This is an implantable vasoocclusive device. It is constructed of a primary helically wound coil, which primary coil is further wound into secondary shapes which are at least partially substantially conical. Other portions of the secondary shape may have sections of constant diameter or of other conical...http://www.google.es/patents/US5649949?utm_source=gb-gplus-sharePatente US5649949 - Variable cross-section conical vasoocclusive coils
