Examination of the Accuracy of Virtual Non-contrast Images of Hepatic Lesions in Photon Counting Detector CT

PURPOSE: The purpose of this study was to compare true non-contrast (TNC) images and virtual non-contrast (VNC) images obtained using photon-counting detector computed tomography (PCD-CT) and to evaluate the accuracy of VNC images in the assessment of hepatic lesions. METHODS: The study included 79 patients who underwent contrast-enhanced CT and were diagnosed with hepatic lesions. The hepatic lesions consisted of 19 cases of hepatocellular carcinoma, 22 cases of metastatic liver tumors, 20 cases of hemangiomas, and 18 cases of cysts. CT values and standard deviations of hepatic lesions and background liver parenchyma were measured on TNC images and on VNC images reconstructed from equilibrium-phase scans. Using the measured values, the contrast-to-noise ratio (CNR) of hepatic lesions was calculated, and CT values and CNRs of the lesions were compared between true TNC and VNC images. RESULTS: The CT values of hepatic lesions on TNC and VNC images were 37.5±15.1 and 38.7±16.1 HU, respectively, while those of background liver parenchyma were 61.2±5.91 and 64.3±6.02 HU, respectively; all demonstrated good agreement. The correlation coefficients of CT values between TNC and VNC images were 0.898 for hepatic lesions and 0.933 for background liver parenchyma. Furthermore, when analyzed by lesion type, no significant differences were observed in CT values and CNRs (p>0.05). CONCLUSION: The accuracy of VNC images for liver lesions was very high, and for typical hepatic lesions in particular, the findings suggest that TNC images may be omitted.