Monitoring torsion on distal end assembly

Abstract

To measure the force on a catheter.SOLUTION: There is provided an apparatus for measuring a torque, consisting of a probe having a shaft with a shaft distal end. The probe has a distal end assembly, configured to be inserted into an organ of a human subject, and having a distal termination and a proximal termination connected to the shaft distal end. A position sensor assembly is attached to the distal end assembly in proximity to the distal termination of the distal end assembly, the position sensor assembly being configured to provide signals indicative of a three-dimensional position and orientation of the distal termination with respect to the shaft distal end. A processor is configured to compute a torsion of the distal termination with respect to the proximal termination in response to the signals from the position sensor assembly, and compute the torque on the distal end assembly in response to the torsion and a predetermined correspondence between the torsion and the torque.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure generally relates to catheters, and more specifically to measuring forces applied to a catheter.

Background Art

[0002] In a catheter configured to ablate tissue, the distal end assembly of the catheter can be maneuvered to a target area of the tissue. Electrodes on the distal end assembly may then be used to ablate the target area tissue.

Brief Description of the Drawings

[0003] The present disclosure will be understood from the following detailed description in conjunction with the accompanying drawings.

Figure 1

Figure 2A

Figure 2B

Figure 3

Figure 4

Figure 5A

Figure 5B

Modes for Carrying Out the Invention

[0004] Overview A catheter having a distal end assembly in the form of a basket or balloon can be advantageously used, for example, for ablation at the opening of a pulmonary vein. When the distal end assembly is accurately positioned, a circular ablation line can be generated by energizing a plurality of electrodes of the assembly simultaneously. The simultaneity shortens the overall time of the ablation procedure.

[0005] In the case of a basket distal end assembly, the spline of the assembly is flexible, and as a result, the assembly can be maneuvered to a desired position within the heart, and the electrodes on the spline conform better to the shape of the tissue to be ablated. However, the flexibility of the spline means that when the distal end assembly is maneuvered to a predetermined position and the electrodes are in contact with the tissue, the assembly can twist as a whole with respect to the catheter shaft. Also, in the case of a balloon, the assembly may twist with respect to the shaft. In addition to twisting, the distal end assembly can be pressed against the tissue.

[0006] While the physician is maneuvering and / or positioning the catheter at the selected ablation site, torque can be established between the twisted distal end assembly and the contacting tissue. The quality and extent of ablation performed by the electrodes depend on the force applied by the electrodes to the tissue. It is important to consider torque when accessing the force applied to the individual electrodes.

[0007] Embodiments of the present disclosure provide a method for determining the torque generated by a distal end assembly by sensing the twist, i.e., angular rotation, of the distal tip of the assembly with respect to the shaft. A plurality of position sensors are attached near the distal tip of the distal end assembly. During the procedure, for example, during an ablation procedure, the position and orientation of the sensors with respect to the shaft are measured, and from the measurements, the twist of the distal tip around the axis defined by the catheter shaft is calculated.

[0008] The calibration procedure performed before the ablation procedure finds the correspondence between the angular rotation generated, i.e., the twist, and the torque that generates the rotation. In one example, the correspondence is model-based, assuming that the distal assembly behaves elastically. The correspondence is then used in the ablation procedure to find the total torque on the assembly from the measured angular rotation. During the ablation procedure, the electrodes of the distal assembly in contact with the tissue are identified. Since the positions of the contact electrodes of the distal assembly are known, the force on each of the electrodes can be calculated from the total torque.

[0009] Description of the System In the following description, like elements are identified by the same numerals and, where necessary, are distinguished by adding a letter as a suffix to the numeral.

[0010] Referring now to FIG. 1, there is shown a catheter-based electrophysiology mapping and ablation system 10, according to an example of the present disclosure, being used in a medical procedure. The system 10 includes a plurality of catheters that are percutaneously inserted by a physician 24 through a patient's vasculature and into a chamber or vascular structure of the patient's heart 12. Typically, a delivery sheath catheter is inserted into the left or right atrium near the desired location of the heart 12. Thereafter, the plurality of catheters can be inserted into the delivery sheath catheter to reach the desired location. The plurality of catheters can include catheters dedicated to sensing intracardiac electrogram (IEGM) signals, catheters dedicated to ablation, and / or catheters dedicated to both sensing and ablation.

[0011] An exemplary catheter 14, also referred to herein as probe 14, configured for ablation treatment is illustrated herein. The probe includes an insertion shaft 37 and a distal end assembly 28 fixed to the distal end of the shaft. During an ablation treatment, when the distal end assembly 28 exits the delivery sheath, the physician 24 operates the proximal end of the shaft 37 to contact the assembly with the heart wall 31 of the chamber 36 of the heart 12 for the purpose of ablating the target site on the wall.

[0012] FIG. 2A is a schematic view of the distal end assembly 28 in a fully deployed and unconstrained form, i.e., with no contact force applied to the distal end assembly. FIG. 2B is a schematic view of the unconstrained assembly along the assembly axis according to an example of the present invention. In the description herein, unless otherwise specified, the catheter 14 is assumed to include a basket catheter, and thus the distal end assembly 28 is a basket configured as a plurality of similar elastic splines 13A, 13B,... collectively referred to as splines 13. The splines 13 form the assembly 28 to have a generally elliptical shape in rotation and function as a support structure for the attached electrodes 26, and thus may also be referred to herein as support structure 13.

[0013] Each spline of the structure 13 has at least one attached electrode 26 that can be used for ablation. Each spline has a known length, and each attached electrode 26 is at a known position on its respective spline. Each proximal end 16 of the splines is fixedly disposed at the distal end 19 of the shaft 37 and functions together as the proximal end of the distal end assembly 28. The distal ends 15 of the splines branch, and the branches are connected to each other by a substantially rigid loop 17 that joins adjacent splines. Other structures for connecting the distal ends 15 are contemplated herein. The distal structure 34 of the assembly, optionally including the loop 17 as an example herein, formed by the connection of the distal ends 15 is typically substantially rigid. The distal structure 34 functions as the distal end of the distal end assembly 28.

[0014] In the example of the distal end assembly 28 shown in FIGS. 2A and 2B, there are 10 distributed splines 13 around an assembly axis, herein referred to as the z-axis, that is collinear with the central axis of the distal end 19 of the shaft 37. However, it will be understood that the assembly 28 may have more or fewer distributed splines than 10.

[0015] As shown in FIG. 2A, the ends 15 of the splines 13 are proximate to a distal point 33 that is centered on the structure 34, and the z-axis includes the line from the distal point to the center of the shaft 37. The ends 15 are symmetrically distributed around the distal point 33.

[0016] The position sensor 35 is disposed at the distal end 19 of the shaft 37. In addition, a plurality of generally similar position sensors 29A, 29B,... are attached to respective different splines 13A, 13B,... proximate the distal ends 15 of the splines. The sensors 29A, 29B,... operate as a position sensor assembly 29 and are attached to respective splines so as to form a three-dimensional (3D) configuration. Since the splines are inclined relative to each other, it will be understood that in the 3D configuration, the axes of their attached sensors are also inclined relative to each other. By having sensors thus inclined, even if the sensors are magnetic-based uniaxial sensors, the signals from the plurality of sensors provide complete 3D information of the attached splines. In the disclosed embodiment, as shown, there are three position sensors 29A, 29B, and 29C on splines 13A, 13B, and 13C, respectively, although other embodiments may have more or fewer than three sensors.

[0017] The splines to which the sensors of the assembly 29 are attached are selected such that the sensors are distributed at least substantially symmetrically with respect to the z-axis. Thus, in the disclosed example using splines 13A, 13B, and 13C, ten splines 13 are separated by 36°, and the angles between splines 13A, 13B, and 13C are 108°, 108°, and 144°. Selecting the splines to be distributed substantially symmetrically ensures that adjacent sensors of the splines are separated as much as possible.

[0018] The position sensors 35 and the position sensors of the assembly 29 are typically magnetic-based position sensors having at least one coil. In the disclosed example, the position sensor 35 is a two-axis or three-axis coil, and the sensors of the assembly 29 are single-axis coils. The sensors 35 and the sensors of the assembly 29 can be operated using a position pad 25 that includes a plurality of magnetic coils 32 configured to generate a magnetic field within a predetermined working volume. The real-time position of the multi-axis sensor 35, i.e., the three-dimensional (3D) position and 3D orientation of the sensor, can be tracked based on the magnetic field generated by the position pad 25 and sensed by the sensor. Similarly, the real-time position of the single-axis sensors of the assembly 29, i.e., their 3D positions and 2D orientations, may be tracked based on the magnetic field from the position pad 25. Details of magnetic-based position sensing techniques are described in U.S. Patent Nos. 5,539,199; 5,443,489; 5,558,091; 6,172,499; 6,239,724; 6,332,089; 6,484,118; 6,618,612; 6,690,963; 6,788,967; 6,892,091.

[0019] In some examples, one or more coils 41 are disposed at the distal end 19, and the coils are configured to generate a magnetic field in a manner generally similar to the coils of the position pad 25. The magnetic field from the coils 41 enables tracking of the position of the sensors of the assembly 29 relative to the coils 41. U.S. Patent Application Publication No. 2020 / 0206461 provides details of a magnetic tracking system similar to that using the coils 41, where a magnetic field generator on a basket catheter shaft is used to find the position of sensors on the basket.

[0020] In some examples, the sensor 35 is configured to operate as a position sensor and a magnetic field generator, either sequentially or simultaneously. When operating in this mode, the position of the sensor 35 relative to the position pad 25 is determined using the magnetic field from the position pad, and the position of the sensors of the assembly 29 is determined relative to the coils 41 (from their magnetic fields) and also relative to the position pad 25.

[0021] The unconstrained form of the distal end assembly 28 shown in FIG. 2A is understood to exist before the assembly enters the delivery sheath as described above. As described above, during an ablation procedure, the physician 24 manipulates the proximal end of the catheter shaft 37 to bring the distal end assembly 28 into contact with the heart wall 31. This manipulation typically involves the physician 24 pushing, pulling, bending, and / or rotating the proximal end of the shaft 37 to move the assembly 28 to the desired position in contact with the wall 31.

[0022] When at least some of the electrodes 26 of the distal end assembly are in contact with the wall 31, the assembly can be twisted from its unconstrained form relative to the shaft 37. In the constrained and twisted form of the assembly, the tissue in contact with the electrodes exerts respective forces on the electrodes, generating torque on the assembly, and the electrodes exert respective counteracting forces on the tissue. The following description, with reference to FIG. 5, explains how the examples of the present disclosure identify both the torque on the assembly and the forces on the assembly electrodes due to the torque.

[0023] Figure 3 is a schematic view of an alternative distal end assembly 128 according to an example of the present disclosure. Except for the differences described below, the operation of assembly 128 is generally the same as the operation of assembly 28 (Figures 2A and 2B), and elements denoted by the same reference numerals in both assembly 28 and assembly 128 generally have the same configuration and operation. In contrast to assembly 28 in which electrode 26 is attached as a single electrode, in assembly 128, electrodes 26 are attached in groups. As an example, in the illustrated example of assembly 128, electrodes 26 are in three groups. With respect to assembly 28, in assembly 128, the sensors of assembly 29 are in the distal portion of assembly 128 in a 3D configuration.

[0024] Figure 4 is a schematic view of a further alternative distal end assembly 228 according to an example of the present disclosure. Except for the differences described below, the operation of assembly 228 is generally the same as the operation of assemblies 28 and 128 (Figures 2A, 2B, and 3), and elements denoted by the same reference numerals within assemblies 28, 128, and 228 generally have the same configuration and operation.

[0025] In contrast to assemblies 28 and 128, the distal end assembly 228 is formed as a balloon assembly and has a balloon 232 that, when inflated, has a generally oblate ellipsoidal shape. Balloon 232 functions as a support structure for ablation electrode 236 attached to the balloon via electrode substrate 238 and can thus also be referred to herein as support structure 232. In Figure 4, assembly 228 is shown in an inflated state with balloon 232 attached to shaft 37.

[0026] The balloon tip 240 is at the distal end of the balloon and, together with the center of the shaft 37, defines the z-axis as the axis of the assembly 228. (The lasso catheter 244 is shown as extending from the balloon tip 240 and may be used to position the balloon assembly 228 at a desired location.) With respect to assemblies 28 and 128, the position sensors of the assembly 29 (in the example shown, there are three sensors 29A, 29B, 29C) are attached to the balloon 232 in proximity to the tip 240 in the 3D configuration described above.

[0027] For simplicity and clarity, the following description pertains to the distal end assembly 28, and those skilled in the art will be able to adapt this description, with necessary modifications, to other distal end assemblies such as the assembly 128 and the assembly 228. Accordingly, the scope of the present disclosure includes other basket catheters having a distal end assembly with a plurality of elastic splines, each spline having at least one electrode usable for ablation. The scope of the present disclosure also includes other balloon catheters having a balloon to which an electrode suitable for ablation is attached.

[0028] Returning to FIG. 1, the system 10 includes one or more electrode patches 38 disposed for skin contact with the patient 23. Measurement of the impedance between a patch 38 and a given electrode 26 can be used to identify whether the electrode is in contact with the tissue of the wall 31. U.S. Patent No. 11,596,324 describes a method that can use the impedance between an electrode on a basket catheter and a patch on a patient's skin to identify whether the electrode is in contact with the tissue within the lumen of the subject's organ. Optionally, the impedance between intracardiac electrodes can be sensed to evaluate contact with the chamber wall. The intracardiac electrodes may include electrodes on the distal end assembly and / or electrodes on the distal end of the catheter shaft.

[0029] Recorder 11 displays the electrocardiogram 21 captured by the body surface ECG electrodes 18 and the intracardiac electrogram (IEGM) that can be captured by the electrodes 26 of the catheter 14. Recorder 11 may include pacing capabilities for pacing the rhythm of the heart and / or may be electrically connected to an independent pacemaker.

[0030] System 10 may include an ablation energy generator 50 adapted to deliver ablation energy to one or more of the electrodes 26. The energy generated by ablation energy generator 50 may include high frequency (RF) energy or pulsed field ablation (PFA) energy, such as unipolar or bipolar high voltage DC pulses that can be used to effect irreversible electroporation (IRE), or combinations thereof, but is not limited thereto.

[0031] The patient interface unit (PIU) 30 is an interface configured to establish electrical communication between the catheter, the electrophysiology device, the power source, and a workstation 55 that controls the operation of system 10. The electrophysiology devices of system 10 may include, for example, multiple catheters, position pads 25, body surface ECG electrodes 18, electrode patches 38, ablation energy generator 50, and recorder 11. Optionally and preferably, PIU 30 implements real-time calculation of the position of the catheter and additionally includes processing capabilities for performing ECG calculations.

[0032] The workstation 55 includes a memory, a processor 22 having a memory or storage device in which appropriate operating software is stored, and a user interface function. The processor 22 operates the system 10. The workstation 55 may optionally include a number of functions, including: (1) rendering to model in three dimensions (3D) the endocardial anatomical structure and display on the display device 27 a model or anatomical map 20 of the heart 12 or a part thereof; (2) displaying on the display device 27 an activation sequence (or other data) compiled from the recorded electrogram 21 as a representative visual indicator or image superimposed on the rendered anatomical map 20; (3) displaying a presentation 39 incorporating real-time position and orientation values of the distal end assembly 28 within the cardiac chamber 36; and (4) displaying on the display device 27 a site of interest, such as the location where ablation energy has been applied. One commercially available product embodying the elements of the system 10 is available as the CARTO (trademark) 3 system, commercially available from Biosense Webster, Inc., 31 Technology Drive, Suite 200, Irvine, CA 92618.

[0033] Referring now to FIG. 5A, this is a flowchart 300 illustrating a calibration algorithm executed by the processor 22, according to an example of the present disclosure.

[0034] The algorithm of the flowchart 300 is assumed to be executed by the processor 22.

[0035] In the initial calibration step 304 of the flowchart, which is performed before the ablation treatment in which the distal assembly 28 is used, the distal assembly is calibrated. The calibration process applies a known torque to the assembly 28, and for each applied torque, the average angular deflection of the sensors of the assembly 29, i.e., the twist, is registered and measured with respect to the distal end 19 of the shaft 37. As explained above, the position sensor 35 on the distal end 19 of the shaft 37 (to which the assembly 28 is attached) measures the orientation of the distal end 19 in 3D.

[0036] As described above, the deflection of each sensor from the unconstrained position is measured from the sensor signals generated in response to the magnetic field transmitted from the position pads 25 and / or the coils 41. The torque may be applied by any convenient method, such as twisting the distal end of the assembly 26 and monitoring the torque required for the twist.

[0037] In the storage step 306, as a result of the calibration process, the processor 22 stores the correspondence between the torque applied to the assembly 28 and the average deflection of the position sensors of the assembly 29 and / or the angular deflection of the distal structure 34. The correspondence may be in any convenient form, such as a look-up table or a model-based relationship.

[0038] In the disclosed example, the correspondence is model-based, assuming that the assembly 28 behaves elastically and has a direct proportionality according to Equation (1). T = k·θ (1) where T is the torque applied to the assembly, measured in N·m, θ is the average angular deflection of the sensors of the assembly 29 measured in degrees, k is the proportionality constant of Equation (1) corresponding to the spring constant of the assembly.

[0039] In step 306, the processor 22 calculates the spring constant k of the assembly.

[0040] Figure 5B is a flowchart 310 that illustrates an operational algorithm executed by processor 22 during an ablation procedure. In this procedure, physician 24 inserts catheter 14 into heart 12 until distal assembly 28 comes to a desired target position where it contacts wall 31. Processor 22 uses the algorithm to verify the torque applied to distal end assembly 28 and the respective forces on electrodes 26 of the assembly as a result of the applied torque.

[0041] The following description of flowchart 310 assumes that the correspondence between torque and average angular deflection given by Equation (1) applies, and one of ordinary skill in the art can adapt the description by making the necessary changes for other types of correspondences.

[0042] In measurement step 308, processor 22 records the measured position of the sensors of assembly 29. From the measured position relative to shaft distal end 19, the processor calculates the average angular deflection of the sensors, i.e., the twist of distal end assembly 28. It will be understood that the sensors of assembly 29 do not necessarily deflect symmetrically with respect to the z-axis. For example, the angular deflection can be asymmetric if distal end assembly 28 is deflected as a whole relative to shaft distal end 19.

[0043] The average angular deflection of the sensors of assembly 29 is θ m and is assumed to be.

[0044] Processor 22 uses the calculated value of the average angular deflection and the spring constant k of the assembly determined in calibration step 304 of flowchart 300 to calculate the total torque T applied to the assembly according to Equation (2). m to calculate. T m = k·θ m (2)

[0045] The torque to the assembly 28 is generated by the electrodes 26 contacting the wall 31, and in the counting step 312, the processor 22 determines the number of electrodes contacting the wall. The processor can identify which of the electrodes 26 is in contact with the tissue of the wall 31 using impedance-based measurements as described above.

[0046] For each electrode 26 identified as being in contact with the wall 31, the processor 22 also records the position of the electrode. The position may be calculated based on the measured twist of the electrode or, alternatively or additionally, using impedance-based measurements as described, for example, with reference to FIG. 1. Further alternatively or additionally, the position may be recorded using the known position of the electrode on the spline 13 and the dimensions of the spline.

[0047] From the positions recorded for each electrode, the processor 22 calculates a vector that includes the distance and direction from the electrode to the axis of the assembly 28, i.e., the z-axis.

[0048] It is understood that each electrode contacting the tissue of the wall 31 contributes to the total torque to the assembly 28, and as a result, the calculated vector corresponds to the stress center distance vector of the torque generated by the electrode.

[0049] In the electrode-force step 316, the processor 22 estimates the torsional force on each electrode using the results calculated in steps 308 and 312.

[0050] In the disclosed example, the total measured torque T m is assumed to be evenly distributed among all the contacting electrodes. In this case, the magnitude of the torsional force on each electrode is given by Equation (3).

[0051]

Equation

[0052] Equation (3) gives the magnitude of the torsional force on the electrode E. The direction of the torsional force on the electrode E is orthogonal to the axis of symmetry of the assembly 28 and also orthogonal to the stress center distance vector of the electrode E.

[0053] The above results, i.e., the values generated from Equations (2) and (3), and the direction of the force on the electrodes of the distal end assembly, can be provided to the physician 24, for example, using the display device 27. For a given electrode, the results may be combined with the forces arising from the electrodes pressing against the tissue in a non-torsional manner, and the overall resultant force on the given electrode may be provided to the physician 24.

Example

[0054] Example 1. An apparatus for measuring torque, comprising a probe (14), comprising a shaft (37) having a shaft distal end (19), a distal end assembly configured to be inserted into an organ of a subject, having a distal end (34) and a proximal end (16) connected to the shaft distal end (28), a position sensor assembly (29) attached to the distal end assembly in proximity to the distal end of the distal end assembly, the position sensor assembly being configured to provide a signal indicative of the three-dimensional (3D) position and orientation of the distal end relative to the shaft distal end, a processor (22) configured to calculate the twist of the distal end relative to the proximal end in response to a signal from the position sensor assembly, and to calculate the torque on the distal end assembly in response to the twist and a predetermined correspondence between the twist and the torque.

[0055] Example 2. The apparatus according to Example 1, comprising a shaft position sensor (35) attached to the distal end of the shaft and configured to provide a signal indicating the orientation of the shaft, wherein the processor is configured to calculate the twist with respect to the orientation of the shaft.

[0056] Example 3. The apparatus according to Example 1, comprising a magnetic field generator (41) attached to the distal end of the shaft, wherein the signal from the position sensor assembly is generated in response to the magnetic field from the generator, and the processor is configured to calculate the twist with respect to the orientation of the shaft.

[0057] Example 4. The apparatus according to Example 1, wherein a predetermined correspondence is based on modeling the distal end assembly as an elastic assembly.

[0058] Example 5. The apparatus according to Example 1, comprising a plurality of electrodes (26) attached to the distal end assembly, wherein the processor is configured to identify the electrodes in contact with the tissue of the organ, evaluate the number of electrodes in contact, and calculate the electrode-torque to a given electrode among the electrodes in contact in response to the number and torque.

[0059] Example 6. The apparatus according to Example 5, wherein the processor is configured to determine the distance of a given electrode to the torsional axis connecting the proximal end to the distal end, and calculate the magnitude of the force on the given electrode in response to the electrode-torque and the distance.

[0060] Example 7. The apparatus according to Example 5, wherein the processor is configured to determine a vector from a given electrode to the torsional axis connecting the proximal end to the distal end, and calculate the direction of the force on the given electrode in response to the vector and the orientation of the torsional axis.

[0061] Example 8. The apparatus according to Example 5, wherein the processor is configured to determine the force on a given electrode in response to the given electrode pressing the tissue in a non-twisted manner.

[0062] Example 9. The device according to Example 1, wherein the distal end assembly comprises a balloon.

[0063] Example 10. The device according to Example 1, wherein the distal end assembly comprises a plurality of splines.

[0064] Example 11. A method for measuring torque, comprising: providing a probe (14), the probe comprising: a shaft (37) having a shaft distal end (19); and a distal end assembly configured to be inserted into a subject's organ, the distal end assembly having a distal end (34) and a proximal end (16) connected to the shaft distal end (28); and a position sensor assembly (29) attached to the distal end assembly in proximity to the distal end of the distal end assembly, the position sensor assembly being configured to provide a signal indicative of the three-dimensional (3D) position and orientation of the distal end relative to the shaft distal end; calculating the twist of the distal end relative to the proximal end in response to a signal from the position sensor assembly; and calculating the torque on the distal end assembly in response to the twist and a predetermined correspondence between the twist and the torque.

[0065] Example 12. The method according to Example 11, comprising attaching a shaft position sensor (35) configured to provide a signal indicative of the orientation of the shaft, and calculating the twist relative to the orientation of the shaft.

[0066] Example 13. The method according to Example 11, comprising attaching a magnetic field generator (41) to the shaft distal end, wherein the signal from the position sensor assembly is generated in response to a magnetic field from the generator, and calculating the twist relative to the orientation of the shaft.

[0067] Example 14. The method according to Example 11, wherein a given correspondence is based on modeling the distal end assembly as an elastic assembly.

[0068] Example 15. The method according to Example 11, comprising attaching a plurality of electrodes (26) attached to the distal end assembly, identifying the electrodes that contact the tissue of the organ, evaluating the number of contacting electrodes, and calculating the electrode-torque to a given electrode among the contacting electrodes in response to the number and torque.

[0069] Example 16. The method according to Example 15, comprising determining the distance of a given electrode to the torsional axis connecting the proximal end to the distal end, and calculating the magnitude of the force on the given electrode in response to the electrode-torque and the distance.

[0070] Example 17. The method according to Example 15, comprising determining a vector from a given electrode to the torsional axis connecting the proximal end to the distal end, and calculating the direction of the force on the given electrode in response to the vector and the direction of the torsional axis.

[0071] Example 18. The method according to Example 15, comprising determining the force on a given electrode in response to the given electrode pressing the tissue in a non-torsional manner.

[0072] Example 19. The method according to Example 11, wherein the distal end assembly comprises a balloon.

[0073] Example 20. The method according to Example 11, wherein the distal end assembly comprises a plurality of splines.

[0074] The above examples are cited by way of example, and the present disclosure is not limited to what is specifically shown and described in the above specification. Rather, the scope of the present disclosure includes both the combinations and sub-combinations of the various features described in the above specification, as well as those variations and modifications not disclosed in the prior art that would be contemplated by those skilled in the art upon reading the above description.

[0075] 〔Embodiment〕 (1) An apparatus for measuring torque, comprising: a probe, comprising: a shaft having a distal end of the shaft; and a distal end assembly configured to be inserted into an organ of a subject, the distal end assembly having a distal end and a proximal end connected to the distal end of the shaft; and a position sensor assembly attached to the distal end assembly in proximity to the distal end of the distal end assembly, the position sensor assembly being configured to provide a signal indicative of a three-dimensional (3D) position and orientation of the distal end relative to the distal end of the shaft; a processor configured to calculate a twist of the distal end relative to the proximal end in response to the signal from the position sensor assembly, and to calculate the torque on the distal end assembly in response to the twist and a predetermined correspondence between the twist and the torque; The apparatus comprising. (2) The apparatus according to Embodiment 1, further comprising a shaft position sensor attached to the distal end of the shaft and configured to provide a signal indicative of the orientation of the shaft, the processor being configured to calculate the twist relative to the orientation of the shaft. (3) The apparatus according to Embodiment 1, further comprising a magnetic field generator attached to the distal end of the shaft, the signal from the position sensor assembly being generated in response to a magnetic field from the generator, the processor being configured to calculate the twist relative to the orientation of the shaft. (4) The apparatus according to Embodiment 1, wherein the predetermined correspondence is based on modeling the distal end assembly as an elastic assembly. (5) The apparatus according to Embodiment 1, further comprising a plurality of electrodes attached to the distal end assembly, the processor being configured to identify electrodes in contact with tissue of the organ, evaluate the number of the contacting electrodes, and calculate an electrode-torque on a given one of the contacting electrodes in response to the number and the torque.

[0076] (6) The apparatus according to embodiment 5, wherein the processor is configured to determine a distance of the given electrode to a torsional axis connecting the proximal end to the distal end, and to calculate a magnitude of a force on the given electrode in response to the electrode-torque and the distance. (7) The apparatus according to embodiment 5, wherein the processor is configured to determine a vector from the given electrode to a torsional axis connecting the proximal end to the distal end, and to calculate a direction of a force on the given electrode in response to the vector and an orientation of the torsional axis. (8) The apparatus according to embodiment 5, wherein the processor is configured to determine a force on the given electrode in response to the given electrode pressing the tissue in a non-torsional manner. (9) The apparatus according to embodiment 1, wherein the distal end assembly comprises a balloon. (10) The apparatus according to embodiment 1, wherein the distal end assembly comprises a plurality of splines.

[0077] (11) A method for measuring torque, comprising: providing a probe, the probe comprising: a shaft having a distal end of the shaft; and a distal end assembly configured to be inserted into an organ of a subject and having a distal end and a proximal end connected to the distal end of the shaft; and a position sensor assembly attached to the distal end assembly in proximity to the distal end of the distal end assembly, the position sensor assembly being configured to provide a signal indicative of a three-dimensional (3D) position and orientation of the distal end with respect to the distal end of the shaft; calculating a torsion of the distal end with respect to the proximal end in response to the signal from the position sensor assembly; calculating the torque on the distal end assembly in response to the torsion and a predetermined correspondence between the torsion and the torque; A method comprising... (12) Attaching a shaft position sensor configured to provide a signal indicative of the orientation of the shaft; and calculating the twist of the shaft relative to the orientation. The method according to embodiment 11. (13) Attaching a magnetic field generator to the distal end of the shaft, wherein the signal from the position sensor assembly is generated in response to the magnetic field from the generator; and calculating the twist of the shaft relative to the orientation. The method according to embodiment 11. (14) The method according to embodiment 11, wherein the predetermined correspondence is based on modeling the distal end assembly as an elastic assembly. (15) Attaching a plurality of electrodes attached to the distal end assembly; identifying the electrodes in contact with the tissue of the organ; evaluating the number of the contacting electrodes; and calculating an electrode-torque to a given electrode among the contacting electrodes in response to the number and the torque. The method according to embodiment 11.

[0078] (16) Determining the distance of the given electrode to the twist axis connecting the proximal end to the distal end; and calculating the magnitude of the force on the given electrode in response to the electrode-torque and the distance. The method according to embodiment 15. (17) Determining a vector from the given electrode to the twist axis connecting the proximal end to the distal end; and calculating the direction of the force on the given electrode in response to the vector and the orientation of the twist axis. The method according to embodiment 15. (18) Determining the force on the given electrode in response to the given electrode pressing the tissue in a non-twisted manner. The method according to embodiment 15. (19) The method according to embodiment 11, wherein the distal end assembly comprises a balloon. (20) The method according to embodiment 11, wherein the distal end assembly comprises a plurality of splines.

Claims

1. 1. An apparatus for measuring torque, comprising: A probe comprising: a shaft having a shaft distal end; a distal tip assembly configured to be inserted into an organ of a subject, the distal tip assembly having a distal terminus and a proximal terminus connected to the shaft distal end; a position sensor assembly attached to the distal tip assembly proximate to the distal end of the distal tip assembly, the position sensor assembly configured to provide a signal indicative of a three-dimensional (3D) position and orientation of the distal end relative to the shaft distal end; a processor configured to calculate a twist of the distal end relative to the proximal end in response to the signal from the position sensor assembly, and to calculate the torque on the distal tip assembly in response to the twist and a predetermined correspondence between the twist and the torque; An apparatus comprising:

2. 2. The apparatus of claim 1, further comprising a shaft position sensor attached to a distal end of the shaft and configured to provide a signal indicative of an orientation of the shaft, the processor configured to calculate the twist relative to the orientation of the shaft.

3. 2. The device of claim 1, further comprising a magnetic field generator attached to a distal end of the shaft, the signal from the position sensor assembly being generated in response to a magnetic field from the generator, and the processor configured to calculate the twist relative to the orientation of the shaft.

4. The apparatus of claim 1 , wherein the predetermined correspondence is based on modeling the distal tip assembly as an elastic assembly.

5. 2. The device of claim 1, comprising a plurality of electrodes attached to the distal end assembly, and wherein the processor is configured to identify electrodes contacting tissue of the organ, assess a number of the contacting electrodes, and calculate an electrode-torque for a given one of the contacting electrodes in response to the number and the torque.

6. 6. The apparatus of claim 5, wherein the processor is configured to determine a distance of the given electrode to a torsional axis connecting the proximal terminus to the distal terminus and calculate a magnitude of a force on the given electrode in response to the electrode-torque and the distance.

7. 6. The device of claim 5, wherein the processor is configured to determine a vector from the given electrode to a torsion axis connecting the proximal terminus to the distal terminus, and to calculate a direction of a force on the given electrode in response to an orientation of the vector and the torsion axis.

8. The apparatus of claim 5 , wherein the processor is configured to determine a force on the given electrode in response to the given electrode pressing against the tissue in a non-torsional manner.

9. The device of claim 1 , wherein the distal end assembly comprises a balloon.

10. The device of claim 1 , wherein the distal tip assembly comprises a plurality of splines.

11. 1. A method for measuring torque, comprising: Providing a probe, said probe comprising: a shaft having a shaft distal end; a distal tip assembly configured to be inserted into an organ of a subject, the distal tip assembly having a distal terminus and a proximal terminus connected to the shaft distal end; a position sensor assembly attached to the distal tip assembly proximate the distal end of the distal tip assembly, the position sensor assembly configured to provide a signal indicative of a three-dimensional (3D) position and orientation of the distal end relative to the shaft distal end; calculating a twist of the distal end relative to the proximal end in response to the signal from the position sensor assembly; calculating the torque on the distal tip assembly in response to the twist and a predetermined correspondence between the twist and the torque; A method comprising:

12. The method of claim 11 , comprising: attaching a shaft position sensor configured to provide a signal indicative of an orientation of the shaft; and calculating the twist relative to the orientation of the shaft.

13. 12. The method of claim 11, comprising: attaching a magnetic field generator to the distal end of the shaft, the signal from the position sensor assembly being generated in response to a magnetic field from the generator; and calculating the twist relative to the orientation of the shaft.

14. The method of claim 11 , wherein the predetermined correspondence is based on modeling the distal tip assembly as an elastic assembly.

15. 12. The method of claim 11, comprising mounting a plurality of electrodes attached to the distal tip assembly, identifying electrodes contacting tissue of the organ, assessing a number of the contacting electrodes, and calculating an electrode-torque for a given one of the contacting electrodes in response to the number and the torque.

16. 16. The method of claim 15, comprising: determining a distance of the given electrode to a torsional axis connecting the proximal terminus to the distal terminus; and calculating a magnitude of a force on the given electrode in response to the electrode-torque and the distance.

17. 16. The method of claim 15, comprising: determining a vector from the given electrode to a torsion axis connecting the proximal terminus to the distal terminus; and calculating a direction of a force on the given electrode in response to an orientation of the vector and the torsion axis.

18. The method of claim 15, comprising determining a force for the given electrode in response to the given electrode pressing against the tissue in a non-torsional manner.

19. The method of claim 11 , wherein the distal end assembly comprises a balloon.

20. The method of claim 11 , wherein the distal end assembly comprises a plurality of splines.

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