DMLC leaf-pair optimal control for mobile, deforming target.

Existing algorithms of dynamic control of independent pairs of leaves allow optimal DMLC delivery of IMRT to rigid targets translating parallel to leaf trajectories. However, in numerous cases of radiotherapy treatments simplifying assumptions of rigid-like motions of targets and surrounding tissues are clearly not satisfied. Therefore algorithms have to be developed that allow one to control MLC so that predetermined intensities are delivered to various points in targets that experience compression and expansion at the time of irradiation. Moreover, it is desirable for such algorithms to ensure that delivery of modulated intensity map will be done with minimal expense of monitor units. Derivation of the algorithm that optimizes the DMLC IMRT to mobile, deforming target is presented in this paper. [To illustrate the general algorithm two representative examples of DMLC IMRT delivery to deforming targets are presented in full detail.] Finally, similarities and differences between solutions for immobile targets, for moving, rigid targets and for moving, deforming targets are discussed.