A method for irradiating a planning target volume with charged particles includes delivering the charged particles to the planning target volume with a charged particle therapy system including a charged particle beam path and a gantry configured to rotate about the planning target volume and to direct the charged particle beam path; rotating the gantry, during an irradiation session, to a plurality of positions; during the rotation, irradiating the planning target volume with the charged particles at a first energy level at one or more of the plurality of positions.