundancy in the smooth exponential signals using principle component analysis (PCA). Multicomponent information is preserved and allows voxel-by-voxel computation of relaxation time spectra with an inverse Laplace transform. Read More

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http://dx.doi.org/10.1002/mrm.27657DOI Listing
January 2019

Dynamic metabolic imaging of copolarized [2- C]pyruvate and [1,4- C ]fumarate using 3D-spiral CSI with alternate spectral band excitation.

Magn Reson Med 2019 Jan 28. Epub 2019 Jan 28.

Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland, Baltimore, Maryland.

Purpose: Developing a method for simultaneous metabolic imaging of copolarized [2- C]pyruvate and [1,4- C ]fumarate without chemical shift displacement artifacts that also permits different excitation flip angles for substrates and their metabolic products.

Methods: The proposed pulse sequence consists of 2 frequency-selective radiofrequency pulses to alternatingly excite 2 spectral sub-bands each one followed by a fast 3D spiral CSI (3D-spCSI) readout. Spectrally selective radiofrequency pulses were designed to excite differential flip angles on substrates and products in each spectral sub-band. Read More

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http://dx.doi.org/10.1002/mrm.27639DOI Listing
January 2019

Chemical exchange saturation transfer imaging of phosphocreatine in the muscle.

Magn Reson Med 2019 Jan 28. Epub 2019 Jan 28.

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

Purpose: To determine the exchange parameters for the CEST of phosphocreatine (PCrCEST) in phantoms and to characterize PCrCEST in vivo in the muscle at different saturation powers and magnetic fields.

Methods: Exchange parameters were measured in PCr solutions using varying saturation power at 15.2 T. Read More

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http://dx.doi.org/10.1002/mrm.27655DOI Listing
January 2019

Erratum to: Local SAR, Global SAR, and Power-Constrained Large-Flip-Angle Pulses with Optimal Control and Virtual Observation Points (MRM 2017; 77:374-384).

Magn Reson Med 2019 Mar 4;81(3):2195. Epub 2018 Nov 4.

Center of Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Aarhus C, Denmark.

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http://dx.doi.org/10.1002/mrm.27581DOI Listing

Parameter map error due to normal noise and aliasing artifacts in MR fingerprinting.

Magn Reson Med 2019 Jan 23. Epub 2019 Jan 23.

Physics, Case Western Reserve University, Cleveland, Ohio.

Purpose: To introduce a quantitative tool that enables rapid forecasting of T and T parameter map errors due to normal and aliasing noise as a function of the MR fingerprinting (MRF) sequence, which can be used in sequence optimization.

Theory And Methods: The variances of normal noise and aliasing artifacts in the collected signal are related to the variances in T and T maps through derived quality factors. This analytical result is tested against the results of a Monte-Carlo approach for analyzing MRF sequence encoding capability in the presence of aliasing noise, and verified with phantom experiments at 3 T. Read More

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http://dx.doi.org/10.1002/mrm.27638DOI Listing
January 2019

Diffusion tractography of the rat knee at microscopic resolution.

Magn Reson Med 2019 Jan 22. Epub 2019 Jan 22.

Center for In Vivo Microscopy, Duke University School of Medicine, Durham, North Carolina.

Purpose: To evaluate whole knee joint tractography, including articular cartilage, ligaments, meniscus, and growth plate using diffusion tensor imaging (DTI) at microscopic resolution.

Methods: Three rat knee joints were scanned using a modified 3D diffusion-weighted spin echo pulse sequence with 90- and 45-μm isotropic spatial resolution at 9.4T. Read More

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http://dx.doi.org/10.1002/mrm.27652DOI Listing
January 2019

Stabilization of T relaxation and magnetization transfer in cartilage explants by immersion in perfluorocarbon liquid.

Magn Reson Med 2019 Jan 22. Epub 2019 Jan 22.

Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, USA.

Purpose: Magnetic resonance imaging of ex vivo cartilage measures parameters such as T and magnetization transfer ratio (MTR), which reflect structural changes associated with osteoarthritis. Samples are often immersed in aqueous solutions to prevent dehydration and to to improve susceptibility matching. This study sought to determine the extent to which T and MTR changes are attributable to immersion alone and to identify immersion conditions to minimize this confounding factor. Read More

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http://dx.doi.org/10.1002/mrm.27650DOI Listing
January 2019
2 Reads

Parallel imaging in time-of-flight magnetic resonance angiography using deep multistream convolutional neural networks.

Magn Reson Med 2019 Jan 21. Epub 2019 Jan 21.

School of Electrical and Electronic Engineering, Yonsei University, Seoul, Korea.

Purpose: To develop and evaluate a method of parallel imaging time-of-flight (TOF) MRA using deep multistream convolutional neural networks (CNNs).

Methods: A deep parallel imaging network ("DPI-net") was developed to reconstruct 3D multichannel MRA from undersampled data. It comprises 2 deep-learning networks: a network of multistream CNNs for extracting feature maps of multichannel images and a network of reconstruction CNNs for reconstructing images from the multistream network output feature maps. Read More

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http://dx.doi.org/10.1002/mrm.27656DOI Listing
January 2019

Incorporation of a spectral model in a convolutional neural network for accelerated spectral fitting.

Magn Reson Med 2019 Jan 21. Epub 2019 Jan 21.

Wallace H. Coulter Department of Biomedical Engineering, Emory University School of Medicine and Georgia Institute of Technology, Atlanta, Georgia.

Purpose: MRSI has shown great promise in the detection and monitoring of neurologic pathologies such as tumor. A necessary component of data processing includes the quantitation of each metabolite, typically done through fitting a model of the spectrum to the data. For high-resolution volumetric MRSI of the brain, which may have ~10,000 spectra, significant processing time is required for spectral analysis and generation of metabolite maps. Read More

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http://dx.doi.org/10.1002/mrm.27641DOI Listing
January 2019
1 Read

Sparsity adaptive reconstruction for highly accelerated cardiac MRI.

Magn Reson Med 2019 Jan 21. Epub 2019 Jan 21.

Biomedical Engineering, The Ohio State University, Columbus, Ohio.

Purpose: To enable parameter-free, accelerated cardiovascular magnetic resonance (CMR).

Methods: Regularized reconstruction methods, such as compressed sensing (CS), can significantly accelerate MRI data acquisition but require tuning of regularization weights. In this work, a technique, called Sparsity adaptive Composite Recovery (SCoRe) that exploits sparsity in multiple, disparate sparsifying transforms is presented. Read More

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http://dx.doi.org/10.1002/mrm.27671DOI Listing
January 2019

Efficient shear wave elastography using transient acoustic radiation force excitations and MR displacement encoding.

Magn Reson Med 2019 Jan 21. Epub 2019 Jan 21.

Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah.

Purpose: To present a novel MR shear wave elastography (MR-SWE) method that efficiently measures the speed of propagating wave packets generated using acoustic radiation force (ARF) impulses.

Methods: ARF impulses from a focused ultrasound (FUS) transducer were applied sequentially to a preselected set of positions and motion encoded MRI was used to acquire volumetric images of the propagating shear wavefront emanating from each point. The wavefront position at multiple propagation times was encoded in the MR phase image using a train of motion encoding gradient lobes. Read More

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http://dx.doi.org/10.1002/mrm.27647DOI Listing
January 2019
1 Read

Dependence of the MR signal on the magnetic susceptibility of blood studied with models based on real microvascular networks.

Magn Reson Med 2019 Jan 18. Epub 2019 Jan 18.

Neurophotonics Center, Department of Biomedical Engineering, Boston University, Massachusetts.

Purpose: The primary goal of this study was to estimate the value of , the exponent in the power law relating changes of the transverse relaxation rate and intra-extravascular local magnetic susceptibility differences as . The secondary objective was to evaluate any differences that might exist in the value of obtained using a deoxyhemoglobin-weighted distribution versus a constant distribution assumed in earlier computations. The third objective was to estimate the value of β that is relevant for methods based on susceptibility contrast agents with a concentration of higher than that used for BOLD fMRI calculations. Read More

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http://dx.doi.org/10.1002/mrm.27660DOI Listing
January 2019
3 Reads

Improved repeatability of dynamic contrast-enhanced MRI using the complex MRI signal to derive arterial input functions: a test-retest study in prostate cancer patients.

Magn Reson Med 2019 Jan 17. Epub 2019 Jan 17.

Department of Radiation Oncology, the Netherlands Cancer Institute, Amsterdam, The Netherlands.

Purpose: The arterial input function (AIF) is a major source of uncertainty in tracer kinetic (TK) analysis of dynamic contrast-enhanced (DCE)-MRI data. The aim of this study was to investigate the repeatability of AIFs extracted from the complex signal and of the resulting TK parameters in prostate cancer patients.

Methods: Twenty-two patients with biopsy-proven prostate cancer underwent a 3T MRI exam twice. Read More

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http://dx.doi.org/10.1002/mrm.27646DOI Listing
January 2019

SUPER: A blockwise curve-fitting method for accelerating MR parametric mapping with fast reconstruction.

Magn Reson Med 2019 Jan 17. Epub 2019 Jan 17.

Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, Connecticut.

Purpose: To investigate Shift Undersampling improves Parametric mapping Efficiency and Resolution (SUPER), a novel blockwise curve-fitting method for accelerating parametric mapping with very fast reconstruction.

Methods: SUPER uses interleaved k-space undersampling, which enables a blockwise decomposition of the otherwise large-scale cost function to improve the reconstruction efficiency. SUPER can be readily combined with SENSE to achieve at least 4-fold acceleration. Read More

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http://dx.doi.org/10.1002/mrm.27662DOI Listing
January 2019

Measuring large lipid droplet sizes by probing restricted lipid diffusion effects with diffusion-weighted MRS at 3T.

Magn Reson Med 2019 Jan 16. Epub 2019 Jan 16.

Department of Diagnostic and Interventional Radiology, Technical University of Munich, Munich, Germany.

Purpose: The in vivo probing of restricted diffusion effects in large lipid droplets on a clinical MR scanner remains a major challenge due to the need for high b-values and long diffusion times. This work proposes a methodology to probe mean lipid droplet sizes using diffusion-weighted MRS (DW-MRS) at 3T.

Methods: An analytical expression for restricted diffusion was used. Read More

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http://dx.doi.org/10.1002/mrm.27651DOI Listing
January 2019

A continuum of T components: Flexible fast fraction mapping in sodium MRI.

Magn Reson Med 2019 Jan 16. Epub 2019 Jan 16.

Melbourne Brain Centre Imaging Unit, The University of Melbourne, Melbourne, Australia.

Purpose: Parameter mapping in sodium MRI data is challenging due to inherently low SNR and spatial resolution, prompting the need to employ robust models and estimation techniques. This work aims to develop a continuum model of sodium -decay to overcome the limitations of the commonly employed bi-exponential models. Estimates of mean -decay and fast component fraction in tissue are emergent from the inferred continuum model. Read More

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http://doi.wiley.com/10.1002/mrm.27659
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http://dx.doi.org/10.1002/mrm.27659DOI Listing
January 2019
2 Reads

Enhanced hyperpolarized chemical shift imaging based on a priori segmented information.

Magn Reson Med 2019 Jan 16. Epub 2019 Jan 16.

Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 76100, Israel.

Purpose: The purpose of the study was to develop an approach for improving the resolution and sensitivity of hyperpolarized C MRSI based on a priori anatomical information derived from featured, water-based H images.

Methods: A reconstruction algorithm exploiting H MRI for the redefinition of the C MRSI anatomies was developed, based on a modification of the spectroscopy with linear algebraic modeling (SLAM) principle. To enhance C spatial resolution and reduce spillover effects without compromising SNR, this model was extended by endowing it with a search allowing smooth variations in the C MR intensity within the targeted regions of interest. Read More

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http://doi.wiley.com/10.1002/mrm.27631
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http://dx.doi.org/10.1002/mrm.27631DOI Listing
January 2019
3 Reads

Mapping hepatic blood oxygenation by quantitative BOLD (qBOLD) MRI.

Magn Reson Med 2019 Jan 16. Epub 2019 Jan 16.

Department of Radiology, Stony Brook University, Stony Brook, New York, New York.

Purpose: Abnormalities in hepatic oxygen delivery and oxygen consumption may serve as a significant indicator of hepatic cellular dysfunction and may predict treatment response. However, conventional and oxygen-enhanced hepatic BOLD MRI can only provide semiquantitative assessment of hepatic oxygenation.

Methods: A hepatic quantitative BOLD (qBOLD) model was proposed for noninvasive mapping of hepatic venous blood oxygen saturation (Y ) and deoxygenated blood volume (DBV) in human subjects. Read More

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http://doi.wiley.com/10.1002/mrm.27642
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http://dx.doi.org/10.1002/mrm.27642DOI Listing
January 2019
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Robust nonadiabatic T preparation using universal parallel-transmit k -point pulses for 3D FLAIR imaging at 7 T.

Magn Reson Med 2019 Jan 16. Epub 2019 Jan 16.

NeuroSpin, Commissariat à l'Energie Atomique, Université Paris-Saclay, Gif sur Yvette, France.

Purpose: The fluid attenuated inversion recovery sequence is a pillar technique to detect brain lesions in MRI. At ultrahigh field, the lengthening of T often advocates a T -weighting preparation module to regain signal and contrast between tissues, which can be affected by transmit RF field inhomogeneity. In this note, we report an extension of a previous fluid attenuated inversion recovery study that now incorporates the T preparation with parallel transmission calibration-free universal pulses to mitigate the problem. Read More

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http://doi.wiley.com/10.1002/mrm.27645
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http://dx.doi.org/10.1002/mrm.27645DOI Listing
January 2019
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Toward direct MRI of neuro-electro-magnetic oscillations in the human brain.

Magn Reson Med 2019 Jan 16. Epub 2019 Jan 16.

Brain Imaging and Analysis Center, Duke University, Durham, North Carolina.

Purpose: Neuroimaging techniques are widely used to investigate the function of the human brain, but none are currently able to accurately localize neuronal activity with both high spatial and temporal specificity. Here, a new in vivo MRI acquisition and analysis technique based on the spin-lock mechanism is developed to noninvasively image local magnetic field oscillations resulting from neuroelectric activity in specifiable frequency bands.

Methods: Simulations, phantom experiments, and in vivo experiments using an eyes-open/eyes-closed task in 8 healthy volunteers were performed to demonstrate its sensitivity and specificity for detecting oscillatory neuroelectric activity in the alpha-band (8-12 Hz). Read More

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http://doi.wiley.com/10.1002/mrm.27654
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http://dx.doi.org/10.1002/mrm.27654DOI Listing
January 2019
10 Reads

A novel bioreactor for combined magnetic resonance spectroscopy and optical imaging of metabolism in 3D cell cultures.

Magn Reson Med 2019 Jan 16. Epub 2019 Jan 16.

Department of Medical Physics, University of Wisconsin at Madison, Madison, Wisconsin.

Purpose: Fluorescence lifetime imaging microscopy (FLIM) of endogenous fluorescent metabolites permits the measurement of cellular metabolism in cell, tissue and animal models. In parallel, magnetic resonance spectroscopy (MRS) of dynamic nuclear (hyper)polarized (DNP) C-pyruvate enables measurement of metabolism at larger in vivo scales. Presented here are the design and initial application of a bioreactor that connects these 2 metabolic imaging modalities in vitro, using 3D cell cultures. Read More

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http://doi.wiley.com/10.1002/mrm.27644
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http://dx.doi.org/10.1002/mrm.27644DOI Listing
January 2019
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Simian immunodeficiency virus transiently increases brain temperature in rhesus monkeys: detection with magnetic resonance spectroscopy thermometry.

Magn Reson Med 2019 Jan 16. Epub 2019 Jan 16.

McLean Imaging Center, McLean Hospital, Belmont, Massachusetts.

Purpose: To evaluate brain temperature effects of early simian immunodeficiency virus (SIV) infection in rhesus macaques using proton magnetic resonance spectroscopy (MRS) thermometry (MRSt) and to determine whether temperature correlates with brain choline or myo-inositol levels.

Methods: Brain temperature was retrospectively determined in serial MRS scans that had been acquired at baseline and at 2 and 4 weeks post-SIV infection (wpi) in 16 monkeys by calculating the chemical shift difference between N-acetylaspartate (NAA) and water peaks in sequentially acquired water-suppressed and unsuppressed point-resolved spectroscopy (PRESS) spectra. Frontal and parietal cortex, basal ganglia, and white matter spectra were analyzed. Read More

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http://dx.doi.org/10.1002/mrm.27635DOI Listing
January 2019

Simultaneous proton resonance frequency shift thermometry and T measurements using a single reference variable flip angle T method.

Magn Reson Med 2019 Jan 16. Epub 2019 Jan 16.

Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah.

Purpose: Implement simultaneous proton resonance frequency (PRF) shift and T measurements with equivalent temporal resolution using a single reference variable flip angle method. This novel method allows for simultaneous thermometry in both aqueous and fatty tissue.

Methods: This method acquires a single reference image at the lower flip angle and all dynamic images at the higher angle. Read More

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http://doi.wiley.com/10.1002/mrm.27643
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http://dx.doi.org/10.1002/mrm.27643DOI Listing
January 2019
3 Reads

Microscopic anisotropy misestimation in spherical-mean single diffusion encoding MRI.

Magn Reson Med 2019 Jan 16. Epub 2019 Jan 16.

Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, Lisbon, Portugal.

Purpose: Microscopic fractional anisotropy (µFA) can disentangle microstructural information from orientation dispersion. While double diffusion encoding (DDE) MRI methods are widely used to extract accurate µFA, it has only recently been proposed that powder-averaged single diffusion encoding (SDE) signals, when coupled with the diffusion standard model (SM) and a set of constraints, could be used for µFA estimation. This study aims to evaluate µFA as derived from the spherical mean technique (SMT) set of constraints, as well as more generally for powder-averaged SM signals. Read More

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http://dx.doi.org/10.1002/mrm.27606DOI Listing
January 2019

Association of bone mineral density and fat fraction with magnetic susceptibility in inflamed trabecular bone.

Magn Reson Med 2019 Jan 7. Epub 2019 Jan 7.

Department of Medical Physics and Biomedical Engineering, University College London, United Kingdom.

Purpose: To evaluate the relationship between bone mineral density (BMD) and magnetic susceptibility, and between proton density fat fraction and susceptibility, in inflamed trabecular bone.

Methods: Two different phantoms modeling the fat fraction (FF) and BMD values of healthy bone marrow and disease states were scanned using a multiecho gradient echo acquisition at 3T. After correction for fat-water chemical shift, susceptibility mapping was performed, and susceptibility measurements were compared with BMD and FF values using linear regression. Read More

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http://dx.doi.org/10.1002/mrm.27634DOI Listing
January 2019

Cardiorespiratory motion-tracking via self-refocused rosette navigators.

Magn Reson Med 2019 Jan 7. Epub 2019 Jan 7.

Bernard and Irene Schwartz Center for Biomedical Imaging, NYU School of Medicine, New York, New York.

Purpose: To develop a flexible method for tracking respiratory and cardiac motions throughout MR and PET-MR body examinations that requires no additional hardware and minimal sequence modification.

Methods: The incorporation of a contrast-neutral rosette navigator module following the RF excitation allows for robust cardiorespiratory motion tracking with minimal impact on the host sequence. Spatial encoding gradients are applied to the FID signal and the desired motion signals are extracted with a blind source separation technique. Read More

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http://dx.doi.org/10.1002/mrm.27609DOI Listing
January 2019