Guide wire assembly

Details Guide wire assembly Guide wire assembly

1998-04-15

2001-02-27

Lateef, Marvin M. (Department: 3737)

Surgery

Diagnostic testing

Flexible catheter guide

C600S478000, C356S340000

Reexamination Certificate

active

06193676

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to medical guide wires and catheters and more particularly, to guiding assemblies and guiding methods for guide wires.
BACKGROUND OF THE INVENTION
Disease processes, e.g., tumors, inflammation of lymph nodes, and plaque build-up in arteries, often afflict the human body. As one specific example, atherosclerotic plaque is known to build up in the walls of arteries in the human body. Such plaque build-up restricts circulation and often causes cardiovascular problems, especially when the build-up occur in coronary arteries.
To treat such disease, it often is necessary to guide a medical device to the diseased site, and then use the medical device to treat the diseased area. Often a guide wire is used to help guide other treatment devices. A guide wire typically is required to properly position a catheter in an artery. The guide wire is advanced and forms a path, through the artery and region of plaque build-up. The catheter or other device such as a balloon or rotational atherectomy device is then guided through the artery using the guide wire.
Known guide wires exist for the treatment of tissue. For example, known guide wires use laser energy to remove plaque build-up on artery walls as the guide wire is advanced One known catheter includes a laser source and a guide wire body. The guide wire body has a first end and a second end, or head, and several optic fibers extend between the first end and the second end. The laser source is coupled to each of the optic fibers adjacent the catheter body first end and is configured to transmit laser energy simultaneously through the optic fibers.
To remove arterial plaque, for example, the guide wire body is positioned in the artery so that the second end of the guide wire body is adjacent a region of plaque build-up. The laser source is then energized so that laser energy travels through each of the optic fibers and substantially photoablates the plaque adjacent the second end of the catheter body. The guide wire body is then advanced through the region to photoablate the plaque in the entire region.
However, it often is difficult to guide known guide wires through the body without risking damage. For example, known guide wires typically cannot be easily advanced through partially or totally occluded arteries without substantial risk of damaging or puncturing the artery wall. As the guide wire is advanced through the artery, it will encounter obstructions to advancement including plaque build-up or the artery wall itself. However, known guide wires typically do not distinguish between plaque build-up and the artery wall. An operator may therefore incorrectly identify an obstruction as plaque build-up and attempt to push the guide wire through the obstruction, resulting in injury or puncture of the artery wall.
Accordingly, it would be desirable to provide a guide wire including a guidance system to determine the safety of advancing the guide wire further into the vessel. In particular, it would also be desirable to provide such a guide wire with the capability of providing information to an operator to distinguish among the types of obstructions which might be hindering advancement of the guide wire.
SUMMARY OF THE INVENTION
These and other objects may be attained by a guide wire assembly which, in one embodiment, includes an interferometric guidance system. Particularly, the guide wire assembly includes a substantially cylindrical guide wire including a first end, a second end, or guide wire head, and a bore extending between the first and second ends. The interferometric guidance system is coupled to the guide wire and includes a low coherent illumination source, an optical beam splitter, a first optic fiber, a second optic fiber, a photodetector and a computer. The first optic fiber is wrapped around a first piezo electric transducer (PZT), and the second optic fiber is wrapped around a second PZT. The first PZT and second PZT are connected to the guidance system in reverse parallel configuration so that when a sawtooth voltage signal is applied, one expands while the other contracts. The first optic fiber includes a first end and a second end, and extends through the guide wire bore so that the second end is adjacent the guide wire second end. The second optic fiber of the guidance system similarly includes a first end and a second end, and a fixed reflector, such as a metal deposit reflector, on the second optic fiber second end.
The beam splitter includes an illumination source input, a first beam output, a second beam output, and a combined beam output. The illumination source is coupled to the illumination input of the beam splitter. The first end of the first optic fiber, and the first end of the second optic fiber are coupled to the beam splitter. Particularly, the first optic fiber first end is communicatively coupled to the first beam output of the beam splitter, and the second optic fiber first end is communicatively coupled to the second beam output of the beam splitter. The beam splitter combined beam output is coupled to the photodetector, which is communicatively coupled with the computer. The photodetector is configured to determine interference between substantially equal reflected light beams which are initially emitted from the same source and are later split to propagate separately through the first optic fiber and through the second optic fiber.
In operation, the guide wire head is inserted at least partially into, for example, a blood vessel so that the guide wire head and the first optic fiber second end of the guidance system is positioned outside the blood vessel. The beam splitter splits the illumination source light beam into two beams. The first beam is transmitted through the first optic fiber to the tissue located in front of the second end of the guide wire. The tissue, acting as a reflective surface, reflects at least a portion of the first light beam back into the first optic fiber and back to the beam splitter. The second light beam is transmitted through the second optic fiber to the fixed reflector which reflects the second light beam, and the reflected beam is returned to the beam splitter. The beam splitter combines the reflected first and second light beams, resulting in constructive or destructive interference of the two light beams, and creates a combined light beam output. The combined light beam output, including interference information, is coupled to the photodetector and the photodetector output is processed by the computer to determine the safety of advancing the guide wire second end, further into the vessel.
Prior to advancing the guide wire further into the vessel, out of phase frequency signals are applied to the PZTs, causing the PZTs to alternately expand and contract out of phase with one another. This action alternately stretches each optic fiber to extend its length. Specifically, alternating between extending the length of the first optic fiber and extending the length of the second optic fiber changes the length of the optical path for the first and second light beams. This shifts the interference point of the reflected first and second light beams, producing interference data which is processed to provide information regarding the tissue at known distances from the guide wire second end.
The above described guide wire assembly provides a guidance system to determine the safety of advancing a guide wire further into a vessel.


REFERENCES:
patent: 5867268 (1999-02-01), Gelikonov et al.

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