Objective:To compare changes in IM temperature during similar ultrasound treatments with 2 different coupling media. Background: Gel pads are gaining popularity as an ultrasound coupling medium. Intramuscular temperatures during ultrasound with gel pads and standard gel have not been compared.

Methods and Measures: Subjects were 13 student volunteers (21.3 ± 1.4 years of age) without lower-extremity pathology. Ultrasound treatments were administered in a laboratory on 2 separate occasions 48 hours apart, each with a different coupling medium (standard ultrasound gel or gel pad). One-MHz continuous ultrasound was administered for 7 minutes at 1.5 W/cm 2 with the transducer head moving 3 to 4 cm/s over an area approximately twice the size of the transducer head. Tissue temperature was measured every 10 seconds using implantable thermocouples inserted at a 3-cm depth to the surface of the right medial calf. Data were analyzed using an ANCOVA with pretreatment temperature as the covariate.

Results: Tissue temperatures increased during both treatments, with the mean and standard deviation peak temperature during the gel pad treatment reaching 39.4° ± 1.5°C compared to 39.2° ± 2.4°C during the normal gel treatment. Statistical analysis revealed no difference in temperature between ultrasound treatments using gel and those performed using gel pads.

Conclusions: Because temperature changes were similar with both treatments, we conclude that these coupling methods are equivalent under the ultrasound application parameters tested.

J Orthop Sports Phys Ther. 2002; 3(5):216–220.

Key Words: acoustic transmission, coupling medium, thermocouple