Abstract
The tongue-and-groove geometric design on multileaf collimator is to reduce interleaf leakage between adjacent leaves. Due to this design, a lower dose distribution will be produced when adjacent or opposed leaf pairs moving at overlapping tract during IMRT delivery. From previous publications show that 15-28% under dose due to tongue-and-groove effect. We use Monte Carlo user code BEAM/EGS4 to simulate the multileaf collimator of ELEKTA SLi accelerator and to analysis the characteristics of tongue-and-groove effect. The under dose effect exists at every depth and the worst under dose is as high as 50% of maximum dose. The simulation results indicate the effect decrease strongly with increasing depth. Another important factor is total beam numbers which improve the under dose to 2% for depth equal to 25cm. The simulation results could be integrated into the IMRT treatment planning system and helpful for uncertainty evaluation.Keyword : tongue-and-groove、IMRT、Monte Carlo