Repeatability and reproducibility of 2D and 3D hepatic MR elastography with rigid and flexible drivers at end-expiration and end-inspiration in healthy volunteers

Purpose: To evaluate the repeatability and reproducibility of 2D and 3D hepatic MRE with rigid and flexible drivers at end-expiration and end-inspiration in healthy volunteers. Materials and methods: Nine healthy volunteers underwent two same-day MRE exams separated by a 5- to 10-min break. In each exam, 2D and 3D MRE scans were performed, each under four conditions (2 driver types [rigid, flexible] × 2 breath-hold phases [end-expiration, end-inspiration]). Repeatability (measurements under identical conditions) and reproducibility (measurements under different conditions) were analyzed by calculating bias, limit of agreement, repeatability coefficient (RC), reproducibility coefficient (RDC), intraclass correlation coefficient (ICC), and concordance correlation coefficient (CCC), as appropriate. Results: For 2D MRE, RCs and ICCs range between 0.29–0.49 and 0.71–0.91, respectively. For 3D MRE, RCs and ICCs range between 0.16–0.26 and 0.84–0.96, respectively. Stiffness values were biased by breath-hold phase, being higher at end-inspiration than end-expiration, and the differences were significant for 3D MRE (p < 0.01). No bias was found between driver types. Inspiration vs. expiration RDCs and CCCs ranged between 0.30–0.54 and 0.61–0.72, respectively. Rigid vs. flexible driver RDCs and CCCs ranged between 0.10–0.44 and 0.79–0.94, respectively. Conclusion: This preliminary study suggests that 2D MRE and 3D MRE under most conditions potentially have good repeatability. Our result also points to the possibility that stiffness measured with the rigid and flexible drivers is reproducible. Reproducibility between breath-hold phases was modest, suggesting breath-hold phase might be a confounding factor in MRE-based stiffness measurement. However, larger studies are required to validate these preliminary results.