[PUBLICATION] The impact of acceleration factors in 4D flow MRI

Original title: “Accelerated sequences of 4D flow MRI using GRAPPA and compressed sensing:
A comparison against conventional MRI and computational fluid dynamics” published online in
August 2022 in the journal Magnetic Resonance in Medicine ▸https://doi.org/10.1002/mrm.29404

Interest of the study

So-called “4D flow MRI” sequences provide an image of the blood flow velocity, both within a given volume and over the course of the cycle cardiac [1]. This promising technique provides non-invasive access to hemodynamic biomarkers such as flow rate, maximum velocities or even derived parameters (e.g. parietal friction, turbulence kinetic energy). However, the clinical use of 4D flow MRI remains underdeveloped due to the long duration of its use. acquisitions. Various techniques have been developed to speed up acquisition time: parallel imaging (e.g. GRAPPA, SENSE) or, more recently, Compressed Sensing [2,3].
The main objective of this study is to investigate the measurement errors induced by the GRAPPA and Compressed Sensing accelerations for flow characterization obtained with 4D flow MRI, in a well-controlled environment featuring complex flow patterns typical of those seen in the cardiovascular system.


« Accelerated sequences of 4D flow MRI
The MRI acquisitions and MFN simulations were then post-processed to allow their comparison following the recommendations of Puiseux et al. 2019 [4]. To compare The following quantities have been evaluated:


« Accelerated sequences of 4D flow MRI 2
Qualitatively, similar hemodynamic patterns were observed for all the modalities. In the video opposite, the non-accelerated acquisition (4D FLOW FS) is compared with the 4D FLOW FS. MFN simulation (CFD_HR), and to the same simulation under-resolved to match the MRI voxels (CFD_LR). Quantitatively, it was found that :


This study shows that highly accelerated Compressed Sensing acquisition enables obtain in vitro results very similar to those obtained with a non-accelerated sequence or with conventional GRAPPA-type accelerations (factors 2 or 3). However, it artifacts are inherent to the 4D flow MRI acquisition procedure: artifacts from spatial and velocity displacement, intravoxel phase shifting, partial volume effects… Although also has its limitations, the MFN appears to be a tool that can be used to study discrepancies.
[1] Markl M, Frydrychowicz A, Kozerke S, Hope M, Wieben O. 4D flow MRI. J Magn Reson Imaging. 2012;36(5):1015-1036. doi:10.1002/jmri.23632
[2] Ma LE, Markl M, Chow K, et al. Aortic 4D flow MRI in 2 minutes using compressed sensing, respiratory controlled adaptive k-space reordering, and inline reconstruction. Magn ResonMed. 2019;81:3675-3690.
[3] Pathrose A, Ma L, Berhane H, et al. Highly accelerated aortic 4D flow MRI using compressed sensing: performance at different acceleration factors in patients with aortic disease. Magn Reson Med. 2020;85:2174-2187.
[4] Puiseux T, Sewonu A, Meyrignac O, et al. Reconciling PC-MRI and CFD: An in-vitro study. NMR Biomed. 2019;32(5):e4063.
[5] YALES2BIO, ( https://imag.umontpellier.fr/~yales2bio/ )

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