Thresholds for Focal Ultrasonic Lesions in Rabbit Kidney, Liver, and Testicle

Thresholds are reported for production of focal ultrasonic lesions in rabbit liver, kidney, and testicle for 2 and 6 MHz, singe pulse exposures ranging in length from 1 to 60 s. Intensity-exposure time thresholds are found to be nearly independent of frequency as shown in earlier work for brain tissue. The results compare favorably with a thermal model for prediction of thresholds which considers the activation energy for thermal destruction of the tissues, their thermal diffusivity, absorption coefficients, time and intensity of exposure, and baseline temperature. All thresholds are of the same magnitude as those previously reported for brain. Those differences which are observed can be explained by the thermal model for the action of ultrasound on tissue.