Abstract

A Needle-Size Probe with a Side-Acting Hydrophone and a Thermocouple for High Intensity Focused Ultrasound

S.Vaezy (Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, WA, USA); G.Keilman, M.Wyzgala (Sonic Concepts, Inc., Woodinville, WA, USA)

e-mail: vaezy@apl.washington.edu

Thermal and acoustic measurements at high acoustic intensities are desirable in studies involving High Intensity Focused Ultrasound (HIFU). We are developing a needle-size probe comprising of a hydrophone and a thermocouple, that can withstand high intensity fields without damage. The probe can simultaneously map the acoustic pressure and temperature field in a test medium. The hydrophone will be nominally 25 um PVDF or PVDF-TrFE with thin-file electrodes, with a flat frequency response from 1 to 20 MHz, isolated from the metallic needle by an ultrasound-absorbing lossy polymer material. The thermocouple (accurate within 1C) signals will be RF-isolated from the hydrophone signals and electromagnetic interference originating from the HIFU source transducer, allowing rapid temperature rise measurements (250 readings per second) to be made with minimal noise and interference. A conformational coating will protect the hydrophone and the thermocouple from cavitation at high acoustic intensities of 4000 W/cm2. The complete assembly will be integrated into a 13-gauge (0.24 mm Outer Diameter) needle (150 mm long). The results of the manufacturing, characterization, and testing in novel, protein-based tissue-mimicking phantoms will be presented.

Section : 5