Surgery – Instruments – Light application
Reexamination Certificate
1999-01-09
2001-05-08
Cohen, Lee (Department: 3739)
Surgery
Instruments
Light application
C606S010000, C606S012000, C128S898000, C356S340000, C356S340000
Reexamination Certificate
active
06228076
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to systems and methods for controlling medical devices, and more particularly, to a control system and methods for controlling tissue ablation.
Many medical treatments involve the removal of diseased or damaged tissue from within the body. For example, common surgical practice requires the excision of tumors, cysts, and polyps, which may appear in any area of the body, and the removal of atherosclerotic plaque from arteries. Classical surgical techniques require a properly trained surgeon to directly view the tissue being treated to determine which, and how much, of the tissue can safely be removed. This type of procedure is highly invasive and typically requires a lengthy recovery period for the patient.
More modern, less invasive surgical tissue removal techniques are known. Generally these techniques greatly benefit the patient, but present new challenges for the surgeon. For example, catheters, endoscopes and laparoscopes are now commonly used for a variety of surgical procedures and require minimal entry into the body. Use of these techniques generally decreases surgical trauma and recovery time, and improves outcome, but also incur significant disadvantages for the surgeon. Particularly, such techniques impair visualization of the affected region and substantially limit surgical working space. For example, optical fiber endoscopes are known but cannot be used in a blood field without first clearing the blood with a saline solution. Ultrasound probes are known but often produce false echoes when used for looking forward through, for example, the lumen of an artery. Fluoroscopy is known but is two-dimensional and exposes the patient and medical personnel to various forms of radiation.
Impaired visualization of the surgical field makes removal of diseased tissue difficult. In particular, the use of high energy tissue ablation devices such as those powered by lasers, radio frequency transmission, microwaves and the like, is risky under conditions of impaired visualization because poor discrimination of healthy tissue from diseased tissue can result in damage of healthy tissue. Accordingly, a surgeon operating such an ablation device must advance it extremely cautiously, perhaps missing diseased tissue which should be removed.
It would therefore be desirable to provide a precise and reliable method for controlling the activation and advancement of tissue ablative devices. It would also be desirable to provide an improved method for visualizing internal body tissues being treated with minimally invasive tissue ablative devices. It would also be desirable to provide an improved method and apparatus for differentiation of abnormal tissue from normal tissue.
BRIEF SUMMARY OF THE INVENTION
In an exemplary embodiment, a method for controlling tissue ablation uses optical time domain reflectometry data to differentiate abnormal tissue from normal tissue, to control ablation of abnormal tissue by controlling the delivery of energy to a tissue ablation element. Using data provided by an interferometric apparatus, a control system provides control signals to tissue ablative apparatus and controls activation of the tissue ablation apparatus so that normal tissue is left untreated while abnormal tissue is ablated.
In one aspect, the present invention is directed to using interference data to identify an interface between abnormal tissue and healthy or normal tissue, and altering the delivery of energy to the tissue ablative apparatus in response to identification of an interface. In one embodiment, the control system includes a microprocessor and an energy controller. The control system is coupled to an interferometric apparatus for providing interfering light beams which produce the interferometric data. More specifically, for example, a low coherence light source producing a light beam is coupled to a beam splitter which splits the beam into two beams, a first or reference beam, and a second or sampling beam, which are transmitted respectively down a first optical fiber, and a second optical fiber. The second optical fiber extends through the lumen of a support member such as a catheter so that a distal, sampling end of the second optical fiber can be positioned near a sample, such as an internal body tissue to be inspected. The first optical fiber is positioned outside the body. The first beam is reflected at the distal or free end of the first optical fiber by a reflector coupled thereto, while the second beam is reflected at the distal sampling end by the sample. The lengths of the first and second optical fibers are adjustable with, for example, a piezoelectric coil. The reflected beams interfere with one another when recombined at the beam splitter. The path length difference between the recombined beams produces a pattern of interference which is detected by a detecting element coupled to the beam splitter. The detecting element provides the interference data to the control system, in which the microprocessor generates a psuedoimage of the sample, and detects interfaces between normal and abnormal tissue. In response to the detection of such an interface, the microprocessor generates and supplies control signals to the energy controller, which accordingly alters the delivery of energy to the tissue ablative apparatus.
In another aspect, the present invention is directed to providing a psuedoimage of a tissue sample for visual display to an individual who is manually advancing a tissue ablative element of the tissue ablative apparatus. In an exemplary embodiment, the microprocessor is coupled to an output display device such as a monitor. The psuedoimage data generated by the microprocessor is displayed on the monitor so that the operator has a visual image while manually advancing the tissue ablative element. The operator can advance while watching the image until, for example, the control system detects an interface and alters the delivery of energy to the tissue ablative apparatus.
The control system and method provide for minimally invasive control of tissue ablation. Further, the system provides high resolution image data so that tissue ablation can be controlled at a very fine scale. In addition, the system and method provide for improved differentiation of abnormal tissue from normal tissue.
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Journal of Biomedical Optics, Apr. 1999, pp. 236-237, Barry R. Masters, Early Development of Optical Low-Coherence Reflectometry and Some Recent Biomedical Applications, Department of Ophthalmology, University of Bern, Bern, Switzerland.
Neet John M.
Winston Thomas R.
Armstrong Teasdale LLP
Cohen Lee
Farah Ahmed
IntraLuminal Therapeutics, Inc.
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