SU‐D‐134‐04: On the (f)utility of Measuring the Lead Equivalence of Protective Garments

Purpose: Verifying claims regarding lead equivalence for lead‐composite and lead‐free garments is difficult. Current standards only require measurement of lead equivalence at a single beam quality. A garment may provide a high degree of protection at the specified beam quality, but underperform at others. We sought to measure the lead equivalence of several protective garments and propose a better method for quantifying protective value. Methods: We measured the penetration of primary and scattered radiation through lead sheets and three garments of nominal 0.5 mm lead equivalence, one lead and two lead‐free. Penetration was measured using nominal 60, 80, 100, and 120 kVp beams. Using polynomial least‐squares fits to the measured data of penetration through lead sheets, we determined the lead equivalence of the protective garments. Results: The lead garment was 0.5 mm lead equivalent across all beam qualities. While the maximum lead equivalence of the lead‐free garments occurred at the manufacturer‐specified beam quality, neither garment was 0.5 mm lead equivalent. The lead equivalence of the lead‐free garments was a strong function of beam quality and nature of the radiation. The lead equivalence of the lead‐free garments in primary beams ranged from 0.40 to 0.47 mm and in scattered beams ranged from 0.37 to 0.46 mm. We also calculated linear fits of penetration through lead as a function of HVL. We propose the Diagnostic Radiation Index of Protection (DRIP), a weighted sum of the penetration percentage across a range of beam qualities. Conclusion: The protective value of garments from both primary and scattered radiation is a strong function of beam quality. Assessment of protective value should be performed across a range of beam qualities. Methods for performing such assessment must be developed and must specify beam qualities, measurement geometry, and the appropriate weighting across the beam quality range for different applications.