Aortic pulse wave velocity measurements with undersampled 4D flow-sensitive MRI: Comparison with 2D and algorithm determination

Purpose: To compare pulse wave velocity (PWV) measurements obtained from radially undersampled 4D phase-contrast magnetic resonance imaging (PC-MRI) with 2D PC measurements and to evaluate four PWV algorithms. Materials and Methods: PWV was computed from radially undersampled 3D, 3-directionally velocity-encoded PC-MRI (4D) acquisitions performed on a 3T MR scanner in 18 volunteers. High temporal resolution 2D PC scans serving as a reference standard were available in 14 volunteers. Four PWV algorithms were tested: time-to-upstroke (TTU), time-to-peak (TTP), time-to-foot (TTF), and cross-correlation (XCorr). Bland-Altman analysis was used to determine inter- and intraobserver reproducibility and to compare differences between algorithms. Differences in age and PWV measurements were analyzed with Student's t-tests. The variability of age-corrected data was assessed with a Brown-Forsythe analysis of variance (ANOVA) test. Results: 2D (4.6-5.3 m/s) and 4D (3.8-4.8 m/s) PWV results were in agreement with previously reported values in healthy subjects. Of the four PWV algorithms, the TTU, TTF, and XCorr algorithms gave similar and reliable results. Average biases of +0.30 m/s and -0.01 m/s were determined for intra- and interobserver variability, respectively. The Brown-Forsythe test revealed that no differences in variability could be found between 2D and 4D PWV measurements. Conclusion: 4D PC-MRI with radial undersampling provides reliable and reproducible measurements of PWV. TTU, TTF, and XCorr were the preferred PWV algorithms.