A method for manufacturing a shaping structure having a generally helical profile and configured to support electrodes for delivering electric energy into a cylindrical lumen of a patient. The method comprises providing a mandrel with a circular cylindrical shape and forming a first hole in the mandrel along the elongate axis, such that opposing ends of a bore of the first hole emerge at the proximal end and at the distal end; forming a second hole in the mandrel to extend from the curved surface to connect with the first hole; wrapping a metal wire around the mandrel; and inserting opposing ends of the metal wire into the second and the third hole respectively, and threading the opposing ends of the metal wire until they emerge from the opposing ends of the bore of the first hole; finally, heating the mandrel and the wire.