Characterization and verification of lead thickness of commercially available lead foil tape for the measurements of lead equivalency of radio‐protective shields

PURPOSE: Radiation protective apparatus is normally specified in "millimeter" of lead equivalence. Typically, it is less than 0.5 mmPb with the exception of lead eyeglasses, which may be 0.75 mmPb equivalent. Upon discovery of commercially available lead foil tape, manufactured by 3M™ "Lead Foil Tape 421" (LFT) which is designed for industrial utility applications. We set out to determine if this LFT can, indeed, be employed as the reference lead in the evaluation of lead equivalency of various protective apparatus. METHOD: The LFT is cut to appropriate size (50 mm × 50 mm) and stacked for varying the total lead thickness for the transmission measurements. The transmission curves are obtained following the geometry spelled out in ASTM Designation F3094‐14 standards. The radiation beam qualities corresponding to modern cardiovascular angiography equipment in the range of 60~120 kVp, in increments of 10 kVp, and in combination with the spectral shaping filters of 0, 0.1, 0.2, 0.3, 0.6 and 0.9 mmCu were employed for characterization of the lead foil tape. The transmission data of lead pieces with known thicknesses (1/64", 1/32" and 3/64") are superimposed on the lead foil tape transmission curves to validate that the 3M™ LFT is indeed usable as 0.1 mm lead. RESULTS: The transmission ratio (data points) of lead pieces with known thicknesses at various radiation beam qualities mentioned above, fall right onto the transmission curves of 3M™ LFT with better than 2% accuracy. Therefore, it is indeed behaving like 0.1 mm thick lead sheet, based on the superimposed transmission curves. The 3M™ "Lead Foil Tape 421" is employed as the reference lead for evaluation of radiation protective apparatus at this institution. Verification of lead protective apparatus with unknown lead equivalence can now be determined with a high accuracy and certainty.