Characterization of the acoustic output of therapeutic ultrasound equipment

The safety and efficacy of ultrasound therapy may be compromised if the output from therapy transducers differs considerably from the indicated value. Although the total power output of a transducer can be easily measured using a pressure balance, it is also important to know how this energy is distributed through space. By using a hydrophone scanning technique, beam profiles of the energy distribution can be obtained. From the beam profiles various parameters such as the effective radiating area (ERA) and the beam non-uniformity ratio (BNR) can be determined. Since the spatial-average intensity selected for treatment is a ratio of the emitted ultrasound power and the effective radiating area, it is essential to be able to measure parameters like the effective radiating area. In this study ERA and BNR measurements for commercially available devices were performed with a hydrophone scanning technique.