Time-Resolved Optical Tomography in Preclinical Studies: Propagation of Excitation and Fluorescence Photons

We present time-resolved methods that rely on near-infrared photons to image the optical properties and distribution of fluorescent probes in small laboratory animals. The scanner assembled in our laboratory is described. The coupled diffusion equations of excitation and fluorescence photons in highly scattering tissues were solved using the three-dimensional Finite Element Method (FEM) provided by Comsol. The computed results allowed to yield photon density maps and the temporal profiles of photons. Simulations were carried-out on two test objects: a resin cylinder and a mouse phantom. The latter required taking into account the straight propagation of photons between the optical fibers and the animal phantom. The results demonstrate the potential applications of the method to pre-clinical imaging.