Primary and secondary lung malignancies treated with percutaneous radiofrequency ablation: Evaluation with follow-up helical CT

OBJECTIVE. We sought to describe the appearance of primary and secondary lung malignancies treated with radiofrequency ablation on follow-up helical CT and to identify the important CT findings for evaluating therapeutic efficacy and response on follow-up CT. MATERIALS AND METHODS. Among the 21 patients in our study population, 17 had lung cancer and four had metastatic nodules. All patients underwent follow-up helical CT immediately after undergoing percutancous radiofrequency ablation, 1 month later, and then every 3 months. Two reviewers interpreted the CT findings and reached a consensus opinion. Patients were divided into two groups on the basis of the posttreatment contrast-enhanced CT findings-those with a complete ablation and those with a partial ablation. The serial changes in the enhancement pattern, size, peripheral ground-glass opacities, and other findings in the treated area in the two groups were assessed on follow-up CT. RESULTS. In the complete ablation group (n = 9 patients), the ablated lesions were completely without contrast enhancement on follow-up CT, and the mean percentage of decrease in the size of the ablated lesions at 3, 6, 9, 12, and 15 months was 5.7%, 11.4%, 14.3%, 40%, and 40%, respectively, compared with the lesion size on the follow-up CT scans obtained immediately after treatment. In the partial ablation group (n = 12 patients), the ablated lesions had various degrees of enhancement, and the mean percentage of ablated lesion size gradually increased after the 6-month follow-up CT examination. Enveloped ground-glass opacity surrounding tumor was seen in five (23.8%) of 21 lesions on the immediate follow-up CT scans. CONCLUSION. Of the CT findings of lung malignancy after radiofrequency ablation therapy, the enhancement pattern and the size of the change in the ablated lesion are the most important factors for deten-nining whether a complete ablation has been achieved.