Validity of Independent Scattering Approximation (ISA) to measure ultrasonic attenuation in porous structures with mono-disperse random pore distribution

Abstract

The goal of this study is to assess the validity of the Independent Scattering Approximation (ISA) for predicting ultrasonic attenuation in structures mimicking simplified geometries of cortical bone. Finite Difference Time Domain (FDTD) methods were used to assess the ultrasound attenuation in porous media with a monodisperse distribution of pores, with pore diameters, density, and frequency in the range of ϕ = 40–120μm, 3–16 pore/mm2, and 1–8 MHz, respectively. The attenuation values obtained from the FDTD simulations were compared to attenuation values predicted by the ISA. The results indicate that the ISA reliably predicts the attenuation for kϕ The results revealed that MS is dominant at ϕ = 120, but that SS is dominant for ϕ = 60 μm. Assuming that the attenuation is a function of kϕ, the ISA is modified to test its applicability where single scattering is dominant. The results using the modified ISA showed that it can predict the attenuation in monodisperse porous structures for kϕ < 1 and ϕ∈[40–100] μm with less than 10% error. The goal of this study is to assess the validity of the Independent Scattering Approximation (ISA) for predicting ultrasonic attenuation in structures mimicking simplified geometries of cortical bone. Finite Difference Time Domain (FDTD) methods were used to assess the ultrasound attenuation in porous media with a monodisperse distribution of pores, with pore diameters, density, and frequency in the range of ϕ = 40–120μm, 3–16 pore/mm2, and 1–8 MHz, respectively. The attenuation values obtained from the FDTD simulations were compared to attenuation values predicted by the ISA. The results indicate that the ISA reliably predicts the attenuation for kϕ<1 and ϕ∈[100,120] μm, with less than 15% error. The error increases up to 26% as ϕ decreases. The reason that ISA fails to predict accurate values for lower ϕ is investigated through the quantification of multiple scattering (MS). This is done by MS assessment in which the effect of multiple versus single scattering (SS) is compared by measuring the backscatt...