Surgery – Instruments – Light application
Reexamination Certificate
2001-02-12
2003-03-25
Dvorak, Linda C. M. (Department: 3739)
Surgery
Instruments
Light application
C606S013000, C606S015000, C606S016000, C128S898000, C358S003050, C358S003050
Reexamination Certificate
active
06537270
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a medical handpiece which is connected with a laser radiation source via a beam guidance device and by which a laser beam is directed to a treatment area, wherein the handpiece is freely moveable relative to the laser beam source. The invention is further directed to a method for cosmetic treatment of skin surfaces using the handpiece according to the invention.
2. Description of the Related Art
In dermatology, laser radiation is frequently used for treatment of port-wine stains, for removal of tattoos, for skin resurfacing and for hair removal. Usually, short laser pulses with a pulse duration in the nanosecond range and microsecond range are introduced into the tissue for this purpose. Treatments of this kind serve primarily to improve the quality of life of the patient and are generally of a cosmetic nature.
The medical technical equipment for carrying out such treatments essentially comprises a laser radiation source and a handpiece which is used for manually directing the beam emitted by the laser radiation source onto the target area.
In order to achieve a lightweight construction of the handpiece and thus to enable the freest possible handling, the laser radiation source and handpiece are constructed as separate subassemblies, wherein the transmission of laser radiation from the radiation source to the handpiece is carried out by means of a movable beam guidance device. The beam guidance device can be formed of a plurality of rigid transmission members interconnected by joints or may also be constructed as a flexible fiber optic system.
The handpieces with which the invention is concerned have an in-coupling element at the transition from the beam guidance device and are outfitted with an emitting surface for the laser beam.
In known handpieces of this type, the emission of the laser beam is carried out with the same characteristics with which it is coupled into the handpiece, i.e., in particular, the distribution of the radiation intensity within the beam cross section and the geometry of the beam cross section are maintained to a great extent and the laser radiation is also directed to the treatment site in this way.
However, for many dermatological applications in which large areas of the skin are to be lased, repeated contiguous placement of the emitting surface is required during treatment in order to cover the entire area to be treated. In so doing, it is important for purposes of uniform treatment of the entire surface that the individual placement surfaces (spots) do not overlap on the one hand, but, on the other hand, also that no areas remain untreated between the placement surfaces.
In this regard, a laser beam with a circular cross section, for example, is disadvantageous because when round spots are placed next to one another there is always overlap or missed locations, so that a uniform radiation of energy into a treatment area is impossible. Accordingly, for effective treatment it is desirable to shape the beam at the emission-side end of the handpiece in such a way that a uniform introduction of energy is ensured when a plurality of spots are rastered on a treatment area.
This is also true for the energy distribution within the laser beam cross section. If the energy density at the edge of the laser beam cross section is less than that in its center, as is the case, for example, with a Gaussian energy distribution, it is not possible to achieve a uniform effect over the entire area of the beam cross section. With laser radiation having a Gaussian energy distribution, it is necessary during treatment to overlap the individual spots in order to achieve approximately continuous treatment results over the entire area to be treated. Of course, this is very difficult to accomplish and depends to a great extent on the sensitivity of the operator and, particularly with uncontrolled overlapping of edge zones, can result in a summing of the energy applied to the parts of the skin at individual locations on the treatment area, causing greater damage to the skin than is desired. Further, the more individual spots must overlap, the longer the duration of the treatment.
The Laid Open Application DE 44 29 193 A1 discloses a device for generating a laser beam with homogeneous cross section which is constructed as a medical handpiece within the meaning of the present new invention. This device can generate radiation which is homogenized with respect to mode and spatially as is required for ablation of the cornea.
A pulsed solid state laser with an emission in the wavelength range of 2 &mgr;m to 3 &mgr;m is used as radiation source. The pulse energy is between 100 &mgr;J and 1 J. A fiber having a length of at least 0.2 m and a diameter between 50 and 1000 &mgr;m is provided for transmitting the energy from the laser arrangement to the handpiece. A transparent rod with circular cross section comprising quartz, sapphire or YAG is provided inside the handpiece following the fiber.
By combining the fiber with the subsequent transparent rod, a beam with a rotationally symmetric intensity profile is achieved at the emission surface; with the latter, the mode mixture emitted by the laser can be effectively converted to the homogenized radially symmetric beam profile, for example, with Gaussian, parabolic or ring-shaped intensity distribution.
However, this handpiece is accordingly not suitable for applications requiring a uniform energy distribution over the entire beam cross section as described above.
OBJECT AND SUMMARY OF THE INVENTION
Based on this prior art, it is the primary object of the invention to further develop a handpiece of the type described above in such a way that a laser beam with a uniform intensity distribution extending to the edge zones of the beam cross section is made available at the emission surface and the geometry of the beam cross section is arranged in such a way that the risk of the target area being affected by unwanted introduction of energy is substantially reduced.
This object is met in a handpiece of the type mentioned above in that at least one optical element with a surface which is structured in the micrometer range and which is accordingly micro-optically active is provided inside the handpiece following the exit face of the beam guidance device.
The optical element with the transparent surface structured in the micrometer range can be realized as a micro-optic array which, by means of diffractive or refractive action, brings about a change in the intensity distribution within the laser beam cross section and/or a beam shaping such that there is a change in cross section.
In a construction of the invention, this surface has a diffractively acting structure whose width is in the order of magnitude of the wavelength of the laser beam utilized for treatment. This can be a height profile varying in this order of magnitude with stripe-shaped, cross-shaped, funnel-shaped and/or otherwise shaped raised portions, an index of refraction varying within the above-mentioned structure width and/or absorption coefficients varying within this structure width. Elements outfitted with surfaces of this type are described, for example, in Naumann, Schröder, “Bauelemente der Optik”, Carl Hanser Verlag, Munich, Vienna, 6th edition, page 584.
By means of the surface which is microstructured in this way, the energy distribution within the beam cross section is made uniform to the edge areas when the laser beam passes through this surface, i.e., a radiation intensity which is uniform over the cross section is present in the beam path following this surface over the entire beam cross section.
In a particularly preferred construction, the surface has a refractively acting structure in the form of an array of spherical, aspherical, cylindrical and/or elliptic lenses, wherein each of the lenses has an extension vertical to the beam direction of 10 &mgr;m to 1000 &mgr;m. These lenses can be arranged hexagonally and/or orthogonally on the surface. They can be concave dispersive lenses o
Elbrecht Jens
Kuehnert Juergen
Schroeder Eckhard
Zimmermann Gabriele
Asclepion-Meditec AG
Dvorak Linda C. M.
Farah A.
Reed Smith LLP
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