Simulation Study on the Effect of Constant Hole Length of Curved Diverging Collimators for Radiation Monitoring Systems

The nuclear accident that occurred in Fukushima, Japan, in 2011, resulted in considerable radiation leaks and mass exposure owing to an insufficient initial response to the disaster. To prevent similar disasters in the future, their cause should be identified, analyzed, and addressed using radiation-monitoring systems. The core component of a radiation-monitoring system is the gamma camera. It consists mainly of a gamma detector and a collimator. We proposed a diverging collimator that incorporates a novel concept of a curved surface such that the collimator hole length is constant for all the incident hole angles. Therefore, the sensitivity is likely to be more uniform across the field of view (FOV) compared with the case of the conventional flat collimator. Through a simulation study, we determined the collimator parameters and compared the performance of the curved collimator with that of the conventional flat collimator. The results revealed the feasibility of achieving higher uniform sensitivity, up to 10.5% at the edge of the FOV by using the proposed curved collimator. The average peak-to-background ratio (PBR) of the curved collimator was determined to be higher by 10.8% across the entire FOV. This indicates that it produced a more distinct signal than the flat collimator. In our future research, we intend to fabricate a curved collimator and evaluate its performance experimentally.