Physically realistic Monte Carlo simulation of source, collimator and tomographic data acquisition for emission computed tomography

A sophisticated simulation package has been developed permitting full tomographic acquisition of nuclear medicine data from physically realistic, non-uniform and asymmetric source and scattering objects. The simulation package is based on MCNP (Monte Carlo for neutron-photon transport), a Monte Carlo code developed at the Los Alamos Scientific Laboratory. The MCNP code has been extensively modified with features that allow direct manipulation of the geometric and physical parameters of the simulation experiment. Collimators of various types have been modelled realistically; collimator properties such as hole dimensions, number of holes and packing geometry can be defined. Other parameters such as energy windows and the number of tomographic views can be set, as can spatial and energy resolution. Any 3D photon source and scattering object can be specified with any degree of detail, allowing for extremely realistic patient models. A post-processing algorithm allows the display and analysis of the simulated images as they are being generated. Using three-dimensional, realistic patient or phantom geometries, this simulation package represents a valuable tool for examining many of the physical aspects of the SPECT imaging situation.