An irradiation treatment planning method for a patient supported by a patient support member which is arranged to be rotated about three orthogonal axes, the method comprising: rotating the patient support member about a first of the three orthogonal axes by a predetermined initial rotation angle; subsequent to said rotation about the first axis, imaging the patient; receiving information regarding treatment prescriptions of the patient; and responsive to said patient image, said received treatment prescription information and information regarding an allowable range of rotation of the patient support member about at least two of the three orthogonal axes, determining a first irradiation treatment plan, wherein in the event that said determined first irradiation treatment plan meets the patient treatment prescriptions, the method further comprises outputting said determined first irradiation treatment plan, and wherein in the event that said determined first irradiation treatment plan does not meet the patient treatment prescriptions, the method further comprises: responsive to said patient image, said received treatment prescription information and said allowable rotation range information, determining a plurality of rotation angles of said patient support member about the first axis; for each of said plurality of determined rotation angles which is different than the predetermined initial rotation angle, rotating said patient support member about the first axis by said respective determined rotation angle and imaging the patient; for each of said plurality of determined rotation angles, determining an irradiation treatment plan portion responsive to said respective patient image, the patient treatment prescriptions and said allowable rotation range information; and outputting each of said plurality of determined treatment plan portions. rotating the patient support member about a first of the three orthogonal axes by a predetermined initial rotation angle; subsequent to said rotation about the first axis, imaging the patient; receiving information regarding treatment prescriptions of the patient; and responsive to said patient image, said received treatment prescription information and information regarding an allowable range of rotation of the patient support member about at least two of the three orthogonal axes, determining a first irradiation treatment plan, wherein in the event that said determined first irradiation treatment plan meets the patient treatment prescriptions, the method further comprises outputting said determined first irradiation treatment plan, and wherein in the event that said determined first irradiation treatment plan does not meet the patient treatment prescriptions, the method further comprises: responsive to said patient image, said received treatment prescription information and said allowable rotation range information, determining a plurality of rotation angles of said patient support member about the first axis; for each of said plurality of determined rotation angles which is different than the predetermined initial rotation angle, rotating said patient support member about the first axis by said respective determined rotation angle and imaging the patient; for each of said plurality of determined rotation angles, determining an irradiation treatment plan portion responsive to said respective patient image, the patient treatment prescriptions and said allowable rotation range information; and outputting each of said plurality of determined treatment plan portions. responsive to said patient image, said received treatment prescription information and said allowable rotation range information, determining a plurality of rotation angles of said patient support member about the first axis; for each of said plurality of determined rotation angles which is different than the predetermined initial rotation angle, rotating said patient support member about the first axis by said respective determined rotation angle and imaging the patient; for each of said plurality of determined rotation angles, determining an irradiation treatment plan portion responsive to said respective patient image, the patient treatment prescriptions and said allowable rotation range information; and outputting each of said plurality of determined treatment plan portions.