Vascular stent with composite structure for magnetic resonance imaging capabilities
View Patent ↗A stent is adapted to be implanted in a duct of a human body to maintain an open lumen at the implant site, and to allow viewing body tissue and fluids by magnetic resonance imaging (MRI) energy applied external to the body. The stent constitutes a metal scaffold. An electrical circuit resonant at the resonance frequency of the MRI energy is fabricated integral with the scaffold structure of the stent to promote viewing body properties within the lumen of the stent.
1. A stent, comprising:
a tubular structure; and
an electrically conductive layer spaced from the tubular structure by an electrically insulative layer to form a composite inductive capacitive circuit integrated on the tubular structure to function as an electrical inductance element and an electrical capacitive element, where the tubular structure defines coil portions formed in a predetermined pattern for the electrically insulative layer that pass between adjacent mask bars that are in an offset configuration relative each adjacent mask bar.
2. The stent of claim 1 , where the coil portions form a continuous coil along a length of the tubular structure, where ends of the coil portions are positioned adjacent each other to form the electrical capacitive element on the tubular structure.
3. The stent of claim 1 , wherein the electrically insulative layer comprises an oxide.
4. The stent of claim 3 , wherein the oxide is niobium oxide or niobium-zirconium oxide.
5. The stent of claim 1 , wherein the tubular structure comprises a metallic element, and the electrically insulative layer comprises the metallic element.
6. The stent of claim 1 , wherein the electrically insulative layer has a thickness less than about one micron.
7. The stent of claim 1 , wherein the electrically insulative layer contacts the electrically conductive layer.
8. The stent of claim 1 , wherein the electrically conductive layer includes longitudinal elements with an interruption at a central point of each longitudinal element, where corresponding ends of the longitudinal elements are connected together by a respective transverse circumferential connecting strip on the tubular structure to form the composite inductive capacitive circuit.
9. The stent of claim 1 , wherein the tubular structure has a thickness greater than a thickness of the electrically conductive layer.
10. The stent of claim 1 , wherein the electrically conductive layer has a thickness less than about ten microns.
11. The stent of claim 1 , wherein the electrically conductive layer comprises niobium.
12. The stent of claim 1 , wherein the tubular structure comprises niobium.
13. The stent of claim 12 , wherein the tubular structure comprises an alloy comprising niobium.
14. The stent of claim 13 , wherein the alloy further comprises zirconium, titanium, or tantalum.
15. The stent of claim 1 , wherein the tubular structure is non-ferromagnetic.
16. The stent of claim 15 , wherein the tubular structure is diamagnetic or paramagnetic.