Inverse treatment planning for Gamma Knife radiosurgery

An inverse treatment planning system for Gamma Knife radiosurgery has been developed using nonlinear programming techniques. The system optimizes the shot sizes, locations, and weights for Gamma Knife treatments. In the patie nt's prescription, the user can specify both the maximum number of shots of radiation and a minimum isodose line that must surround the entire treatme nt volume. After satisfying all of the constraints included in the prescrip tion, the system maximizes the conformity of the dose distribution. This au tomated approach to treatment planning has been applied retrospectively to a series of patient cases, and each optimized plan has been compared to the corresponding manual plan produced by an experienced user. The results dem onstrate that this tool can often improve the tumor dose homogeneity while using fewer shots than were included in the original plan. Therefore, inver se treatment planning should improve both the quality and the efficiency of Gamma Knife treatments. (C) 2000 American Association of Physicists in Med icine. [S0094-2405(00)01412-7].