Model-Based Correction For Scatter And Tailing Effects In Simultaneous Tc-99m And I-123 Imaging For A Cdznte Cardiac Spect Camera

An advantage of semiconductor-based dedicated cardiac single photon emission computed tomography (SPECT) cameras when compared to conventional Anger cameras is superior energy resolution. This provides the potential for improved separation of the photopeaks in dual radionuclide imaging, such as combined use of Tc-99m and I-123. There is, however, the added complexity of tailing effects in the detectors that must be accounted for. In this paper we present a model-based correction algorithm which extracts the useful primary counts of Tc-99m and I-123 from projection data. Equations describing the in-patient scatter and tailing effects in the detectors are iteratively solved for both radionuclides simultaneously using a maximum a posteriori probability algorithm with one-step-late evaluation. Energy window-dependent parameters for the equations describing in-patient scatter are estimated using Monte Carlo simulations. Parameters for the equations describing tailing effects are estimated using virtually scatter-free experimental measurements on a dedicated cardiac SPECT camera with CdZnTe-detectors. When applied to a phantom study with both Tc-99m and I-123, results show that the estimated spatial distribution of events from Tc-99m in the Tc-99m photopeak energy window is very similar to that measured in a single Tc-99m phantom study. The extracted images of primary events display increased cold lesion contrasts for both Tc-99m and I-123.