Exhibit Hall | Forum 3
Purpose: This study is to characterize the dosimetric properties of leaded vinyl (RPD, Inc.) for shielding and collimation in skin electron radiotherapy.
Methods: The 1.6mm-thick leaded vinyl is a flexible material with 0.5mm-Pb equivalence. It is easily cut into shapes for customized shielding and skin collimation. To assess its dosimetric properties, we conducted measurements of leaded vinyl shielded fields and collimated fields (diameter of 2-4 cm), compared them against those of reference fields. All measurements were performed in a solid water phantom at 100cm SSD, under 6x6cm 6 MeV and 9 MeV beams, produced by a Varian TrueBeam Linac. A 1x3mm W2 scintillator detector and Gafchromic films were used for measurements at depth from 0.5 to 2.5cm. Evaluated properties include residual dose behind shielding, backscatter factor, PDD, penumbra (20-80%) width and width of 90% isodose lines.
Results: 3 and 4 layers of leaded vinyl are needed to reduce the residual dose to below 5% for 6 MeV and 9 MeV beams, respectively. Backscattered dose of 6 MeV is 129.5% and reduced to 104.1% with 2mm of wax. 3mm of wax reduces 9 MeV backscattered dose from 135.1% to 109.6%. For collimated fields, as the diameter decreases from 4 to 2cm, we observed: (1) decrease of the maximum dose from 101.4% to 99.3% for 6 MeV and increase of the maximum dose from 102.2% to 114.4% for 9 MeV, (2) shift of maximum dose to surface for both energies, (3) increase of surface dose by 8.5% and 16.3% for 6 and 9 MeV respectively. As depth increases, the penumbra width increases from 0.2-0.4cm to 0.9-1.2cm, the width of 90% IDLs decreases from 1.5-1.6cm to 0.8-0.9cm.
Conclusion: Leaded vinyl is a suitable material for shielding and collimating low-energy electron treatments. Its dosimetric properties were collected and assessed for clinical application.
Funding Support, Disclosures, and Conflict of Interest: One author has a research grant from Ashland Inc., the manufacturer of GafChromic film.
Electron Therapy, Shielding, Collimation