Speed of sound in rubber-based materials for ultrasonic phantoms.

PURPOSE: In this work we provide measurements of speed of sound ( SoS ) and acoustic impedance ( Z ) of some doped/non-doped rubber-based materials dedicated to the development of ultrasound phantoms. These data are expected to be useful for speeding-up the preparation of multi-organ phantoms which show similar echogenicity to real tissues.

METHODS: Different silicones (Ecoflex, Dragon-Skin Medium) and polyurethane rubbers with different liquid (glycerol, commercial detergent, N -propanol) and solid (aluminum oxide, graphene, steel, silicon powder) inclusions were prepared. SoS of materials under investigation was measured in an experimental setup and Z was obtained by multiplying the density and the SoS of each material. Finally, an anatomically realistic liver phantom has been fabricated selecting some of the tested materials.

RESULTS: SoS and Z evaluation for different rubber materials and formulations are reported. The presence of liquid additives appears to increase the SoS , while solid inclusions generally reduce the SoS . The ultrasound images of realized custom fabricated heterogeneous liver phantom and a real liver show remarkable similarities.

CONCLUSIONS: The development of new materials' formulations and the knowledge of acoustic properties, such as speed of sound and acoustic impedance, could improve and speed-up the development of phantoms for simulations of ultrasound medical procedures.