Optical waveguides – Optical fiber bundle
Reexamination Certificate
1998-12-22
2001-05-29
Bovemick, Rodney (Department: 2874)
Optical waveguides
Optical fiber bundle
C600S433000, C604S218000, C604S218000, C606S015000, C606S016000
Reexamination Certificate
active
06240231
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to interventional medical devices, and more particularly concerns an optical fiber composite shaft having variable stiffness for enhanced performance of the composite shaft when used with or without a guide catheter, or as a stand-alone flow directed device for use in the vascular system as part of an imaging system, a therapeutic system, or for delivery of medical devices.
DESCRIPTION OF RELATED ART
Conventional minimally invasive catheter based therapies typically require guide wires that are one to two meters long extending through a longitudinal lumen in the catheter, and that are torqueable and pushable at the proximal end, yet soft and flexible at the distal end. Many such guidewires are made of stainless steel or the like, and are ground to tapers which provide the desired bending properties along the guidewire. Recently, numerous minimally invasive sensing and actuation procedures have been developed which benefit from the unique qualities of an optical fiber to deliver optical light or power to the distal tip of the optical fiber. For example, optical fiber based technology can be used for imaging, treatments such as “thrombolyzing” blood or cutting tissue by use of high energy light delivered through the end of the optical fibers, and for the delivery of therapeutic agents, such as timed release agents or embolics. However, conventional optical fiber technology has not been easily adaptable to such applications, particularly when the optical fiber must also act as a guidewire, either within a catheter or as a stand-alone device, since optical fibers, when used alone, are not very torqueable, pushable or resilient when compared to guide wires made from a variety of other, more rigid, materials. Also, small diameter optical fibers are quite “floppy”, while larger diameter fibers can be too stiff to maneuver through sharp bends, and the use of optical fibers as guidewires or pushers within catheters can thus be difficult and quite technique sensitive.
A variable stiffness catheter having a longitudinal lumen is known that is composed of a relatively flexible outer coaxial tube and at least two tandemly disposed inner coaxial tube segments, the tube segments varying in stiffness, with the stiffest being located at the proximal end of the catheter and the least stiff ending proximal of the distal end of the catheter, thus providing the catheter with a minimum of two regions of different stiffness and flexibility. In order to reinforce a wide variety of catheters incorporating longitudinal lumens for interventional therapies, catheters in the prior art have used reinforcements to the exterior of the catheter, including additional strengthening layers and the like to alter the bending characteristics of the catheter. However, such a catheter structure is typically only capable of being used with a guidewire, and thus cannot provide the benefits of optical fiber technology unless the guidewire is withdrawn and exchanged for an optical fiber. Thus, there remains a serious limitation in the capability of flow directed optical fiber shafts and optical fibers used within catheters to provide the torquability, pushability and resistance to fracture available from metal guidewires. It would also be desirable to provide an optical fiber with variable stiffness to allow optical fibers to be more pushable at the proximal end and more trackable at the distal end, and to make the use of optical fibers in catheter-based therapies more straight forward and less technique sensitive. The present invention addresses these and numerous other needs.
SUMMARY OF THE INVENTION
Briefly, and in general terms, the present invention in its broadest aspect provides for a variable stiffness composite sensor shaft, with a variable stiffness jacket encapsulating the sensor shaft to make the use of such a sensor shaft in catheter based therapies more predictable, straight forward, and less technique sensitive. Typically, such a sensor shaft can be an optical fiber or the like which by itself has physical characteristics that are undesirable for guidewires or stand-alone flow directed devices. By use of the invention, a variable stiffness shaft can be made which is more pushable at the proximal end and more trackable at the distal end, with the capability to provide a wide range of predictable variations in stiffness and other structural parameters over the length of the shaft. It has been found that it is often the case that a sensor shaft such as an optical fiber or ultrasonic conductor is made of a material that has undesirable characteristics for guidewires, since they are generally of a less resilient and strong material than those typically chosen for guidewires. The invention overcomes these limitations by providing for means to selectively strengthen the sensor shaft by low profile overlays of materials to create a composite shaft. A variable stiffness optical fiber shaft constructed according to the invention can be used in conjunction with a guide catheter or as a flow directed, stand alone catheter.
By using the construction according to the invention, coating or heat shrinking a heat shrinkable material on the outside diameter of the optical fiber will improve tracking of the device, and heat shrinking layers of a heat shrinkable material, braid or coil imbedded in a polymer layer, or other polymers in telescoping fashion from proximal to distal end will yield a shaft with a stiffer, more manageable, proximal end and a softer, more maneuverable, distal tip.
The invention accordingly provides in a presently preferred embodiment for a variable stiffness optical fiber shaft for placement within the vascular system, and the invention is particularly adaptable for use within a tortuous, small diameter vessel such as those found in the vasculature of the brain. The variable stiffness optical fiber shaft comprises an optical fiber having a proximal end and a distal end, and at least one coaxial layer of a polymer, metal, or both for providing a desired additional stiffness extending over the optical fiber, to thereby provide desired variations in stiffness along the length of the shaft. In one presently preferred embodiment, the variable stiffness optical fiber shaft comprises a plurality of coaxial layers of heat shrink polymer encapsulating the optical fiber, the coaxial layers extending from the proximal end of the optical fiber toward the distal end, the plurality of coaxial layers having different lengths to provide the optical fiber shaft with varying stiffness over the length of the optical fiber shaft. The plurality of coaxial layers can be arranged in successive progressively shorter coaxial layers, and can be formed of heat shrink polymeric material, such as polyethylene, polytetrafluoroethylene (PTFE) polyethylene terephthalate (PET), polyether ethyl ketone (PEEK), polyphenylene sulfide (PPS), or any of a variety of other polymers which can be fabricated into a structure and necked or shrunk over a shaft. A layer of braid or coil may also be embedded in the polymer to increase the stiffness of the composite shaft in certain areas.
While the invention can effectively use tubes which are placed over the exterior of the optical fiber shaft and then heat shrunk or bonded by adhesive to the fiber, it is also contemplated that the shaft can be reinforced by other longitudinally extending additional structures with varying cross sections for certain specific applications.
In a presently preferred embodiment, the variable stiffness optical fiber shaft comprises a first coaxial layer of a heat shrink polymer extending essentially the entire length of the optical fiber, from the proximal end to the distal end; a second layer of a coaxial layer of a heat shrink polymer, of the same or different material as the first coaxial layer, extending over the first coaxial layer from the proximal end of the optical fiber to a distal position spaced proximally from the distal end of the optical fiber; and a third coaxial layer of a heat shrink polymer, of
Debeer Nicholas C.
Ferrera David A.
Han Thuzar
Kurz Daniel R.
Wong Rose Y.
Bovemick Rodney
Fulwider Patton Lee & Utecht LLP
Kang Juliana K.
Micrus Corporation
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