Endovascular Method and Apparatus with Electrical Feedback

Abstract

An apparatus for delivering energy, and in particular laser energy, to a tissue is adapted to minimize or eliminate burn back caused by contact between the energy delivery apparatus and bodily fluids by (i) preventing the energy delivery apparatus from contacting bodily fluids or tissues that might burn or cause the apparatus to burn; and/or (ii) monitoring the apparatus to detect overheating in order to withdraw the apparatus or control the energy supply in case overheating is detected. The apparatus is applicable, by way of example, to treatment of blood vessels using endovascular techniques.

Claims

1. Apparatus for therapeutic in vivo application of laser energy to a tissue, comprising: an optical fiber; and an introducer arranged to be inserted into a body cavity and to receive said optical fiber, said optical fiber being moved through the introducer to a position at which the laser energy may be delivered by said optical fiber to the tissue, wherein an end of the introducer extends beyond a tip of said optical fiber when the optical fiber is at said laser energy delivery position, the end or said introducer substantially surrounding the tip of the optical fiber to prevent body fluids from contacting the optical fiber, and wherein a tip of the optical fiber includes an angled surface that causes the laser energy to exit the optical fiber at an angle relative to a principal axis of the optical fiber, whereby the laser energy is delivered to the tissue through the introducer.

2. Apparatus as claimed in claim 1, wherein the introducer has a closed end.

3. Apparatus as claimed in claim 1, wherein the introducer has an open end arranged to enable fluid to pass through the end of the introducer.

4. Apparatus as claimed in claim 1, further comprising a feedback circuit for detecting overheating or burn back of at least one of said optical fiber, said tissue, and said introducer.

5. Apparatus as claimed in claim 1, wherein the feedback circuit includes a thermal sensor positioned at an end of said introducer.

6. Apparatus as claimed in claim 5, wherein said thermal sensor is a thermocouple.

7. Apparatus as claimed in claim 5, wherein said thermal sensor is a thermistor.

8. Apparatus as claimed in claim 1, wherein the feedback circuit includes an optical detector.

9. Apparatus as claimed in claim 1, wherein the feedback circuit includes a detector for detecting radiation transmitted back through the introducer.

10. Apparatus as claimed in claim 9, wherein said radiation is an aiming beam.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a schematic drawing of a conventional varicose vein treatment apparatus.

[0020] FIGS. 2A and 2B are side view of an optical fiber, showing the effects of burn back.

[0021] FIG. 3 is a schematic drawing of a treatment apparatus constructed in accordance with the principles of a preferred embodiment of the invention.

[0022] FIGS. 4A-4F show various fiber tips for use in connection with the preferred treatment apparatus.

[0023] FIG. 5 shows a detector that may be used in connection with a treatment apparatus, according to another preferred embodiment of the invention.

[0024] FIG. 6 is a schematic drawing of an optical fiber with a heat sink according to another preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] As illustrated in FIG. 3, the apparatus of a preferred embodiment of the invention includes an energy delivery device in the form of an optical fiber 10 that is introduced into the vessel 11 by means of a Teflon introducer 12. The Teflon introducer lacks a homeostasis valve and has an end 15 that extends beyond the tip 14 of the fiber 10 and that is arranged to prevent contamination of the fiber tip 14 by blood 11 in the vessel. The Teflon introducer may optionally include a motorized fiber pull back 16. In addition, a detector 17 may be included, as described in more detail below.

[0026] End 15 of the introducer may be either open or closed. If it is completely closed, then the end may include cooling means within the introducer for cooling the fiber. Cooling means for use in a catheter are well known and the details of the cooling means do not form a part of the present invention. Alternatively, the end 15 of the introducer may be open, in which case saline or other irrigation fluid may be introduced at the opposite end to flush the end of the introducer and prevent blood or tissue from accumulating there. In either case, blood is prevented from contacting the tip 14 of the fiber, thereby reducing burn back.

[0027] FIGS. 4A to 4F show various tip configurations. The tip can be arranged to direct laser light in a radial direction so as to impinge on walls of the vessel, either in a single direction or along an arc extending up to 360° around the fiber. Such side firing fiber optic tips are known, and the invention is not limited to any particular tip. FIG. 4A shows a conical tip; FIG. 4B shows an orb-shaped tip; FIG. 4C shows an inverted cone-shaped tip; FIG. 4D shows an angled tip; FIG. 4E shows a reflective tip; and FIG. 4F shows an angle tip. The cap of FIG. 4F may be similar to the one shown in U.S. Pat. No. 5,242,438, except that the fiber tip is not exposed. Those skilled in the art will appreciate that a 360° effect may be achieved with a simple side firing laser by rotating the fiber.

[0028] FIG. 6 shows a further variation of the invention, used in cases where the bare fiber is exposed, or to further protect the fiber within the introducer. In the variation illustrated in FIG. 6, the bare fiber 70 is surrounded by an optional insulator 71 and heat sink 72, which helps prevent burn back by removing or directing heat away from the fiber tip. Those skilled in the art will appreciate that the insulator and heat sink may be added to a fiber to help prevent burn back even when the fiber is used without an introducer.

[0029] In addition to protecting the fiber from contamination and resulting damage, the invention provides for monitoring and detection of conditions that might affect operation of the apparatus, such as burn back or bends in the fiber or energy delivery device. The monitoring device may be a conventional detector 17, but instead of configuring the detector to monitor light exiting the fiber, the detector 17 is configured to detect light exiting the introducer, as indicated by dashed line 18 in FIG. 3. A mirror 19 or fiber may be positioned to direct light exiting the introducer to the detector 17.

[0030] Alternatively, detector 17 may be electrically connected to one or more electrical sensors 20 positioned in the introducer to detect heat or light resulting from burn back, and connected to the monitor 17 by a wire, indicated in FIG. 3 by dashed line 21. The electrical sensor may be a thermocouple, thermistor, or any other electrical detector capable of being positioned in the introducer and of generating an electrical signal in response to heat, or a photodetector or similar device sensitive to light generated during overheating or burn back. Although a wire is illustrated, the sensor(s) 21 in the introducer may also include a wireless transmitter or electrical to optical converter for wireless or optical communications.

[0031] In embodiments where light exiting the introducer is to be detected, the introducer must act as a waveguide. The inner diameter and material of the introducer may be selected accordingly, depending on the wavelengths of light to be detected. For example, burn back can be directly detected based on light emitted by the burning body fluid, or by reflecting an aiming beam of the laser back to through the introducer to measure the clarity of fluid used to flush the end of the introducer in case of an open-ended sheath.

[0032] Alternatively, instead of monitoring light propagating through the introducer, the detector may be arranged to monitor the fiber cladding. An example of a detector capable of monitoring the fiber cladding is illustrated in FIG. 5. In this embodiment, a reflector 45 reflects a portion of the secondary source of radiation 40 into the proximal end of sense fiber 50. The secondary radiation is further transmitted toward the distal end of the sense fiber 55, which directs the radiation to an optical filter 58, after which the light is focused onto a photodetector 63 with a condensing lens 65. The photodetector converts optical radiation to an electrical signal that is further amplified by an op-amp 70. The amplified electrical signal 80 Vout can now be used to control the laser and/or produce a signal to alert the operator of the potential fiber fault.

[0033] A method of treating varicose veins using the apparatus illustrated in FIGS. 1-6 will now be described. According to the method of the invention, the right/left lower extremity to be treated is prepped and draped in the customary sterile fashion. A layer of ultrasound transmission gel is applied to an ultrasound probe, which is then draped in a sterile sleeve and placed onto the sterile field. Using the ultrasound, the entire greater saphenous vein is mapped with a sterile surgical marker and measurements of its length, maximal and minimal diameters, and tortuosities are recorded.

[0034] Under local anesthesia and using ultrasound guidance, percutaneous entry is made with a 19-gauge needle into the Greater or Lesser Saphenous vein. A 0.035″ J tip guide wire is inserted through the needle and is advanced up the Greater Saphenous Vein (GSV) to the Sapheno Femoral Junction (SFJ). The needle is removed and discarded, the skin at the entry site is nicked with a scalpel, and a 45 cm 4 or 5 French introducer sheath is inserted through this opening over the guide wire. With this new procedure the fiber is not required to pass beyond the introducer, the distal introducer tip can be reduced to the same size as the dilator and thus eliminate the need for the dilator. The tip of the introducer should be marked (radiopague and color markings) to indicate the distal end. Also the fiber should have markings (i.e. cm, mm inches . . . ) To indicate its position relative to the introducer, since, the fiber and introducer does not require a dilator. The fibers markings could also be encoded to allow for electrical (i.e. magnetic bar code) or optical means to enable remote control or other feedback. Remote control could include laser enable/disable, automatic pull back, presently a foot switch is used to enable the laser, where a hand switch coupled to the fiber would be with the feedback determining the rate of pullback, laser enable, cumulative joules, etc. . . .

[0035] The sheath is advanced to the SFJ. The dilator, if used, and the guidewire are then removed, and the laser fiber is introduced to the distal end of the introducer. The distal end of the introducer I.D. should be large enough to pass a guidewire but small enough to prevent the fiber tip from passing thru. Also the fiber should have a mechanical stop that controls how far the fiber can be introduced into the introducer.

[0036] As noted above, the fiber tip may be shaped (cone, angled, etc. see attachment A) or capped with a reflective tip to provide more lateral energy perpendicular to the axis of the fiber. The more perpendicular the energy is toward the laser catheter wall the more that is transmitted to the tissue. If power density is an issue, then a diffusing tip or automated fiber movement could also be added. Coaxial water flow may be added where deeper tissue penetration and/or reduced surface reflections from the laser sheath are required.

[0037] The position of the fiber and introducer sheath within the GSV is confirmed with ultrasound. The distal end of introducer sheath, is then positioned one or two centimeters below the SFJ. While preventing the introducer sheath from moving, the fiber is withdrawn.

[0038] The location of the introducer is confirmed using ultrasound anesthesia is administered along the greater saphenous vein. A final check of the introducer position, about 1 to 2 cm below the SFJ is made using ultrasound and by direct visualization of the red aiming beam through the skin. Anesthesia, is administered along the greater saphenous vein. A final check of the fiber position, about to 2 cm below the SFJ is made using ultrasound and protective eyewear is worn by all persons in the operating room. The laser source, such as but not limited to 810,940 or 980 nm, is turned on by means of a foot pedal or hand piece activation switch. Using continuous energy, e.g., 14 watts, the fiber is withdrawn at a rate of 1 to 2 mm/second. Because the laser sheath is not removed while treating, vein areas needing further treatment can be retreated by repositioning the fiber within the introducer to the desired treatment area. Afterwards, both the laser fiber and sheath are removed.

[0039] Repeat ultrasound imaging is performed to confirm absence of flow through the entire length of treated vein, and absence of deep venous thrombosis immediately and 5 minutes following the procedure. After assuring hemostasis, the skin incision over the saphenous vein is closed with a bandage. A class 2-compression stocking is placed on the leg of the treated vein.

[0040] Having thus described a preferred embodiment of the invention in sufficient detail to enable those skilled in the art to make and use the invention, it will nevertheless be appreciated that numerous variations and modifications of the illustrated embodiment may be made without departing from the spirit of the invention, and it is intended that the invention not be limited by the above description or accompanying drawings, but that it be defined solely in accordance with the appended claims.