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

Introduction: 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.
Methods: 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.
Results: In total, 1590 FLLs (median size, 22.6 mm) were analyzed in 1445 patients (median age, 59 years; male, 1101). 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.
Conclusion: 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.

引言：现有研究表明，磁共振成像（MRI）在肝细胞癌（HCC）诊断中优于计算机断层扫描（CT），但不同研究间尚存分歧。本研究针对多种临床指南，对比了CT与钆塞酸增强MRI在HCC诊断中的效能，并评估二线检查的增量价值。
方法：本项回顾性多中心研究纳入存在HCC发病风险且合并直径≥10mm肝脏局灶性病变（FLLs）的患者。所有受试者于2015年1月至2018年6月期间均接受了增强CT与钆塞酸增强MRI检查。4名放射科医师分别依据肝脏影像报告和数据系统（LI-RADS）、亚太肝脏研究学会（APASL）及韩国肝癌学会-国家癌症中心（KLCA-NCC）的指南标准独立阅片，并对比不同指南下两种影像检查的诊断效能。
结果：本研究共纳入1445例患者（中位年龄59岁，男性1101例），共计分析1590个FLLs（中位直径22.6mm）。针对APASL与KLCA-NCC指南，MRI的诊断灵敏度均高于CT：APASL指南下分别为89.3%[95%置信区间（CI）：87.7%~90.8%]与78.9%[95%CI：77.0%~80.8%]；KLCA-NCC指南下分别为78.7%[95%CI：76.7%~85.0%]与73.7%[95%CI：71.6%~75.7%]（两组P值均为0.002）。但LI-RADS指南下，MRI的诊断灵敏度低于CT（70.6%[95%CI：68.4%~72.6%] vs 74.7%[95%CI：72.6%~76.7%]，P=0.002），这与MRI中非外周廓清征象占比更低有关。依据LI-RADS、KLCA-NCC及APASL指南标准，MRI可分别将CT检出的22.4%、32.2%及53.5%的非HCC征象重新归类为HCC；而CT则可分别将MRI检出的30.2%、29.0%及25.8%的非HCC征象重新归类为HCC。
结论：CT检查后追加钆塞酸增强MRI的附加价值取决于所采用的诊断标准。LI-RADS指南中将廓清时限限定于门静脉期，会导致钆塞酸增强MRI相对于CT的诊断灵敏度降低。