Ultrasound therapy units in Manitoba and Northwestern Ontario: performance evaluation.

Twenty-six ultrasound therapy devices in clinical use in Manitoba and Northwestern Ontario were tested for performance compliance with Canadian government standards of functioning. The performance characteristics measured were the temporal average acoustic power output, the electrical impulse frequency to the transducer, and the timer accuracy. Twenty-one of the 26 units (81%) had power levels which differed by more than +/- 20% of the indicated output, and only five units (19%) had all tested power levels within +/- 20% of the indicated output. Seven units (27%) had inaccurate timers, but only one unit (of the 13 tested) had an unacceptable frequency reading. This study supports the results of other investigations which have suggested that the majority of ultrasound therapy units in clinical use are in need of calibration. This situation needs to be corrected immediately if patients are to receive the prescribed doses of ultrasound radiation for treatment purposes both safely and effectively. Possible courses of action for rectifying these problems are discussed.