Highly accelerated 4D flow CMR using pseudo-spiral Cartesian undersampling at an acceleration factor of R=20 resulted in an acceptable underestimation (<10%) of peak velocity and peak WSS compared to an R=10 reference scan.
Observational (n=7)
No
Does highly accelerated 4D flow CMR using pseudo-spiral Cartesian acquisition and compressed sensing reconstruction provide accurate velocity and wall shear stress estimations compared to standard CMR in healthy carotids and phantoms?
Highly accelerated 4D flow CMR using pseudo-spiral Cartesian sampling and compressed sensing allows for acceptable (<10% error) estimation of peak velocity and wall shear stress at acceleration factors up to R=20.
BACKGROUND: 4D flow cardiovascular magnetic resonance (CMR) enables visualization of complex blood flow and quantification of biomarkers for vessel wall disease, such as wall shear stress (WSS). Because of the inherently long acquisition times, many efforts have been made to accelerate 4D flow acquisitions, however, no detailed analysis has been made on the effect of Cartesian compressed sensing accelerated 4D flow CMR at different undersampling rates on quantitative flow parameters and WSS. METHODS: We implemented a retrospectively triggered 4D flow CMR acquisition with pseudo-spiral Cartesian k-space filling, which results in incoherent undersampling of k-t space. Additionally, this strategy leads to small jumps in k-space thereby minimizing eddy current related artifacts. The pseudo-spirals were rotated in a tiny golden-angle fashion, which provides optimal incoherence and a variable density sampling pattern with a fully sampled center. We evaluated this 4D flow protocol in a carotid flow phantom with accelerations of R = 2-20, as well as in carotids of 7 healthy subjects (27 ± 2 years, 4 male) for R = 10-30. Fully sampled 2D flow CMR served as a flow reference. Arteries were manually segmented and registered to enable voxel-wise comparisons of both velocity and WSS using a Bland-Altman analysis. RESULTS: Magnitude images, velocity images, and pathline reconstructions from phantom and in vivo scans were similar for all accelerations. For the phantom data, mean differences at peak systole for the entire vessel volume in comparison to R = 2 ranged from - 2.3 to - 5.3% (WSS) and - 2.4 to - 2.2% (velocity) for acceleration factors R = 4-20. For the in vivo data, mean differences for the entire vessel volume at peak systole in comparison to R = 10 were - 9.9, - 13.4, and - 16.9% (WSS) and - 8.4, - 10.8, and - 14.0% (velocity), for R = 20, 25, and 30, respectively. Compared to single slice 2D flow CMR acquisitions, peak systolic flow rates of the phantom showed no differences, whereas peak systolic flow rates in the carotid artery in vivo became increasingly underestimated with increasing acceleration. CONCLUSION: Acquisition of 4D flow CMR of the carotid arteries can be highly accelerated by pseudo-spiral k-space sampling and compressed sensing reconstruction, with consistent data quality facilitating velocity pathline reconstructions, as well as quantitative flow rate and WSS estimations. At an acceleration factor of R = 20 the underestimation of peak velocity and peak WSS was acceptable (< 10%) in comparison to an R = 10 accelerated 4D flow CMR reference scan. Peak flow rates were underestimated in comparison with 2D flow CMR and decreased systematically with higher acceleration factors.
Peper et al. (Wed,) conducted a observational in Healthy subjects (n=7). Highly accelerated 4D flow CMR (R=20) vs. R=10 accelerated 4D flow CMR reference scan was evaluated on Mean difference in peak systolic wall shear stress (WSS) for entire vessel volume at R=20 vs R=10. Highly accelerated 4D flow CMR using pseudo-spiral Cartesian undersampling at an acceleration factor of R=20 resulted in an acceptable underestimation (<10%) of peak velocity and peak WSS compared to an R=10 reference scan.
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