Physical Validation of the Survey Meter Detector Count Rate Efficiencies for the GECAT Software
Abstract
Purpose
The Gamma-Emitter Contamination Assessment Tool (GECAT) is a software application designed to perform in-field radiological triage. The application relies on detector count rate efficiency data generated by performing Monte Carlo radiation transport on digital phantoms and detector CAD models. A physical experiment was conducted to compare against computational results and validate the detector efficiency portion of the GECAT dose calculation algorithm.
Methods
To validate the accuracy of these computationally derived values, physical detector efficiency measurements were performed using the adult female CIRS ATOM anthropomorphic phantom. Radioactive sources were placed inside the phantom in the lung or abdomen regions, representing common accumulation points for inhaled radionuclides in the body. Cobalt 60, Cesium 137, and Barium 133 were surveyed separately to cover high, medium, and low energy emissions. Anterior and posterior screening positions were used at lung and abdomen locations, with detector distances of 6 and 30 cm. The Ludlum detectors used were the 44-2, 26-3, 26S, and 44-9 models, containing both Geiger-Muller, Sodium-Iodide, and Cesium-Iodide technologies. Following the physical measurements, identical geometries were modeled computationally. A high-quality digital mesh phantom was derived from CT images of the CIRS phantom. Detector CAD models were obtained from the manufacturer. These digital assets were imported into Monte Carlo particle transport software to produce simulated count rate efficiency values.
Results
Measured and simulated count rate efficiencies showed strong agreement, with ratios approaching unity across tested configurations. These results support the reliability of GECAT for rapid, in-field dose assessment.
Conclusion
This study validates the method GECAT employs to generate detector efficiency data for dose estimations. The study also validates detector CAD models used and supports the reliability of the radiation transport software. Grounding the GECAT application in a physical validation study ensures it can be trusted for in-field radiation dose assessment in individuals.