Thesis (Ph.D.) - Cairo University - Faculty of Science - Department of Biophysics

The aim of the study is to evaluate the dependence of photo-neutron production on different variables and different treatment methods (IMRT and 3DCRT techniques) using TLD (600/700) and MC simulation. The equivalent neutron doses were measured at different field sizes, depth in phantom, gantry angles and different distances along patient couch. The equivalent neutron doses were measured for 5 Prostate cancer cases using TLD (600/700).The equivalent neutron doses were measured for selected rectum case using TLD (600/700) and Geant 4 simulation. The results showed that: The measured equivalent neutron doses decreases from0.2 mSv/Gy to0.09 mSv/Gy as increases field sizes from 2x2 cm2 to 20x20 cm2. The measured equivalent neutron doses was maximum (0.15 mSv/Gy) at dmax =5 cm and decreases gradually as increases depth in phantom reaches to 0.07 mSv/Gy at 10 cm. The measured equivalent neutron doses decreases from 1.5mSv/Gy to0.02 mSv/Gy when measured at isocenter and at 100cm along the patient couch. Using 3DCRT for PTV and OARs were ranging from 0.027 to 0.39 mSv per photon Gy and for IMRT were 0.135 to 2.34 mSv per photon Gy. The measured equivalent neutron doses for rectum case were ranging from 0.04 to 0.24mSv per photon Gy, this result nearly the same calculated by MC. In conclusion the photo-neutron production is decreases as increases field size and distance from isocenter along patient couch while increases with depth in phantom up to dmax and decreases gradually as increases depth in phantom. IMRT requires longer beam-on time than 3DCRT leading to worse OARs sparing and increase the production of photo-neutrons than 3DCRT

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