Traveling Volunteers: A Multi-Vendor, Multi-Center Study on Reproducibility and Comparability of 4D Flow Derived Aortic Hemodynamics in Cardiovascular Magnetic Resonance

Background Implementation of four-dimensional flow magnetic resonance (4D Flow MR) in clinical routine requires awareness of confounders. Purpose To investigate inter-vendor comparability of 4D Flow MR derived aortic hemodynamic parameters, assess scan-rescan repeatability, and intra- and interobserver reproducibility. Study Type Prospective multicenter study. Population Fifteen healthy volunteers (age 24.5 +/- 5.3 years, 8 females). Field Strength/Sequence 3 T, vendor-provided and clinically used 4D Flow MR sequences of each site. Assessment Forward flow volume, peak velocity, average, and maximum wall shear stress (WSS) were assessed via nine planes (P1-P9) throughout the thoracic aorta by a single observer (AD, 2 years of experience). Inter-vendor comparability as well as scan-rescan, intra- and interobserver reproducibility were examined. Statistical Tests Equivalence was tested setting the 95% confidence interval of intraobserver and scan-rescan difference as the limit of clinical acceptable disagreement. Intraclass correlation coefficient (ICC) and Bland-Altman plots were used for scan-rescan reproducibility and intra- and interobserver agreement. A P-value <0.05 was considered statistically significant. ICCs >= 0.75 indicated strong correlation (>0.9: excellent, 0.75-0.9: good). Results Ten volunteers finished the complete study successfully. 4D flow derived hemodynamic parameters between scanners of three different vendors are not equivalent exceeding the equivalence range. P3-P9 differed significantly between all three scanners for forward flow (59.1 +/- 13.1 mL vs. 68.1 +/- 12.0 mL vs. 55.4 +/- 13.1 mL), maximum WSS (1842.0 +/- 190.5 mPa vs. 1969.5 +/- 398.7 mPa vs. 1500.6 +/- 247.2 mPa), average WSS (1400.0 +/- 149.3 mPa vs. 1322.6 +/- 211.8 mPa vs. 1142.0 +/- 198.5 mPa), and peak velocity between scanners I vs. III (114.7 +/- 12.6 cm/s vs. 101.3 +/- 15.6 cm/s). Overall, the plane location at the sinotubular junction (P1) presented most inter-vendor stability (forward: 78.5 +/- 15.1 mL vs. 80.3 +/- 15.4 mL vs. 79.5 +/- 19.9 mL [P = 0.368]; peak: 126.4 +/- 16.7 cm/s vs. 119.7 +/- 13.6 cm/s vs. 111.2 +/- 22.6 cm/s [P = 0.097]). Scan-rescan reproducibility and intra- and interobserver variability were good to excellent (ICC >= 0.8) with best agreement for forward flow (ICC >= 0.98). Data Conclusion The clinical protocol used at three different sites led to differences in hemodynamic parameters assessed by 4D flow. Level of Evidence 2 Technical Efficacy Stage 2