Patent Application
20050171437
Not Applicable.
Not Applicable.
1. Field of Invention
This invention pertains to apparatus for switching signals, lambdas, or bandgaps of optical spectrum in a catheter. More particularly, this invention pertains to selectively applying a plurality of optical signals to a optical fiber in a catheter and processing the optical signals returned from the catheter.
2. Description of the Related Art
During the past twenty years, the use of catheters to enter, diagnose, and treat diseases and malfunctions of the blood vessels and other vessels has become commonplace. Catheters are widely employed to deliver stents to occluded blood vessels, as well as to position and deploy balloons to enlarge occluded blood vessels. Also, catheters are used in combination with excimer lasers for treating and removing plaque.
Unfortunately, medical professionals are unable to take advantage of the relatively non-invasive catheter in certain cases. For example, in the case of a totally occluded aortic or other vessel, it is difficult or impossible to safely insert and position a catheter due to the difficulty or impracticability of using X-RAY techniques to position the catheter. In approximately 330,000 cases per year, this results in open-heart surgery, which in addition to a long and painful recovery and high expense, carries significant risks.
Similarly, the usefulness of catheters in treating and removing plaque is often limited. Recent findings indicate that nonstenotic, lipid rich coronary plaques, also called “vulnerable plaques” or “biological hot plaques” are exceptionally likely to cause the vast majority of fatal heart attacks. In other words, the majority of the approximately 1,300,000 heart attacks that will occur this year are caused by a soft plaque, for which there is not currently available a viable tool for identifying, diagnosing, or treating. While catheter-based excimer lasers have been proven to be effective at treating and removing soft plaques, their use has been limited by the practitioner's inability to see and control the position of the catheter before, during, and after using the excimer laser.
Various tests exist for identifying persons at risk of myocardial infarction. These persons are candidates for further evaluation and treatment. In such a case, an ideal treatment and system would allow for the use of multiple devices within a single catheter, therefore allowing several functions, some complementary, over the course of a single catheter insertion procedure, which would allow: a) the use of an interferometer capable of navigating the catheter through the blood vessels to allow the catheter to be moved through total occlusions as well as through the twists and turns of the blood vessels; b) the use of an interferometer that could use multiple wavelengths to differentiate among various materials in the optical path, including vulnerable plaque, calcified plaque, arterial walls, etc.; and c) the intermittent use of an excimer or other laser to ablate, vaporize, or otherwise destroy the plaque in the path of the catheter.
There are three primary instruments routinely used in catheter insertion procedures. First, Michelson interferometers of various types are used to differentiate between plaque and arterial walls, and to do so with physical resolution in the range of 10 microns. Michelson interferometers provide the ability to see and navigate through a total occlusion. Second, Diffuse Reflectance Near Infrared Spectroscopy (DRNIRS), often with regard to multiple wavelengths, is effective at differentiating and identifying a wide variety of substances, including hundreds of plasma constituents, such as glucose, calcified plaque, vulnerable plaque, total protein, human metalloproteins, creatinine, uric acid, triglycerides, uric acid, urea, etc. DRNIRS interferometry provides the capability to detect and determine materials without actually contacting or touching them. The substances are distinguished by the characteristic absorption and reflectance of specific wavelengths of light, typically between 300 and 2200 nanometers. Third, excimer lasers typically use a very short pulse, less than 1 microsecond, normally about 100 nanoseconds, and could be operated together with both types of interferometry in duty cycles as high as hundreds of hertz.
Other devices for evaluating and treating arterial disease are known to those skilled in art. As with all optical devices, it is generally known to use either a single fiber or a bundle of fibers to transmit one or more optical signals. Often these devices are intended to improve the resolution and/or information available using the known navigation and diagnostic techniques and focus on improving a single technique. Examples of such uses are described in the following U.S. patents. U.S. Pat. No. 5,217,456, issued to Narciso, Jr., discloses a catheter for ablation of a lesion. The rotating catheter has a bundle of optical fibers that are used to make fluorescence measurements to identify the radial position of the lesion. U.S. Pat. No. 6,384,915, issued to Everett, et al., and U.S. Pat. No. 6,175,669, issued to Colston, et al., disclose the use of a multiplexed reflectometer for performing Michelson interferometry. Both patents describe a system including a optical fiber set contained within the catheter. The optical fibers are connected to the illumination source via an optical switch, which sequentially cycles the output of the source through the optical fiber set to diagnose consecutive spatially-distinct regions of a lumen. U.S. Pat. No. 6,463,313, issued to Winston, et al., describes a device having dual Michelson interferometers. The outputs are combined to produce a composite image thereby providing more complete information to the medical professional. U.S. Pat. No. 6,501,551, issued to Tearney, et al., discloses the combination of two sources of differing wavelengths using wavelength division multiplexing. The combined signal is injected into a single optical fiber in the catheter. The reflections are separated by wavelengths and guided to separate detectors associated with a particular wavelength.
Devices combining some navigation or diagnostic element, such as a Michelson interferometer, with a treatment element, such as a excimer laser, are known to those skilled in the art. These devices are represented by the angioplasty systems such as the those described in U.S. Pat. No. 5,275,594, issued to Baker, et al. and in U.S. Pat. No. 6,463,313, Winston, et al. Both Baker, et al., and Winston, et al., disclose systems that use feedback from the diagnostic element to control the operation of the treatment element. U.S. Pat. No. 6,389,307, issued to Abela, discloses a system having a lower power diagnostic laser and a high power treatment laser coupled to the same optical fiber. The operator activates the desired laser, preferably one at a time, to achieve a desired function.
An optical switching system for use with a catheter-based analysis and treatment instrument that facilitates a procedure that combines navigation, identification, and correction within the domain of insertion and operation during a single catheter experience or procedure would offer dramatic benefits to save lives and preclude coronary events. This procedure would be an effective, efficient, and safe method for treating a very dangerous condition, especially when compared to the options of performing no procedure or performing a bypass surgery.
An apparatus and method for treatment of the arteries of the heart using optical switches to allow safe navigation of blood vessels with a catheter through the use of one or more interferometer systems and intermittent or concurrent treatment through the use of a treatment laser, precise insertion of a stent to cover the hot plaque, or other tool. The apparatus and method allows differentiation among arterial walls, calcified plaque, vulnerable plaque, such as Biological Hot Plaque, thin capped fibrous atheromas (TCFAs), and other forms and substance in blood vessels. The device and method is useful in the treatment of Atherosclerosis, Arteriosclerosis, and Thrombosis, the performance of Hemodialysis Access Maintenance, and the insertion of Trans jugular Intrahepatic Portosystemic Shunts.
The apparatus allows multiple optical sources to be switched into one or more optical fibers in the catheter. The return signal from the catheter is switched between multiple optical detectors, such as an interferometer, a spectrum analyzer, and a reflectometer. The use of optical switches allows the use of one or more interferometric systems in the same fiber, as well as using the switches to control a duty cycle that protects the optical source and detectors and other vulnerable or sensitive optical devices from harmful back reflections generated by the short but powerful pulses of an excimer, or other, laser or light source, or in the case that such devices are not in danger of being harmed by back reflection, switching through several interferometric light sources in order to determine geometry and composition in the path of the catheter.
The use of an optical switch provides the capability to sample multiple lambdas and/or bandwidth spectra through a fiber and from the loci of a single fiber end in the catheter into the loci of a single point on an artery wall quick enough to safely assure that all the sampling of lambdas or bandwidth spectra occurred in the same loci in the artery allowing an inference as to the composition at that loci on the artery wall, allowing to differentiate among artery wall, calcified plaque, hot plaque and other materials.
The above-mentioned features of the invention will become more clearly understood from the following detailed description of the invention read together with the drawings in which:
An optical switching system for use with catheter-based analysis and treatment, or optical switching system, is shown and described. The use of an optical switching system allows the use of one or more interferometric systems in the same fiber, as well as using the optical switching system to control a duty cycle that protects the optical source and detectors and other vulnerable or sensitive optical devices from harmful back-reflections generated by the short pulses of a high-power light source, such as an excimer laser, or in the case that such devices are not in danger of being harmed by back reflection, switching through several interferometric light sources in order to determine geometry and composition in the path of the catheter.
The use of optical switches greatly aids in safely constructing and using a device for locating, identifying, and removing a blockage. First, an optical switch allows the use of multiple wavelengths and the insertion of these into one or more optical fibers by rapidly switching among the available wavelengths. It is important to note that while various types of interferometry may often be performed on a single type of fiber, for the most part they cannot be operated at the same time as they would interfere with the functionality and resolution of the various interferometers. For this reason, in the case where multiple interferometers are useful, the optical switch permits one or more interferometers to operate through the same optical fiber set. For example, the procedure can use Michelson interferometry for navigating through a total occlusion and use Diffuse Reflectance Near Infrared Spectroscopy (DRNIRS) for differentiating between blood, water, vulnerable plaque, calcified plaque, and other objects. Similarly, when using identifying interferometry, various wavelengths are required to identify different materials, such as calcium rich plaque, vulnerable plaque, blood, water, arterial walls, etc. Again, the optical switch allows the necessary wavelengths to be switched through the optical fibers. Second, an optical switch provides the ability to return the reflectances from the end of the catheter to multiple interferometry devices. Third, an optical switch makes it possible to break the optical connection to both optical sources and optical detectors during the use and duty cycle of a high-power laser. By taking the optical sources and optical detectors off-line protects them from harmful and potentially destructive back reflections, to which such devices are exceptionally vulnerable.
As illustrated and described herein, the optical circulator 106 passes signals between successive ports in one direction. However, those skilled in the art will recognize that single direction signal paths can be achieved using other devices including optical switches. The bank of lasers 102 is presumed to have multiple sources; however, those skilled in the art will recognize that a single tunable laser or other tunable source capable of generating the desired wavelengths could be used. In such an arrangement, the single source subsumes the functions of the multiple sources and the first optical switch without departing from the spirit and scope of the present invention. Similarly, the optical detectors 122 is illustrated as including multiple devices performing differing functions. Those skilled in the art will recognize that the optical detectors may include only a single analysis device or single multi-function analysis device and would not require the third optical switch. In either event, such a substitution could easily be warranted by advances in the illumination source or the optical detectors or may merely reflect a medical apparatus performing fewer functions than the illustrated embodiment.
Those skilled in the art will recognize that the number of optical fibers depends upon the desired field of vision and the image processing occurring at the analysis device and, therefore, that number can be varied without departing from the scope and spirit of the present invention. Similarly, the arrangement of the optical fibers depends both upon number and the desired field of vision. Typical, the optical fibers will be equidistantly spaced around the perimeter of the primary tube to provide the most complete field of vision; however, those skilled in the art will recognize other arrangements may be used without departing from the scope and spirit of the present invention.
The three optical switches 506, 508, 514 are interfaced by an optical junction 516. The primary function of the optical junction 516 is to route the optical signals to the appropriate destination. This generally means that source signals are routed into the catheter and the reflectances returning from the catheter are routed to the output ports. A secondary function of the optical junction 516 is to prevent optical signals from traveling to undesirable destinations. This generally means that the reflectances are prevented from reaching the input ports 502 and the source signals are prevented from directly reaching the output ports 504. These two functions are realized by implementing the optical junction with an optical circulator; however those skilled in the art will recognize that the optical junction can be built from combinations of other optical components including splitters, multiplexers, demultiplexers, and switches without departing from the scope and spirit of the present invention.
A controller 518 coordinates the operation of the three optical switches 506, 508, 514 so that the reflectances of an input signal of a certain type or wavelength are directed to the appropriate detector for analysis. This is facilitated by software routines processed by the controller 518 and commands received from an optional user interface 520. If required, the optical junction can also be placed under the control of the controller 518.
It should be noted that while the illustrated embodiments of
Another feature of the present invention is the ability to control the routing of the optical sources through the catheter to obtain a full picture of the lumen. By sending the signal from each optical source through a selected group of the optical fibers in the catheter a more accurate picture of the lumen is obtained.
The usefulness of the information obtained is largely dependent upon the acquisition speed of the information. A rapid acquisition speed allows both navigation and identification information to be obtained about the same location in the artery. If the acquisition speed is to low, the navigation information and the identification information are not associated with the same location within the artery and do not provide a complete picture. Obviously, the switching speed is dependent upon the forward movement speed and/or the rotational speed of the catheter and the number of wavelengths required to obtain a complete picture. The present inventor has found that a switching speed in the range of 30 to 50 milliseconds provides a sufficient data acquisition speed for most applications, although other switching time ranges are acceptable. The optical switching system of the present invention is capable of operating at the necessary switching speed to obtain useful information.
Certain characteristics of the optical switching system are useful in providing an efficient implementation; however, those skilled in the art will recognize that these characteristics are intended to be exemplary and not limiting. In various embodiments, the optical switching system latches exhibits low optical loss, nominally less than 1 dB, and low port to port variability, nominally less than 0.5 dB. The optical switching system latches in all positions, making the switch stable, resistant to shock and vibration and unintentional switching. The optical switching system exhibits temperature Independent operation with regard to optical performance. The optical switching system exhibits low polarization dependent loss, nominally less than 0.2 dB. The optical switching system exhibits a switching time quicker than 100 milliseconds.
From the foregoing description, it will be recognized by those skilled in the art that a device and method for safely navigating blood vessels using a catheter has been provided. The device and method uses an optical switch to control the inputs and outputs of optical fibers set in a catheter. The device can differentiate among arterial walls, calcified plaque, vulnerable plaque (biological hot plaque and thin capped fibrous atheromas), and other forms and substances in blood vessels. The device is useful in the treatment of the arteries of the heart, Atherosclerosis, Arteriosclerosis, Thrombosis, for the performance of Hemodialysis Access Maintenance, and for the insertion of Transjugular Intrahepatic Portosystemic Shunts. In addition, the device provides for the intermittent or concurrent use of a treatment laser, such as an excimer laser, or other treatment tool, such as a stent or an angioplasty balloon, in conjunction with one or more interferometer systems and devices by use of optical switches.
While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept.
