Modeling the Wavelength Dependence of the Early Arriving Fraction of a Short Optical Pulse Transmitted Through a Highly Scattering Medium

The wavelength dependence of light transport parameters of human tissue are estimated using Mie calculations of scattering from a simple model of a distribution of single sized spherical scatterers in an otherwise homogeneous background medium. The results are consistent with a dominant contribution to tissue scattering from small cellular or intercellular constituents such as mitochondria. The early arriving transmitted fraction of short optical pulses is calculated using both a diffusion approximation, and a Monte Carlo solution of the transport problem. Both predict enhancement of this transmission as the incident wavelength is changed from 700 nm to 1300 nm. However, the Monte Carlo solution predicts a much larger enhancement, showing strong disagreement with the diffusion result for early arriving photons at all tissue depths greater than a few millimeters.