| Summary: | 碩士 === 慈濟科技大學 === 放射醫學科學研究所 === 107 === The tongue and groove design of the multi-leaf collimator (MLC) of the linear accelerator (LINAC) may result in the radiation leakage. In this study, the Varian TrueBeamTM phase space particle files were used to construct the Millennium 120 multi-leaf collimator module for Monte Carlo simulations of such tongue and groove effect. The simulations have been carried out in conditions of different energies, field sizes, depths, and two different LINAC modes, i.e., the flattening filter (FF) and the flattening filter free (FFF) modes. The leakages were also measured by the films for the specific conditions as used in the Monte Carlo simulations. The total average radiation leakage rates found by the Monte Carlo simulations and the measurements were 0.69% ± 0.04% and 1.60% ± 0.23% respectively. The leakage does not increase with energies. The average leakage increases with the filed sizes and depths. No significant differences in leakage rate of the tongue and groove effect were found between the FF and the FFF modes.
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