Intraoperative ultrasound is used to facilitate location of the tumors and assist in guiding the RFA probe into the tumor core. A RFA probe is introduced into the lesion and an array of electrodes is deployed into the tumor. After deployment, power of 50 watts is applied and increased in 10 watt increments every 60 seconds to a maximum of 90 watts. This is continued until "roll off" occurs. This indicates a drop in power output as tissue impedance increases secondary to coagulation necrosis. After a 30 second pause, the power is reapplied at 75% of the total for "roll off" and advanced as before. The probe is reapplied to encompass the entire tumor. Each cycle should ablate a sphere of 3-5 cm in diameter depending on the size of the probe used.

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