Saline-enhanced radio-frequency tissue ablation in the treatment of liver metastases

PURPOSE: To assess the effect of intraparenchymal saline injection on the results of radio-frequency (RF) tissue ablation. MATERIALS AND METHODS: Ex vivo and in vivo animal RF ablation was performed with and without intraparenchymal saline injection. Initially, saline was injected as a bolus (1-20 mi) before RF application. For subsequent in vivo studies, saline was injected as a bolus before RF application or continuously (1 mL/min) during RF application. Finally, 14 patients with liver metastases and one patient with primary cholangiocarcinoma were treated with the continuous infusion technique. A single RF electrode (tip exposure, 1-3 cm) was used with various ablation parameters. RESULTS: With pretreatment bolus injection of saline, lesions measured 1.4 cm +/- 0.1, 1.6 cm +/- 0.2, and 1.2 cm +/- 0.1 in ex vivo liver, in vivo animal muscle, and in vivo animal liver, respectively. Without saline enhancement, lesion sizes were 1.0 +/- 0.2, 1.2 +/- 0.3 and 0.8 +/- 0.1 cm, respectively. With continuous saline injection in in vivo pig liver, lesion size was 1.8-4.1 cm in diameter. In human tumors, necrosis volume was variable, but complete necrosis was seen in 13 of 25 lesions (diameter, 1.2-3.9 cm). Partial necrosis greater than 50% was seen in 12 lesions (diameter, 1.5-4.5 cm). CONCLUSION: Saline-enhanced RF ablation might permit percutaneous destruction of large liver lesions.