Patent Application
20230366759
The present invention relates to a catheter device according to the preamble of claim 1.
Such a catheter device comprises a measuring device for measuring a force effect on the catheter device. The measuring device comprises an elastically deformable transducer body with a plurality of transducer portions and a sensor device arranged on the transducer body. The transducer portions form at least one pair of adjacent transducer portions which are connected to each other via a connecting portion and are movable relative to each other with deformation of the connecting portion. The sensor device is designed to measure a force effect between the transducer portions of the at least one pair of adjacent transducer portions.
Such a catheter device may be designed as an ablation catheter, for example. An ablation catheter may be used to treat cardiac arrhythmias by selectively eliminating heart tissue, for example by heating or electrophoresis, in order to locally suppress the generation or conduction of electrical impulses. An electrode may be brought into contact with heart tissue for this purpose, for example in order to heat tissue locally by introducing a high-frequency current during high-frequency ablation and thus destroy it, or in order to induce electrophoresis in the tissue cells by means of pulsed electrical fields and thus destroy them.
In the case of such a catheter device, a force shall be reliably ascertained in order to determine whether the catheter device is in contact with the tissue to be treated and the force with which the catheter device is acting on the tissue.
In a catheter device known from U.S. Publication No. 2014/0081264 A1, an optical fibre is arranged on a transducer body, which has a plurality of sensor devices each with an optical grating. The sensor devices are intended to measure a force effect between transducer portions of the transducer body, the transducer body being designed in such a way that each sensor device may measure a force effect along a defined spatial direction.
In a catheter device known from U.S. Publication No. 2006/0200049 A1, different optical fibres are arranged on a body and each have a sensor device. A force effect may be measured via the sensor devices, which may, for example, have optical gratings in the form of Fiber Bragg Gratings.
International Publication No. WO 2013/177577 A2 describes a catheter device which has an optical fibre enclosed in a cylindrical sleeve. A temperature-compensated Fiber Bragg Grating interferometer is optically connected to the optical fibre. When a pressure load is applied, a force value may be determined and evaluated by means of a signal generated by the interferometer.
The present disclosure is directed toward overcoming one or more of the above-mentioned problems, though not necessarily limited to embodiments that do.
An object of the present invention is to provide a catheter device which enables a reliable and accurate measurement of a force effect on the catheter device.
At least this object is achieved by a subject with the features of claim 1.
Accordingly, the transducer body is made of a glass material.
Within the frame of this application glass material is to be understood as a metastable basically amorphous structure with low crystallinity comprising silicon dioxide. The amount of crystallinity is below 20%, in particular below 10%, in particular below 5%, in particular below 2%, in particular below 1%.
For example, the transducer body may be made of a quartz glass material, especially a high-purity quartz glass material.
The transducer body may also be made of a glass ceramic material or a sintered glass ceramic material made of silicon dioxide.
The transducer body may, for example, be manufactured using 3D printing. It is advantageous to use an additional sintering process after 3D printing to form the transducer body.
In the measuring device of the catheter device, a force effect is measured between transducer portions, which are connected to each other in pairs via a connecting portion and may be moved relative to each other in a predetermined way via the connecting portion. In particular, the transducer portions may, for example, be swivelled and/or axially adjusted in relation to each other so that a force effect along a predefined spatial direction may be determined on the basis of a movement of two transducer portions relative to each other.
The force effect is measured here via a sensor device, which is designed to indicate a deformation between adjacent transducer portions on the basis of a measurement signal, so that, by evaluating the measurement signal, a force value may be determined, which indicates a force acting on the catheter device. The sensor device may be designed as an optical sensor device. The sensor device may, for example, have an optical fibre, in particular in the form of a glass fibre, on which at least one optical device for measuring a force effect between the transducer portions of the at least one pair of adjacent transducer portions is formed. The optical device for measuring a force effect between the transducer portions of the at least one pair of adjacent transducer portions may be formed as an optical grating.
Such an optical grating may, for example, be formed by a Fiber Bragg Grating (FBG), a Long Period Grating (LPG) or a Fabri-Perot resonator, with at least one optical grating being advantageously assigned to each pair of transducer portions, so that measured values may be recorded between each pair of transducer portions in order to evaluate force values on the basis of a deflection between two transducer portions in order to determine a force acting on the catheter device.
In one embodiment, the optical fibre is extended along the longitudinal axis on the transducer body. The optical fibre is firmly connected here to the transducer body at least at defined fastening regions, in particular in the region of the transducer portions, so that a deflection of transducer portions relative to each other leads to a change in length, in particular elongation or compression, at the optical fibre and may thus be measured via the optical gratings of the optical fibre.
In general, a change in length in the form of an elongation or compression at the optical fibre leads to a change in the optical properties of the optical gratings, in particular a change in the grating spacing of the optical gratings. From a change in length at the optical fibre, it may be concluded that there is a force effect at the transducer body and thus at the catheter device, and the force effect may be determined, for example, on the basis of a calibration, within the framework of which, before the actual operation, a deflection at the transducer body and an associated deformation, in particular elongation or compression at the optical fibre, is related to a force effect at the transducer body.
The fact that the transducer body is made of a glass material, especially a quartz glass, a glass ceramic or a sintered glass ceramic, results in advantageous elastic properties at the transducer body. This makes it possible, by means of suitable calibration before the catheter device is put into operation, to carry out measurements of forces acting on the catheter device during operation in a manner that is stable in the long term, since a deflection of transducer portions of the transducer body in relation to each other when force is applied, for example distally on the catheter device, results in the generation of measured values which may be evaluated for determining the force.
If, in addition, the optical fibre of the sensor device is designed as a glass fibre, there is the possibility of an advantageous connection of the optical fibre with the transducer body made of glass material. For example, the glass fibre may be connected to transducer portions of the transducer body by bonding, for example using glass frit, by glass soldering or by welding. Alternatively, for example, a form fit may be produced, for example by thermal clamping between the optical fibre and the transducer portions of the transducer body, in order to connect the optical fibre to the transducer body. Again, as an alternative, the optical fibre, when producing the transducer body, may be connected to the transducer body by sintering in a sintering process. Another possibility to connect the optical fibre to the transducer body is to melt small, prepared glass bridges coloured by laser pulses, the glass bridges turning into melt drops and enclosing the glass fibre, cooling down rapidly at the same time and thus creating the fixation. Another possibility to connect the optical fibre to the transducer body is to coat the glass fibre with a suitable metal thin film. The transducer body may be provided with a further suitable layer (or a layered composite), so that the optical fibre may be connected to the transducer body by a solder, for example a eutectic gold-tin (AuSn) solder. This joining technique is also called eutectic soldering. This type of connection, which may be carried out in particular without the use of adhesive, may prevent signal artefacts that could be caused by elastoplastic or tribological effects or degradation of the connection over the service life of the catheter device.
As the transducer body is made of glass material, the measuring device is MR-compatible without further measures and may also be combined with magnetic field sensors, for example for the purpose of catheter navigation.
In one embodiment, the catheter device has a pigtail connected to the transducer body and separate from the optical fibre, which pigtail is optically coupled to the optical fibre at a connection point on the transducer body. The fact that the pigtail is designed separately from the optical fibre, i.e., not in one piece with the optical fibre, and is connected to the optical fibre by optical coupling, prevents mechanical influences on the pigtail, for example tribological influences, from influencing sensor signals. In particular, any movement or force effect on the pigtail is not directly transmitted to the optical fibre of the sensor device and thus cannot lead to artefacts in sensor signals. In addition, the use of different fibres for the optical fibre of the sensor device on the one hand and for the pigtail as the feed line for the optical fibre of the sensor device on the other hand makes it possible to adapt the fibres to the particular requirements, for example by using fibres with different diameters. The pigtail should be sufficiently stable to prevent damage, especially breakage during operation, so that the pigtail should have a larger diameter, for example. By contrast, the optical fibre of the sensor device should be sufficiently elastically extensible to provide a favourable sensitivity for force measurement. The optical fibre of the sensor device may therefore have, for example, a smaller (outer) diameter than the pigtail. The use of different fibres for the optical fibre of the sensor device on the one hand and for the pigtail as the supply line for the optical fibre of the sensor device on the other hand also enables the sensor device to be produced in a pre-assembled and manageable form and thus to be transported more safely (for example to avoid a breakage of the optical fibre) to another location for final assembly in a catheter.
In one embodiment, the connection point on the transducer body is designed in such a way that it aligns the optical fibre and the pigtail centrally in relation to each other. This maximises the transmitted optical sensor signal.
In a further embodiment, the connection point where the optical fibre is optically coupled to the pigtail is provided with an adhesive to adjust the refractive indices of the optical fibre and the pigtail.
In one embodiment, the transducer portions of the transducer body are arranged in a line along a longitudinal axis. The longitudinal axis of the transducer body corresponds advantageously to the longitudinal axis of the catheter device, so that the transducer portions are connected longitudinally to each other on the catheter device, with adjacent transducer portions, in pairs, each being connected to each other via a connecting portion that may be deformed in a defined manner.
By means of the connecting portions, the transducer portions may be moved relative to each other in different ways so that a force effect may be measured via the sensor device assigned to the pairs of transducer portions. The transducer body splits a force applied to the catheter device into vector components, which may be measured by different optical gratings of the optical fibre of the sensor device.
In one embodiment, the transducer body has, for example, at least one pair of adjacent transducer portions which are connected to each other by a connecting portion which is movable around a defined spatial direction extending transversely to the longitudinal axis. The transducer portions are thus, by specifying the connecting portion, movable relative to each other about the spatial direction defined by the connecting portion, so that a force effect about the particular spatial direction may be detected on the basis of a force measurement using an optical grating assigned to the particular pair of transducer portions.
The transducer portions of a pair of adjacent transducer portions are fundamentally only movable around the defined spatial direction, so that a deflection at the transducer portions transverse to the longitudinal axis and transverse to the defined spatial direction may be measured on the basis of the sensor device.
In this case, the connecting portion may, for example, be designed as a web extending between the assigned adjacent transducer portions, which web may be moved flexibly, substantially exclusively around the assigned, defined spatial direction.
In an advantageous embodiment, there may be at least two pairs of adjacent transducer portions, each connected to the other by a connecting portion, the connecting portions being movable about different defined spatial directions extending transversely to the longitudinal axis and thus defining a movability of the transducer portions about different spatial directions. The different spatial directions may, for example, be directed perpendicularly to each other and thus define a plane of movement perpendicular to the longitudinal axis of the transducer body, so that a force effect in the plane of movement extending perpendicularly to the longitudinal axis may be determined via the optical gratings assigned to the pairs of transducer portions.
For example, two pairs of transducer portions may be used to measure a radial force effect on the catheter device along radially directed spatial directions offset by 90° to each other. By contrast, a further, third pair of transducer portions may be used to receive and measure an axial force along the longitudinal axis of the catheter device, so that a force effect may be measured in three-dimensional space using the three pairs of transducer portions.
The third pair of transducer portions is also connected to each other via an associated connecting portion, the connecting portion being shaped in such a way that, when axial force is applied to the catheter device, the transducer portions are deflected relative to each other and thus an axial force is preferably received and measured at this pair of transducer portions.
In one embodiment, the transducer body has a cooling channel for conducting a coolant. The cooling channel is, for example, extended longitudinally along the longitudinal axis through the transducer body, and the cooling channel may be designed concentrically with a cylinder axis of the transducer body, which is cylindrical in its basic form, or also may be designed eccentrically to the cylinder axis. In particular, in order to form recesses in the transducer body to separate the transducer portions from each other, an eccentric arrangement of the cooling channel in the transducer body may be advantageous in order to allow one or more recesses to extend beyond the cylinder axis.
During operation a coolant may be passed through the cooling channel. The coolant, for example in the form of a temperature-controlled physiological saline solution, may also be used for flushing and may be conducted through the transducer body towards the distal end of the catheter device, in particular to a functional electrode of the catheter device arranged at the distal end, in order to exit the catheter device at the functional electrode.
Due to the fact that the transducer body is temperature-controlled by the coolant during operation of the catheter device, temperature-induced artefacts in the force measurement may be reduced. By keeping the transducer body at a substantially constant temperature when the catheter device is in use, a temperature-induced change in length at the optical fibre of the measuring device may be avoided, and therefore it may be assumed that measurement signals obtained using the optical gratings are at least approximately not influenced by temperature effects. This makes it possible to dispense with additional temperature compensation for the force measurement.
Because the transducer body is made of a glass material, in particular quartz glass, biocompatibility is achieved, although the coolant passed through the transducer body may also be used for flushing in the region of the functional electrode, and the transducer body may therefore be in indirect contact with the patient's tissue and blood circulation.
The cooling channel may be straight and axially extended through the transducer body. It is also conceivable, however, that the cooling channel is, for example, meander-shaped and/or designed with a lumen of varying internal diameter in the transducer body. In this way, a convective heat exchange of the coolant with the transducer body may be improved, with a laminar flow within the cooling channel, which may have a heat-insulating effect, being reduced.
In one embodiment, the catheter device has a substantially rigid protective sleeve, in which the transducer body is arranged and to which the transducer body is connected. The protective sleeve encloses the transducer body towards the outside and thus provides a sleeve for the transducer body. The protective sleeve may, for example, have a cylindrical shape which accommodates the transducer body inside. The protective sleeve may, for example, be made of a metal material or a fibre-reinforced plastics material, for example a glass- or carbon-fibre-reinforced plastics material, or a non-fibre-reinforced hard plastics material, and is substantially rigid, i.e., it is not elastically deformable under forces acting during operation.
The transducer body is preferably firmly connected to the protective sleeve at one end, but otherwise extends freely inside the protective sleeve. For example, there may be a (air) gap between the transducer body and the protective sleeve where the transducer body is not connected to the protective sleeve, so that the transducer body is arranged and received with play in the protective sleeve and may thus move in the protective sleeve under elastic deformation.
Via the (air) gap, the transducer body is preferably thermally insulated from the protective sleeve so that temperature control of the transducer body is supported by a coolant passing through the transducer body.
For example, the transducer body may be connected to the protective sleeve at a first end and may be movable relative to the protective sleeve with a second end remote from the first end, so that the transducer body may be deflected with the second end in the protective sleeve, in particular radially. At the first end, the transducer body may be fixed to the protective sleeve in the manner of a cantilever beam, for example, so that the transducer body is fixed at the first end in relation to the protective sleeve in terms of position and torque. A deflection of the second end is thus effected with elastic deformation of the transducer body, in particular with deflection of the transducer portions relative to each other.
In one embodiment, the catheter device has a functional electrode which—when the catheter device is designed as an ablation catheter—serves, for example, to feed electrical energy into the tissue to be treated and is positioned distally on the catheter device for this purpose. The functional electrode is connected, for example, to the second end of the transducer body, so that a force acting on the functional electrode as a result of contact of the catheter device with surrounding tissue leads to elastic deformation and deflection at the transducer body and thus a force acting on the functional electrode may be measured on the basis of the deformation of the transducer body. Typically, the force effects to be measured are in the range of 0.05 N to 0.5 N, preferably in the range of 0.2 N to 0.4 N. If the catheter device is inserted into the body or removed from the body via the vascular system, a force effect exceeding 0.5 N may occur in the region of the force measuring device and in particular in the region of the transducer body. Force effects in the region of the transducer body of up to 20 N are not unusual when inserting and removing the catheter device, especially if the insertion and removal is carried out through an insertion catheter. In this case it is helpful if the force measuring device, especially the transducer body, is protected by a protective sleeve, i.e., the deformation of the transducer body is limited by the protective sleeve. Typical values for the force effect with which this protective effect should take effect are in the range of 0.5 N to 2 N.
The functional electrode may, for example, form a distal termination of the catheter device and is exposed outwardly during operation of the catheter device. At its distal end, the functional electrode may in particular have a hemispherical shape.
In one embodiment, the catheter device has one or more electrode poles, which serve, for example, to sense electrical signals from tissue and are arranged distally on the catheter device for this purpose. These electrode poles may be designed as ring electrodes, which may be used for diagnostic mapping, for example. The ring electrodes are preferably arranged on the protective sleeve.
In one embodiment, the catheter device has an elastically deformable sealing element to seal a transition between the protective sleeve and the second end of the transducer body. The sealing element is flexibly deformable and is designed to seal the transition between the protective sleeve and the transducer body, even in the event of a deflection at the transducer body, in such a way that no liquid may penetrate the protective sleeve.
The sealing element may, for example, be made of an elastomeric plastic and is flexibly deformable.
In one embodiment, the protective sleeve forms a stop to limit elastic deformation of the transducer body. The stop may be formed especially in the region of the second end of the transducer body, so that a radial deflection of the transducer body may be limited and an overstressing of the transducer body due to an overload and a resulting deformation of the transducer body may be avoided. The stop may, for example, be formed by a circumferential edge at the distal end of the protective sleeve, so that the stop limits deflection of the transducer body in all radial directions.
In one embodiment, the catheter device has an evaluation device which is designed to evaluate an optical signal to determine a force effect on the transducer body. The optical signal is obtained as a response signal to a fed-in optical signal and may be present in particular as a reflection signal which has been reflected at the optical gratings of the sensor device. The optical signal may be evaluated in order to determine a force effect on the transducer body on the basis of the optical signal, in particular on the basis of a change in the optical signal compared to a reference signal in a defined, unloaded initial state of the transducer body.
The optical gratings may be arranged on a single optical fibre. An evaluation may be carried out here using a single optical signal, in particular one fed-in in broadband, with the optical gratings differing in their optical properties and reflecting in particular in the range of different wavelengths. Optical signals obtained from different gratings therefore differ in wavelength and may be differentiated and evaluated accordingly in order to evaluate information from the individual gratings and thus determine a force effect in the region of the different gratings and thus along the different force directions assigned to the different gratings.
The evaluation device may, in one embodiment, be designed in particular to evaluate a wavelength change of the optical signal to determine the force effect. When a force is applied to the transducer body and two transducer portions are thus deflected relative to each other, this causes a change in the length of the optical fibre in the region of the optical gratings assigned to the transducer portions, in particular an elongation or compression of the optical fibre and thus a change in the optical properties of the optical gratings of the sensor device. In particular, a grating period of the optical gratings may change, which leads to a change in the received reflection signal and may be evaluated accordingly.
Additional features, aspects, objects, advantages, and possible applications of the present disclosure will become apparent from a study of the exemplary embodiments and examples described below, in combination with the Figures and the appended claims.
The idea underlying the present invention will be explained in more detail below on the basis of the exemplary embodiments shown in the figures, in which:
In the embodiment shown in
The catheter device 1 has a flushed functional electrode 2 in the form of a head electrode, which is designed for performing an ablation and is arranged distally of an elastic sealing element 3. The sealing element 3 is designed to allow elastic movability of the functional electrode 2 relative to a rigid segment 4 of the catheter device 1 and to seal a transition between the functional electrode 2 and the rigid segment 4 in a fluid-tight manner so that liquid from the outside cannot penetrate into the interior of the catheter device 1. The sealing element 3 is firmly connected to the transducer body 15 on the one hand and the rigid segment 4 on the other hand.
The rigid segment 4 serves to surround a transducer body 15 of the measuring device, which is enclosed in rigid segment 4, outwardly and thus protect it against external mechanical stress and thermal influences. A number of ring electrodes 5 are arranged on the rigid segment 4, in the embodiment shown three ring electrodes 5, and may be used for diagnostic mapping, for example.
A controllable segment 6 is connected proximally to the rigid segment 4. The controllable segment 6, which may be deflected by bending a control button 8 on a handle 9 to deflect and control the functional electrode 2, is connected to a catheter shaft 7, which is flexible, but torsion- and compression-resistant and cannot be controlled.
Optical measuring signals generated using the measuring device may be fed via an optical connection 10 in the form of a glass fibre connection on the handle 9, for example, to an external control and evaluation device.
An electrical connection 11 is also located on the handle 9, via which electrical connection ablation energy may be introduced into the functional electrode 2, and electrical signals, which are obtained via the ring electrodes 5, for example, may be diverted. A flushing connection 12 in the form of a Luer lock closure is provided to introduce a cooling and flushing liquid, for example a physiological saline solution, for the functional electrode 2 and the measuring device on the handle 9.
As may be seen in
The elastic sealing element 3 enables the functional electrode 2 to move relative to the rigid segment 4 when it comes into contact with tissue 13 (illustrated by the dashed functional electrode 2′ in with regard to amount and direction.
As may be seen in
The transducer body 15 is manufactured in one embodiment from a glass material, preferably a high-purity quartz glass, in 3D printing with a subsequent sintering process.
In an alternative embodiment, the transducer body 15 is made of a glass material, for example a glass ceramic material or a sintered glass ceramic material.
The glass fibre 16, for example, has a light-conducting core with a diameter between 5 μm and 15 μm, for example 9 μm, and a glass sheath with a diameter between 80 μm and 200 μm, for example 125 μm. The glass sheath may be surrounded by an insulating polyamide coating, so that the glass fibre 16, for example, has a total diameter between 100 μm and 250 μm, for example 155 μm. During operation, light with a short coherence length is coupled into the light-conducting core via the optical connection 10 (see
The fact that the transducer body 15 is made of a glass material, in particular a quartz glass, a glass ceramic or a sintered glass ceramic, results in an advantageous connection with the glass fibre 16. For example, the glass sheath of the glass fibre 16 may be exposed for fixing, for example, and fused, welded, soldered or inseparably connected by (anodic) bonding to the quartz glass, the glass ceramic or the sintered glass ceramic of the transducer body 15. By such a material connection of the transducer body 15 to the glass sheath of the glass fibre 16, hysteresis-effective elastoplastic couplings of a force-induced or thermal deformation of the transducer body 15 into the glass fibre 16 and thus into its optical gratings 17, 18, 19, which could otherwise occur, for example, in adhesive bonding, may be avoided. In addition, by using the glass sheath of the glass fibre 16 with the transducer body 15 consisting of glass or glass ceramic, a long-term and age-resistant connection may be created, without the connection being impaired over the service life of the measuring device.
The transducer body 15 has transducer portions 150-153 lined up along the longitudinal axis L and connected in pairs by connecting portions 154-156 and decoupled from each other by recesses 33-36 in such a way that the transducer portions 150-153 may be deflected elastically in pairs, as will be explained below. The glass fibre 16 is connected to the transducer portions 150-153 of the transducer body 15 in such a way that regions of the glass fibre 16 where the optical gratings 17, 18, 19 are located are freely extended over the recesses 33, 34, 35, 36.
At the proximal end of the transducer body 15, a flushing tube 21 for cooling the tissue 13 during ablation via the functional electrode 2 is glued into a flange 39 formed on the transducer body 15. This has the advantage that a flushing liquid, for example in the form of a physiological saline solution, may be led via the flushing connection 12 through a cooling channel 22 in the transducer body 15, and thus the transducer body 15 and thus also the glass fibre 16 may be cooled and kept at a constant temperature. For example, a material bond between the glass sheath of the glass fibre 16 and the transducer body 15 results in a favourable heat transfer between the glass fibre 16 and the transducer body 15. A temperature-induced drift of the measuring signals S1, S2, S3 due to thermal expansion of the optical gratings 17, 18, 19 may thus be counteracted. It may be that a thermosensor for temperature correction of the measured values is not necessary.
When using the catheter device 1 to perform an ablation, the inner surface of the cooling to channel 22 is in indirect blood contact via the flushing fluid. Because the inner surface of the transducer body 15 which limits the cooling channel 22 is made of a glass material, preferably a high-purity quartz glass, glass ceramic or sintered glass ceramic, corresponding to the material of the transducer body 15, biocompatibility is guaranteed for temporary use in a catheter in the patient.
The arrangement has the further advantage that there are no tribological interactions of the transducer body 15 with a flushing line led to the functional electrode 2, and thus no signal shifts or signal artefacts such as jumps due to tribological interactions may occur.
The transducer body 15 is connected to the protective sleeve 20 proximally at an axial location 25. Distally, the transducer body 15 and the protective sleeve 20 are connected to each other via the elastic sealing element 3. The sealing element 3 is connected interlockingly at an axial location 32 to the protective sleeve 20 and at a location 31 to the transducer body 15.
The connection at the locations 25, 31, 32 is preferably linear along peripheral connecting lines.
The protective sleeve 20 limits the deformation of the transducer body 15 and thus of its optical gratings 17, 18, 19, which is necessary for measuring the contact force. The transducer body 15 is thus prevented from breaking due to overload, for example when the catheter 1 passes through haemostasis valves or curved sluice catheters.
In addition, the outer surface of the protective sleeve 20 has an insulating layer 14 (for example made of LCP) on which the ring electrodes 5 are attached. The axial extent of the rigid segment 4 is determined substantially by the length of the protective sleeve 20.
The sealing element 3 enables the deformation of the transducer body 15 and thus of its optical gratings 17, 18, 19, which is necessary for measuring the contact force, and prevents the penetration of body fluid.
The functional electrode 2 is adhesively fixed at an axial location 30 on the transducer body in such a way that the flushing openings 29 of the functional electrode 2 coincide with the branched flushing channels 28 connected to the flushing channel 22.
The transducer body 15 has a cable channel 24, through which an electrical cable 23 extends to the functional electrode 2. The electrical cable 23 is connected to the functional electrode 2 at a soldering point 26 in the region of a recess 27, which facilitates the mounting of the functional electrode 2 on the transducer body 15 with soldered cable 23, as shown in
For example,
Parallel to the cable channel 24, a channel 61 extends through the transducer body 15, in which a cable for a thermocouple 60 may be laid.
In the embodiment shown, the cooling channel 22 is arranged eccentrically to the centre of the transducer body 15, which has a basic cylindrical shape, in order to create space for the recesses 33, 35, 36.
Between the protective sleeve 20 and the transducer body 15 there is an air gap 62, which serves as thermal insulation outwardly and thus supports the cooling effect on the optical gratings 17, 18, 19 via the cooling channel 22. In addition, the air gap 62 allows a deformation of the transducer body 15 and thus a sectional movement of the transducer body within the rigid segment 4.
Because the recess 33 extends into the transducer body 15 over a comparatively small axial length but a comparatively large radial depth, the connecting portion 154 forms a connection in the manner of a short bar (corresponding to the connecting portion 154 of transducer body 15, shown hatched in
Because the recess 36 is arranged at a right angle to the recess 35, radial forces in particular, which are directed perpendicularly to the radial forces detectable at the optical grating 18, may be received and detected at the optical grating 19.
The glass fibre 16 has, in one embodiment, a non-polymer-based coating (also referred to as a coating), but may be used in other embodiments without such a coating.
In order to make a connection to the transducer body 15, the glass fibre 16 may, for example, have a coating of a gold material which makes it possible to form a connection of the glass fibre 16 with a metal coating of the transducer body 15 by soldering. In another embodiment, a glass fibre 16 may be bonded to the transducer body 16 without coating by means of glass frit/glass solder. In another embodiment, a transducer body 15 may be fitted with a glass fibre 16 as a so-called green body, i.e., as a blank during production in a sintering process, in order to create a connection between the transducer body 15 and the glass fibre 16 during subsequent sintering. The glass fibre 16 may be connected positively to the transducer body in a different embodiment, for example by thermally expanding the transducer body 15 for the glass fibre 16, attaching the glass fibre 16 to the expanded transducer body 15 and thereby creating a tension between the transducer body 15 and the glass fibre 16 when the transducer body 15 cools down. In another embodiment, the fixing is done by laser pulses on coloured glass bridges, which transform into melt droplets and enclose the glass fibre and cool down rapidly. In another embodiment, one or more optical fibres may be created in the transducer body 15, for example by doping, by using glass materials with different refractive indices or by laser treatment, in order to create a measuring device without a separate glass fibre connected to the transducer body 15.
In
While
As may be seen from at the functional electrode 2, the transducer body 15 is elastically deformed within the protective sleeve 20 and moves within the protective sleeve 20 by deflecting the portions of the transducer body 15 separated from each other by the recesses 33, 35, 36 relative to each other.
While the transducer body 15 is firmly connected to the protective sleeve 20 at the axial location 25 in the manner of a rigid beam clamp, the end of the transducer body 15 assigned to the sealing element 3 may move freely within the protective sleeve 20. Accordingly, the transducer body 15 may be axially lengthened or shortened when force is applied to the functional electrode 2 and may bend in any radial direction, with elastic deformation of the sealing element 3. The elastic sealing element 3 ensures that no body fluid may penetrate into the air gap 62 and a transition between the functional electrode 2 and the protective sleeve 20 is thus sealed fluid-tight.
Due to the fixed connection of the glass fibre 16 to the transducer body 15, the three optical gratings 17, 18, 19 are immediately compressed or stretched according to the magnitude and direction of the force on the functional electrode 2 in the event of deformation at the transducer body 15, so that a force effect in terms of magnitude and direction may be detected on the basis of measurement signals obtained via the optical gratings 17, 18, 19.
A force measurement may be possible up to an amount of 8 N, for example.
To counteract overloading of the transducer body 15, deflection and deformation of the transducer body 15 is limited by a distal inner edge 40 of the protective sleeve 20. The inner edge 40 thus acts as a limit stop.
Due to the temperature control of the transducer body 15 and thus of the glass fibre 16 by coolant flow through the cooling channel 22, it may be assumed that a mechanical expansion ε1, ε2, ε3 of the optical gratings 17, 18, 19 due to force-induced deformation at the transducer body 15 alone is the cause of a displacement δλ1, δλ2, δλ3 of a reflected wavelength λB1, λB2, λB3 at the optical gratings 17, 18, 19 acting as band stops.
For measurement purposes, a wavelength signal is fed into the optical fibre 16, which is reflected at the optical gratings 17, 18, 19. If the signal is stretched or compressed at one of the optical gratings 17, 18, 19, a shift of the wavelength in the associated reflected signal occurs. Each optical grating 17, 18, 19 acts as a narrow-band bandstop with an associated centre wavelength, with the wavelength ranges of the optical gratings 17, 18, 19 differing from one another and thus signals being reflected at different wavelengths at the optical gratings 17, 18, 19.
For the wavelength shift, the following applies:
δλi≈0.78·εi·λBi
with
i=1,2 or 3.
The distance between the band gaps λBi, for example, lies in a range between 5 nm and 30 nm, for example is 10 nm, to ensure reliable differentiation of the wavelength shifts &i, which are two to three orders of magnitude smaller.
Three signals S1, S2, S3 of the optical gratings 17, 18, 19 are generated from the wavelength shifts δλ1, δλ2, δλ3. The following applies here:
S
i=1000·δγi
The factor 1000 takes into account the ratio δλi/λBi.
In principle, three distinguishable optical signals from LPG or Fabri-Perot resonators may perform the same function in addition to the FBG signals described above. These signals must only be proportional to three independent components of the force vector . In
, due to an interaction of the functional electrode 2 with tissue 13, acts on the functional electrode 2, points through the centre 43 and is directed at an elevation angle α and an azimuth angle φ to the functional electrode axis 41.
From the signals S1, S2, S3 the force in magnitude and direction may be determined. In this way each force vector may be assigned a signal vector S accordingly:
The signals S1, S2, S3 derived from reflection signals of the optical gratings 17, 18, 19 may be used as components of a signal vector {right arrow over (S)} be interpreted in a signal space. The result is a system of equations with three equations and three unknowns, namely the magnitude of the force FG and the angles α, φ, which may be resolved and a determination of the force vector in respect of amount and direction.
In general, it may be assumed that a risk of perforation on the tissue 13 is greatest when the line of action 42 and the functional electrode axis 41 are at least approximately in alignment with each other. The angle α is then at or near 0°, so that the functional electrode 2 is perpendicular to the surface of the tissue 13. If, on the other hand, the functional electrode 2 with the electrode axis 41 is aligned at least approximately parallel to the tissue 13, the angle α has a value of approximately 90° and there is a comparatively small risk of perforation.
For calibration, a method for generating a characteristic diagram may be used which establishes a relationship between quantities derived from the measurement signals generated by the measuring device and the magnitude and direction of the force vector.
In particular, calibration may be carried out using a 5-point method, as a result of which calibration values are obtained which are used as parameters in a signal-force determination algorithm. After calibration has been carried out, the magnitude of the force FG and the angle α may be calculated from the three derived signals S1, S2, S3 of the optical gratings 17, 18, 19 in a control and evaluation device implemented in a peripheral device and connected to the optical connection 10, using the algorithm. The following applies:
The magnitude of the force FG and the angle α, which may be seen as components of a force vector may be interpreted on one level, may be displayed digitally on a monitor and thus may be made available to a user as information.
If the functional electrode 2, as shown in the present example, has the shape of a hemisphere at its distal end and the distal end face of the functional electrode 2 thus corresponds to a (hemi-)spherical surface, all lines of action of the resulting forces FG run (neglecting friction) between the functional electrode 2 and tissue 13 (in
If the shape of the functional electrode 2 deviates from a spherical shape, a spherical cap with a defined point of action may be placed on functional electrode 2 (play-free) for calibration.
For calibration, a calibration force||=FC and a calibration angle αC between 0° and 90° is selected. Values such as those that may occur during later operational use are useful here, for example. For example, a value of FC=0.29 N, corresponding to 30 g (this corresponds to a reference weight as it is often used in medical practice), and αC=45° may be used for the amount of the calibration force—assuming that the functional electrode 2 will seldom lie exactly perpendicularly or exactly parallel to the surface of a tissue 13 during ablation. In this way it is possible to calibrate to a high measuring accuracy in a working region.
The calibration point 44, to which the calibration force FC is applied, is, for example, on the functional electrode axis 41 of functional electrode 2.
The calibration points 45, 46, 47 are at an angular distance ac (for example 45°) from the functional electrode axis 41. The calibration points 45, 46, 47 must be rotated by Δφ=120° to each other around the axis of rotation.
The calibration point 48 is at an angular distance αC=90° to the functional electrode axis 41 and is shifted by Δφ=0° to one of the calibration points 45, 46, 47. (The absolute angle of rotation φ of the functional electrode 2 has no significance for calibration).
Each of the calibration measurements at the five calibration points 44, 45, 46, 47, 48 yields a signal vector {right arrow over (S)} with three components each. This means that 15 individual values are recorded. Of these, for example, twelve parameters (calibration values) are selected for the signal-force determination algorithm.
From the signal vector {right arrow over (S)}1 of the first calibration point 44, with FC=30 g and αC=0°, four parameters may be calculated for the signal-force determination algorithm:
{right arrow over (SI)}(30g,0°)→{right arrow over (b)}30g,0°=b30g,0°·{right arrow over (eb)}
From the signal vectors {right arrow over (S)}II, {right arrow over (S)}III, {right arrow over (S)}IV of the calibration points 45, 46, 47, with FC=30 g and αC=45° another seven parameters may be calculated for the signal-force determination algorithm:
{right arrow over (SII)}(30g,45°,φ),{right arrow over (SIII)}(30g,45°,φ+120°),{right arrow over (SIV)}(30g,45°,φ+240°)→{right arrow over (b)}30g,45°,{right arrow over (f1)}30g,45°,{right arrow over (f2)}30g,45°
{right arrow over (b)}30g,45° is discarded in favour of {right arrow over (b)}30g,0°=b30g,0°·{right arrow over (e)}b(see above). From {right arrow over (f1)}30g,45° and {right arrow over (f2)}30g,45° only {right arrow over (e)}f1, {right arrow over (e)}f2 and
are adopted.
From the signal vector {right arrow over (S)}V of the calibration point 48, with FC=30 g and αC=90° for 4), φ+120° or for φ+240°, the still missing parameter for the signal-force determination algorithm may be calculated:
{right arrow over (SV)}(30g,90°,φ)→{right arrow over (f1)}30g,90°
All that is required is |{right arrow over (f)}130g,90°|=f130g,90°
This results in twelve calibration parameters (calibration values):
The diagram shows an isoforce area 51 as a grid. All signal vectors {right arrow over (S)} which end from the zero point on this iso-force area 51 are determined by a force vector {right arrow over (FG )} of the same amount FG is generated. The isoforce area 51 has the shape of a tri-axial ellipsoid, where the vectors {right arrow over (ef1)} and {right arrow over (ef2)} are orthogonal to each other. The vector {right arrow over (eb )} may be arbitrary, but must be linearly independent of {right arrow over (ef1)} and {right arrow over (ef2)} be.
For FC=30 g, the isoforce area 51 is fully described with the following vectors shown in
In the areas covered by {right arrow over (f1)} and {right arrow over (b)} and also {right arrow over (f2)} and {right arrow over (b)}, if the isoforce areas 51, 52, 53 are visible when cut. The rays 63 emanating from the zero point correspond to the edges of cut cones. All signal vectors {right arrow over (S)} are generally located on a specific cone, since they always start from zero. Signal vectors {right arrow over (S)} which lie on the same cone represent forces that act at the same angle α from the tissue 13 on the functional electrode 2, but may have different amounts and φ directions.
To determine FG and α, the coordinates f1 and b in the characteristic diagram 55 are first calculated from the underlying signal vector {right arrow over (S)} via the signal-force determination algorithm. With these values the result is:
If α assumes a negative value, the force determined is a tensile force.
A core 65 of the glass fibre 16 and a core 68 of the pigtail 67 are brought into alignment with the geometries of the groove 70 and the structure 71 by aligning the outer radii 73, 74 of the glass fibre 16 on the one hand and the pigtail 67 on the other hand, so that light may be coupled with low loss from the pigtail 67 into the glass fibre 16 used for signal detection and vice versa.
It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teachings of the disclosure. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention, which is to be given the full breadth thereof. Additionally, the disclosure of a range of values is a disclosure of every numerical value within that range, including the end points.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20197779.0 | Sep 2020 | EP | regional |
This application is the United States National Phase under 35 U.S.C. § 371 of PCT International Patent Application No. PCT/EP2021/072485, filed on Aug. 12, 2021, which claims the benefit of European Patent Application No. 20197779.0, filed on Sep. 23, 2020, the disclosures of which are hereby incorporated by reference herein in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/072485 | 8/12/2021 | WO |
