US20050049481A1 - Electromagnetic radiation transparent device and method of making thereof - Google Patents

Abstract

A medical device includes a pattern of electrically conductive material. The pattern of electrically conductive material has an anti-antenna geometrical shape such that the anti-antenna geometrical shape substantially prevents the medical device from creating an imaging artifact and/or substantially allows imaging of a volume within the medical device. The pattern may be formed by multiple “figure-8” shaped electrical conductors, multiple “figure-8” emulating electrical conductors, multiple sine-wave-like shaped electrical conductors, multiple zig-zag patterned electrical conductors, by multiple electrical conductors, each having sequential conductive loops, and/or a single conductor weaved into a loop mesh. The electrically conductive material may be titanium, tantalum, nitinol, stainless steel, and/or NbZr.

Description

PRIORITY INFORMATION
• This application claims priority from U.S. Provisional Patent Application, Ser. No. 60/497,591, filed on Aug. 25, 2003. The entire content of U.S. Provisional Patent Application, Ser. No. 60/497,591 is hereby incorporated by reference.
FIELD OF THE PRESENT INVENTION
• The present invention is directed to stent designs, deployment devices for stents, and the fabrications thereof More particularly, the present invention is directed to stents which produce little or no magnetic resonance image artifacts and the fabrications thereof.
BACKGROUND OF THE PRESENT INVENTION
• The use of stents as a medical corrective and preventive device is well known.
• For example, U.S. Pat. No. 5,133,732 discloses that a stent can be implanted into a body vessel. The stent is a cylindrical body formed by a coiled generally continuous wire with a deformable zig-zag structure. The stent is further provided with means for preventing the stent body from stretching along its longitudinal axis. This stent is especially useful when implanting very long stents by means of balloon expansion. The entire content of U.S. Pat. No. 5,133,732 is hereby incorporated by reference.
• In another example, U.S. Pat. No. 5,507,767 discloses that a self-expanding endovascular stent is formed of stainless steel wire which is bent into an elongated zigzag pattern. The zigzag pattern has a plurality of substantially straight wire sections of various lengths separating a plurality of bends. The zigzag pattern is helically wound about a central axis to define a tubular shape such that a majority of the bends is disposed in a helix. Adjacent bends in the helix are interconnected with a filament. The entire content of U.S. Pat. No. 5,507,767 is hereby incorporated by reference.
• Magnetic resonance imaging (“MRI”) has been developed as an imaging technique adapted to obtain both images of anatomical features of human patients as well as some aspects of the functional activities and characteristics of biological tissue. These images have medical diagnostic value in determining the state of the health of the tissue examined. Unlike the situation with fluoroscopic imaging, a patient undergoing magnetic resonance imaging procedure may remain in the active imaging system for a significant amount of time, e.g. a half-hour or more, without suffering any adverse effects.
• In an MRI process, a patient is typically aligned to place the portion of the patient's anatomy to be examined in the imaging volume of the MRI apparatus. Such an MRI apparatus typically comprises a primary electromagnet for supplying a constant magnetic field (B₀) which, by convention, is along the z-axis and is substantially homogeneous over the imaging volume and secondary electromagnets that can provide linear magnetic field gradients along each of three principal Cartesian axes in space (generally x, y, and z, or x₁, x₂and x₃, respectively). The MRI apparatus also comprises one or more RF (radio frequency) coils which provide excitation and detection of the MRI induced signals in the patient's body.
• The gradient fields are switched ON and OFF at different rates depending on the MRI scan sequence used. In some cases, this may result in a changing magnetic field on the order of dB/dt=50 T/s. The frequency that a gradient field may be turned ON can be between 200 Hz to about 300 kHz.
• Uniformity in the static magnetic B₀field over the imaging volume is important for image clarity. When the field is not uniform, image distortions called “image artifacts” result. Additionally, if the gradient fields deviate significantly from their ideal linear character over the imaging volume, image artifacts develop.
• Medical devices which are placed into a patient's body can cause the magnetic fields of the MRI system to deviate from their preferred characteristics for clear imaging. If a medical device comprises metallic components (such as iron), image artifacts result due to the metal's magnetic susceptibility properties distorting the MRI system applied magnetic fields. These are known as susceptibility artifacts. Additionally, if the medical device comprises conductive components, eddy currents develop in these conductive components when the MRI system's oscillating magnetic fields are applied. The eddy currents distort the net magnetic fields in the imaging volume, thereby providing another source for MRI imaging artifacts.
• After a stent is inserted into a patient, it is often desirable, over time, to determine if the stent is performing as expected. In the case, for example, of deploying a stent to correct a stenosis problem, it is desirable to determine if there is any indication of restenosis. This, as well as for other medical situations, requires obtaining images of the volume inside the stent. Due to the image artifact problems, described above, inherent in metallic, conductive stents, it is not possible to obtain clear MR images of the interior volume of the stents.
• Attempts have been made to overcome these problems. The article, “Artifact-Free In-Stent Lumen Visualization by Standard Magnetic Resonance Angiography Using a New Metallic Magnetic Resonance Imaging Stent” by Arno Buecker, et al.,Circulation, Apr. 16, 2002, pp. 1772-1775, discloses that a handmade stent can enhance the imaging ability of the stent's lumen. However, the handmade prototypes lacked a radial force comparable to standard stainless steel stents. Additionally, the article discloses the use of a contrasting agent to enhance visualization of the stent lumen.
• The article “MR Imaging of Vascular Stents: Effects of Susceptibility, Flow, and Radiofrequency Eddy Currents” by Lambertus W. Bartels, et al., published inJournal of Vascular and Interventional Radiology, volume 12, Number 3, March 2001, pp. 365-371, describes the various image artifacts that prevent clear imaging of stent lumen.
• The article “Improved Lumen Visualization in Metallic Vascular Implants by Reducing RF Artifacts” by Lambertus W. Bartels, et al., published inMagnetic Resonance in Medicine, 74:171-180 (2002), describes attempts at imaging metallic stents lumen by using contrast agents and by increasing the power deposited into the patient during the MRI procedure. The power deposited into the patient body, measured as the Specific Absorption Rate (SAR) can be harmful to the patient undergoing an MRI if set too high. In addition to the higher power deposited into the patient, the article discloses that adjustments in the image reconstruction process need to be implemented.
• U.S. Patent Application Publication US 2002/0188345 A1, published Dec. 12, 2002, discloses an expandable metallic stent that has discontinuities of non-conducting material. These eliminate electrically conducting paths in the stent rings and cells. This makes the stent easier to image with magnetic resonance imaging (MRI). The entire content of U.S. Patent Application Publication US 2002/0188345 A1 is hereby incorporated by reference.
• WIPO PCT publication WO 03/015662 A1 discloses that a metallic endoprosthesis causes no significant artifacts on images taken by magnetic resonance tomography (MRT), as a result of the combination of the production materials with a special design, which permits an evaluation of the externally adjacent region and the lumen of the endoprosthesis by means of MRT.
• Although the above-described stents can be used to help a patient, these stents still cause magnetic resonance imaging artifacts. Moreover, the above-described stents prevent the imaging of the volume within the stent during magnetic resonance imaging.
• Therefore, it is desirable to provide a stent which produces little to no magnetic resonance imaging artifacts. Moreover, it is desirable to provide a stent that allows the imaging of the volume within the stent. Furthermore, it is desirable to provide a stent which produces little to no magnetic resonance imaging artifacts and/or allows the imaging of the volume within the stent.
SUMMARY OF THE PRESENT INVENTION
• One aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material. The pattern of electrically conductive material has an anti-antenna geometrical shape such that the anti-antenna geometrical shape substantially prevents the medical stent from creating an imaging artifact.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material. The pattern of electrically conductive material has an anti-antenna geometrical shape such that the anti-antenna geometrical shape substantially allows imaging of a volume within the stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material. The pattern of electrically conductive material has an anti-antenna geometrical shape such that the anti-antenna geometrical shape substantially prevents the medical stent from creating an imaging artifact and substantially allows imaging of a volume within the stent.
• Another aspect of the present invention is an electrically conductive structure. The electrically conductive structure includes a pattern of electrically conductive material. The pattern of electrically conductive material has an anti-antenna geometrical shape such that the anti-antenna geometrical shape substantially prevents creation of an imaging artifact by the electrically conductive structure.
• Another aspect of the present invention is a medical device. The medical device includes a pattern of electrically conductive material. The pattern of electrically conductive material has an anti-antenna geometrical shape such that the anti-antenna geometrical shape substantially prevents creation of an imaging artifact by the medical device.
• Another aspect of the present invention is an electrically conductive structure. The electrically conductive structure includes a pattern of electrically conductive material. The pattern of electrically conductive material has an anti-antenna geometrical shape such that the anti-antenna geometrical shape substantially allows imaging of a volume within the electrically conductive structure.
• Another aspect of the present invention is an electrically conductive structure. The electrically conductive structure includes a pattern of electrically conductive material. The pattern of electrically conductive material has an anti-antenna geometrical shape such that the anti-antenna geometrical shape substantially prevents creation of an imaging artifact by the medical device and substantially allows imaging of a volume within the electrically conductive structure.
• Another aspect of the present invention is a medical device. The medical device includes a pattern of electrically conductive material. The pattern of electrically conductive material has an anti-antenna geometrical shape such that the anti-antenna geometrical shape substantially allows imaging of a volume within the medical device.
• Another aspect of the present invention is a medical device. The medical device includes a pattern of electrically conductive material. The pattern of electrically conductive material has an anti-antenna geometrical shape such that the anti-antenna geometrical shape substantially prevents creation of an imaging artifact by the medical device and substantially allows imaging of a volume within the medical device.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially prevents the medical stent from creating an imaging artifact.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially allows imaging of a volume within the stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially prevents the medical stent from creating an imaging artifact and substantially allows imaging of a volume within the stent.
• Another aspect of the present invention is an electrically conductive structure. The electrically conductive structure includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially prevents creation of an imaging artifact by the electrically conductive structure.
• Another aspect of the present invention is a medical device. The medical device includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially prevents creation of an imaging artifact by the medical device.
• Another aspect of the present invention is an electrically conductive structure. The electrically conductive structure includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially allows imaging of a volume within the electrically conductive structure.
• Another aspect of the present invention is an electrically conductive structure. The electrically conductive structure includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially prevents creation of an imaging artifact by the medical device and substantially allows imaging of a volume within the electrically conductive structure.
• Another aspect of the present invention is a medical device. The medical device includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially allows imaging of a volume within the medical device.
• Another aspect of the present invention is a medical device. The medical device includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially prevents creation of an imaging artifact by the medical device and substantially allows imaging of a volume within the medical device.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially prevents the medical stent from creating an imaging artifact. The electrically conductive material is shaped so as to be expandable, the expansion of the electrically conductive material causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially allows imaging of a volume within the stent. The electrically conductive material is shaped so as to be expandable, the expansion of the electrically conductive material causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially prevents the medical stent from creating an imaging artifact and substantially allows imaging of a volume within the stent. The electrically conductive material is shaped so as to be expandable, the expansion of the electrically conductive material causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially prevents the medical stent from creating an imaging artifact. The electrically conductive material is shaped so as to be expandable upon application of heat, the expansion of the electrically conductive material causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially allows imaging of a volume within the stent. The electrically conductive material is shaped so as to be expandable upon application of heat, the expansion of the electrically conductive material causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material. The pattern of electrically conductive material substantially prevents the medical stent from creating an imaging artifact and substantially allows imaging of a volume within the stent. The electrically conductive material is shaped so as to be expandable upon application of heat, the expansion of the electrically conductive material causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material and a track-and-lock mechanism having a shape substantially matching the shape of the electrically conductive material so as to substantially prevent the electrically conductive material from moving in such a way as to reduce the radius of the medical stent. The pattern of electrically conductive material substantially prevents the medical stent from creating an imaging artifact. The electrically conductive material is shaped so as to be expandable, the expansion of the electrically conductive material causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material and a track-and-lock mechanism having a shape substantially matching the shape of the electrically conductive material so as to substantially prevent the electrically conductive material from moving in such a way as to reduce the radius of the medical stent. The pattern of electrically conductive material substantially allows imaging of a volume within the stent. The electrically conductive material is shaped so as to be expandable, the expansion of the electrically conductive material causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material and a track-and-lock mechanism having a shape substantially matching the shape of the electrically conductive material so as to substantially prevent the electrically conductive material from moving in such a way as to reduce the radius of the medical stent. The pattern of electrically conductive material substantially prevents the medical stent from creating an imaging artifact and substantially allows imaging of a volume within the stent. The electrically conductive material is shaped so as to be expandable, the expansion of the electrically conductive material causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material and a track-and-lock mechanism having a shape substantially matching the shape of the electrically conductive material so as to allow the electrically conductive material to move in a single direction. The pattern of electrically conductive material substantially prevents the medical stent from creating an imaging artifact. The electrically conductive material is shaped so as to be expandable, the expansion of the electrically conductive material causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material and a track-and-lock mechanism having a shape substantially matching the shape of the electrically conductive material so as to allow the electrically conductive material to move in a single direction. The pattern of electrically conductive material substantially allows imaging of a volume within the stent. The electrically conductive material is shaped so as to be expandable, the expansion of the electrically conductive material causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a pattern of electrically conductive material and a track-and-lock mechanism having a shape substantially matching the shape of the electrically conductive material so as to allow the electrically conductive material to move in a single direction. The pattern of electrically conductive material substantially prevents the medical stent from creating an imaging artifact and substantially allows imaging of a volume within the stent. The electrically conductive material is shaped so as to be expandable, the expansion of the electrically conductive material causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a plurality of links, each link being connected together so as to form a cylindrical shaped medical stent, each link being shaped so as to be expandable, the expansion of the links causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a plurality of links, each link being connected together so as to form a cylindrical shaped medical stent, each link being shaped so as to be expandable upon application of heat, the expansion of the links causing an increase in a radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a plurality of links, each link being connected together so as to form a cylindrical shaped medical stent, each link being shaped so as to be expandable, the expansion of the links causing an increase in a radius of the medical stent; and a track-and-lock mechanism having a shape substantially matching the shape of the links so as to substantially prevent the links from moving in such a way as to reduce the radius of the medical stent.
• Another aspect of the present invention is a medical stent. The medical stent includes a plurality of links, each link being connected together so as to form a cylindrical shaped medical stent, each link being shaped so as to be expandable upon application of heat, the expansion of the links causing an increase in a radius of the medical stent; and a track-and-lock mechanism having a shape substantially matching the shape of the links so as to allow the links to move in a single direction.
• Another aspect of the present invention is a method of fabricating a medical stent. The method cuts a first cylinder of electrically conductive material so as to create a first pattern of conductive mesh strands having a plurality of nodes; cuts a second cylinder of electrically conductive material so as to create a first pattern of conductive mesh strands having a plurality of nodes; positions the first cylinder into a volume of the second cylinder and positioning the first cylinder with respect to the second cylinder such the nodes of the first cylinder are close to the nodes of the second cylinder without the nodes of the first cylinder touching the nodes of the second cylinder; and applies a non-conductive binding material to adjacent nodes of the two cylinders.
• Another aspect of the present invention is a method of fabricating a medical stent. The method cuts a first cylinder of electrically conductive material so as to create a first pattern of conductive mesh strands having a plurality of nodes; cuts a second cylinder of electrically conductive material so as to create a first pattern of conductive mesh strands having a plurality of nodes; positions the first cylinder into a volume of the second cylinder and positioning the first cylinder with respect to the second cylinder such the nodes of the first cylinder are close to the nodes of the second cylinder without the nodes of the first cylinder touching the nodes of the second cylinder; positions a third cylinder of a non-conductive binding material between the first and second cylinders; and applies heat to the adjacent nodes of the first and second cylinders to cause the non-conductive binding material to bind the adjacent nodes together.
• Another aspect of the present invention is a method of fabricating a medical stent. The method produces a web of conductive strands wherein at all the cross-over points, a non-conductive material is applied to hold the cross-over point strands in place and to electrically isolate the conductive strands from one another; cuts a portion of the web to produce a sheet of conductive strands; forms the sheet of conductive strands into a cylinder shape; and attaches ends of sheet together to hold the cylinder shape in place.
BRIEF DESCRIPTION OF THE DRAWINGS
• The present invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating a preferred embodiment and are not to be construed as limiting the present invention, wherein:
• FIG. 1 is a schematic illustration of two conductive loops in a changing magnetic field;
• FIG. 2 is a schematic illustration of a conductor in a “figure-8” configuration in a changing magnetic field;
• FIG. 3 is an illustration of one stent embodiment according to the concepts of the present invention;
• FIG. 4 is an illustration of another stent embodiment according to the concepts of the present invention;
• FIG. 5 is an illustration of another stent embodiment according to the concepts of the present invention;
• FIG. 6 is an illustration of another stent embodiment according to the concepts of the present invention;
• FIG. 7 illustrates a curved stent mesh embodiment according to the concepts of the present invention;
• FIGS. 8 and 9 illustrate a stent mesh by a “Z”-like shape strand according to the concepts of the present invention;
• FIG. 10 illustrates a stent mesh embodiment according to the concepts of the present invention;
• FIG. 11 illustrates a cross-over node in a stent mesh according to the concepts of the present invention;
• FIG. 12 illustrates another cross-over node in a stent mesh according to the concepts of the present invention;
• FIG. 13 illustrates another stent embodiment according to the concepts of the present invention;
• FIG. 14 illustrates a stent within a body which is heated by application of external RF energy;
• FIG. 15 is a cross sectional view of a coated stent according to the concepts of the present invention;
• FIGS. 16 through 21 illustrate various steps in the creation of a medical stent according to the concepts of the present invention;
• FIGS. 22 through 24 illustrate the use of a planar conductive weave sheet material from which a stent is formed according to the concepts of the present invention; and
• FIGS. 25 and 26 illustrate a locking mechanism for an expandable stent according to the concepts of the present invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
• The present invention will be described in connection with preferred embodiments; however, it will be understood that there is no intent to limit the present invention to the embodiments described herein. On the contrary, the intent is to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the present invention, as defined by the appended claims.
• For a general understanding of the present invention, reference is made to the drawings. In the drawings, like reference have been used throughout to designate identical or equivalent elements. It is also noted that the various drawings illustrating the present invention are not drawn to scale and that certain regions have been purposely drawn disproportionately so that the features and concepts of the present invention could be properly illustrated.
• FIG. 1 is a schematic illustration of inducedcurrents110 and112 in twoconductive rings102 and104, respectively, when theconductive rings102 &104 are placed in an environment in which there is an oscillatingmagnetic field106. At an instant in time, as illustrated inFIG. 1, bothcurrents110 &112 travel in a clockwise direction. But as the magnetic field oscillates, the direction of thesecurrents110 &112 will diminish to zero and then begin to circulate in a counter-clockwise direction (not shown.)
• FIG. 2 illustrates when theconductive rings102 &104 have been electrically joined together to form a single “figure-8” shaped or emulatingconductor120. The twolobes126 &128 of the “figure-8” shaped or emulatingconductor120 have equal planar areas. When placed in changingmagnetic field122 such that the flux of themagnetic field122 passes through thelobes126 &128, no net current will be induced in the “figure-8” shaped or emulatingconductor120. The “figure-8” shaped or emulatingconductor120 is electrically insulated at thecross-over point124.
• FIG. 3 illustrates a portion of amedical stent130, according to the concepts of the present invention. The illustratedmedical stent130 includes multiple “figure-8” shaped or emulatingconductors132,134,136 &138. The “figure-8” shaped or emulatingconductors132,134,136 &138 are electrically insulated at the cross-over points131. The cross-over points131 may also provide mechanical support for the “figure-8” shaped or emulatingconductors132,134,136 &138
• The “figure-8” shaped or emulatingconductors132,134,136 &138 are fastened together bynon-conductive connectors140. Theseconnectors140 may be constructed of Teflon®, Tefzel®, a nonconductive polymer, silicon, or other nonconductive material. The “figure-8” shaped or emulatingconductors132,134,136 &138 may be, for example, tantalum, nitinol, copper, or other conductive material or conductive composite material, which has a low magnetic susceptibility.
• The “figure-8” shaped or emulating conductors realize immunity from the electromagnetic interference or insult. In other words, each “figure-8” shaped or emulating conductor has an anti-antenna geometrical shape such that the anti-antenna geometrical shape prevents the medical stent from creating an imaging artifact and/or allows the imaging of the volume within the stent.
• FIG. 4 illustrates a portion of amedical stent160, according to the concepts of the present invention. The illustratedmedical stent160 includesconductors162 &164 having sequential conductive loops to form the cylindrical surface of themedical stent160. The sequential conductive loops form two or more sequential “figure-8” shaped or emulating conductive loop pairs wherein each sequentially loopedconductor162 &164 contains an even number of loops.
• Atcrossover point168, theconductor164 is electrically isolated by aninsulation member165 to prevent short circuiting the overall loop sequence. Atcrossover point169, theconductor162 is electrically isolated by aninsulation member167 to prevent short circuiting the overall loop sequence. Theinsulation members165 and167, at the crossover points168 &169, can also provide mechanical support forconductors162 &164 so that the shape is maintained.
• The sequentially loopedconductors162 &164 are fastened to each other usingnon-conductive material166.Material166 also provides means for securing the sequentially loopedconductor162 &164 from slipping through thefasteners166. Additional sequentially looped conductors (not shown) are added to complete the stent construction.
• The sequentially looped conductors realize immunity from the electromagnetic interference or insult. In other words, each sequentially looped conductor has an anti-antenna geometrical shape such that the anti-antenna geometrical shape prevents the medical stent from creating an imaging artifact and/or allows the imaging of the volume within the stent.
• FIG. 5 illustrates a portion of amedical stent170, according to the concepts of the present invention. The illustratedmedical stent170 includes asingle conductor172 weaved into a loop mesh to define the stent cylinder. The weave, for example, beginning at174, traces down the length of the to-be-constructed stent cylinder170 and then back up the cylinder length to define an even number of loops. The pattern formed by the weave may be sinusoidal, “Z” shaped, zig-zag shaped, or sawtooth shaped or other such pattern that traverses back and forth with respect to a direction that is perpendicular to the progressive direction of travel of the trace. This pattern forms two or more runs of two or more sequential “figure-8” shaped or emulating conductive loop pairs wherein each run of two or more sequential “figure-8” shaped or emulating conductive loop pairs contains an even number of loops.
• Continuing to follow the weave pattern, theconductor172 continues to weave down and up the length of the cylinder to thepoint176. To complete the stent, the weave continues in a like fashion around the circumference of the yet to-be-defined cylinder stent170.
• At eachintra-run cross-over point178, anonconductive material179 is used to electrically insulate theconductor172 from itself Additionally, thenonconductive material179 secures the crossed-over conductor, along a run, from deforming or slipping or otherwise changing the intra-run cross-over points.
• At eachinter-run cross-over point175, anonconductive material177 is used to electrically insulate theconductor172 from itself. Additionally, thenonconductive material177 secures the crossed-over conductor, between runs, from deforming or slipping or otherwise changing the inter-run cross-over points.
• The weave pattern of the conductor realizes immunity from the electromagnetic interference or insult. In other words, the weave pattern has an anti-antenna geometrical shape such that the anti-antenna geometrical shape prevents the medical stent from creating an imaging artifact and/or allows the imaging of the volume within the stent.
• FIG. 6 illustrates a portion of a cylinder shapedstent190 being constructed from a singleconductive material192 in a weave pattern. In this case, the conductor completes a circumferential sine-wave-like pattern rather than the longitudinal sine-wave-like pattern shown inFIG. 5.
• It is noted that the circumferential pattern formed by the weave may also be sawtooth or other such pattern that traverses back and forth with respect to a direction that is perpendicular to the progressive direction of travel of the trace.
• At intra-run cross-over points194 &198,nonconductive materials191 &193 are used to electrically insulate theconductive material192 from itself Additionally, thenonconductive materials191 &193 secure the crossed-overconductive material192, along a run, from deforming or slipping or otherwise changing the intra-run cross-over points.
• At eachinter-run cross-over point196, anonconductive material195 is used to electrically insulate theconductive material192 from itself Additionally, thenonconductive material195 secures the crossed-overconductive material192, between runs, from deforming or slipping or otherwise changing the inter-run cross-over points.
• The circumferential pattern realizes immunity from the electromagnetic interference or insult. In other words, the circumferential pattern has an anti-antenna geometrical shape such that the anti-antenna geometrical shape prevents the medical stent from creating an imaging artifact and/or allows the imaging of the volume within the stent.
• FIGS. 7-9 illustrate how the curved segments of the sine-wave like shape of the weaves mentioned inFIGS. 3, 4,5, and6 can be replaced by “Z” shaped, zig-zag shaped, or sawtooth shaped segments.
• FIG. 7 shows a typical cross-over point of a stent weave.Conductors200 and202 (or a single conductor) of a stent weave are fastened together by anon-conductive material201 which electrically insulates theconductors200 and202 (or a single conductor) from each other. It is noted thatconductors200 and202 are continuous, not discontinuous, throughnon-conductive material201.
• FIG. 8 shows one possible alternative to thecurved weave segments200 and202 ofFIG. 7. InFIG. 8, the conductive segments have a “Z” shaped, zig-zag shaped, or sawtooth shaped. Theconductive segments204 and206 do not cross over each other. Theconductive segments204 and206 are fastened to each other bymaterial208 which electrically isolatesconductive segments204 and206 from each other.
• When the stent is to be positioned and expanded in the body, the “Z” shaped segments ofconductive segments204 and206 straighten out to increase the overall diameter of the cylinder defined by the stent. This is shown inFIG. 9 wherein theconductive segments204 and206 have been straightened, thus increasing their span length and the overall diameter of the cylinder defined by the stent.
• FIG. 10 shows a conductive cylindermedical stent220 mesh comprising manyconductive strands221 andjunctions222. In this case, the conductors complete a sine-wave-like pattern. The pattern formed by the conductors may be circumferential or longitudinal. It is noted that the pattern formed by the conductors may also be “Z” shaped, zig-zag shaped, or sawtooth shaped or other such pattern that traverses back and forth with respect to a direction that is perpendicular to the progressive direction of travel of the trace.
• The pattern formed by the conductors realizes immunity from the electromagnetic interference or insult. In other words, the pattern formed by the conductors has an anti-antenna geometrical shape such that the anti-antenna geometrical shape prevents the medical stent from creating an imaging artifact and/or allows the imaging of the volume within the stent.
• FIG. 11 illustrates an expanded view of ajunction222, according to the concepts of the present invention. Thejunction222 includes fourconductive strands224,226,228 &230 fastened together and electrically isolated from one another by thenon-conductive material234.Small holes225,227,229 &231 are optionally fabricated into the ends of theconductive strands224,226,228 &230 so that thefastening material234 may be shaped to include protrusions to securely fasten to thestrands224,226,228 &230 with no possibility of any of the strands slipping out of thematerial234.
• It is noted that, although not shown, certain ends of theconductive strands224,226,228 &230 may be electrically connected to each other to form the proper loop circuitry needed to produce the opposing currents in the stent so that a net zero current is realized. For example,conductive strand224 may be electrically connected toconductive strand230, whileconductive strand226 may be electrically connected toconductive strand228. On the other hand, for another example,conductive strand224 may be electrically connected toconductive strand226, whileconductive strand230 may be electrically connected toconductive strand228.
• The connection pattern of certain ends of the conductive strands realizes immunity from the electromagnetic interference or insult. In other words, the connection pattern of certain ends of the conductive strands has an anti-antenna geometrical shape such that the anti-antenna geometrical shape prevents the medical stent from creating an imaging artifact and/or allows the imaging of the volume within the stent.
• Other shapes for the conductive strand ends to help secure theconductive strands224,226,228 &230 together, while keeping theconductive strands224,226,228 &230 electrically isolated, may be used. For example,FIG. 12 shows theconductive strands224,226,228 &230 withbarbed ends240,242,246 &248, respectively, so that thefastening material234 may be shaped around the barbed ends240,242,246 &248 to securely fasten to thestrands224,226,228 &230 with no possibility of any of the strands slipping out of thematerial234.
• It is noted that, although not shown, certain of the barbed ends240,242,246 &248 of theconductive strands224,226,228 &230 may be electrically connected to each other to form the proper loop circuitry needed to produce the opposing currents in the stent so that a net zero current is realized. For example, conductivebarbed end240 may be electrically connected to conductivebarbed end242, while conductivebarbed end246 may be electrically connected to conductivebarbed end248. On the other hand, for another example, conductivebarbed end240 may be electrically connected to conductivebarbed end246, while conductivebarbed end248 may be electrically connected to conductivebarbed end242.
• The connection pattern of certain barbed ends of the conductive strands realizes immunity from the electromagnetic interference or insult. In other words, the connection pattern of certain barbed ends of the conductive strands has an anti-antenna geometrical shape such that the anti-antenna geometrical shape prevents the medical stent from creating an imaging artifact and/or allows the imaging of the volume within the stent.
• FIG. 13 illustrates another type of conductive stent weave which can be employed as a stent or as a component of a stent. Theconductor260 is formed to produce aloop261 that would have induced current flowing in a first direction, aloop264 that would have induced current flowing in a second direction, aloop266 that would have induced current flowing in the first direction, and aloop268 that would have induced current flowing in the second direction, the first direction being opposite of the second direction. Thedirection changing pattern263 enables the adjacent loops to have induced currents flowing in opposite directions.
• An example of such a configuration is a loop-½ hitch-loop-½ hitch pattern wherein the ½ hitch would correspond to thedirection changing pattern263 ofFIG. 13.
• As illustrated inFIG. 13, stackingsuch loops261,264,266,268 . . . , with the intersperseddirection changing pattern263, forms a cylindrical coil. In this way, when following theconductor260 from one end to the other, a trace would travel clockwise around thefirst loop261, counter-clockwise around thenext loop264, clockwise around the next266, counter-clockwise around the next268, and so on.
• At each cross-over point,nonconductive materials267 &265 are used to electrically insulate theconductive material260 from itself Additionally, thenonconductive materials267 &265 secure the crossed-overconductive material260 from deforming or slipping or otherwise changing the cross-over points.
• Optionally, non-conductivestructural ribbing262 may also be added to increase the structure strength and integrity of the overall stent.
• The stacked loop pattern, with interspersed direction changing pattern, realizes immunity from the electromagnetic interference or insult. In other words, the stacked loop pattern, with interspersed direction changing pattern, has an anti-antenna geometrical shape such that the anti-antenna geometrical shape prevents the medical stent from creating an imaging artifact and/or allows the imaging of the volume within the stent.
• FIG. 14 illustrates the deployment of anarterial stent302. Thearterial stent302 is initially attached to aguidewire306 at itsdistal end304 and is positioned into place within abody310 and within anartery308. Thearterial stent302 is fabricated out of a memory material, for example, nitinol which, when heated, returns to a previous manufactured shape.
• Initially thearterial stent302 has a small cylindrical diameter. WhenRF energy312 is transmitted through thebody310, thearterial stent302 will heat up and expand to its final deployed diameter.
• In one embodiment, thedistal end304 of theguidewire306 is coated with a material which is particularly efficient at converting theRF energy312 into heat energy to heat and activate thestent302 expansion.
• In another embodiment, thearterial stent302, which may be a mesh or weave like stent as describe above, is coated with a material322 (seeFIG. 15) which is particularly efficient at converting the RF energy312 (seeFIG. 15) into heat energy. It is noted that thearterial stent302 should be constructed to realize immunity from the electromagnetic interference or insult. In other words, thearterial stent302 should be constructed to have an anti-antenna geometrical shape such that the anti-antenna geometrical shape prevents the medical stent from creating an imaging artifact and/or allows the imaging of the volume within the stent.
• FIG. 15 shows a cross-section of thearterial stent302 which is comprised of the stent meshshape memory material320 coated withheating material322. Alternatively, only the outside of thestent mesh320 is coated with theheating material322. Alternatively, only the inside of thestent mesh320 is coated with theheating material322.
• TheRF energy312 may be that which is transmitted by an MRI system (not shown) or may be that from some other RF transmitter (not shown). It is known that in some cases and under some conditions long conductors in an MRI environment can heat up. When this phenomenon is incorporated into the catheter or guide-wire which is part of the overall stent delivery system, this heat energy can be utilized to activate the shape memory material expansion, thus expanding the stent.
• FIG. 16-21 illustrate one possible fabrication process for a medical stent. Referring toFIG. 16, theinitial stock material349; for example, tantalum; is in the shape of a hollow cylinder. The cylinder may be cut into a pattern as illustrated inFIG. 17, for example. The cutting of thecylinder stock material349 may be accomplished by laser cutting or by other means.
• FIG. 17 shows the resultingcut cylinder351 which comprises end rings350 and354, and one half of the stentpattern mesh strands356,358 &360. (Other mesh strands are shown as dashed lines for clarity.)
• Themesh strands356,358 &360 are connected to the end rings350 &354 bytabs362 &364.
• FIG. 18 shows twosuch cut cylinders351 positioned such that one cylinder has been rotated by 180 degrees; so that the two end rings354 are close to each other. As thearrows355 inFIG. 18 illustrate, one cylinder is to be slid into the other. This may be accomplished in several different ways including: heating one of the cut cylinders so that it expands and/or fabricating one of the two cut cylinders out a cylinder stock material which is slightly smaller in diameter than the other.
• FIG. 19 illustrates the two cut cylinders in their final position. The orientation is such that the nodes in thecut pattern381 &382 are close together, but are not touching.
• The two cut cylinders realize immunity from the electromagnetic interference or insult. In other words, the two cut cylinders have an anti-antenna geometrical shape such that the anti-antenna geometrical shape prevents the medical stent from creating an imaging artifact and/or allows the imaging of the volume within the stent.
• FIG. 20 illustrates the application of a non-conductivebinding material390, for example, silicon rubber or other thermoplastic or thermoset polymer, or glass, etc. at each of thenodes381 &382 which rigidly fasten theconductive mesh strands356,358 &360 together. The resultingstent mesh388 is then cut from the supportingnubs362 &364 ofFIG. 17, giving thefinal stent portion388 shown inFIG. 21.
• The pattern that is cut out of the initial hollow cylinder stock ofFIG. 16 may alternatively include “Z” shaped, zig-zag shaped, or sawtooth shaped segments as shown inFIG. 8 which facilitates the final stent's ability to expand radially.
• In one embodiment (not shown, but referring toFIG. 21), the non-conductivebinding material390 ofFIG. 20 is initially in the form of a hollow cylinder which is so dimensioned as to fit between the two cutcylinders351 forming three concentric cylinders, the bindingmaterial390 cylinder being the middle layer. The application of a laser or other means then melts thebinding material390 at the nodes as well as eliminates unwanted binding material.
• In one embodiment, the weaving of the conductive material (see, for example,FIG. 5) is used to produce a sheetstock planar material400 illustrated inFIG. 22. As mentioned for other conductive weaves (see description ofFIG. 5), at all the cross-over points,non-conductive materials401 and403 is applied to hold the cross-over point strands in place and to electrically isolate the conductive strands from one another. Aportion406 of the planar woven sheet or web is cut from the initialwoven sheet400. The dashedlines402 and404 indicate where a cut through the woven sheet orweb400 is made.
• FIGS. 23 and 24 show thecut portion406 being rolled into a cylinder shape. The cut strand, which come together as the cut edges402 and404, are brought together and then attached to one another to hold the stent together. The attachment may be affected by either a conductive material (solder, welding, etc.) or by a non-conductive means (glass, polymer, etc.)
• In one embodiment (not shown) conductive metallic stents are coated with a nano-magnetic thin film coating which reduces the amount of eddy currents generated by the oscillating magnetic fields of an MRI system. In one such embodiment, multiple lays of various compositions and/or thicknesses are applied to the stents. In another embodiment, only portions of the stent are coated with the nano-magnetic thin films, thus changing the MRI system induced eddy current flow pattern.
• In one embodiment, non-magnetic stents are coating with a nano-magnetic thin film coating which alters the magnetic fields of the MRI system enough for the stent to be visible in an MR image without distorting the image of the tissue a short distance from the stent.
• In another embodiment (not shown) conductive metallic stent is coated with a carbon composite material, in part, in patterns, or in whole.
• In another embodiment (not shown) non-conductive stents are coated with a carbon composite material, in part, in patterns, or in whole.
• FIGS. 25 and 26 illustrate astent500 which is, initially, at its smallest radius “r”501. Thestent500 is in the shape of a cylinder.
• FIG. 25 illustrates a cross section of thestent500. Astent strand512 is wrapped within thestent500 to reduce thecylindrical radius501 before deployment with a body. Thestent500 has a track-and-lock mechanism502 through whichstent strand512 passes and is confined to.
• FIG. 26 gives one example of a track-and-lock mechanism502. Aportion506 of the track-and-lock mechanism502 is shown as a cut-away view inFIG. 26. Thestent strand512 has teeth which match that of theteeth510 within the track-and-lock mechanism502. Thestent strand512 is confined to move in theguide slot514 and can only move in such a way so as to increase theoverall radius501 of thecylinder stent500.
• The shape of the teeth of thestent strand512 and the shape of the teeth of the track-and-lock mechanism502 prevent thestent strand512 from moving in such a way as to reduce thecylinder radius501. Thus, when deployed with; e.g. a balloon catheter system (not shown); the stent may be expanded to its full and final radius and locked into that radius.
• In summary, the various stent embodiments, described above, realize immunity from the electromagnetic interference or insult. In other words, the stent has an anti-antenna geometrical shape such that the anti-antenna geometrical shape prevents the medical stent from creating an imaging artifact and/or allows the imaging of the volume within the stent.
• Although the various embodiments discussed above have been described in the context of a medical stent, the various concepts and aspects of the present invention are readily applicable to other devices and uses.
• For example, the pattern of electrically conductive material, according to the various concepts of the present invention, can be used in medical devices having electrically conductive structures that would, under normal circumstances, generate imaging artifacts and/or heat in response to the imaging processes, such as magnetic radiation imaging (MRI), and/or radio frequency radiation so as to make the medical devices imaging artifact immune and heat resistant. More specifically, the pattern of electrically conductive material, according to the various concepts of the present invention, could be used to create an imaging artifact immune and heat resistant mail for a doctor's glove or clothing.
• While various examples and embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that the spirit and scope of the present invention are not limited to the specific description and drawings herein, but extend to various modifications and changes.

Claims (18)

1. A medical stent, comprising:

a plurality of links, each link being connected together so as to form a cylindrical shaped medical stent, each link being shaped so as to be expandable, said expansion of said links causing an increase in a radius of the medical stent.

2. The medical stent as claimed inclaim 1, wherein said plurality of links are multiple electrical conductors, said multiple electrical conductors forming a pattern to substantially prevent the self-deploying medical stent from creating an imaging artifact.

3. The medical stent as claimed inclaim 1, wherein said plurality of links are multiple electrical conductors, said multiple electrical conductors forming a pattern to substantially allow imaging of a volume within the stent.

4. The medical stent as claimed inclaim 1, wherein said plurality of links are multiple electrical conductors, said multiple electrical conductors forming a pattern to substantially prevent the self-deploying medical stent from creating an imaging artifact and substantially allow imaging of a volume within the stent.

5. The medical stent as claimed inclaim 1, wherein each link is tantalum.

6. The medical stent as claimed inclaim 1, wherein each link is nitinol.

7. The medical stent as claimed inclaim 1, wherein each link is stainless steel.

8. The medical stent as claimed inclaim 1, wherein each link is NbZr.

9. The medical stent as claimed inclaim 1, wherein each link is titanium.

10. A medical stent, comprising:

a plurality of links, each link being connected together so as to form a cylindrical shaped medical stent, each link being shaped so as to be expandable upon application of heat, said expansion of said links causing an increase in a radius of the medical stent.

11. The medical stent as claimed inclaim 10, wherein said plurality of links are multiple electrical conductors, said multiple electrical conductors forming a pattern to substantially prevent the self-deploying medical stent from creating an imaging artifact.

12. The medical stent as claimed inclaim 10, wherein said plurality of links are multiple electrical conductors, said multiple electrical conductors forming a pattern to substantially allow imaging of a volume within the stent.

13. The medical stent as claimed inclaim 10, wherein said plurality of links are multiple electrical conductors, said multiple electrical conductors forming a pattern to substantially prevent the self-deploying medical stent from creating an imaging artifact and substantially allow imaging of a volume within the stent.

14. The medical stent as claimed inclaim 10, wherein each link is tantalum.

15. The medical stent as claimed inclaim 10, wherein each link is nitinol.

16. The medical stent as claimed inclaim 10, wherein each link is stainless steel.

17. The medical stent as claimed inclaim 10, wherein each link is NbZr.

18. The medical stent as claimed inclaim 10, wherein each link is titanium.

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