Effects of 3.3-MHz ultrasound on caudal thigh muscle temperature in dogs.

Abstract

To examine the tissue-temperature changes that occur at various depths during 3.3-MHz ultrasound (US) treatments of the caudal thigh muscles in dogs. A prospective, randomized, experimental study. Ten mixed-breed research dogs. Two US treatments, one at an intensity of 1.0 W/cm(2) and one at 1.5 W/cm2, were administered to the caudal thigh region of 10 adult male and female hound-type dogs weighing 20.5 to 25.0 kg. Needle thermistors were inserted in the caudal thigh muscles below the skin surface at depths of 1.0, 2.0, and 3.0 cm, directly under the US treatment area. Both intensities of US treatment were performed on each dog over a 10-cm2 area for 10 minutes using a sound head with an effective radiating area of 5 cm2. Treatments were administered in random order. Tissue temperature was measured before, during, and after US treatment until tissue temperature returned to baseline. At the completion of the 10-minute US treatment, the temperature rise at an intensity of 1.0 W/cm2 was 3.0 degrees C at the 1.0-cm depth, 2.3 degrees C at 2.0-cm depth, and 1.6 degrees C at 3.0-cm depth. At an intensity of 1.5 W/cm2, temperatures rose 4.6 degrees C at the 1.0-cm depth, 3.6 degrees C at 2.0-cm depth, and 2.4 degrees C at 3.0-cm depth. Tissue temperatures returned to baseline within 10 minutes or sooner after treatment in all dogs. This study demonstrates that significant heating occurs in the superficial thigh muscle of dogs during 3.3-MHz US. 3.3-MHz US can be used to increase superficial tissue temperature in dogs, although the amount of time that tissue temperature remains elevated is relatively short.