Abstract: An iterative method for determining a two—or—three-dimensional image on the basis of signals arising from X-ray tomography, comprises: segmenting the image by separating distinct materials respectively by level lines for 2D or level surfaces for 3D; and adapting the mesh, triangular for 2D or tetrahedral 3D, in which points are distributed in a homogeneous manner respectively over a level line for 2D or over a level surface for 3D, serving to formulate the progressively coarse triangular mesh for 2D or tetrahedral mesh for 3D, so that the number of distributed points depends respectively, for a line, on the ratio of the length of the line to the length of the minimum line from among the lines of the segmented image, or, for a surface, on the ratio of the area of the surface to the area of the minimum surface from among the surfaces of the segmented image.