On the relation between the spatial dose integrity and the temporal instability of polymer gel dosimeters

Koen Vergote*, Y. De Deene, E. Vanden Bussche, C. De Wagter

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)

Abstract

When irradiating a polymer gel dosimeter to relatively high doses, edge enhancing effects (overshoots) may be noticed near dose gradients, resulting in a loss of spatial dose integrity. These overshoots are believed to be a consequence of monomers diffusing into the high-dose region, where they react with long-living macroradicals. Macroradicals may also be responsible for the temporal chemical instability of post-irradiation polymerization that occurs in the polymer gel dosimeter. In this study, a mathematical model is proposed that simulates the edge enhancing effect. The model is based on the hypothesis that the macroradicals are responsible for both the temporal instability and loss of spatial dose integrity. All input parameters for the model are obtained from independent experiments. The edge enhancing effect is studied both experimentally and theoretically for polymer gel dosimeters with various gelatin concentrations. The change in the edge enhancement is also investigated over post-irradiation time. Comparisons between polymer gel measurements and simulations confirm the hypothesis that there is a strong relation between the spatial and temporal instabilities.

Original languageEnglish
Pages (from-to)4507-4522
Number of pages16
JournalPhysics in Medicine and Biology
Volume49
Issue number19
DOIs
Publication statusPublished - 7 Oct 2004
Externally publishedYes

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