A model for the control of multileaf collimator and related inverseplanning

A new approach for the inverse treatment planning in radiation therapy with the multileaf colli-mator (MLC) technique is presented. The application of the MLC-techniques requires an algorithm for the computation of the positions or velocities of leaves as a function of time such that the prescribed dose in the patient space is obtained. First the intensity distribution in the treatment space is determined applying some inverse treatment techniques. Then an MLC control algorithm which generates the determined intensity distribution is required. In the present paper a mathematical model is given which controls the MLC such that the intensity distribution is obtained under selected dose constraints. In addition an MLC control algorithm not requiring an intensity distribution as an intermediate step is expressed. The algorithm uses the MLC leaf positions and delivery times directly in inverse treatment planning. The method can easily be implemented to multiple static treatments ("step-and-shoot") but a modiication to dynamical MLC techniques is also straightforward.