Combined computed tomography and magnetic resonance imaging improves diagnosis of hepatocellular carcinoma ≤ 3.0 cm

Background/purpose Imaging diagnosis of hepatocellular carcinoma (HCC) is important, but the diagnostic performance of combined computed tomography (CT) and magnetic resonance imaging (MRI) using the Liver Imaging Reporting and Data System (LI-RADS) v2018 is not fully understood. We evaluated the clinical usefulness of combined CT and MRI for diagnosing HCC <= 3.0 cm using LI-RADS. Methods In 222 patients at risk of HCC who underwent both contrast-enhanced dynamic CT and gadoxetate disodium-enhanced MRI in 2017, 291 hepatic nodules <= 3.0 cm were retrospectively analyzed. Two radiologists performed image analysis and assigned a LI-RADS category to each nodule. The diagnostic performance for HCC was evaluated for CT, ordinary-MRI (washout confined to portal venous-phase), and modified-MRI (washout extended to hepatobiliary phase), and sensitivity and specificity were calculated for each modality. Generalized estimating equations were used to compare the diagnostic performance for HCC between combined CT and ordinary-MRI, combined CT and modified-MRI, and CT or MRI alone. p < 0.0062 (0.05/8) was considered statistically significant following Bonferroni correction for multiple comparisons. Results In 291 nodules, the sensitivity and specificity of CT, ordinary-MRI, and modified-MRI were 70.2% and 92.8%, 72.6% and 96.4%, and 84.6% and 88.0%, respectively. Compared with CT or MRI alone, both combined CT and ordinary-MRI (sensitivity, 83.7%; specificity, 95.2%) and combined CT and modified-MRI (sensitivity, 88.9%; specificity, 89.2%) showed significantly higher sensitivity (p <= 0.006), without a significant decrease in specificity (p >= 0.314). Conclusions Compared with CT or MRI alone, combined CT and MRI can increase sensitivity for diagnosing HCC <= 3.0 cm, without a significant decrease in specificity.