Improving Planar Imaging for Semi-Pixelated Scintillation Crystals

The development and the application of planar image reconstruction algorithms to the experimentally collected charge from a γ- Camera system using homogeneous and semi-pixelated scintillation crystals is presented here. In order to overcome the irregularities near the limits of the field of view, formed by missing charge at the edges of the anodic grid, the new reconstruction algorithms are proposed with a mathematical model operating on the charge signals recorded from the anode wires of a Position Sensitive PhotoMultiplier Tube (PSPMT). According to this method, the incident photon generates a light distribution that can be modeled on the detective plane with a 2-dimensional Gaussian function, which is the result of the superposition of two analytically defined Gaussian curves with different intensity and width. In this way, there is a potential from experimentally collected charge distribution to determine the characteristics of the light distribution. Systematic measurements for CsI(Tl) scintillation crystals, irradiated isotropically by a Cs-137 source, were performed and their planar images were reconstructed. The experimentally obtained light characteristics inside the semi-pixelated and homogeneous scintillators are evaluated. Following the proposed model, image reconstruction results show improvement in spatial resolution compared to traditional reconstruction methods and the advantage of using semi-pixelated scintillation crystals over homogeneous is exhibited.