This study aims to investigate and evaluate the secondary photons characterizations under flattening filter (FF) for high radiotherapy quality in terms of fluence, energy fluence, energy fluence distribution, spectral distribution and angular spread distribution of secondary photons, which are mainly coming from primary collimator originated in the whole Linac head. However, the flattening filter illuminates the photons of low energy. After this component, the secondary photons of low energy are coming from flattening filter and secondary collimators that contaminate the dosimetry for deep tumor treatment.
Fluence profile, energy profile and angular spread of secondary photons decreased with FF volume reduction percent but energy distribution and spectral distribution kept almost constant with FF volume reduction. The FF volume reduction allows reducing the secondary photons emergent from FF in number and in energy and it permits to increase the radiotherapy efficiency by decreasing the photons contamination when the cancer is treating.