ABSTRACT
PURPOSE: To assess the variability of liver stiffness measurements using magnetic resonance elastography (MRE) at 1.5T, depending on different approaches of regions of interest (ROIs) drawing. MATERIAL AND METHODS: Fifty consecutive patients with successful liver MRE were included. There were 32 men and 18 women with a mean age of 52±14 (SD) years (range: 20-85 years). MRE was acquired using a gradient recalled-echo MRE sequence. At the level of the portal bifurcation, one observer drawn in the right liver first 3 elliptical ROI and then one free-hand ROI, as large as possible based on the confidence map and the anatomy. Three additional elliptical ROIs were further drawn on the slice above and 3 other on the slice below, for a total of 9 elliptical ROIs. The average value of liver stiffness in the 3 elliptical ROIs of the central slice and the one from the 9 elliptical ROIs were computed. Three liver stiffness values were obtained for each patient from the 3 measurement methods (one free-hand ROI, 3 elliptical ROIs and 9 elliptical ROIs). Inter-method variability was assessed using the intra-class correlation coefficient (ICC) and Bland-Altman analysis. RESULTS: The variability between the 3 methods was excellent with ICC>0.978 (P<0.0001). The Bland-Altman analysis revealed high agreement between the 3 methods with bias<0.45kPa and limits of agreement<±1.13kPa. The variability was lower when comparing a large free-hand ROI and the 3-elliptical ROIs, than when comparing the 9-elliptical ROIs to one of the other methods. CONCLUSION: Our results show that the variability between the 3 methods of ROI drawing and placement is very low.
