"A medical device, in accordance with an embodiment of the invention, comprises a core element made at least partially of a shape-memory material. Shape-memory material is a material that can be formed into a particular shape, retain that shape during resting conditions (e.g., when the shaped material is in free space or when external forces applied to the shaped material are insufficient to substantially deform the shape), be deformed into a second shape upon subjecting the initial shape to a sufficiently strong external force, and revert substantially back to the initial shape once the external force is no longer applied. Examples of shape memory material include synthetic plastics, stainless steel, and superelastic, metallic alloys of nickel/titanium (commonly referred to as nitinol), copper, cobalt, vanadium, chromium, iron, or the like. In one embodiment, a first portion of the core element extends substantially longitudinally, and a second portion is wound to form a helical coil. The helical coil is adapted to taper from a larger diameter at a proximal end thereof to a smaller diameter at a distal end thereof, thereby resembling a helical cone shape.
"In one embodiment, a flat wire (with, for example, a square, rectangular, or other quadrilateral cross-section) substantially wraps the first and second portions of the core element. A distal end of the flat wire can be attached to the distal end of the helical coil, so as to maintain the relative orientation and position between the flat wire and the core element. In a further embodiment, a layer of polymeric material substantially covers the entire outer surface of the flat wire (i.e., the surface of the flat wire that contacts the walls of the anatomical lumen or catheter), including that portion of the flat wire that wraps both the first and second portions of the core element. In another embodiment, the polymeric layer covers a portion of the outer surface of the flat wire wrapping the second portion of the core element, while leaving the outer surface of the flat wire wrapping the first longitudinal portion of the core element uncovered. Alternatively, the polymeric layer covers the outer surface of the flat wire wrapped about the second portion of the core element and at least a portion of the first longitudinal section in the vicinity of the helical cone.
"In another embodiment, a wire element substantially wraps only the first longitudinal portion of the core element, and a sheath (of, for example, a polymeric material) covers the second, helical cone portion of the core element. The proximal end of the sheath can be attached to the distal end of the wire element, and the distal end of the sheath can be attached to the distal end of the second portion of the core element.
"In yet another embodiment, the curved, second portion of the core element is covered substantially by a polymeric material and the longitudinal section of the core element remains uncovered. In this embodiment, the core element is not covered by a wire element.
"In one embodiment, the polymeric material/layer is applied by spraying. For example, a polymeric material can be spray-coated onto the outer surface of the wire and/or directly onto the helical cone section of the core element. In another embodiment, the polymeric material can be a sheath that is heat-shrunk about the wire and/or the second portion of the core element. The polymeric sheath can be made of PTFE, EPTFE, ETFE or other suitable material that exhibits a light color capable of reflecting most of the laser energy used during a lithotripsy procedure and absorbing or dissipating the energy not reflected with no or minimal damage to the polymeric sheath at normal laser operating levels.
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