A Method of Estimating Pressure and Intensity Distributions of Multielement Phased Array High Intensity Focused Ultrasonic Field at Full Power Using a Needle Hydrophone

The pressure and intensity distribution of high intensity focused ultrasound (HIFU) fields at full power are critical for predicting heating patterns and ensuring safety of the therapy. With the limitations of maximum pressure at the hydrophone and damage from cavitation or thermal effects, it is hard to measure pressure and intensity directly when HIFU is at full power. HIFU‐phased arrays are usually composed of large numbers of small elements and the sound power radiated from some of them at full power is measureable using a hydrophone, we grouped them based on the limitation of maximum permissible pressure at the hydrophone and the characteristics of the element arrangement in the array. Then sound field measurement of the group was carried out at full power level. Using the acoustic coherence principle, the pressure and intensity distribution of the array at full power level can be calculated from corresponding values from the groups. With this method, computer simulations and sound field measurement of a 65‐element concentric distributed phased array was carried out. The simulation results demonstrate theoretically the feasibility of this method. Measurements on the 65‐element phased array also verify the effectiveness of this method for estimating the pressure and intensity distribution of phased array at full power level using a needle hydrophone.