Optimization of each layer's hole of a variable collimator for environmental radiation monitoring using GATE

Abstract

The purpose of this work is to optimize the number of holes in each layer with the Monte Carlo simulation tool, GATE, a variable collimator of the non-replaceable types that makes up for pinhole collimator's shortcomings. The material is tungsten and the detector size is 25.8 × 25.8 × 3.0 mm3 GAGG with 0.7 × 0.7 × 3.0 mm3 pixels arranged in 29 × 29 × 1 and performance is evaluated based on the field-of-view, sensitivity, and spatial resolution by magnification for the point source 137Cs. Simulations were designed to optimize the five layers from 44, 55, 11, 55, 44 to 6, 9, 3, 9, and 6 to meet the feasibility of manufacturing collimators. We also confirmed performance errors of 5.7% sensitivity and 5.2% spatial resolution compared to using an ideal variable collimator for all parameters, such as specific purposes and magnification scale. Through these results, we propose an environmental monitoring system that can be used for diverse radiation disasters by enabling image magnification and transforming the shape of the collimator.