MR imaging of hepatocellular carcinoma following microwave coagulation therapy

MRI was performed in 13 patients who had microwave coagulation therapy (MCT) for hepatocellular carcinoma. Six of them underwent surgery after MRI. The area (including tumor) treated by MCT showed low to high intensity on T1WI, and low to isointensity on T2WI. No enhancement was obtained on dynamic MRI. Histologically, this area was supposed to be coagulation necrosis. On T1WI, only tumor showed high intensity within the MCT area in 8 patients, and nearly uniform intensity was observed in 5 patients. Histologically, residual cell nuclei were observed in the former, and nearly uniform coagulation necrosis in the latter. The marginal part of the MCT area exhibited low intensity on T1WI, and high intensity on T2WI. Strong enhancement was obtained on dynamic MRI, and histologically, granulation tissue was noted. In the hepatic parenchyma around the MCT area, a ring-or wedge-shaped high intensity part was observed in 7 patients on T2WI, and that part was enhanced on dynamic MRI. This finding was considered to reflect changes such as hepatic hyperperfusion. In terms of the capability of visualizing residual tumor after MCT, MRI was superior to CT. Furthermore, a clear distinction was seen between the MCT area and non-MCT area on T2WI and dynamic MRI. Thus, MRI was useful in the determination of additional therapy.