Effects of two ultrasound devices and angles of application on the temperature of tissue phantom

Ultrasound is a commonly used therapeutic modality for which there is little research on the effect of treatment dosage on the extent of tissue heating. The purpose of this study was to investigate the effect of two different ultrasound devices, angle of ultrasound application, and treatment time on the temperature of a tissue phantom. Four trials were performed at four ultrasound application angles (90 degrees, 80 degrees, 70 degrees, and 60 degrees) with both an Excel UltraMax and a Mettler Sonicator 720. A continuous 1-MHz frequency at 2.0 W/cm2 was administered for 5 minutes, with tissue phantom temperature recorded at 1-minute intervals. The analysis of the data revealed significant main effects between ultrasound devices, angle of application, and treatment times. Interactions were identified between ultrasound device and treatment times and angle of application and treatment times. Analysis of simple effects revealed significant differences between ultrasound devices after 2, 3, 4, and 5 minutes of treatment and between treatment times and 80 degrees and 60 degrees angles of application. Maximal temperature increase after a 5-minute treatment was 2.025 degrees C. This level of tissue heating falls below expected values and may not yield therapeutic results. The thermal effects were noted to be greatest at 80 degrees and 90 degrees angles of application. Despite appropriate calibration and identical treatment protocols, the two ultrasound devices yielded significantly different tissue phantom temperatures, which were notably lower than expected values. We concluded that direct monitoring of ultrasound device output and calculation of treatment dosage should occur on a routine basis, as treatment outcome will certainly be affected by the actual dosage of ultrasonic energy.