Low-Dose Gamma Radiation Dosimetry Using a 60Co Irradiator: Experimental Validation and Reproducibility

Abstract

Abstract: Low-dose ionizing radiation has been increasingly investigated in preclinical research due to its potential to modulate biological responses while minimizing the risk of significant tissue damage. However, the scientific reliability of studies conducted in the milliGray dose range strongly depends on the availability of rigorous, reproducible, and traceable dosimetric protocols. Small variations in irradiation geometry, exposure time, or shielding conditions may result in substantial uncertainties when low doses are involved, reinforcing the importance of precise dosimetric characterization and standardized experimental methodologies. In this context, the present study describes the development and validation of a low-dose gamma radiation dosimetry protocol (~41.3 mGy) implemented using a multipurpose cobalt-60 (60Co) irradiator at the Gamma Irradiation Laboratory (LIG) of the Nuclear Technology Development Center (CDTN), Brazil. The protocol was designed to support preclinical experiments, with emphasis on accuracy, reproducibility, and strict compliance with radiological protection requirements. Dosimetric planning was based on the Beer–Lambert exponential attenuation law, applied to the dimensioning of lead shielding and to the definition of the transmitted beam fraction required to achieve the target dose. These theoretical calculations were integrated with the geometric configuration of the irradiation system, including source-to-sample distance and exposure time, to ensure controlled dose delivery within the milliGray range. A conservative experimental configuration was adopted, employing the maximum operational distance available in the irradiator to reduce dose rates and improve temporal control during short irradiation times. Lead shielding elements were used to stabilize the irradiation setup and to ensure consistent attenuation of the gamma beam. All irradiation procedures followed the routine operational practices of the LIG/CDTN, ensuring dosimetric traceability and adherence to national radiological protection standards. The results demonstrate that the proposed protocol enables the controlled and reproducible delivery of low gamma doses with suitable radiation field uniformity for preclinical applications. Overall, the methodology provides a robust and adaptable dosimetric framework for experimental studies requiring low-dose gamma irradiation, contributing to improved standardization, safety, and comparability in preclinical dosimetry research.