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Effect of a flattening filter on the surface and build-up doses for high-energy photons produced with a varian TrueBeam STx linear accelerator
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F. Alkaya   , C.K. Akbas , S.Ç. Karacam , H.B. Becerir |
| Department of Healt Physics,Graduate School of Health Sciences, Istanbul Medipol University, 34810, Istanbul, Turkey |
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Abstract: (21 Views) |
Background: The aim of thise study was to measure and determine the surface and build- up region doses at different field sizes on the central axis of 6 and 10 MV with flettening filter (FF) and without flettenin filter (FFF) high-energy photon beams, which are commonly used in clinical radiotherapy applications, and to reveal the difference between FF and FFF beams. Material and Methods: The dose measurements were made using a parallel-plate ion chamber and a water-equivalent solid water phantom for a field size of 5 × 5, 10 × 10, and 20 × 20 cm2, with a source skin distance of 100 cm. Results: The relative surface doses for 6 MV FF high-energy photons are 10.9%±0.007%, 16.4%±0.010% and 26.9%±0.014% for field sizes of 5x5, 10x10 and 20x20 cm2. For 6 MV FFF they are 14.7%±0.010%, 19.7%±0.010% and 27.2±0.009% respectively. The relative surface doses for 10 MV FF high-energy photons are 6.3%±0.010%, 12.0%±0.007% and 23.7%±0.010% for field sizes of 5x5, 10x10 and 20x20 cm2. For 10 MV FFF they are 9.7%±0.010%, 13.8%±0.007% and 20.1%±0.007% respectively. Conclusion: It was observed that the relative surface doses increased in FFF for 6MV compared to FF photon beams, and increased in 5x5 and 10x10 cm2 field sizes and decreased in 20x20 cm2 field size for 10MV photon beam. These results may have important implications in radiotherapy applications where skin dose is important. |
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| Keywords: TrueBeam STx, flattening filter free, surface dose, build-up dose, radiotherapy. |
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Full-Text [PDF 823 kb]
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Subject:
Radiation Biology
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