A method and a device for regulating a therapeutic beam directed at an object are provided. The method includes displaying at least one multidimensional image data record encompassing at least one target area of the object. The method also includes determining the treatment beam dosage directed at the at least one target area, and recording and optionally visualizing an isoline or isosurface dependent on the treatment beam dosage in the at least one multidimensional image data record. The method includes adjusting the isoline or isosurface such that the isoline or isosurface approximates a contour of the target area as closely as possible or corresponds to the contour, and regulating the treatment beam dosage by evaluation of the adjusted isoline or isosurface.