Modeling the acoustic field of physiotherapy ultrasound transducers using non uniform acoustic pressure distributions

In ultrasonic physiotherapy, the therapeutic effect is produced in the first 5 cm, into the Fresnel zone. Models are focused principally in the Fraunhofer zone which is too far from the therapeutic region. More realistic models are required to express the overlapping commonly produced near the transducer face. This paper presents the modeling of the acoustic field of physiotherapy ultrasonic transducers under non-uniform pressure distributions by using the finite element method. Theoretical approaches are compared with measurements to determine their accuracy. Although the nonuniform vibration models were presented years ago, their validation is still not complete. The results show the efficacy of modeling real transducers under free vibrating, simply supported and clamped conditions in relation to the overlapping in the Fresnel zone. In was concluded that the Fresnel zone is not correctly modeled with any of the approaches of this paper which were proposed in the literature.