Reducing shield thickness and backscattered radiation using a multilayered shield for 6–10 MeV electron beams

Martin Butson*, Tom Chen, Somkhit Rattanavoang, James Hellyer, Alison Gray, Vinod Nelson, Richard Short, Satya Rajapakse, James Lee, Gerald Fogarty, Michael Izard, Robin Hill

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

Intraoral and external electron shields used in radiotherapy are designed to minimize radiation exposure to non-treatment tissue. Sites where shields are used include but are not limited to, the treatment of lips, cheeks and ears whilst shielding the underlying oral cavity, tongue, gingival or temporal region. A commonly known and published effect, concerns the enhancement in dose that can occur on the beam side on an electron shield caused by an increase in electron backscatter radiation. In this work a lead shield has been designed incorporating copper, aluminium and wax in a step down filter arrangement to minimise backscatter whilst minimizing overall shield thickness for better clinical setup and ease of use. For electron beams ranging from 6 to 10 MeV, a standard shield design of 4 mm lead, 0.6 mm copper, 1.0 mm aluminium and 1.5 mm wax (3.1 mm added filtration, 7.1 mm total thickness) provided adequate backscatter and transmission reduction to match a standard 4.5 mm lead and 10 mm wax (total thickness 14.5 mm) electron shield. Dose enhancement values of no more than 10 % were measured utilising this shield design with a 50 % reduction in shield thickness. The thinner shield will not only allow easier patient set up but should be tolerated better by patients when mucosal reactions occur as they place less physical pressure on these sites during treatment due to their smaller size.

Original languageEnglish
Pages (from-to)619-626
Number of pages8
JournalAustralasian Physical and Engineering Sciences in Medicine
Volume38
Issue number4
DOIs
Publication statusPublished - 1 Dec 2015
Externally publishedYes

Keywords

  • Electron
  • Radiation
  • Radiotherapy
  • Shielding

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