Comparison of Gadoxetic Acid-enhanced Liver MRI and Contrast-enhanced CT for the Noninvasive Diagnosis of Hepatocellular Carcinoma

Magnetic resonance imaging (MRI) has been shown to outperform computed tomography (CT) in diagnosing hepatocellular carcinoma (HCC), although inconsistencies exist across studies. We compared the performance of CT and gadoxetic acid-enhanced MRI in diagnosing HCC according to various guidelines, and to assess the incremental value of a second-line examination. This retrospective multicenter study included patients at risk of developing HCC with focal liver lesions (FLLs) ≥10 mm. These patients underwent both contrast-enhanced CT and gadoxetic acid-enhanced MRI between January 2015 and June 2018. Four radiologists independently assessed the images using criteria from the Liver Imaging Reporting and Data System (LI-RADS), the Asian Pacific Association for the Study of the Liver (APASL), and the Korean Liver Cancer Association-National Cancer Center (KLCA-NCC) guidelines. The diagnostic performance of CT and MRI was compared across guidelines. In total, 1,590 FLLs (median size, 22.6 mm) were analyzed in 1,455 patients (median age, 59 years; male, 1,101). Sensitivity was higher with MRI than with CT for APASL (89.3% [95% CI: 87.7%, 90.8%] vs. 78.9% [95% CI: 77.0%, 80.8%], respectively) and KLCA-NCC (78.7% [95% CI: 76.7%, 85.0%] vs. 73.7% [95% CI: 71.6%, 75.7%], respectively) (p = 0.002 for both). However, LI-RADS showed lower sensitivity with MRI than with CT (70.6% [95% CI: 68.4%, 72.6%] vs. 74.7% [95% CI: 72.6%, 76.7%], p = 0.002), due to fewer nonperipheral washout. MRI re-categorized 22.4%, 32.2%, and 53.5% of non-HCC observations on CT as HCC with LI-RADS, KLCA-NCC, and APASL, respectively. CT re-classified 30.2%, 29.0%, and 25.8% of non-HCC observations on MRI as HCC with LI-RADS, KLCA-NCC, and APASL, respectively. The added value of gadoxetic acid-enhanced MRI after CT depends on the diagnostic criteria used. Restricting washout timing to the portal venous phase in LI-RADS reduces the sensitivity of gadoxetic acid-enhanced MRI relative to CT.