Estimation of contact force of expandable assembly of catheter

Abstract

To detect contact force of a cardiac catheter.SOLUTION: A system of the present invention includes a medical probe and a processor. The medical probe includes a shaft to be inserted into the cavity of an organ of a patient, an expandable assembly having elasticity, which is attached to the distal end of the shaft, a position sensing element attached to the distal end of the shaft, and at least one distal position sensing element on the distal end of the expandable assembly. The processor senses each relative position of the at least one distal position sensing element and a proximal position sensing element, determines the deflection of the expandable assembly on the basis of the relative position, associates the deflection with contact force applied to the expandable assembly, and displays the contact force on a display.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates generally to invasive medical probes, and more particularly to detecting contact force in cardiac catheters. [Background technology]

[0002] A cardiac catheter typically comprises an elongate shaft for insertion into a patient's body and a distal end that includes one or more electrodes and / or sensors. The catheter may further comprise a magnetic position sensor attached to the distal end of the shaft.

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

[0004] It is also known to sense the contact force applied to the distal tip. One method of estimating the contact force of a distal tip assembly is described in U.S. Pat. No. 8,535,308. This patent describes a spring-loaded connection that couples the distal tip to the distal end of the shaft. A connection sensor contained within the catheter senses the position of the distal tip relative to the distal end of the shaft. The connection sensor includes first and second subassemblies disposed within the catheter on opposite sides of the connection, each subassembly including one or more magnetic transducers. Deflection is estimated from the relative positions of the subassemblies based on position signals emitted and received by the subassemblies. The tip contact force is estimated from the deflection based on a known spring constant of the connection.

[0005] A more complete understanding of the present disclosure will be obtained from the following detailed description of the embodiments of the present disclosure when read in conjunction with the drawings. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic, pictorial illustration of a catheter-based electroanatomical (EA) mapping and ablation system, according to one embodiment of the present disclosure. [Figure 2A] 1A-1C are schematic depictions of a catheter expandable distal end assembly (i) in free space, (ii) compressed against tissue, and (iii) tilted by contacting tissue, respectively, in accordance with an embodiment of the present disclosure. [Figure 2B] 1A-1C are schematic depictions of a catheter expandable distal end assembly (i) in free space, (ii) compressed against tissue, and (iii) tilted by contacting tissue, respectively, in accordance with an embodiment of the present disclosure. [Figure 2C] 1A-1C are schematic depictions of a catheter expandable distal end assembly (i) in free space, (ii) compressed against tissue, and (iii) tilted by contacting tissue, respectively, in accordance with an embodiment of the present disclosure. [Diagram 3] 1 is a schematic, pictorial illustration of a catheter expandable distal end assembly in a deformed shape when pressed against tissue, according to an embodiment of the present disclosure. FIG. [Figure 4] 4 is a flow chart that generally illustrates a method for estimating a contact force of an expandable distal end assembly, such as that of FIG. 2 or 3, in contact with tissue, according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] overview A catheter having multiple electrodes attached to its expandable distal end assembly can be used to map and / or ablate a wall cavity of a patient's organ, such as a heart chamber. The expandable distal end assembly is coupled to a distal end of a catheter shaft for insertion into the cavity. The expandable distal end assembly may be shaped in the form of a balloon, basket, and / or another type of cage, and may include multiple electrodes configured for sensing and / or delivering therapeutic signals. The expandable distal end assembly has multiple splines coupled at their proximal and distal ends. When expanded, the splines bend radially outward. When collapsed, the splines are generally disposed along the axis of the shaft. Electrodes and / or sensors may be disposed on the splines and / or on the membrane of the balloon for a balloon distal end. The expandable distal end assembly may also be referred to herein as an expandable assembly.

[0008] In a ventricular mapping and / or ablation procedure, a physician expands the assembly and manipulates the expanded distal tip assembly so that the electrodes contact the ventricular wall. The quality of electroanatomical mapping and / or ablation (e.g., based on depolarization signals acquired by the electrodes) depends on the contact force of the electrodes with the wall tissue. Estimation of such forces on the shaft can be difficult because the elasticity of the expandable distal tip assembly can cause contraction, tilting, and deformation of the expandable distal tip assembly relative to the distal end of the shaft.

[0009] Thus, when displaying a visual indication of the distal tip assembly on the EA map in real time, there may be a significant discrepancy between the estimated electrode position based on the position and orientation of the magnetic sensors and the actual position of the electrode. However, knowing the actual deflection of the distal tip assembly and the contact force on the distal tip assembly is clinically important (e.g., to assess the readiness to ablate tissue).

[0010] Examples of the disclosure described herein provide techniques for a processor to estimate a contact force of an expandable distal tip assembly based on locally estimating a change in deflection of the expandable assembly. The disclosed techniques involve sensing the relative position of one or more first position sensing elements at the distal tip and at least a second position sensing element at the distal end of the shaft (or at the proximal end of the expandable distal tip assembly).

[0011] In some exemplary embodiments, the one or more first position sensing elements at the distal end of the distal tip assembly and the 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 attached to the catheter and an EMC embedded in a location pad is described in more detail herein.

[0012] In some exemplary embodiments, the 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 tracing, as described in more detail herein. Other position sensing elements (also referred to as position sensors) may be contemplated.

[0013] Using an elastic model and / or calibration of the expandable assembly, the processor estimates the amount of force exerted by the expandable distal end assembly on tissue from the change in shape and / or deflection.

[0014] In some exemplary embodiments, the relative position is defined based on determining the position of each position sensor (or electrode) in a defined global coordinate system and determining the relative position. In other exemplary embodiments, the relative position of each position sensor is based on measuring one or more position signals obtained in a local transmitter-receiver mode, which does not require first determining the position of each position sensor (or electrode) in a defined global coordinate system. Using the local signals, the processor calculates the relative position of the transmitting element with respect to the receiving element, one on the shaft and the other on the expandable assembly.

[0015] In some exemplary embodiments, the processor uses a local transmitter-receiver mode by using a proximal and a distal EMC, the distal EMC being located on a distal portion of the expandable assembly and the proximal EMC being located on a distal end of the shaft. Typically, three distal EMCs may be used.

[0016] In a local transmitter-receiver mode, one EMC group (e.g., distal EMC(s)) emits a magnetic field and the other EMC (proximal EMC(s)) outputs an electrical signal in response to picking up the magnetic field. This local transmitter-receiver mode can result in more accurate estimation of deflection and shape changes of the expandable distal tip assembly compared to methods that require first determining each position of each position sensor in a global coordinate system.

[0017] Depending on the number of distal EMCs and / or their distribution across the expandable distal end assembly, the disclosed techniques can provide accurate estimation of the contact force of the expandable distal end assembly. For example, the processor can estimate where the contact occurs on the lateral circumference of the expandable distal end assembly by detecting the tilt orientation of the expandable distal end 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 on a portion closer to the shaft or on a more distal portion of the expandable distal end assembly).

[0018] In one embodiment, 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 change in distance and angle values ​​from free space values ​​to a contact force exerted on the assembly.

[0019] The expandable distal end assembly is typically made of Nitinol or some other material with elastic properties. Since each of the splines of the expandable distal end assembly is an elastic beam and 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. Thus, the processor can estimate the force applied to the expandable distal end assembly as an elastic element. If a simple spring model for the contraction and tilt of the expandable distal end assembly is too limited (e.g., for some types of expandable distal end assemblies), the processor may use a more complex elastic model (e.g., 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 the elements (e.g., spline portions, sensors, electrodes) of the expandable distal end assembly in contact with tissue is described in U.S. Patent Application Publication No. 17 / 874,224, filed July 26, 2022. Another example of such a system and method for tracking element coordinates is described in U.S. Patent Application Publication No. 18 / 089,428, filed December 27, 2022. A processor using these techniques can locate the position of the electrodes under the deformed shape of the expandable distal tip assembly.

[0020] Additionally or alternatively, the processor can estimate the contact force using empirical data, including a calibration of force versus expandable distal tip assembly deformation. The processor can use weights to interpolate between the calibration values. In such a case, the system's memory is configured to store a relationship between the EMC output and the contact force based on the empirical data (e.g., a look-up table). The processor is configured to relate the EMC output to the contact force using the stored empirical data.

[0021] In another embodiment, 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 may be for a neural network model.)

[0022] In one example, the distal EMC is a magnetic single-axis sensor (SAS) configured to generate at least one respective oscillating magnetic field signal. The distal end of the shaft includes a magnetic triaxial sensor (TAS) consisting of three mutually orthogonal TASs, the TASs configured to output electrical signals in response to receiving the magnetic field signals. In another example, the distal end of the shaft includes three EMCs that are parallel and displaced from one another on the shaft.

[0023] The distal EMC is configured to pick up the magnetic fields generated by the location pads, and the processor is configured to sample the resulting output and use it to determine the position of the distal coil in a 3D coordinate system. The TAS comprises three mutually orthogonal EMCs configured to pick up the magnetic fields generated by the location pads, 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.

[0024] Any given frequency used for contact force detection is different from the frequency produced by the external location pads of the position tracking system for position sensing.

[0025] In yet another example, a distal EMC (eg, SAS) is embedded into each electrode disposed on the splines of the expandable distal tip assembly.

[0026] System Description FIG. 1 is a schematic, pictorial illustration of a catheter-based electroanatomical (EA) mapping and ablation system 10, according to one embodiment of the present disclosure.

[0027] The system 10 includes one or more catheters that are percutaneously inserted by a physician 24 through a patient's vascular system into a heart chamber or vascular structure of the heart 12. Typically, a delivery sheath catheter is inserted into the left or right atrium near a desired location of the heart 12. One or more catheters can then be inserted into the delivery sheath catheter to reach the desired location. The one or more catheters may include catheters dedicated to sensing Intracardiac Electrogram (IEGM) signals, catheters dedicated to ablation, and / or catheters dedicated to both sensing and ablation. An exemplary basket catheter 14 configured to sense IEGMs is shown herein. As seen in inset 45, the physician 24 brings a basket-type expandable distal end assembly 28 (hereinafter also referred to as "expandable distal end assembly 28") attached to a shaft 44 of the catheter 14 into contact with the heart wall to sense a target site within the heart 12. For ablation, the physician 24 similarly brings a distal end of an ablation catheter to a target site for ablation.

[0028] As seen in inset 65, catheter 14 is an exemplary catheter including one, and preferably multiple, electrodes 26, optionally distributed across multiple splines 22 in expandable distal tip assembly 28, and configured to sense IEGM signals. Catheter 14 further includes (i) a proximal position sensor 29 (e.g., TAS 29 with three EMCs) embedded in the distal end 46 of shaft 44 near expandable distal tip assembly 28, and (ii) two distal position sensors 39 (e.g., SAS 39 with a single EMC) for tracking the position of the distal end of expandable distal tip assembly 28. Optionally and preferably, position sensors 29 and 39 are magnetic-based position sensors including magnetic coils for sensing three-dimensional (3D) position.

[0029] Figures 2B and 2C below show two scenarios 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 tissue. In Figure 2B, the force is estimated from the contraction of the expandable distal tip assembly relative to the distal end of the shaft, and in Figure 2C, the force is estimated from the tilt of the expandable distal tip assembly relative to the distal end of the shaft.

[0030] In the disclosed contact force estimation technique, the EMCs of the distal sensor 39 and the proximal sensor 29 are operated in a transmitter-receiver mode, where one EMC (e.g., of sensor 39) emits 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 location and orientation data than that produced by using the EMCs with a magnetic field source external to the patient's body.

[0031] Additionally, the magnetic-based position sensor (29, 39) may operate with an external location pad 25 that includes multiple magnetic coils 32 configured to generate a magnetic field within a predetermined working volume. The frequencies of these fields are different from any given frequency used in a local transmitter-receiver mode for contact force detection, thus eliminating confusion between signals. Using operation with the external location pad 25 (at different frequencies for each EMC), the processor can determine the location of the EMC 39 on the coordinate system of the position tracking system.

[0032] The real-time orientation of the expandable distal tip assembly 28 of the catheter 14 is thus calculated from the tracked locations of the sensors 29 and 39 (locations are tracked using magnetic fields generated with the location pad 25 and sensed by the magnetic-based position sensors 29 and 39). This relative orientation is manifested by the angle formed between the distal tip 46 and the longitudinal axis 42 of the expandable assembly 28 (leading to the distal edge 16 of the assembly). The distal end 46 of the shaft 44 may include an amplification circuit configured to amplify the output from the three EMCs of the sensors 29.

[0033] Further details of magnetic based position sensing technology are described in U.S. Patent Nos. 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.

[0034] The system 10 includes one or more electrode patches 38 positioned for skin contact on the patient 23 to establish a positional reference for the location pads 25 and impedance-based tracking of the electrodes 26. For impedance-based tracking, a current is directed to the electrodes 26 and sensed at the electrode skin patch 38, so that the location of each electrode can be triangulated via the electrode patch 38. Details of impedance-based position tracking technology are described in U.S. Patent Nos. 7,536,218, 7,756,576, 7,848,787, 7,869,865, and 8,456,182.

[0035] Recorder 11 displays electrograms 21 captured by the body surface ECG electrodes 18 and intracardiac electrograms (IEGMs) captured by electrodes 26 of catheter 14. Recorder 11 may include pacing capability for pacing the cardiac rhythm and / or may be electrically connected to a stand-alone pacer.

[0036] The system 10 may include an ablation energy generator 50 adapted to deliver 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 unipolar or bipolar high voltage direct current pulses such as may be used to effect irreversible electroporation (IRE), or a combination thereof.

[0037] The patient interface unit (PIU) 30 is a controller with processing capabilities configured to establish electrical communications between the catheters, electrophysiological equipment, a power source, and a workstation 55 that controls the operation of the system 10. The electrophysiological equipment of the system 10 may include, for example, a number of catheters, location pads 25, body surface ECG electrodes 18, electrode patches 38, an ablation energy generator 50, and a recorder 11. Optionally and preferably, the PIU 30 additionally includes processing capabilities for performing real-time calculations of catheter position and executing ECG calculations.

[0038] The workstation 55 includes a processor unit 56 having a memory 57, a memory or storage device loaded with suitable operating software, and a user interface function. The workstation 55 may optionally provide multiple functions, including (i) modeling the endocardial anatomical structures in three-dimension (3D) and rendering the model or anatomical map 20 for display on the display device 27, (ii) displaying activation sequences (or other data) compiled from recorded electrograms 21 in a representative visual display or image superimposed on the rendered anatomical map 20 on the display device 27, (iii) displaying real-time positions and orientations of multiple catheters within the cardiac chambers, and (iv) displaying sites of interest, such as locations where ablation energy has been applied, on the display device 27. One commercially available product embodying elements of the system 10 is available as the CARTO™ 3 system, commercially available from Biosense Webster, Inc. 31A Technology Drive, Irvine, Calif., 92618.

[0039] Estimation of Contact Forces in Catheter Expandable Assemblies 2A-2C are schematic depictions of a catheter expandable distal end assembly 281 (i) in free space, (ii) compressed against tissue 47, and (iii) tilted by contacting tissue 47, respectively, in accordance with an embodiment of the present disclosure.

[0040] The expandable distal end assembly 281 is formed by the spine 222 and comprises two distal EMCs 239 and a TAS 229 with three mutually orthogonal EMCs. In FIG. 2A, the expandable distal end assembly 281 is in free space and has a given first length 241. The transmitter-receiver layout 229 / 239 in FIG. 2 is only one of many possible realizations 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 end assembly while the shaft has only a dual-axis magnetic sensor (DAS).

[0041] 2B, once pressed against tissue 47 (e.g., several of the electrodes 226 are brought into firm contact with wall tissue), the elastically expandable distal end assembly 281 retracts to a second, shorter length 242. Such a scenario may be typical for a pulmonary vein isolation (PVI) procedure, where several distal electrodes 226 are used in this manner to electrically ablate the ostia of the PVs in the left atrium and eliminate arrhythmias.

[0042] The transmitter-receiver mode of one of the EMC239 and TAS229 is the extendable distal end assembly retracted D L (e.g., length 241 minus length 242). A known (e.g., measured) spring constant K of the expandable distal end assembly 281 L Based on the contact force F C F C =K L D L can be estimated from

[0043] In Figure 2C, the expandable distal end assembly 281 is brought into lateral contact with tissue 47. As a result, the expandable distal end assembly 281 is tilted or bent from its zero angle orientation (as seen in Figure 2A) to an angle β 250 (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). Such a scenario may be typical when several electrodes 226 are used to ablate ventricular wall tissue to eliminate ventricular arrhythmias.

[0044] The transmitter-receiver mode of EMC 239 and that of TAS 229 allow for an accurate determination of the amount of tilt β of the expandable distal tip assembly. A , the measured or known distance L between the EMC 239 and the EMC of the sensor 229, and L (e.g., length 241), the contact force F A F A =K A can be estimated from L β.

[0045] As described above, if a simple spring model for contraction and tilting of the expandable distal end assembly is limited (e.g., for some types of expandable distal end assemblies), the processor may use a more complex elastic model (e.g., based on a set of springs) for deformation of the expandable distal end assembly, as seen in FIG. 3.

[0046] Additionally or alternatively, the processor can estimate the contact force using empirical data, including a calibration of forces for expandable distal tip assembly tilt and / or deformation. The processor can use weights to interpolate between the calibration values. In such a case, the memory of the system is configured to store a relationship between the EMC output and the contact force based on the empirical data. The processor is configured to relate the EMC output to the contact force using the stored empirical data.

[0047] FIG. 3 is a schematic, pictorial illustration of a catheter expandable distal end assembly 28 in a deformed shape when pressed against tissue 47, according to an embodiment of the present disclosure.

[0048] As shown, the expandable distal tip assembly 28 forms an angle θ 308 with respect to the distal end 46 of the shaft 44. The angle 308 is defined between a longitudinal axis 307 of the expandable distal tip assembly and a 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 readily calculate the angle θ 308. The processor can calculate the amount of deflection of the distal edge 306 based on the tilt angle and the length (e.g., length 241) of the expandable distal tip assembly.

[0049] However, it is clear that the splines 22 on the pressed side (L1) are compressed inwards while the splines 22 on the free side (e.g., in the ventricular blood pool) are bent outwards, but the shape that the splines 22 follow is unknown. To estimate the tilt, it is sufficient to know that the sensors 39 move with a small relative change between their movements due to deformation, and this change can be mainly taken into account. As a result, the deformation of the expandable distal end assembly does not cause any significant error in the estimated contact force.

[0050] If smaller deformation effects are important, analysis of the deformed shape can be performed using the aforementioned U.S. Patent Application Publication No. 18 / 089,428 by looking at the frontal cross sections L1-L2 312 (e.g., azimuthal planes). Because the splines 22 are elastic and continuous, the processor can reconstruct the entire expandable distal end assembly shape by finding the spline locations 314 in one such plane.

[0051] Using a look-up table of measured contact forces versus spline position values ​​in surface L1-L2 312 (e.g., a look-up table stored in memory 57), processor 56 can estimate (e.g., interpolate) with great accuracy the actual contact forces within the patient's body.

[0052] Method for estimating contact forces in catheter expandable assemblies 4 is a flow chart that generally illustrates a method for estimating the contact force of an expandable distal end assembly (e.g., basket expandable distal end assembly 28 or 281) such as of FIG. 2 or 3 in contact with tissue, according to an embodiment of the present disclosure. The algorithm according to the presented embodiment performs a process that begins with the physician 24 inserting the expandable distal end assembly into a cavity (e.g., a cardiac chamber) at expandable distal end assembly insertion step 402.

[0053] Next, in an assembly contact step 404, the physician contacts the expandable distal end assembly with cavity wall tissue (e.g., tissue 47), which causes the expandable distal end assembly to change shape or orientation relative to the distal end of the shaft, as seen in Figures 2B, 2C, and 3.

[0054] In a signal acquisition step 406, the processor 56 receives a signal indicative of position and / or orientation acquired by an EMC (eg, an EMC39 / 239 or TAS29 / 329) implemented in a local transmitter-receiver mode as described above.

[0055] Using the signals indicative of position and / or orientation, the processor estimates the amount of change in shape and / or orientation of the expandable distal tip assembly relative to the distal end of the shaft in an assembly change estimation step 408 .

[0056] In a contact force estimation step 410, using an elastic model and / or empirical data (e.g., a look-up table stored in memory 57), the processor 56 relates the amount of change to the contact force applied to the expandable distal end assembly (e.g., to a basket-type cage).

[0057] Finally, the processor provides an indication of the contact force (eg, size and location on the expandable distal tip assembly) to the user on the display in a contact force display step 412.

[0058] The flowchart shown in Figure 4 has been chosen solely for the purposes of conceptual clarity. This embodiment may also include additional steps in the algorithm, such as estimating electrical conductivity between a given electrode and tissue. This step, and other possible steps, have been intentionally omitted from the disclosure herein in order to provide a more simplified flowchart.

[0059] It should be noted that while most of the embodiments are described with respect to determining relative position using a local transmitter-receiver mode, the systems and methods described herein may alternatively and / or additionally determine relative position using position sensing of each position sensor (electrode) with reference to a global coordinate system. EXAMPLES

[0060] Example 1 The 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) attached to a distal end (46) of the shaft (44) and having elastic properties, (iii) a proximal position sensing element (29) mounted to the distal end (46) of the shaft, and (iv) at least one distal position sensing element (39) 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 positions, (III) relate the deflection to a contact force applied to the expandable assembly (28), and (IV) provide an indication of the contact force on a display (27).

[0061] Example 2 The system (10) of 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).

[0062] Example 3 A controller (30) applies a drive signal of a given frequency to one of the proximal EMC and the at least one distal EMC; A system (10) as described in Example 2, configured to receive and process output at a given frequency 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 (39) and the proximal position sensing element (29).

[0063] Example 4 A system (10) as described in Example 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 to output a respective signal indicative of a position in a 3D coordinate system of the position traction system, and the drive signal has a frequency different from the frequency used by the magnetic source external to the patient (23).

[0064] Example 5 The system (10) of any one of Examples 3 to 4, further comprising an amplifier circuit attached to the catheter, the circuit being configured to amplify the output at a given frequency by the other of the proximal EMC and the at least one distal EMC.

[0065] Example 6 A system (10) as described in any one of Examples 2 to 5, wherein the distal end (46) of the shaft (44) includes three EMCs (29) oriented non-parallel to one another, and the processor is configured to detect at least one of axial compression of the expandable assembly (28) and angular deflection of the expandable assembly (28) relative to the distal end (46) of the shaft (44) by processing output from the three EMCs.

[0066] Example 7 The system (10) of any one of Examples 2 to 6, wherein at least one distal EMC (39) is embedded within each electrode (26) disposed on the spline (22).

[0067] Example 8 A system (10) as described in any of Examples 2 to 7, wherein the distal end (46) of the shaft (44) is provided with at least two EMCs (29) that are parallel to and offset from each other on the shaft (44).

[0068] Example 9 A system (10) as described in any one of Examples 1 to 8, comprising a memory (57) configured to store a relationship between the position sensing element (29, 39) output and the contact force based on empirical data, and a processor (56) configured to correlate the position sensing element output to the contact force using the empirical data.

[0069] Example 10 The system (10) of any one of Examples 1 to 9, wherein the expandable assembly (28) is a basket assembly formed with a plurality of splines (22).

[0070] Example 11 The 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) attached to a distal end (46) of the shaft and having elastic properties, (ii) a proximal position sensing element (29) mounted to the distal end of the shaft, and (iii) at least one distal position sensing element (39) 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 positions. The deflection is related to a contact force applied to the expandable assembly (28). An indication of the contact force is provided on a display (27).

[0071] Although the embodiments described herein primarily address cardiac diagnostic applications, the methods and systems described herein may also be used in other medical applications.

[0072] It will be understood that the above described embodiments are given by way of example, and that the present disclosure is not limited to what is particularly shown and described hereinabove. Rather, the scope of the present disclosure includes both combinations and subcombinations of the various features described above, as well as variations and modifications thereof that would occur to one skilled in the art upon reading the foregoing description and that are not disclosed in the prior art.

[0073] [Embodiment] (1) A system comprising: 1. A medical probe, comprising: a shaft for insertion into a cavity of a patient's organ; an expandable assembly attached to a distal end of the shaft and having elastic properties; a position sensing element mounted to the distal end of the shaft; at least one distal position sensing element on a distal end of the expandable assembly; 1. A processor comprising: 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; relating the deflection to a contact force applied to the expandable assembly; a processor configured to provide an indication of the contact force on a display; A system comprising: (2) The system of embodiment 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 controller: applying a drive signal of a given frequency to one of the proximal EMC and the at least one distal EMC; The system of embodiment 2, configured to receive and process output at the given frequency 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 and the proximal position sensing element. (4) The system of embodiment 3, wherein each of the EMCs is configured to sense a magnetic field generated by a magnetic source external to the patient and output a respective signal indicative of a position in a 3D coordinate system of a position traction system, and the drive signal has a frequency different from a frequency used by the magnetic source external to the patient. (5) The system of embodiment 3, further comprising an amplifier circuit attached to the catheter, the circuit configured to amplify the output at the given frequency by the other of the proximal EMC and the at least one distal EMC.

[0074] (6) The system of embodiment 2, wherein the distal end of the shaft includes three EMCs oriented non-parallel to one another, and the processor is configured to detect at least one of axial compression of the expandable assembly and angular deflection of the expandable assembly relative to the distal end of the shaft by processing output from the three EMCs. (7) The system of embodiment 2, wherein the at least one distal EMC is embedded within each electrode arranged on the spline. (8) The system of embodiment 2, wherein the distal end (46) of the shaft (44) is provided with at least two EMCs (29) that are parallel to and offset from one another on the shaft (44). (9) The system of embodiment 1, further comprising a memory configured to store a relationship between the position sensing element output and the contact force based on empirical data, and the processor configured to use the empirical data to correlate the position sensing element output to the contact force. (10) The system of embodiment 1, wherein the expandable assembly is a basket assembly formed with a plurality of splines.

[0075] (11) A method comprising the steps of: Inserting a shaft of a medical probe into a cavity of a patient's organ, the probe comprising: (i) an expandable assembly attached to a distal end of the shaft and having elastic properties; (ii) a position sensing element mounted to the distal end of the shaft; and (iii) at least one distal position sensing element 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; and correlating the deflection to a contact force applied to the expandable assembly; providing an indication of said contact force on a display; and The method includes: (12) The method of embodiment 11, wherein each of the proximal position sensing element and the at least one distal position sensing element is an electromagnetic coil (EMC). (13) applying a drive signal of a given frequency to one of the proximal EMC and the at least one distal EMC; 13. The method of claim 12, further comprising receiving and processing an output at the given frequency 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. (14) The method of embodiment 13, wherein each of the EMCs is configured to sense a magnetic field generated by a magnetic source external to the patient and output a respective signal indicative of a position in a 3D coordinate system of a position traction system, and the drive signal has a frequency different from a frequency used by the magnetic source external to the patient. (15) The method of embodiment 13, comprising amplifying the output from the three EMCs using an amplifier circuit attached to the catheter.

[0076] (16) The method of embodiment 12, wherein the distal end of the shaft includes three EMCs oriented non-parallel to one another, and the processor is configured to detect at least one of axial compression of the expandable assembly and angular deflection of the expandable assembly relative to the distal end of the shaft by processing outputs from the three EMCs. (17) The method of embodiment 12, wherein the at least one distal EMC is embedded within each electrode arranged on a spline. (18) The method of claim 12, comprising storing a relationship between EMC output and contact force based on empirical data, and relating the EMC output to the contact force using the empirical data. (19) The method of embodiment 12, wherein the expandable assembly is a basket assembly formed with a plurality of splines.

Claims

1. 1. A system comprising:

1. A medical probe, comprising: a shaft for insertion into a cavity of a patient's organ; an expandable assembly attached to a distal end of the shaft and having elastic properties; a position sensing element mounted to the distal end of the shaft; at least one distal position sensing element on a distal end of the expandable assembly; 1. A processor comprising: 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; relating the deflection to a contact force applied to the expandable assembly; a processor configured to provide an indication of the contact force on a display; A system comprising:

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 controller is applying a drive signal of a given frequency to one of the proximal EMC and the at least one distal EMC; 3. The system of claim 2, configured to receive and process output at the given frequency 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.

4. 4. The system of claim 3, wherein each of the EMCs is configured to sense a magnetic field generated by a magnetic source external to the patient and output a respective signal indicative of a position in a 3D coordinate system of a position traction system, and the drive signal has a frequency different from a frequency used by the magnetic source external to the patient.

5. 4. The system of claim 3, comprising an amplifier circuit attached to the catheter, the circuit configured to amplify the output at the given frequency by the other of the proximal EMC and the at least one distal EMC.

6. 3. The system of claim 2, wherein the distal end of the shaft includes three EMCs oriented non-parallel to one another, and the processor is configured to detect at least one of axial compression of the expandable assembly and angular deflection of the expandable assembly relative to the distal end of the shaft by processing outputs from the three EMCs.

7. The system of claim 2 , wherein the at least one distal EMC is embedded within a respective electrode disposed on a spline.

8. The system of claim 2, wherein the distal end (46) of the shaft (44) comprises at least two EMCs (29) that are parallel and offset from one another on the shaft (44).

9. 2. The system of claim 1, further comprising: a memory configured to store a relationship between a position sensing element output and a contact force based on empirical data, the processor configured to use the empirical data to relate the position sensing element output to the contact force.

10. The system of claim 1 , wherein the expandable assembly is a basket assembly formed with a plurality of splines.

11. 1. A method comprising: Inserting a shaft of a medical probe into a cavity of a patient's organ, the probe comprising: (i) an expandable assembly attached to a distal end of the shaft and having elastic properties; (ii) a position sensing element mounted to the distal end of the shaft; and (iii) at least one distal position sensing element 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; and correlating the deflection to a contact force applied to the expandable assembly; providing an indication of said contact force on a display; and The method includes:

12. The method of claim 11 , wherein each of the proximal position sensing element and the at least one distal position sensing element is an electromagnetic coil (EMC).

13. applying a drive signal of a given frequency to one of the proximal EMC and the at least one distal EMC; 13. The method of claim 12, further comprising receiving and processing an output at the given frequency 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.

14. 14. The method of claim 13, wherein each of the EMCs is configured to sense a magnetic field generated by a magnetic source external to the patient and output a respective signal indicative of a position in a 3D coordinate system of a position traction system, and the drive signal has a frequency different from a frequency used by the magnetic source external to the patient.

15. 14. The method of claim 13, comprising amplifying the output from the three EMCs using an amplifier circuit attached to the catheter.

16. 13. The method of claim 12, wherein the distal end of the shaft includes three EMCs oriented non-parallel to one another, and the processor is configured to detect at least one of an axial compression of the expandable assembly and an angular deflection of the expandable assembly relative to the distal end of the shaft by processing outputs from the three EMCs.

17. The method of claim 12 , wherein the at least one distal EMC is embedded within a respective electrode disposed on a spline.

18. 13. The method of claim 12, comprising: storing a relationship between EMC output and contact force based on empirical data; and relating EMC output to contact force using the empirical data.

19. The method of claim 12 , wherein the expandable assembly is a basket assembly formed with a plurality of splines.

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