Object shape dependent scatter simulations for PET

The correctness of an analytical simulation for single-scattered gamma rays in positron volume imaging was verified by comparing it to Monte Carlo simulation of single scattering. The Monte Carlo simulation was verified using measured tomograph data. The single-scatter analytical simulation was extended to estimate multiple scattering. The multiple-scatter analytical simulation showed good agreement with the Monte Carlo simulation of total object scatter. It is shown using the analytical simulation that the position of a source along the line of response and the shape of the scattering object make a substantial difference in the scatter distribution in the projections. Such projections can be generated in a much shorter time using the analytical simulation than using the Monte Carlo simulation. A scatter correction method which uses the analytical simulation and exploits the inherent smoothness of the scatter distribution to account for three-dimensional effects in scatter distribution and object shape is also proposed