Removal of the effect of Compton scattering in 3-D whole body positron emission tomography by Monte Carlo

A Monte Carlo technique has been developed to simulate and correct for the effect of Compton scatter in 3-D acquired PET whole body imaging. The method utilizes the attenuation corrected and normalized, 3-D reconstructed image volume as the source intensity distribution for a photon-tracking Monte Carlo simulation. It is assumed that the number of events in each pixel of the image represents the isotope concentration at that location in the body. The history of each annihilation photon´s interactions in the scattering media is followed. The edges and average attenuation coefficients of the various scattering media are determined using a segmented image volume derived from a short transmission scan. The sinograms for the scattered and unscattered photon pairs are generated in a simulated 3-D PET acquisition. The calculated scatter contribution is used to correct the original data set. The method is general and can be applied to any scanner configuration or geometry. In its current form the simulation requires 20 hours on a Sparc10 when every pixel in a 89-plane, 128×128 pixel, 3-D acquired (CTI 961, two bed positions) image volume is sampled, and roughly 1 hour when 16 pixels (4×4) are grouped as a single pixel. Here, the authors present results of the scatter correction method using a 3-D acquired human study of the thorax as input