Surgery – Means for introducing or removing material from body for... – Gas application
Reexamination Certificate
2001-04-26
2004-06-22
Lo, Weilun (Department: 3761)
Surgery
Means for introducing or removing material from body for...
Gas application
C604S315000
Reexamination Certificate
active
06752778
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to an arrangement for the suction removal of waste products such as smoke and tissue particles in the ablation of biological tissue by means of laser radiation, wherein the laser radiation is directed to the tissue through the orifice of a tubular channel and the waste products are sucked through the orifice into the channel.
2. Description of Related Art
The removal of biological tissue by application of laser energy without thermal injury to the target areas is known. This semi-nonthermal process is used, for example, in medicine for cutting cartilage, hard tooth tissue, and skin areas as well as in ophthalmic surgery for shaping the cornea (photorefractive keratectomy). Processes of this kind and the associated equipment are disclosed, for example, in DE 197 27 573 C1 and EP 0 412 789 B1.
It is disadvantageous that waste products in the form of smoke or tissue particles occurring during the removal of tissue impair the air quality in the immediate vicinity of the treatment site resulting, on the one hand, in noxious odor for the patient and treating personnel and, on the other hand, in partial weakening of the laser radiation. The latter is especially significant in photorefractive keratectomy in which the surface of the cornea is shaped by precise removal of material. In this case, apart from the ability to direct the laser beam in an unimpeded and precise manner, it is also important that the radiation energy is introduced into the cornea with exactly constant intensity, so that the results of ablation can be achieved with the desired quality. However, the intensity is influenced by escaping smoke clouds and tissue particles crossing the laser beam, which can lead to irregular and therefor unwanted changes in ablation.
U.S. Pat. No. 5,344,418 describes an arrangement in which an applicator has flow channels for gases or air near the outlet opening for the laser beam, a flow of gas or air being directed from these flow channels to the treated tissue during treatment, which has the intended result that the troublesome ablated waste products are blown away from the treatment area.
Apart from the fact that this does not solve the problem of air contamination and noxious odor for the patient and operator, another disadvantage consists in that the air flow occurring relative to the surface of the treated biological substance disadvantageously leads to a drying out of this substance. This drying causes unpredictable and often excessive ablation.
The disadvantages mentioned above are also not overcome by the solution disclosed in U.S. Pat. No. 5,181,916. In this case, impurities are not blown away by the gas flow is directed to the treated area; rather, the smoke gases occurring at the treatment site are sucked off by means of the gas flow. A suction opening which is arranged concentrically about the orifice and through which the laser beam exits is used for this purpose. Because of the gas flowing away over the tissue, the tissue is also dried up in this case.
OBJECT AND SUMMARY OF THE INVENTION
Proceeding from this prior art, it is the primary object of the invention to reduce unwanted variations in laser radiation intensity could by ablation waste products while retaining the advantages of the elimination of ablation waste products by suction removal and also to avoid as far as possible drying out the treated substance.
According to the invention, in an arrangement of the type mentioned above, the inner wall of the channel has at least one outlet opening for a gas in the vicinity of the orifice and the flow of gas is directed to the center of the channel.
Further, in an arrangement of the type mentioned above, the inner wall of the channel has at least one outlet opening for a gas in the vicinity of the orifice, wherein the flow of gas is directed from the outlet opening substantially opposite to the radiating direction of the laser beam into the channel.
In a particularly preferred construction of the invention, the tubular channel has a portion which tapers conically toward the orifice.
Further, it lies within the scope of this invention that the tubular channel has, at least in the conically extending portion, two chambers extending concentrically around its circumference, one of which chambers is provided for guiding gas to the outlet opening. The second chamber is used for carrying the gas, which is sucked off and which entrains the waste products, out of the channel interior. For this purpose, the second chamber is connected with the channel interior by a suction opening on the one hand and is connected with a suction device via a suction line on the other hand.
It is effectively achieved by means of this arrangement that the gas does not flow through between the orifice and the treatment area so as to flow over the surface of the substance, but exits already from the orifice or from the immediate vicinity of the orifice accompanied by suitable pressure and is guided into the interior of the channel.
In this way, the underpressure or vacuum formed by the suction is predominantly or even completely balanced by the gas volume guided out through the outlet openings, with the result tat there is only a slight flow of air, if any, outside the channel, particularly between the orifice and the substance surface, and drying out can accordingly no longer occur.
The smoke occurring during treatment and coming from the treatment site and the tissue particles detaching from the latter move in the direction of the orifice, are acquired by the flow of gas or air within the tubular channel, and are carried off.
In advantageous constructions, outlet openings arranged in a radially symmetric manner about the center of the channel or, alternatively, an annularly extending outlet opening can be provided, for example. Both variants achieve comparable gas flow which is initially directed from the outlet openings into the mouth toward the center of the channel and then, due to the vacuum formed in the channel interior, is deflected opposite the direction of the laser beam into the channel.
The outlet openings are preferably expanded in the manner of a diffusor, so that the gas exits from these outlet openings with decreasing flow velocity and unwanted eddying of the gas flow is accordingly prevented. Above all, the gas exiting from the outlet openings is prevented from moving toward the treatment area due to eddying or excessive flow velocity out of the orifice.
In a particularly preferred construction of the invention, air is provided as gas and the outlet openings are connected with an air compressor or with a pressure vessel filled with air. Means for regulating the pressure of the supplied air and therefore also the flow velocity should advantageously be provided at the air compressor or at the pressure vessel. Such means e.g., pressure reducing valves, are sufficiently known in the prior art and need not be described in more detail.
Further, it can advantageously be provided that the inner wall of the channel has a plurality of suction openings arranged in a radial symmetric manner about the center of the channel and which communicate with a suction device. This arrangement also prevents a whirling of the air which exits from the outlet openings and is directed to the suction openings and carries the smoke gases and tissue particles, since it always only needs to travel a very short route between the outlet opening and suction opening.
The air flow takes place substantially close to the inner wall of the channel, while the center which is reserved for the laser beam is impaired only slightly by the air flow. Also, as a result of this, the smoke gas and tissue particles move and are discharged with the air flow extensively outside the laser beam, so that the energy impinging on the treatment area is not impaired in intensity by opaque particles or, if so, only to a substantially smaller extent than in the prior art.
It is further preferably provided that the total cross section of the outlet openings and the
Fiedler Joachim
Goder Claus
Schroeder Eckhard
Seitz Bernhard
Anderson C
Carl Zeiss Meditec AG
Lo Weilun
Reed Smith LLP
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