A simplified description of the measured energy-dependent point-source response function for Tc-99m SPECT imaging by multidimensional curve fitting

Experimental measurements of a point source in a uniformly-attenuating cylindrical phantom are being used to model the energy-dependent point-source response function (PSRF) of a SPECT imaging system. These data provide a model PSRF for validating Monte Carlo simulations and testing reconstruction algorithms. Additionally, the data are being used to develop a reconstruction method that utilizes full energy spectral information. The experimental image data have been fitted in two stages to produce a concise description of the system PSRF. The PSRF, as a function of energy and spatial location, is specified by 14 parameters, modeling the image of a point source that would be measured at that location. The PSRF of the SPECT system is being parameterized further by modeling each of the 14 parameters by analytic functions of energy and spatial location. In this way, the energy-dependent PSRF of the SPECT imaging system can be calculated at any spatial location and energy. This paper reports the results of the first stage parameterization, the results of image reconstruction based on the first stage parameterization, and the status of the second stage parameterization of the measured system PSRF.