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Non cartesian MRI

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https://www.readbyqxmd.com/read/27831865/the-spurs-algorithm-for-resampling-an-irregularly-sampled-signal-onto-a-cartesian-grid
#1
Amir Kiperwas, Daniel Rosenfeld, Yonina C Eldar
We present an algorithm for resampling a function from its values on a non-Cartesian grid onto a Cartesian grid. This problem arises in many applications such as MRI, CT, radio astronomy and geophysics. Our algorithm, termed SParse Uniform ReSampling (SPURS), employs methods from modern sampling theory to achieve a small approximation error while maintaining low computational cost. The given non-Cartesian samples are projected onto a selected intermediate subspace, spanned by integer translations of a compactly supported kernel function...
November 1, 2016: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/27763692/accelerated-mapping-of-magnetic-susceptibility-using-3d-planes-on-a-paddlewheel-pop-epi-at-ultra-high-field-strength
#2
Daniel Stäb, Steffen Bollmann, Christian Langkammer, Kristian Bredies, Markus Barth
With the advent of ultra-high field MRI scanners in clinical research, susceptibility based MRI has recently gained increasing interest because of its potential to assess subtle tissue changes underlying neurological pathologies/disorders. Conventional, but rather slow, three-dimensional (3D) spoiled gradient-echo (GRE) sequences are typically employed to assess the susceptibility of tissue. 3D echo-planar imaging (EPI) represents a fast alternative but generally comes with echo-time restrictions, geometrical distortions and signal dropouts that can become severe at ultra-high fields...
October 20, 2016: NMR in Biomedicine
https://www.readbyqxmd.com/read/27591366/variable-density-sampling-and-non-cartesian-super-resolved-reconstruction-for-spatiotemporally-encoded-single-shot-mri
#3
Lin Chen, Jianpan Huang, Ting Zhang, Jing Li, Congbo Cai, Shuhui Cai
Spatiotemporally encoded (SPEN) single-shot MRI is an emerging ultrafast technique, which is capable of spatially selective acquisition and reduced field-of-view imaging. Compared to uniform sampling, variable density sampling has great potential in reducing aliasing artifacts and improving sampling efficiency. In this study, variable density spiral trajectory and non-Cartesian super-resolved (SR) reconstruction method are developed for SPEN MRI. The gradient waveforms design of spiral trajectory is mathematically described as an optimization problem subjected to the limitations of hardware...
August 28, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27580517/assessment-of-cerebral-blood-perfusion-reserve-with-acetazolamide-using-3d-spiral-asl-mri-preliminary-experience-in-pediatric-patients
#4
Houchun H Hu, Zhiqiang Li, Amber L Pokorney, Jonathan M Chia, Niccolo Stefani, James G Pipe, Jeffrey H Miller
PURPOSE: To demonstrate the clinical feasibility of a new non-Cartesian cylindrically-distributed spiral 3D pseudo-continuous arterial spin labeling (pCASL) magnetic resonance imaging (MRI) pulse sequence in pediatric patients in quantifying cerebral blood flow (CBF) response to an acetazolamide (ACZ) vasodilator challenge. MATERIALS AND METHODS: MRI exams were performed on two 3 Tesla Philips Ingenia systems using 32 channel head coil arrays. After local institutional review board approval, the 3D spiral-based pCASL technique was added to a standard brain MRI exam and evaluated in 13 pediatric patients (average age: 11...
August 28, 2016: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/27373796/adding-muscle-where-you-need-it-non-uniform-hypertrophy-patterns-in-elite-sprinters
#5
G G Handsfield, K R Knaus, N M Fiorentino, C H Meyer, J M Hart, S S Blemker
Sprint runners achieve much higher gait velocities and accelerations than average humans, due in part to large forces generated by their lower limb muscles. Various factors have been explored in the past to understand sprint biomechanics, but the distribution of muscle volumes in the lower limb has not been investigated in elite sprinters. In this study, we used non-Cartesian MRI to determine muscle sizes in vivo in a group of 15 NCAA Division I sprinters. Normalizing muscle sizes by body size, we compared sprinter muscles to non-sprinter muscles, calculated Z-scores to determine non-uniformly large muscles in sprinters, assessed bilateral symmetry, and assessed gender differences in sprinters' muscles...
July 4, 2016: Scandinavian Journal of Medicine & Science in Sports
https://www.readbyqxmd.com/read/27317215/mri-evaluation-of-cooperative-and-non-cooperative-patients-with-non-traumatic-acute-abdominal-pain-preliminary-observations
#6
Miguel Ramalho, Inul Hithaya, Mamdoh AlObaidy, Janaka Kalubowila, Yong Hwan Jeon, Sriluxayini Manikkavasakar, Richard C Semelka
PURPOSE: To compare diagnostic performance of two MRI protocols, motion resistant and conventional breath-hold, in patients with acute abdominal pain. MATERIALS AND METHODS: Thirty-five patients unable to breath-hold underwent a motion-resistant protocol (Radial group). Twenty-seven patients able to breath-hold underwent conventional protocol. The diagnostic performance of MRI was calculated. Cartesian and radial 3D-GRE sequences were compared. RESULTS: In Radial group, diagnosis was correct in 31/35 patients (88...
July 2016: Clinical Imaging
https://www.readbyqxmd.com/read/27271925/feasibility-of-self-gated-isotropic-radial-late-phase-mr-imaging-of-the-liver
#7
Jakob Weiss, Jana Taron, Ahmed E Othman, Robert Grimm, Matthias Kuendel, Petros Martirosian, Christer Ruff, Christina Schraml, Konstantin Nikolaou, Mike Notohamiprodjo
OBJECTIVE: To evaluate feasibility of a 3D-isotropic self-gated radial volumetric interpolated breath-hold examination (VIBE) for late-phase MRI of the liver. MATERIAL AND METHODS: 70 patients were included and underwent liver MRI at 1.5 T. Depending on the diagnosis, either Gd-EOB-DTPA (35 patients) or gadobutrol (35 patients) were administered. During late (gadobutrol) or hepatocyte-specific phase (Gd-EOB-DTPA), a radial prototype sequence was acquired and reconstructed using (1) self-gating with 40 % acceptance (rVIBE40); (2) with 100 % acceptance of the data (rVIBE100) and compared to Cartesian VIBE (cVIBE)...
June 8, 2016: European Radiology
https://www.readbyqxmd.com/read/27173617/-massive-brain-dataset-multiple-acquisitions-for-standardization-of-structural-imaging-validation-and-evaluation
#8
Martijn Froeling, Chantal M W Tax, Sjoerd B Vos, Peter R Luijten, Alexander Leemans
PURPOSE: In this work, we present the MASSIVE (Multiple Acquisitions for Standardization of Structural Imaging Validation and Evaluation) brain dataset of a single healthy subject, which is intended to facilitate diffusion MRI (dMRI) modeling and methodology development. METHODS: MRI data of one healthy subject (female, 25 years) were acquired on a clinical 3 Tesla system (Philips Achieva) with an eight-channel head coil. In total, the subject was scanned on 18 different occasions with a total acquisition time of 22...
May 13, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27073905/comparison-of-cartesian-and-non-cartesian-real-time-mri-sequences-at-1-5t-to-assess-velar-motion-and-velopharyngeal-closure-during-speech
#9
Andreia C Freitas, Marzena Wylezinska, Malcolm J Birch, Steffen E Petersen, Marc E Miquel
Dynamic imaging of the vocal tract using real-time MRI has been an active and growing area of research, having demonstrated great potential to become routinely performed in the clinical evaluation of speech and swallowing disorders. Although many technical advances have been made in regards to acquisition and reconstruction methodologies, there is still no consensus in best practice protocols. This study aims to compare Cartesian and non-Cartesian real-time MRI sequences, regarding image quality and temporal resolution trade-off, for dynamic speech imaging...
2016: PloS One
https://www.readbyqxmd.com/read/27017991/hybrid-radial-cones-trajectory-for-accelerated-mri
#10
Kevin M Johnson
PURPOSE: To design and develop a series of ultrashort echo time k-space sampling schemes, termed radial-cones, which enables high sampling efficiency while maintaining compatibility with parallel imaging and compressed sensing reconstructions. THEORY AND METHODS: Radial-cones is a trajectory that samples three-dimensional (3D) k-space using a single base cone distributed along radial dimensions through a cost function-based optimization. Trajectories were generated for highly undersampled, short readout sampling and compared with 3D radial sampling in point spread function (PSF) analysis, digital and physical phantoms, and initial human volunteers...
March 28, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/26777798/accelerating-functional-mri-using-fixed-rank-approximations-and-radial-cartesian-sampling
#11
Mark Chiew, Nadine N Graedel, Jennifer A McNab, Stephen M Smith, Karla L Miller
PURPOSE: Recently, k-t FASTER (fMRI Accelerated in Space-time by means of Truncation of Effective Rank) was introduced for rank-constrained acceleration of fMRI data acquisition. Here we demonstrate improvements achieved through a hybrid three-dimensional radial-Cartesian sampling approach that allows posthoc selection of acceleration factors, as well as incorporation of coil sensitivity encoding in the reconstruction. METHODS: The multicoil rank-constrained reconstruction used hard thresholding and shrinkage on matrix singular values of the space-time data matrix, using sensitivity encoding and the nonuniform Fast Fourier Transform to enforce data consistency in the multicoil non-Cartesian k-t domain...
December 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/26519940/pseudo-projection-driven-self-gated-cardiac-cine-imaging-using-cartesian-golden-step-phase-encoding
#12
Liheng Guo, J Andrew Derbyshire, Daniel A Herzka
PURPOSE: To develop and evaluate a novel two-dimensional self-gated imaging technique for free-breathing cardiac cine MRI that is free of motion-detection overhead and requires minimal planning for motion tracking. METHODS: Motion along the readout direction was extracted solely from normal Cartesian imaging readouts near ky  = 0. During imaging, the readouts below a certain |ky | threshold were scaled in magnitude and filtered in time to form "pseudo-projections," enabling projection-based motion tracking along readout without frequently acquiring the central phase encode...
August 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/26507705/coil-compression-in-simultaneous-multislice-functional-mri-with-concentric-ring-slice-grappa-and-sense
#13
Alan Chu, Douglas C Noll
PURPOSE: Simultaneous multislice (SMS) imaging is a useful way to accelerate functional magnetic resonance imaging (fMRI). As acceleration becomes more aggressive, an increasingly larger number of receive coils are required to separate the slices, which significantly increases the computational burden. We propose a coil compression method that works with concentric ring non-Cartesian SMS imaging and should work with Cartesian SMS as well. We evaluate the method on fMRI scans of several subjects and compare it to standard coil compression methods...
October 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/26194589/evaluation-of-the-orbit-using-contrast-enhanced-radial-3d-fat-suppressed-t1-weighted-gradient-echo-radial-vibe-sequence
#14
Lev Bangiyev, Eytan Raz, Tobias K Block, Mari Hagiwara, Xin Wu, Eugene Yu, Girish M Fatterpekar
OBJECTIVE: Contrast-enhanced fat-suppressed T1 weighted (T1W) two-dimensional (2D) turbo spin echo (TSE) and magnetization-prepared gradient echo (MPRAGE) sequences with water excitation are routinely obtained to evaluate orbit pathology. However, these sequences can be marred by artefacts. The radial-volume-interpolated breath-hold examination (VIBE) sequence is a motion-robust fat-suppressed T1W sequence which has demonstrated value in paediatric and body imaging. The purpose of our study was to evaluate its role in assessing the orbit and to compare it with routinely acquired sequences...
October 2015: British Journal of Radiology
https://www.readbyqxmd.com/read/25983363/parallel-magnetic-resonance-imaging-as-approximation-in-a-reproducing-kernel-hilbert-space
#15
Vivek Athalye, Michael Lustig, Martin Uecker
In Magnetic Resonance Imaging (MRI) data samples are collected in the spatial frequency domain (k-space), typically by time-consuming line-by-line scanning on a Cartesian grid. Scans can be accelerated by simultaneous acquisition of data using multiple receivers (parallel imaging), and by using more efficient non-Cartesian sampling schemes. To understand and design k-space sampling patterns, a theoretical framework is needed to analyze how well arbitrary sampling patterns reconstruct unsampled k-space using receive coil information...
April 1, 2015: Inverse Problems
https://www.readbyqxmd.com/read/25960254/non-cartesian-balanced-steady-state-free-precession-pulse-sequences-for-real-time-cardiac-mri
#16
Xue Feng, Michael Salerno, Christopher M Kramer, Craig H Meyer
PURPOSE: To develop a new spiral-in/out balanced steady-state free precession (bSSFP) pulse sequence for real-time cardiac MRI and compare it with radial and spiral-out techniques. METHODS: Non-Cartesian sampling strategies are efficient and robust to motion and thus have important advantages for real-time bSSFP cine imaging. This study describes a new symmetric spiral-in/out sequence with intrinsic gradient moment compensation and SSFP refocusing at TE = TR/2...
April 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/25953291/advances-in-t1-weighted-and-t2-weighted-imaging-in-the-abdomen-and-pelvis
#17
REVIEW
Justin M Ream, Andrew B Rosenkrantz
Utilization of abdominopelvic MR imaging continues to increase in volume and gain widespread clinical acceptance. Many factors such as diaphragmatic respiratory motion, bulk patient motion, and the need for large volumetric coverage while maintaining clinically feasible scan times have proven challenging for body applications of MRI. However, many advances in MR acquisition, including non-Cartesian T1-weighted and T2-weighted acquisitions, advanced Dixon sequences, and 3-dimensional volumetric T2-weighted imaging have helped to mitigate some of the issues which have hampered abdominopelvic MR...
May 2015: Radiologic Clinics of North America
https://www.readbyqxmd.com/read/25906343/mr-pet-evaluation-of-1-month-post-ablation-therapy-for-hepatocellular-carcinoma-preliminary-observations
#18
Miguel Ramalho, Mamdoh AlObaidy, Lauren M Burke, Brian M Dale, David A Gerber, Terence Z Wong, Richard C Semelka
PURPOSE: The purpose of the study was to evaluate the feasibility and protocol optimization of whole-body hybrid MR-PET system performed 1-month after post-locoregional thermoablative procedures for hepatocellular carcinomas (HCCs). MATERIALS AND METHODS: Eight patients (6 men and 2 women; mean age, 56.6 ± 5.5 years) with 9 ablated HCCs constituted our study population. Three readers interpreted the studies to determine the presence or absence of residual malignancy...
August 2015: Abdominal Imaging
https://www.readbyqxmd.com/read/25750620/comparing-different-stimulus-configurations-for-population-receptive-field-mapping-in-human-fmri
#19
Ivan Alvarez, Benjamin de Haas, Chris A Clark, Geraint Rees, D Samuel Schwarzkopf
Population receptive field (pRF) mapping is a widely used approach to measuring aggregate human visual receptive field properties by recording non-invasive signals using functional MRI. Despite growing interest, no study to date has systematically investigated the effects of different stimulus configurations on pRF estimates from human visual cortex. Here we compared the effects of three different stimulus configurations on a model-based approach to pRF estimation: size-invariant bars and eccentricity-scaled bars defined in Cartesian coordinates and traveling along the cardinal axes, and a novel simultaneous "wedge and ring" stimulus defined in polar coordinates, systematically covering polar and eccentricity axes...
2015: Frontiers in Human Neuroscience
https://www.readbyqxmd.com/read/25385670/graphical-programming-interface-a-development-environment-for-mri-methods
#20
Nicholas R Zwart, James G Pipe
PURPOSE: To introduce a multiplatform, Python language-based, development environment called graphical programming interface for prototyping MRI techniques. METHODS: The interface allows developers to interact with their scientific algorithm prototypes visually in an event-driven environment making tasks such as parameterization, algorithm testing, data manipulation, and visualization an integrated part of the work-flow. Algorithm developers extend the built-in functionality through simple code interfaces designed to facilitate rapid implementation...
November 2015: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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