Characterization of Acoustical Properties of a Phantom for Soft Tissues (PVCP and Graphite Powder) in the Range 20-45̊C

Stability and duration of ultrasonic (US) Phantoms are still a subject of research. We present a study of acoustic and mechanical properties for polyvinyl chloride plastisol (PVCP) with graphite powder (at 2% in weight) used to construct tissue-like phantoms in the temperature range of 20-45C. PVCP is a new material in the field of US phantoms and has longer duration and stability than the conventional organic mimicking materials. Longitudinal US velocity and attenuation were measured at 1 MHz by the standard transmission method. Shear velocity was obtained by 1-D transient elastography. The extreme values for each of the parameters were obtained at 20 C and 45C. They are: 1501.5±0.7 m/s and 1331.8±0.3 m/s for longitudinal US velocity; 0.46±0.03 dB/cm and 0.94±0.09 dB/cm for attenuation; and 8.4±1.2 m/s and 1.7±0.8 m/s for Shear velocity. Specific heat measured with a calorimeter and thermal conductivity measured by the method of hot plates were, respectively, 2.65±0.51 J/(kgC) and 0.091±0.013J/(s°Cm), both at 22 °C. For 2% of graphite powder, the parameter ranges were compatible to biological tissue ones and therefore, the same phantom can simulate different conditions only by changing its temperature. Other graphite percentages are to be tested to simulate parameter values of pathological conditions like nodules, calcification, fibrosis, etc. The phantom did not suffer from dehydration and is easy to be built in several different geometries.