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Objective:
For liver stiffness measurement (LSM) using magnetic resonance elastography (MRE), it is unclear whether free drawing of region-of-interest (ROI) with or without including intrahepatic segmental vessels can affect the result of hepatic fibrosis. We aimed to investigate the ROI drawing avoiding intrahepatic segmental vessels can affect the LSM in MRE.

Materials and Methods:
In this institutional review board–approved, prospective study, 95 participants with successful 2-dimensional (2D) gradient recalled-echo MRE before hepatic surgery for resection of a primary hepatic tumor (n = 51) or living liver donation (n = 64) were included. LSMs were acquired by manually drawing ROIs on the obtained elastogram two times for each participant. First, the conventional LSM was determined by manually drawing free ROIs as large as possible on the elastogram within the 95% confidence region, staying 1 cm within the liver capsule and excluding large vessels, the central biliary tree, gallbladder, hepatic lesion and artifacts. In addition to the conventional LSM, the modified LSM was determined avoiding any intrahepatic segmental vascular intensity identifiable on magnitude image. LSMs obtained by two methods were compared with paired sample signed-rank test in all participants, and subgroups with and without hepatic fibrosis. The diagnostic performance of the two methods for the diagnosis of any fibrosis (= F1), advanced fibrosis (= F3), and cirrhosis (F4) was compared with the reference standard of surgical specimen using McNemar’s test, chi-square test, and Delong’s test. The optimal cutoff of LSM in predicting the stage of hepatic fibrosis was applied as follows: 2.32 kPa for = F1, 3.02 kPa for = F3, 4.23 kPa for F4 by reference to a previous document.

Results:
The modified LSM was larger than the conventional LSM in all participants (median, [interquartile range]; 2.4 kPa [1.8, 3.7]) vs. 2.2 kPa [1.7, 3.3]), in participants with fibrosis (3.7 kPa [3.2, 5.0] vs. 3.3 kPa [2.8, 4.6]), and in participants without fibrosis (1.7 kPa [1.6, 1.9] vs 1.7 kPa [1.6, 1.9]) (p < .001). For diagnosis of advanced fibrosis (= F3), the modified method shows higher sensitivity (0.841 vs. 0.659, p = 0.013), accuracy (0.905 vs. 0.832, p = 0.045), and area under the curve (0.901 vs. 0.820, p = 0.009) than the conventional method. There was no significant difference in diagnostic performance between two methods for diagnosing any fibrosis (= F1) or cirrhosis (F4).

Conclusion:
Despite excellent intermethod agreements, the exclusion of intrahepatic segmental vascular intensity from ROIs affected LSM in MRE. Compared to the method including intrahepatic segmental vessels, the LSM measured by the method avoiding intrahepatic segmental vessels was larger. Compared to the conventional method, the method avoiding intrahepatic segmental vessels showed superior performance in diagnosing advanced hepatic fibrosis (= F3).