Low-KeV Virtual Monoenergetic Dual-Energy CT with Deep Learning Reconstruction for Assessing Hepatocellular Carcinoma

Purpose To evaluate the diagnostic performance of low-keV virtual monoenergetic imaging (VMI) using dual-energy CT (DECT) with deep learning image reconstruction (DLIR) in patients with hepatocellular carcinoma (HCC). MethodsThis retrospective study included patients with HCC undergoing DECT scans between February 2019 and March 2022. VMI was reconstructed with hybrid iterative reconstruction (HIR) at 70-keV (HIR70keV) and 40-keV (HIR40keV) and DLIR at 40-keV (DLIR40keV). Two radiologists calculated the contrast-to-noise ratio (CNR) of the HCC. The possible presence of HCC was assessed by two additional radiologists. CNR was compared using Friedman's test. Diagnostic performance was compared between three groups using Cochran's Q test and jackknife alternative free-response receiver operating characteristic analysis. Results Thirty-two patients (mean age 73.19 +/- 11.86, 23 males) with 36 HCCs were enrolled. The CNR of DLIR40keV was significantly higher than HIR70keV and HIR40keV (p < 0.001 and 0.001). The sensitivities for the detection of HCC were HIR70keV, 63.9%; HIR40keV, 72.2%; DLIR40 keV, 83.3%, and HIR70keV, 52.8%; HIR40keV, 61.1%; DLIR40 keV, 77.8% for observers 1 and 2, respectively. DLIR40keV sensitivity was significantly higher than HIR70keV on both readers (p = 0.020 and 0.013). The figures of merit (FOM) were HIR70keV, 0.86; HIR40keV, 0.92; DLIR40 keV, 0.96, and HIR70keV, 0.84; HIR40keV, 0.90; and DLIR40 keV, 0.94 for observers 1 and 2, respectively. For both observers, DLIR40keV FOM was significantly higher than HIR70keV (p = 0.013 and 0.012). Conclusion DLIR40keV achieved the best CNR among the three groups. HCC detectability was significantly improved at DLIR40keV compared to HIR70keV.