Comparative study of treatment dose plans after the refinement of Leksell Gamma Knife single-beam dose profiles.

We investigated the amplification of discrepancy when using multiple shots of the same collimator size helmet, by comparing dose plans in the Leksell GammaPlan employing the default single-beam dose profiles and the Monte Carlo generated single-beam profiles. Four collimator helmets were studied. The results show that the largest amplification of discrepancy with multiple shots was found with the 8 mm collimator because of the largest discrepancy of its single-beam dose profile. The amplification of discrepancy is significant when tumor volumes increase but insignificant when the tumor volumes are in an elongated shape. Using close shot overlapping strategy (i.e., more shots close packed together) shows no observable increase in the amplification of discrepancy. For the best quality of Leksell Gamma Knife radiosurgery, it is suggested that the single-beam dose profiles should be refined, especially the 8 mm collimator, to prevent error amplification when using multiple collimator shots.