DE4200587C1 - Light wave applicator for cutting and coagulating biological tissue - applies laser beam via flexible optical fibre having non-constant refractive index profile along its cross=section - Google Patents

Abstract

The applicator has a flexible light conducting fibre (2). The refractive index profile across the section of the fibre (2) is not constant. Light from a laser (3) is fed into the fibre (2) via a focussing lens (4). At the treatment end the fibre (2) has a free end so it can be accurately guided to the appropriate place in the human body to carry out the necessary treatment according to the adjusted beam angle. Between the feed in end and the treatment end is a manipulator (6). This can accurately provide a curve (8) in part of the fibre (2) for coupling the laser light over regions of different refractive indices. Thus, at the free end the light emerges with a large beam angle (13) for coagulation or, by unbending the fibre, with a small angle (13) for cutting. ADVANTAGE - Allows invasive treatment to be carried out quickly and simply.

Description

The invention relates to a light wave applicator, the one without serious surgical intervention Laser treatment in the human body enables. This is one of the best ways to cut tissue high light intensity at the destination required to achieve a high cutting effect. To this end are optical fibers with small numerical values Apertures are advantageous because the light beam is then with small opening angle emerges and at a preselected distance from the to be treated Make a small laser spot with a high one Luminous power density generated. Against is one Optical fiber with higher numerical aperture for Coagulate the tissue more advantageously. The Light beam occurs with a large opening angle off and generated at the selected distance a large spot of light on the area to be treated with a correspondingly low one Light power density.

To carry out such a laser treatment is in DE 38 33 992 A1 Optical fiber irradiation device for Laser cutting and coagulation are shown at the in a single fiber two laser light beams at an angle be coupled in, the first light beam on distal fiber end axially and the second light beam is broadcast circumferentially. A disadvantage of  the device according to the prior art is that uses an elaborately divided focusing optics will and to carry out the individual operational Process a complex switching technology is required.

Furthermore, the prior art, for example in DE 39 12 400 C1, an optical Step index fiber for the transmission of Laser light radiation with high power described which is a stepped profile in the core owns, the radiation in the core area is coupled. The fiber is suitable for small radii of radiation completely, d. H. without radiation losses, to the outside transferred in such a way that when a the bending radius determined the radiation from the inside Core area into an outer core area coupled over and then both in the core area as well is forwarded outside. Such Coupling effects are in telecommunications undesirable as they are too faulty Carry information transfers.

Against the background shown, it is the task of the invention, a light wave applicator for to further develop medical purposes so that its Use and its handling for cutting and Coagulate biological tissue quickly and can be done easily.

This object is achieved according to the invention with those specified in claim 1 Features resolved.  

In practice, laser treatment consists of Needs bleeding during the procedure by coagulating the tissue and the vessels to Bring to a standstill. This is according to the invention achieved by using an optical fiber with a special profile, with a manipulating part of the applicator defined Changes are caused such that the Beam angle of the laser radiation can be changed can. For this purpose, optical fibers with profiles used which light with different Apertures can lead. In particular, be there Gradient index profiles or stepped Step profiles preferred.

The manipulator of the fiber optic applicator consists of a mechanical part, the one defined S-shaped curvature in a partial area the optical fiber causes. The radii of curvature are so small that radiation overcoupling from an inner core of the fiber into one outer core area of the fiber. Without The radiation is particularly manipulated by the fiber through total reflection within the core forwarded and occurs at the distal end of the fiber with the minimum numerical aperture. Becomes instead the fiber is manipulated by means of a Subject to S-shaped curvature, so couples to the Radiation point radiation from the core area into the  outer core area, and the radiation is in the further course both in the core area and in surrounding outer area. At the distal end then the radiation occurs at a maximum Numerical aperture. In the first case, the Laser radiation for cutting, in the second case for Coagulation used. By using a Manipulator to initiate the Coupling effect was in an optical fiber advantageously achieved that the Laser treatment in the human body simplified was, the radiation device itself is much cheaper to manufacture.

According to an expedient embodiment of the invention is a compressive force by means of the manipulator Curvature of the fiber can be applied. A loading or relieving pressure force by means of the manipulator To initiate means for the attending doctor easy handling of the applicator in order to human body in the area to be treated quickly and easily after the cutting process initiate immediate hemostasis treatment.

The manipulator is expediently a resilient Strap clamp designed the optical fiber by means of clamping pins arranged offset at the ends pinched, with a clamping pin over the fiber and the opposite clamping pin the fiber reaches under.

According to an advantageous embodiment of the Invention has the strap clamp on the overlapping Area a push button with a stamp on it can be pressed against the optical fiber during the clamping process is, the gripping pin below Optical fiber between the overarching  Clamp pin and the stamp jammed. Through this The optical fiber is clamped into one S-shaped curvature pressed to that described coupling effect leads.

According to one embodiment of the invention Optical fiber is a step index fiber with a Core area and a cladding, with the glass core has two-stage refractive indices in the way that the refractive index of the inner core area is larger than the refractive index of the outer Core area and the glass jacket a smaller one Refractive index has as the outer core area.

According to a development of the invention Optical fiber is a step index fiber with a Glass core and a coat from one Plastic coating, whereby the glass core has a higher Refractive index has as the plastic sheath and the coating consists of two coating layers, one of which the inner layer has a refractive index, which is lower than the refractive index of the outer layer.

According to a further embodiment, the Optical fiber is a step index fiber with a Core area, an intermediate jacket, another Core area and a fiber cladding, the inner Core area has a smaller refractive index than the outer core area and the intermediate jacket one has a smaller refractive index than the inner one Core area and the fiber cladding a refractive index that is less than or equal to the refractive index of the intermediate coat.

After further appropriate training of Invention has a core and the optical fiber a coat, the core one  has gradient-shaped refractive index curve, which in essentially follows an r² law, whereby the core at the interface to the cladding one has a smaller refractive index than the core center.

In further training, the level index fiber has one Core and a coat on, the core one has gradient-shaped refractive index curve, which in essentially runs according to an r² law that Core area from the jacket through an intermediate jacket is separated and the intermediate sheath a smaller one Refractive index has as the core area.

The invention will now be described with reference to the figures schematically illustrated embodiments explained. It shows

Fig. 1 is a schematic view of an applicator according to the invention,

Fig. 2 is a partial sectional view of a manipulator in the relaxed position,

Fig. 3 is a partially sectioned step index fiber in the relaxed position of FIG. 2,

Fig. 4 shows a further partial sectional view of a manipulator in the cocked position,

Fig. 5 is a partially sectioned, S-shaped curved step-index fiber according to Fig. 4,

Fig. 6 is a schematic representation of the refractive index curve along the cross-section of an embodiment of a step index fiber,

Fig. 7 is a further schematic representation of the refractive index curve along the cross-section of a step index fiber in another embodiment.

Fig. 1 shows a schematic representation of a Lichtwellenapplikators for cutting and coagulation of biological tissue. The applicator has an armored optical waveguide 1 with a flexible optical step index fiber 2 , into which the light of a laser 3 is coupled at the end via a focusing device 4 . To disconnect or replace the optical waveguide 1 , an optical plug 5 is provided at its coupling end, which can be connected to the focusing device 4 .

On the treatment side (distal), the step index fiber 2 can be guided specifically to the site to be treated in order to carry out the desired treatment in the human body in accordance with the radiation angle 13 . Between the coupling end and the free treatment-side end of the optical waveguide 1 , a manipulator 6 is arranged, which can give a curvature 8 in a partial area of the optical waveguide 1 to the step index fiber 2 , so that at the free treatment-side end the laser light at a large radiation angle 13 for coagulating Tissue or when the optical waveguide 1 is bent, a small radiation angle 13 emerges for the cutting treatment.

For the curvature 8 of the step index fiber 2 ( FIG. 4), a pressure force is exerted on the step index fiber 2 via a push button 7 on the manipulator 6 , so that the overcoupling effect arises in the step index fiber 2 for the coagulation treatment. When the pushbutton 7 ( FIG. 2) is relieved, the curvature 8 recedes, so that the overcoupling effect is eliminated and the irradiation device can be used for cutting. This is done by a simple, relieving hand movement of the treating doctor on manipulator 6 .

The manipulator 6 itself is designed as a spring clip 9 . The yoke clamp 9 has clamping pins 10, 11 which are offset at the end and which clamp the step index fiber 2 in the manner of pliers. The clamping pin 10 engages over the step index fiber 2 from above, the clamping pin 11 reaching under the step index fiber from below. The pushbutton 7 , which cooperates with a stamp 12 , is connected to the overlapping area of the strap clamp 9 .

During the clamping process, the punch 12 is pressed against the step index fiber 2 from above. The resulting S-shaped curvature 8 takes place in that the lower clamping pin 11 presses in between the upper clamping pin 10 arranged above and the punch 12 .

Fig. 3 shows the step index fiber 2 with the refraction profiles n₁, n₂ and n₃ without the manipulator 6 in the non-curved state. Without special manipulation of the step index fiber 2 , the radiation is passed on by total reflection within the core 14 with the refractive index n 1 , so that the radiation with the minimal numerical aperture emerges at the distal end of the step index fiber 2 . If, instead, the step index fiber 2 , as shown in Fig. 4, is subjected to an S-shaped curvature 8 , the radiation couples from the core region 14 with the refractive index n 1 to the surrounding core region 15 with the refractive index n 2 at the point of curvature 8 and then occurs at the distal end with the maximum numerical aperture.

Because of this simple actuating device, the step index fiber 2 can be used for cutting, shown in FIGS. 2 and 3, and for coagulation, shown in FIGS. 4 and 5.

The step index fiber 2 can have different embodiments. In an embodiment with a stepped refractive index profile, shown in Fig. 6, the laser beam is focused into the inner core area with the refractive index n 1. It must apply that the radiation product (R _L × D _L ) of the laser beam is less than or equal to the corresponding size 2 × NA₁ × D₁ of the fiber, where NA₁ is the numerical aperture and D₁ is the diameter of the inner core region of the fiber. The beam product is an important parameter of the beam. For a beam that is rotationally symmetrical to the axis, it is the product of the diameter D in meters with a full divergence angle R in rad of the beam at its narrowest point (waist). The corresponding size for a fiber is the product of the full acceptance angle of the fiber core R _F with the diameter D _{K of} the fiber core in meters. Approximately, the full acceptance angle R _{F of} the fiber is generally expressed by the value 2NA, where NA is the numerical aperture of the fiber and the relationship applies: sin (R _F / 2) = NA.

The numerical aperture is determined by the Refractive index difference between the radiation-guiding Layer with the refractive index n 1 and Neighboring layer with the refractive index n₂:

to NA₁ = (n₁²-n₂²) ^1/2 .

It is assumed that n₁ <n₂ applies. From the specification of the numerical aperture, the Specialist with knowledge of the fiber components correct refractive indices or refractive index ratios specify.

As an example, the refractive index profile of a fiber is shown in Fig. 6, which has a core with the refractive indices n₁ and n₂, with n₁ <n₂ and a jacket with the refractive index n₃, where n₂ <n₃. A laser beam

with (R _L × D _L ) 2NA₁ × D₁, wherein

NA₁ = (n₁²-n₂²) ^1/2

and D₁ is the diameter of the core A, is in the Core area focused.

Without manipulation ( Fig. 3) of the fiber, the radiation is transmitted through total reflection within the core 14 and emerges at the distal end of the fiber with the minimum numerical aperture NA 1. Instead, the fiber z. B. by means of the manipulator 6 ( FIG. 5) subjected to an S-shaped curvature 8 , radiation couples from the core area 14 into the core area 15 at the point of curvature, and the radiation is subsequently developed both in the core area 14 and in the core area 15 guided. The radiation then emerges at the distal end with a numerical aperture

NA₃ = (NA₁² + NA₂²) ^1/2 ,

in which

NA₂ = (n₂²-n₃²) ^1/2

is. In the first case ( Fig. 3) the laser radiation is used for cutting, in the second case ( Fig. 5) for coagulation.

According to a further embodiment, the same effect can be achieved if, instead of a double core 14, 15, a simple core with the refractive index n 1 is used, but the fiber covering is designed in a double layer such that the first covering layer has a refractive index n 2, which is smaller than the refractive index n₃ of the fiber cladding. Here again applies n₁ <n₂ <n₃. After actuation of the manipulator 6, the radiation is guided both in the fiber core and in the fiber jacket.

In a third embodiment, the fiber, whose refractive index profile is shown in Fig. 7, consists of a core region D with the refractive index n 1, which is separated by an intermediate cladding layer Z with the refractive index n 2 from a further core region E with the refractive index n 3. The fiber cladding G with the refractive index n₄ adjoins the core region E. The condition n₃ <n₁ <n₂n₄ applies.

The laser radiation is in turn in the core D. the refractive index coupled n₁ and occurs on distal fiber end with the numerical aperture

NA₁ = (n₁²-n₂²) ^1/2

out. If the manipulator 6 is actuated, laser radiation couples at the point of curvature 8 via the intermediate cladding Z into the core region E with the refractive index n 3 and is then guided both by the core D and preferably by the core E and occurs at the distal fiber end with the numerical aperture

NA₃ = (n₃²-n₄²) ^1/2.

According to a further embodiment, not shown, the core region of a fiber with a cladding has a gradient-shaped refractive index profile, which essentially runs according to an r² law, and has a refractive index n 1 in the middle of the fiber and a refractive index n 2 at the interface with the fiber cladding with n 1 <n 2 . The core area of the fiber is oversized so that the beam product (R _L × D₁) of the laser is relatively small and for an r² fiber is given by (NA × D _K ), whereby

NA = (n₁²-n₂²) ^1/2

is. The laser radiation is coupled into the fiber in such a way that the laser modes with a flat wavefront spread in the fiber, as is the case, for. B. at A.Gerrard, HM Burch, Introduction to Matrix Methods in Optics, Chapter III, 9. When the manipulator 6 is not actuated, the laser radiation thus only propagates in a small area in the center of the core and emerges at the distal end with a smaller numerical aperture than the relationship

NA = (n₁²-n₂²) ^1/2

corresponds.

After the manipulator 6 has been actuated, mode-coupling effects are triggered by the induced fiber curvature 8 in such a way that the laser radiation now propagates along the entire fiber core and at the distal end of the fiber with the numerical aperture

NA = (n₁²-n₂²) ^1/2

exit.

Claims (9)

1. Light wave applicator for cutting and coagulating biological tissue by means of laser radiation, which has a flexible optical fiber ( 2 ) with a refractive index profile that is not constant over its cross-section, the numerical aperture of the optical fiber being selectively and reproducibly changeable by actuating a manipulator ( 6 ), the Manipulator ( 6 ) is able to impart a curvature ( 8 ) to the optical fiber ( 2 ) in one of its partial areas, in such a way that the laser light is coupled over areas of different refractive indices of the optical fiber ( 2 ). 2. Optical wave applicator according to claim 1, in which by means of the manipulator ( 6 ) a compressive force can be applied to the optical fiber ( 2 ) to generate the curvature ( 8 ), the coupling of the laser light taking place in the curvature region of the optical fiber ( 2 ) for coagulation and Relief of the pressure force the radiation can be used for cutting. 3. Optical wave applicator according to claim 1 or 2, in which the manipulator ( 6 ) is designed as a resilient clamp ( 9 ) which clamps the optical fiber ( 2 ) by means of distally offset clamping pins ( 10, 11 ), the clamping pin ( 10 ) Optical fiber ( 2 ) overlaps and the opposing clamping pin ( 11 ) engages under the optical fiber. 4. Optical wave applicator according to one of claims 1 to 3, in which the strap clamp ( 9 ) on the overlapping area has a push button ( 7 ) with a stamp ( 12 ) which can be pressed during the clamping process against the optical fiber ( 2 ) and in which the lower grip Clamping pin ( 11 ) clamps the optical fiber ( 2 ) between the overlapping clamping pin ( 10 ) and the stamp ( 12 ). 5. Optical wave applicator according to one of claims 1 to 4, in which the optical fiber ( 2 ) is a step index fiber with a core and a cladding, the core having double-stage refractive indices, in such a way that the refractive index (n₁) of the inner core region is larger than the refractive index (n₂) of the outer core area and the cladding has a smaller refractive index (n₃) than the outer core area. 6. Optical wave applicator according to one of claims 1 to 4, wherein the optical fiber ( 2 ) is a step index fiber with an inner core region (D), an intermediate sheath (F), an outer core region (E) and a fiber sheath (G), wherein the inner core region (D) has a smaller refractive index (n₁) than the outer core region (E), the intermediate cladding (F) has a smaller refractive index (n₂) than the inner core region (D) and the fiber cladding (G) has a refractive index (n₄) has less than or equal to the refractive index (n₂) of the intermediate cladding (F). 7. Optical wave applicator according to one of claims 1 to 4, wherein the optical fiber ( 2 ) is a step index fiber with a core and a jacket made of a double-layer plastic coating, the core having a higher refractive index (n₁) than the jacket and the coating of two Layers exist, of which the inner layer has a refractive index (n₂) which is lower than the refractive index (n₃) of the outer layer. 8. Optical wave applicator according to one of claims 1 to 4, in which the optical fiber ( 2 ) has a core and a cladding, the core having a gradient-shaped refractive index profile, which essentially follows an r² law, and the core at the interface to The cladding has a smaller refractive index than the core center. 9. Optical wave applicator according to one of claims 1 to 4, wherein the optical fiber ( 2 ) has a core and a cladding, the core having a gradient-shaped refractive index profile, which runs essentially according to an r² law and the core area from the cladding area through an intermediate cladding which has a smaller refractive index than the core area.