Investigation of Accelerated Monte Carlo Techniques for PET Simulation and 3-D 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 eventual use in scatter correction of clinical 3-D PET studies. We have reduced the execution time to about 30 minutes or 1 million coincidences per minute. This allows us rapid feedback for the close examination of the accuracy of the simulation. The simulated sinogram matches the original normalized sinogram to within 5% for a low noise level of 2.5% achieved by summing over many planes. We present techniques used to improve computational efficiency of Monte Carlo simulations and photon transport. We use the method to analyze how scatter from within the body, outside the FOV, and from scanner shielding as well as the chosen energy threshold affect 3-D PET sinograms.