Utility of Corrected Effective Atomic Numbers in Differentiating Hepatocellular Carcinomas and Liver Metastases From Hepatic Hemangiomas.

Objective To examine whether malignant liver masses (hepatocellular carcinomas (HCCs)/liver metastases) can be differentiated from hepatic hemangiomas using corrected effective atomic numbers, which can eliminate the effect of fat on unenhanced CT images. Materials and methods An unenhanced and contrast-enhanced dual-energy CT scan was performed on 94 patients with 132 liver masses. Regions of interest with a diameter of 10 mm were placed in tumor areas without degeneration based on contrast-enhanced CT images. Corrected effective atomic numbers (Zeff) were calculated from the actual Zeff and liver fat value on unenhanced CT images using the following formula: corrected Zeff = [actual Zeff - 6.27 * liver fat value (%) / 100] / [1 - liver fat value (%) / 100]. The mean corrected Zeff of the HCC, liver metastasis, and hepatic hemangioma groups was compared. Results There were 43 HCCs, 40 metastases (17 from colon cancer and 23 from pancreatic cancer), and 49 hemangiomas. The mean corrected Zeff values were as follows: HCC 7.771 ± 0.123; metastasis 7.756 ± 0.204; and hemangioma 7.618 ± 0.114. A significant difference in corrected Zeff was found between hemangioma and both HCC and metastasis (p < 0.001), while no significant difference was observed between HCC and metastasis. Corrected Zeff≥7.666 distinguished malignant liver masses (HCC/metastasis) from hemangiomas with a sensitivity of 80.72% and specificity of 71.43% (AUC=0.771, 95% CI: 0.689-0.852). Conclusions A significant difference in corrected effective atomic number was found between malignant liver masses (hepatocellular carcinomas/liver metastases) and hepatic hemangiomas. No significant difference was found between hepatocellular carcinomas and liver metastases. A corrected Zeff ≥ 7.666 differentiated malignant liver masses from hepatic hemangiomas with 80.72% sensitivity and 71.43% specificity (AUC = 0.771).