Maximum likelihood reconstruction for fluorescence Optical Projection Tomography

Tomographic reconstruction of fluorescence optical projection tomography (OPT) data is usually performed using the standard filtered back projection (FBP) algorithm. However, there are several physical aspects of fluorescence OPT that pose major challenges for the FBP algorithm. These include blurring, and the fact that for an isotropically emitting point source (or fluorophore), the power received by an objective aperture decreases with the inverse square of the distance to the source. These two effects are shown to result in qualitative and quantitative inaccuracies in fluorescence OPT reconstructions obtained using standard FBP. A model of image formation is developed which includes the effects of isotropic emission and blurring. The model is used to calculate a probabilistic system matrix for use in the maximum likelihood expectation maximisation algorithm, which leads to reconstructions that are both qualitatively superior and quantitatively correct.