The Dynatron Solaris® Ultrasound Machine: Slower Heating Than Textbook Recommendations at 3 MHz, 1.0 W/cm2.

ABSTRACT

CONTEXT Therapeutic ultrasound clinical parameters are provided in many modality textbooks based on research performed with the Omnisound brand. Literature exists to support variability in heating rates with different manufacturers. It is unknown if the Dynatron Solaris heats at rates consistent with textbook recommendations. OBJECTIVE: Determine the rate of tissue-temperature increases in the medial triceps surae with the Dynatron Solaris® 708 ultrasound unit. DESIGN: 3 × 13 repeated measures. Independent variables were tissue depth (1.0, 1.75, and 2.5 cm) and time (13 time periods throughout the treatment). SETTING: Research laboratory. PARTICIPANTS: 30 healthy volunteers (female = 11, male = 19; age 21.30 ± 1.95 y; adipose thickness = 0.54 ± 0.15 cm). INTERVENTION  Three thermocouples were inserted into the medial triceps surae at 1.0, 1.75, and 2.5-cm depths. A continuous 3-MHz, 1.0-W/cm2 for 20 minutes ultrasound treatment was performed with a Dynatron Solaris 708 machine. MAIN OUTCOME MEASURES: Intramuscular tissue-temperature increases at each depth throughout the 20-min treatment. RESULTS: There was a significant main effect of depth (F2,52 = 29.76, P < 0.001) and time (F12,312 = 181.59, P < .001) and a significant interaction between times and depths (F24,624 = 15.49, P < .001). The 1.0-cm depth increased 4.22 ± 1.58°C in 6 min (0.70°C/min rate), the 1.75-cm depth increased 3.93 ± 1.94°C in 10 min (0.39°C/min rate), and the 2.5-cm depth increased 3.60 ± 1.86°C in 20 min (0.18°C/min rate). CONCLUSIONS: The rate of tissue-temperature increase varied at each depth and the 1.0-cm depth was the only rate similar to textbooks. Clinicians will not reach tissue-temperature goals using Omnisound textbook parameters on the Dynatron Solaris 708 at depths greater than 1.0 cm, which may affect clinicians, educators, and state-certification exams.