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Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine

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https://www.readbyqxmd.com/read/28205298/automatic-segmentation-of-the-right-ventricle-from-cardiac-mri-using-a-learning-based-approach
#1
Michael R Avendi, Arash Kheradvar, Hamid Jafarkhani
PURPOSE: This study aims to accurately segment the right ventricle (RV) from cardiac MRI using a fully automatic learning-based method. METHODS: The proposed method uses deep learning algorithms, i.e., convolutional neural networks and stacked autoencoders, for automatic detection and initial segmentation of the RV chamber. The initial segmentation is then combined with the deformable models to improve the accuracy and robustness of the process. We trained our algorithm using 16 cardiac MRI datasets of the MICCAI 2012 RV Segmentation Challenge database and validated our technique using the rest of the dataset (32 subjects)...
February 16, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28205251/multishot-echo-planar-mreit-for-fast-imaging-of-conductivity-current-density-and-electric-field-distributions
#2
Munish Chauhan, Rohini Vidya Shankar, Neeta Ashok Kumar, Vikram D Kodibagkar, Rosalind Sadleir
PURPOSE: Magnetic resonance electrical impedance tomography (MREIT) sequences typically use conventional spin or gradient echo-based acquisition methods for reconstruction of conductivity and current density maps. Use of MREIT in functional and electroporation studies requires higher temporal resolution and faster sequences. Here, single and multishot echo planar imaging (EPI) based MREIT sequences were evaluated to see whether high-quality MREIT phase data could be obtained for rapid reconstruction of current density, conductivity, and electric fields...
February 16, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28198576/a-constrained-slice-dependent-background-suppression-scheme-for-simultaneous-multislice-pseudo-continuous-arterial-spin-labeling
#3
Xingfeng Shao, Yi Wang, Steen Moeller, Danny J J Wang
PURPOSE: To present a constrained slice-dependent (CSD) background-suppression (BS) scheme in 2D arterial spin labeling (ASL) using simultaneous multislice acquisition with blipped-CAIPIRINHA (controlled aliasing in parallel imaging results in higher acceleration). METHODS: Background suppression for 2D acquisition is challenging because of the multiple nulling points required for sequential slice readout. Constrained slice-dependent BS exploits the simultaneous multislice technique to reduce the readout duration, and uses slice-dependent premodulation pulses to achieve BS across slice groups...
February 15, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28198571/pulmonary-mri-morphometry-modeling-of-airspace-enlargement-in-chronic-obstructive-pulmonary-disease-and-alpha-1-antitrypsin-deficiency
#4
Alexei Ouriadov, Eric Lessard, Khadija Sheikh, Grace Parraga
PURPOSE: We generated lung morphometry measurements using single-breath diffusion-weighted MRI and three different acinar duct models in healthy participants and patients with emphysema stemming from chronic obstructive lung disease (COPD) and alpha-1 antitrypsin deficiency (AATD). METHODS: Single-breath-inhaled (3) He MRI with five diffusion sensitizations (b-value = 0, 1.6, 3.2, 4.8, and 6.4 s/cm(2) ) was used, and signal intensities were fit using a cylindrical and single-compartment acinar-duct model to estimate MRI-derived mean linear intercept (Lm ) and surface-to-volume ratio (S/V)...
February 15, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28198568/compressed-sensing-mri-reconstruction-from-3d-multichannel-data-using-gpus
#5
Ching-Hua Chang, Xiangdong Yu, Jim X Ji
PURPOSE: To accelerate iterative reconstructions of compressed sensing (CS) MRI from 3D multichannel data using graphics processing units (GPUs). METHODS: The sparsity of MRI signals and parallel array receivers can reduce the data acquisition requirements. However, iterative CS reconstructions from data acquired using an array system may take a significantly long time, especially for a large number of parallel channels. This paper presents an efficient method for CS-MRI reconstruction from 3D multichannel data using GPUs...
February 15, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28191681/a-time-efficient-acquisition-protocol-for-multipurpose-diffusion-weighted-microstructural-imaging-at-7-tesla
#6
Farshid Sepehrband, Kieran O'Brien, Markus Barth
PURPOSE: Several diffusion-weighted MRI techniques have been developed and validated during the past 2 decades. While offering various neuroanatomical inferences, these techniques differ in their proposed optimal acquisition design, preventing clinicians and researchers benefiting from all potential inference methods, particularly when limited time is available. This study reports an optimal design that enables for a time-efficient diffusion-weighted MRI acquisition scheme at 7 Tesla...
February 12, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28191664/direct-arterial-injection-of-hyperpolarized-13-c-labeled-substrates-into-rat-tumors-for-rapid-mr-detection-of-metabolism-with-minimal-substrate-dilution
#7
Steven Reynolds, Stephen Metcalf, Edward J Cochrane, Rebecca C Collins, Simon Jones, Martyn N J Paley, Gillian M Tozer
PURPOSE: A rat model was developed to enable direct administration of hyperpolarized (13) C-labeled molecules into a tumor-supplying artery for magnetic resonance spectroscopy (MRS) studies of tumor metabolism. METHODS: Rat P22 sarcomas were implanted into the right inguinal fat pad of BDIX rats such that the developing tumors received their principle blood supply directly from the right superior epigastric artery. Hyperpolarized (13) C-molecules were either infused directly to the tumor through the epigastric artery or systemically through the contralateral femoral vein...
February 12, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28191646/non-invasive-evaluation-of-blood-oxygen-saturation-and-hematocrit-from-t1-and-t2-relaxation-times-in-vitro-validation-in-fetal-blood
#8
Sharon Portnoy, Mike Seed, John G Sled, Christopher K Macgowan
PURPOSE: We propose an analytical method for calculating blood hematocrit (Hct) and oxygen saturation (sO2 ) from measurements of its T1 and T2 relaxation times. THEORY: Through algebraic substitution, established two-compartment relationships describing R1=T1-1 and R2=T2-1 as a function of hematocrit and oxygen saturation were rearranged to solve for Hct and sO2 in terms of R1 and R2 . Resulting solutions for Hct and sO2 are the roots of cubic polynomials. METHODS: Feasibility of the method was established by comparison of Hct and sO2 estimates obtained from relaxometry measurements (at 1...
February 12, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28185433/model-based-iterative-reconstruction-for-single-shot-epi-at-7t
#9
Uten Yarach, Myung-Ho In, Itthi Chatnuntawech, Berkin Bilgic, Frank Godenschweger, Hendrik Mattern, Alessandro Sciarra, Oliver Speck
PURPOSE: To describe a model-based reconstruction strategy for single-shot echo planar imaging (EPI) that intrinsically accounts for k-space nonuniformity, Nyquist ghosting, and geometric distortions during rather than before or after image reconstruction. METHODS: Ramp sampling and inhomogeneous B0 field-induced distortion cause the EPI samples to lie on a non-Cartesian grid, thus requiring the nonuniform fast Fourier transform. Additionally, a 2D Nyquist ghost phase correction without the need for extra navigator acquisition is included in the proposed reconstruction...
February 10, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28185321/a-2-in-1-single-element-coil-design-for-transcranial-magnetic-stimulation-and-magnetic-resonance-imaging
#10
Hai Lu, Shumin Wang
PURPOSE: To demonstrate the feasibility of turning transcranial magnetic stimulation (TMS) coil for MRI signal reception. METHODS: A critically coupled network was formed by using a resonated turn of TMS coil as the secondary and a regular radiofrequency (RF) coil as the primary. A third coil was positioned between the two coils for detuning during RF transmission. Bench measurement, numerical simulation, and MRI experiment were performed for validation. RESULTS: The signal-to-noise ratio of the proposed 2-in-1 coil is 35% higher in its field of view, compared with a MRI-only reference coil of the same size, made by the same material, and backed up by an untuned TMS coil, but lower than a RF surface coil of the same size without any TMS coil nearby...
February 10, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28185310/multifrequency-reconstruction-for-frequency-modulated-bssfp
#11
Anne Slawig, Tobias Wech, Valentin Ratz, Johannes Tran-Gia, Henning Neubauer, Thorsten Bley, Herbert Köstler
PURPOSE: Banding artifacts in images acquired by balanced steady-state free precession (bSSFP) remain a challenge in MRI as they considerably reduce image quality, and diagnostic value deteriorates accordingly. As the steady-state tolerates small shifts in frequency, it is possible to acquire frequency-modulated bSSFP. Unfortunately, standard reconstructions of such measurements suffer from signal loss. Our study proposes a multifrequency reconstruction and demonstrates its capability of suppressing banding artifacts while retaining the high signal level of standard bSSFP...
February 10, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28185304/dual-echo-z-shimmed-proton-resonance-frequency-shift-magnetic-resonance-thermometry-near-metallic-ablation-probes-technique-and-temperature-precision
#12
Yuxin Zhang, Megan E Poorman, William A Grissom
PURPOSE: To improve the precision of proton resonance frequency-shift magnetic resonance thermometry near ablation probes by recovering near-probe image signals that are typically lost due to magnetic susceptibility-induced field distortions. METHODS: A dual-echo gradient-recalled echo sequence was implemented, in which the first echo was under- or over-refocused in the slice dimension to recover image signal and temperature precision near a probe, and the second echo was fully refocused to obtain image signal everywhere else in the slice...
February 10, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28185303/interchangeable-neck-shape-specific-coils-for-a-clinically-realizable-anterior-neck-phased-array-system
#13
Michael J Beck, Dennis L Parker, Bradley D Bolster, Seong-Eun Kim, J Scott McNally, Gerald S Treiman, J Rock Hadley
PURPOSE: To demonstrate the interchangeable neck shape-specific (NSS) coil concept that supplements standard commercial spine and head/neck coils to provide simultaneous high-resolution (hi-res) head/neck imaging with high signal-to-noise ratio (SNR). METHODS: Two NSS coils were constructed on formers designed to fit two different neck shapes. A 7-channel (7ch) ladder array was constructed on a medium neck former, and a 9-channel (9ch) ladder array was constructed on large neck former...
February 10, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28185301/feasibility-of-through-time-spiral-generalized-autocalibrating-partial-parallel-acquisition-for-low-latency-accelerated-real-time-mri-of-speech
#14
Sajan Goud Lingala, Yinghua Zhu, Yongwan Lim, Asterios Toutios, Yunhua Ji, Wei-Ching Lo, Nicole Seiberlich, Shrikanth Narayanan, Krishna S Nayak
PURPOSE: To evaluate the feasibility of through-time spiral generalized autocalibrating partial parallel acquisition (GRAPPA) for low-latency accelerated real-time MRI of speech. METHODS: Through-time spiral GRAPPA (spiral GRAPPA), a fast linear reconstruction method, is applied to spiral (k-t) data acquired from an eight-channel custom upper-airway coil. Fully sampled data were retrospectively down-sampled to evaluate spiral GRAPPA at undersampling factors R = 2 to 6...
February 10, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28169457/improving-labeling-efficiency-in-automatic-quality-control-of-mrsi-data
#15
Nuno Pedrosa de Barros, Richard McKinley, Roland Wiest, Johannes Slotboom
PURPOSE: To improve the efficiency of the labeling task in automatic quality control of MR spectroscopy imaging data. METHODS: 28'432 short and long echo time (TE) spectra (1.5 tesla; point resolved spectroscopy (PRESS); repetition time (TR)= 1,500 ms) from 18 different brain tumor patients were labeled by two experts as either accept or reject, depending on their quality. For each spectrum, 47 signal features were extracted. The data was then used to run several simulations and test an active learning approach using uncertainty sampling...
February 7, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28168738/golden-ratio-rotated-stack-of-stars-acquisition-for-improved-volumetric-mri
#16
Ziwu Zhou, Fei Han, Lirong Yan, Danny J J Wang, Peng Hu
PURPOSE: To develop and evaluate an improved stack-of-stars radial sampling strategy for reducing streaking artifacts. METHODS: The conventional stack-of-stars sampling strategy collects the same radial angle for every partition (slice) encoding. In an undersampled acquisition, such an aligned acquisition generates coherent aliasing patterns and introduces strong streaking artifacts. We show that by rotating the radial spokes in a golden-angle manner along the partition-encoding direction, the aliasing pattern is modified, resulting in improved image quality for gridding and more advanced reconstruction methods...
February 6, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28164366/ultralow-field-and-spin-locking-relaxation-dispersion-in-postmortem-pig-brain
#17
Hui Dong, Seong-Min Hwang, Michael Wendland, Lixing You, John Clarke, Ben Inglis
PURPOSE: To investigate tissue-specific differences, a quantitative comparison was made between relaxation dispersion in postmortem pig brain measured at ultralow fields (ULF) and spin locking at 7 tesla (T). The goal was to determine whether ULF-MRI has potential advantages for in vivo human brain imaging. METHODS: Separate specimens of gray matter and white matter were investigated using an ULF-MRI system with superconducting quantum interference device (SQUID) signal detection to measure T1ULF at fields from 58...
February 5, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28164364/simultaneous-determination-of-metabolite-concentrations-t1-and-t2-relaxation-times
#18
Li An, Shizhe Li, Jun Shen
PURPOSE: To simultaneously measure concentration and T1 and T2 values of metabolites in the human brain in a single scan session. METHODS: A new pulse sequence with multiple variable acquisition parameters was proposed to encode metabolite T1 and T2 information into the acquired data. A linear combination-fitting algorithm was developed in-house to simultaneously determine metabolite concentrations and relaxation times. RESULTS: Concentration, T1 , and T2 values of N-acetyl-aspartate, total creatine, total choline, and glutamate were reliably measured in the frontal gray matter and white matter regions of nine healthy volunteers at 7 tesla in less than 10 minutes of scan time per voxel...
February 5, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28164362/mri-based-transfer-function-determination-for-the-assessment-of-implant-safety
#19
J P Tokaya, A J E Raaijmakers, P R Luijten, J F Bakker, C A T van den Berg
PURPOSE: We introduce a new MR-based method to determine the transfer function (TF) for radiofrequency (RF) safety assessment of active implantable medical devices. Transfer functions are implant-specific measures that relate the incident tangential electric field on an (elongated) implant to a scattered electric field at its tip. The proposed method allows for TF determination with a high spatial resolution in relatively fast measurements without requiring dedicated bench setups from MRI images...
February 5, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28164361/in-vivo-quantification-of-aortic-stiffness-using-mr-elastography-in-hypertensive-porcine-model
#20
Huiming Dong, Ria Mazumder, Venkata Sita Priyanka Illapani, Xiaokui Mo, Richard D White, Arunark Kolipaka
PURPOSE: Aortic stiffness plays an important role in evaluating and predicting the progression of systemic arterial hypertension (SAH). The aim of this study is to determine the stiffness of aortic wall using MR elastography (MRE) in a hypertensive porcine model and compare it against invasive aortic pressure measurements. METHODS: Renal wrapping surgery was performed on eight pigs to induce SAH. Aortic MRE was performed at baseline and 2 months postsurgery using a retrospectively pulse-gated gradient-echo MRE sequence on a 1...
February 5, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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