Deciding between an X-Ray and 137Cs Irradiator - It's not just about Energy Spectra

摘要

Irradiators utilizing radioactive cesium-137 (Cs-137) or cobalt-60 (Co-60) gamma-ray sources have been used for biological applications for many decades. These applications include irradiation of much of the nation's blood supply and radiation biology research. In 2005, the U.S. Nuclear Regulatory Commission was assigned the task of preventing the misuse of radioactive materials by persons with malicious intentions; gamma-ray sources, in particular, were given high priority. This resulted in increased security requirements, including constant surveillance, controlled access and personnel background checks. As a result of such regulations being introduced, organizations considering the purchase of a gamma-ray irradiator for the First time or as a replacement to an existing one due to radioactive decay, are now looking into alternative technologies, primarily an X-ray irradiator. To make an educated decision on whether a particular type of X-ray irradiator is of sufficient equivalency to a particular type of Cs-137 irradiator for specific applications, one must rely on relevant published comparison studies from other researchers, or perform the comparison studies on their own. This work focuses on the comparison of the radiation physics aspects of two Cs-137 irradiator models and three X-ray irradiator models, for the purpose of determining whether the X-ray irradiator models could validly replace the Cs-137 irradiator models for certain applications. Although evaluating the influence of relative biological effectiveness (RBE) differences among irradiators could be part of this study, that has been left for a related publication focused on the theoretical aspects of this topic. These evaluations were performed utilizing 47-g and 120-g tissue-equivalent rodent dosimetry phantoms. Our results indicate that, depending upon the user's dose uncertainty budget and maximum areal density of specimens to be irradiated, the RS 2000 160 kVp X-ray irradiator, X-RAD160 X-ray irrad