Investigation of accelerated Monte Carlo techniques for PET simulation and 3D 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 use the simulation to analyze scatter effects in PET and explore the potential for use in scatter correction of clinical 3D PET studies. We have reduced the execution time to about 30 minutes or similar to1 million coincidences 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. We use the simulation to analyze how scatter from within the body, outside the FOV, and from scanner shielding as well as the chosen energy threshold affect 3D; PET sinograms.