WO2001087176A1

WO2001087176A1 - Optical surgical system and method

Info

Publication number: WO2001087176A1
Application number: PCT/US2001/015943
Authority: WO
Inventors: Fritz Brauer; William D. Fountain; Larry M. Osterink
Original assignee: Clinicon Corporation
Priority date: 2000-05-15
Filing date: 2001-05-15
Publication date: 2001-11-22
Also published as: AU2001261709A1

Abstract

The optical delivery system and method utilizes the combination of a thermally and optically conductive surgical blade with a light source. The light source, which can be a laser or a high power incoherent light source, provides light of a wavelength that is readily absorbed by the blood at the incision site so that photocoagulation is induced to reduce bleeding. The surgical blade is made from a material that transmits light to the incision site without significant absorption of energy which might heat the blade, thus, the only heating of the blade results from contact with the heated blood. Shaping and direction optics can be integrated into the blade to focus, expand, or steer the incoming light beam.

Description

OPTICAL SURGICAL SYSTEM AND METHOD

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an instrument for transmitting optical radiation for application to biological tissue for removal, penetration or treatment of the tissue and more particularly to an instrument for efficiently and accurately delivering optical radiation to a predetermined location on the biological tissue.

Description of Related Art

Surgical applications of lasers are well established in ophthalmology, otolaryngology, gynecology, dermatology and plastic surgery, having been in use, in some cases, for over two decades. Lasers have also become well accepted in the treatment of cardiovascular diseases. The types of lasers are nearly as numerous as the procedures that use them, and selection of a laser for any given procedure depends upon the laser-tissue interaction, which phenomena have been widely reported, and the desired outcome of that interaction. See, e.g., M.J.C. van Gemert and A.J. Welch, "Time Constants in Thermal Laser Medicine", Lasers in Surgery and Medicine 9:405-421 (1989); and J.L. Ratz, "Laser Physics", Clinics in Dermatology 13:1 1-20 (1995), which are incorporated herein by reference. The types of lasers may be grouped into ultraviolet (193-351 nm), visible wavelength (400-700 nm), and infrared (700-100,000 nm). The visible light lasers, such as argon (488- 514 nm), flashlamp-pumped dye (510 nm), copper vapor (578 nm) and ruby (694 nm), are commonly used for selective photothermalysis, e.g., photocoagulation of vascular and pigmented lesions. Laser light within the visible range can be delivered using a number of conventional optical techniques including refractive lenses and quartz fiber optics, since conventional materials such as quartz transmit visible wavelengths with very low loss. Examples of visible light delivery systems are provided in U.S. Patents No. 5,207,673 of Ebling, et a/., "Fiber Optic Apparatus for Use with Medical Lasers", No. 5,495,541 of Murray, et a/., "Optical Delivery Device with High Numerical Aperture Curved Waveguide", and No. 5,530,780 of Ohsawa, "Fiber Optic Laser Conducting and Diffusion Device", the disclosures of which are incorporated herein by reference. Ultraviolet (UV) lasers, or excimer lasers, which include argon-fluoride (193 nm) and krypton-fluoride (248 nm), have been used predominantly in photorefractive keratectomy to ablate corneal tissue. In such applications, the UV light is transmitted through free space for delivery to the outer surface of the patient's cornea. Excimer lasers have also been reported for ablation of skin. (See, e.g., R.J. Lane, et a/., "Ultraviolet-Laser Ablation of Skin", Arch. Dermato/.- 121 : 609-617 (May 1985).)

Visible, UV and near IR laser light have been combined with surgical tips to provide precise control of application of laser radiation and/or to provide means for coagulating blood adjacent an incision. U.S. Patent No. 4,126,136 of Auth, etal., describes a transparent scalpel blade connected to a fiber optic waveguide which transports laser radiation to the blade. The blade, which is preferably synthetic sapphire (AI₂O₃), emits laser radiation through the tapered cutting edge to photocoagulate the blood. U.S. Patent No. 4,627,435 of Hoskin discloses a surgical knife formed from a diamond blade optically coupled to a Nd:YAG laser by a fiber optic bundle. The diamond blade is heated by the laser radiation to provide a cauterizing action while making the incision. The diamond blade may also be coupled to a visible laser to provide illumination for enhanced visibility of the incision site. U.S. Patent No. 4,693,244 of Daikuzono describes an artificial sapphire tip coupled to a quartz optical fiber to transmit radiation from a neodymium:yttrium-aluminum-gamet (Nd:YAG) laser. The 1.06 μm wavelength of the Nd:YAG laser is poorly absorbed by human tissue, and therefore is not normally able to cut or vaporize tissue. However, the sapphire tip allows the Nd:YAG laser to be used for cutting tissue since the optics of the tip concentrate the 1.06 μm laser light, producing a very high power density. Nonetheless, even with the increased power density, the Nd.ΥAG laser light does not provide sufficiently deep coagulation to be useful in certain procedures such as vascular organ surgery and organ transplantation. In alternate configurations, the sapphire tip can be coated with an optically-absorbing material so that the tip is heated by the radiation to coagulate the blood at an incision made with a separate surgical blade.

U.S. Patent 5,320,620 of Long, et al., describes a laser surgical device with a blunt light-emitting element for coagulation. The tip, which may be sapphire, silica or YAG, is coupled to an optical fiber for receiving laser energy. The tip may be coated with a high melting point material to absorb the radiation and heat the tip. The disclosures of each of the above patents, and all other patents cited in this specification, are incorporated herein by reference. U.S. Patent No. 5,194,712 of Jones describes a single crystal diamond cutting tool with an anti-reflection coating bonded to the entry and exit faces of the cutting tool to provide efficient transfer of laser light, or to concentrate laser light at the desired incision. This device uses the laser light to effect cutting of tissue. The diamond material is used as an optically- transmitting window, and is not used to mechanically cut tissue. Of the infrared lasers, which include C0₂ (9.3-10.6 μm) and Nd:YAG

(1.06 μm), the CO₂ laser is most widely used for surgical applications where ablation and cutting of tissue is desired. It is also more readily available and more economical, costing much less than other types of surgical lasers. While Ho:YAG and Nd:YAG lasers still emit light at a short enough wavelength that conventional optical delivery techniques can be used, because of its position in the mid-infrared region of the electromagnetic spectrum, the C0₂ laser cannot be delivered through quartz fiber optics, or silica or sapphire lenses, since these materials are opaque to the 10 micron wavelength and absorb the infrared laser radiation. (Materials that are commonly used with C0₂ laser light, both as lenses and other optically-transmissive elements, include sodium chloride, potassium chloride, zinc selenide, and germanium.) The CO₂ laser light is typically directed through a series of mirrors in a complex articulating system through which the light is delivered to a handpiece containing a lens which will allow the beam to be focussed in a non-contact manner onto the target tissue. Examples of delivery optics for C0₂ laser radiation are disclosed in U.S. Patents No. 5,497,441 of Croitoru, etal., "Hollow Waveguide Tips for Controlling Beam divergence and Method of Making Such Tips"; Patent No. 5,005,944 of Laakmann, er a/., "Hollow Lightpipe and Lightpipe Tip Using a Low Refractive Index Inner Layer"; and Patent No. 4,917,083 of Harrington, et a/., "Delivery System for a Laser Medical System." Relatively recent developments in infrared waveguide technology include a flexible hollow waveguide which is suitable for use with CO₂ lasers having powers over 80 W. Such waveguides are disclosed in U.S. Patents No. 5,440,664 and 5,567,471 of Harrington, et al. It is known that single crystal type Ma diamond (pure carbon, effectively free of nitrogen impurity) has very low absorption at 9.3-10.6 μm, on the order of 0.03 cm^"1, and also has high thermal conductivity, on the order of 2,000 W/m-K in comparison with other far-IR transmitting materials. Diamond optics also do not suffer from the hygroscopic properties of the salt-based C0₂ laser optical materials, and are also mechanically stronger that other infrared- transmitting materials. High quality synthetic diamonds, including diamond films formed using chemical vapor deposition (CVD) have been made possessing similar mechanical, optical and thermal characteristics. For this reason laser cavity windows formed from diamond have been described for use in high power lasers, particularly CO₂ lasers. See, e.g., U.S. Patent No.

5,335,245 of Marie, et al.; and U.S. Patent No. 5,245,189 of Satoh, et al.

See, also, Patent No. 5,194,712 of Jones, supra with regard to use of diamond for transmission of laser radiation, including that from a C0₂ laser.

One surgical application of lasers is for treatment of certain cardiovascular diseases, in particular, techniques for revascularization of ischemic myocardium. The procedure, laser transmyocardial revascularization (TMR), was first reported in the early 1980's following procedures which used a CO₂ laser to form channels in damaged heart tissue to increase myocardial perfusion via the transport of oxygenated blood through the channels. (See, e.g., M. Mirhoseini, et al., "Myocardial Revascularization by Laser: A Clinical Report", Lasers in Surgery and Medicine 3:241 -245 (1983).) This initial work was performed on an arrested heart using a low-power (80 W) CO₂ laser. Subsequent work in TMR led to the numerous laser systems which could be used on a beating heart, such as the one disclosed in U.S. Patent No. 4,658,817 of Hardy ("Method and Apparatus for Transmyocardial Revascularization Using a Laser"), in which a high-power C0₂ laser was used. Patents No. 5,380,316, and 5,554,152, of Aita, et al., assigned to CardioGenesys Corporation of Santa Clara, California, disclose the use of a relatively low-power C0₂ laser or a Holmium:YAG laser for TMR procedures. However, the commercial catheter-based system actually marketed by CardioGenesys is based upon a Ho:YAG laser with a fiber optic/lens contact- type delivery system. The wavelength emitted by the Ho:YAG laser, 2.1 microns, like the Nd:YAG, is sufficiently short to permit use of conventional optical delivery techniques, eliminating the delivery limitations experienced with C0₂ lasers. Patent No. 5,607,421 of Jeevanandam, et al., describes a laser TMR system which uses a thulium-holmium-chromium:YAG laser (THC:YAG) laser with conventional optical fiber delivery via a catheter passed through the left atrium.

Development of other laser TMR systems for investigational use has been reported by PLC Systems, Inc., of Franklin, Massachusetts, Eclipse Surgical Technologies, Inc., of Sunnyvale, California, and Helionetics, Inc., of Van Nuys, California, all for use on a beating heart. The Eclipse TMR system uses a Ho:YAG laser with a fiber optic delivery system for contact delivery to the myocardium. The Helionetics system is based an excimer laser and uses conventional fiber optic delivery techniques. PLC Systems uses a high power (1000 Watt) C0₂ laser in its Heart Laser™ with an articulated arm delivery system, such as that described in U.S. Patent No. 5,558,668 of Lankford, et al., assigned to PLC Medical Systems, Inc.

Primary distinctions between the use of Ho:YAG or excimer lasers and C0₂ lasers include that the C0₂ lasers can create a transmural channel with a single pulse synchronized with the R wave (beginning of contraction) of a beating heart. (An exemplary synchronization system is disclosed in U.S. Patent No. 5,125,926 of Rudko, etal.) The Ho:YAG and excimer lasers utilize low pulse energy and must fire multiple pulses over multiple cardiac cycles, typically without synchronization, in order to form a single channel. Another important distinction is in the delivery systems, with C0₂ based systems using articulated arms, supplying the laser energy in a non-contact manner, thus requiring higher power laser sources and more invasive access methods, e.g., open chest surgery. Distinctions also lie in the relative costs and reliability of C0₂ and excimer laser-based systems: Surgical C0₂ lasers are readily available, inexpensive and easily maintained, and many hospitals already possess or have access to such lasers. Excimer lasers are large, expensive, and difficult to maintain, requiring frequent service, and use highly toxic gas as the lasing medium. The precision required for safe and controllable formation of multiple small diameter channels in the myocardium suggests that a contact or near- contact methods for application of laser energy would be preferred. Further, the ability to utilize contact delivery methods enables the use of less invasive procedures for obtaining access to the heart, e.g., small incisions between the ribs (thoracotomy) as opposed to open chest surgery. However, according to TMR techniques currently in use, the advantages of contact delivery must be offset by the lower ablative energy provided by shorter wavelength (mid- or near-IR) light.

Other well-known surgical applications of lasers include cosmetic surgery. Many of these applications involve ablation of the skin by focusing a pulsed beam of light to impinge upon a small spot of skin, and scanning the beam in a pattern to cover the area to be treated. In such procedures, the sole mechanism is the ablation of tissue by highly-absorbed laser light, typically from a CO₂ laser. Because of its wavelength and power density, the CO₂ laser, while effective for tissue ablation, presents a risk of thermal damage to surrounding tissue which can lead to hypertrophic scarring. Other complications include hypopigmentation, dilated pores, postoperative hemorrhage, infection and excessive growth of granulation tissue.

In other aesthetic (plastic) surgery applications, lasers are generally not used to make the skin incision because the cold knife (scalpel) can make finer cuts than lasers, and such incisions will heal without leaving a scar. However, bleeding can be considerable, especially when highly vascular regions of the body, such as the face, are treated. Therefore, means for cauterizing and/or coagulation would be helpful in such procedures. Many other surgical procedures exist in which a combination of precision cutting and simultaneous coagulation would be advantageous. For example, in removal of brain tumors, it is critical to precisely remove the tumor tissue while leaving intact as much of the healthy tissue as possible.

The delivery system and method disclosed in the following written description and drawings addresses and overcomes the above-described deficiencies as well as providing other effective laser surgery techniques.

SUMMARY OF THE INVENTION

It is an advantage of the present invention to provide an optical delivery system and method which permits precise control of the location of impingement of optical radiation on biological tissue.

It is another advantage of the present invention to provide means for combining optical and mechanical means for simultaneous cauterization/coagulation and incision of biological tissue. Still another advantage of the present invention is to provide a system and method for minimizing thermal damage to tissue from optical radation which is used for surgical cauterization/coagulation.

Yet another advantage of the present invention is to provide a surgical blade for manipulating light during delivery of the light to a surgical site. The optical delivery system and method utilizes the combination of a thermally and optically conductive surgical blade with a light source. The light source, which can be a laser or a high power incoherent light source, provides light of a wavelength that is readily absorbed by water or hemoglobin in the blood at the incision site so that cauterization and/or photocoagulation is induced to reduce bleeding. Lasers that can be used in the present invention, which are typically low power, on the order of less than 20 watts, can include C0₂, excimer, various types of YAG, and diode lasers, which emit light within the wavelength range of 300 nm to 30 μm. The surgical blade is made from a material that transmits light to the incision site without significant absorption of energy which might heat the blade. Thus, the only heating of the blade results from contact with the heated tissue or blood. Shaping and directing optics can be integrated into the blade to focus, expand, or steer the incoming light beam as appropriate for specific surgical applications.

In an exemplary embodiment, the system and method of delivery of laser radiation comprises a flexible hollow waveguide connectable at a first end to a low power CO₂ laser source, a rigid hollow waveguide having a proximal end and a distal end, a coupler for coupling the second end of the flexible hollow waveguide to the proximal end of the rigid hollow waveguide and a light-transmissive optical tip partially disposed within and extending from the distal end of the rigid waveguide. The optical tip has an entrance face for receiving the laser radiation and at least one exit face for transmitting the radiation toward a target area of biological tissue. Means are provided for positioning the rigid hollow waveguide to direct movement of the optical tip and the light emitted therefrom. In an exemplary embodiment, the rigid hollow waveguide is a stainless steel tube with an inner diameter and a smooth, polished internal surface for reflection of the laser radiation. Other materials which meet the reflective and heat absorptive requirements for transmitting the laser radiation may be substituted for the stainless steel. The entrance end of the diamond tip has an outer diameter to closely fit within the inner diameter of the rigid waveguide, where it is brazed, glued or otherwise firmly affixed. The exit end of the optical tip can be flat, approximately parallel to the entrance face, or beveled, to create one or more blade edges to limit the point(s) of exit of the laser radiation and to provide a cutting edge which may be used in combination with the radiation to simultaneously create and cauterize an incision. Portions of the optical tip can be curved, to act as a lens or mirror, providing a focusing or expanding function, or to cause the output light to be emitted at an angle relative to the cutting edge. The diameter and emission location of the radiation leaving the optical tip can also be controlled by polishing only the desired exit area of the exit face, leaving the remainder of the tip material with a roughened or "frosted" surface which will reflect the majority of laser radiation back into the body of the tip so that it can be redirected out of the exit face. Alternatively, for more efficient internal reflection, the areas of the optical tip through which no radiation should escape may be bonded with a metal or ceramic coating which reflects the laser light.

In alternate embodiments, an optical tip can be affixed directly to the flexible waveguide without an intervening rigid waveguide; or in a self- contained handheld system, a small laser can be coupled through a short rigid waveguide directly to the optical tip, with no flexible waveguide. The delivery system may also incorporate an articulated arm containing mirrors at each joint ("knuckle") or the arm, obviating the need for a rigid or flexible waveguide. In a catheter-based system, an optical fiber (when using a UV or visible laser) or a small-diameter waveguide or specialized fiber (when using a far-IR laser, such as C0₂ ) could be utilized to couple the laser to a distal optical tip which could be retractable into the catheter. Other variations based will be apparent to those of skill in the art by taking into account the wavelength, method of access to the surgical site, and the specific surgical indication/procedure. The combination of the flexible waveguide, coupler, rigid hollow waveguide and optical tip may be used for formation of channels in a transmyocardial revascularization (TMR) procedure. Using a low power CO₂ laser (under 1000 Watts, preferably less than 100 W) emitting at 9.3 or 10.6 microns coupled via a flexible waveguide to a rigid waveguide/diamond tip assembly, the distal end of the assembly is guided to an area of the heart to be revascularized. The tip is preferably configured as a flat window or a slightly curved lens, i.e., a lens having a relatively long focal point which will not significantly modify the beam diameter or power density at close range. Placement of the tip at the desired location may be by catheter through one of the patient's major vessels, so that the ablation begins on the interior of the beating heart, or through a small incision in the chest wall, with the laser radiation being introduced outside-in, through the exterior (epicardial) surface. The optical tip is placed in direct contact with the tissue of the beating heart for delivery of ablative laser radiation for formation of a channel. The tip is advanced as the ablation proceeds to control the depth of the channel. In order to avoid arrhythmogenesis, it is preferred that the laser pulses be synchronized to the peak of the R-wave of the patient's ECG.

Monitoring of the minimally-invasive TMR procedure may be achieved using a three-dimensional image acquisition endoscope with a head-mounted display. This may be supplemented using an ultrasonic imaging endoscope inserted into the patient's esophagus, as is known in the art. Conventional heart rate monitoring techniques may be used to generate a trigger signal to synchronize delivery of the laser radiation with the heart beat. Monitoring of the catheter-based TMR procedure may be accomplished using conventional fluoroscopy/angiography, or may utilize more sophisticated electrical/mechanical mapping systems as are known in the art.

A similar delivery system in combination with a low power CO₂ laser may be used for performing left ventricular remodeling, utilizing the "Batista procedure" for severe dilated cardiomyopathy in which a section of the enlarged left ventricle is surgically removed to reduce the size of the heart and to increase pumping function. In a variation of the TMR embodiment, the diamond tip is formed as a blade which is frosted or otherwise treated to minimize escape of laser radiation everywhere except at the cutting edge. The cutting edge, in combination with the laser radiation, allows the simultaneous cutting of the heart tissue and photocoagulation of blood along the incision.

Treatment of otitis media by perforation of the eardrum (myringotomy) can be achieved by combining the delivery system as described for TMR with an otoscope to permit viewing of the tympanic membrane to properly position the perforation. Using a low power laser with the diamond tip held a short distance from, but not in contact with the membrane, an area of the tissue is denatured. Using a diamond tip shaped as a lance, or a diamond lens for focusing the laser to a small point, a small area of the denatured tissue is then punctured to provide a vent for pressure behind the eardrum. The puncturing is achieved by ablation, cutting, or a combination of both. After the pressure has been reduced, a larger perforation is made through the denatured tissue, leaving a rim of necrosis to delay healing of the perforation to provide improved patency, thus permitting the draining of fluids from the middle ear without requiring placement of a drainage tube.

Harvesting of skin graft tissue, removal of cancerous growth in skin cancer, and cosmetic surgery, including blepharoplasty, can be performed using a small lance blade, on the order of 3 mm, and a CO₂ laser (at 9.3- 10.6μm wavelengths). The blade is used for precision cutting while the laser light induces photocoagulation of blood and/or cauterization of the incision site, to significantly reduce blood loss. For all applications, the delivery system of the present invention allows adjustment of the laser power to obtain the degree of coagulation or cauterization desired.

BRIEF DESCRIPTION OF THE DRAWINGS Understanding the present invention will be facilitated by consideration of the following detailed description of preferred embodiments of the present invention taken in conjunction with the accompanying drawings, in which like numerals refer to like parts and in which:

Figure 1 is a diagrammatic view of the laser delivery system of the present invention;

Figure 2 is a side elevation, partially cut away, showing the rigid waveguide and diamond tip of a first embodiment of the delivery system;

Figures 3a-3d are diagrammatic views of alternative embodiments of diamond tips for use in the delivery system of the present invention, where Figure 3a shows a blade having one beveled edge, Figures 3b and 3c show alternate configurations of blades having two beveled edges, and Figure 3d shows a blade having four beveled edges;

Figures 4a and 4b are diagrammatic views of an alternative embodiment of the rigid waveguide, with Figure 4a being a side elevational view and Figure 4b being a top view;

Figure 5 is a diagrammatic view of the system for performing a TMR procedure;

Figures 6a-6d are diagrammatic views of a human heart, partially cut away at the left ventricle, showing the steps of a TMR procedure, where Figure 6a shows initial placement of the diamond tip, Figure 6b shows a channel partially formed in the myocardium, Figure 6c shows a completed channel and Figure 6d shows a plurality of completed channels and a partially completed channel;

Figures 7a and 7b are diagrammatic views of a human heart showing the steps of a PLV procedure, where Figure 7a shows formation of the incision around the wedge of tissue to be excised, and Figure 7b shows the heart after completion of the procedure;

Figures 8a and 8b are diagrammatic views of a tympanic membrane, where Figure 8a shows the first step of denaturing the tissue and Figure 8b shows the second step of perforating the tympanic membrane within the denatured area;

Figure 9 is a diagrammatic view of a partial cross-section of a human ear and an otoscope adapted for performing a myringotomy according to the present invention; and Figures 10a and 10b are diagrammatic views of surgical blades incorporating light-shaping optics, where Figure 10a illustrates a blade with a curved reflecting surface and Figure 10b illustrates a blade with a curved refracting surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As illustrated in Figure 1 , a surgical optical radiation delivery system for use with a light source 102 comprises a flexible waveguide 104 connectable at a first end 106 to light source 102, a rigid hollow waveguide 1 12 having a proximal end 1 14 and a distal end 1 16, a coupler 1 10 for coupling the second end 108 of flexible waveguide 104 to the proximal end 1 14 of rigid hollow waveguide 1 12 and a light-transmissive optical tip 120 partially disposed within and extending from distal end 1 16 of rigid waveguide 1 12. As can be seen in more detail in Figure 2, optical tip 120 has an entrance face 202 for receiving optical radiation and at least one exit 204 face for transmitting optical radiation toward an area of biological tissue. The rigid hollow waveguide 1 12 may include means for gripping in the user's hand to support and direct movement of the tip 120 and the light emitted therefrom, or may be combined with a steerable endoscope or catheter-based device to enable guidance. The light source, which can be a laser or a high power incoherent light source, provides light of a wavelength that is readily absorbed by water or hemoglobin in the blood at the incision site so that photocoagulation is induced to reduce bleeding. In particular, the heating of the blood stimulates the release of clotting enzymes. Lasers that can be used in the present invention, which are typically low power, on the order of less than 20 watts, can include CO₂, excimer, various types of YAG, and diode lasers, which emit light within the wavelength range of 300 nm to 30 μm.

Flexible waveguide 104 is preferably be constructed according to the disclosure of Harrington, etal. in Patent No. 5,567,471 , which is incorporated herein by reference. The waveguide of Harrington, et al. comprises a hollow tube of flexible, thin-wall silica-glass with a protective sheath on its outer surface. The inner surface of the tube is coated with a material that is optically reflective at mid-infrared wavelengths, such as silver, so that the coating is optically smooth. A dielectric film, such as silver iodide, is deposited on the reflective layer. The hollow waveguide as taught by Harrington, et al. is particularly useful when the light source is a CO₂ laser, due to the long wavelength of that laser. Other light sources having shorter wavelengths can be transmitted through an optical fiber or other waveguide, selection of which will be apparent to those of skill in the art. The rigid hollow waveguide 1 12 is a stainless steel tube with an inner diameter and a smooth, polished internal surface for reflection of the optical radiation. The inner diameter of waveguide 1 12 is preferably on the order of 1 .0 to 1.5 mm or less to provide greater control over the spatial profile of the output beam. The outer diameter is determined primarily by the materials used, to assure that the tube can be formed with a smooth internal surface without irregularities from creases or wrinkles which might disrupt the efficient transfer of optical energy. The outer diameter may also depend on any requirements for housing waveguide 1 12 within some other structure, such as a cannula or catheter. Other materials which meet the reflective and heat absorptive requirements for transmitting the optical radiation may be substituted for the stainless steel. Such materials include invar, nickel, platinum, and other high specific heat metals or alloys.

The entrance face 202 of tip 120 has an outer diameter to closely fit within the inner diameter of the rigid waveguide, i.e., on the order of 1.0 to 1.5 mm or less, where it is brazed, glued or otherwise firmly affixed, for example, by crimping the end of waveguide 1 12 around the tip 120. The surface of entrance face 202 is preferably flat, perpendicular to the axis of waveguide 1 12, and may be coated or bonded with an anti-reflective coating 210 such as silicon nitride or silicon carbide, as disclosed in Patent No. 5,194, 12 of Jones. The exit face 204 of the tip 120 may be flat, nearly parallel to entrance face 202, as shown in Figure 2, or beveled, as shown in Figures 3a-3d, to create one or more blade edges to limit the point(s) of exit of the optical radiation and to provide a cutting edge which may be used in combination with the radiation to simultaneously optically and mechanically cut and induce photocoagulation as the incision is made. (Note that, for purposes of this description, the phrase "mechanically cut" means the cutting performed using a sharp blade pressed against the tissue, while "optically cut" means removal or separation of tissue by laser ablation, regardless of whether the laser radiation is applied in a contact or non-contact manner.) At lower power levels, the system can be used to mechanically cut while providing simultaneous coagulation.

As in conventional diamond, sapphire or like surgical blades for mechanical cutting, multiple facets may be created to form, for example, a spear tip (using two facets), a triple edge (using three facets), or a "curved" tip (with four or more facets to approximate a rounded blade). Figure 3a shows a blade 300 with a single beveled edge 302. In this configuration, laser radiation would be emitted only through beveled edge 302, which is also the only cutting edge. Figure 3b illustrates a blade 304 with two beveled edges 306,308 to form a lance or spear. Both edges 306,308 can be used to cut, and apex 310 can be used to pierce. Laser radiation will be emitted through both beveled edges 306,308. Figure 3c shows an alternate two-edge blade 312 with beveled edges 314,316. Edge 314 is long and may be used for larger-area slicing, with apex 318 for piercing. Figure 3d illustrates a "curved" blade 320 with four beveled edges 324,326,328,330 formed at the distal end of the blade.

The size of the blade to be used will depend on the procedure, and will dictate, to some extent, the laser power required. Smaller blades will be used for surface procedures, such as cosmetic and skin surgeries, such as those described herein, where mostly small blood vessels are encountered. A typical blade will be a 3 mm lance-type blade, and the light source will be a 4-10 W CO₂ laser. Here, the clotting mechanism is heating of water in the blood. When working in areas of larger vasculature, the light source will preferably emit in the near IR region (around 0.8-1 .1 μm), such as is possible with certain diode lasers, Nd:YAG, and other YAG lasers. For deep tissue work, blades with larger surface areas are necessary, which requires higher input powers, generally in the 2-80 W range. In these cases, heating of the blood, and coagulation, is stimulated by absorption of light by hemoglobin.

The diameter and emission location of the radiation leaving the tip may be further controlled by polishing only the desired area of the exit face, leaving the remainder of the with a roughened or "frosted" surface which will reflect the majority of optical radiation back into the tip so that it can be re-directed out of the exit face. Alternatively, for more efficient internal reflection, the areas of the tip through which no radiation should escape may be bonded or coated with a metal or ceramic film. In the embodiment of Figure 2, the sidewalls 206 of tip 120 are treated with internally reflective coating 208 to minimize escape of optical radiation. In Figures 3a-d, all areas but the beveled edges may be treated to enhance internal reflection and guide the optical radiation toward the beveled edge. The beveled edges are formed in accordance with conventional techniques for forming surgical diamond cutting blades, in which a facet is formed at the cutting edge. Alternative means for maximizing and/or directing internal reflection of the light can include formation of refracting or reflecting surfaces within the blade. Figures 10a and 10b illustrate exemplary configurations of optical elements integrated into the blade structure for expanding the incoming light for emission through the cutting edge.

As shown in Figure 10a, incident beam 846 enters through entrance face 848 of tip 842. Upon entry, it is refracted slightly due to the change in refractive index, then strikes curved reflecting surface 844 which is disposed at an angle relative to entrance face 848 and to incident beam 846. The convex curvature of reflecting surface 844 causes exit beam 850 to diverge as it passes through exit face 852, here shown as a beveled cutting edge. By making reflecting surface 844 concave, beam 850 could be focused to a smaller portion of exit face 852.

In Figure 10b, an alternate means for expanding the beam is provided by directing incident beam 858 through curved (concave) refracting surface 856 formed on the surface of entrance face 860 of tip 854. The combination of the change in refractive index of the tip and curved surface 856 expands beam 868, which reflects off of flat internal reflector 866, disposed at an angle relative to the optical path of incident beam 858, and continues to diverge as it exits as beam 862 through exit face 864, shown as a beveled cutting edge. As above, a smaller exit beam can be formed by forming refracting surface 856 with a convex lens instead of a concave lens. In the embodiments of both figures 10a and 10b, the angle of the internal reflector can be changed to modify the direction of the exit beam as it passes through the exit face.

The dimensions of such surgical blades are generally appropriate for use in combination with the optical delivery system. For example, the base end of a commercially-available surgical blade manufactured by Drukker International BV, Cuijk, The Netherlands) may have a width in the range of 0.7 to 1.4 mm and a thickness of 0.17 mm, such that it would easily fit within the interior of the hollow waveguide 1 12. It may be preferable to form the base end of the blade to have an entrance face with a shape and an area that just fits within the cross-sectional shape and area of the hollow waveguide to enhance efficiency in capture of the optical radiation incident upon the entrance face and to minimize diffraction losses where the optical radiation impinges upon a corner or edge of the entrance face. Thus, if the hollow waveguide is rounded, the entrance face is preferably rounded. Since it may be easier to form the base of a diamond blade with a rectangular or square cross-section, the hollow waveguide may be crimped or otherwise modified to create a corresponding rectangular or square cross-section at its interior with approximately the same cross-sectional area as the base of the blade. Alternatively, the hollow waveguide could be configured with a square or rectangular cross-section along its entire length. Commercial diamond blades can range from 0.25 mm down to less than 35 microns in thickness with widths on the order of 1 mm or less. A modification for accommodating an exemplary commercial diamond blade is illustrated in Figures 4a and 4b, showing a hollow waveguide 400 with a circular cross-section at proximal end 402 and a rectangular cross-section at distal end 404 to match the rectangular shape of the base 406 of diamond blade 408. The transition 410 from circular to rectangular cross-section is made as gradual as possible to retain the smooth internal surface to minimize scattering loss and mode conversion. With the laser radiation being emitted only from beveled edge(s) 412, the edge can simultaneously cut the tissue and coagulate the blood at the incision. Unlike methods of the prior art, the optical radiation, whether from a laser or incoherent source, is not used to heat the blade to create a "hot knife", but rather, it is absorbed by the blood at the incision site which stimulates the clotting mechanism, thus significantly reducing bleeding at the incision. For CO₂ lasers, absorption is primarily by water, which causes the blood to heat locally. For other lasers and light sources, the wavelength emitted by the optical source is preferably selected as one that is absorbed by hemoglobin, which includes UVA, blue, green and yellow. The only heating that is experienced by the blade is from the blood localized at the incision. Therefore, thermal damage to surrounding tissue which can occur when optical absorption of light is the sole cutting mechanism is also avoided. Diamond tips are preferably formed using a single crystal natural diamond, which, ideally, is a type Ma diamond. Type Ma diamonds are effectively free from nitrogen impurities and have enhanced optical and thermal properties. Other types of diamonds may be used provided that they possess the thermal and optical characteristics required to efficiently transmit infrared laser radiation while tolerating thermally-induced stresses and strains. Type lb diamonds (most synthetics) and polycrystalline diamond films manufactured by chemical vapor deposition (CVD), e.g., DIAFILM™ available from De Beers Industrial Diamond Division, Berkshire, England, may also be used. In addition to the use of diamond, other materials that are thermally conductive, strong and hard, and are also suitable for fabrication into a window or blade can be used in the present invention. Table 1 provides an exemplary list of materials that are optically transparent at potential treatment wavelengths, along with relevant properties of the materials. This list is not exhaustive and is not meant to exclude other suitable materials. The transparent dielectric materials are better than, or similar to, the better steels used in similar laser delivery systems and can be made from either natural or synthetic materials. Whether natural or synthetic, suitability for use as blade material will typically depend more on the presence of impurities rather than on the origin of the material.

Table 1

1. Aluminum Oxynitride

2. Alexandrite

3. Yttrium aluminum garnet

Surface modifications can be made to the blade to prevent it from sticking to tissue being cut. The ionic bonding or plasma deposition of nonstick coatings, for example monomers of Teflon^®, to the blade material makes the surface of the blade smoother and less chemically reactive to substances it might contact. The coating, generally f luorocarbon in composition, prevents the adherence of coagulated blood and tissue to the blade during surgical procedures.

The delivery system of the present invention can be used in a TMR procedure for formation of channels in the myocardium. Such as system overcomes the limitations that exist in the prior art by combining a contact delivery system with the greater ablation capability afforded by using, in the preferred embodiment, the CO₂ (far-IR) laser as a source. An exemplary system is illustrated in Figure 5. The distal end 516 of hollow waveguide 512 is fitted with diamond tip 520 configured as a flattened or slightly curved lens at exit face 524. Hollow waveguide 512 is axially slidably retained within channel 502 of an endoscope 500 so that it may be extended from at least partially retracted into the housing 530. Housing 530 may also contain means for performing one or more other functions in addition to retaining the waveguide 512 and diamond tip 520. At least a portion of flexible waveguide 510 is also retained within endoscope 500. The proximal end 536 of waveguide 510 is attached via connector 538 to laser 526.

In the preferred embodiment, housing 530 also retains a plurality of axially-running control lines 532 which are attached at the distal end 502 for guiding the endoscope 500, as is known in the art, and a plurality of optical fibers 504, a first portion of which provide a source of visible illumination and a second portion of which provide visual feedback to the surgeon in the form of a three dimensional image. The three dimensional image, which is computer-enhanced using the images obtained via the optical fibers 504, is viewed using a binocular head mounted display 506 which is worn by the surgeon to provide real-time visual feedback in a minimally invasive surgical procedure. A three dimensional endoscope system is disclosed and described in International Patent Application Publication Number WO 94/28783 of American Surgical Technologies Corporation, the disclosure of which is incorporated herein by reference. One such commercial three-dimensional viewing system is available as the Vista Series 8000 Visualization and Information System, which incorporates the CardioScope™, for image acquisition, and CardioView™, for the head-mounted display, manufactured by Vista Medical Technologies, Vista Cardiothoracic Surgery Division, of Westborough, Massachusetts.

Briefly, the three-dimensional image is produced by a conventional stereoscopic endoscope 500 which converts optical images of an object, in this case, the patient's heart, to left and right video image signals. Conversion of the two-dimensional optical images into left and right signals is achieved using a camera head 514 connected to a video processing module 515. After processing, the images are displayed on the left and right lenses 518,520 of the head mounted display 506. The lenses 518,520 may be liquid crystal displays (LCDs), such as described in U.S. Patent 5,532,852 of Kalmanish, or may be passive displays as described in above-referenced International Publication No. WO 94/28783. Visual monitoring of the procedure may be supplemented using known techniques of ultrasonic imaging by placing a ultrasonic probe within the patients esophagus. (See, e.g., I. Kupferwasser, et al., "Quantification of mitral valve stenosis by three-dimensional transesophageal echocardiography", Intl J. Cardiac Imag., 12:241 -247, 1996.)

Synchronization of the laser activation with the R waves of the electrocardiogram (ECG) signal utilizes a conventional ECG device 522 which is connected to a trigger pulse generating device 524. The trigger pulse is passed to a laser firing circuit which activates the laser 526 on the R wave of the electrocardiographic cycle, when the ventricle is maximally distended. An exemplary synchronization system is disclosed in U.S. Patent 5,125,926 of Rudko, et al.

Referring to Figures 6a-6d, the method for performing a TMR procedure comprises making one or more small left anterior incisions (thoracotomies) through the fourth, fifth or sixth intercostal space to provide access to the left ventricle area of the heart 602. The distal end 609 of an endoscope 606 retaining flexible waveguide 607, hollow waveguide 608 and diamond tip 610 is inserted through and fed into incision 612 (indicated by dashed lines) until the tip 610 comes in contact with the pericardium 614. Endoscope 606 is configured such that it also retains the viewing optics, including illumination means, for providing a three-dimensional image for viewing using head- mounted display 616, which is described above with regard to Figure 5. It also may include guidance means, such as control lines running axially along the length of the endoscope for manipulating the distal end 609 of the endoscope. Such guidance means are known in the art. Alternatively, the viewing optics may be housing within a separate endoscope which is inserted through a separate incision near incision 612.

As illustrated in Figure 6a, which shows the system set-up, the patient's ECG is monitored using an ECG device 618 which provides a trigger signal for activating CO₂ laser 620 in synchrony with the R wave 619, as indicated on ECG output display 621. Upon triggering, laser 620 emits a pulse of low power 10.6 micron laser light, i.e., less than 1000 W and preferably having a power within the range of 25-50 W, with a beam diameter of approximately 1 mm. (Generally, the laser should have a power density of greater than 5000 W/cm².)

In Figure 6b, which illustrates portions of both the heart 602 and overall system components, the distal end 607 of endoscope 606 is indicated by dashed lines to show the relative movement of the diamond tip 610 for advancing the tip into the heart tissue. It should be noted that, where the viewing and lasing components are housed in a common endoscope, distal end 607 is positioned to achieve the desired depth of view based upon the viewing optical components, since tip 610 can be advanced as needed relative to the distal end 607. The laser light emitted through diamond tip 610 in contact with the pericardium 614 ablates the tissue, providing a point of entry without tearing the pericardial tissue, and allows the tip 610 to be advanced into the myocardium 622. Triggered by detection of another R wave, the laser radiation ablates the myocardial tissue with which the tip 610 is in contact. As the myocardial channel 624 is formed, the tip 610 is advanced until the channel extends through the myocardium 622 and the endocardium 626 and, finally, the tip 610 extends into the left ventricle 628, as shown in Figure 6c. In prior art TMR systems based on high power CO₂ lasers, "overshoot" after the channel is fully punched through the heart wall is controlled by blood contained within the left ventricle, since the water in the blood will absorb the radiation. However, such reliance may be risky and could result in damage to the opposite inner wall of the left ventricle, or could create blood clots (thrombus) which occlude distal vessels, potentially resulting in stroke or other ischemic insult. In the present method, since the ablation is advanced gradually, there is no "overshoot" with an uncontained high power laser beam. Stop 632, shown only in Figure 6c, may be disposed within endoscope 606 to limit the travel of tip 610 by preventing flange 634 from advancing further, thus providing even greater control and accuracy in the application of the laser radiation. If such a stop is utilized, the length of hollow waveguide 608 should be sufficient to allow tip 610 to pass completely through the myocardium 622 and enter the left ventricle 628. The tip 610 is then backed out through the channel 624 and another channel is begun at a different point on the outer wall of the left ventricle. Figure 6d shows three completed channels 624 with another one in the process of being formed. As is known in the TMR art, a number of channels are formed, typically on the order of 15 to 40 channels spaced about 1 cm apart in a grid-like array, with diameters of about 1 mm, to provide the desired improvement in myocardial perfusion.

Since multiple applications of the laser radiation are required to create each channel, activation of the laser may be triggered by the R wave for every n beats, depending on the patient's heart rate. For example, for a rate of 60 beats/minute, n might be selected to be 5, 10, or some other integer value. Consideration may also need to be given to how long the laser requires between pulses, with the triggering rate being set to a value corresponding to a period equaling an integer times the heart rate which is greater than the laser recharge cycle. The pericardium 614 may provide a relatively high amount of initial resistance due to its density. Therefore, as an alternative to the flat or slightly rounded tip, it may be desirable to utilize a lance or spear-type diamond tip, such as that illustrated in Figure 3b, to facilitate perforation of the pericardial tissue. The pulsed nature of the laser causes disruption of tissue along fractures perpendicular to the channel, causing angiogenesis in myocardial tissue up to 10 mm away from the channels, which close within 2-6 weeks.

Variations in the TMR procedure with the inventive system can be utilized, based upon the method of obtaining access to the myocardium. In one alternative method, the heart is accessed through catheters placed in the patient's femoral artery and passed through the aorta 630, which can be seen in Figure 6a, across the aortic valve and into the left ventricle 628. Using this method, perforation of the pericardium 614 is not required, and the channels are created in the myocardium 622 to a pre-determined depth. In another alternative method, access is gained in an open chest procedure via a sternotomy or thoracotomy. As in the first method, the diamond tip is initially placed in contact with the pericardium 614, and the channels are formed completely through the myocardium 622.

Because the CO₂ laser radiation is delivered by contacting the tissue, the optical components of the system can be simplified as compared to conventional CO₂ laser-based TMR systems, which require an additional laser, typically helium-neon (He-Ne), which emits a visible red light (632.8 nm), with corresponding optics, for aiming purposes. In the present invention, contact, and thus, aiming, is readily monitored using the images generated by the 3-D endoscope 606 and viewer 616. As previously mentioned, esophageal ultrasonic imaging may also be used to monitor the positioning of the device and the progress of the procedure. Fluoroscopy (angiography) can also be utilized to determine the location of the distal tip of the endoscope and guid the positioning of tip 610.

An important advantage of the present invention is that, because of its low power requirements, it may be used with virtually any C0₂ laser head, including retrofitting of a CO₂ laser which may already be available within the hospital. This provides greater access to TMR capability for hospitals which may not have the budget for purchasing dedicated TMR systems, which systems cost well over $200,000, and makes it possible to perform the procedures more cost effectively. The contact procedure allows the power level to be significantly lower than that required for non-contact CO₂ laser- based systems, which require power levels of 800 W and up in order to supply sufficient energy to create a complete channel in a single pulse. (A non-contact TMR system must create the channel in a single pulse since exact positioning of a subsequent pulse at the same point may be difficult on the beating heart.) The contact delivery system of the present invention allows for greater precision and improved safety, while providing a more economical means for performing TMR procedures.

In an alternate embodiment, the laser delivery system of the present invention may be used to perform a partial left ventriculectomy (PLV), also known as the Batista procedure, for removal of myocardium for treatment of severe dilated (hypertrophic) cardiomyopathy. The same low power CO₂ laser may be used as that used for the TMR procedures. Other types of lasers, such as Ho:YAG or Nd:YAG may be used, however, the advantages of cost savings with the low power CO₂ laser may not be available. The diamond tip used for the delivery system will have at least one cutting edge, and may be any of the configurations shown in Figures 3a-3d, or variations thereupon.

The method of performing a PLV using the inventive system comprises providing access to the heart by way of a sternotomy or thoracotomy. It may be preferred to utilize recently reported systems and procedures for minimally invasive surgery, such as the system developed by CardioThoracic Systems, Inc. of Cupertino, California under the trademark MIDCAB™. Such systems permit access to the heart through an incision through one of the left intercostal spaces. Spreaders are used to increase the spacing between a pair of ribs to provide a surgical window to the heart.

The patient is placed on a heart-lung bypass machine. The heart continues beating in order to permit identification of the area to be removed. As illustrated in Figure 7a, using the inventive laser delivery system with a low power C0₂ laser 700, typically on the order of 25-50 W, the diamond tip 702, shown here with two beveled edges 704,706, is retained within hollow waveguide 730 and is used to simultaneously cut and irradiate tissue in the wall of the left ventricle 708 between the papillary muscles (not shown) to remove a wedge of tissue 710. The laser radiation is emitted through edges 704,706 to facilitate cutting, particularly through the pericardium 712, and to induce photocoagulation of the tissue as the incision is made through the myocardium 714 and endocardium 716 thus greatly reducing blood loss. The stippling at the incision through the myocardium 714 is provided to indicate photocoagulated tissue. The dotted line indicates the intended line of incision 720. After the wedge of tissue 710 is removed, the edges 718, 720 of the incision are pulled together and sutured to form a smaller left ventricle, as shown in Figure 7b, with thicker walls. The stippling at the joined incision again indicates photocoagulated tissue of the pericardium 712. The heart-lung machine is removed, and the thoracic incision is closed.

Other types of lasers may be substituted for the low power C0₂ laser in this procedure in order to provide photocoagulation/cauterization of the tissue as the incision is made mechanically with the diamond blade. Alternative lasers include Ho:YAG, Nd:YAG, and solid-state (diode), all emitting within the range of 300 nm to 30 μm. Other lasers are known for their photocoagulation capabilities, including argon, krypton and Er:YAG. Generally, the laser power will be fairly low, less than 100 W, with most applications using powers of less than 20 W. The vast majority of procedures will require only 2-4 W.

In addition to laser light sources, high-power incoherent light sources can be used, in conjunction with spectral filtering to limit the emitted wavelength to avoid absorption of energy by chromophores in the blood. If the local heating of the blood is not intended to be accomplished through water absorption, filters should be selected to prevent transmission of light that is absorbed by chromophores other than hemoglobin. An example of an appropriate light source is the Model No. EX500-13F CERMAX^® Focused Xenon Arc Lamp manufactured by ILC Technology. Before the addition of any filtering, it has a radiant output of 1 12 W including 5 W in the UV range (wavelength <390 nm) and 65 W in the IR range (wavelengths > 770 nm), forming a spot of about 1 .8 mm diameter. Using optical techniques known to those of skill in the art, using appropriate filtering, a sufficient fraction of this power can be coupled, in spectrally selective fashion, into a high-power multimode optical fiber (e.g. 500 μm step-index fused silica) that will, in turn, couple well into an optically-transmissive blade.

The optical delivery system of the present invention provides several advantages over current PLV techniques. These advantages includes reduced tearing of the heart tissue resulting from conventional steel blade knives or surgical scissors, since the diamond blade has a much cleaner, sharper edge, which produces less cell damage, and the laser radiation can augment the mechanical cutting with ablation, at least with the CO₂ laser, and induces photocoagulation to reduce bleeding as the cut is made with the C0₂ laser as well as many other types of laser. These advantages, in turn, reduce the time in surgery and the risk of post-operative bleeding, and contribute to faster healing.

A third embodiment of the inventive laser delivery system may be used for performing a myringotomy for treatment of otitis media. In this case, two different diamond tips may be used. The first diamond tip 802 mounted within hollow waveguide 804, shown in Figure 8a, is configured as an expanding lens which slightly enlarges the diameter of beam 816 from a low power C0₂ laser 814, e.g., 25-50 W, to irradiate an area 806 on the tympanic membrane 808, preferably, but non-necessarily non-contact (for the patient's comfort), resulting in the denaturing of the tissue in the area 806. The denaturing is indicated by stippling. A hollow waveguide with a second diamond tip 810, shown in Figure 8b, is then attached to the distal end of the waveguide 812 connected to the CO₂ laser 814 to complete the procedure. Second diamond tip 810 may be configured as a focusing lens, a flat window, or a lance-type blade as shown. The key to second diamond tip 810 is that it generates a narrower, more focused beam than that delivered by first diamond tip 802 so that a smaller area of impact is defined on the tympanic membrane 808 with a correspondingly-higher power density. The smaller, diameter, higher power density beam is then used to ablate a small perforation 818 generally at the center of the area of the denatured tissue 806 so that a rim 820 of denatured tissue remains around the perforation. This latter aspect of the procedure is preferably performed in two steps. The first step is that a small "vent" hole is formed to release any pressure that has built up behind the tympanic membrane which could otherwise lead to bursting of the membrane if it were suddenly perforated. After the pressure has been equalized, a larger perforation is formed to provide the desired drainage. The small vent hole may be created by gently pushing the tip 822 of the lance blade 810 against the membrane, then backing the blade away from the tissue to allow the pressure release. The desired, larger perforation 816 can then be created by a combination of mechanical pressure from the blade 810 and the laser ablation, or by either alone.

The rim of denatured tissue 820 retards the healing of the perforation, giving it extended patency. This eliminates the need for placement of a shunt tube for drainage such as is required in most current myringotomy procedures. Observation and control of the myringotomy procedure using the inventive system may be achieved using conventional viewing optics including an otoscope 830 with an illumination source 832, illustrated in Figure 9 along with a section of an ear 840. Illumination source 832 may double as the targeting means, and, in this case, is shown as a He-Ne laser along with the appropriate optics for directing the beam 834 from the He-Ne laser 832 along substantially the same optical path as, or to convergence with, the ablation laser 814.

The myringotomy procedure is not limited to the wavelength emitted by a CO₂ laser, and a wide range of laser wavelengths may be used, including lasers emitting in the near- and mid-IR, including Ho:YAG, and near-UV ranges, such as excimer. The only requirement is that the laser radiation must be sufficient to achieve adequate denaturing of the tissue as required for extended patency of the perforation.

The described myringotomy procedure takes advantage of the benefits of laser ablation and other laser/tissue interactions without requiring the complex optical systems taught by others in the art. For example, Patent No. 5,280,378 of Lombardo describes a cyclically scanned laser for use in myringotomy procedures. The scanned beam forms many tiny holes in the tympanic membrane to outline an area which can then be punched through at the perforations. In that procedure, the laser is used only for cutting/piercing, and no intentional denaturing occurs. Thus, the patency of the perforation is not improved significantly relative to mechanical lancing procedures and a shunt will still be required.

Another implementation of the inventive laser delivery system can be used for performing a variety of cosmetic and reconstructive surgical procedures. In such cases where surgery is to be performed on or around the eyes and nose, where the skin is particularly thin and delicate and prone to bruising, the prevention of bleeding and scarring is an important consideration. The present invention provides both precision cutting and cauterization and/or coagulation to performing, e.g., blepharaplasty and harvesting of skin for grafts.

Four-lid blepharoplasty is an operative procedure performed on the upper and lower eyelids to correct droopy eyelid skin and bags under the eyes. In blepharoplasty, the final cut rests in the fold of the eyelid. Scarring at this incision site must be kept to an absolute minimum in order to prevent the possibility of Cicatricial Ectropion, a condition that results in the pulling of the upper or lower eyelid away from the eye.

For use in the blepharoplasty procedure, the inventive laser delivery system includes a 9.3-10.6 μm CO₂ laser at low power, typically around 4-10 W, and a small lance blade with a 3-10 mm cutting surface. This combination is preferable for surgical procedures involving small blood vessels, such as those of the skin around the eyes and nose. The use of the small blade affords the practitioner more precision in cutting as well as better tactile feedback and controlled cauterization of small blood vessels, thus minimizing bleeding. The low power of the laser assures that there will be less thermal damage to the delicate tissue of the eyelids. In procedures using the inventive laser delivery system in blepheroplasty procedures, the epidermis and dermis of the eyelid shows minimal coagulative change and vascular damage, thus facilitating more rapid revascularization at the surgical site. Surgical procedures involving the harvesting or repair of tissue as in full thickness skin grafts, whether as a result of severe burns or the excision of basal cell cancers, benefit from the use of the optical delivery system of the present invention. Full thickness wounds can only regenerate from the edges, making it necessary to provide the patient with skin grafted from other areas of the body (autograft) in order for the wound to be closed. Using the inventive system with a low power (2-20 W) CO₂ laser and an appropriate size blade (e.g. 8 mm, depending on the surface area to be cut), the harvesting of skin grafts can be performed with minimal blood loss and trauma to the tissue. Other benefits of the inventive optical delivery system include the increased speed in which the graft can be harvested and, thus, applied to the wound, minimizing the risk of introducing airborne contaminants, which is a critical factor in cases of serious burns. Minimized trauma to the graft tissue allows for improved re-epithelialization and faster revascularization, both of which are paramount to the recovery of the patient. The precision cutting ability provided by the optical delivery system of the present invention is also beneficial in obtaining biopsies using microscopic- oriented histologic surgery ("MOHS"), where thin layers of a suspected melanoma are removed and analyzed by a pathologist to determine the depth of tissue removal necessary to completely excise the melanoma. Other examples of reconstructive or cosmetic surgical procedures that benefit from the inventive optical delivery system include, but are not limited to, hair transplantation, abdominal foreflap surgery (abdominoplasty) and existing scar reduction. In hair transplantation, hair "plugs" are excised from areas of the scalp in which healthy hair follicles are plentiful and then transplanted into a "recipient hole" on an area of the scalp where more hair is desired. The use of low power laser cutting devices provides the practitioner with a means for creating the recipient holes rapidly with minimal bleeding. Further, there is minimal thermal damage to the hair follicles surrounding the recipient area. In abdominal foreflap surgery as well as any reconstructive or cosmetic surgical procedure, the minimization of blood loss and tissue trauma at the surgical site is vital to patient comfort and recovery. Additionally, minimized tissue trauma translates to less scarring which ultimately improves patient outlook.

Still another application of the optical delivery system of the present invention is the excision of brain tumors, where precise control is required to minimize the amount of tissue excised while ensuring complete removal of the tumor tissue. This is particularly important when removing tumor tissue in close proximity to critical structures, such as in treatment of acoustic or optic neuromas, and surgery of the spinal cord. The present invention has been demonstrated to limit damage to only 6-7 cell layers, compared with 30-40 cell layers when used a conventional electro-surgical cutter. The advantages of the present invention also allow liver, spleen, kidney and pancreas vascular beds to be coagulated while tissue is being resected, such as for tumor removal, or in organ transplantation. The laser delivery system of the present invention provides means for precise control of surgical lasers and other light sources, allowing the safe usage of inexpensive conventional lasers and light sources for advanced optical surgical techniques. The delivery system allows hospitals and physicians to avoid the significant expense involved in purchasing new, dedicated laser surgical systems when they already have access to CO₂ lasers which were part of an older and possibly out-of-date surgical system. The combined laser and mechanical surgical techniques which are enabled by the low power levels allow surgeons to exploit the benefits of each technique without compromise, providing significant advantages over prior art laser surgical systems. Surgical procedures to which the inventive system and method can be applied are myriad, and include, but are not limited to, transmyocardial revascularization, partial left ventriculectomy, myringotomy, organ transplant, cancer excision, skin grafting, and various cosmetic surgery procedures, including blepheroplasty and hair transplantation, among others. Generally, because of its ability to simultaneously cut the tissue and coagulate the blood at the site of the incision with minimal damage to surrounding tissue, the inventive system and method can be applied to any surgery performed in a vascular area.

It will be apparent to those skilled in the art that various modifications and variations can be made in the system and method of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modification and variations of this invention provided they come within the scope of the appended claims and their equivalents. WE CLAIM:

Claims

1. An optical surgical system, the system comprising: a light source having an output for emitting light at a wavelength adapted for absorption in and local heating of blood, the light emitted by the light source having a power level; a waveguide having a proximal end, a distal end and a first length, the proximal end attached to the output of the light source; and an optically-transmissive tip having a base end with an entrance face, at least one internally reflecting surface, and at least one exit face comprising a cutting edge, the base end adapted to be retained within and extend from the distal end of the waveguide, wherein the light energy is emitted from the exit face so that when the cutting edge cuts tissue at an incision site, energy from the light is absorbed by the blood at the incision site, wherein the power level of the light is selected to generate heat at the incision site to stimulate coagulation of the blood.

2. The optical surgical system of claim 1 , wherein the at least one internally reflecting surface in the optically-transmissive tip comprises a curved reflecting surface disposed at an angle relative to the entrance face.

3. The optical surgical system of claim 2, wherein the curved reflecting surface is convex.

4. The optical surgical system of claim 1 , wherein the entrance face has a lens formed therein for refracting the light.

5. The optical surgical system of claim 1 , where the waveguide comprises a rigid waveguide formed from a hollow metal tube having a polished interior surface, and an interior cross-sectional area.

6. The optical surgical system of claim 1 , wherein the waveguide comprises a flexible waveguide.

7. The optical surgical system of claim 1 , wherein the waveguide comprises a combination of a flexible waveguide and a rigid waveguide, wherein the rigid waveguide is attached to a distal end of the flexible waveguide and the optically-transmissive tip is attached to a distal end of the rigid waveguide.

8. The optical surgical system of claim 1 , wherein the lens is concave.

9. The optical surgical system of claim 1 , wherein the optically- transmissive tip is formed a material that is transparent at the wavelength emitted by the light source.

10. The optical surgical system of claim 6, wherein the material selected from a group consisting of diamond, silicon carbide, sapphire, aluminum oxynitride, chrysoberyl, spinel, yttrium aluminum garnet, cubic zirconia, silicon and -quartz.

1 1 . The optical surgical system of claim 1 , wherein the at least one exit face comprises two beveled edges that are disposed at angles relative to each other to form a point.

12. The optical surgical system of claim 1 , wherein the at least one exit face has a non-stick coating formed thereon.

13. The optical surgical system of claim 12, wherein the non-stick coating is formed through ionic bonding or plasma deposition on the at least one exit face.

14. The optical surgical system of claim 12, wherein the non-stick coating comprises monomers of Teflon^®.

15. The optical surgical system of claim 1 , wherein the light source is a laser.

16. The optical surgical system of claim 15, wherein the laser is selected from the group consisting of CO₂, excimer, Nd-YAG, Er-YAG, argon ion, krypton ion, and diode lasers.

17. The optical surgical system of claim 15, wherein the laser emits light within a wavelength range of 300 nm to 30 μm.

18. The optical surgical system of claim 16, wherein the laser emits light at a wavelength that is absorbed by water in the blood.

19. The optical surgical system of claim 16, wherein the laser is a CO₂ laser and the light has a wavelength within the range of 9.3-10.6 μm.

20. The optical surgical system of claim 16, wherein the laser emits light at a wavelength that is absorbed by hemoglobin in the blood.

21 . The optical surgical system of claim 14, wherein the laser emits light having a power less than 100 W.

22. The optical surgical system of claim 21 , wherein the laser emits light at less than 20 W.

23. The optical surgical system claim 1 , wherein the light source is an incoherent light source.

24. The optical surgical system of claim 1 , wherein the incoherent light source is a focused xenon arc lamp.

25. A method for performing a surgical procedure which includes creating an incision in tissue, the method comprising: providing a light source for emitting light at a wavelength that can be absorbed by blood to stimulate coagulation; connecting the light source to an optically-transmissive tip having an internally-reflecting surface and a cutting edge, wherein substantially all light energy entering the tip is transmitted out of the cutting edge; cutting the tissue with the cutting edge and simultaneously activating the light source so that the light stimulates coagulation of blood at the incision.

27. The method of claim 25, wherein the tissue is selected from the group consisting of skin, muscle, and organs.

28. The method of claim 25, wherein the light source is a laser emitting light at less than 100 W.

29. The method of claim 25, wherein the optically-transmissive tip is formed from a material selected from the group consisting of diamond, silicon carbide, sapphire, aluminum oxynitride, chrysoberyl, spinel, yttrium aluminum garnet, cubic zirconia, silicon and α-quartz.

30. The method of claim 25, wherein the internally-reflecting surface is a curved reflector disposed at an angle to the light entering the tip.

31. The method of claim 25, wherein the optically-transmissive tip has an entrance face having a lens formed therein for shaping the light entering the tip.

32. The method of claim 25, wherein the optically-transmissive tip has two cutting edges disposed at an angle relative to each other to form a point.

33. The method of claim 25, wherein the tissue is skin surrounding the eyes and the surgical procedure is a blepharoplasty.

34. The method of claim 25, wherein the tissue is skin and the surgical procedure is harvesting of skin for a skin graft.

35. The method of claim 25, wherein the tissue is skin and the surgical procedure if microscopic-oriented histologic biopsy of the skin.

36. The method of claim 25, wherein the tissue is skin and the surgical procedure is reconstructive, plastic or aesthetic surgery.

37. The method of claim 25, wherein the tissue is skin and the surgical procedure is hair transplantation.

38. The method of claim 25, wherein the tissue is a vascular organ and the surgical procedure is a resection of at least a portion of the organ or excision of a tumor within the organ.

39. The method of claim 25, wherein the surgical procedure is organ transplantation and the tissue is from the group consisting of heart, lung, kidney, pancreas, and liver.

40. The method of claim 25, wherein the tissue is myocardium and the surgical procedure is resection of a portion of the myocardium to treat cardiomyopathy.

41. The method of claim 25, wherein the tissue is myocardium and the surgical procedure is transmyocardial revascularization.

42. The method of claim 25, wherein the tissue is myocardium and the surgical procedure is a partial left ventriculectomy.

43. The method of claim 25, wherein the tissue is tympanic membrane and the surgical procedure is myringotomy.