Poster — Wed Eve—24: Dosimetry of Lead Shield in Electron Radiotherapy: A Monte Carlo Evaluation

Abstract

We investigated the dosimetric characteristics of the beam profile, relative dose at the central beam axis (CAX) and penumbra width at the depth of maximum dose (), varying with different sizes and thicknesses of a piece of lead (Pb) layer using different clinical electron beams. Monte Carlo simulations (EGSnrc‐based code) validated by measurements were used to calculate beam profiles at for different Pb shields and electron beams with energies of 4, 9 and 16 MeV. Pb layers with different thicknesses (2–8 mm) and sizes () were placed at the center of an electron field on a Solid Water phantom. Beam profiles were determined at , and dosimetry under the Pb layer was studied. We found that 2 mm of Pb layer is adequate to provide 5 half‐value‐layer attenuation for the 4 MeV electron beams. However, for the 9 and 16 MeV electron beams, the relative dose at CAX and depends on the thickness and size of the Pb layer. The dosimetry of the beam profile under the Pb layer at depends on the penumbra at the edge of the layer, and beam attenuation varies with the thickness of the layer. The dosimetry of the profile also depends on the electron side‐scatter contributing to the CAX, and photon contamination produced by the Pb layer. The dosimetric data calculated by Monte Carlo simulations in this study provides useful information in selecting the Pb shield suitable for the protection of critical tissue in electron radiotherapy.