Phase‐contrast acceleration mapping with synchronized encoding

Schmidt, Simon; Bruschewski, Martin; Flassbeck, Sebastian; John, Kristine; Grundmann, Sven; Ladd, Mark E.; Schmitter, Sebastian

doi:10.1002/mrm.28948

Cited by 5 publications

(3 citation statements)

References 25 publications

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“…75 Schmidt et al modified a velocity-encoded sequence with synchronized encoding (SYNC SPI) to allow direct acceleration mapping by replacing the bipolar encoding gradients with tripolar gradient waveforms for the purpose of synchronization of the spatial and acceleration encoding time points. 76 Although it is thought that the effect depends on the design of the imaging sequence, this is a research topic that seems to be noteworthy in order to accurately measure the flow velocity, flow rate, and WSS.…”

Section: Trigger Timementioning

confidence: 99%

Quality Control for 4D Flow MR Imaging

Isoda

Fukuyama

2022

MRMS

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In recent years, 4D flow MRI has become increasingly important in clinical applications for the blood vessels in the whole body, heart, and cerebrospinal fluid. 4D flow MRI has advantages over 2D cine phasecontrast (PC) MRI in that any targeted area of interest can be analyzed post-hoc, but there are some factors to be considered, such as ensuring measurement accuracy, a long imaging time and post-processing complexity, and interobserver variability.Due to the partial volume phenomenon caused by low spatial and temporal resolutions, the accuracy of flow measurement in 4D flow MRI is reduced. For spatial resolution, it is recommended to include at least four voxels in the vessel of interest, and if possible, six voxels. In large vessels such as the aorta, large voxels can be secured and SNR can be maintained, but in small cerebral vessels, SNR is reduced, resulting in reduced accuracy. A temporal resolution of less than 40 ms is recommended. The velocity-to-noise ratio (VNR) of low-velocity blood flow is low, resulting in poor measurement accuracy. The use of dual velocity encoding (VENC) or multi-VENC is recommended to avoid velocity wrap around and to increase VNR. In order to maintain sufficient spatio-temporal resolution, a longer imaging time is required, leading to potential patient movement during examination and a corresponding decrease in measurement accuracy.For the clinical application of new technologies, including various acceleration techniques, in vitro and in vivo accuracy verification based on existing accuracy-validated 2D cine PC MRI and 4D flow MRI, as well as accuracy verification on the conservation of mass' principle, should be performed, and intraobserver repeatability, interobserver reproducibility, and test-retest reproducibility should be checked.

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Section: Trigger Timementioning

confidence: 99%

Quality Control for 4D Flow MR Imaging

Isoda

Fukuyama

2022

MRMS

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“…10 Such parameters can provide additional information for studying disease mechanisms, diagnosis, and treatment monitoring and planning. 4D flow MRI is also increasingly used for in vitro imaging of synthetic and biological flow phantoms, for example, to study underlying hemodynamic effects, 11,12 assess accuracy and precision of PC MRI hemodynamic measures, 13 predict surgical outcomes with rapid prototyping models, 14,15 and evaluate computational fluid dynamics modeling results. 16 Such in vitro scans offer advantages over in vivo scans, including prolonged scan times to support higher spatial/temporal resolutions and/or higher precision, controlled and repeatable acquisitions without motion artifacts, and comparisons with other velocity measures such as particle image velocimetry.…”

Section: Introductionmentioning

confidence: 99%

“…4D flow MRI is also increasingly used for in vitro imaging of synthetic and biological flow phantoms, for example, to study underlying hemodynamic effects, 11,12 assess accuracy and precision of PC MRI hemodynamic measures, 13 predict surgical outcomes with rapid prototyping models, 14,15 and evaluate computational fluid dynamics modeling results 16 …”

Section: Introductionmentioning

confidence: 99%

Toward accurate and fast velocity quantification with 3D ultrashort TE phase‐contrast imaging

Degenhardt,

Schmidt,

Aigner

et al. 2024

Magnetic Resonance in Med

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PurposeTraditional phase‐contrast MRI is affected by displacement artifacts caused by non‐synchronized spatial‐ and velocity‐encoding time points. The resulting inaccurate velocity maps can affect the accuracy of derived hemodynamic parameters. This study proposes and characterizes a 3D radial phase‐contrast UTE (PC‐UTE) sequence to reduce displacement artifacts. Furthermore, it investigates the displacement of a standard Cartesian flow sequence by utilizing a displacement‐free synchronized‐single‐point‐imaging MR sequence (SYNC‐SPI) that requires clinically prohibitively long acquisition times.Methods3D flow data was acquired at 3T at three different constant flow rates and varying spatial resolutions in a stenotic aorta phantom using the proposed PC‐UTE, a Cartesian flow sequence, and a SYNC‐SPI sequence as reference. Expected displacement artifacts were calculated from gradient timing waveforms and compared to displacement values measured in the in vitro flow experiments.ResultsThe PC‐UTE sequence reduces displacement and intravoxel dephasing, leading to decreased geometric distortions and signal cancellations in magnitude images, and more spatially accurate velocity quantification compared to the Cartesian flow acquisitions; errors increase with velocity and higher spatial resolution.ConclusionPC‐UTE MRI can measure velocity vector fields with greater accuracy than Cartesian acquisitions (although pulsatile fields were not studied) and shorter scan times than SYNC‐SPI. As such, this approach is superior to traditional Cartesian 3D and 4D flow MRI when spatial misrepresentations cannot be tolerated, for example, when computational fluid dynamics simulations are compared to or combined with in vitro or in vivo measurements, or regional parameters such as wall shear stress are of interest.

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4D flow MRI velocity uncertainty quantification

Rothenberger,

Zhang,

Markl

et al. 2024

Magnetic Resonance in Med

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PurposeAn automatic method is presented for estimating 4D flow MRI velocity measurement uncertainty in each voxel. The velocity distance (VD) metric, a statistical distance between the measured velocity and local error distribution, is introduced as a novel measure of 4D flow MRI velocity measurement quality.MethodsThe method uses mass conservation to assess the local velocity error variance and the standardized difference of means (SDM) velocity to estimate the velocity error correlations. VD is evaluated as the Mahalanobis distance between the local velocity measurement and the local error distribution. The uncertainty model is validated synthetically and tested in vitro under different flow resolutions and noise levels. The VD's application is demonstrated on two in vivo thoracic vasculature 4D flow datasets.ResultsSynthetic results show the proposed uncertainty quantification method is sensitive to aliased regions across various velocity‐to‐noise ratios and assesses velocity error correlations in four‐ and six‐point acquisitions with correlation errors at or under 3.2%. In vitro results demonstrate the method's sensitivity to spatial resolution, venc settings, partial volume effects, and phase wrapping error sources. Applying VD to assess in vivo 4D flow MRI in the aorta demonstrates the expected increase in measured velocity quality with contrast administration and systolic flow.ConclusionThe proposed 4D flow MRI uncertainty quantification method assesses velocity measurement error owing to sources including noise, intravoxel phase dispersion, and velocity aliasing. This method enables rigorous comparison of 4D flow MRI datasets obtained in longitudinal studies, across patient populations, and with different MRI systems.

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Phase‐contrast acceleration mapping with synchronized encoding

Abstract: This is an open access article under the terms of the Creat ive Commo ns Attri butio n-NonCo mmerc ial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Cited by 5 publications

References 25 publications

Quality Control for 4D Flow MR Imaging

Quality Control for 4D Flow MR Imaging

Toward accurate and fast velocity quantification with 3D ultrashort TE phase‐contrast imaging

4D flow MRI velocity uncertainty quantification

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