Measurement of the field characteristics from High Intensity Focused Ultrasound transducer

The measurement of the field characteristics from a High Intensity Focused Ultrasound (HIFU) transducer is indispensable to optimize tissue ablation and minimize collateral damage. The objective of this research was to develop a system and method to measure the field characteristics from the HIFU source. The implementation of this work utilizes a planar scanning technique. A needle hydrophone was used as a measurement tool to scan the entire ultrasound beam on both X and Y axis at the focal plane of the HIFU transducer at two different frequencies (1.52 MHz and 5 MHz). The voltage signal representing the acoustic pressure-time waveform was then measured as a function of the hydrophone position in the ultrasound field. The pressure distributions of the HIFU source such as contour plots, corresponding color plots and three- dimensional reconstruction plots were obtained. The relationships between the pressure amplitudes generated from the HIFU transducer and the excitation voltages driving the HIFU source are presented to verify the HIFU field extrapolation assumption. The results show that the system and method to measure the field characteristics from HIFU transducer were successfully developed using planar scanning technique. In addition, the results indicate that the acoustic output is not proportional to the excitation voltage driving the HIFU source.