Measurement of lead equivalence for protective aprons

Three computer codes have been applied to X-ray beam transmission measurements through lead vinyl to determine lead equivalence. One method used an analytic approach applied to narrow-beam transmission measurements, while two other codes were applied to broad-beam transmission measurements. Of the two broad-beam codes, one used an iterative analytic method of calculation while the other was based on fitted data from Monte Carlo simulation. Transmission measurements were made with standard X-ray equipment at 80, 100 and 120 k Vp. The results show a close agreement between all three methods. Agreement was within 3% for all paired measurements between the two broad-beam transmission codes at 100 k Vp. Agreement between narrow-and broad-beam determinations was also good on average over all beam energies with a larger spread in some paired results. No effects of beam energy were evident between any of the methods. This result seems to indicate that simple iterative computer codes can be safely used to estimate lead equivalence. The use of broad-beam geometry appears to be the preferable method of determination, due to the close agreement between analytic and Monte Carlo based methods. However should the sample size prevent broad-beam geometry it is clear that narrow-beam results are quite acceptable in clinical evaluations. Copyright (2000) Australasian Radiation Protection Society Inc