Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Light application
Patent
1996-03-28
2000-11-07
Shay, David M.
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Light application
607 92, 606 2, 606 10, 606 16, 606 17, 604 20, A61N 506
Patent
active
061430188
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention relates to a method of the type disclosed in the preamble to claim 1 and a device for performing the method.
It is known that laser radiation can be guided by means of optical waveguides, and the radiation transmitted in this manner can be introduced into biological tissue, either directly by means of the optical waveguide, transluminally or transcutaneously, or be additionally influenced purposefully in its distribution function by further measures--for example, by way of special catheters or endoscopes--and the radiation applied in this manner can be used to induce thermal or photochemical necroses. Since the mid-1970's it has been standard practice to introduce, for example, neodymium:YAG radiation into biological tissue in this manner and use the absorption of this radiation occurring in the tissue to heat the area of the tissue at the end of the fiber and thus effect coagulation necroses.
As dictated by the fact that the optical fibers employed have active diameters between 200 and 600 .mu.m, a very high power density results at the fiber/tissue boundary surface, even with low power outputs of the laser. Therefore, the carbonization threshold of the tissue is exceeded very rapidly, with the consequence that the exiting laser radiation is additionally absorbed by the carbonization product and can no longer penetrate corresponding to the optical coefficients typical for the tissue. Even the most commonly-used operator can only succeed in producing coagulation necroses having a 5 to 7 mm diameter, which typically accompany a carbonization of the tissue touching the fiber.
The transcutaneous introduction of the optical fiber, the so-called "bare fiber," is usually effected in an operation using puncture sets, i.e. with hollow metallic needles and trocars. Transluminal application using suitable flexible catheters or endoscopes is effected as a continuation.
A method for interstitial laser therapy is described in U.S. Pat. No. 5,169,396, the feature which distinguishes this method being that direct contact of the end surface of the fiber with the tissue is prevented by the placement of a fluid deposit with a biocompatible fluid which absorbs the laser radiation at the end of the puncturing needle. The primary result is that the fiber-tissue boundary surface is no longer heated, but instead the light-absorbing fluid is heated, which in turn warms the surrounding tissue by means of heat conduction.
Although this procedure prevents primary carbonization at the end of the fiber, it has the considerable disadvantage that the transport of energy into the tissue is only effected by heat conduction, and therefore leads to very limited coagulation necroses in view of the large heat sink of the surrounding tissue. Moreover, the method has the considerable disadvantage that the pigments or chromophoric groups of the fluid which absorbs the laser radiation also decompose photochemically or thermally at the fiber end with the radiation outputs used and the power densities stipulated by them, causing uncontrollable side effects.
In an arrangement known from DE 40 41 234, an attempt is made to resolve the problem of carbonization at the fiber-tissue boundary surface by specially preparing the fiber end in such a way that the laser radiation no longer exits the fiber pro-degree with a very small exiting aperture, but is scattered radially outwardly in steps from the fiber over a lengthy segment. The distribution of the laser power on the surface of the applicator is made more even by additional measures which further increase radial scattering, such as the provision of a scatter dome.
The goal of the most homogeneous possible introduction of the laser radiation into the tissue can be achieved extensively with these measures, but the technological expenditures involved in preparing the fiber end and possibly a high-temperature-resistant, yet flexible cover catheter are considerable. An additional disadvantage of this laser scatter light applicator having a cover catheter is that by nature the tis
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patent: 4336809 (1982-06-01), Clark
patent: 4612938 (1986-09-01), Dietrich et al.
patent: 4676231 (1987-06-01), Hisazami et al.
patent: 5489279 (1996-02-01), Meserol
patent: 5571151 (1996-11-01), Gregory
Beuthan Jurgen
Muller Gerhard
Roggan Andre
CeramOptec GmbH
Huttinger GmbH
Shay David M.
Skutnik Bolesh J.
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