The assessment of aortic pulse wave velocity using 4D flow magnetic resonance imaging: Methods comparison

Purpose: Compare various methods of transit time (TT) and consequently aortic Pulse Wave Velocity (aoPWV) estimation from 4D MRI (aoPWV=aortic length/TT), in terms of associations with age and Bramwell-Hill (BH aoPWV). Method: We studied 43 healthy subjects (48±17 yrs.) who had aortic 4DFlow MRI. Three strategies were used to estimate aoPWV: (S1) using flow curves in two aortic locations to calculate TT (ascending (AA) and distal descending aorta (dDA)) as a 2D-like strategy, (S2 and S3) using flow curves of the entire aortic path-line between dDA and AA to estimate TT with various methods: cross-correlation; Fourier and Wavelet or aoPVW by fitting a plan on the systolic upslope of flow curves. Results: Expected associations with age were found for the three strategies with strongest correlations for 3D-like strategies than 2D-like strategy (S2:r=0.75, S3:r=0.72, p<0.001, S1: r=0.55, p<0.001). Similar results were found for associations with BH aoPWV. Best results were obtained using the TT wavelet-based approach. Conclusion: Low temporal resolution of 4DFlow is compensated by aortic 3D coverage, leading to strong associations of aoPWV with age and BH aoPWV.