4D DMLC leaf sequencing to minimize organ at risk dose in moving anatomy.

The most favorable treatment for moving body anatomy should aim at utilizing organ motion to minimize the dose to sensitive structures without compromising the dose delivered to the target. The solution of the problem of appropriate intensity redistribution over different phases of body motion is achievable in dynamic multileaf collimator (DMLC) intensity modulated radiation therapy delivery, due to the fact that multiple solutions are admissible for imposing the same intensity map over a moving target in this technique of irradiation. The realization of this type of delivery provides a treatment methodology that delivers treatment plans for moving patient anatomy that are superior to any treatments possible for static patient body anatomy. This paper is devoted to exploring this idea. To this end, a simple, though clinically realistic example is developed and presented that shows modified DMLC leaf motions that deliver a predetermined intensity to a moving target while reducing the dose delivered to organs at risk.