Leakage radiation from secondary and tertiary collimators for a Medical Linear Accelerator

Radiation leakage is a critical factor which has to be considered before undergoing any treatment procedure. This work aims to evaluate the leakage of secondary and tertiary collimators which is a beam limiting device for various energies of Varian true beam medical linear accelerator. Measurements were taken with a 0.6cc farmer chamber at an isocentre for open beams at 24 different positions in which isocentre plane is perpendicular to the beam axis with secondary collimators closed. The transmission factors of collimators were calibrated for all the positions and average as well as maximum leakage was evaluated. The same was repeated for all the photon energies and for multi-leaf collimators (MLC) in which leakage values were acquired for different positions. (author)