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Infrared Laser Catheter Apparatus

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Infrared Laser Catheter Apparatus ~" ' MM II II II Ml II I II III II II II I II J European Patent Office © Publication number: 0 214 712 B1 Office_„. europeen- desj brevets^ » © EUROPEAN PATENT SPECIFICATION © Date of publication of patent specification: 02.09.92 © Int. CI.5: A61 B 17/00, A61B 17/36 © Application number: 86303982.2 @ Date of filing: 27.05.86 © Infrared laser catheter apparatus. ® Priority: 31.07.85 US 761188 © Proprietor: C.R. BARD, INC. 731 Central Avenue @ Date of publication of application: Murray Hill New Jersey 07974(US) 18.03.87 Bulletin 87/12 @ Inventor: Slnofsky, Edward © Publication of the grant of the patent: Apartment 8 South Washington Street 02.09.92 Bulletin 92/36 Reading Massachusetts(US) © Designated Contracting States: DE FR GB IT NL © Representative: Woodward, John Calvin et al VENNER SHIPLEY & CO. 368 City Road © References cited: London EC1V 2QA(GB) EP-A- 0 153 847 GB-A- 2 017 506 GB-A- 2 125 986 US-A- 3 327 712 US-A- 4 383 729 US-A- 4 458 683 ELECTRONIC DESIGN, vol. 17, no. 13, June 21, 1969, pp 36, 38, 40 D.N. KAYE: "The happy merger of fiber optics and lasers" 00 CM s O Note: Within nine months from the publication of the mention of the grant of the European patent, any person ^ may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition qj shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid (Art. 99(1) European patent convention). Rank Xerox (UK) Business Services 1 EP 0 214 712 B1 2 Description laser is very short, typically about ten nanoseconds. In order to develop reasonable aver- This invention relates to a laser catheter ap- age power, pulses with extremely high peak power paratus for generating and transmitting energy to a must be used. When an attempt is made to chan- surgical site in a living body for the purposes of 5 nel such a high peak power output into an optical tissue removal or repair. fiber, the high peak power destroys the fiber. Thus, While lasers have been used for many years excimer lasers have a practical power limit which is for industrial purposes such as drilling and cutting relatively low. Consequently, when these lasers are materials, it is only recently that surgeons have used for biological tissue removal, the operation is begin to use lasers for surgical operations on living 10 slow and time consuming. tissue. To this end, laser energy has been used to The CO2 laser has other drawbacks. This laser repair retinal tissue and to cauterize blood vessels generates output energy with a wavelength on the in the stomach and colon. order of 10 micrometers. At this wavelength, the In many surgical situations, it is desirable to absorption of blood hemoglobin is negligible but transmit laser energy down an optical fiber to the 15 the absorption by water and tissue is relatively surgical location. If this can be done, the optical high. Scattering at this wavelength is also very low. fiber can be included in a catheter which can be Although the CO2 laser possesses favorable char- inserted into the body through a small opening, acteristics for surgical applications in that it has low thus reducing the surgical trauma associated with scattering and high absorption in tissue, it suffers the operation. In addition, the catheter can often be 20 from the same drawback as excimer lasers in that maneuvered to surgical sites which are so restrict- the absorption length is relatively short due to the ed that conventional scalpel surgery is difficult, if high absorption of the laser energy in water. Thus, not impossible. For example, laser energy can be the surgical area must be cleared of blood prior to used to remove atherosclerotic plaque from the the operation. walls of the vasculature and to repair defects in 25 Unfortunately, the CO2 laser also suffers from a small-diameter artery walls. serious additional problem. Due to the long A problem has been encountered with laser wavelength, the output energy from the carbon surgery in that prior art lasers which have been dioxide laser cannot be presently transmitted down used for industrial purposes often have characteris- any optical fibres which are suitable for use in tics which are not well suited to percutaneous laser 30 percutaneous surgery (present fibres which can surgery. For example, a laser which is convention- transmit energy from a CO2 laser are either com- ally used for scientific purposes is an excimer laser posed of toxic materials, are soluble in water or are which is a gas laser that operates with a gas not readily bendable, or possess a combination of mixture such as Argon-Fluorine, Krypton-Fluorine the previous problems) and, thus, the laser is only or Xenon-Fluorine. Another common industrial laser 35 suitable for operations in which the laser energy is the carbon dioxide or CO2 laser. can be either applied directly to the surgical area Both the excimer laser and the CO2 laser have or applied by means of an optical system com- been used for surgical purposes with varying re- prised of prisms or mirrors. sults. One problem with excimer lasers is that they David N. Kaye describes in his article "The produce output energy having a wavelength in the 40 happy merger of fibre optics and lasers" two meth- range 0.2-0.5 micrometers. Blood hemoglobin and ods of combining fibre optics and lasers as a tool proteins have a relatively high absorption of energy to reach locations which are not accessible with in this wavelength range and, thus, the output large fixed lasers. Among several laser/fibre com- beam of an excimer laser has a very short absorp- binations an Er:Glass laser for medical and indus- tion length in these materials (the absorption length 45 trial use is proposed. This laser emits a pulsed is the distance in the materials over which the laser radiation of 1 .54 urn so as to eliminate retinal eye beam can travel before most of the energy is damage. Most of the lasers described operate in absorbed). Consequently, the surgical site in which continuous wave mode so they cannot be used for these lasers are to be used must be cleared of the successful removal of plaque. References are blood prior to the operation, otherwise most of the 50 also made to several materials which can be made laser energy will be absorbed by intervening blood to lase at various wavelengths but the only use of before it reaches the surgical area. While the re- the equipment described is for the treatment of the moval of blood is possible if surgery is performed eye rather than for plaque removal deep within the on an open area it is often difficult if surgery is to body. Indeed, none of the equipment described be performed via a catheter located in an artery or 55 could be used for this purpose. vein. GB-A-2017506 discloses a laser tunnelling de- An additional problem with excimer lasers is vice in which a thrombus in a blood vessel is that the output energy pulse developed by the destroyed by the use of laser light fed through an 2 3 EP 0 214 712 B1 4 optical fibre received in a catheter inserted into a tromagnetic energy scattering versus blood vessel. However, there is no discussion or wavelength. suggestion in this reference that atherosclerotic Figure 2 shows an absorption versus wavelength plaque could be removed by this method, and plot for atherosclerotic plaque obtained in a ca- there is no suggestion of the parameters required 5 rotid endarterectomy with the region of interest to achieve such plaque removal. for the inventive laser sources (1.4-2.2 microm- It is an object of the present invention to pro- eters) outlined. vide a laser catheter which is capable of providing Figure 3 of the drawing is a schematic diagram laser energy that can be transmitted through an of a typical solid state laser construction used in optical fibre under such conditions as to achieve io the inventive laser sources. plaque removal. Figure 4 of the drawing is a plot of laser output In accordance with the present invention there intnsity versus time for a typical pulse shape is provided a laser catheter apparatus for surgically developed by a laser shown in Figure 3 when removing atherosclerotic plaque from a surgical used for tissue removal. site within the body, comprising a flexible catheter is Figure 5 is a schematic diagram of a laser member, a laser energy source and an optical fibre catheter which employs a single optical fiber for located within a lumen defined within the catheter transmitting laser energy to a surgical location. member, the optical fibre being composed of a Figure 6 of the drawing is an enlarged cross- substantially non-toxic material and being tolerant section of the probe tip the single fiber catheter to the operation of the laser source, wherein the 20 shown in Figure 5. output of the laser source is directed into the Figure 7 of the drawing shows the manner in proximal end of the optical fibre, propagated along which the fiber is inserted into the fiber holder. the optical fibre, and is directable by means at- Figure 8 is a schematic diagram of a wire- tached to the distal end of the optical fibre to the guided catheter which employs four optical fi- surgical site, the catheter member and optical fibre 25 bers to increase the area which can be irradi- being sufficiently flexible and being dimensioned to ated with the laser light.
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