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Effect of collimator scatter factors on dose calculation of different breast cancer cases in radiotherapy
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| M.A. Eid, H.S. Mohammed, A.M. Abdelaal, S. Taha |
| Radiotherapy Department, Nasser Institute, Cairo, Egypt , mohamedahmed@gstd.sci.cu.edu.eg |
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Abstract: (494 Views) |
Background: The present study aims to estimate the effect of collimator, phantom and Multi-Leaf Collimator (MLC) scatters on dose calculation in different breast cancer cases using acrylic, brass build-up caps and acrylic mini-phantom in the measurements. Materials and Methods: Collimator scatter factors (Sc), phantom scatter factors (Sp) and MLC transmission factors for different field sizes ranging from 1 × 1 cm2 to 40 × 40 cm2 for energies 6 MV and 15 MV were measured using acrylic mini-phantom (PTW and local mini-phantom), acrylic build up cap and brass build up cap where the farmer ionization chamber was used as detector in this study and semiflex detector was used but only with small field sizes from 1 × 1 cm2 to 4 × 4 cm2 and scatter effect on the dose calculation in different breast cancer cases was evaluated. Results: The results in this study show that there is no significant difference between MLC transmission factors using acrylic mini-phantom and brass build-up cap with energy 6 MV where the transmission factor value is 0.007 and 0.0071 with acrylic mini-phantom and brass build- up cap, respectively. Also it is clear that brass build-up cap gives the highest collimator scatter factors results where collimator scatter factors start at value 0.963 at field size 4 × 4 cm2 then increase gradually to end at point value 1.049 at field size 40 × 40 cm2. In breast cancer cases, there is sharp increase in organ at risk doses with brass build-up cap. Conclusion: From this study it is evident that almost there is large variation between the acrylic build-up cap, acrylic mini-phantom and brass build-up cap where brass build-up achieve higher results in most measurements. |
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| Keywords: Collimator scatter factor, mini-phantom, build-up cap, brass, MLC transmission. |
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Full-Text [PDF 1027 kb]
(123 Downloads)
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Type of Study: Original Research |
Subject:
Radiation Biology
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