Patent Publication Number: US-6981971-B2

Title: Medical laser device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority from U.S. Provisional Patent Application Ser. No. 60/369,256, filed Mar. 27, 2002 and from UK Patent Application Serial No. GB-0114687, filed Jun. 15, 2001, the entire contents of each application being hereby incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a medical laser device. 
   2. Description of the Related Art 
   In certain invasive medical procedures thermal or other energy is administered to a patient with beneficial effects. For example, energy can be used to detect a tumour or a region of the body, or to destroy or denature diseased or malfunctioning body tissue. One example of this type of treatment is disclosed in U.S. Pat. No. 6,095,149 which describes the treatment of invertebral disc abnormalities with thermal energy. Other types of medical treatment utilise laser energy, for example endovenous laser treatment (EVLT), wherein laser energy is delivered to the inner wall of a vein. 
   Laser energy may be delivered to an area of the body by means of an optical fiber such as a bare-tipped optical fiber. However, the tips of such optical fibers could cause trauma to soft tissues. Therefore, for some invasive applications it is not desirable to insert the optical fiber directly into the body tissue. Instead, the optical fiber is typically inserted into a flexible introducer sheath which acts to guide and protect the optical fiber (and also the surrounding tissue) whilst it is being inserted into the region of the body to be treated. An introducer sheath is frequently inserted into body tissue over a guide wire and then the optical fiber can be inserted once the introducer sheath is in place in the body. 
   In use the introducer sheath is often positioned so that the optical fiber protrudes a few millimeters or centimeters from the end of the introducer sheath so as to deliver laser energy efficiently from the tip of the fiber to the surrounding tissue. 
   It is known to detect the protrusion of the optical fiber from the introducer sheath using ultrasound and/or direct visualization of a red aiming laser beam from the optical fiber through the skin. However, these methods are unsatisfactory for a number of reasons. The use of ultrasound requires additional equipment which is expensive and complicates the procedure. Visualization of the laser beam is imprecise and at best only a guide and then only in regions of the body which are sufficiently close to the surface of the skin. Therefore, conventional techniques are not suitable for use in a wide range of applications. 
   Furthermore, as a result of it being difficult for an operator or surgeon to determine when the distal end of the optical fiber is approaching the distal end of the introducer sheath, damage can readily occur to the soft tissues if the optical fiber is initially accidentally extended beyond the introducer sheath. As a result an operator must insert the optical fiber very slowly into the introducer sheath and must proceed cautiously at all times which makes the procedure slow. 
   It is therefore desired to provide an improved medical laser device. 
   SUMMARY OF THE INVENTION 
   According to a first aspect of the present invention, there is provided a medical laser device comprising: 
   a laser source for emitting laser radiation; 
   an introducer sheath having a proximal end and a distal end; and 
   an optical fiber having a proximal end and a distal end, the optical fiber in communication with the laser source for transmitting the laser radiation and for emitting the laser radiation from a distal end thereof; 
   wherein the optical fiber comprises a first marker for positioning the optical fiber so that the distal end of the optical fiber is substantially in alignment with the distal end of the introducer sheath and wherein the optical fiber comprises a second marker for indicating how far the introducer sheath should be withdrawn relative to the optical fiber so that the optical fiber projects a predetermined distance beyond the introducer sheath. 
   In use, laser radiation is delivered to the inner wall of a vein where it is absorbed, thermally re-structuring the vein. 
   The first and second markings allow an operator or surgeon to know when the distal end of the optical fiber is aligned with the end of the introducer sheath and when the distal end of the optical fiber extends beyond the introducer sheath by a predetermined amount. This enables the operator or surgeon to quickly insert the optical fiber into the introducer sheath and enables the optical fiber to be positioned in the optimum position relative to the introducer sheath without risk of damage to either the optical fiber or surrounding tissue. 
   The markings may comprise at least one band which extends around at least a portion of the circumference of the optical fiber. 
   Preferably, the two markings are separated by a distance of either about 4 cm, about −3.5 cm, about 3 cm, about 2.5 cm or about 2 cm so that in use the optical fiber will extend preferably between 2-4 cm from the end of the introducer sheath. A separation of approximately 3 cm is particularly preferred. 
   The minimum preferred separation (2 cm) is so as to prevent thermal damage to the introducer sheath during treatment. The maximum preferred separation (4 cm) is so as to minimize the length of the optical fiber remaining within the body once the introducer sheath has been removed from the patient&#39;s body. 
   The two markings or markers may differ in shape and color to aid the operator or surgeon using the device. This can make it easier to refer to the markings, for example, when teaching or explaining how to use the device to another operator or surgeon. 
   The markings may be engraved or embossed an the optical fiber. This enables the operator to have tactile feedback as to the position of the markings, without having to look at the optical fiber. This allows the operator to concentrate on other equipment. Furthermore, if the markings are embossed then there may be sufficient co-operation between the marking and a friction seal of the introducer sheath so as to secure them temporarily together when the introducer sheath is retracted. 
   The laser radiation may be delivered either in a pulsed, continuous or quasi-continuous manner. 
   According to one embodiment, the introducer sheath may comprise graduated markings for assisting a user to withdraw the introducer sheath at a desired rate. This rate may be defined as a distance per unit time or a distance per laser pulse. A visual and/or audible indicator may be provided to give an indication of how fast the introducer sheath should be withdrawn. 
   The optical fiber is preferably secured to the introducer sheath, which is preferably flexible, at a position wherein the first marking is substantially in alignment with the proximal end of the introducer sheath. The optical fiber and the introducer sheath may then be positioned at a desired location using ultrasound. The introducer sheath can then be released from the optical fiber and the introducer sheath withdrawn relative to the fiber optic device until the second marking is substantially in alignment with the proximal end of the introducer sheath, enabling the distal end of the optical fiber to protrude a known distance from the distal end of the introducer sheath in order to administer laser energy. The optical fiber may then be secured to the introducer sheath substantially at the position where the second marking is substantially in alignment with the proximal end of the introducer sheath, and energy from a laser energy source may then be provided to the distal end of the optical fiber. The optical fiber and the introducer sheath may be withdrawn whilst laser energy is emitted from the distal end of the optical fiber. This is an advantageous way of administering laser energy invasively. 
   According to a second aspect of the present invention, there is provided a medical laser device comprising: 
   a continuous laser source for emitting laser radiation; 
   an introducer sheath having a proximal end and a distal end, the introducer  5  sheath having graduations; and 
   an optical fiber having a proximal end and a distal end, the optical fiber in communication with the laser source for transmitting the laser radiation and for emitting the laser radiation from a distal end thereof; 
   wherein the optical fiber comprises a first marker for positioning the optical fiber so that the distal end of the optical fiber is substantially in alignment with the distal end of the introducer sheath and wherein the optical fiber comprises a second marker for indicating how far the introducer sheath should be withdrawn relative to the optical fiber so that the optical fiber projects a predetermined distance beyond the introducer sheath. 
   According to a third aspect of the present invention, there is provided a medical laser device comprising: 
   a pulsed laser source for emitting laser radiation; 
   an introducer sheath having a proximal end and a distal end; and 
   an optical fiber having a proximal end and a distal end, the optical fiber in communication with the laser source for transmitting the laser radiation and for emitting the laser radiation from a distal end thereof; 
   wherein the optical fiber comprises a first marker for positioning the optical fiber so that the distal end of the optical fiber is substantially in alignment with the distal end of the introducer sheath and wherein the optical fiber comprises a second marker for indicating how far the introducer sheath should be withdrawn relative to the optical fiber so that the optical fiber projects a predetermined distance beyond the introducer sheath. 
   According to a fourth aspect of the present invention, there is provided a medical laser device comprising: 
   a laser source for emitting laser radiation; 
   a flexible introducer sheath having a proximal end and a distal end, wherein the proximal and of the introducer sheath is provided with a friction seal for forming a seal with the optical fiber; and 
   an optical fiber having a proximal end and a distal end, the optical fiber in communication with the laser source for transmitting the laser radiation and for emitting the laser radiation from a distal end thereof; 
   wherein the optical fiber comprises a first marker for positioning the optical fiber so that the distal end of the optical fiber is substantially in alignment with the distal end of the introducer sheath and wherein the optical fiber comprises a second marker for indicating how far the introducer sheath should be withdrawn relative to the optical fiber so that the optical fiber projects a predetermined distance beyond the introducer sheath. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which: 
       FIG. 1  shows a medical laser device according to the preferred embodiment; 
       FIG. 2  shows in greater detail the distal end section of the optical fiber shown  FIG. 1 ; 
     FIG.  3 ( a ) shows an optical fiber having been initially inserted into an introducer sheath and FIG.  3 ( b ) shows the introducer sheath having been subsequently withdrawn relative to the optical fiber; and 
       FIG. 4  shows the optical fiber and introducer sheath used for endovenous laser treatment. 
   

   DETAILED DESCRIPTION OF THE DRAWINGS 
   With reference to  FIGS. 1 and 2 , an optical fiber having a distal end  13  and a proximal end  15  is shown which is coupled to a laser energy source  14  via a connector  22 . According to one embodiment the optical fiber  12  has a length of 3.5 ±0.1 m and is preferably provided with a protective buffer layer  18 . One or more markings or other form of indicator  45 ,  46  are arranged on the optical fiber  12  at a predetermined distance from distal end  13 . Preferably, the markings  45 ,  46  are provided around substantially the whole circumference of the protective buffer layer  18  of the optical fiber  12 . According to the preferred embodiment, the laser energy source  14  is an 810 nm diode laser manufactured by DIOMED, Ltd., United Kingdom. The connector  22  may be any suitable connector/fiber terminator such as a standard sub-miniature A (SMA) connector (as shown) or other proprietary connector. 
   The distal end  13  of the optical fiber  12  is shown in more detail in FIG.  2 . The optical fiber  12  is preferably capable of withstanding enviromental temperatures of 20 −10° C. to 120° C. and comprises a glass core  32  with a fiber tip  34 , a cladding layer  30  surrounding the core  32 , and an outer protective buffer layer  18 . The core  32  has a higher refractive index than the cladding  30  and thus laser energy is guided along the core  32  by total internal reflection. According to the preferred embodiment the optical fiber  12  has a 600 μm diameter glass core, for example Type FT600 URT, Spectram 25 (SLT), No. BF05900 available from 3M, USA. The buffer layer  18  is preferably partially stripped back a short distance (e.g., approx. 1 cm) from the fiber tip  34  so that the diameter of the optical fiber  12  in the region around the fiber tip  34  is approximately 0.6 mm. For efficient operation of the device the surface quality of the fiber tip  34  is high. The fiber tip  34  is preferably substantially free from defects within a central aperature of 88% of the diameter of the fiber optic core  32  with all sharp edges having been 5 previously removed from the fiber tip  34 . Preferably, other defects (if present) do not scatter light outside a 0.37 numerical aperature (NA), and do not cause localized heating when illuminated with 60 W of laser light at 810 nm evenly distributed over a 0.37 NA. The optical fiber  12  is preferably capable of withstanding a force of 2 kg, applied between the connector/terminator (SMA)  22 , and the distal end  13 , without damage. 
   The relationship between the position of the markings or indicators  45 ,  46  and an introducer sheath  40  or the like will now be described in more detail with reference to FIGS.  3 ( a ) and ( b ). 
   FIG.  3 ( a ) shows the optical fiber  12  having been initially inserted within an introducer sheath  40  so that the distal end  13  of the optical fiber  12  is substantially flush or otherwise aligned with the distal end  60  of the introducer sheath  40 . Marking  45  is shown substantially aligned with the proximal end  50  of the introducer sheath  40 . The introducer sheath  40  is then withdrawn relative to the optical fiber  12  until marking  46  is substantially aligned with the proximal end  50  of the introducer sheath  40 . As shown in FIG.  3 ( b ), the distal end  13  of the optical fiber  12  then protrudes beyond the distal end  60  of the introducer sheath  40  by a predetermined amount, preferably approx. 3 cm. 
   The introducer sheath  40  comprises a hollow tube  70  with a friction seal  42  at the proximal end  50  to prevent blood loss during insertion into blood vessels. The placement of the introducer sheath  40  through skin and tissue provides access into an area to be treated, and acts as a guide for introducing instrumentation and other apparatus. The introducer sheath  40  is preferably a five French introducer sheath, such as RCF-50-35-45-J-RB available from Cook, Inc., Bloomington, Ind. 
   Markings or indicators  45 ,  46  are preferably optically visual markings which are preferably provided around the whole circumference of the protective buffer layer  18  of the optical fiber  12 , and are provided at predetermined distances from the distal end  13  of the optical fiber  12 . The predetermined distances are arranged to correspond to predetermined positions of the distal end  13  of the optical fiber  12  relative to the distal end  60  of the introducer  40 . The predetermined positions represent both alignment of the respective distal ends  13 ,  60  as shown in FIG.  3 ( a ) and also protrusion of the distal end  13  of the optical fiber  12  beyond the distal end  60  of the introducer  40  as shown in FIG.  3 ( b ). 
   In one embodiment the markings or indicators  45 ,  46  may be engraved or embossed onto the protective buffer layer  18  of the optical fiber  12  surface. Advantageously, this enables an operator to have tactile feedback as to the position of the markings  45 ,  46  and thus have an indication as to the position of the optical fiber  12  within the introducer sheath  40 , without necessarily having a look at the optical fiber  12 . 
   The markings  45 ,  46  preferably comprise one or more bands provided at a number of predetermined locations and may preferably be provided by heat shrinking material onto the optical fiber  12 . The bands are preferably 1 mm wide with ±0.5 mm 25 tolerance. The bands are preferably colored in order to contrast with the color of the buffer layer  18 . The number of bands can give information about the location. For example, one band may be provided as a first marker  45 , and two bands for a second marker  46  etc. 
   The location of the first marker  45  preferably corresponds to the depth of insertion of the optical fiber  12  into the introducer sheath  40  such that the distal end  13  of the optical fiber  12  (i.e. fiber tip  34 ) is very closely aligned or is substantially flush with the distal end  60  of the introducer sheath  40 . The introducer sheath  40  is preferably 35 cm or 45 cm long and may be provided with a 2.1 cm friction seal  42  marking a total length 37.1 cm or 47.1 cm. Accordingly, the first marking  45  may be provided at 371 mm±1 mm or 471 mm±1 mm from the distal end  13  of the optical fiber  12 . 
   The location of the second marking  46  preferably corresponds to a position where the distal end  13  of the optical fiber  12  extends or projects 30 mm±1 mm beyond the distal end  60  of the introducer sheath  40 . Accordingly, the second marking is preferably provided at 401 mm±1 mm or 501 mm±1 mm from the distal end  13  of the optical fiber  12 . 
   The markings  45 ,  46  may comprise any number of bands, colors, or forms for ease of recognition during a medical procedure, or be provided at other locations along the optical fiber  12  depending upon the length of the introducer sheath  40  and any friction seal that the optical fiber  12  is required to cooperate with. 
   An example of a use of the medical laser device is for use in endovenous laser treatment (EVLT) in human leg  100 . This will now be described in more detail with reference to FIG.  4 . Local anesthesia such as 0.3% or otherwise dilute lidocaine administered perivenously along the Greater Saphenous Vein (GSV)  200  and ultrasound guidance, are preferably used. Percutaneous entry into the Greater Saphenous Vein  200  is made with a needle at point  150 , 25-45 cm below the Saphenofemoral Junction (SFJ)  300 . A 0.035″ (0.089 cm) J-tip guide wire is passed into the Greater Saphenous Vein  200  and a five French introducer sheath  40  is passed over the guide wire and up to the Saphenofemoral Junction  300 . The guide wire is removed and a sterile 600 μm diameter core, bare-tipped optical fiber  12  is introduced into the vein  200  through the introducer sheath  40  until the first markings  45  is aligned with the proximal end  50  of the introducer sheath  40  (which corresponds with the portion of the friction seal furthermost from distal end  60 ). The optical fiber  12  and the proximal end  50  of the introducer sheath  40  are the fixed or held together. They are then moved together and positioned using ultrasound guidance at a location about 1-2 cm below the Saphenofemoral Junction  300  within the Greater Saphenous Vein  200 . Once positioned, the introducer sheath  40  is then released from the optical fiber  12  and the introducer sheath  40  is withdrawn relative to the optical fiber  12  until the proximal end  50  of the introducer sheath  40  is aligned with the second mark  46  on the optical fiber  12 . When the introducer sheath  40  and the optical fiber  12  are in this position then the distal end  13  of the optical fiber  12  will extend approximately 30 mm beyond the distal end  60  of the introducer sheath  40 . This position has been found to be an effective position for administering laser energy in EVLT treatment. An extension of 20 mm of the optical fiber  12  beyond the end of the introducer sheath  40  has been found to be the minimum suitable distance for administering laser energy in EVLT treatment without causing thermal damage to the introducer sheath  40 . The optical fiber  12  and the proximal end  50  of the introducer sheath  40  are then secured together with non-permanent means. Alternatively, if marking  45  is embossed then there may be sufficient co-operation between the marking  45  and the friction seal  42  of the introducer sheath  40  to secure them temporarily together. Pulsed 810 nm wavelength laser radiation from a laser energy source (not shown) is administered with a power of 10-12 Watts, in pulses of 0.8-1.0 second duration at 1 second pulse intervals to treat the Greater Saphenous Vein  200 . The introducer sheath  40  together with the optical fiber  12  are then slowly withdrawn in preferably 2-5 mm increments whilst administering the laser radiation, and manual compression is applied over a red aiming beam in order to achieve vein wall apposition around the laser fiber tip  34 . 
   In an embodiment, the cycle is activated and deactivated by a foot switch or hand switch. The clinician is instructed to withdraw the introducer sheath  40  2-3 mm between 1 second laser pulses. This process continues until the desired length of the vein has been treated. 
   In other embodiments the optical fiber  12  may be made of materials of comprise material combinations other than glass so long as the guiding properties of the core  32  of the optical fiber  12  are maintained i.e. providing the core  32  has a higher refractive index than the cladding  30 , and so long as the materials can operate in the temperature range −10° C. to 120° C. For, example any glass, plastic or hollow waveguide material could be used. 
   It will also be appreciated that the indicators of markings  45 ,  46  may be ink markings and the color of the markings  45 ,  46  may give information about their location. For example the first marker  45  may be colored differently to the second marker  46 . Alternatively, according to less preferred embodiments, the markings  45 ,  46  may be radio opaque and hence be capable of abservation by non-optical means. 
   Furthermore, it will be appreciated that other introducer sheaths commonly used in the art in interventional cardiology and electrophysiology procedures including angiography, angioplasty, stenting, atherectomy, temporary pacing, endomyocardial biopsies, transseptal catheterizations, electrophysiology studies, and RF ablations could be used. 
   Another embodiment of the present invention is contemplated, wherein the laser provides a continous rather than pulsed output. The laser may be activated by a foot or hand switch. Graduated markings are provided on the external surface of the introducer sheath  40  to provide control for withdrawing the introducer sheath  40  at a prescribed rate and to indicate how far the introducer sheath  40  has been withdrawn from the patient&#39;s body. A visable and/or audible indicator may be provided so as to assist an operator to remove the introducer sheath  40  and optical fiber  12  at a controlled speed. In one embodiment the visable and/or audible indicator may form part of the laser system coupled to the optical fiber  12 . As an example, if the markings on the external surface of the introducer sheath  40  were placed at 1 cm intervals, then the audible and/or visual indicator might be activated once per second thereby assisting a user to withdraw the introducer sheath  40  and the optical fiber  12  at a controlled speed of 1 cm/sec. An additional graduation on the introducer sheath  40  would therefore be revealed every time the indicator bleeped and/or flashed. 
   This embodiment has the benefit of potentially providing bio-feedback to control the rate at which the introducer sheath  40  is withdrawn. Furthermore, the continuous withdrawl results in a more uniform illumination of the internal surface of the blood vessel. According to the previously described embodiment using a pulsed laser source, the introducer sheath  40  and optical fiber  12  are withdrawn in a stepped manner which may in some circumstances cause relatively high intensity regions of illumination at, for example, 2-3 mm intervals along the blood vessel. Any such potential problem is therefore avoided by using a continuous laser source, providing graduations on the introducer sheath  40  and withdrawing the introducer sheath  40  in a controlled manner. 
   According to a further embodiment a visual and/or audible indicator may also be used in conjunction with the previously described embodiment which uses a pulsed laser as an aid to withdrawing the introducer sheath  40 . This allows a hybrid approach wherein the optical fiber  12  is withdrawn a longer distance e.g. 1-3 cm during a longer pulse-length. According to this embodiment, the laser source is operated in a quasi-continuous mode. 
   It will be appreciated that the above described embodiments are given by way of example only and that various modifications thereto may be made without departing from the scope of the invention.