Evaluation and verification of a simplified lead equivalency measurement method.

ABSTRACT

PURPOSE: This technical note presents an inexpensive tool and method for determining lead equivalency using digital radiography x-ray equipment. METHODS: A test tool was developed using commercially available lead tape (3M™ Lead Foil Tape 421). The test tool consisted of nine varying lead thick squares arranged in a larger square (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 1.0 mm). It was imaged on a DR plate with a digital portable x-ray unit across a range of energies (60-120 kVp) and two beam filtrations. Lead equivalency was determined by using the linear relationship between dose to the detector and pixel values in the raw images. The lead equivalency of the tape was validated using known lead thicknesses (physically measured with caliper). Additional lead equivalency measurements were made for protective eyewear, a thyroid shield, and a lead apron. RESULTS: The test tool and method measured the two known lead thicknesses to be -9.7% to 7.1% different from the actual values across the range of energies under normal x-ray beam conditions and under a 1-mm copper filtered x-ray beam. The additional lead equivalency measurements of radiation protection apparel across energies ranged from -6% to 20% for both beam conditions when compared with the values provided by the manufacturer. CONCLUSION: This work validates the test tool and methodology as an inexpensive alternative to checking the lead equivalency of radiation protection apparel in a clinical setting. The methodology is equipment independent with a few prerequisites.