Differentiating Hepatic Abscess from Malignant Mimickers: Value of Diffusion-Weighted Imaging with an Emphasis on the Periphery of the Lesion

PurposeTo evaluate the efficacy of diffusion-weighted imaging (DWI) in differentiating hepatic abscess from malignant mimickers with an emphasis on periphery of the lesions. Materials and MethodsThirty-nine patients with hepatic abscess and 74 patients with malignant hepatic tumors were included, who underwent gadoxetic acid-enhanced MRI. For qualitative and quantitative analysis, signal intensities and apparent diffusion coefficient (ADC) values of the periphery were assessed. Two observers reviewed DWI and ADC maps rated using a 5-point scale. Diagnostic performance was evaluated using the receiver operating characteristics (ROC) curve analysis. ResultsThe periphery of hepatic abscesses was T1-hypointense, arterial hyperintense, and hypointense on hepatobiliary phase less frequently than that of malignant tumors (P < 0.05). No hepatic abscesses showed peripheral washout on 3-min late phase compared with malignant tumors (59.5%) (P < 0.001). Both groups showed hyperintense rims on DWI, but, 37(94.9%) abscesses revealed rims with high ADC values compared with one (1.4%) malignant tumor (P < 0.001). Mean ADC values of abscesses (1.47 x 10(-3) mm(2)/s 0.36 [standard deviation]) were significantly higher than those of malignancies (0.68 x 10(-3) mm(2)/s +/- 0.20). Diagnostic performance (area under the ROC curve [Az]) of DWI in identifying hepatic abscess was 0.986 and 0.982 for each observer. ConclusionIn addition to conventional MRI, DWI is helpful in differentiating hepatic abscess from malignant mimickers.