DMLC leaf-pair optimal control of IMRT delivery for a moving rigid target.

In dynamic multileaf collimation (DMLC), pairs of servo-controlled leaves sweep across the target to deliver the modulated radiation intensity map while the beam is on continuously. The mathematical model for dynamic, optimal control of a single leaf pair has been developed for the case of a rigid target, translating parallel to the leaf trajectories. This mathematical model ensures delivery of the modulated intensity map while minimizing beam-on time. Numerical solutions of the model are presented here for optimal IMRT delivery for stationary and oscillating targets, together with a discussion of the results. Comparisons between solutions for stationary and mobile targets, as well as comparisons between optimal and suboptimal algorithms, are provided. These comparisons allow us to estimate potential gains in the effectiveness of DMLC IMRT delivery when it is based on optimal algorithms.