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 [ABSTRACT FROM AUTHOR]