Standards for characterizing highly nonlinear acoustic output from therapeutic ultrasound devices: Current methods and future challenges

Abstract

One of the major challenges of characterizing the acoustic fields and power from diagnostic and high intensity or high pressure therapeutic devices is addressing the impact of amplitude-dependent nonlinear propagation effects. The destructive capabilities of high intensity therapeutic devices (HITU) make acoustic output measurements with conventional fragile sensors used for diagnostic ultrasound difficult. Different approaches involving more robust measurement devices, scaling and simulation are described in two recent IEC documents, IEC TS 62556 for the specification and measurement of HITU fields and IEC 62555 for the measurement of acoustic power from HITU devices. Existing and proposed applications include even higher pressure levels and use of cavitation effects. Promising hybrid approaches involve a combination of measurement and simulation. In order to meet the challenges of design, verification, and measurement, standards and consensus are needed to couple the measurements to the prediction of acoustic output in realistic tissue models as well as associated effects such as acoustic radiation force and temperature elevation.