Photon diffusion equation

Photon diffusion equation is a second order partial differential equation describing the time behavior of photon fluence rate distribution in a low-absorption high-scattering medium.
Its mathematical form is as follows.
where formula_2 is photon fluence rate (W/cm2), formula_3 is Del operator, formula_4 is absorption coefficient (cm−1), formula_5 is diffusion constant, formula_6 is the speed of light in the medium (m/s), and formula_7 is an isotropic source term (W/cm3).
Its main difference with diffusion equation in physics is that photon diffusion equation has an absorption term in it.
Application.
Medical Imaging.
diffuse optical tomography