Differentiation of liver abscess from liver metastasis using dual-energy spectral CT quantitative parameters

Objective: To explore the value of single source dual-energy spectral CT quantitative parameters in differential diagnosis of liver abscess and liver metastatic tumor. Methods: Fifty-one patients with 73 liver lesions (28 liver abscesses and 45 liver metastases) underwent plain and contrast-enhanced spectral CT scans. The fat and blood concentrations and CT values of 40-140 keV monochromatic images were measured to calculate effective atomic number (Eff-Z) and a slope (K): [CT(40 keV)-CT(140 keV)/100] for the cystic component on the plain scan images. The iodine concentration of the lesion wall on the enhanced three-phase images were measured and normalized to that of aorta for normalized iodine concentration (NIC). All of the single quantitative parameters were compared between liver abscesses and liver metastases by the independent samples t-test or Mann-Whitney U test. Statistical difference parameters between liver abscesses and liver metastases were analyzed by receiver-operating characteristic (ROC) curves. The diagnostic capability was determined by calculating the area under the curve (AUC). Using binary logistics regression analysis combining the best diagnostic performance parameter in the plain and enhanced phase images. The predictive model of liver abscess was established, and the receiver operating characteristic (ROC) analysis was performed. Results: There were significant differences in CT value, the slope (K), Eff-Z, blood and fat concentrations in the plain phase and NIC in the contrast-enhanced venous and delay phases between liver abscesses and liver metastases (all P < 0.05). The CT value at 40 keV in the plain phase provided 0.761 in area under the curve (AUC) in ROC with sensitivity of 71.4% and, specificity of 75.6% in differentiating liver abscess and tumor. Combining with NIC in delay phase, the respectively values improved to 0.963, and 89.3% and 93.3%. Conclusion: The quantitative parameters in single source dual-energy CT provide high diagnostic accuracy in differentiating liver abscesses from liver metastases.