Measurement of the Attenuation Properties of the Protective Materials Used as a Thyroid Guard and Apron for Personnel Protection against Diagnostic Medical X-rays


In the medical field, some protective materials incorporating lead or high-Z elements are used as lead-equivalent aprons or garments and thyroid guards for the protection of personnel against X-rays. However, in recent years, non-lead protective materials have become widespread in radiology because of their light weight and durability. Lead (Pb) has been replaced by non-toxic elements in conventional aprons or garments, which are generally made from Pb materials. Therefore, it is essential to experimentally demonstrate the Pb-equivalence of any protective material to determine whether it complies with nominal thicknesses of 0.25 mm, 0.35 mm, 0.5 mm or 1 mm Pb. In this study, the X-ray attenuation properties of some protective materials made from elastomers loaded by high-Z elements (such as Sb, Sn, W, Ba, etc.) were experimentally determined using both narrow and broad-beam geometry conditions. The X-ray attenuation properties have been determined in terms of the attenuation ratio (F), buildup factor (B) and lead equivalent (dPb) for the investigated protective materials. These properties have already been stated by the manufacturers of the protective materials. From the air kerma values measured with a calibrated ionisation chamber, it was found that the mean attenuation ratios change from F = (90.7 +/- 0.2)% to (20.9 +/- 0.1)%, and the dose build-up factors are within the range of B = 1.90 to 2.75 at 80 kVp. The F-ratios change from F = (41.8 +/- 0.1)% to (8.5 +/- 0.1)%, and those B-factors remain in the range of B = 0.85 to 1.64 at 100 kVp. Among the attenuation properties for the x-ray protective materials, the most distinctive property is its lead equivalence. When they are compared with each other in terms of this property, e.g., for the dPb = 0.5 mm Pb thickness stipulated by standards, it is found that some of the investigated materials did not meet this criterion when exposed to X-radiation at diagnostic beam qualities. This result clearly indicates that the quality control tests of any protective material should always be performed to verify its compliance to the attenuation requirements before it is used in medical X-ray facilities for the radiation protection of the personnel.


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