Acoustic and ultrasonographic characterization of polychloroprene, beeswax, and carbomer-gel to mimic soft-tissue for diagnostic ultrasound.

Materials with acoustic properties similar to soft-tissue are essential as tissue-mimicking materials (TMMs) for diagnostic ultrasound (US). The velocity (c), acoustic impedance (AI) and attenuation coefficient of US (µ) in a material collectively define its acoustic property. In this work, the acoustic properties of polychloroprene rubber, beeswax, and Carbomer-gel are determined. The pulse-echo technique is used to estimate c and µ. The product of a sample density (ρ) and c gives its AI. Using a reference based on the International Commission on Radiation Units and Measurements Report-61, Tissue Substitutes, Phantoms and Computational Modelling in Medical Ultrasound, the results are evaluated. The acceptance criteria are 1.043 ± 0.021 g/cm (ρ), 1561 ± 31.22 m/s (c), 1.63 ± 0.065 MRayls (AI) and µ within 0.5-0.7 dB/cm/MHz. Sample computerized tomography (CT) and US scanning are performed to evaluate their similarities (contrast and speckle pattern) with respective images of the human liver (a clinical soft-tissue). The average errors in measuring c and µ were 0.14% and 1.2% respectively. From the present findings, acoustic properties of polychloroprene and beeswax are unacceptable. However, the results of Carbomer-gel ρ = 1.03 g/cm, c = 1567 m/s, AI = 1.61 MRayls are satisfactory and µ = 0.73 dB/cm/MHz, is higher than the reference (4.3%). Carbomer-gel could produce CT and US images, efficiently mimicking the respective liver images. Carbomer-gel containing 95% water is a low-cost material with a simple formulation. Present results suggest, Carbomer- gel mimics soft-tissue and can be used as a TMM for diagnostic US.