Comparison of compressed sensing and conventional 4D flow MRI for turbulent kinetic energy assessment in healthy participants and patients with aortic stenosis

This study aims to evaluate the feasibility of turbulent kinetic energy (TKE) assessments using compressed sensing (CS)-accelerated three-dimensional time-resolved phase-contrast magnetic resonance imaging (4D flow MRI) in patients with aortic stenosis (AS). Conventional and CS 4D flow MRI (R = 2 with GRAPPA and R = 7.7 with CS, respectively) were sequentially acquired for voxel-wise comparison in healthy participants and patients. Total TKE was measured in both the ascending aorta (AAo) and the whole aortic region. The difference between GRAPPA and CS was expressed as the ratio of (CS 4D flow - Conventional 4D flow) to (Conventional 4D flow). A two-tailed paired t-test was used to assess statistical significance. In healthy participants, the maximum total TKE (TKE_max) measured by CS 4D flow MRI was substantially higher than that obtained with conventional 4D flow MRI, showing a 95.4% increase in the AAo region (0.74 ± 0.43 mJ by GRAPPA vs. 1.17 ± 0.72 mJ by CS; P = 0.053) and a 207.7% increase in the whole aortic region (1.13 ± 0.73 mJ by GRAPPA vs. 2.13 ± 0.95 mJ by CS; P = 0.006). In patients with AS, CS 4D flow MRI showed good agreement with conventional imaging, with only a 5.0% difference in TKE_max at the AAo (14.0 ± 4.6 mJ by GRAPPA vs. 14.8 ± 5.5 mJ by CS; P = 0.129) and a 7.4% difference in the whole region (16.3 ± 5.5 mJ by GRAPPA vs. 17.6 ± 6.5 mJ by CS; P = 0.050). CS 4D flow MRI demonstrated agreement, showing insignificant differences in total TKE measurements specifically within the AAo for AS patients. In healthy participants, CS-based TKE assessment showed larger relative differences compared with conventional 4D flow MRI, likely reflecting a low-TKE effect.