Heat therapy HIFU transducer electrical impedance modeling by using FEM

Piezoelectric elements are commonly used as ultrasonic transducers. Spherically-concave transducers use in high intensity focused ultrasound for acoustic energy concentration within a body is one of the non-invasive techniques employed in ablation surgery. Transducer acoustic distribution is directly related with piezoelectric element material, geometry and vibration mode. Therefore, its electrical impedance response is an important parameter to consider. The aim of this paper was to model the electrical impedance of a 2 MHz concave transducer by means of finite element method. Impedance was measured from 10 kHz to 4 MHz when the transducer was emitting in air and distilled water. Piezoelectric element material was unknown. Three hard PZT materials PZT-4, PZT-4D and PZT-8 were used during modeling. PZT-8 impedance response showed better concordance with measurements than the other materials.