Radio-frequency ablation of hepatic metastases: Postprocedural assessment with a US microbubble contrast agent - Early experience

PURPOSE: To evaluate contrast agent-enhanced ultrasonography (US) in the de tection of untreated tumor after radio-frequency (RF)ablation of hepatic me tastases. MATERIALS AND METHODS: Twenty patients with solitary colorectal liver metas tases underwent percutaneous RF tumor ablation. Pre- and postablation imagi ng was performed with nonenhanced and enhanced color and power Doppler US a nd contrast-enhanced helical computed tomography (CT). Initial follow-up CT and US contrast-enhanced helical computed tomography (CT). Initial follow- up CT and US were performed 24 hours after ablation. The findings at US and CT were compared. RESULTS: Nonenhanced US demonstrated intratumoral signal in 15 of 20 metast ases before ablation. This signal increased after contrast agent administra tion. Contrast-enhanced US performed 24 hours after ablation demonstrated r esidual foci of enhancement in three tumors, whereas no US signals were see n in any tumor on nonenhanced scans. CT demonstrated small (<3-mm) persiste nt foci of residual enhancement in these three tumors and in three addition al lesions that were not seen at US (US sensitivity, 50%; specificity, 100% ; diagnostic agreement with CT, 85%). All six patients with evidence of res idual tumor underwent;repeat RF ablation. CONCLUSION: Contrast-enhanced US may depict residual tumor after RF applica tion and thereby enable additional directed therapy. The potential reductio n in treatment sessions and/or ancillary imaging procedures might increase the ease and practicality of percutaneous ablation;of focal hepatic metasta ses.