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Influence of ridge filter material on the beam efficiency and secondary neutron production in a proton therapy system

Riazi, Z ; Sharif University of Technology | 2012

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  1. Type of Document: Article
  2. DOI: 10.1016/j.zemedi.2012.06.001
  3. Publisher: Elsevier , 2012
  4. Abstract:
  5. In this work, the 3D proton dose profile is calculated in a homogenous water phantom using a Monte Carlo application developed with the Geant4 toolkit. The effect of the ridge filter material (for SOBP widths of 6, 9 and 12 cm) on the homogeneity of the dose distribution, secondary neutron production and beam efficiency are investigated in a single ring wobbling irradiation system. The energy spectrum of secondary neutrons per primary proton at various locations around the phantom surface is calculated. The simulation revealed that most of the produced neutrons are released at slight angles which enable them to reach the patient and consequently to be hazardous. Also, the homogeneity of the dose distribution at the proximal edge of spread out Bragg peak (SOBP) field is deteriorated due to the scattering of protons in the ridge filter. It is found that for reducing the above mentioned destructive effects, usage of a PMMA ridge filter is better than Al one. For a similar value of 9 cm water equivalent thickness, beam widening radius of Al at isocenter is twice of PMMA. Furthermore, for uniform irradiation of the target, the beam efficiency of the system for Al is less than of PMMA and also regarding to the secondary neutron production PMMA is a better choice
  6. Keywords:
  7. Geant4 ; Secondary neutrons ; Wobbling spreading system ; Controlled study ; Energy transfer ; Energy yield ; Equipment design ; Filter ; Mathematical computing ; Mathematical model ; Monte Carlo method ; Neutron dosimetry ; Neutron radiation ; Phantom ; Process design ; Process technology ; Proton therapy ; Radiation dose distribution ; Radiation field ; Radiation ridge filter ; Radiation scattering ; System analysis ; Computer Simulation ; Equipment Failure Analysis ; Filtration ; Light ; Models, Theoretical ; Neutrons ; Protons ; Radiotherapy, Conformal ; Scattering, Radiation
  8. Source: Zeitschrift fur Medizinische Physik ; Volume 22, Issue 3 , September , 2012 , Pages 231-240 ; 09393889 (ISSN)
  9. URL: http://www.sciencedirect.com/science/article/pii/S0939388912000621