Investigation of accelerated Monte Carlo techniques for PET simulation and3D PET scatter correction

We have been developing Monte Carlo Techniques for calculating primary and scatter photon distributions in PET. Our first goal has been to accelerate the Monte Carlo Code for fast PET simulation. Our second goal has been to u se the simulation to analyze scatter effects in PET and explore the potenti al for use in scatter correction of clinical 3D PET studies. We have reduce d the execution time to about 30 minutes or similar to1 million coincidence s per minute on a dual 300MHz processor UltraSparcII workstation. The short execution time makes it feasible to use this technique for 3D PET scatter correction in the clinic. Fast simulation also allows us rapid feedback for the close examination of the accuracy of the method. We present techniques used to improve computational efficiency of Monte Carlo PET simulations. W e use the simulation to analyze how scatter from within the body, outside t he FOV, and from scanner shielding as well as the chosen energy threshold a ffect 3D; PET sinograms.