The invention designs a segmented short-arc VMAT plan, modified from the original VMAT plan, to fit the breath-hold interval. The modified VMAT of the invention has the advantages of its applicability to different planning systems for variously long arcs and its preprogrammed arc segmentation for summated dose consistency. The present invention provides a method and a system for use in administering radiation therapy to patients using a radiotherapeutic apparatus with gantry rotation, and also meets the requirements for dose planning and accurate delivery, as well as coordinates patients breath-hold level.
