Gadoxetate-enhanced MRI Transitional Phase Parenchymal Signal: Effect on Washout and LI-RADS Diagnostic Performance...

Background At gadoxetate-enhanced MRI, extending nonperipheral washout to the transitional phase (TP) may reduce specificity for hepatocellular carcinoma (HCC) diagnosis. Purpose To compare the diagnostic performance of the Liver Imaging Reporting and Data System (LI-RADS) according to different washout assessments incorporating TP liver parenchymal signal intensity at gadoxetate-enhanced MRI and to identify factors associated with hyperintense TP liver parenchyma. Materials and Methods This retrospective study included patients who underwent gadoxetate-enhanced MRI and subsequent hepatic resection or liver transplant between January 2019 and December 2020. Signal intensity of TP liver parenchyma was assessed relative to the portal vein and categorized as hypo-, iso-, or hyperintense. Washout was defined as (a) confined to the portal venous phase (PVP) only, consistent with LI-RADS version 2018 (PVP-only); (b) extending to the TP regardless of TP liver parenchymal signal intensity (TP-all); and (c) extending to the TP only when TP liver parenchymal signal was hypointense or isointense (TP-iso/hypo). Sensitivity and specificity of LR-5 (ie, definitely HCC) were compared across these definitions using generalized estimating equations. Univariable and multivariable logistic regression analyses were performed to identify predictors of hyperintense TP parenchyma. Results A total of 438 patients (mean age, 60 years ± 9.1 [SD]; 345 men) with 558 hepatic observations were included; 25.6% of patients (112 of 438) showed hyperintense liver parenchyma in the TP, whereas 51.6% (226 of 438) showed isointense liver parenchyma and 22.8% (100 of 438) showed hypointense signal. Compared with PVP-only, TP-iso/hypo showed higher sensitivity (77.8% [332 of 427 patients] vs 70.7% [302 of 427]; P < .001) without evidence of a reduction in specificity (96.2% [126 of 131 patients] vs 96.9% [127 of 131]; P = .95). Low body mass index (adjusted odds ratio [OR], 0.89; P = .003), low bilirubin (adjusted OR, 0.62; P = .03), and high cardiac index (adjusted OR, 2.89; P = .03) were associated with hyperintense TP liver parenchyma. Conclusion Extending nonperipheral washout to the TP at gadoxetate-enhanced MRI while considering TP liver parenchymal signal intensity improved the diagnostic performance of LI-RADS for HCC. © RSNA, 2026 Supplemental material is available for this article. See also the editorial by Kim and Yoo in this issue.