Room: AAPM ePoster Library
Purpose: Tungsten eye shields clinically limit dose to the lens and eye when treating superficial facial lesions using 6-9 MeV electrons. Eye shields may be limited in quantity, require sterilization, may interfere with mask immobilization and/or bolus, require anesthetic, and are uncomfortable for the patient. U.S. coin currencies are produced with consistent dimensions and composition, consist primarily of copper, are more widely available than lead sheets or eye shields, as a widely available alternative to an eye shield or lead sheets, which reduces the need for sterilization, not as toxic as lead, and matches the dimensions necessary for blocking the eye.
Methods: Stacks of U.S. Currency denominations (cent, nickel, quarter and dollar), lead sheets, and large, medium, small 3 mm Tungsten eye shields (RPD) were placed on the Sun Nuclear IC PROFILER with each material stack centered on a detector and attenuating the beam along a different profile. Multiple measurements were taken using a Varian Truebeam with all available electron energies (6, 9, 12, 16, 20 MeV) at 100 cm SSD using a 15 cone. Coins were progressively added to their stack to investigate the attenuating properties of each material. Analysis was performed in Matlab and compared to composite ESTAR calculations.
Results: High copper content coins provided reasonable attenuation, leaving cents (primarily zinc) unsuitable. Coins performed similarly, with thicknesses of approximately 4.5, 5.0, 7.5, 12, and 14 mm required to reduce transmission below 10% for 6, 9, 12, 16, and 20 MeV electron beams, respectively. Measured values matched well with ESTAR expected values but must account for the 9 mm water equivalent buildup of the Profiler.
Conclusion: U.S. Currency is a feasible alternative to tungsten eye shields in some situations, but these results require approximately 5-10 mm moldable bolus for additional attenuation and coin stack positioning.