A method and apparatus is presented for optimizing a treatment plan for irradiation therapy. The method includes defining a single objective function based on a plurality of objective functions that are each associated with a plurality of tissue types within a subject, upper and lower bounds for each objective function and a plurality of apertures. The method also includes determining a radiation dose delivered to voxels of each tissue type based on minimizing the single objective function based on the plurality of apertures with initial values at each angle. The method also includes delivering a beam of radiation with controlled intensity and beam cross-sectional shape at each angle based on the plurality of apertures.