Effect of Transducer Velocity on Intramuscular Temperature During a 1-MHz Ultrasound Treatment

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Abstract

Study Design:

A 3 × 2 repeated-measures design was used. The independent variables were transducer velocity (2-3 cm/s, 4-5 cm/s, and 7-8 cm/s) and time (pretreatment and posttreatment).

Objective:

To determine if transducer velocity of a 1-MHz ultrasound treatment affects intramuscular tissue temperature.

Background:

Most authors advocate ultrasound transducer velocities of 2 to 4 cm/s within an area of 2 to 3 times the effective radiating area or 2 times the size of the transducer head. However, a much faster rate of application (approximately 7-8 cm/s) is often observed in clinical settings.

Methods and Measures:

Eleven healthy screened volunteers (9 males, 2 females; mean ± SD age, 22.6 ± 1.7 years; mean ± SD height, 175.7 ± 13.7 cm; mean ± SD body mass, 82.5 ± 19.5 kg) were randomly assigned to a treatment order with all conditions administered during a single testing session. Each transducer velocity condition was administered for 10 minutes, using 1-MHz ultrasound with a 100% continuous duty cycle at an intensity of 1.5 W/cm2 over an area twice the size of the transducer head. After the first treatment, the 2 remaining subsequent velocity conditions were administered after the intramuscular temperature returned to within ±0.3°C of the initial pretreatment temperature for 5 minutes. The dependent variable was left triceps surae muscle temperature measured at 3 cm below one half the measured skinfold thickness.

Results:

Temperature increase across the 3 velocities was within 0.4°C (F2,20 = 0.07, P = .93). Posttreatment values (mean ± SD) ranged from 42.7°C ± 2.3°C for the slowest velocity to 43.1°C ± 1.4°C for the fastest velocity. Temperature increase was significant for time (F1,10 = 155.68, P<.00001), increasing from 37.8°C ± 0.8°C pretreatment to 42.9°C ± 1.9°C after treatment.

Conclusion:

Very similar intramuscular temperature increases can be observed among ultrasound treatments (10-minute duration, 1-MHz frequency, 100% continuous duty cycle, 1.5 W/cm2 intensity, within an area twice the size of the transducer head), with transducer velocities of 2 to 3, 4 to 5, and 7 to 8 cm/s. J Orthop Sports Phys Ther 2006;36(5):320-325. doi:10.2519/jospt.2006.2157

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