Surgery – Instruments – Light application
Patent
1995-02-09
1999-11-23
Nasser, Robert L.
Surgery
Instruments
Light application
607 89, A61B 1736
Patent
active
059892463
DESCRIPTION:
BRIEF SUMMARY
PROBE FOR HEATING BODY TISSUE
The invention relates to a probe for heating body tissue according to the generic part of claim 1.
Since 1983 (Bown S G, World J. Surg, 1983, 7, 700-709), lasers have been used for interstitial tumor therapy. The method intends to achieve a controlled, and, to the largest possible extent, homogeneous heating of sufficiently large tissue volumes (diameter>2 cm) by means of the introduction of light via light guides. The main advantage of the method consists in the fact that only a thin puncture channel (<2,55 mm) is necessary to give the surgeon access to the tumor. This minimally invasive technique is especially suited for treating deep-seated tumors which are inaccessible to other therapeutical methods. Since tumor cells are considered to be particularly sensitive to heat (Lambert A R; JAMA; 1912, 59, 2147-2148), a relatively slight increase in temperature by approximately 7.degree. C. to 9.degree. C. during a period of a few minutes is sufficient for destroying the tumor. It is therefore a pre-condition of successful "interstitial thermotherapy" that the tumor is heated by at least this temperature also in its peripheral areas.
When using conventional light guides for introducing energy (Bare Fiber; ITT-Faser.RTM. DE 38 13 227), however, an undesirable temperature profile is created in the tissue in that temperature decreases abruptly as tissue depth increases. As a consequence, a therapeutically effective temperature increase is only present in an area having a diameter of a few millimeters around the site of introduction (Masters A, Bown S G, Las. Med. Sci; 1990, 5, 129-136; Svaasand L O, et al., Las. Med. Sci; 1990, 5, 121-128). This is insufficient for treating most clinically relevant tumors. The radiation power can only be increased within narrow limits, since an increase may result not only in vaporization or carbonization of tissue, but subsequently also in the destruction of the fiber itself. The power output from a glass fiber (bare fiber) typically having a diameter of 600 .mu.m is thus limited to a few Watt, which largely prevents therapeutic use of the principle in practice.
In principle, this problem could be somewhat diminished by increasing the diameter of the fiber and the output surface. This is in conflict, however, with the desired aim of keeping the outer diameter of the whole system as small as possible.
There have also been several attempts to solve the problem by using so-called diffusor elements specifically designed for the purpose. In general, these are intended to reduce the power density at the output site and, at the same time, ensure homogeneous solid angle distribution of the radiated energy. Hollow spherical or cylindrical diffusor elements are known whose cavities are in part filled with glass particles of a defined size (Heinze A, et al, SPIE; 1990, 1201, 304-312). For transmitting sufficiently high radiation energy, however, the output surface has to be enlarged to such an extent that the resulting increase in the size of the diffusor elements is inacceptable. A further problem is that the commonly used scattering particles put an additional heat load on the output portion due to their self-absorption. Materials for the isotropic scattering of laser light (e.g. Star W M, et al, Photochem. Photobiol.; 1987, 46, 5, 619-624) for high power densities at optical border surfaces (>7 kW/cm.sup.2) have not yet been disclosed. Furthermore, there is as yet no possibility of varying the solid angle distribution of the radiated beam in a simple manner and according to choice. Likewise, the problem of the abrupt decrease in temperature within the tissue itself has not yet been solved. In principle, one could achieve a substantially homogeneous temperature distribution within a tissue volume by actively cooling the introduction surfaces. However, this means that a considerable portion of the total energy being introduced has to be removed again by active cooling. To achieve sufficient heating (increase in temperature by 7.degree. C. to 9.degre
REFERENCES:
patent: 1550197 (1925-08-01), Berry
patent: 1721019 (1929-07-01), Hert
patent: 2074034 (1937-03-01), Ackerman
patent: 4509344 (1985-04-01), Ludwigsen et al.
patent: 4967765 (1990-11-01), Turner et al.
patent: 5019075 (1991-05-01), Speers et al.
patent: 5129896 (1992-07-01), Hasson
patent: 5165773 (1992-11-01), Nath
patent: 5169396 (1992-12-01), Dowlatshahi et al.
patent: 5190540 (1993-03-01), Lee
patent: 5196005 (1993-03-01), Doiron et al.
patent: 5209748 (1993-05-01), Daikuzono
patent: 5281213 (1994-01-01), Milder et al.
patent: 5304171 (1994-04-01), Gregory et al.
patent: 5415654 (1995-05-01), Daikuzone
patent: 5441497 (1995-08-01), Narciso, Jr.
Kaufmann Raimund
Schwarzmaier Hans-Joachim
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