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Magnetic Resonance Imaging

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https://www.readbyqxmd.com/read/28219649/a-novel-approach-to-segmentation-and-measurement-of-medical-image-using-level-set-methods
#1
Yao-Tien Chen
The study proposes a novel approach for segmentation and visualization plus value-added surface area and volume measurements for brain medical image analysis. The proposed method contains edge detection and Bayesian based level set segmentation, surface and volume rendering, and surface area and volume measurements for 3D objects of interest (i.e., brain tumor, brain tissue, or whole brain). Two extensions based on edge detection and Bayesian level set are first used to segment 3D objects. Ray casting and a modified marching cubes algorithm are then adopted to facilitate volume and surface visualization of medical-image dataset...
February 17, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28219648/direct-magnitude-and-phase-imaging-of-myelin-using-ultrashort-echo-time-ute-pulse-sequences-a-feasibility-study
#2
Qun He, Yajun Ma, Shujuan Fan, Hongda Shao, Vipul Sheth, Graeme M Bydder, Jiang Du
In this paper, we aimed to investigate the feasibility of direct visualization of myelin, including myelin lipid and myelin basic protein (MBP), using two-dimensional ultrashort echo time (2D UTE) sequences and utilize phase information as a contrast mechanism in phantoms and in volunteers. The standard UTE sequence was used to detect both myelin and long T2 signal. An adiabatic inversion recovery UTE (IR-UTE) sequence was used to selectively detect myelin by suppressing signal from long T2 water protons. Magnitude and phase imaging and T2* were investigated on myelin lipid and MBP in the forms of lyophilized powders as well as paste-like phantoms with the powder mixed with D2O, and rubber phantoms as well as healthy volunteers...
February 17, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28216453/quantification-of-myocardial-oxygenation-in-heart-failure-using-blood-oxygen-level-dependent-t2-magnetic-resonance-imaging-comparison-with-cardiopulmonary-exercise-test
#3
Michinobu Nagao, Yuzo Yamasaki, Satoshi Kawanami, Takeshi Kamitani, Koji Sagiyama, Taiki Higo, Tomomi Ide, Atsushi Takemura, Umiko Ishizaki, Kenji Fukushima, Yuji Watanabe, Hiroshi Honda
PURPOSE: Quantification of myocardial oxygenation (MO) in heart failure (HF) has been less than satisfactory. This has necessitated the use of invasive techniques to measure MO directly or to determine the oxygen demand during exercise using the cardiopulmonary exercise (CPX) test. We propose a new quantification method for MO using blood-oxygen-level-dependent (BOLD) myocardial T2* magnetic resonance imaging (M-T2* MRI), and investigate its correlation with CPX results. METHODS: Thirty patients with refractory HF who underwent cardiac MRI and CPX test for heart transplantation, and 24 healthy, age-matched volunteers as controls were enrolled...
February 16, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28216452/water-and-lipid-diffusion-mri-using-chemical-shift-displacement-based-separation-of-lipid-tissue-split
#4
Naoki Ohno, Hirohito Kan, Tosiaki Miyati, Toshitaka Aoki, Shota Ishida, Toshifumi Gabata
PURPOSE: To obtain water and lipid diffusion-weighted images (DWIs) simultaneously, we devised a novel method utilizing chemical shift displacement-based separation of lipid tissue (SPLIT) imaging. MATERIALS AND METHODS: Single-shot diffusion echo-planar imaging without fat suppression was used and the imaging parameters were optimized to separate water and lipid DWIs by chemical shift displacement of the lipid signals along the phase-encoding direction. Using the optimized conditions, transverse DWIs at the maximum diameter of the right calf were scanned with multiple b-values in five healthy subjects...
February 16, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28189821/improved-traveling-wave-efficiency-in-7t-human-mri-using-passive-local-loop-and-dipole-arrays
#5
Xinqiang Yan, Xiaoliang Zhang, John C Gore, William A Grissom
Traveling-wave MRI, which uses relatively small and simple RF antennae, has robust matching performance and capability for large field-of-view (FOV) imaging. However, the power efficiency of traveling-wave MRI is much lower than conventional methods, which limits its application. One simple approach to improve the power efficiency is to place passive resonators around the subject being imaged. The feasibility of this approach has been demonstrated in previous works using a single small resonant loop. In this work, we aim to explore how much the improvements can be maintained in human imaging using an array design, and whether electric dipoles can be used as local elements...
February 9, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28188872/pre-transplantation-31-p-magnetic-resonance-spectroscopy-for-quality-assessment-of-human-pancreatic-grafts-a-feasibility-study
#6
Lina Carlbom, Jan Weis, Lars Johansson, Olle Korsgren, Håkan Ahlström
OBJECTIVE: To investigate the feasibility of using (31)P-MRS for objective non-invasive quality assessment of human pancreas grafts prior to transplantation or islet isolation. MATERIALS AND METHODS: Pancreata from 5 human donors, 3 males and 2 females, aged 49-78years, with body mass index (BMI) 22-31kg/m(2), were included. Pancreata were perfused with histidine-tryptophan-ketoglutarate solution during procurement and stored in hypothermic condition (4°C) for 21-44h...
February 8, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28188873/an-improved-fsl-first-pipeline-for-subcortical-gray-matter-segmentation-to-study-abnormal-brain-anatomy-using-quantitative-susceptibility-mapping-qsm
#7
Xiang Feng, Andreas Deistung, Michael G Dwyer, Jesper Hagemeier, Paul Polak, Jessica Lebenberg, Frédérique Frouin, Robert Zivadinov, Jürgen R Reichenbach, Ferdinand Schweser
Accurate and robust segmentation of subcortical gray matter (SGM) nuclei is required in many neuroimaging applications. FMRIB's Integrated Registration and Segmentation Tool (FIRST) is one of the most popular software tools for automated subcortical segmentation based on T1-weighted (T1w) images. In this work, we demonstrate that FIRST tends to produce inaccurate SGM segmentation results in the case of abnormal brain anatomy, such as present in atrophied brains, due to a poor spatial match of the subcortical structures with the training data in the MNI space as well as due to insufficient contrast of SGM structures on T1w images...
February 7, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28185692/comments-on-intravoxel-incoherent-motion-diffusion-weighted-imaging-as-an-adjunct-to-dynamic-contrast-enhanced-mri-to-improve-accuracy-of-the-differential-diagnosis-of-benign-and-malignant-breast-lesions
#8
LETTER
https://www.readbyqxmd.com/read/28167143/causal-mri-reconstruction-via-kalman-prediction-and-compressed-sensing-correction
#9
Angshul Majumdar
This technical note addresses the problem of causal online reconstruction of dynamic MRI, i.e. given the reconstructed frames till the previous time instant, we reconstruct the frame at the current instant. Our work follows a prediction-correction framework. Given the previous frames, the current frame is predicted based on a Kalman estimate. The difference between the estimate and the current frame is then corrected based on the k-space samples of the current frame; this reconstruction assumes that the difference is sparse...
February 4, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28163122/comparison-of-bold-diffusion-weighted-fmri-and-adc-fmri-for-stimulation-of-the-primary-visual-system-with-a-block-paradigm
#10
R Nicolas, H Gros-Dagnac, F Aubry, P Celsis
The blood oxygen level-dependent (BOLD) effect is extensively used for functional MRI (fMRI) but presents some limitations. Diffusion-weighted fMRI (DfMRI) has been proposed as a method more tightly linked to neuronal activity. This work proposes a protocol of DfMRI acquired for several b-values and diffusion directions that is compared to gradient-echo BOLD (GE-BOLD) and to repeated spin-echo BOLD (SE-BOLD, acquisitions performed with b=0s/mm(2)), which was also used to ensure the reproducibility of the response...
February 2, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28161319/biophysical-and-neural-basis-of-resting-state-functional-connectivity-evidence-from-non-human-primates
#11
REVIEW
Li Min Chen, Pai-Feng Yang, Feng Wang, Arabinda Mishra, Zhaoyue Shi, Ruiqi Wu, Tung-Lin Wu, George H Wilson, Zhaohua Ding, John C Gore
Functional MRI (fMRI) has evolved from simple observations of regional changes in MRI signals caused by cortical activity induced by a task or stimulus, to task-free acquisitions of images in a resting state. Such resting state signals contain low frequency fluctuations which may be correlated between voxels, and strongly correlated regions are deemed to reflect functional connectivity within synchronized circuits. Resting state functional connectivity (rsFC) measures have been widely adopted by the neuroscience community, and are being used and interpreted as indicators of intrinsic neural circuits and their functional states in a broad range of applications, both basic and clinical...
February 2, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28137626/reliability-of-the-depth-dependent-high-resolution-bold-hemodynamic-response-in-human-visual-cortex-and-vicinity
#12
Jung Hwan Kim, David Ress
Functional magnetic resonance imaging (fMRI) often relies on a hemodynamic response function (HRF), the stereotypical blood oxygen level dependent (BOLD) response elicited by a brief (<4s) stimulus. Early measurements of the HRF used coarse spatial resolutions (≥3mm voxels) that would generally include contributions from white matter, gray matter, and the extra-pial compartment (the space between the pial surface and skull including pial blood vessels) within each voxel. To resolve these contributions, high-resolution fMRI (0...
January 28, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28137627/prospective-motion-correction-for-3d-pseudo-continuous-arterial-spin-labeling-using-an-external-optical-tracking-system
#13
Murat Aksoy, Julian Maclaren, Roland Bammer
Head motion is an unsolved problem in magnetic resonance imaging (MRI) studies of the brain. Real-time tracking using a camera has recently been proposed as a way to prevent head motion artifacts. As compared to navigator-based approaches that use MRI data to detect and correct motion, optical motion correction works independently of the MRI scanner, thus providing low-latency real-time motion updates without requiring any modifications to the pulse sequence. The purpose of this study was two-fold: 1) to demonstrate that prospective optical motion correction using an optical camera mitigates artifacts from head motion in three-dimensional pseudo-continuous arterial spin labeling (3D PCASL) acquisitions and 2) to assess the effect of latency differences between real-time optical motion tracking and navigator-style approaches (such as PROMO)...
January 27, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28132859/improved-performance-of-prostate-dce-mri-using-a-32-coil-vs-12-coil-receiver-array
#14
Stephen J Riederer, Eric A Borisch, Adam T Froemming, Roger C Grimm, Akira Kawashima, Lance A Mynderse, Joshua D Trzasko
PURPOSE: To assess whether acquisition with 32 receiver coils rather than the vendor-recommended 12 coils provides significantly improved performance in 3D dynamic contrast-enhanced MRI (DCE-MRI) of the prostate. MATERIALS: The study was approved by the institutional review board and was compliant with HIPAA. 50 consecutive male patients in whom prostate MRI was clinically indicated were prospectively imaged in March 2015 with an accelerated DCE-MRI sequence in which image reconstruction was performed using 12 and 32 coil elements...
January 27, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28131908/multispectral-3d-phase-encoded-turbo-spin-echo-for-imaging-near-metal-limitations-and-possibilities-demonstrated-by-simulations-and-phantom-experiments
#15
Jetse S van Gorp, Razmara Nizak, Job G Bouwman, Daniël B F Saris, Peter R Seevinck
To see improvements in the imaging performance near biomaterial implants we assessed a multispectral fully phase-encoded turbo spin-echo (ms3D-PE-TSE) sequence for artifact reduction capabilities and scan time efficiency in simulation and phantom experiments. For this purpose, ms3D-PE-TSE and ms3D-TSE sequences were implemented to obtain multispectral images (±20kHz) of a cobalt-chromium (CoCr) knee implant embedded in agarose. In addition, a knee implant computer model and the acquired ms3D-PE-TSE images were used to investigate the possibilities for scan time acceleration using field-of-view (FOV) reduction for off-resonance frequency bins and compressed sensing reconstructions of undersampled data...
January 25, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28131907/3d-late-gadolinium-enhanced-cardiovascular-mr-with-centra-plus-profile-view-ordering-feasibility-of-right-ventricular-myocardial-damage-assessment-using-a-swine-animal-model
#16
Keigo Kawaji, Akiko Tanaka, Mita B Patel, Hui Wang, Francesco Maffessanti, Takeyoshi Ota, Amit R Patel
AIMS: To develop a high-resolution, 3D late gadolinium enhancement (LGE) cardiovascular magnetic resonance imaging (MRI) technique for improved assessment of myocardial scars, and evaluate its performance against 2D breath-held (BH) LGE MRI using a surgically implanted animal scar model in the right ventricle (RV). METHODS AND RESULTS: A k-space segmented 3D LGE acquisition using CENTRA-PLUS (Contrast ENhanced Timing Robust Acquisition with Preparation of LongitUdinal Signal; or CP) ordering is proposed...
January 25, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28109888/improving-structural-brain-images-acquired-with-the-3d-flash-sequence
#17
Jinghua Wang, Lili He, Hairong Zheng, Zhong-Lin Lu
The three-dimension Fast Low Angle SHot Magnetic Resonance Imaging (3D FLASH) sequence has been widely adopted in medical diagnostic imaging because of its availability, simplicity, and high spatial resolution. To improve the quality of structural brain images acquired with the 3D FLASH sequence, we developed a parameter optimization scheme and image inhomogeneity correction methods. The optimal imaging parameters were determined by maximizing gray-matter and white-matter CNR efficiency. Compared to protocols based on published parameters, applying the proposed optimal imaging parameters increased CNR efficiency by >10%...
January 19, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28109887/compressed-sensing-based-simultaneous-black-and-gray-blood-carotid-vessel-wall-mr-imaging
#18
Bo Li, Hao Li, Hanjing Kong, Li Dong, Jue Zhang, Jing Fang
OBJECTIVE: In this study, we sought to demonstrate the blood suppression performance, image quality and morphological measurements for compressed sensing (CS) based simultaneous 3D black- and gray-blood imaging sequence (CS-siBLAG) in carotid vessel wall MR imaging. MATERIALS AND METHODS: Seven healthy volunteers and five patients were recruited. Healthy subjects underwent five CS-siBLAG scans with 1, 2, 3, 4 and 5-fold accelerations. Signal-to-tissue ratio (STR) and contrast-to-tissue ratio (CTR) were computed as the measures of flowing signal suppression performance and the image quality for black-blood imaging of the technique...
January 19, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28108373/left-ventricle-segmentation-via-two-layer-level-sets-with-circular-shape-constraint
#19
Cong Yang, Weiguo Wu, Yuanqi Su, Shaoxiang Zhang
This paper proposes a circular shape constraint and a novel two-layer level set method for the segmentation of the left ventricle (LV) from short-axis magnetic resonance images without training any shape models. Since the shape of LV throughout the apex-base axis is close to a ring shape, we propose a circle fitting term in the level set framework to detect the endocardium. The circle fitting term imposes a penalty on the evolving contour from its fitting circle, and thereby handles quite well with issues in LV segmentation, especially the presence of outflow track in basal slices and the intensity overlap between TPM and the myocardium...
January 17, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28104438/safety-of-externally-stimulated-intracranial-electrodes-during-functional-mri-at-1-5t
#20
Pallab K Bhattacharyya, Jeffery Mullin, Bryan S Lee, Jorge A Gonzalez-Martinez, Stephen E Jones
Surgical resection of the epileptogenic zone (EZ) is a potential cure for medically refractory focal epilepsy. Proper identification of the EZ is essential for such resection. Synergistic application of functional magnetic resonance imaging (fMRI) simultaneously with stimulation of a single externalized intracranial stereotactic EEG (SEEG) electrode has the potential to improve identification of the EZ. While most EEG-fMRI studies use the electrodes passively to record electrical activity, it is possible to stimulate the brain using the electrodes by connecting them with conducting cables to the stimulation hardware...
January 16, 2017: Magnetic Resonance Imaging
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