SinapTec (France)

Therapeutic ultrasound has been the focus of numerous recent investigations. Recent developments such as histotripsy techniques have led to greater electrical solicitation of ultrasound setup with high intensity and short bursts, which can induce potential risks for patients and operators, as well as suboptimal performances. Neither acoustic nor electrical engineering standards are designed for analyzing such signals. Ultrasound setups are usually characterized by voltage-only and wattmeter power measurements under long duration (> 1 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i>) and low power (< 100 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W</i>) conditions. We propose a method based on combined current–voltage (CCV) measurements performed at high temporal resolution to evaluate performance, stability and consistency under short duration (< 1 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ms</i>) and high power (100 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W</i>) conditions. The average power, envelope variation coefficient and overshoot factor were computed under various input signal conditions with precise automatic windowing of the active part of the pulse. CCV measurements were validated against wattmeter measurements for long duration and high-power signals. The instability of a prototype histotripsy setup was characterized to optimize the hardware. Three other ultrasound setups used for histotripsy, HIFU, and cavitation were evaluated and showed stable behavior. This method can be used to characterize electrical signals across a wide range of ultrasound setups, including setups in which traditional techniques are inapplicable. In addition, this method provides quantitative information about RF signal instability and is simple to implement. Electrical measurements are less time-consuming than acoustic measurements, so they are essential for optimizing reproducibility in laboratory settings under rigorous conditions.