A Monte Carlo correction for Compton scattering effects in 3D PET brain imaging

A Monte Carlo simulation has been developed to simulate and correct for Compton scattering effects in 3D acquired PET brain images. As input the routine requires the 3D reconstructed image volume of interest which is treated as a source intensity distribution for a photon-tracking Monte Carlo simulation. It is assumed that the number of counts in each pixel of the image represents the number of back-to-back 511 keV photon pairs being emitted at that location in the brain. The program then follows the history of each photons´ interactions in the scattering medium and generates the sinograms for the scattered and unscattered photon pairs detected in a simulated 3D PET acquisition. The calculated scatter contribution is then subtracted from the original data set. The calculation is general and can be applied to any scanner configuration or geometry. In its current form the simulation requires 25 hours on a single Sparc10 CPU when every pixel in a 15-plane, 128×128 pixel image volume is studied, and less than 2 hours when sampled over regions of 4×4 pixels. Results of the correction applied to 3D human and phantom studies are presented