Metrological evaluation of speed of sound in oils for commercial phantom development

This study presents a metrological evaluation of speed of sound in oil-based materials, aiming to support the development of Tissue Mimicking Materials (TMM) for the performance assessment of diagnostic ultrasonic equipment. While traditional agar-based TMMs are commonly used, their limited durability and stability highlight the need for alternative materials with improved transportability and long-term consistency. In this context, mineral oil, lubricating oil, and ethylene glycol were characterized for their ultrasonic properties. Measurements were carried out using a pulse-echo ultrasonic setup with submerged transducers, under controlled temperature conditions. The speed of sound was determined based on time-of-flight data, and the associated measurement uncertainties were evaluated following the Guide to the Expression of Uncertainty in Measurement (GUM). The measured ultrasonic velocities for each material were as follows: ethylene glycol at (1727.0 ± 4.6) m s-1, mineral oil at (1397.0 ± 5.7) m s-1, and lubricating oil at (1472.0 ± 4.7) m s-1. Among the tested materials, mineral and lubricating oils demonstrated the most suitable acoustic behaviour and are therefore strong candidates for use in the development of stable and transportable oil-based phantoms.