Method for determining the radiation protection provided by shielding garments used to protect workers in medical fluoroscopy, or in other applications where the user is in close proximity to the object being examined by a fluroroscope operating at voltage potentials below 130 kV
This standard is needed by manufacturers, users and qualified experts evaluating performance of radiation shielding garments used mainly in medical fluoroscopy. Current testing methods for evaluating radiation protection of shielding garments are based on the narrow beam attenuation test using a direct x-ray beam. This test produces an inaccurate evaluation of the protection expected by the wearer for two reasons. One is that it excludes secondary radiation emitted from the protective material, and the second is because the direct beam setup used in the standard test does not emulate the radiation emissions encountered by the user. First the test design excludes secondary radiations produced in the garment from reaching the detector. When shielding garments are produced with elements with atomic numbers lower than that of lead, there is a substantial contribution of fluorescent radiation emitted by the material under conditions of use. These fluorescent emissions are largely absent when the garment contains only lead (Z=82) or bismuth (Z=83). Because the narrow beam attenuation test shows higher attenuation per unit mass of certain lighter elements such as barium, tin, antimony or similar elements, modern shielding garments may only contain these lighter elements resulting in a lighter product more desirable to users required to wear the garment for extended periods. The inaccuracy from excluding secondary radiation means that the attenuation test overestimates the actual protection. The second problem is that the scattered radiation that produces nearly all of the hazard to workers using medical fluoroscopes is of lower energy than that produced in the direct beam. A test that only evaluates direct beam exposure tends to underestimate the actual protection of the shielding.
Keywordsfluoroscopy; scattered radiation;
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top