Response of the Skin to Focused Ultrasound

Abstract

Skin of mice has been irradiated with focused ultrasound of one megacycle frequency. Skin in the growing phase of the hair growth cycle becomes ulcerated within two days following treatment while skin in the resting phase of the cycle is relatively unaffected. It is concluded that the response of the skin to ultrasound depends upon the physiological state of the organ at the time of irradiation. Thermal changes which occur during irradiation with ultrasound were measured in resting and growing skin, and no significant difference in absorption of acoustic energy between the systems was found. Since the capacities of the respective systems for absorbing ultrasound are equal this factor can be eliminated as a possible cause for the differential response of the skin. It is also suggested that the differential response of the skin cannot be attributed to structural differences between resting and growing follicles. When skin is irradiated with focused light which produces the same thermal change as that produced by ultrasound, skin in growth is ulcerated and skin at rest is unaffected. The heating component of ultrasound appears to be the physical factor to which the biological response can be attributed.