Experimental validation of an analytical method of calculating SPECT projection data

The authors have developed a method for analytically calculating photon distributions in SPECT projections. This method models primary photon distributions as well as first and second order Compton scattering and Rayleigh scattering. It uses no free fitting parameters and so the projections produced are completely determined by the characteristics of the SPECT camera system, the energy of the isotope, an estimate of the source distribution and an attenuation map of the scattering object. The method was previously validated by comparison with Monte Carlo simulations and the authors are now verifying its accuracy with respect to phantom experiments. They have performed experiments using a Siemens MS3 SPECT camera system for a /sup 99m/Tc point source (2 mm in diameter) within a homogeneous water bath, a small spherical source (1 cm in diameter) within a homogeneous water cylinder, the small spherical source within a non-homogeneous medium consisting of air and water, and the small spherical source together with. A larger spherical source (2.8 cm. in diameter) in a non-homogeneous air and water medium. The authors' technique reproduces well the distribution of photons in the experimentally acquired projections for all of these cases.