Physical measurements for quality control in industrial radiation sterilization

The use of ionizing radiation has brought about a growing industry for the sterilization of disposable surgical equipment, medical supplies, and containers for biological specimens. For many products, irradiation has become an alternative to autoclaving or gas treatment by ethylene oxide. Over fifteen years of experience with industrial sterilization by cobalt-60 gamma radiation have shown that radiation methods provide a clear advantage over gas sterilization, in that sterilization can be performed on non-permeable sealed packages. Moreover, regulatory agencies, such as the Food and Drug Administration in the U.S.A., are reappraising the requirements for sterility assurance. For products released to the public, consideration is now being given to the use of physical dosimetry, i.e., the measurement of radiation dose by physical methods. This is based on a knowledge of the microbial burden of the product before sterilization and on the probability of killing microorganisms by a given radiation dose. Because physical dosimetry is easier to control and less complicated than biological tests, it may be considered in the future the basis for quality assurance of the sterilized product. Some of the problems associated with standardized measurement techniques in radiation sterilization include the choice of dosimetry and its calibration, as well as methods and procedures used to minimize errors due to variations in radiation flux density, source geometry with respect to the product, and environmental factors. (author)