Estimation of anisotropy coefficient and total attenuation of swine liver at 850 nm based on a goniometric technique: Influence of sample thickness

Estimation of optical properties of biologic tissue is crucial for theoretical modeling of laser treatments in medicine. Tissue highly absorbs and scatters the light between 650 nm and 1300 nm, where the laser provides therapeutic effects. Among other properties, the characteristic of biological tissues to scatter the light traveling trough, is described by the anisotropy coefficient (g). The relationship between g and the distribution of the scattered light at different angles is described by Henyey-Greenstein phase function. The measurement of angular distribution of scattered light is performed by the goniometric technique. This paper describes the estimation of g and attenuation coefficient, μ
_t
, of swine liver at 850 nm, performed by an ad hoc designed goniometric-based system, where a spectrometer measures intensities of scattered light at fixed angles (0°, 30°, 45°, 60, 120°, 135° and 150°). Both one-term and two-term Henyey-Greenstein phase function have been employed to estimate anisotropy coefficient for forward (g
_fs
) and backward scattering (g
_bs
). Measurements are performed on samples of two thicknesses (60 um and 30 urn) to investigate the influence of this factor on g, and repeated 6 times for each thickness. The estimated values of g
_fs
were 0.947 and 0.951 for thickness of 60 μm and 30 μm, respectively; the estimations of g
_fs
were -0.498 and -0.270 for thickness of 60 μm and 30 μm, respectively. Moreover, μ
_t
of liver has been estimated (i.e., 90±20 cm
¹
), through Lambert-Beer equation. The comparison of our results with data reported in literature encourages the use of the ad hoc designed tool for performing experiments on other tissue, and at other wavelengths.