Added value of diffusion weighted MRI in evaluation of treatment response: post radiofrequency ablation for hepatocellular carcinoma

Abstract

Objective: To evaluate the feasibility of DWI and the corresponding ADC values to detect local tumor progression (LTP) after radiofrequency ablation for hepatocellular carcinoma. Materials and methods: 139 MR examinations were done for 51 HCC patients post-RFA. Pre and postgadolinium enhanced images as well as DW sequences were performed. ADC values of ablation zones and liver parenchyma were assessed. ADC values of ablation zones and adjacent signal alterations identified in DWI were analyzed. Results: LTP was detected in 12 patients (23.5%) and 16 lesions (21.9%). The mean ADC value of ablated zones differed significantly from that of normal liver parenchyma. No obvious changes were detected in the ADC values of the ablated zones over time. ROIs covering the whole ablation zone showed no significant ADC value difference regarding the presence or absence of LTP. DWI showed 53 hyperintense areas in the periphery of the ablated zones, and the corresponding ADC values were significantly lower in patients with LTP than in patients without LTP. Conclusion: DWI is a feasible follow-up tool for postablation liver contributing in detection of LTP. ADC based evaluation of signal alterations in the periphery of the ablation zone may be helpful in differentiation between LTP and post treatment tissue changes.