Ultrasound hyperthermia applicators: intensity distributions and quality assurance

Intensity plots at several depths in water were obtained with three ultrasound hyperthermia applicators (Clinitherm, Mark VII), each with a single plane circular ceramic transducer element. One of the applicators exhibited an anomalous localized intensity maximum 3 cm away from the central beam axis. This observation, and the fact that transducer efficiency and field patterns may change with time and use, suggest quality assurance enhancement through periodic checks of output distributions of ultrasonic applicators for clinical use.