Patent Application
20150005813
The invention relates to a surgical instrument which can also be employed under the conditions of a magnetic resonance tomograph (MRT).
Conventional surgical instruments, such as biopsy forceps, in particular for myocardial biopsies, such as are known, for example, from DE 101 59 584 A1, comprise a forceps element having a forceps base and at least two forceps fingers guided such that they can move relative to one another on the forceps base, as well a manual actuation element for opening and closing the forceps element and an elongated, flexible actuation cable which connects the manual actuation element to the forceps element and has a tubular, flexible cable sheath connected to the forceps base and a flexible cable core which is guided displaceably in the cable sheath and is connected to the forceps fingers for opening and closing the forceps element.
In conventional biopsy forceps of this type, the components of the forceps element are made of non-rusting steel. The cable sheath of the actuation cable is constructed as spiral coiled spring and, like the cable core usually constructed from wire, is likewise made of metal, usually stainless steel.
The known biopsy forceps cannot be employed under the conditions of a magnetic resonance tomograph (nuclear spin tomograph) since the forceps element and the actuation cable generate artefacts in the imaging in which the image, in particular of the forceps element, depending on the location and imaging scale, does not correspond to the actual position of the forceps element in the patient's body and can completely overlap or falsify relevant areas. This makes evaluation of the image difficult. Furthermore, the forceps element and the actuation cable may heat up in the magnetic field.
The actuation cable of biopsy forceps of the type in question has a comparatively small diameter of, for example, 1.0 to 3 mm, but with a length of, for example, 50 cm to 1.4 m is comparatively long. Under the frequency conditions of the magnetic resonance tomograph, the elongated components of the actuation cable but also of the forceps element may heat up inductively and damage surrounding tissue, particularly if electromagnetic fields of the tomograph create resonance conditions on the actuation cable. Furthermore, because of the strong magnetic field of the tomograph, no ferromagnetic materials should be present, particularly on the forceps element or the actuation cable, in order to exclude the magnetic field of the tomography from undesirably deflecting the forceps element and the actuation cable.
Similar problems also result with other surgical instruments, for example instruments with the aid of which surgical components, such as occluders or vessel clips or stents, such as are known e.g. from WO 2010/130617 A1, are to be put in place under MRT conditions. In such instruments, the surgical component is held on a hook-like gripping device and is detached from the gripping device after placement in the body of the patient.
The object of the invention is a surgical instrument which can also be employed under the operating conditions of a magnetic resonance tomograph, in particular under real time conditions, and generates adequately image-true artefacts.
The invention is based on a surgical instrument which comprises:
The object explained above is achieved according to the invention in that at least the tool element of the surgical tool, but in particular also the tool base thereof, is made substantially of a non-ferromagnetic or substantially non-ferromagnetic metal or of ceramic or of plastic, and in that the cable sheath and the cable core are each made of an electrically non-conducting or substantially non-conducting composite material in which a plurality of reinforcing threads are embedded in a plastics matrix.
It has been found that conventional materials which can be employed in magnetic resonance tomographs as a rule do not meet the requirements imposed on the actuation cable of a surgical instrument, in particular a gripper instrument. In order to be able to reliably actuate the surgical tool arranged on the distal end of the actuation cable, it must be possible to exert a force of from 20 to 40 N, possibly even more than 100 N, based on the cable sheath, many times on the surgical tool via the cable core. Since the actuation cable is comparatively thin and long, several times this force, for example 100 to 300 N, must be exerted on the cable core, based on the cable sheath, at the manual actuation element in order to be able to overcome the friction in the actuation cable, especially since tangential losses of force occur due to bends in the actuation cable during operation. It has furthermore been found that conventional plastics materials such as can be employed in a magnetic resonance tomograph are not adequately resistant to elongation, so that they are only inadequately elongation-resistant under the force conditions mentioned. Adequately high actuation forces on the tool element lead in this manner to excessively long actuation paths on the manual actuation element in the case of conventional MRT-suitable plastics materials. It has been found, surprisingly, that the abovementioned problems can be overcome if the cable sheath and the cable core are each made of an electrically non-conducting or substantially non-conducting composite material in which a plurality of reinforcing threads are embedded in a plastics matrix. The reinforcing threads increase the tensile and compressive strength of the cable sheath and cable core even under the operating conditions of the magnetic resonance tomograph. The cable sheath has a tubular shape. It goes without saying that the tube forming the cable sheath optionally can also have several lumina separated from one another.
Since the tool element and optionally also the tool base is/are substantially made of non-ferromagnetic metal, that is to say of diamagnetic or paramagnetic material or of ceramic or of plastic, they can be exposed to the strong magnetic field of the tomograph without being deflected or displaced by the magnetic field. Titanium, in particular, is suitable, but platinum, gold, silver, copper or aluminium or alloys based on such metals are also suitable. If in particular the tool element is made of metal or ceramic, it is adequately resistant to wear and can optionally be provided with cutting edges or the like for severing tissue. The cable sheath and the cable core are electrically non-conducting and accordingly do not heat up under the operating conditions of the tomograph, that is to say they can also be employed with tomographs having a particularly high magnetic field strength of more than 3 T. It is essential that the cable sheath and the cable core are made of a composite material in which reinforcing threads are embedded in a plastics matrix and impart to the cable sheath and the cable core adequate tensile and compressive rigidity and also adequate torsional rigidity in order, for example, to be able to open and close but also rotate a forceps tool manually by means of the manual actuation element with a definable use of force, for example for the removal of biopsy samples.
In a preferred embodiment, the surgical tool is constructed as a holding tool having a gripping device which forms the tool element and is guided such that it can move relative to the tool base forming a holding base, the manual actuation element for opening and closing the holding tool via the cable core being connected to the gripping device.
The tool element or the gripping device can be a coupling piece, in particular a hook or the like, as is known for putting in place an occluder or a vessel clip or a stent. Preferably, the surgical instrument is constructed as a gripper instrument, in which the surgical tool is constructed as a forceps tool and comprises, on a forceps base connected to the cable sheath, at least two forceps fingers which are guided such that they can move relative to one another on the forceps base. The forceps fingers in turn are connected to the cable core for opening and closing the forceps tool.
It goes without saying that the forceps tool of the gripper instrument can be configured in various ways. Thus, for example, the forceps fingers can be constructed as spoons which are linked to the forceps base and connected to the cable core via a steering gear, for example in the form of a scissors gear, as is known, for example, from DE 101 59 584 A1. Alternatively, however, the forceps fingers can also be constructed, as is usual in the case of holding forceps, such that they are spring-mounted radially to the cable sheath and firmly connected to the cable core, so that by means of the cable core they can be drawn into an end region of the cable sheath forming the tool base for closing the forceps tool. When the forceps fingers are pushed out of this end region, they spread away from one another to open the forceps tool. The gripper instrument can also be a collecting basket or the like which spreads out in a sprung manner. Alternatively, however, the gripper instrument can also be a collecting loop which is connected to the cable core and spreads out automatically when it is pushed out of the tool base.
At least the tool element, such as the forceps fingers, but where appropriate also the tool base or the forceps base, are preferably made of titanium or a titanium alloy in order to achieve artefact imaging of the holding element which is as far as possible true to scale. However, other paramagnetic or diamagnetic metals, such as platinum, gold, silver, copper or aluminium or alloys thereof, are also suitable.
The overall dimensions of the surgical tool and/or of the manual actuation element, where this is made of electrically conducting material, in particular metal, are preferably less than 10 cm, in particular less than 6 cm and preferably less than 3 cm. Electromagnetic resonances under the operating conditions of the tomograph and therefore heating up of the metal parts by the electromagnetic field can be reliably avoided in this manner. Although the cable sheath and/or the cable core is/are preferably made overall of electrically non-conducting or substantially non-conducting material, adhering to the above dimension limits allows the use of segmented electrically conducting components which are electrically insulated from one another at least between the segments. This allows e.g. the use of electrically conducting reinforcing thread segments, such as carbon reinforcing thread segments.
The cable sheath must transmit in a reliable and largely non-elastic manner tensile and compressive forces as well as torsional forces from the manual actuation element to the tool element, such as the forceps tool. Nevertheless, it must be ensured that the actuation cable is adequately flexurally elastic. In a preferred embodiment, these properties are achieved in an optimum manner, in spite of the comparatively small diameter of the cable sheath, if the reinforcing threads of the composite material of the cable sheath are coiled around the central axis thereof. In particular, in this embodiment the composite material of the cable sheath comprises reinforcing threads coiled in opposite directions around the central axis thereof in order to obtain properties which correspond to one another in both torsional rotation directions. The reinforcing threads coiled in opposite directions can be arranged in two separate winding layers lying one on top of the other, in which they are fixed by the plastics matrix. Particularly high tensile and compressive and torsional rigidity is achieved, however, if the reinforcing threads form a woven structure, in particular in the form of a woven tube. A woven structure is also to be understood as meaning a woven-like structure, such as a knitted or braided or stitched structure. It is essential for such a woven structure that reinforcing threads run essentially symmetrically to a generatrix of the cable sheath, so that a torsional strength results which is symmetrical around the central axis in both directions of rotation.
In a preferred embodiment, the cable sheath comprises a multi-layered structure of non-conducting or substantially non-conducting plastics material, in particular having a tubular inner sheath layer optionally comprising several lumina and an outer sheath layer, surrounding the inner sheath layer, made of such a plastics material, the reinforcing threads being arranged between the inner and the outer sheath layer, that is to say forming, for example, a middle layer made of a woven tube. In such a cable sheath, the inner sheath layer and the outer sheath layer can be formed from plastics materials of different hardness and/or flexural elasticity. In particular, the inner sheath layer can be harder or more rigid than the outer sheath layer, which leads to a reduction in the loss of actuation force.
The cable core runs freely displaceably in the cable sheath and accordingly has an external diameter of the order of, for example, 0.5 to 1 mm. Nevertheless, the cable core must also have an adequate tensile and compressive rigidity, so that the length of the cable core changes only insignificantly under load. Under the given dimensional conditions, the reinforcing threads of the cable core preferably run substantially in the longitudinal direction of the cable core. The reinforcing threads of the cable core can be constructed as thread sections which, however, are preferably in each case longer than 3 cm. Preferably, the reinforcing threads of the cable core extend in one piece over the entire length thereof.
The cable core is preferably constructed as more rigid to tensile and compressive stress than the cable sheath. The cable core accordingly should have a high modulus of elasticity of at least 2,000 MPa, measured in accordance with ASTM D 638/DIN EN ISO 527, and/or a ball indentation hardness of at least 120 MPa (DIN EN ISO 2039-1). The yield stress, measured in the tensile test according to DIN EN ISO 527, should be at least 60 MPa. The cable core should withstand forces of at least 100 N, but more preferably at least 200 N, without or without noticeable plastic deformation.
Suitable plastics for the plastics matrix of the cable core are epoxy resin and/or a plastic from the group of polyamides, in particular PA 6 or PA66, and/or the group of polyimides (PI) and/or polyetherimides (PEI), and/or the group of polyamide-imides (PAI) and/or the group of polyaryletherketones (PAEK) and/or of polyetheretherketones (PEEK) and/or polyetherketones (PEK), and/or the group of polyphenylene sulphides (PPS), and/or the group of polysulfones (PSU) in particular polyarylsulfones and/or of polyphenylsulfones (PPSU) and/or of polyethersulfones (PES), and/or the group of liquid crystal polymers (LCP). The plastics matrix should comprise at least one of these plastics.
The plastics matrix of the composite material of the cable sheath preferably comprises plastics which are less hard and/or more flexurally elastic than the plastics matrix of the cable core. Suitable plastics are, for example, polyamide (PA), polyethylene (PE), polypropylene (PP), polyurethane (PU), polytetrafluoroethylene (PTFE), perfluoroethylene/propylene plastic (FEP), perfluoroalkoxyalkane (PFA) or polyether block amide (PEBAX). The plastics matrix of the cable sheath should comprise at least one of these plastics. In a multi-layered construction of the cable sheath, the inner sheath layer is preferably made of PA or PPSU, while the outer sheath layer is made of a plastics material which, in contrast, is less hard or more flexible, for example PEBAX. The inner sheath layer is preferably doped with a lubricant, in particular BaSO4, in order to improve the slip properties of the cable sheath. Doping with BaSO4 moreover improves the visibility of the actuation cable in the magnetic resonance tomograph without noticeable artefact formation.
The reinforcing threads of the composite material of the cable sheath and/or of the cable core are preferably aramid fibres or glass fibres or polyester fibres or ceramic fibres or fibres of liquid crystal polymer. In each case a plurality of such fibres can be combined or twisted into threads for easier handling. Reinforcing threads of glass fibres improve the tensile and shear values of the cable core to a particularly high degree. In order also to improve the breaking strength, the cable core is preferably reinforced with a mixture of reinforcing threads of different material, in particular of glass fibres and aramid fibres, embedded in the plastics matrix. In this connection, PEEK has proved to be particularly suitable as the material of the plastics matrix.
Where the materials of the surgical or forceps tool and of the actuation cable are electrically non-conducting, they can form artefacts which are not adequately detectable in magnetic resonance imaging, depending on the susceptibility (magnetisability) thereof. In order to facilitate evaluation of the image, the cable sheath and/or the cable core can carry or comprise at least regions of marking material, for example metal, in particular in the form of particles of this material, which has a susceptibility which differs from water. The marking can be in the form of rings, which can optionally also be made completely of metal and can also be used at predetermined intervals, in the nature of a measuring scale, for length measurement under MRT conditions. The measuring scale can be constructed, for example, as a cm scale and can optionally be provided at intervals on the actuation cable with an inscription. The zero point of the measuring scale is expediently at the distal end, i.e. the tip of the tool element. Such a marking is of advantage in particular in the case of non-metallic tool elements, for example forceps fingers, for example made of ceramic or plastic, but also in the case of the electrically non-conducting actuation cable, in particular the cable sheath thereof. In the case of tool elements constructed as a gripping device, it may be of advantage for only some of the forceps fingers which can move relative to one another be coated or doped with marking material, in order to generate different MRT artefacts of the individual forceps fingers in this manner. The open or closed state of the forceps tool can be rendered visible in this manner.
In order to be able to insert the surgical instrument more easily into the body of the patient, it is advantageous for the actuation cable to be more flexible in configuration in a limited region close to the surgical tool than in its remaining length leading to the manual actuation element. In a preferred embodiment in which the reinforcing threads of the cable sheath surround the central axis in the form of a coil, this can be achieved by coiling the reinforcing threads in the more flexible region with a lower pitch than in the region of the cable sheath lying between this region and the manual actuation element. The diameter of the cable core is also expediently chosen to be smaller in the flexible region than in the residual length of the cable core following towards the manual actuation element.
The surgical instrument is expediently inserted into the body of the patient via an MRT-capable catheter. The catheter preferably has a distal end which can be controlled in its degree of bending. The controllable end can, for example, be curved manually before insertion into the body or, however, in the inserted state can be controlled in its curvature from a manual actuation device via a drawing wire guided in the catheter.
In a preferred embodiment, the curvature of a region of the actuation cable adjacent to the surgical tool can be controlled from the manual actuation element, as is known for conventional biopsy forceps from DE 36 41 935 A1. This facilitates the insertion of the surgical instrument into the body of the patient and placement of the surgical tool in a desired position. In the case of a surgical instrument which can be employed under MRT conditions, the curvature of the end region of the actuation cable adjacent to the surgical tool can also be controlled in a constructionally simple manner if a further, flexible cable core of electrically non-conducting or substantially non-conducting material is guided displaceably in the cable sheath, the end of which cable core adjacent to the tool base is fixed eccentrically to a central axis of the cable sheath on the tool base or close to the tool base on the cable sheath. The further cable core is also displaceable by means of a control unit of the manual actuation element. If the further cable core is pulled out of the cable sheath, because of its eccentric connection of its end adjacent to the surgical tool, it curves the end region of the cable sheath. In the position pulled out of the cable sheath, the further cable core can expediently be stopped at the manual actuation element.
The embodiment explained above of a flexible actuation cable having an end region which can be controlled in its curvature can be employed even if the actuation cable has a comparatively small diameter. In order to limit the region of controllable curvature in a predetermined manner and to ensure a comparatively large angle of curvature in this region, in a preferred embodiment, for formation of the region of controllable curvature, the cable sheath has non-uniform flexurally elastic properties transversely to the central axis in a section of its length adjacent to the tool base viewed in the circumferential direction, and is more flexible towards the eccentrically fixed end of the further cable core than outside this region. The flexible properties of the curvature region moreover lessen the transverse forces exerted by the further cable core on the cable sheath.
The more flexible properties of the curvature region can be realised in various ways. On the one hand, the plastics matrix of the curvature region can be made of a more elastic or more flexible plastics material than outside the curvature region. However, the bending properties can also be influenced by suitable choice of the reinforcement of the cable sheath. For example, as already explained above, the pitch of the reinforcing threads coiled around the central axis can be smaller in the curvature region than outside the curvature region. In addition or alternatively, on the side of the central axis facing away radially from the eccentrically fixed end of the further cable core, in the region of controllable curvature, the cable sheath can be provided with a reinforcement extended in the direction of the central axis. In this manner, on its side exposed to tension during curving, the cable sheath is stiffened by the additional, longitudinally running reinforcement. In addition or alternatively, however, in the region of controllable curvature on the side of the central axis lying radially to the eccentrically fixed end of the further cable core, the cable sheath can also be made of a softer material, at least in a part-region, than at least in a part-region on the diametrally opposite side. Curving of the cable core is also facilitated by this measure.
The curvature properties of the cable sheath can additionally or alternatively also be influenced, however, by its design. In a preferred embodiment, in the region of controllable curvature the cable sheath has, on the side lying towards the eccentric end of the further cable core with respect to the central axis, a plurality of recesses arranged at intervals from one another in the direction of the central axis. The recesses are expediently grooves or cavities extending in the circumferential direction over a part-length of the circumference. The recesses are preferably provided on the outer circumference of the cable sheath. In the region of controllable curvature, the cable sheath is expediently sheathed with a flexible protective tube, which smoothes the surface of the cable sheath. Where the plastics matrix of the cable sheath, as explained above, is constructed in several layers, it goes without saying that the recesses or cavities can also be provided on the inner layer of the plastics matrix.
The cable core connected to the surgical tool can have a smaller diameter in the controllable curvature region than outside this region, in order to be able to curve the actuation cable overall more easily in this region. The further cable core can accordingly also have a smaller diameter in the controllable curvature region than outside the region. In the transition region between the smaller and the larger diameter, the cable cores expediently taper conically, in order to reduce the risk of breaking in the transition region.
The manual actuation element may also be exposed to the strong magnetic field of the tomograph, which may possibly also lead to a heating up of the manual actuation element, especially if it comprises metal parts. In order to prevent excessive heating up of the manual actuation element, the manual actuation element is expediently made of a non-magnetic, electrically conducting material, in particular plastic, at least in its manually accessible outer surfaces.
Embodiments of the invention are explained in more detail in the following with the aid of a drawing.
The surgical biopsy forceps shown in
For MRT-guided biopsies, in particular myocardial biopsies, the dimensions of the forceps tool 5 are comparatively small. For example, the forceps tool 5 conventionally has a diameter of less than 3 mm at a length of between 6 and 15 mm. The actuation cable 3 in its turn is comparatively thin having an external diameter of from, for example, 1.0 to 3 mm, but comparatively long, for example, between 50 cm to 1.4 m. In spite of these dimensional conditions, both the cable sheath 13 and the cable core 15 must have tensile and compressive rigidity in order to be able to transmit the forces required for opening and closing the forceps tool 5 without a noticeable, load-related change in length. The actuation cable 3 and in particular the cable sheath 13 thereof must moreover be substantially torsionally rigid in order to be able to rotate the forceps tool 5 in a defined manner around the axis of the actuation cable 3. In spite of these rigidity requirements, the actuation cable 3 must be adequately flexible.
In conventional biopsy forceps, the cable sheath is constructed as a metallic coiled spring, of which the windings adjacent to one another can transmit adequately high tensile and compressive forces in a torsionally rigid manner. The cable core is usually made of a metal wire of solid cross-section. In a magnetic resonance tomograph, the forceps tool and the actuation cable of conventional biopsy forceps generate image artefacts which are not true to scale and make evaluation of the image difficult. Furthermore, the metal parts of the actuation cable heat up in the electromagnetic field of the tomograph. Where the material of the forceps tool and of the actuation cable has ferromagnetic properties, these components are deflected in an undesirable manner in the magnetic field of the tomograph.
In order to avoid the disadvantages explained above, both the cable sheath 13 and the cable core 15 are produced from an electrically substantially non-conducting, flexible composite material, in which in each case a plurality of reinforcing threads 37 running along the actuation cable 3 are embedded in a plastics matrix. In the composite material of the cable sheath 13, the reinforcing threads 37 run, as shown in
As shown in
The cable core 15 runs in the cable sheath 13 with radial play 45. The play 45 should, on the one hand, be a small as possible in order to keep path losses between the actuation path of the manual actuation element 1 and the actuation path of the forceps tool 5 as low as possible during actuation of the manual actuation element 1. On the other hand, diameter tolerances which the play must compensate may result during production of the cable core 15 and the cable sheath 13. Based on half the diameter difference shown in
Preferably, the reinforcing threads 37 extend integrally substantially over the entire length of the actuation cable 3. It goes without saying, however, that the reinforcing threads can also extend merely over a part-region of the total length of the actuation cable, since they are firmly connected to one another via the plastics matrix. The reinforcing threads 37 can be constructed, for example, as aramid fibres or glass fibres or polyester fibres or ceramic fibres or fibres of liquid crystal polymer. Glass fibres have proved to have a particular tensile and shear strength especially for the cable core 15. In order to reduce the risk of breaking of the glass fibres, the glass fibres are preferably embedded in the plastics matrix as a mixture with aramid fibres. Electrically conducting fibres, for example carbon fibres, can optionally also be used to a certain extent if these fibres are segmented and the segments are electrically insulated from one another and have a length of less than 10 cm, in particular less than 6 cm and preferably less than 3 cm.
It has proved favourable for the reinforcing threads 37 in each case to be made of a very large number of reinforcing fibres, the fibre diameter of which in each case is of the order of 1/100 mm or thinner. A very large number of such fibres can be bundled or twisted into a thread, the diameter of which is between about 0.1 to 0.15 mm. The reinforcing of the cable core 15 is made of a plurality of such reinforcing threads, which can be embedded in the plastics matrix by coextrusion. The reinforcing threads 37 of the cable sheath 13 are expediently applied to the inner sheath layer 41, for example by means of a tubular braiding machine, before the outer sheath layer 43 is applied to this composite, for example likewise by coextrusion.
The material of the plastics matrix of the cable sheath 13 can be polyamide (PA), polyethylene (PE), polypropylene (PP), polyurethane (PU), polytetrafluoroethylene (PTFE), perfluoroethylene-propylene plastic (FEP), perfluoroalkoxyalkane (PFA) or a polyether block amide (PEBAX). The plastics matrix should comprise at least one of these plastics materials as the highest content. The inner sheath layer 41 expediently is made of PA or PPSU. For the outer sheath layer 43, PEBAX has proved to be suitable. In order to achieve a firm connection between the sheath layers 41, 43, the materials of the plastics matrix are preferably thermoplastics. To improve the slip properties and to improve visibility in the magnetic resonance tomograph without substantial formation of artefacts, the plastics matrix is expediently doped with BaSO4 or another lubricant.
The material of the plastics matrix of the cable core 15 is preferably epoxy resin or a plastic from the group of polyamides, in particular PA 6 or PA66, and/or the group of polyimides (PI) and/or polyetherimides (PEI), and/or the group of polyamide-imides (PAI), and/or the group of polyaryletherketones (PAEK) and/or of polyetheretherketones (PEEK) and/or of polyetherketones (PEK), and/or the group of polyphenylene sulphides (PPS), and/or the group of polysulfones (PSU) in particular polyarylsulfones and/or of polyphenylsulfones (PPSU) and/or of polyethersulfones (PES), and/or the group of liquid crystal polymers (LCP). The plastics matrix should comprise at least one of these plastics materials as the highest content. PEEK and PPSU have proved to be particularly suitable.
The cable core should have a ball indentation hardness of more than 120 MPa (measured in accordance with DIN EN ISO 2039-1) and an E modulus of at least 2,000 MPa (measured in accordance with ASTM D 638, DIN EN ISO 527). The yield stress of the material of the plastics matrix of the cable core 15 should be at least 60 MPa (measured in accordance with DIN EN ISO 527). Plastics materials which meet these requirements are e.g. PEEK and PPSU. The ball indentation hardness of the plastics materials of the inner sheath layer 41 and of the outer sheath layer 43, like the E modulus of these materials and the yield stress thereof, can be lower. For the material of the reinforcing threads but also of the plastics matrix, it is essential that they should not lose their strength under the operating conditions of the magnetic resonance tomograph. The material of the reinforcing threads and of the plastics matrix must therefore have temperature-constant or substantially temperature-constant expansion properties at least up to 60° C., but preferably up to 130° C., that is to say have no or no noticeable losses in strength. The cable core should be able to absorb forces of at least 100 N, more preferably at least 200 N, without plastic deformation.
It goes without saying that the material of the cable core and of the cable sheath, like that of the surgical tool and of the manual actuation element, must also be able to withstand relatively high temperatures in order to be able to sterilise or autoclave the instrument.
At least the forceps fingers 29 of the forceps tool 5 are preferably made of titanium or a titanium alloy in order to achieve artefacts which are as image-true as possible. However, other paramagnetic or diamagnetic materials, such as platinum, gold, silver, copper or aluminium or alloys of these metals, are also suitable. Since the forceps tool 5 is made of metal, it is visible in the tomograph, so that the biopsy forceps can be put in place. Because of the small dimensions of the forceps tool 5, the risk of heating up in the electromagnetic field of the tomograph is low. Individual components of the forceps tool 5, such as the axis 27, can therefore also be produced from less expensive materials, such as non-rusting steel having non-magnetic properties, if artefacts generated in the image by such components can be tolerated.
While the components of the forceps tool 5 are visible in the tomograph, the actuation cable 3 does not image detectably or images such that it is only poorly detectable. It has therefore proved favourable for the actuation cable 3, in particular the cable sheath 13 thereof, to be doped or coated with metallic particles at least in regions, or for metallic marking rings, as indicated at 47, to be applied as visible marks at predetermined intervals on the actuation cable 13. The marking rings 47 can be made of solid material or in turn of regions doped with metal. Such visible marks can also be used as scale marks.
The two forceps fingers 29 can be constructed such that they generate different artefacts in the tomograph. The open or closed state of the forceps tool 5 can also be shown in this manner. The two forceps fingers 29 can be made of different material or be doped or coated differently with marking material, as is indicated at 49 in
However, in order to rule out heating up of metallic or electrically conducting components in the electromagnetic field of the tomograph, the dimensions of these components should be shorter than 10 cm, in particular shorter than 6 cm and preferably shorter than 3 cm. This also applies to any metallic components of the manual actuation element 1, such as the extension piece 17, which is conventionally constructed as a metal rod, or the pressure spring 35, especially if the biopsy forceps are used in an open magnetic resonance tomograph in which the manual actuation element 1 may also be exposed to the magnetic field. The manual actuation element 1, at least in its manually accessible outer surfaces, such as the thumb ring 9, the guide shaft 7 and the index finger-middle finger sliding grip 19, is expediently made of a non-magnetic, electrically non-conducting material, in particular plastic. If metal parts, such as the extension piece 17 or the pressure spring 35, are provided, the dimensions are chosen to be smaller than 10 cm and preferably smaller than 6 cm.
Variants of the surgical instrument explained above with the aid of
The forceps fingers 29a, 29b shown in
The coupling hook 57f and optionally the tool base 21f, like the coupling head 61f, are made of non-ferromagnetic material, for example titanium or platinum, gold, silver, copper, aluminium or an alloy thereof or of electrically non-conducting plastic. The actuation cable 3f and the manual actuation element correspond to components 3 and 1 as have been explained above with the aid of
The actuation cable 3 of the biopsy forceps 1 explained with the aid of
In contrast to the biopsy forceps of
A further cable core 69 is arranged in the lumen 67, the end 71 of which cable core 69 adjacent to the forceps tool 5g is fixed eccentrically to the central axis 39g on the forceps base 21g. The cable core 69 is otherwise freely displaceable in the lumen 67 and can be loaded with tension by the manual actuation element via a handling unit (not shown in more detail). Because of the eccentricity with which the end 71 of the cable core 69 is fixed on the tool base 21g, the actuation cable 3g curves in a region immediately adjacent to the forceps tool 5g. The angle of curvature is determined by the displacement path around which the cable core 69 is moved on the manual actuation element relative to the cable sheath 13g. It goes without saying that the end 71 of the cable core 69 close to the forceps base 21g can also be fixed directly, but eccentrically to the central axis 39g, on the cable sheath 13g.
The handling unit connected to the cable core 69 for adjusting the curvature can have the form of a finger grip, as is shown at 19 in
The cable sheath 13g, like the cable cores 15g and 69, are constructed according to the explanations for the cable sheath 13 and the cable core 15 of
It goes without saying that the forceps tool 5g can also be replaced by other surgical tools, as explained, for example, in
Inhomogeneities in the cable sheath 13g can mean that the actuation cable 3g not only curves in the curvature region but also winds around the central axis 39g. Furthermore, it is desirable for the tensile force to be exerted on the further cable core 69 to adjust the curvature to be comparatively low, since the further cable core 69 loads the cable sheath 13g radially during curving of the actuation cable and may damage the inner wall of the lumen 67.
The forceps tool 5h and the actuation cable 3h correspond in construction and mode of action to the embodiment according to
The cable sheath 13h comprises, as has already been explained with the aid of
The recesses 75 are formed in the outer surface of the outer sheath layer 43h and, as shown at 77 in
The cable core 15h also contributes towards stiffening of the curvature region of the actuation cable 13h. In order to reduce the flexural rigidity of the curvature region, as indicated at 15′h in
The reinforcements of the cable jackets explained above which are coiled in opposite directions can have a uniform pitch over the entire length of the actuation cable. As in the embodiment indicated in diagram form in
A further variant which likewise can be employed in the embodiments of
| Number | Date | Country | Kind |
|---|---|---|---|
| 102012201081.5 | Jan 2012 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2013/051210 | 1/23/2013 | WO | 00 |
