Geometric Sensitivity of Variable Pinhole SPECT with a Keel-edge Pinhole Model

A variable pinhole (VP) collimator is formed by stacking several tungsten plates with different apertures. The configuration of the VP can be optimized for target region-of-interests at different rotation angles. Hence, both the resolution and sensitivity of the system can be improved. However, it is difficult to analytically implement the exact system model that simulates the step shapes between adjacent layers. In this study, we compared the conventional keel-edge and knife-edge pinhole models with the VP model using simulations. The keel-edge and knife-edge models were evaluated based on various specifications to identify the optimum system model. The simulation results showed that the keel-edge model with 80% channel length (keel-edge 80%) elicits the best performance with a fixed acceptance angle and pinhole plate thickness. The results in this study are expected to be applied to full-scale SPECT with a VP collimator which is currently under development.