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Non cartesian MRI

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https://www.readbyqxmd.com/read/29261334/respiratory-motion-correction-for-free-breathing-3d-abdominal-mri-using-cnn-based-image-registration-a-feasibility-study
#1
Jun Lv, Ming Yang, Jue Zhang, Xiaoying Wang
OBJECTIVE: Free-breathing abdomen imaging requires non-rigid motion registration of unavoidable respiratory motion in 3D under-sampled datasets. In this work, we introduce an image registration method based on the convolutional neural network (CNN) to obtain motion-free abdominal images throughout the respiratory cycle. METHODS: Abdominal data were acquired from 10 volunteers using a 1.5T MRI system. The respiratory signal was extracted from the central-space spokes, and the acquired data were reordered in 3 bins according to the corresponding breathing signal...
December 20, 2017: British Journal of Radiology
https://www.readbyqxmd.com/read/29193380/optimization-and-validation-of-accelerated-golden-angle-radial-sparse-mri-reconstruction-with-self-calibrating-grappa-operator-gridding
#2
Thomas Benkert, Ye Tian, Chenchan Huang, Edward V R DiBella, Hersh Chandarana, Li Feng
PURPOSE: Golden-angle radial sparse parallel (GRASP) MRI reconstruction requires gridding and regridding to transform data between radial and Cartesian k-space. These operations are repeatedly performed in each iteration, which makes the reconstruction computationally demanding. This work aimed to accelerate GRASP reconstruction using self-calibrating GRAPPA operator gridding (GROG) and to validate its performance in clinical imaging. METHODS: GROG is an alternative gridding approach based on parallel imaging, in which k-space data acquired on a non-Cartesian grid are shifted onto a Cartesian k-space grid using information from multicoil arrays...
November 28, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28940748/rapid-compressed-sensing-reconstruction-of-3d-non-cartesian-mri
#3
Corey A Baron, Nicholas Dwork, John M Pauly, Dwight G Nishimura
PURPOSE: Conventional non-Cartesian compressed sensing requires multiple nonuniform Fourier transforms every iteration, which is computationally expensive. Accordingly, time-consuming reconstructions have slowed the adoption of undersampled 3D non-Cartesian acquisitions into clinical protocols. In this work we investigate several approaches to minimize reconstruction times without sacrificing accuracy. METHODS: The reconstruction problem can be reformatted to exploit the Toeplitz structure of matrices that are evaluated every iteration, but it requires larger oversampling than what is strictly required by nonuniform Fourier transforms...
September 23, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28937270/feasibility-of-free-breathing-lung-mri-for-radiotherapy-using-non-cartesian-k-space-acquisition-schemes
#4
Shivani Kumar, Robba Rai, Alto Stemmer, Sonal Josan, Lois Holloway, Shalini Vinod, Daniel Moses, Gary Liney
OBJECTIVE: To test a free-breathing MRI protocol for anatomical and functional assessment during lung cancer radiotherapy by assessing two non-Cartesian acquisition schemes based on T1 weighted 3D gradient recall echo sequence: (i) stack-of stars (StarVIBE) and (ii) spiral (SpiralVIBE) trajectories. METHODS: MR images on five healthy volunteers were acquired on a wide bore 3T scanner (MAGNETOM Skyra, Siemens Healthcare, Erlangen, Germany). Anatomical image quality was assessed on: (1) free breathing (StarVIBE), (2) the standard clinical sequence (volumetric interpolated breath-hold examination, VIBE) acquired in a 20 second (s) compliant breath-hold and (3) 20 s non-compliant breath-hold...
December 2017: British Journal of Radiology
https://www.readbyqxmd.com/read/28885742/adaptive-bulk-motion-exclusion-for-improved-robustness-of-abdominal-magnetic-resonance-imaging
#5
Bjorn Stemkens, Thomas Benkert, Hersh Chandarana, Mark E Bittman, Cornelis A T Van den Berg, Jan J W Lagendijk, Daniel K Sodickson, Rob H N Tijssen, Kai Tobias Block
Non-Cartesian magnetic resonance imaging (MRI) sequences have shown great promise for abdominal examination during free breathing, but break down in the presence of bulk patient motion (i.e. voluntary or involuntary patient movement resulting in translation, rotation or elastic deformations of the body). This work describes a data-consistency-driven image stabilization technique that detects and excludes bulk movements during data acquisition. Bulk motion is identified from changes in the signal intensity distribution across different elements of a multi-channel receive coil array...
November 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28875538/a-generalized-parametric-response-mapping-method-for-analysis-of-multi-parametric-imaging-a-feasibility-study-with-application-to-glioblastoma
#6
Anthony Lausch, Timothy Pok-Chi Yeung, Jeff Chen, Elton Law, Yong Wang, Benedetta Urbini, Filippo Donelli, Luigi Manco, Enrico Fainardi, Ting-Yim Lee, Eugene Wong
PURPOSE: Parametric response map (PRM) analysis of functional imaging has been shown to be an effective tool for early prediction of cancer treatment outcomes and may also be well-suited toward guiding personalized adaptive radiotherapy (RT) strategies such as sub-volume boosting. However, the PRM method was primarily designed for analysis of longitudinally acquired pairs of single-parameter image data. The purpose of this study was to demonstrate the feasibility of a generalized parametric response map analysis framework, which enables analysis of multi-parametric data while maintaining the key advantages of the original PRM method...
September 6, 2017: Medical Physics
https://www.readbyqxmd.com/read/28844222/recent-advances-in-parallel-imaging-for-mri
#7
REVIEW
Jesse Hamilton, Dominique Franson, Nicole Seiberlich
Magnetic Resonance Imaging (MRI) is an essential technology in modern medicine. However, one of its main drawbacks is the long scan time needed to localize the MR signal in space to generate an image. This review article summarizes some basic principles and recent developments in parallel imaging, a class of image reconstruction techniques for shortening scan time. First, the fundamentals of MRI data acquisition are covered, including the concepts of k-space, undersampling, and aliasing. It is demonstrated that scan time can be reduced by sampling a smaller number of phase encoding lines in k-space; however, without further processing, the resulting images will be degraded by aliasing artifacts...
August 2017: Progress in Nuclear Magnetic Resonance Spectroscopy
https://www.readbyqxmd.com/read/28560829/dynamic-phosphocreatine-imaging-with-unlocalized-ph-assessment-of-the-human-lower-leg-muscle-following-exercise-at-3t
#8
Oleksandr Khegai, Guillaume Madelin, Ryan Brown, Prodromos Parasoglou
PURPOSE: To develop a high temporal resolution imaging method that measures muscle-specific phosphocreatine (PCr) resynthesis time constant (τPCr ) and pH changes in muscles of the lower leg following exercise on a clinical 3T MRI scanner. METHODS: We developed a frequency-selective 3D non-Cartesian FLORET sequence to measure PCr with 17-mm nominal isotropic resolution (28 mm actual resolution) and 6-s temporal resolution to capture dynamic metabolic muscle activity...
May 30, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28560040/spatially-segmented-undersampled-mri-temperature-reconstruction-for-transcranial-mr-guided-focused-ultrasound
#9
Pooja Gaur, Beat Werner, Xue Feng, Samuel W Fielden, Craig H Meyer, William A Grissom
BACKGROUND: Volumetric thermometry with fine spatiotemporal resolution is desirable to monitor MR-guided focused ultrasound (MRgFUS) procedures in the brain, but requires some form of accelerated imaging. Accelerated MR temperature imaging methods have been developed that undersample k-space and leverage signal correlations over time to suppress the resulting undersampling artifacts. However, in transcranial MRgFUS treatments, the water bath surrounding the skull creates signal variations that do not follow those correlations, leading to temperature errors in the brain due to signal aliasing...
2017: Journal of Therapeutic Ultrasound
https://www.readbyqxmd.com/read/28486977/rapid-cartesian-versus-radial-acquisition-comparison-of-two-sequences-for-hepatobiliary-phase-mri-at-3-tesla-in-patients-with-impaired-breath-hold-capabilities
#10
Johannes Budjan, Philipp Riffel, Melissa M Ong, Stefan O Schoenberg, Ulrike I Attenberger, Daniel Hausmann
BACKGROUND: Hepatocyte-specific gadolinium based contrast agents (HSCA) provide substantial information for the classification of liver lesions in magnetic resonance imaging (MRI). However, breathing artifacts which reduce image quality and diagnostic confidence of hepatobiliary phase acquisitions are regularly observed in clinical routine. The aim of this study was to evaluate two approaches to reduce breathing artifacts for hepatobiliary phase imaging. METHODS: Twenty minutes after administration of a HSCA (gadoxetic acid), a T1-weighted VIBE sequence with radial k-space sampling (radialVIBE, 180 s acquisition time in free breathing) and a highly accelerated Cartesian VIBE with Dixon fat separation (CD-VIBE, CAIPIRINHA acceleration with r = 2 × 2, breath-hold 8-10 s) were acquired in 35 patients (12 female, 57 ± 13 years), who showed breath-holding difficulties in early phases of the examinations...
May 9, 2017: BMC Medical Imaging
https://www.readbyqxmd.com/read/28185433/model-based-iterative-reconstruction-for-single-shot-epi-at-7t
#11
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...
December 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28129150/the-spurs-algorithm-for-resampling-an-irregularly-sampled-signal-onto-a-cartesian-grid
#12
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/28048297/th-ef-bra-08-a-novel-technique-for-estimating-volumetric-cine-mri-vc-mri-from-multi-slice-sparsely-sampled-cine-images-using-motion-modeling-and-free-form-deformation
#13
W Harris, F Yin, C Wang, Z Chang, J Cai, Y Zhang, L Ren
PURPOSE: To develop a technique to estimate on-board VC-MRI using multi-slice sparsely-sampled cine images, patient prior 4D-MRI, motion-modeling and free-form deformation for real-time 3D target verification of lung radiotherapy. METHODS: A previous method has been developed to generate on-board VC-MRI by deforming prior MRI images based on a motion model(MM) extracted from prior 4D-MRI and a single-slice on-board 2D-cine image. In this study, free-form deformation(FD) was introduced to correct for errors in the MM when large anatomical changes exist...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28034638/free-breathing-whole-heart-3d-cine-mri-with-self-gated-cartesian-trajectory
#14
M Usman, B Ruijsink, M S Nazir, G Cruz, C Prieto
PURPOSE: To present a method that uses a novel free-running self-gated acquisition to achieve isotropic resolution in whole heart 3D Cartesian cardiac CINE MRI. MATERIAL AND METHODS: 3D cardiac CINE MRI using navigator gating results in long acquisition times. Recently, several frameworks based on self-gated non-Cartesian trajectories have been proposed to accelerate this acquisition. However, non-Cartesian reconstructions are computationally expensive due to gridding, particularly in 3D...
May 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/27943402/autocalibrating-motion-corrected-wave-encoding-for-highly-accelerated-free-breathing-abdominal-mri
#15
Feiyu Chen, Tao Zhang, Joseph Y Cheng, Xinwei Shi, John M Pauly, Shreyas S Vasanawala
PURPOSE: To develop a motion-robust wave-encoding technique for highly accelerated free-breathing abdominal MRI. METHODS: A comprehensive 3D wave-encoding-based method was developed to enable fast free-breathing abdominal imaging: (a) auto-calibration for wave-encoding was designed to avoid extra scan for coil sensitivity measurement; (b) intrinsic butterfly navigators were used to track respiratory motion; (c) variable-density sampling was included to enable compressed sensing; (d) golden-angle radial-Cartesian hybrid view-ordering was incorporated to improve motion robustness; and (e) localized rigid motion correction was combined with parallel imaging compressed sensing reconstruction to reconstruct the highly accelerated wave-encoded datasets...
November 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27831865/the-spurs-algorithm-for-resampling-an-irregularly-sampled-signal-onto-a-cartesian-grid
#16
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...
February 2017: 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
#17
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
#18
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...
November 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
#19
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...
January 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/27373796/adding-muscle-where-you-need-it-non-uniform-hypertrophy-patterns-in-elite-sprinters
#20
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
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