Utilization of a Machine Learning Algorithm for the Application of Ancillary Features to LI-RADS Categories LR3 and LR4 on Gadoxetate Disodium-Enhanced MRI

SIMPLE SUMMARY: In the Liver Imaging Reporting and Data System (LI-RADS), liver observations are categorized as LR1-LR5 according to the probability of benign and hepatoma on the basis of major features. Subsequent adjustment is allowed using ancillary features (AFs). However, the LI-RADS does not provide specific guidelines. In this study, we determined the utilization of a machine-learning-based strategy of applying AFs to LR3/4 on MRI. Our decision tree algorithm of applying AFs for LR3/4 provides significantly higher AUC, sensitivity, and accuracy than those of other methods, albeit reduced specificity. These appear to be usefully employed in certain circumstances in which there is a focus on the early detection of hepatoma. ABSTRACT: Background: This study aimed to identify the important ancillary features (AFs) and determine the utilization of a machine-learning-based strategy for applying AFs for LI-RADS LR3/4 observations on gadoxetate disodium-enhanced MRI. Methods: We retrospectively analyzed MRI features of LR3/4 determined with only major features. Uni- and multivariate analyses and random forest analysis were performed to identify AFs associated with HCC. A decision tree algorithm of applying AFs for LR3/4 was compared with other alternative strategies using McNemar’s test. Results: We evaluated 246 observations from 165 patients. In multivariate analysis, restricted diffusion and mild–moderate T2 hyperintensity showed independent associations with HCC (odds ratios: 12.4 [p < 0.001] and 2.5 [p = 0.02]). In random forest analysis, restricted diffusion is the most important feature for HCC. Our decision tree algorithm showed higher AUC, sensitivity, and accuracy (0.84, 92.0%, and 84.5%) than the criteria of usage of restricted diffusion (0.78, 64.5%, and 76.4%; all p < 0.05); however, our decision tree algorithm showed lower specificity than the criterion of usage of restricted diffusion (71.1% vs. 91.3%; p < 0.001). Conclusion: Our decision tree algorithm of applying AFs for LR3/4 shows significantly increased AUC, sensitivity, and accuracy but reduced specificity. These appear to be more appropriate in certain circumstances in which there is an emphasis on the early detection of HCC.