Local tumor recurrence following hepatic cryoablation: Radiologic-histopathologic correlation in a rabbit model

PURPOSE: To use radiologic-histopathologic correlation in an animal model t o distinguish normal postoperative findings from evidence of residual tumor after cryoablation of malignant hepatic tumors. MATERIALS AND METHODS: Hepatic cryoablation was performed in 12 rabbits wit h VX2 tumors and in two healthy rabbits. Nonenhanced and dynamic contrast m aterial-enhanced computed tomography (CT) and magnetic resonance (MR) imagi ng and power and color Doppler flow ultrasonography (US) were performed 7-8 days after cryoablation. Histopathologic findings were correlated with ima ging findings. RESULTS: Twenty tumors of 5-20 mm (mean, 10 mm) and seven areas of normal l iver were treated with cryolesions of 11-21 mm (mean, 15 mm). All cryolesio ns exhibited arterial phase rim enhancement at Ci and MR imaging, and 13 (5 7%) of 23 lesions demonstrated peripheral flow at US because of granulation tissue. There was macroscopic recurrence in 15 (75%) of 20 treated tumors; 14 (93%) appeared as peripheral nodularity with low-grade enhancement. Nec rotic tissue did not enhance. Intact vessels extended up to 6 mm inside cry olesion margins and caused focal internal enhancement and Doppler flow. Are as of high signal intensity on T2-weighted MR images correlated with liquef action necrosis, granulation tissue, and tumor. CONCLUSION: In this animal model, recurrent tumor typically appeared as foc al nodules at the cryolesion periphery. Rim and central foci of enhancement , Doppler flow, and increased signal intensity on TZ-weighted MR images can be normal findings after hepatic cryoablation.