Multiple Probe Radiofrequency Ablation: Pilot Study in an Animal Model

PURPOSE: Radiofrequency ablation (RFA) is becoming increasingly popular for the minimally invasive treatment of benign and malignant tumors. Currently available systems are limited to the use of a single probe because of electrical interactions between probes. The purpose of this study was to test a new prototype multiple probe generator with a built-in switching mechanism to determine if multiple zones of necrosis could be formed simultaneously without a significant penalty in terms of lesion size and procedure time. MATERIALS AND METHODS: A dual probe generator was created by modifying a commercially available system into an alternating monopolar system with an external electronic switch controlled by a temperature feedback loop. A total of 20 radiofrequency (RF) lesions (conventional single probe, n = 10; switched dual probe, n = 10) were created in the livers of six adult pigs (temperature, 100°C; 10-minute ablation). Lesions were excised and examined for volume, minimum diameter, and maximum diameter. RESULTS: The time to target temperature was slightly greater for dual (3.5 minutes) versus single ablations (2.7 minutes). However, this resulted in only a 48 second (6.5%) longer total ablation time. There was no significant difference between conventional single and dual lesions for lesion volume (13.6 ± 9.3 cm³ versus 13. 7 ± 7.0 cm³; P > .05), minimum diameter (1.63 ± 0. 56 cm³ versus 1.61 ± 0.53; P > .05) or maximum diameter (3.3 ± 0.84 versus 3.4 ± 0.55, P > .05). CONCLUSION: A multiple probe RFA system that can simultaneously ablate multiple areas in the liver is feasible. If multiple probe units become clinically available, large or irregularly shaped lesions could be treated more effectively than with conventional single probe units, and multiple tumors could be ablated simultaneously, thus potentially decreasing procedure time and anesthetic complications.