Water equivalence evaluation of PRESAGE® formulations for megavoltage electron beams: a Monte Carlo study

Tina Gorjiara, Zdenka Kuncic, Robin Hill, John Adamovics, Clive Baldock

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

To investigate the radiological water equivalency of three different formulations of the radiochromic, polyurethane based dosimeter PRESAGE® for three dimensional (3D) dosimetry of electron beams. The EGSnrc/BEAMnrc Monte Carlo package was used to model 6-20 MeV electron beams and calculate the corresponding doses delivered in the three different PRESAGE® formulations and water. The depth of 50 % dose and practical range of electron beams were determined from the depth dose calculations and scaling factors were calculated for these electron beams. In the buildup region, a 1.0 % difference in dose was found for all PRESAGE® formulations relative to water for 6 and 9 MeV electron beams while the difference was negligible for the higher energy electron beams. Beyond the buildup region (at a depth range of 22-26 mm for the 6 MeV beam and 38 mm for the 9 MeV beam), the discrepancy from water was found to be 5.0 % for the PRESAGE® formulations with lower halogen content than the original formulation, which was found to have a discrepancy of up to 14 % relative to water. For a 16 MeV electron beam, the dose discrepancy from water increases and reaches about 7.0 % at 70 mm depth for the lower halogen content PRESAGE® formulations and 20 % at 66 mm depth for the original formulation. For the 20 MeV electron beam, the discrepancy drops to 6.0 % at 90 mm depth for the lower halogen content formulations and 18 % at 85 mm depth for the original formulation. For the lower halogen content PRESAGE®, the depth of 50 % dose and practical range of electrons differ from water by up to 3.0 %, while the range of differences from water is between 6.5 and 8.0 % for the original PRESAGE® formulation. The water equivalent depth scaling factor required for the original formulation of PRESAGE® was determined to be 1.07-1.08, which is larger than that determined for the lower halogen content formulations (1.03) over the entire beam energy range of electrons. All three of the PRESAGE® formulations studied require a depth scaling factor to convert depth in PRESAGE® to water equivalent depth for megavoltage electron beam dosimetry. Compared to the original PRESAGE® formulation, the lower halogen content formulations require a significantly smaller scaling factor and are thus recommended over the original PRESAGE® formulation for electron beam dosimetry.
Original languageEnglish
Pages (from-to)455-463
Number of pages9
JournalAustralasian Physical and Engineering Sciences in Medicine
Volume35
Issue number4
DOIs
Publication statusPublished - 2012

Keywords

  • PRESAGE®
  • Electron beam dosimetry
  • Monte Carlo
  • EGSnrc/BEAMnrc

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