Measured acoustic intensities for clinical diagnostic ultrasound transducers and correlation with thermal index.

Abstract

To investigate if the thermal index for bone (TIB) displayed on screen is an adequate predictor for the derated spatial-peak temporal-average (I_SPTA_.3 ) and spatial-peak pulse-average (I_SPPA_.3 ) acoustic intensities in a selection of clinical diagnostic ultrasound machines and transducers. We calibrated five clinical diagnostic ultrasound scanners and 10 transducers, using two-dimensional grayscale, color Doppler and pulsed-wave Doppler, both close to and far from the transducer, with a TIB between 0.1 and 4.0, recording 103 unique measurements. Acoustic measurements were performed in a bespoke three-axis computer-controlled scanning tank, using a 200-μm-diameter calibrated needle hydrophone. There was significant but poor correlation between the acoustic intensities and the on-screen TIB. At a TIB of 0.1, the I_SPTA_.3 range was 0.51-50.49 mW/cm² and the I_SPPA_.3 range was 0.01-207.29 W/cm² . At a TIB of 1.1, the I_SPTA_.3 range was 19.02-309.44 mW/cm² and the I_SPPA_.3 range was 3.87-51.89 W/cm² . TIB is a poor predictor for I_SPTA_.3 and I_SPPA_.3 and for the potential bioeffects of clinical diagnostic ultrasound scanners. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.