System, method, and computer program product to select a desired portion of a subject to receive a radiation dose, including: determining a plurality of Pareto points on a Pareto surface (PS); selecting a first reference point (p1) on a back side of an assumed Pareto surface (PS′) and first direction (q1) emerging therefrom towards PS′ from behind; selecting a first starting adjustment (x10) and iteratively developing forward a minimum criterion in steps until a final adjustment (x11) is reached that still is implementable in the radiation apparatus; stopping the forward development, thereby determining x11 represented by a final front point (y11) as a real Pareto point of PS′; and along q1, dismissing undetermined portions of the objective space in front of and behind y11 as not containing parts of the PS, and continuing with other remaining more determined portions that are assumed to each contain a part of PS′.