Abstract
The main thrust of this study is to evaluate 3D ordered-subsets expectation maximization (OSEM) algorithm in Tc-99m SPECT images for different noise levels. Also this study aims to compare 3D OSEM, with filtered back projection (FBP) with an optimized set of filter parameters, both with and without attenuation correction (AC). The SPECT images of a Jaszczak phantom filled with uniform Tc-99m solution, and capillary line sources with Tc-99m were acquired using a Siemens e-Cam Dual Head Gamma Camera. Three noise levels were achieved by acquiring the SPECT images of the Jaszczak phantom for 30, 20 and 10 seconds per projection angle. As expected, noise increases with increasing number of iterations. There is a significant increase in contrast with increasing number of subsets and iterations. In terms of noise, results have shown that 3D OSEM was significantly better than FBP for low count statistics Without AC, there was no significant difference between FBP and 3D OSEM., The key results of the present study arc that improved spatial resolution was achieved using 3D OSEM. and constant resolution was obtained after 17 and 22 iterations in the centre and periphery of the FOV respectively. Furthermore, applying AC with 3D OSEM results in an improved image contrast in comparison to FBP.