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Your search keyword '"MR flow imaging"' showing total 3 results
Start Over Descriptor "MR flow imaging" Publisher wiley
3 results on '"MR flow imaging"'

1. Comparison of fast acquisition strategies in whole-heart four-dimensional flow cardiac MR: Two-center, 1.5 Tesla, phantom and in vivo validation study

Author

Garg, P, Westenberg, JJM, van den Boogaard, PJ, Swoboda, P, Aziz, R, Foley, JRJ, Fent, GJ, Tyl, FGJ, Coratella, L, ElBaz, MSM, van der Geest, RJ, Higgins, DM, Greenwood, JP, and Plein, S

Subjects
validation, phase-contrast magnetic resonance imaging, MR flow imaging, flow quantification, 4D flow cardiac MR
Abstract

Purpose\ud To validate three widely‐used acceleration methods in four‐dimensional (4D) flow cardiac MR; segmented 4D‐spoiled‐gradient‐echo (4D‐SPGR), 4D‐echo‐planar‐imaging (4D‐EPI), and 4D‐k‐t Broad‐use Linear Acquisition Speed‐up Technique (4D‐k‐t BLAST).\ud \ud Materials and Methods\ud Acceleration methods were investigated in static/pulsatile phantoms and 25 volunteers on 1.5 Tesla MR systems. In phantoms, flow was quantified by 2D phase‐contrast (PC), the three 4D flow methods and the time‐beaker flow measurements. The later was used as the reference method. Peak velocity and flow assessment was done by means of all sequences. For peak velocity assessment 2D PC was used as the reference method. For flow assessment, consistency between mitral inflow and aortic outflow was investigated for all pulse‐sequences. Visual grading of image quality/artifacts was performed on a four‐point‐scale (0 = no artifacts; 3 = nonevaluable).\ud \ud Results\ud For the pulsatile phantom experiments, the mean error for 2D PC = 1.0 ± 1.1%, 4D‐SPGR = 4.9 ± 1.3%, 4D‐EPI = 7.6 ± 1.3% and 4D‐k‐t BLAST = 4.4 ± 1.9%. In vivo, acquisition time was shortest for 4D‐EPI (4D‐EPI = 8 ± 2 min versus 4D‐SPGR = 9 ± 3 min, P

Published
2018

2. Assessment of Reynolds stress components and turbulent pressure loss using 4D flow MRI with extended motion encoding.

Author

Haraldsson H, Kefayati S, Ahn S, Dyverfeldt P, Lantz J, Karlsson M, Laub G, Ebbers T, and Saloner D

Subjects
Algorithms, Blood Flow Velocity, Computer Simulation, Constriction, Pathologic physiopathology, Humans, Hydrodynamics, Imaging, Three-Dimensional, Models, Cardiovascular, Motion, Phantoms, Imaging, Poisson Distribution, Pressure, Reproducibility of Results, Stress, Mechanical, Magnetic Resonance Imaging methods
Abstract

Purpose: To measure the Reynolds stress tensor using 4D flow MRI, and to evaluate its contribution to computed pressure maps., Methods: A method to assess both velocity and Reynolds stress using 4D flow MRI is presented and evaluated. The Reynolds stress is compared by cross-sectional integrals of the Reynolds stress invariants. Pressure maps are computed using the pressure Poisson equation-both including and neglecting the Reynolds stress., Result: Good agreement is seen for Reynolds stress between computational fluid dynamics, simulated MRI, and MRI experiment. The Reynolds stress can significantly influence the computed pressure loss for simulated (eg, -0.52% vs -15.34% error; P < 0.001) and experimental (eg, 306 ± 11 vs 203 ± 6 Pa; P < 0.001) data. A 54% greater pressure loss is seen at the highest experimental flow rate when accounting for Reynolds stress (P < 0.001)., Conclusion: 4D flow MRI with extended motion-encoding enables quantification of both the velocity and the Reynolds stress tensor. The additional information provided by this method improves the assessment of pressure gradients across a stenosis in the presence of turbulence. Unlike conventional methods, which are only valid if the flow is laminar, the proposed method is valid for both laminar and disturbed flow, a common presentation in diseased vessels. Magn Reson Med 79:1962-1971, 2018. © 2017 International Society for Magnetic Resonance in Medicine., (© 2017 International Society for Magnetic Resonance in Medicine.)

Published
2018
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3. Comparison of respiratory motion suppression techniques for 4D flow MRI.

Author

Dyverfeldt P and Ebbers T

Subjects
Aorta diagnostic imaging, Humans, Models, Biological, Movement, Phantoms, Imaging, Imaging, Three-Dimensional methods, Magnetic Resonance Imaging methods, Respiratory-Gated Imaging Techniques methods
Abstract

Purpose: The purpose of this work was to assess the impact of respiratory motion and to compare methods for suppression of respiratory motion artifacts in 4D Flow MRI., Methods: A numerical 3D aorta phantom was designed based on an aorta velocity field obtained by computational fluid mechanics. Motion-distorted 4D Flow MRI measurements were simulated and several different motion-suppression techniques were evaluated: Gating with fixed acceptance window size, gating with different window sizes in inner and outer k-space, and k-space reordering. Additionally, different spatial resolutions were simulated., Results: Respiratory motion reduced the image quality. All motion-suppression techniques improved the data quality. Flow rate errors of up to 30% without gating could be reduced to less than 2.5% with the most successful motion suppression methods. Weighted gating and gating combined with k-space reordering were advantageous compared with conventional fixed-window gating. Spatial resolutions finer than the amount of accepted motion did not lead to improved results., Conclusion: Respiratory motion affects 4D Flow MRI data. Several different motion suppression techniques exist that are capable of reducing the errors associated with respiratory motion. Spatial resolutions finer than the degree of accepted respiratory motion do not result in improved data quality. Magn Reson Med 78:1877-1882, 2017. © 2017 International Society for Magnetic Resonance in Medicine., (© 2017 International Society for Magnetic Resonance in Medicine.)

Published
2017
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