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Organ Body Dose Simulation Using Monte Carlo Code EGS5 and Human Phantom and Bench-Marking with TL Dosimetry

Gilani, Nima | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42020 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Sohrabpour, Mostafa; Mahdavi, Rabie
  7. Abstract:
  8. Varian Clinac 2100 accelerator head was simulated using EGS5 Monte Carlo code. Phase space method was applied to this simulation. Two phase space plates were used in these simulations; one was inserted before the moveable jaws and the other one was placed after the jaws. The first plate was simulated for energy. And the second plate was to simulate each field size at the set energy. In the phase space method used in the EGS5 code one extracts the particle parametric information from a file as opposed to following the original particles that start at the source point. It is expected that this file to be a replica of the particles that pass the plate and further it should not add any appreciable error to the calculations. A 30×30×30 water phantom was used for dosimetry purposes. It was used in a voxelized form in order to calculate P.D.D. (percentage depth dose) and dose profile. The simulations were done for different SSD’s (source surface distance) and field sizes on the water phantom surface. Finally the simulation results were compared with the experimental results obtained from Pars hospital Tehran, Iran based on dosimetry chamber measurement and accordingly accelerator head parameters were tuned. In the second phase of the simulations a RANDO female phantom was used. Its geometry was derived by taking a CT scan and then voxelized using CTCREATE toolkit in BEAMnrc code. A usercode was developed in EGS5 in order to transform the BEAMnrc geometry file into EGS5 format. The simulations were done for 6 and 18 MV nominal energies of the accelerator and for fields ranging from 5×5 cm2 to 14×10 cm2. The average error was less than 3% for 6 MV nominal energy and less than 5% for 18 MV nominal energy of the accelerator. Simulation times varied from 1 to 20 hours according to energy and field size of the beam.

  9. Keywords:
  10. Monte Carlo Method ; Accelerators ; State Space ; Thermoluminesence Dosimetry ; Equivalent-Man Phantom ; TL Dosimetry ; Varian Accelerator ; Voxel ; EGS5 Code

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