Sensitivity of spatially-resolved diffuse reflectance to high-order optical parameters

A modified delta-P1 approximation is studied in this paper. An analytic solution Rδ-P1(ρ) of this model for reflectance in double source approximation is developed by taking the source series expansion terms to the first order. It is shown that when the source in extended to first order, a better description for high absorption and high scattering media will be developed. The new model can give satisfactory results in describing irradiance distribution close to source compared with the RSDA(ρ) of diffusion approximation. Moreover, Rδ-P1(ρ) provides the prediction of the second-order parameter γ, which is significant for developing the inversion algorithm to recover optical parameters from spatially-resolved diffuse reflectance by using smaller source-detector separations.

δ-P1 approximation model of biological tissues

Qi¹,

Liu²,

Liu³

et al. 2011

Study of SP3 for spatially-resolved diffuse reflectance close to light source

Zhang¹,

Qing-Jun²,

Yang³

2012

Based on P3 approximate spatially-resolved diffuse reflectance theory for semi-infinite biological tissue, the simplified expression SP3 function for highly absorbing medium close to source is studied. The research result shows that function SP3 can better describe the spatially-resolved diffuse reflectance close to source for higher absorption; the inversion of the optical parameters of highly absorbing medium with function SP3 shows the existence of extreme values of the curves fitted with diffuse reflectance data for different start distances, and the inversion results near the extreme values are the most closest to the optical parameters of real tissues.

Sensitivity of Delta-P1 approximation model to second-order parameter

Wang¹,

Wang²

2012

The sensitivity of the second-order parameter of the Henyey-Greenstein phase function based on the spatially-resolved diffuse reflectance within the two-point-source approximation to the Delta-P1 approximation model is studied, and the analytical expression of the sensitivity is derived. The results show that the analytic solution of the Delta-P1 approximation model for reflectance contains the second-order parameter of the scattering phase function compared with the diffusion approximation model, and the second-order parameter has significant influence (the extreme value greater than 30%) on the analytic solution for spatially-resolved diffuse reflectance with small source-detector separations ( 1.5 mm) no matter whether the absorption is weak or strong. The research has theoretical significance for obtaining the optical information abour tissue with the second-order parameter .