Small hepatocellular carcinoma treated with percutaneous RF ablation: MR imaging follow-up

OBJECTIVE, The purpose of our study was to determine the usefulness of MR i maging in the follow-up evaluation of small hepatocellular carcinoma lesion s treated with RF ablation. SUBJECTS AND METHODS. The study group included 37 patients with a single he patocellular carcinoma lesion less than 3 cm in diameter. A strict protocol required followup MR imaging every 6 months after RF treatment. At each fo llow-up visit, the findings on unenhanced and dynamic gadolinium-enhanced M R images were correlated with those on contrast-enhanced CT images and with results of fine-needle aspiration biopsy. In five patients who underwent s urgical resection after the 6-month follow-up examination, comparison with histologic findings of surgical specimens was also performed. RESULTS. Correct diagnosis of complete or partial tumor necrosis was made i n 32 (86%) of the 37 patients with the use of unenhanced and dynamic gadoli nium-enhanced MR images. Hypointensity on T2-weighted images and loss of en hancement on dynamic MR images corresponded to completely necrotic lesions in all patients. Conversely, intratumoral regions of hyperintensity on T2-w eighted images and enhancement on dynamic MR images did not always correlat e to residual viable tumor. MR imaging and CT findings agreed in the evalua tion of therapeutic response in all patients. CONCLUSION. Our experience confirms that MR imaging is useful for evaluatin g the effectiveness of RF therapy in achieving tumor regression.