Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
  • A61B18/18—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
  • A61B18/20—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser
  • A61B18/22—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser the beam being directed along or through a flexible conduit, e.g. an optical fibre; Couplings or hand-pieces therefor
  • A61B18/24—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser the beam being directed along or through a flexible conduit, e.g. an optical fibre; Couplings or hand-pieces therefor with a catheter
  • A61B18/245—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser the beam being directed along or through a flexible conduit, e.g. an optical fibre; Couplings or hand-pieces therefor with a catheter for removing obstructions in blood vessels or calculi
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
  • A61B18/18—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
  • A61B18/20—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser
  • A61B18/22—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser the beam being directed along or through a flexible conduit, e.g. an optical fibre; Couplings or hand-pieces therefor
  • A61B18/26—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser the beam being directed along or through a flexible conduit, e.g. an optical fibre; Couplings or hand-pieces therefor for producing a shock wave, e.g. laser lithotripsy
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B2017/00017—Electrical control of surgical instruments
  • A61B2017/00137—Details of operation mode
  • A61B2017/00154—Details of operation mode pulsed

Definitions

• the present invention relates to the treatment of blockages in tubular tissues and organs with concurrent reduction of platelet aggregation; and more specifically, relates to the removal of intravascular occlusions such as atherosclerosis or thrombus in a manner such as to retard or prevent recurrence of the thrombus at the removal site.
• Angioplasty had its origin with balloon angioplasty.
• the cardiologist inserts a long, hollow, narrow tube (catheter), into an artery through an incision.
• the doctor can monitor the exact place of the catheter inside an artery.
• the cardiologist advances the tube through the blood vessels to reach the blockage.
• a second, thinner catheter is then inserted into the first catheter.
• At the tip of the second catheter exists a small miniature, deflated balloon. Once in proper position, the miniature balloon is inflated, causing the narrowed area of the artery to become slightly wider.
• a device known as a stent is inserted via another narrow catheter. A stent reduces the likelihood that the artery becomes narrowed again after the angioplasty procedure.
• Laser angioplasty had its origin in the 1980s to overcome inherent problems with and limitations of balloon and stent angioplasty-restenosis. Laser irradiation was demonstrated to ablate atherosclerotic tissue, which allowed recanalization of lesions that could not be traversed by conventional balloon catheters. In order for laser angioplasty to be effective, however, without lateral tissue damage, a laser with the proper wavelength and energy was required. The object was to remove (or tunnel through) the obstruction to allow restoration of blood flow without damaging the blood cells or the blood vessel tissues. Damage to surrounding tissue from balloon or laser angioplasty may trigger clotting of the blood, which may result in the reoccurrence of the occlusion.
• Thermal damage caused by laser energy being absorbed by the tissues depends on the wavelength of the laser, duration of the beam, tissue color, consistency, and water content.
• thermal laser angioplasty a laser is used to heat a biocompatible metal alloy tip attached to a fiberoptic waveguide. The surgeon guides the probe through the obstruction causing a small lumen for the blood to flow through. This method can cause extensive thermal damage of the tissues as well as carbonization and necrosis of the vessel walls.
• Photothermal laser angioplasty involves contact of a laser probe that rapidly heats the plaque (obstruction) to the point of vaporization by direct absorption of the light energy. This method is more productive and safer than the thermal method, but still can cause damage to vessel walls.
• the third general method is photoablative laser angioplasty that involves the use of an ultraviolet laser.
• the excimer, excited dimer, laser uses either two noble gas atoms or a noble gas atom in conjunction with a halogen atom to lase at different wavelengths, mostly ultraviolet (UV).
• Excimer lasers (“cool" lasers) were, thus, found particularly useful because they generate nanosecond, high power, UV and UVB pulses that cause bonds to break and plaques to vaporize by acoustic shock waves and/or photoablative effect.
• Excimer laser angioplasty technology involves moving a fiberoptic catheter through the circulatory system to destroy and thus remove or tunnel through occlusions along the arterial wall.
• the energy source of an excimer laser can be a beam of electrons at high energy or many electrons at high current discharge (10,000 A).
• XeCl is a common excimer laser that is used for angioplasty. In a typical XeCl laser, an electron collides with a Xe atom causing it to go to an unstable electronic configuration, which allows it to bind with a CI atom and produce XeCl*. Since there are no XeCl* molecules at a low energy state, population inversion takes place with the resulting emissions around 300 nm.
• Platelets the body's natural blood-clotters
• thrombocytes platelets play a major role in blood coagulation, clotting and hemostasis (stoppage of bleeding).
• Platelets are the smallest blood components. Platelets detect and attach themselves to specific molecular markers that are typically produced when a blood vessel is damaged or ruptured and adhere to the vascular damage site. Through a complex mechanism, they express molecules on their surfaces that attract other blood cells, and that stimulates the production of fibrinogen and fibrin.
• antiplatelet drugs which are a type of anticoagulant, have been prescribed for angioplasty patients to reduce the likelihood that the platelets will gather together (aggregate) and form potentially harmful blood clots. All patients, for example those with bleeding ulcers, cannot use antiplatelet medications. Additionally, these medications are not always effective.
• thrombus being an easily fractured substance, was incompletely ablated, causing rather large pieces of material to float downstream and form blood clots in the small downstream arteries.
• Various complications were reported in this patient group, related to the lack of blood flow through the arteries. Largely, based on this experience, it became generally accepted that the presence of thrombus in an artery excluded the use of excimer laser angioplasty in that artery.
• U.S Patent 6,022,309 issued February 8, 2000 to Celliers et al, for Opto- acoustic thrombolysis applied laser angioplasty to vascular thrombus.
• This is an example of a catheter-based laser device for generating an ultrasound excitation of a liquid medium to fragment a thrombus. Pulsed laser light is guided through an optical fiber to provide the energy for producing the acoustic vibrations. The optical energy is deposited in a liquid medium to generate an acoustic impulse. Thus, the laser energy is used to generate the acoustic shock wave in the solution. This effect is described further in the specification as laser light absorbed by the fluid surrounding the catheter.
• the present invention does not rely on direct ablation of the occlusion, but instead uses a high frequency train of low energy laser pulses to generate ultrasonic excitations in the fluids in close proximity to the occlusion.
• a repetition rate which may vary from 10 Hz to 100 kHz
• an ultrasonic radiation field is established locally in the medium.
• Celliers et al. teaches the use of an ultrasonic wave to dislodge the occlusion tearing it into fragments or pieces.
• the second procedure is to deliver a preselected deposit-dissolving medication into the blood stream in the vicinity of the deposit through a channel or lumen in the catheter promptly after completion of the first procedure.
• the deposit-dissolving medication penetrates into openings created in the deposit by the shock wave to begin to break it up or dissolve it.
• the first and second procedures are repeated in the same sequence at least once, and preferably several times, to ultimately fragment the deposit so that the fragments may be removed through the channel in the catheter.
• Alt describes how these fragments may be dissolved to keep them from becoming embolisms.
• Alt and Celliers et al. disclose methods which produce macro sized fragments, which must be dissolved and eventually removed. Neither patent mentions post-procedure clotting from tissue damage.
• Vascular occlusions can be treated with pulses of laser light which generate pressure spikes within the occlusion while minimizing the occurrence of post treatment embolism and retarding, diminishing or preventing the formation of post treatment retenosis.
• the medium within the working canal of the vessel, in contact with the occlusion is substantially transparent to the wavelength of the laser light used such that a substantial portion of the laser energy is absorbed by the occlusion.
• Pulsed laser light is transmitted through a catheter encased fiberoptic, the distal end of which is placed in substantial contact with an occlusion in the presence of a liquid medium which is substantially transparent to the laser light, to emulsify the occlusion to cellular sized debris while treating platelets disposed upon surrounding tissue to retard, minimize or prevent formation of thrombus.
• a pulsed radiation field can be established locally within the occlusion to generate a rapid positive pressure spike through an aqueous, liquid to vapor, phase transition, and a subsequent rapid negative pressure spike through a vapor to liquid aqueous phase transition to reduce the biologic material to a cellular size debris.
• the ultraviolet light breaks the occlusive tissue into subcellular debris by directly breaking the molecules of the tissue when those molecules absorb ultraviolet photons. This is the photo-ablative effect unique to ultraviolet laser angioplasty.
• a repetitive series of laser energy pulses emulsifies the entirety of the biologic matter forming the occlusion while treating the surrounding tissue to retard, inhibit or prevent platelet aggregation.
• an excimer laser system is used. This method can be used in vivo for the treatment of for example thrombolytic vascular conditions and to remove and retard recurrence of such conditions.
• laser energy transmission is provided through a catheter encased fiberoptic to the distal end which is in substantial contact with a vascular occlusion, in the presence of a medium which is substantially transparent to the laser energy, to provide ablation of the occlusion to cellular sized debris with concurrent treatment to surrounding tissue to inhibit retard, minimize or even prevent platelet aggregation thus minimizing thrombosis.
• Dissolution of the occlusion is promoted by pulsed, laser energy produced, pressure spikes, which emulsify the occlusion.
• a method for ablating a vascular obstruction comprises inserting a fiber optic into the vasculature to a point in substantial contact with an occlusion in the presence of a medium that is substantially transparent to the wavelength of the laser light, and delivering an amount of pulsed laser energy, through the fiber optic, to emulsify the occlusion to a non embolism sized debris while concurrently retarding, minimizing inhibiting or even preventing platelet aggregation on surrounding vascular tissue to minimize the occurrence of thrombus.
• the laser light has (i) a pulse frequency within the range of 10 Hz to 200 Hz, (ii) a wavelength within the range of 200 nm to 2500 nm and (iii) an energy density within the range of 10 mJ/mm 2 to 100 mJ/mm 2 .
• FIG. 1 shows a longitudinal cross sectional view of an application of the optical fiber-based catheter used in an artery in accordance with the present invention.
• FIG. 2 shows a longitudinal cross sectional view of an application of the optical fiber-based catheter used in a vein in accordance with the present invention.
• FIG. 3 depicts an annular fiber arrangement of the distal tip of optical fiber- based catheter used in accordance with the present invention.
• FIG. 4 depicts a segmented fiber arrangement of the distal tip of the optical fiber-based catheter used in accordance with the present invention.
• FIG. 5A shows the positioning of the distal tip of the catheter encased fiber optic in relation to the lesion to be treated by the method of the instant invention.
• FIG. 5B shows the positioning of the distal tip of the catheter encased fiber optic in relation to the lesion during treatment by the method of the instant invention.
• FIG. 5C shows the positioning of the distal tip of the catheter encased fiber optic in relation to the ablated lesion at the termination of treatment by the method of the instant invention.
• FIG. 6 shows a graphic depiction of the positive and negative pressure spikes associated with the ablation of an occlusion in accordance with the process of the instant invention.
• FIG. 7 shows a cross section of a vascular member treated in accordance with the process of the instant invention showing ablated material and the treated platelets.
• FIG. 8 shows the distal tip of a fiber optic having non-parallel fibers.
• the procedure used in accordance with the invention is similar to conventional balloon angioplasty.
• the vascular lesion, blockage or occlusion is crossed with a flexible guide wire.
• the laser catheter which contains a central guide wire lumen, is introduced through a guide catheter, which allows introduction of solutions (medium) to the vessel being treated.
• the distal tip of the fiber catheter is placed in substantial contact with the proximal end of the occlusion to be removed. It will be guided through the process along the guide wire.
• a medium (solution) which is substantially transparent to the wavelength of the laser light, is introduced into the blood vessel so that the energy will pass through the medium and penetrate the occlusion to be removed.
• a preferred system for the vascular ablation of a thrombus comprises a XeCl excimer laser delivering pulses of light at 308 nm, with a pulse width of at least 100 ns and a pulse repetition rate of between about 25 and 100 Hertz.
• the light from the laser is launched into pure synthetic silica fibers contained in an intravascular catheter.
• the fluence is preferably in the range of from about 30 to 45 mJ/mm of fiber surface area.
• the distal tip of the fiber catheter is advanced to the proximal end of the thrombus mass.
• the distal tip is advanced at a rate of from about 0.25 to about 0.75 mm per second while the laser is pulsing. The process is repeated until the distal catheter tip reaches the distal edge of the lesion being treated.
• the pressure spike of the instant invention comprises an energy induced, expansion of the material of the occlusion to produce a rapid, positive pressure spike and subsequent rapid energy diffusion to surrounding tissue to produce a negative pressure spike.
• the presence of a medium transparent to the wavelength of the laser light allows substantial energy to impinge on the occlusion to cause emulsification and/or liquefaction of the occlusion resulting in harmless cell sized debris which is flushed from the site and reabsorbed by the body.
• the distal tip of the catheter progresses through the occlusion with each set of pulses to remove the blockage and, simultaneously, treating the surrounding vascular area to retard or prevent platelet aggregation.
• a blood vessel 10 with vascular wall 12, a blocking thrombus lesion 14, and a stenotic plaque deposit 16 comprise the vessel to be treated.
• a laser 20 provides laser light into optical fiber 22, located within a laser catheter 24, which has been inserted into the blood vessel 10 through guide catheter 26.
• the exterior diameter of the laser catheter 24 is smaller than the interior diameter of guide catheter 26 to provide an irrigation lumen 28 through which solutions and medicaments can be introduced into vessel working channel 18.
• a retrograde flushing passage 32 is formed between the exterior of the guide catheter 26 and the vascular wall 12 to provide for exit of occlusion debris irrigated from the vessel-working channel 18.
• a guide wire 30 extends through laser catheter 24 in a centered guide wire lumen (not shown).
• the thrombus 14 is crossed with guide wire 30.
• the distal end of fiber 22 is placed in substantial contact with the proximal end of thrombus 14 within blood vessel 10.
• a solution or medium, which is substantially transparent to the laser light, so that the energy will pass through the medium and impinge on the thrombus 14, is introduced into the vessel-working channel 18 through irrigation lumen 28.
• the guiding catheter 26 is introduced (left or right depending on the target coronary artery) using a standard flexible guide wire 30.
• the flexible guide wire 30 is then inserted across the thrombus 14.
• the position of the guide wire 30 is monitored within the vessel 10 under fluoroscopy.
• the guide wire 30 is inserted into the centered lumen in the laser catheter 24 by introducing the proximal end of the guide wire 30 into the distal tip of the laser catheter 24, and the laser catheter 24 is carefully advanced in small increments, to avoid kinking the guide wire 30.
• the guide wire 30 is maintained in its position in the patient's circulatory system while advancing the laser catheter 24.
• the laser catheter 24 is inserted into the guide catheter 26 and advanced to the guide catheter's 26 distal tip while maintaining the guide wire 30 position.
• the guide catheter's 26 position in the ostium of the vessel 10 is reconfirmed with contrast media injection and fluoroscopy prior to advancing the laser catheter 24 to the thrombus 14.
• the laser catheter 24 is advanced to the thrombus 14 while maintaining the guide wire's 30 position in the patient's circulatory system. Contrast medium solution is then injected through the irrigation lumen 28 to verify the positioning of the laser catheter 24 under fluoroscopy.
• a solution which is transparent to the laser light wavelength, such as physiologic saline solution or lactated Ringer's solution, is then infused into the arterial working channel 18 including the lasing site and vascular structures adjacent to the lasing site through the irrigation lumen 28.
• the laser 20 is activated and the laser catheter 24 slowly advanced allowing the laser energy to remove the desired material.
• the lasing site is continually irrigated with solution through irrigation lumen 28, which flushes debris from the working channel 18, and exits through retrograde flushing passage 32.
• the laser catheter 24 is advanced at a rate commensurate with the laser energy and pulse repetition rate being used per pass.
• a rate of approximately 0.5 mm to approximately 1 mm per five-second lasing train at 25 pulses per second is exemplary.
• An advancement rate that is too rapid will fail to emulsify the thrombus completely and cause larger debris.
• FIG. 2 there is shown the laser angioplasty configuration according to the invention for a vein.
• a vein 110 with vascular wall 112, an elongated blocking thrombus lesion 114 comprise the vessel to be treated.
• a laser 20 provides laser light into optical fiber 22, located within the laser catheter 24 (shown in FIG. 2), which has been inserted into the blood vessel 110 through guide catheter 26.
• the exterior diameter of the laser catheter 24 is smaller than the interior diameter of guide catheter 26 to provide an irrigation lumen 28 through which solutions and medicaments can be introduced into vessel working channel 118.
• a guide wire 30 extends through laser catheter 24 in a centered guide wire lumen (not shown).
• the thrombus 114 is crossed with guide wire 30.
• the distal end of fiber 22 contained in laser catheter 24 is placed in substantial contact with the proximal end of thrombus 114 within vein 110.
• a solution which is substantially transparent to the laser light so that the energy will pass through the medium and impinge on the thrombus 114, is introduced into the vessel-working channel 118 through an irrigation lumen 28.
• distal end of fiber 22 contained in laser catheter 24 is slightly convex as is the thrombus 114. This configuration creates lased areas 134 filled with medium. Because the medium is substantially transparent to the laser light substantially all the energy will pass through the medium in areas and impinge on the thrombus 114, thus, the medium will not heat appreciably ahead of the thrombus 114.
• the operation in this procedure is substantially the same as for FIG. 1.
• FIG. 3 and FIG. 4 there is shown the distal tip of the laser catheter 124 with guide wire lumen 125 and having two fiber 122 configurations.
• the fibers 122 are arranged annularly. While the fibers 122 still exit the distal end of laser catheter 124 perpendicular to the long axis of laser catheter 124, so that the light is emitted straight out the end, the fibers 122 can be fired as individual rings. This can be accomplished one ring at a time or in gang.
• the fibers 122 are arranged in pie shaped segments.
• FIG. 5A shows the positioning of the distal end of fiber 222 contained in laser catheter 224 in relation to the thrombus 214 prior to commencing treatment
• FIG. 5B shows the positioning of the distal end of fiber 222 contained in laser catheter 224 in relation to the thrombus 214 during treatment
• FIG. 5C shows the positioning of the distal end of fiber 222 contained in laser catheter 224 in relation to the ablated thrombus 214 at the termination of treatment.
• the distal tip of fiber 222 on guide wire 230 which crosses thrombus 214, is positioned in work area 218 through guide catheter 226.
• the exterior diameter of the laser catheter 224 is smaller than the interior diameter of the guide catheter 226 to provide an irrigation lumen 228, through which solution and medicaments are introduced into vessel working channel 218 in preparation for commencing ablation of the thrombus.
• the distal tip of fiber 222 is in substantial contact with thrombus 214.
• lased light emits from the distal end of fiber 222 to ablate a section 215 directly in front of the laser catheter 224.
• the section 215 has a depth of about 50 to 100 microns, which is the extent of the penetration of the laser light into the thrombus 214.
• the material in 215 is homogenized or emulsified and sub cellular (non-embolism producing) debris is carried through vessel working channel 218, exiting through retrograde flushing passage 232.
• Platelets 234, shown on either surface of the previously ablated thrombus material 214 are treated or stunned so that they form a layer of inactivated platelets on the surface of the lased thrombus 214.
• FIG. 6 there is shown a pictorial graph of the pressure spikes created in accordance with the inventive method.
• This figure is meant as a graphic, simplified picture of the pressure spikes during the inventive procedure.
• the following theory is presented for elucidation and is not meant to be limiting. It is theorized that there are two thermal effects during laser angioplasty. The first is associated with a photoacoustic phenomenon. If the high heat of the fiber tip is not controlled, a sudden, drastic rise in temperature in the medium layer in contact with the fiber tip creates a sudden high pressure, creating a pressure wave that radiates away from the fiber tip in all directions. This photoacoustic effect, noticed by researchers in Holland, Germany, and elsewhere, and described in Alt and Celliers et al., creates an audible sound. When blood or other radiation absorbing media are present in front of the lesion, the effect is severe.
• FIG. 7 shows a treated vessel 312 with inactivated platelets 334 covering substantially all the treated vascular tissue including ablated plaque as well as ablated thrombus.
• the parameters for a particular laser to effect ablation of the occlusion as well as the retarding effect to the platelets.
• the energy delivered to the tissue to be ablated is that amount effective to cause photo ablative expansion and contraction while stunning platelets to retard their aggregation tendencies.
• FIG. 8 there is shown another distal tip of laser catheter 324 having an array of fibers 322 that do not exit the distal end of laser catheter 324 perpendicular to the long end axis of the laser catheter 324.
• a concentric guide wire lumen carries guide wire 330 through the center of laser catheter 324.
• the laser light is irradiated at various angles from the centerline of laser catheter 324 to provide laser energy to an occlusion other than in a perpendicular line.
• laser light can be irradiated to provide ablative effects in accordance with the invention to the tops or bottom surfaces of occlusions as the laser catheter 324 passes through the occlusion in a manner as shown in FIG. 5 A, FIG. 5B, and FIG. 5C.
• Catheters useful in practicing the present invention, can be of various types.
• one embodiment can consist of a catheter having an outer diameter of 3.5 millimeters or less, preferably 2.5 millimeters or less.
• the optical fiber which can be a 50 to 400 micron diameter or smaller silica (fused quartz) fiber such as the model SG 800 fiber manufactured by Spectran, Inc. of Sturbridge, Mass.
• the catheter may be multi-lumen to provide flushing and suction ports.
• the catheter tip can be constructed of radio-opaque and heat resistant material. The radio- opaque tip can be used to locate the catheter under fluoroscopy.
• the invention can be used with various catheter devices, including devices which operate under fluoroscopic guidance as well as devices which incorporate imaging systems, such as echographic or photoacoustic imaging systems or optical viewing systems.
• the laser catheters that are preferably used in accordance with the inventive method consist of optical fibers encased within a polyester shaft. There are two major portions of the laser catheter shaft, the proximal portion, which terminates at the laser connector, and the distal portion, which terminates at the tip having direct patient contact.
• the fibers terminate at the distal tip within a polished adhesive end and at the proximal end within the laser connector.
• a radiopaque marker is located on the distal end of the laser catheter to aid localization within the coronary vasculature in conjunction with fluoroscopy.
• the guidewire lumen begins at the distal tip and is concentric with the fiber array, and exits the laser catheter about 9 cm away from the distal tip, which has direct patient contact.
• a proximal marker may be located on the outer jacket of the laser catheter, 104 cm from the distal tip, to assist in the placement of the laser catheter within a femoral guiding catheter without the need for fluoroscopy.
• Multifiber laser catheters transmit energy from the laser to the obstruction in the artery.
• the ultraviolet energy is delivered to the tip of the catheter to photo-ablate fibrous, calcific, and atheromatous lesions, thus recanalizing diseased vessels.
• the laser catheters may have a proprietary lubricious coating to ease their trackability through coronary vessels.
• Lesions treatable in accordance with the instant invention are traversable by a guidewire and composed of atherosclerotic plaque and/or calcified material.
• the lesions should be definable by angiography.
• the process of this invention accomplishes lysis of thrombus, atherosclerotic plaque or any other occluding material in the tubular tissue.
• a working channel which surrounds or runs parallel to the optical fiber may be used to dispense small quantities of thrombolytic drugs to facilitate further lysis of any significantly sized debris (>5 micrometer diameter particles) left over from the instant process.
• Applications envisioned for this invention include any method or procedure whereby localized ablations are to be produced in the body's tissues through laser energy.
• the invention can be used in (i) endovascular treatment of vascular occlusions that lead to ischemic stroke, (ii) endovascular treatment of cerebral vasospasm, (iii) endovascular treatment of cardiovascular occlusions (iv) endovascular treatment of stenoses of the carotid arteries, (v) endovascular treatment of stenoses of peripheral arteries, (vi) general restoration of patency in any of the body's luminal passageways wherein access can be facilitated via percutaneous insertion, and (vii) lithotriptic applications including therapeutic removal of gallstones, kidney stones or other calcified objects in the body.
• the pulsed laser energy source used by this invention can be based on a gaseous, liquid or solid state medium.
• Rare earth-doped solid state lasers, ruby lasers, alexandrite lasers, Nd: YAG lasers and Ho:YLF lasers are all examples of lasers that can be operated in a pulsed mode at high repetition rate and used in the present invention. Any of these solid state lasers may incorporate non-linear frequency-doubling or frequency- tripling crystals to produce harmonics of the fundamental lasing wavelength.
• a solid state laser producing a coherent beam of ultraviolet radiation may be employed directly with the invention or used in conjunction with a dye laser to produce an output beam which is tunable over a wide portion of the ultraviolet and visible spectrum.
• Tunability over a wide spectrum provides a broad range of flexibility for matching the laser wavelength to the absorption characteristics of the tissue located at the distal end of the catheter.
• the output beam is coupled by an optical fiber to the surgical site through, for example, a percutaneous catheter.
• a pulsed beam of light removes and/or emulsifies thrombus or atherosclerotic plaque with less damage to the underlying tissue and less chance of perforating the blood vessel wall than prior art devices.
• Various other pulsed lasers can be substituted for the disclosed laser sources.
• various dye materials and configurations can be used in the dye laser.
• Configurations other than a free-flowing dye such as dye-impregnated plastic films or cuvette-encased dyes, can be substituted in the dye laser.
• the dye laser can also store a plurality of different dyes and substitute one for another automatically in response to user- initiated control signals or conditions encountered during use (e.g. when switching from a blood-filled field to a saline field or in response to calcific deposits).
• Suitable dyes for use in the dye laser components of the invention include, for example, P-terphenyl (peak wavelength 339); BiBuQ (peak wavelength: 385); DPS (peak wavelength: 405); and Coumarin 2 (peak wavelength: 448).
• the pulsed light source may be an optical parametric oscillator (OPO) pumped by a frequency-doubled or frequency-tripled solid-state laser.
• OPO systems allow for a wide range of wavelength tunability in a compact system comprised entirely of solid state optical elements.
• the laser wavelength in OPO systems may also be varied automatically in response to user-initiated control signals or conditions encountered during use. ,
• Another implication of the technique is that other forms of energy delivered to the treatment site may create identical effects.
• the energy must be delivered to a small volume of tissue, typically on the order of a cubic millimeter or less, in a very short period of time, typically less than a microsecond.
• the energy will be rapidly turned into heat in the tissue, regardless of the form of energy arriving at the tissue.
• different laser wavelengths could be used to deposit the required energy in the tissue, or pulsed incoherent light, or even pulsed electrical or radio frequency energy.
• This technique may also be applicable to the liquefaction or modification of other brittle tissue structures, such as calcified lesions, cartilage, bones, calculi, biliary stones,, etc.
• laser lithotripsy practices a similar technique, by applying a large pulse of energy to the external surface of kidney stones. The resulting surface explosion and pressure wave are meant to fracture the stone into small pieces more easily passed through the urinary tract.

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