Effects of transducer mass on intramuscular temperature during ultrasound treatments.

CONTEXT A potential variable that could affect rate of temperature elevation with ultrasound is the pressure (mass) that is applied to the transducer head during application. Added pressure could compress the tissue, affecting density and the transmission of ultrasound energy. Little research has been completed to determine the effects of the amount of pressure applied during therapeutic ultrasound in vivo. OBJECTIVE To determine the effects of different applied transducer mass on intramuscular temperature during an ultrasound treatment within the left triceps surae. DESIGN Crossover clinical trial. SETTING Human performance research laboratory. PARTICIPANTS Convenience sample of thirteen healthy, college-age students. INTERVENTIONS Three separate 3-MHz, 1.0-W/cm2 ultrasound treatments were administered 1.5 cm within the triceps surae. The independent variables were the linear temperature standards (0.5°C, 1.0°C, 1.5°C, and 2.0°C above baseline) and the 3 different applied pressures measured in grams (200 g, 600 g, and 800 g). MAIN OUTCOME MEASURES A thermocouple probe was used to measure triceps surae temperature, and time to reach the temperature standards was recorded during the ultrasound treatments. A 4 × 3 repeated-measures analysis of variance (RM-ANOVA) was used to analyze the differences for temperature points (0.5°C, 1.0°C, 1.5°C, and 2.0°C) and transducer mass (200 g, 600 g, and 800 g) and with respect to time. RESULTS The results of the RM-ANOVA showed no temperature-point and transducer-mass interaction (F6,72 = 1.69, P = .137) or main effect for mass (F2,24 = 1.23, P = .309). The time required to raise temperature 2°C was 209.1 ± 68.10 s at 200 g, 181.5 ± 61.50 s at 600 g, and 194.9 ± 75.54 s at 800 g. CONCLUSIONS Under the conditions of this study, the amount of mass applied with the transducer during an ultrasound treatment does not ultimately affect the rate of tissue heating.