Estimation of contact forces for catheter expandable assemblies

Abstract

The name of the invention is estimation of contact force of a catheter expandable assembly. A system includes a medical probe and a processor. The medical probe comprises: a shaft for insertion into a cavity of an organ of a patient; an expandable assembly fitted at the distal end of the shaft, where the expandable assembly has an elastic property; a position sensing element mounted on the distal end of the shaft; and at least one distal position sensing element located on the distal end of the expandable assembly. The processor senses a relative position of each of the at least one distal position sensing element and the proximal position sensing element; determining a deflection of the expandable component based on the relative position; correlating the deflection with a contact force exerted on the expandable component; and providing an indication of the contact force on a display.

Description

Technical Field

[0001] The present disclosure relates generally to invasive medical probes, and particularly to contact force detection of cardiac catheters. Background Art

[0002] A cardiac catheter typically includes an elongated shaft for insertion into a patient's body and a distal end including one or more electrodes and / or sensors. The catheter may further include a magnetic position sensor mounted at the distal end of the shaft.

[0003] Using the signals acquired by the magnetic position sensor, the processor is able to accurately estimate the position and orientation of the distal end of the shaft inside the patient's body.

[0004] It is also known to sense the contact force applied to the distal end. One way to estimate the contact force of a distal end assembly is described in U.S. Patent 8,535,308. The patent describes a spring-loaded joint that connects the distal tip to the distal end of a shaft. A joint sensor housed within a catheter senses the position of the distal tip relative to the distal end of the shaft. The joint sensor includes a first subassembly and a second subassembly that are disposed on opposite respective sides of the joint within the catheter and each include one or more magnetic transducers. Based on the position signals transmitted and received by the subassemblies, the deflection is estimated from the relative position of the subassemblies. Based on the known spring constant of the joint, the tip contact force is estimated from the deflection.

[0005] The present disclosure will be more fully understood through the following detailed description of examples of the present disclosure in conjunction with the accompanying drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic illustration of a catheter-based electroanatomical (EA) mapping and ablation system according to an example of the present disclosure;

[0007] FIG. 2A to FIG. 2C Schematic illustrations of an expandable distal tip assembly of a catheter according to an embodiment of the present disclosure (i) in free space, (ii) compressed against tissue, and (iii) tilted by contacting tissue;

[0008] Figure 3 is a schematic illustration of a catheter expandable distal tip assembly in a deformed shape when pressed against tissue according to an example of the present disclosure; and

[0009] Figure 4 is a schematic diagram according to an example of the present disclosure showing an estimation such as FIG. 2 or Figure 3 A flow chart of a method for extending the contact force of a distal tip assembly in contact with tissue. DETAILED DESCRIPTION

[0010] Overview

[0011] The wall cavity of the patient's organ (such as a heart cavity) can be mapped and / or ablated using a catheter having a plurality of electrodes mounted at an expandable distal end assembly of the catheter. The expandable distal end assembly is coupled at the distal end of the catheter shaft for insertion into the cavity. The expandable distal end assembly can be shaped in the form of an air bag, a basket and / or another type of cage, and can include a plurality of electrodes configured for sensing and / or delivering therapeutic signals. The expandable distal end assembly can include a plurality of splines connected at its proximal end and distal end. When expanded, the splines are bent radially outward. When collapsed, the splines are arranged roughly along the axis of the shaft. Electrodes and / or sensors can be arranged on the splines of the balloon and / or on the membrane for the distal end of the balloon. The expandable distal end assembly may also be referred to as an expandable assembly herein.

[0012] In the mapping and / or ablation procedures of the cardiac chambers, the physician expands the assembly and manipulates the expanded distal end assembly to contact the electrode with the cavity wall. The quality of electroanatomical mapping (e.g., based on the depolarized signals collected by the electrodes) and / or ablation depends on the contact force of the electrode with the wall tissue. Estimating such forces on the shaft may be difficult because the elasticity of the expandable distal end assembly may cause the expandable distal end assembly to contract, tilt, and deform relative to the distal end of the shaft.

[0013] Therefore, when visual markings of the distal tip assembly are displayed in real time on the EA map, there may be a significant difference between the electrode position estimated based on the position and orientation of the magnetic sensor and the actual position of the electrode. However, it is clinically important to know the actual deflection of the distal tip assembly and the contact force on the distal tip assembly (e.g., to assess readiness for ablating tissue).

[0014] Examples of the present disclosure described herein provide a technique in which a processor estimates a contact force of an expandable distal tip assembly based on a change in a local estimate of a deflection of the expandable assembly. The disclosed technique involves sensing the relative position of one or more first position sensing elements at the distal end and at least a second position sensing element at the distal end of the shaft (or the proximal end of the expandable distal tip assembly).

[0015] In some exemplary embodiments, one or more first position sensing elements at the distal end of the distal tip assembly and at least one second position sensing element at the distal end of the shaft are electromagnetic coils (EMCs). Position sensing based on transmission between an EMC mounted on a catheter and an EMC embedded in a positioning pad is described in more detail herein.

[0016] In some example embodiments, one or more first position sensing elements at the distal end of the distal tip assembly and at least one second position sensing element at the distal end of the shaft are electrodes that sense position based on impedance tracking, as described in more detail herein. Other position sensing elements (also referred to as position sensors) are contemplated.

[0017] Using the expandable assembly and / or the calibrated elastic model, the processor estimates an amount of force exerted on the tissue by the expandable distal tip assembly from the change in shape and / or deflection.

[0018] In some example embodiments, the relative position is defined based on determining the position of each position sensor (or electrode) within a defined global coordinate system and determining the relative position. In other example embodiments, the relative position of each position sensor is based on measuring one or more position signals acquired in a local transmitter-receiver mode, which does not require first determining the position of each position sensor (or electrode) within a defined global coordinate system. Using the local signals, the processor calculates the relative position of the transmitting element and the receiving element, one of which is located on the axis and the other is located on the expandable component.

[0019] In some example embodiments, the processor uses a local transmitter-receiver mode by using a proximal and distal EMC, wherein the distal EMC is disposed on a distal portion of the expandable assembly and the proximal EMC is disposed on a distal end of the shaft. Typically, three distal EMCs may be used.

[0020] In the local transmitter-receiver mode, one EMC group (e.g., the distal EMC) transmits a magnetic field, and the other EMC (the proximal EMC) outputs an electrical signal in response to picking up the magnetic field. This local transmitter-receiver mode can produce a more accurate estimate of the deflection and shape change of the extendable distal tip assembly than an approach that requires first determining each position of each position sensor within a global coordinate system.

[0021] Based on the number of distal EMCs and / or their distribution on the expandable distal tip assembly, the disclosed technology can provide an accurate estimate of the contact force of the expandable distal tip assembly. For example, the processor can estimate the location where contact occurs on the lateral circumference of the expandable distal tip assembly by detecting the tilt direction of the expandable distal tip assembly. By detecting the deformation, the processor can estimate the location of the center of contact on the lateral circumference (e.g., whether the location is located on a portion closer to the shaft or at a more distal portion of the expandable distal tip assembly).

[0022] In one example, based on the magnetic field generated by the distal EMC and sensed by the proximal EMC, the processor determines the distance and angle between the two EMCs and converts the changes in the distance and angle values ​​from free space values ​​to contact forces exerted on the component.

[0023] The expandable distal end assembly is usually made of nitinol or some other material with elastic properties. Each of the splines of the expandable distal end assembly is an elastic beam, and since the splines are all connected at their proximal and distal ends, the expandable distal end assembly can be elastically modeled as a structure made of elastic beams. Therefore, the processor can derive the force applied to the expandable distal end assembly as an elastic element. When the simple spring model for the contraction and tilting of the expandable distal end assembly is too limited (for example, for some types of expandable distal end assemblies), the processor can use a more complex elastic model (for example, based on a set of springs or beams) for the deformation of the expandable distal end assembly. An example of a system and method for tracking the coordinates of an element (e.g., a spline portion, a sensor, an electrode) of an expandable distal end assembly in contact with tissue is described in U.S. Patent Application Publication 17 / 874,224 filed on July 26, 2022. Another example of such a system and method for tracking the coordinates of an element is described in U.S. Patent Application Publication 18 / 089,428 filed on December 27, 2022. A processor using these techniques is able to find the location of the electrodes in the deformed shape of the expandable distal tip assembly.

[0024] Additionally or alternatively, the processor can estimate the contact force using empirical data including calibrations for the force of deformation of the extendable distal end assembly. The processor can use weights to interpolate between calibration values. In this case, the memory of the system is configured to store the relationship between the EMC output and the contact force based on the empirical data (e.g., a lookup table). The processor is configured to associate the EMC output with the contact force using the stored empirical data.

[0025] In another example, the force on each spline (or each electrode) can be estimated based on modeling the shape of the expandable distal tip assembly for different calculated forces. The modeled forces on the splines can be compared to pre-measured values, and the comparison can then be used to calibrate the model with weights. (Such weights can also be a neural network model.)

[0026] In one example, the distal EMC is a magnetic single axis sensor (SAS) configured to generate at least one corresponding oscillating magnetic field signal. The distal end of the shaft includes a magnetic triaxial sensor (TAS) made of three mutually orthogonal EMCs, which is configured to output an electrical signal in response to receiving the magnetic field signal. In another example, the distal end of the shaft includes three EMCs that are parallel and displaced from each other on the shaft.

[0027] The distal EMC is configured to pick up the magnetic field generated by the localization mat, and the processor is configured to sample the resulting output and use it to determine the position of the distal coil in the 3D coordinate system. The TAS includes three mutually orthogonal EMCs configured to pick up the magnetic field generated by the localization mat, and the processor is configured to sample the resulting output and use it to determine the position and orientation of the shaft in the 3D coordinate system.

[0028] Any given frequency used for contact force detection is different from the frequency generated by the external positioning pad of the position tracking system used for position sensing.

[0029] In yet another example, the distal EMC (eg, SAS) is embedded in corresponding electrodes disposed on the splines of the expandable distal tip assembly.

[0030] System Description

[0031] Figure 1 is a schematic illustration of a catheter-based electroanatomical (EA) mapping and ablation system 10 according to an example of the present disclosure.

[0032] The system 10 includes one or more catheters that are inserted into the cavity or vascular structure of the heart 12 by a physician 24 through the patient's vascular system through the skin. Typically, the delivery sheath catheter is inserted into the left atrium or right atrium near the desired location in the heart 12. Then, one or more catheters can be inserted into the delivery sheath catheter in sequence to reach the desired location. The one or more catheters may include a catheter dedicated to sensing intracardiac electrogram (IEGM) signals, a catheter dedicated to ablation, and / or a catheter dedicated to both sensing and ablation. An exemplary basket-shaped catheter 14 configured for sensing IEGM is shown herein. As shown in inset 45, the physician 24 brings the basket-type expandable distal tip assembly 28 (hereinafter also referred to as "expandable distal tip assembly 28") mounted on the shaft 44 of the catheter 14 into contact with the heart wall to sense the target site in the heart 12. For ablation, the physician 24 similarly brings the distal end of the ablation catheter to the target site for ablation.

[0033] As shown in inset 65, catheter 14 is an exemplary catheter including one and preferably a plurality of electrodes 26, which are optionally distributed over a plurality of splines 22 at an expandable distal tip assembly 28 and are configured to sense IEGM signals. Catheter 14 additionally includes (i) a proximal position sensor 29 (e.g., a TAS 29 including three EMCs) embedded in the distal end 46 of the shaft 44 near the expandable distal tip assembly 28, and (ii) two distal position sensors 39 (e.g., a SAS 39 including a single EMC) to track the position of the distal end of the expandable distal tip assembly 28. Optionally and preferably, position sensors 29 and 39 are magnetic-based position sensors that include magnetic coils for sensing three-dimensional (3D) position.

[0034] The following Figure 2B and Figure 2C Two cases are shown where the EMC of the distal sensor 39 and the proximal sensor 29 are used together to estimate the contact force of the elastically expandable distal tip assembly with the tissue. Figure 2B In , the force is estimated from the retraction of the expandable distal tip assembly relative to the distal end of the shaft, while in Figure 2C In the present invention, the force is estimated from the tilt of the expandable distal tip assembly relative to the distal end of the shaft.

[0035] In the disclosed contact force estimation technique, the EMCs of distal sensor 39 and proximal sensor 29 operate in a transmitter-receiver mode, wherein one EMC (e.g., of sensor 39) transmits a magnetic field and the other EMC (e.g., of sensor 29) outputs an electrical signal in response to receiving the magnetic field. This transmitter-receiver mode used by the processor to estimate contact force produces more accurate position and orientation data than data produced by using an EMC with a magnetic field source external to the patient's body.

[0036] In addition, the magnetic position sensors (29, 39) can also operate with an external positioning pad 25, which includes a plurality of magnetic coils 32 configured to generate a magnetic field in a predefined workspace. The frequencies of these fields are different from any given frequency used in the local transmitter-receiver mode for contact force detection, thereby eliminating confusion between signals. Using operation with an external positioning pad 25 (at a different frequency for each EMC), the processor is able to determine the position of the EMC 39 on the coordinate system of the position tracking system.

[0037] The real-time orientation of the expandable distal tip assembly 28 of the catheter 14 can be calculated in this manner from the tracked positions of the sensors 29 and 39 (the positions are tracked using the magnetic field generated by the positioning pad 25 and sensed by the magnetic-based position sensors 29 and 39). The relative orientation is represented by the angle formed between the distal tip 46 and the longitudinal axis 42 (to the distal edge 16 of the assembly) of the expandable assembly 28. The distal end 46 of the shaft 44 may include an amplification circuit configured to amplify the outputs of the three EMCs from the sensor 29.

[0038] Details of magnetic-based position sensing technology are described in U.S. Patents 5,5391,199, 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, and 6,892,091.

[0039] The system 10 includes one or more electrode patches 38 positioned in contact with the skin of the patient 23 to establish a position reference for impedance-based tracking of the positioning pad 25 and the electrodes 26. For impedance-based tracking, current is directed toward the electrodes 26 and sensed at the electrode skin patches 38 so that the position of each electrode can be triangulated via the electrode patches 38. Details of impedance-based position tracking techniques are described in U.S. Patents 7,536,218, 7,756,576, 7,848,787, 7,869,865, and 8,456,182.

[0040] Recorder 11 displays electrograms 21 captured using surface ECG electrodes 18 and intracardiac electrograms (IEGMs) captured using electrodes 26 of catheter 14. Recorder 11 may include pacing capabilities for pacing the cardiac rhythm and / or may be electrically connected to a separate pacemaker.

[0041] The system 10 may include an ablation energy generator 50 adapted to conduct ablation energy to one or more electrodes at the distal tip of a catheter configured for ablation. The energy generated by the ablation energy generator 50 may include, but is not limited to, radio frequency (RF) energy or pulsed field ablation (PFA) energy (including monopolar or bipolar high voltage DC pulses that may be used to achieve irreversible electroporation (IRE)), or a combination thereof.

[0042] The patient interface unit (PIU) 30 is a controller with processing capabilities that is configured to establish electrical communications between catheters, electrophysiology equipment, a power source, and a workstation 55 for controlling the operation of the system 10. The electrophysiology equipment of the system 10 may include, for example, multiple catheters, positioning pads 25, surface ECG electrodes 18, electrode patches 38, ablation energy generator 50, and recorder 11. Optionally and preferably, the PIU 30 additionally includes processing capabilities for enabling real-time calculations of catheter position and for performing ECG calculations.

[0043] The workstation 55 includes a memory 57, a processor unit 56 having memory or storage loaded with appropriate operating software, and user interface capabilities. The workstation 55 can provide multiple functions, optionally including: (i) three-dimensional (3D) modeling of the endocardial anatomy and rendering the model or anatomical map 20 for display on the display device 27; (ii) displaying the activation sequence (or other data) compiled from the recorded electrograms 21 on the display device 27 as representative visual markers or images superimposed on the rendered anatomical map 20; (iii) displaying the real-time position and orientation of multiple catheters within the cardiac chamber; and (iv) displaying areas of interest (such as where ablation energy has been applied) on the display device 27. A commercial product embodying elements of the system 10, the commercial product being capable of being displayed in a CARTO TM The 3 system was purchased from Biosense Webster, Inc., 31A Technology Drive, Irvine, CA 92618.

[0044] Estimation of contact forces of expandable components of catheters

[0045] FIG. 2A to FIG. 2C Schematic illustrations of a catheter expandable distal tip assembly 281 (i) in free space, (ii) compressed against tissue 47, and (iii) tilted by contacting tissue 47, respectively, according to an embodiment of the present disclosure.

[0046] The expandable distal tip assembly 281 is formed by the spine 222 and includes two distal EMCs 239 and a TAS 229 including three mutually orthogonal EMCs. Figure 2A 2, the expandable distal tip assembly 281 is in free space and has a given first length 241. The transmitter-receiver layout 229 / 239 of FIG. 2 is only one of many more possible implementations of the disclosed transmitter-receiver configuration for contact force sensing. As another example, there may be three EMCs at the distal end of the catheter expandable distal tip assembly, while the shaft has only a dual-axis magnetic sensor (DAS).

[0047] exist Figure 2B4, once pressed against tissue 47 (e.g., where some of electrodes 226 are brought into firm contact with the wall tissue), the resiliently expandable distal tip assembly 281 contracts to a second shorter length 242. This situation may be typical in the context of a pulmonary vein isolation (PVI) procedure, where some of the distal electrodes 226 are used in this manner to electrically ablate a PV ostium in the left atrium to eliminate arrhythmias.

[0048] The transmitter-receiver mode of one of the EMC 239 and TAS 229 enables accurate determination of the amount D by which the expandable distal tip assembly is retracted. L (eg, length 241 minus length 242). Based on the known (eg, measured) spring constant K of the expandable distal tip assembly 281 L , contact force F C Can be from F C =K L ·D L estimate.

[0049] exist Figure 2C In the embodiment of the present invention, the expandable distal end assembly 281 is brought into contact with the side of the tissue 47. As a result, the expandable distal end assembly 281 is moved from its 0-angle orientation (eg, Figure 2A The distal end of the shaft 244 is inclined or bent at an angle β250 (the angle between the longitudinal axis 204 of the distal end of the shaft 244 and the axis 206 of the expandable distal end assembly). This situation may be typical in some cases where the electrode 226 is used to ablate the wall tissue of the ventricle to eliminate ventricular arrhythmias.

[0050] The transmitter-receiver mode of the EMC 239 and these of the TAS 229 enable accurate determination of the amount of inclination of the expandable distal tip assembly. β is based on the known (eg, measured) spring constant K of the expandable distal tip assembly 281 A , the measured or previously known distance L between the EMC 239 and the EMC of the sensor 229, and L (eg, the length 241), the contact force F A Can be from F A =K A ·L·β estimation.

[0051] As described above, when a simple spring model for the retraction and tilting of the expandable distal tip assembly is limited (e.g., for some types of expandable distal tip assemblies), the processor may use a more complex elastic model (e.g., based on a set of springs) for the expandable distal tip assembly deformation, such as Figure 3 as shown in .

[0052] Additionally or alternatively, the processor can estimate the contact force using empirical data including calibrations for forces that tilt and / or deform the extendable distal end assembly. The processor can interpolate between calibration values ​​using weights. In this case, the system's memory is configured to store the relationship between the EMC output and the contact force based on the empirical data. The processor is configured to associate the EMC output with the contact force using the stored empirical data.

[0053] Figure 3 is a schematic illustration of catheter expandable distal tip assembly 28 in a deformed shape when pressed against tissue 47 according to an example of the present disclosure.

[0054] As shown, the expandable distal tip assembly 28 forms an angle θ308 relative to the distal end 46 of the shaft 44. The angle 308 is defined between the longitudinal axis 307 of the expandable distal tip assembly 28 and the longitudinal axis 304 of the distal end 46. Using the EMC 39, the EMC of the TAS 29, and the known relationship between the distal edge 306 of the assembly and the distal end 46, the processor can easily calculate the angle θ308. The processor can calculate the amount of deflection of the distal edge 306 based on the tilt angle and the length of the expandable distal tip assembly (e.g., the length 241).

[0055] However, the shape followed by the splines 22 is unknown, although it is apparent that the splines 22 on the compressed side (L1) are compressed inwardly, while the splines 22 on the free side (e.g., in the blood pool of the cardiac chamber) are bent outwardly. To estimate the tilt, it is sufficient to know that the sensors 39 move together and have a small relative change between their movements due to deformation, and that this change can be accounted for to a large extent. As a result, the expandable distal tip assembly deformation does not cause any significant error in the estimated contact force.

[0056] If the smaller effects of deformation are of interest, analysis of the deformed shape can be accomplished using the aforementioned U.S. Patent Application Publication 18 / 089,428 by observing the frontal cross-sectional plane L1-L2 312 (e.g., the azimuthal plane). Since the splines 22 are elastic and continuous, the processor can reconstruct the entire expandable distal tip assembly shape by finding the spline positions 314 in one such plane.

[0057] Using a lookup table (eg, a lookup table stored in memory 57) of measured contact forces versus spline position values ​​in plane L1-L2 312, processor 56 is able to very accurately estimate (eg, interpolate) the actual contact forces inside the patient's body.

[0058] Method for estimating contact forces of expandable components of a catheter

[0059] Figure 4is a schematic diagram according to an example of the present disclosure showing an estimation such as FIG. 2 or Figure 3 Flow chart of a method for measuring contact force of an expandable distal tip assembly (e.g., basket-shaped expandable distal tip assembly 28 or 281) in contact with tissue. According to the example presented, the algorithm executes a process starting at an expandable distal tip assembly insertion step 402 with a physician 24 inserting an expandable distal tip assembly into a cavity (e.g., a cardiac cavity).

[0060] Next, at an assembly contacting step 404, the physician brings the expandable distal tip assembly into contact with cavity wall tissue (e.g., tissue 47), which causes the expandable distal tip assembly to change shape or orientation relative to the distal end of the shaft, such as Figure 2B , Figure 2C and Figure 3 as shown in .

[0061] At a signal acquisition step 406, the processor 56 receives position and / or orientation indicative signals acquired by an EMC implemented in a local transmitter-receiver mode as described above (eg, those of EMC 39 / 239 or TAS29 / 329).

[0062] In an assembly change estimation step 408, using the position and / or orientation indicative signals, the processor estimates an amount of change in the shape and / or orientation of the expandable distal tip assembly relative to the distal end of the shaft.

[0063] At a contact force estimation step 410, using an elastic model and / or empirical data (eg, a lookup table stored in memory 57), processor 56 correlates the variation to the contact force applied on the expandable distal tip assembly (eg, with the basket cage).

[0064] Finally, at a contact force display step 412, the processor provides an indication of the contact force (eg, the size and location on the expandable distal tip assembly) to the user on a display.

[0065] Figure 4 The flowchart shown is chosen purely for conceptual clarity. This example may also include additional steps of the algorithm, such as estimating the conductivity between a given electrode and tissue. This step and other possible steps are intentionally omitted from the disclosure herein in order to provide a more simplified flowchart.

[0066] It should be noted that although most examples have been described with reference to determining relative position using local transmitter-receiver patterns, the systems and methods described herein may alternatively and / or additionally determine relative position using position sensing by each position sensor (electrode) with reference to a global coordinate system.

[0067] Example

[0068] Example 1

[0069] A system (10) includes a medical probe (14) and a processor (56). The medical probe (14) includes (i) a shaft (44) for insertion into a cavity of an organ of a patient (23), (ii) an expandable assembly (28) mounted at a distal end (46) of the shaft (44), wherein the expandable assembly (28) has elastic properties, (iii) a proximal position sensing element (29) mounted on the distal end (46) of the shaft, and (iv) at least one distal position sensing element (39) located on the distal end of the expandable assembly (28). The processor (56) is configured to (I) sense a relative position of each of the at least one distal position sensing element (39) and the proximal position sensing element (29), (II) determine a deflection of the expandable assembly (28) based on the relative position, (III) associate the deflection with a contact force applied to the expandable assembly (28), and (IV) provide an indication of the contact force on a display (27).

[0070] Example 2

[0071] A system (10) as recited in Example 1, wherein each of the proximal position sensing element (29) and the at least one distal position sensing element (39) is an electromagnetic coil (EMC).

[0072] Example 3

[0073] The system (10) of embodiment 2, wherein the controller (30) is configured to apply a driving signal of a given frequency to one of the proximal EMC and the at least one distal EMC; and

[0074] The output at a given frequency is received and processed by the other of the proximal EMC and the at least one distal EMC to determine the relative position of each of the at least one distal position sensing element (39) and the proximal position sensing element (29).

[0075] Example 4

[0076] A system (10) according to embodiment 3, wherein each of the EMCs (29, 39) is configured to sense a magnetic field generated by a magnetic source (32) external to the patient and output a corresponding signal indicating a position in a 3D coordinate system of a position traction system, and wherein the drive signal has a frequency different from a frequency used by the magnetic source external to the patient (23).

[0077] Example 5

[0078] A system (10) according to any one of embodiments 3 to 4, and comprising an amplification circuit mounted on the catheter, the circuit being configured to amplify the output at the given frequency through the other of the proximal EMC and the at least one distal EMC.

[0079] Example 6

[0080] A system (10) according to any one of Examples 2 to 5, wherein the distal end (46) of the shaft (44) includes three EMCs (29), the three EMCs (29) being oriented non-parallel with respect to each other, and wherein the processor is configured to detect at least one of axial compression of the expandable component (28) and angular deflection of the expandable component (28) relative to the distal end (46) of the shaft (44) by processing outputs from the three EMCs.

[0081] Example 7

[0082] A system (10) according to any one of embodiments 2 to 6, wherein the at least one distal EMC (39) is embedded in a corresponding electrode (26) disposed on the spline (22).

[0083] Example 8

[0084] A system (10) according to any one of embodiments 2 to 7, wherein the distal end (46) of the shaft (44) includes at least two EMCs (29), and the at least two EMCs (29) are parallel and displaced from each other on the shaft (44).

[0085] Example 9

[0086] A system (10) according to any one of embodiments 1 to 8, and the system includes a memory (57), the memory being configured to store the relationship between the output of the position sensing element (29, 39) and the contact force based on empirical data, and wherein the processor (56) is configured to use the empirical data to associate the position sensing element output with the contact force.

[0087] Example 10

[0088] A system (10) according to any one of embodiments 1 to 9, wherein the expandable component (28) is a basket component formed with a plurality of splines (22).

[0089] Embodiment 11

[0090] A method includes inserting a shaft (44) of a medical probe (14) into a cavity of an organ of a patient (23), the probe comprising (i) an expandable assembly (28) mounted at a distal end (46) of the shaft, wherein the expandable assembly (28) has elastic properties, (ii) a proximal position sensing element (29) mounted on the distal end of the shaft, and (iii) at least one distal position sensing element (39) located on the distal end of the expandable assembly (28). A relative position of each of the at least one distal position sensing element (39) and the proximal position sensing element (29) is sensed. A deflection of the expandable assembly (28) is determined based on the relative position. The deflection is associated with the contact force applied to the expandable assembly (28). An indication of the contact force is provided on a display (27).

[0091] Although the examples described herein are primarily directed to cardiac diagnostic applications, the methods and systems described herein can also be used in other medical applications.

[0092] It should be understood that the above examples are cited by way of example, and the present disclosure is not limited to what is specifically shown and described above. On the contrary, the scope of the present disclosure includes combinations and sub-combinations of the various features described above, as well as variations and modifications thereof, which will occur to those skilled in the art upon reading the above description and which are not disclosed in the prior art.

Claims

1. A system, comprising: A medical probe, comprising: a shaft for insertion into a cavity of an organ of a patient; an expandable component mounted at the distal end of the shaft, wherein the expandable component has elastic properties; a position sensing element mounted on the distal end of the shaft; and at least one distal position sensing element located on a distal end of the expandable assembly; and A processor, the processor being configured to: sensing a relative position of each of the at least one distal position sensing element and the proximal position sensing element; determining a deflection of the expandable assembly based on the relative position; correlating the deflection to a contact force exerted on the expandable assembly; and An indication of the contact force is provided on a display. 2 . The system of claim 1 , wherein each of the proximal position sensing element and the at least one distal position sensing element is an electromagnetic coil (EMC).

3. The system of claim 2, wherein the controller is configured to: applying a driving signal of a given frequency to one of the proximal EMC and the at least one distal EMC; and The output at the given frequency is received and processed by the proximal EMC and the other of the at least one distal EMC to determine the relative position of each of the at least one distal position sensing element and the proximal position sensing element, wherein each of the EMCs is configured to sense a magnetic field generated by a magnetic source external to the patient and output a corresponding signal indicating a position in a 3D coordinate system of a position traction system, and wherein the drive signal has a frequency different from a frequency used by the magnetic source external to the patient.

4. A system according to claim 3, and comprising an amplification circuit mounted on the catheter, the circuit being configured to amplify the output at the given frequency through the other of the proximal EMC and the at least one distal EMC.

5. A system according to claim 2 or claim 3, wherein the distal end of the shaft includes three EMCs, one EMC of the three EMCs is oriented non-parallel with respect to the other EMCs, and wherein the processor is configured to detect at least one of axial compression of the expandable component and angular deflection of the expandable component relative to the distal end of the shaft by processing outputs from the three EMCs.

6. The system of claim 2 or claim 3, wherein the at least one distal EMC is embedded in a corresponding electrode disposed on the spline.

7. A system according to claim 2 or claim 3, wherein the distal end (46) of the shaft (44) comprises at least two EMCs (29), which are parallel and displaced from each other on the shaft (44).

8. A system according to any one of claims 1 to 3, and the system includes a memory, the memory being configured to store the relationship between the position sensing element output and the contact force based on empirical data, and wherein the processor is configured to use the empirical data to associate the position sensing element output with the contact force.

9. The system of any one of claims 1 to 3, wherein the expandable component is a basket-like component formed with a plurality of splines.

10. A method comprising: A medical probe is provided, the probe comprising (i) an expandable assembly mounted at a distal end of a shaft, wherein the expandable assembly has elastic properties, (ii) a position sensing element mounted on the distal end of the shaft, and (iii) at least one distal position sensing element located on the distal end of the expandable assembly; sensing a relative position of each of the at least one distal position sensing element and the proximal position sensing element; determining a deflection of the expandable assembly based on the relative position; correlating the deflection to a contact force exerted on the expandable component; as well as An indication of the contact force is provided on a display.

11. The method of claim 10, wherein each of the proximal position sensing element and the at least one distal position sensing element is an electromagnetic coil (EMC); and the method further comprises applying a driving signal of a given frequency to one of the proximal EMC and the at least one distal EMC; and The output at the given frequency is received and processed by the other of the proximal EMC and the at least one distal EMC to determine a relative position of each of the at least one distal position sensing element and the proximal position sensing element.

12. A method according to claim 11, wherein each of the EMCs is configured to sense a magnetic field generated by a magnetic source external to the patient and output a corresponding signal indicating a position in a 3D coordinate system of a position traction system, and wherein the drive signal has a frequency different from a frequency used by the magnetic source external to the patient.

13. A method according to claim 11 or claim 12 and comprising amplifying the outputs from three EMCs using amplification circuitry mounted on the conduit.

14. A method according to claim 11 or claim 12, wherein the distal end of the shaft includes three EMCs, one EMC of the three EMCs is oriented non-parallel with respect to the other EMCs, and wherein the processor is configured to detect at least one of axial compression of the expandable component and angular deflection of the expandable component relative to the distal end of the shaft by processing outputs from the three EMCs.

15. A method according to claim 11 or claim 12, and comprising storing the relationship between EMC output and contact force based on empirical data, and using the empirical data to relate the EMC output to the contact force.

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