Tissue ablation with radiofrequency using multiprobe arrays.

RATIONALE AND OBJECTIVES: We studied the feasibility of increasing the volume of tissue destroyed by radiofrequency tissue coagulation using multiprobe arrays and defined parameters that determine lesion size and shape. METHODS: Radiofrequency was applied to ex vivo calf liver using arrays of two to five 18-gauge probes for 6 min at 70-90 degrees C. Probe spacing (1-3 cm) and arrangement, as well as the method of radiofrequency application (simultaneous or sequential), were varied. The resulting areas of tissue coagulation were measured and compared. RESULTS: Uniform tissue necrosis was observed with simultaneous radiofrequency application for probes 1.5 cm or less apart. At 1.5 cm, arrays of three equidistant probes produced spheroid lesions approximately 3.0 +/- 0.2 cm in diameter. Arrays of four equidistant probes produced cuboid lesions of 3.2 +/- 0.1 cm per side. However, probes placed 2 cm or more apart produced independent lesions 1.4 cm in diameter, with incomplete necrosis between probes. In the trials using five-probe arrays, a central region 4mm in diameter showed no visible evidence of tissue necrosis. With each array, lesion size varied less than 3 mm in any direction. Greater necrosis was accomplished when radiofrequency was applied simultaneously rather than sequentially. CONCLUSION: Multiprobe radiofrequency arrays permit the destruction of more tissue in a single treatment session than is possible with multiple individual probes operating alone. Probes spaced 1.5 cm or less apart act synergistically, producing a total volume of coagulated tissue that is greater than when the individual probes are operated sequentially.