a patient's vascular system to occlude a Patent Ductus Arteriosus; FIGS. 9A and 9B are a side view and an end view, respectively, of a medical device in accordance with yet another embodiment of the invention; FIG. 10A is a side view of one molding element suitable for forming the invention of FIGS. 9A and 9B; FIG. 10B is a cross-sectional view of another molding element suitable for forming the