In tissue optics it is customary to distinguish between thin and thick media. For thin media the decay is governed by ballistic transport, however for thick media the dynamics is heavily diffusive and therefore usually analyzed with the diffusion approximations. The specific route from ballistic to diffusive transport carries important information on the relationship between ballistic and diffusive light transmitted through the media.

A model which describes the quantitative relationship between ballistic and diffusive light is presented and examined. An important conclusion of this model is that the ballistic regime can be extended by reducing the solid angle of the measurement device, and therefore by planning the system correctly, it should be possible to extract the ballistic image of a tissue with a thickness of approximately 1cm or even more.