Information analysis for 3D SPECT imaging of radionuclide distributions in attenuating objects

The existing communication model of SPECT studies is extended by including the attenuating medium in the communication channel. Based on the extended model two fundamental theorems are presented to demonstrate the significance of the mutual information in system design and imaging reconstruction. In addition, the authors present a mutual information formula for SPECT systems to image radionuclide distributions in attenuating objects using single photon emission computed tomography (SPECT) collimators, The formula is, in turn, expressed in terms of the source distribution, attenuation coefficients, and collimator parameters such as collimator thickness, hole size, septal thickness, hole shape factor, and focal length. The polyhedral collimator is employed for the authors´ mutual information analysis in this report. Based on imaging surface decomposition, the analysis of the polyhedral collimator is reduced to the analysis of a single-headed collimator for planar imaging. Conventional collimators including parallel and cone beam collimators are used for the analysis of the single-headed collimator. The information loss due to attenuation is evaluated for myocardial imaging using technetium-99m and thalium-201