1. A method for designating a region of interest of a subject from volume data of the subject through at least one of sole processing and dispersed processing performed by at least one computer, the volume data of the subject including coordinates of voxels and having three or more dimensions, the method comprising: designating a plurality of designation points from the coordinates of the voxels with the at least one computer; connecting the designation points to generate a curved surface including the designation points with the at least one computer; and designating the region of interest by adding a thickness to the curved surface with the at least one computer.