Abstract
AIMS: To propose a modified liver imaging reporting and data system (LI-RADS) categorization for observations at noncontrast abbreviated magnetic resonance imaging (AMRI). MATERIAL AND METHODS: This retrospective study comprised consecutive patients with chronic liver disease who underwent contrast-enhanced MRI (CE-MRI) for hepatocellular carcinoma (HCC) screening between July 2022 and June 2024. An anonymized AMRI dataset comprising T2-weighted and diffusion-weighted imaging (DWI) sequences was read by two radiologists independently for morphology, signal intensity at T2-weighted MRI, and diffusion restriction. The diagnostic performance of the AMRI features was assessed using contrast-enhanced MRI diagnostic reports as the reference standard. A 3-tier LI-RADS was proposed comprising benign (AMRI-LR-1), equivocal (AMRI-LR-2), and malignant (AMRI-LR-3) categories. The AMRI features for categorization were derived based on the best performance for diagnosing benign and malignant CE-MRI observations. RESULTS: One hundred fifty-three LI-RADS observations were reported in CE-MRI scans. AMRI detected 136 observations with 88% accuracy (95% CI: 84.2-91.8%), 81.4% sensitivity (95% CI: 76.8-86%), and 95.1% specificity (95% CI: 92.6-97.6%). The best performance for diagnosing benign CE-MRI (LR-1 and LR-2) observations was achieved with a combination of well-defined morphology, marked T2-weighted hyperintensity, and absence of diffusion restriction (accuracy 86% [95% CI: 79-91%] and area under the ROC curve (AUC) 0.76 [95% CI: 0.64-0.89]) (AMRI-LR-1). For diagnosing a malignant CE-MRI (LR-4, 5, M, TIV) observation, a combination of mild to moderate T2-weighted hyperintensity and diffusion restriction yielded the best performance (accuracy 72% [95% CI: 63-79%] and AUC 0.71 [95% CI: 0.62-0.80]) (AMRI-LR-3). CONCLUSION: The proposed AMRI-LI-RADS may allow objective evaluation of observations at noncontrast AMRI and may guide appropriate management. However, multicenter validation studies with a larger number of patients should be performed.