Ultrasound-guided thermocouple placement for cryosurgery

BACKGROUND. Although cryosurgical methods have high cure rates, imprecise estimates of both skin lesion depth and destructive temperature front location result in subjective technique in skin malignancy treatments. OBJECTIVE. We evaluated the possibility of newer ultrasound equipment to assist in the precise placement of thermocouples in human skin. METHODS. DermaScan C ver. 3 ultrasonographic equipment fitted with a sharp focus probe with a frequency of 20 MHz and a scan length of 12.1 mm was used to locate thermocouples with 27- and 30-gauge needles. RESULTS. We successfully and reproducibly located thermocouples and thin needles, and accurately measured their distance from the skin surface. CONCLUSION. Ultrasound is a useful method for the accurate placement of thermocouples, and needles as thin as 30 gauge for monitoring in cryosurgery.