Effect of scattering and porosity on the apparent absorption in porous biphasic structures—Application to cortical bone

Abstract

In this in-silico study, the attenuation coefficient in porous structures mimicking simplified cortical bone is calculated both in presence and absence of absorption, to isolate the effect of scattering on attenuation. Pore distributions with various pore concentrations (5–25 pore/mm2) and diameters (40–120 μm) are generated. The propagation of 8 MHz plane waves is simulated using a 2D FDTD package. The attenuation coefficient is measured by fitting the exponential decay of the signal amplitude in the frequency domain during propagation in the absence or presence of absorption (coefficient of 10 dB/cm/MHz to mimic bone tissue), for different pore concentrations and sizes. The difference between total attenuation and scattering attenuation coefficients (obtained with no absorption) is defined as the apparent absorption coefficient. For ka 1, increasing porosity leads to a higher apparent absorption, indicating a higher impact of absorption, even though the absorption coefficient and the overall volume fraction of absorbing material (solid phase) were kept constant. This suggests complex interactions between the wave and the structure, and could be attributed to longer propagation paths in the solid phase due to multiple scattering by the pores.In this in-silico study, the attenuation coefficient in porous structures mimicking simplified cortical bone is calculated both in presence and absence of absorption, to isolate the effect of scattering on attenuation. Pore distributions with various pore concentrations (5–25 pore/mm2) and diameters (40–120 μm) are generated. The propagation of 8 MHz plane waves is simulated using a 2D FDTD package. The attenuation coefficient is measured by fitting the exponential decay of the signal amplitude in the frequency domain during propagation in the absence or presence of absorption (coefficient of 10 dB/cm/MHz to mimic bone tissue), for different pore concentrations and sizes. The difference between total attenuation and scattering attenuation coefficients (obtained with no absorption) is defined as the apparent absorption coefficient. For ka 1, increasing porosity leads to a higher appa...