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Simulation of Intensity Modulated Radiation Therapy (IMRT) and Assessment of the Time Parameter

Shahi Maynbolagh, Rezgar | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49647 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Vosoughi, Naser; Mahdavi, Rabi; Robat Jazi, Mostafa
  7. Abstract:
  8. It is necessary to evaluate dosimetry accuracy in the framework of advanced methods for radiation therapy such as Intensity Modulated Radiation Therapy (IMRT) to ensure reliability of a proposed treatment. The ability of the Monte Carlo codes to model linear accelerator (LINAC) and to calculate the exact dose distribution in clinical radiation therapy is one of the reasons to use such codes. The purpose of this project is to validate a treatment planning system with BEAMnrc and DOSXYZnrc Monte Carlo codes. In this study, the dose distribution obtained from DOSXYZnrc in considered to be thr main criterion with which the dose distribution obtained from treatment planning system is assessed and validated. For this purpose, a patient's Nasopharynx district's CT image and treatment plan has been used. One of the other purposes of this study is to investigate the effect of time parameter on treatment quality. In radiation therapy by LINAC, time is interpreted as Monitor Unit (MU) which is equal to 1 cGy deposited dose in the maximum dose depth in a field of 10×10 cm^2 of water phantom. Hence, the variation of the MU due to energy variation is also investigated. Therefore the integral dose and the hemogenity index for the 6 and 15 MV were evaluated. Difference in integral dose between Monte Carlo simulation and treatment planning system for 6 and 15 Mev are respectevly in 1.13 to 2.74 interval and 1.18 to 2.65 interval. The PTV dose hemogenity index for 6 and 15 MV were respectivly 0.1826 and 0.216 which had 1.22 and 1.38 percent deviation from the obtained results from the treatment planning system. As a result, the Monte Carlo method is a suitable criterion for evaluating the algorithms' efficiency for calculating the dose in the patient's body. Furthermore, the 6 Mev has a better covering on the PTV than the 15 MV, resulting that the 6 MV treatment planning is more efficient for head and neck tumors
  9. Keywords:
  10. Monte Carlo Method ; Radiotherapy ; Intensity Modulated Radiation Therapy (IMRT) ; Multileaf Collimator ; Nasopharynx Carcinoma

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