A radiation force technique for acoustic power calibration of high intensity focused ultrasound transducers.

It is essential to know the acoustic power radiated by transducers used in high intensity focused ultrasound (HIFU) surgery devices for both safety and effectiveness considerations. The power radiated by medical ultrasound transducers usually is measured via radiation force balance (RFB) methods. However, for the high power focused fields encountered in HIFU applications, such measurements can be difficult due to the need for short measurement times to prevent transducer damage, heating of the RFB target, and bubble formation. To address these challenges, a procedure based on pulsed measurements was formulated. High output focused ultrasound transducers were characterized in terms of an effective duty factor, which was then used to calculate the power during the pulse at high drive levels. Two absorbing target designs were used, and both gave reliable results and displayed no damage and minimal temperature rise if placed near the HIFU transducer and away from the focus. The procedure was reproducible up to the maximum power generated of approximately 230 W, representative of the HIFU range, thus allowing the radiated power to be calibrated in terms of the peak‐to‐peak voltage applied to the transducer.