Monte Carlo simulation in SPECT: complete 3D modeling of source, collimator and tomographic data acquisition

A sophisticated SPECT (single-photon-emission computed tomography) simulation package has been developed, permitting full tomographic acquisition of data from physically realistic nonuniform and asymmetric 3-D source objects. The package is based on the Los Alamos code MCNP (Monte Carlo for Neutron-Photon transport), which has been extensively modified by the authors to allow complete collimator and source modeling and direct manipulation of the geometric and physical parameters of the nuclear medicine experiment. A brief description of the synthetic SPECT imaging system and its capabilities is presented. The code MCNP and details of the modifications that have been necessary in order to run MCNP for this application are provided. Preliminary experiments to verify the accurate modeling of the imaging situation are also described. Its ability to model two different collimator geometries (parallel-hole and cone-beam) and steps taken to verify the models are discussed