A multi-phase radiation therapy treatment method is provided that includes computational software to simultaneously optimize radiation plans for each phase of delivery. A specific realization of multi-phase therapy, dual gating, is described where the first radiation therapy treatment plan provides treatment during an inhale phase of a patient breathing cycle and the second radiation therapy treatment plan provides treatment during an exhale phase of the patient breathing cycle. Using a radiation therapy machine, the first radiation therapy treatment plan is delivered during the inhale phase and the second radiation therapy treatment plan is delivered during the exhale phase of the patient breathing cycle. An associated imaging method is provided for gated volumetric image guidance at multiple different phases in a single imaging acquisition.
