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

Objective-To examine the tissue-temperature changes that occur at various d epths during 3.3-MHz ultrasound (US) treatments of the caudal thigh muscles in dogs. Study Design-A prospective, randomized, experimental study. Animals-Ten mixed-breed research dogs. Methods-Two US treatments, one at an intensity of 1.0 W/cm(2) and one at 1. 5 W/cm(2), were administered to the caudal thigh region of 10 adult male an d 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-cm(2) area for 10 minu tes using a sound head with an effective radiating area of 5 cm(2). Treatme nts were administered in random order. Tissue temperature was measured befo re, during, and after US treatment until tissue temperature returned to bas eline. Results-At the completion of the 10-minute US treatment, the temperature ri se at an intensity of 1.0 W/cm(2) was 3.0 degreesC at the 1.0-cm depth, 2.3 degreesC at 2.0-cm depth, and 1.6 degreesC at 3.0-cm depth. At an intensit y of 1.5 W/cm(2), temperatures rose 4.6 degreesC at the 1.0-cm depth, 3.6 d egreesC at 2.0-cm depth, and 2.4 degreesC at 3.0-cm depth. Tissue temperatu res returned to baseline within 10 minutes or sooner after treatment in all dogs. Conclusions-This study demonstrates that significant heating occurs in the superficial thigh muscle of dogs during 3.3-MHz US. Clinical Relevance-3.3-MHz US can be used to increase superficial tissue te mperature in dogs, although the amount of time that tissue temperature rema ins elevated is relatively short. (C) Copyright 2001 by The American Colleg e of Veterinary Surgeons.