A model for the control of a multileaf collimator inradiation therapy treatment planning

Abstract

A new approach for inverse treatment planning in radiationtherapy with the multileaf collimator (MLC) technique ispresented. The application of the MLC technique requires analgorithm for the computation of the positions or velocities ofleaves as a function of time such that the prescribed dose inthe patient space is obtained. The conventional method is to first determine the intensity distribution in the treatmentspace by applying some inverse treatment techniques. Then anMLC control algorithm which generates the determined intensitydistribution is required. In this paper an MLC controlalgorithm not requiring an intensity distribution as anintermediate step is expressed. The algorithm uses the MLC leafpositions and delivery times (in multiple static treatments)directly in inverse treatment planning. The method isimplemented to multiple static treatments but a modification todynamical MLC techniques is possible. The numerical test isbased on the search for a feasible solution but also theoptimization (object function) based approach is formulated. Therelated feasible problem consists of a high-dimensional system ofalgebraic (in-) equations. It is solved by an iterative row actionprojection method. The applied algorithm is well suited andcomputationally robust for high-dimensional feasible problems.