Accelerated IMRT plan optimization using the adaptive clustering method

A major problem of intensity modulated radiation therapy (IMRT) planning is the high numerical complexity of the corresponding optimization problems. This is mainly a consequence of the volume discretization into a very large number of volume elements. Many approaches simplify the volume discretization in order to reduce the computation times. However, most of them do the simplification in a non-adaptive way prior to the plan computations and are thus of a heuristic type. The adaptive clustering method overcomes this drawback as follows. The dose mapping and the planning structures first undergo a preprocessing. The obtained output then serves as a ‘construction kit’ for the formation of volume discretizations that are individually adapted during each plan computation. This method is highly flexible, since it is widely independent of the type of plan parameters, can be applied to a very large class of functions for dose evaluation, and is not restricted to the use of a particular numerical solver.