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Radio-frequency ablation of hepatic metastases: postprocedural assessment with a US microbubble contrast agent--early
L Solbiati1, S N Goldberg, T Ierace
1Department of Radiology, Ospedale Generale, Busto Arsizio, Italy.
Purpose:
To evaluate contrast agent-enhanced ultrasonography (US) in the detection of untreated tumor after radio-frequency (RF) ablation of hepatic metastases.
Materials And Methods:
Twenty patients with solitary colorectal liver metastases underwent percutaneous RF tumor ablation. Pre- and postablation imaging was performed with nonenhanced and enhanced color and power Doppler US and 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 metastases before ablation. This signal increased after contrast agent administration. Contrast-enhanced US performed 24 hours after ablation demonstrated residual foci of enhancement in three tumors, whereas no US signals were seen in any tumor on nonenhanced scans. CT demonstrated small (< 3-mm) persistent foci of residual enhancement in these three tumors and in three additional lesions that were not seen at US (US sensitivity, 50%; specificity, 100%; diagnostic agreement with CT, 85%). All six patients with evidence of residual tumor underwent repeat RF ablation.
Conclusion:
Contrast-enhanced US may depict residual tumor after RF application and thereby enable additional directed therapy. The potential reduction in treatment sessions and/or ancillary imaging procedures might increase the ease and practicality of percutaneous ablation of focal hepatic metastases.