Abstract
Purpose: Uncertainties in radiochromic film dosimetry applied to microbeam radiation therapy (MRT) dosimetry at the Canadian Light Source (CLS) are investigated. A dose‐dependent change in film response as a function of microbeam width is characterized and its impact on peak‐to‐valley dose ratios (PVDRs) evaluated. Variation across the MRT collimator and inhomogeneity in film construction are also studied. Methods: Gafchromic® EBT2 film was used to measure doses from a filtered synchrotron source on the surface of solid water for microbeams ranging from 10 micrometers to 1 mm and doses between 0.4 – 74 Gy. The microbeams were generated using a variable slit or a MRT collimator (50 micrometer slits, 400 micrometer spacing). The film was scanned with an Epson Perfection V700 Photo digital scanner (4800 dpi). Corresponding Monte Carlo (PENELOPE) simulations were performed.Results: A dose‐dependent reduction in film response with decreasing microbeam width was observed. The measured ratio of dose for a 50 micrometer slit beam relative to a 1 mm beam ranged from 0.15 and 0.56, decreasing as the dose is increased. A corresponding simulation predicts a ratio of 0.91. Depending on dose, measured PVDRs ranged from 7 to 64. Variability in measured doses between different slits of the MRT collimator is also problematic, with deviations from the average of up to 26% in the microbeam path, and over 70% between two microbeams. Inherent inhomogeneity in optical density of the unexposed EBT2 film may also result in uncertainties of approximately 0.15 Gy. Conclusions: Although the high resolution of radiochromic film makes it a potentially attractive two‐dimensional dosimeter for MRT, large uncertainties arise from variations in dose‐response as a function of microbeam size, and spatial inhomogeneity of the response. These problems must be addressed before film can be considered for accurate measurement of absolute doses, and even relative metrics.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.