Expression of optical diffusion coefficient in high-absorption turbid media.

The optical diffusion coefficient in a homogeneous turbid medium with high absorption was determined by steady-state measurements of the light transmission under the infinite-boundary condition. The intensity of the transmission was well described by the solution of the optical diffusion equation. Moreover, the optical diffusion coefficient D was given by a constant, (3 mu'(s))-1, where mu'(s) is the reduced scattering coefficient, up to the absorption coefficient of about 0.3 mu'(s). These results mean that attenuation by absorption only contributes to exponential attenuation along the optical path defined by the scattering coefficient and geometry of the system even in high-absorption turbid media such as the pathological living tissues of bleeding or haematoma.