Optical and acoustic properties at 1064 nm of polyvinyl chloride-plastisol for use as a tissue phantom in biomedical optoacoustics

A novel optoacoustic phantom made of polyvinyl chloride-plastisol (PVCP) for optoacoustic studies is described. The optical and acoustic properties of PVCP were measured. Titanium dioxide (TiO₂) powder and black plastic colour (BPC) were used to introduce scattering and absorption, respectively, in the phantoms. The optical absorption coefficient (μ_a) at 1064 nm was determined using an optoacoustic method, while diffuse reflectance measurements were used to obtain the optical reduced scattering coefficient (μ'_s). These optical properties were calculated to be μ_a = (12.818 ± 0.001)A_BPC cm⁻¹ and μ'_s = (2.6 ± 0.2)S_TiO2 + (1.4 ± 0.1) cm^-1, where A_BPC is the BPC per cent volume concentration, and S_TiO2 is the TiO₂ volume concentration (mg mL⁻¹). The speed of sound in PVCP was measured to be (1.40 ± 0.02) × 10³ m s⁻¹ using the pulse echo transmit receive method, with an acoustic attenuation of (0.56 ± 1.01) f^(1.51±0.06)_MHz (dB cm⁻¹) in the frequency range of 0.61–1.25 MHz, and a density, calculated by measuring the displacement of water, of 1.00 ± 0.04 g cm⁻³. The speed of sound and density of PVCP are similar to tissue, and together with the user-adjustable optical properties, make this material well suited for developing tissue-equivalent phantoms for biomedical optoacoustics.