Arterial-Washout Temporal Profiling in CEUS LI-RADS: A Diagnostic Algorithm for Reducing Hepatocellular Carcinoma Misclassification

Purpose To determine whether combining the arterial phase onset time to washout onset time interval (AWTI) with washout onset time improves the accuracy of contrast-enhanced US (CEUS) Liver Imaging Reporting and Data System (LI-RADS) and reduces the incidence of hepatocellular carcinoma (HCC) being misclassified as LR-M. Materials and Methods CEUS and clinical data from patients with focal liver lesions (FLLs), collected between January 2019 and October 2024, were retrospectively analyzed. The AWTI was calculated for all FLLs with washout < 60 seconds. A revised classification was proposed: <i>(a)</i> washout < 45 seconds + AWTI < 21 seconds for LR-M; and <i>(b)</i> washout ≥ 45 seconds + AWTI ≥ 21 seconds for LR-5. Diagnostic performance of the revised classification was compared with that of the standard LI-RADS with washout < 60 seconds (and ≥60 seconds). Results The study included 352 patients (median age, 56 years [IQR, 46-65]; 284 male), each with one FLL. Among HCCs, 75.9% exhibited washout ≥ 60 seconds. In contrast, 75.0% of intrahepatic cholangiocarcinomas, 52.0% of metastatic liver carcinomas, and 66.7% of other malignancies demonstrated washout < 45 seconds. Of benign FLLs, 12.8% showed washout ≥ 60 seconds. Among FLLs classified as LR-5, 92.6% were HCCs; among FLLs classified as LR-M, 41.8% were HCCs. The optimal AWTI cutoff to distinguish LR-M from LR-5 was 21 seconds. The revised LR-M (washout < 45 seconds + AWTI < 21 seconds) significantly increased the positive predictive value to 92.6% (<i>P</i> < .05). The revised LR-5 (washout ≥ 45 seconds + AWTI ≥ 21 seconds) significantly improved the sensitivity and negative predictive value to 89.0% and 87.0%, respectively (both <i>P</i> < .05). The diagnostic accuracy and area under the receiver operating characteristic curve were 88.4% and 0.88, respectively, despite slight decreases in the specificity and positive predictive value. Conclusion Combining washout onset time with AWTI as an alternative for standard washout onset time (<60 sec/≥60 sec) reduced misclassification of HCC and significantly improved the diagnostic performance of CEUS LI-RADS for LR-M and LR-5. <b>Keywords:</b> Ultrasound, Reconstruction Algorithms, Diagnosis, Classification, Ultrasound-Contrast, Abdomen/GI, Liver, Contrast Agents-Intravenous, Efficacy Studies, Hepatocellular Carcinoma, Contrast-enhanced Ultrasound, Liver Imaging Reporting and Data System, Washout Time <i>Supplemental material is available for this article.</i> © RSNA, 2025 See also commentary by Hui and Chiang in this issue.