Experimental validation of an analytical method of calculating photon distributions

We 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 we are now verifying its accuracy with respect to phantom experiments. We have performed experiments using a Siemens MS3 SPECT camera system for a point source (2 mm in diameter) within a homogeneous water bath and a small spherical source (1 cm in diameter) within both a homogeneous water cylinder and a non-homogeneous medium consisting of air and water. Our technique reproduces well the distribution of photons in the experimentally acquired projections.