Acoustic properties of butadiene and silicone elastomers at megahertz frequencies

AbstractA tissue mimic material with a sound velocity of 1540 m s–1 and an acoustic attenuation of 0·5 dB MHz–1 cm–1 is required for calibrating medical Doppler ultrasound transducers. These properties can be obtained with a solid material comprised of a gel containing a high water content. If solid elastomers are to be used to provide a more stable tissue mimic, modelling suggests that the materials would require low viscoelastic damping, with a low glass transition temperature, Tg. Castable polyurethanes have been made using a polybutadiene soft segment and by adding process oil, the acoustic loss has been reduced to 0·9 dB MHz–1 cm–1 with a sound velocity of 1459 m s–1. Unfilled butadiene rubber (with a high-cis microstructure) had an acoustic loss around 1 dB MHz–1 cm–1, the low loss being associated with its low Tg, with a sound velocity of 1567 m s–1. Silicone elastomers made from unfilled poly dimethyl siloxane had an acoustic loss of 0·71 dB MHz–1 cm–1, but the sound velocity was too low at 1033 m...