Accuracy, repeatability, reproducibility and reference ranges of primary sclerosing cholangitis specific biomarkers from quantitative MRCP.

Purpose: To assess the repeatability and reproducibility of quantitative MRCP-derived metrics generated from MRCP + software, designed for assessing biliary tree health.

Methods: Metric accuracy was assessed using a 3D-printed phantom containing 20 tubes with sinusoidally-varying diameters, simulating strictures and dilatations along ducts. Data from 80 participants (60 healthy volunteers and 20 with liver disease) was analysed in total. Repeatability and reproducibility of the quantitative metrics were assessed on Siemens, GE and Philips scanners at both 1.5T and 3T. All subjects were scanned on a Siemens Prisma 3T scanner which acted as the reference scanner. A subset of these participants also underwent scanning on the remaining scanners. Data from healthy volunteers was used to estimate the natural range of measured values (reference ranges). The reproducibility coefficient (RC) of 7 commonly reported quantitative metrics were compared between healthy controls and published values in primary sclerosing cholangitis (PSC) patients.

Results: The phantom analysis confirmed measurement accuracy with absolute bias of 0.0-0.1 for strictures and 0.1-0.2 for dilatations across all scanners (95% limits of agreement within ± 1.0). In vivo, RCs for the quantitative MRCP-derived metrics across the scanners ranged from: 12.4-25.4 for total number of ducts; 4.9-7.9 for number of dilatations; 3.3-6.5 for number of strictures; 4.6-9.8 mm for total length of dilatations; 26.5-51.7 mm for total length of strictures; and 4.4-6.8 for number of ducts with a stricture or dilatation. Repeatability on the same scanner was generally better than comparisons across scanners. Six metrics demonstrated sufficient cross-scanner reproducibility to distinguish healthy volunteers from PSC patients.

Conclusion: The precision of quantitative MRCP-derived metrics were sufficient to differentiate PSC and healthy subjects and should be well suited for multi-centre trials and assessment of biliary tree health.