Hybrid model of light propagation in random media based on the time-dependent radiative transfer and diffusion equations

- Light propagation in homogeneous random media is investigated.
- A crossover length and the time from ballistic regime to diffusive regime of light propagation are evaluated as a function of optical properties.
- An accurate and efficient model based on the time-dependent radiative transfer and diffusion equations for light propagation in the media is proposed by using the crossover length and time.

Numerical modeling of light propagation in random media has been an important issue for biomedical imaging, including diffuse optical tomography (DOT). For high resolution DOT, accurate and fast computation of light propagation in biological tissue is desirable. This paper proposes a space-time hybrid model for numerical modeling based on the radiative transfer and diffusion equations (RTE and DE, respectively) in random media under refractive-index mismatching. In the proposed model, the RTE and DE regions are separated into space and time by using a crossover length and the time from the ballistic regime to the diffusive regime, ρDA~10/μt′ and tDA~20/vμt′ where μt′ and v represent a reduced transport coefficient and light velocity, respectively. The present model succeeds in describing light propagation accurately and reduces computational load by a quarter compared with full computation of the RTE.