Performance of the New WCOS Technique for the TITAN SPECT Formulation

Virginia Tech, Nuclear Engineering Program, Department of Mechanical Engineering, 900 N Glebe Rd, Arlington, VA 22203

^* Corresponding Author, E-mail: royston@vt.edu

Abstract

The TITAN code is a parallel hybrid deterministic transport code that includes novel algorithms for simulation of a Single Photon Emission Computed Tomography (SPECT) device. Monte Carlo methods are generally used for SPECT simulation, but can be time consuming and are subject to statistical uncertainties. Representation of the collimator in SPECT is difficult in a deterministic code and a new method is presented to improve the accuracy of the existing hybrid formulation, a combination of SN with fictitious quadrature and ray-tracing. In the new technique, weighted circular ordinate splitting (WCOS), the angular fluxes along the fictitious directions are weighted by the detector surface area projected along each direction to the front of the collimator. For a simple water phantom with a Tc-99m source, the behavior of the WCOS technique for varying parameters is examined for a low energy, general purpose collimator and a low energy, high sensitivity collimator. The TITAN detector flux distribution is benchmarked against the MCNP5 solution and shown to require significantly less computation time. Finally, the parallel computation time of the TITAN SPECT simulation is analyzed.