A goniometric apparatus is presented for measuring the angular dependence of scattering of a HeNe laser beam by in vitro human dermis samples of various thicknesses, hydrated to an 85 percent water content. Measurements of the transmitted and reflected light as a function of angle are presented for tissue thicknesses of 20-650 μm. Extrapolation of these angular scattering patterns to the limit of an incremental tissue thickness specifies the scattering phase function appropriate for use in the radiative transport equation. The scattering phase function is composed of a forward-directed scattering component (90 percent contribution) characterized as a Henyey-Greenstein function with g(HG) equal 0.91, and an additional isotropic component (10 percent contribution, b = 0.10). The net value for the average cosine of the scattering phase function, g equal (1 - b)g(HG), is 0.82, which corresponds to an average deflection angle of 35° for for a scattering event. The on-axis attenuation of the collimated HeNe laser beam indicates a total attenuation constant of 190 cm-1, composed of an absorption coefficient of 2.7 cm-1 and a scattering coefficient of 187 cm-1.
|Original language||English (US)|
|Number of pages||25|
|Journal||Lasers in the Life Sciences|
|State||Published - Jan 1 1988|
ASJC Scopus subject areas
- Medicine (miscellaneous)