Percutaneous ablation therapy of hepatocellular carcinoma with irreversible electroporation: MRI findings

Objective: Irreversible electroporation is a new ablation modality. Our purpose was to describe the MRI findings after irreversible electroporation treatment of hepatocellular carcinoma (HCC).

Subjects and methods: In an 18-month period, we treated 24 HCC lesions in 20 patients who were not candidates for surgery. MRI was performed before and 1 month after irreversible electroporation. We used the liver-specific contrast medium gadoxetic acid. We evaluated the size, shape, signal intensity (T1-weighted, T2-weighted, and diffusion-weighted imaging), dynamic contrast enhancement pattern, and signal behavior during the liver-specific phase. Changes in the perilesional parenchyma, perfusion abnormalities, and complications were also recorded.

Results: According to the modified Response Evaluation Criteria in Solid Tumors system, 22 of 24 lesions had a complete response, and two lesions showed a partial response and were retreated. The lesions showed a mean size increase of 10%, with a round or oval shape. On the T1-weighted images, we observed a hyperintense core and a hypointense rim. On the T2-weighted sequences, the signal was heterogeneously hypointense. On diffusion-weighted images, 83% of lesions showed restricted diffusion, with b values of 0-800 s/mm(2), whereas in 17% of the lesions, the signal was not clearly discernible for different b values. The apparent diffusion coefficient values did not show statistically significant differences between the baseline (800-1020 × 10(-3) mm(2)/s) and the reassessment after 1 month (900-1100 × 10(-3) mm(2)/s). The necrotic area did not show a signal increase after contrast material injection. Perfusion abnormalities, such as areas of transient hepatic intensity difference, were present in the tissue adjacent to six treated lesions. In two patients, a reduced or absent concentration of the contrast medium was observed during the liver-specific phase around the ablation zone. One patient had an arteriovenous shunt and another had biliary duct dilatation.

Conclusion: MRI detects characteristic morphologic and functional changes after irreversible electroporation treatment.