Zero-point force calibration for basket catheters

Abstract

To provide a method and system for estimating the mechanical / deformation force applied between a catheter and tissue. [Solution] This disclosure provides a system comprising a catheter having an expandable distal end assembly (EDEA) having multiple electrodes, and a processor. The processor is configured to receive input from a user commanding force zeroing measurements of the EDEA while it is in the patient's heart, to estimate the actual locations of at least some electrodes, to determine the standard positions of the electrodes, to calculate the deviation of the actual locations from the corresponding standard positions, and to enable or prevent force zeroing measurements according to the calculated deviation. The system improves the accuracy of force measurements by automatically determining when conditions are favorable for force zeroing and improves the reliability of subsequent force measurements during medical procedures.

Description

Technical Field

[0001] The present invention generally relates to medical devices, and more particularly, to methods and systems for estimating mechanical / deformation forces applied between a catheter and tissue.

Background Art

[0002] Various techniques for measuring and / or estimating contact forces applied inside tissue by medical devices are known in the art. Effective techniques for obtaining measurements of such forces are constantly being improved. In particular, catheters having an expandable distal end assembly (EDEA) with multiple electrodes are used in mapping and ablation procedures in the heart. These catheters often incorporate force sensing capabilities for measuring the contact force between the catheter and the heart tissue.

[0003] Catheters with an EDEA, such as basket catheters, can expand within the heart cavity and contact the heart cavity wall. The electrodes on these catheters can be used for various purposes, including sensing the electrical activity of the heart, delivering ablation energy, and providing position information. The ability to accurately determine the position of these electrodes within the heart is important for many cardiac procedures.

[0004] Position sensing techniques for medical devices have evolved significantly over the years. These techniques may utilize various physical principles, such as electromagnetic fields, electrical impedance measurements, or mechanical sensors, to determine the position and orientation of catheter electrodes within the body. Advanced signal processing techniques are often employed to improve the accuracy and reliability of these position measurements.

[0005] The mechanical properties of catheters, especially those with expandable components, can be complex. Catheters are often designed to be flexible enough to travel through blood vessels while maintaining sufficient rigidity to apply controlled forces when needed. The materials used in the catheter structure, such as nitinol, contribute to these mechanical properties.

[0006] As medical procedures become increasingly sophisticated, research and development is underway to improve the accuracy and reliability of medical devices and associated measurement technologies. This includes efforts to improve force sensing capabilities, position tracking accuracy, and the overall performance of catheter-based systems used in cardiac procedures.

[0007] The present invention will be better understood from the following detailed description of embodiments of the present disclosure, together with the drawings. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of a catheter-based position tracking and ablation system according to one embodiment of the present invention. [Figure 2] Figure 1 is a schematic diagram of the distal end assembly of a catheter in the system shown, illustrating different positions of the distal end assembly within a patient's heart according to one embodiment of the present invention. [Figure 3] This flowchart schematically illustrates a method for estimating zero-point force calibration according to one embodiment of the present invention. [Modes for carrying out the invention]

[0009] overview Calibration procedures play a crucial role in ensuring the accuracy of force measurements obtained from medical devices. These procedures may include establishing baseline measurements or determining standard positions under controlled conditions. Specific calibration requirements may vary depending on the type of device and its intended application.

[0010] Some medical procedures, such as pulsed-field ablation (PFA) and radiofrequency (RF) ablation of a patient's cardiac tissue, benefit from sensing the contact force applied to the tissue during ablation. The distal end assembly may comprise, for example, a basket assembly comprising ablation electrodes coupled to a flexible spline.

[0011] One challenge when using such catheters, particularly larger ones that can occupy a significant volume of the cardiac chamber, is accurately determining the zero-force state, i.e., the state of complete relaxation of the distal end assembly when it is not in contact with tissue. This is used to calibrate force measurements and ensure accurate force application during procedures. Conventional methods for zero-point force calibration, also referred herein as zero-point force calibration measurement, often rely on visual confirmation that the catheter appears to be centered in the cardiac chamber, assuming no contact with tissue. However, with larger catheters, even if the catheter appears to be centered in the cardiac chamber, it can be difficult to confirm non-contact with the wall in 3D space. Even small deformations can lead to unintended contact, making it difficult to guarantee the true absence of contact force. The relatively large dimensions of the nitinol basket, coupled with the complex morphology of the ventricle, present a significant challenge in ensuring the absence of contact during zero-point force calibration.

[0012] Furthermore, the force-deformation relationship in these catheters is often highly nonlinear, and the catheter is most sensitive to small forces when in its near-standard state. This sensitivity to small forces adds complexity to the task of accurately determining the zero-force state based on visual inspection. For example, the zero-force state may be misdetermined during unintended contact related to small deformations that are not visually apparent.

[0013] The automated approaches described herein help address this complexity in certain embodiments by identifying when electrodes on the EDEA are in their standard positions and activating, enabling, or preventing zero-point force calibration based on the calculated deviation from the standard positions. This automated evaluation capability may help improve the accuracy of zero-point force calibration in some embodiments. Improved zeroing techniques can potentially improve the overall accuracy of force measurements during treatment, leading to better patient outcomes and a more efficient workflow.

[0014] For example, consider a basket catheter. Basket catheters are typically constructed from nitinol splines with elastic-plastic properties, or any other material. Because nitinol is sensitive to temperature and in vivo conditions, the neutral, fully relaxed shape of a nitinol basket when positioned within the ventricular cavity may differ from its shape outside the patient.

[0015] Therefore, prior to estimating the mechanical force applied to the nitinol basket during the procedure, it is necessary to predetermine the shape of the nitinol basket when no mechanical force is being applied by cardiac tissue. This shape is referred to herein as the "zero-point force calibration."

[0016] Furthermore, the system may use an impedance-based touch proximity index (TPI) and electrocardiogram (ECG) signals to determine when the electrode is in contact with or near tissue. The TPI provides an indicator of the electrode's proximity to the tissue, while the ECG signal is detected when the electrode is near or in contact with the tissue, but may not be detected when the electrode is away from the tissue. By integrating this information, the system can make an optimal assessment of when to perform zero-point force calibration, thereby ensuring accurate force measurements during medical procedures.

[0017] Considering the above, it is desirable to provide a catheter-based diagnostic and / or therapeutic system that can automatically acquire the zero-point force calibration applied to the distal end assembly of the catheter and / or guide the user regarding when to initiate zeroing.

[0018] The embodiments of the present invention described below provide a technique for obtaining zero-point force calibration applied between the tissue in question (e.g., in a patient's heart) and the expandable distal end assembly (EDEA) of a catheter prior to ablation or sensing procedure. The disclosed technique relies on quantifying and using the elastic properties of the deformable components of the distal end assembly.

[0019] In some embodiments, the system may include a catheter having an expandable distal end assembly (EDEA) on which multiple electrodes are positioned, and a processor. The processor may be configured to receive input from a user instructing zero-point force calibration of the EDEA while the EDEA is in the patient's heart.

[0020] The processor may, for example, determine at least some standard positions of the electrodes relative to a reference point. While the EDEA is in vivo, the processor may estimate at least some actual locations of the electrodes. The processor may then calculate the deviation of the actual locations from the corresponding standard positions. Based on the calculated deviation, the processor may enable or disable (in other words, allow or override) the zero-point force calibration commanded by the user.

[0021] If zero-point force calibration is enabled, the processor may initiate zero-point force calibration based on the receipt of a command from the user. The processor may then calculate the force based on the deviation of the actual location and the output from the zero-point force calibration, and display the calculated force on an electronic display device.

[0022] The process of enabling and disabling zero-point force calibration can be repeated in vivo. For example, the processor can disable zero-point force calibration measurements based on the deviation exceeding a deviation threshold and resume another zero-point force calibration measurement based on the deviation falling below the deviation threshold.

[0023] This automated decision-making process may be important in some embodiments because the system can evaluate the suitability of the conditions for zero-point force calibration more accurately than a physician.

[0024] In some embodiments, if the calculated deviation exceeds a predetermined threshold, the processor may disable the use of zero-point force calibration. Conversely, if the calculated deviation is below the threshold, the processor may enable the use of zero-point force calibration. The threshold may be adjustable based on factors such as the specific procedure being performed or the patient's anatomical structure.

[0025] Alternatively, the system may search for the minimum deviation over a sensing period. During this period, the processor continuously monitors the deviation of the actual location from the standard position and identifies the location where the deviation is minimum. The measurement with this minimum deviation can then be used as the zero-point force calibration.

[0026] The system may provide feedback regarding the deviation to the user and, in some cases, enable the user to proceed with zero-point force calibration. This feedback may include visual or auditory cues to guide the user when repositioning the EDEA to achieve suitable conditions for zero force.

[0027] By automating the decision to perform zero-point force calibration, the system may help ensure more accurate and reliable force measurements during a medical procedure. This may, in some cases, lead to an improvement in patient outcomes and a more efficient workflow.

[0028] In some embodiments, the catheter includes an EDEA on which multiple electrodes are positioned. The EDEA is configured as a basket with one or more splines that can deform in response to mechanical force and return to its original shape when no force is applied. The splines are typically made of a shape memory alloy such as Nitinol, which has elastic and plastic properties and is biocompatible.

[0029] In some embodiments, electrodes on the EDEA serve multiple purposes. One electrode may function as a transmitter, and the other as a receiver. The transmitter is preferably a single-axis position sensor (TAS). The receiving electrode is typically a single-axis sensor (SAS) oriented to different 3D locations and orientations, designed to detect signals from the transmitter.

[0030] In some embodiments, the system includes position sensing capabilities for electrodes on the EDEA. Position sensing may allow for the determination of the actual location of the electrodes within the patient's heart.

[0031] In some embodiments, the transmitter is located on the distal end of the shaft and the receiver is located on the distal end of the EDEA. This configuration allows the transmitter to emit a signal that is detected by the receiver, enabling the system to accurately determine the electrode position and evaluate the deformation of the EDEA.

[0032] Furthermore, the system may use a Bézier curve-based approach. This method may include sensing the location and position of the catheter shaft, as well as the uniaxial sensor (SAS) at the distal end of the basket. The system may then use the Bézier curve to determine the shape of each spline, which may then be used to determine the location of each electrode on the spline.

[0033] In some embodiments, the sensor may be an actual coil or a printed coil.

[0034] In some embodiments, position sensing may utilize multiple approaches. For example, the system may employ advanced current localization (ACL) techniques to determine the location of each electrode. This method may involve applying a current and measuring the resulting voltage to calculate the electrode position.

[0035] The system may combine data from both ACL and Bézier curve-based approaches to improve the accuracy of electrode location estimation.

[0036] In some embodiments, the system may use a model of the catheter mechanism to further improve electrode location estimation based on these two methods. This method must incorporate constraints arising from the mechanical properties of the catheter. These constraints may include the elastic and deformable properties of the catheter material, the expected response to applied forces, and the geometric configuration of the splines. By integrating these mechanical constraints, the system can improve the accuracy of the Bézier curve representation and thus the accuracy of electrode location estimation.

[0037] Position sensing capabilities may allow the system to track the deformation of the EDEA in real time as it interacts with cardiac tissue. This information may be used to calculate the deviation of the actual electrode locations from their standard positions, which may then be used to determine when conditions are suitable for force zeroing measurements.

[0038] In some embodiments, the catheter comprises a transmitter and an EDEA having one or more receivers, typically implemented using electric coils. The transmitter is coupled to the shaft of the catheter or to the irrigation device. One or more receivers are coupled to each of the deformable components of the EDEA. For example, (i) in an EDEA comprising a basket, one or more receivers may be coupled to each spline of the basket.

[0039] One or more receivers are electrically connected to the processor, and the transmitters are electrically connected to the processor or a signal generator controlled by the processor. In some embodiments, the electrical connection may be (i) via wires or traces operating between the proximal and distal ends of the catheter, for example, between the EDEA and the operating console of the system comprising the processor, or (ii) wirelessly using wireless devices connected to the proximal and distal ends of the catheter.

[0040] In some embodiments, the processor is configured to apply a transmit signal, referred to herein as the first signal, to a transmitter, and at least one of the receivers is configured to generate a receive signal, referred herein as the second signal, in response to receiving the first signal.

[0041] In some embodiments, during and prior to zero-point force calibration, the physician inserts the EDEA into the patient's heart, expands the EDEA to its expansion location, positions the EDEA in contact with tissue, and moves the EDEA between several different locations within the heart. For each location of the EDEA within the heart, the processor is configured to estimate the zero-point force calibration of the EDEA based on user input instructing the EDEA while it is inside the patient's heart.

[0042] Alternatively, the system may perform zero-point force calibration automatically without user intervention. In this method, the processor continuously monitors the deviation of the EDEA from its standard position as it moves within the heart. The processor identifies the location where the deviation is smallest and automatically performs zero-point force calibration based on this minimum deviation.

[0043] The processor may estimate the actual locations of at least some of the electrodes and compare them to at least some standard locations of the electrodes. The processor may then calculate the deviation of the actual locations from the corresponding standard locations. Based on the calculated deviation, the processor may enable or prevent zero-point force calibration as instructed by the user.

[0044] In some embodiments, the processor is configured to record the output from the SAS sensor or other deformation-sensing sensor through zero-point force calibration.

[0045] In some embodiments, if the calculated deviation exceeds a predetermined threshold, the processor may prevent recording the zero-point force calibration and then allow another zero-point force calibration to be performed. Conversely, if the calculated deviation falls below the threshold, the processor may enable recording the zero-point force calibration.

[0046] In some embodiments, the system / processor may use displays to provide visual or auditory feedback to guide the user when repositioning the EDEA to achieve conditions suitable for zero-point force calibration. This feedback may include a real-time indicator of the current deviation and suggestions for catheter movements that may reduce the deviation.

[0047] The threshold may be adjustable based on factors such as the specific procedure being performed or the patient's anatomical structure. In some embodiments, the processor may provide feedback to the user regarding the deviation, allowing the user to decide whether to proceed with zero-point force calibration. In some embodiments, the threshold deviation is predetermined. The user may also manually adjust the threshold. More likely, the system uses the deviation from a standard position, along with the touch proximity index (TPI) and electrocardiogram (ECG) recording, to find the optimal moment to capture the zero state. In this case, the threshold may be used as a hard stop, meaning that it is clearly indicated that zero-point force calibration cannot be performed if the deviation exceeds this threshold.

[0048] The disclosed technology improves force sensing capabilities. Force sensing may be used to improve the quality of cardiac procedures, such as PFA and / or RF ablation, and electrophysiological mapping, by improving the accuracy and reducing the complexity of sensing the mechanical force applied between the ablation electrode and the tissue intended to be ablated during RF ablation procedures. The disclosed technology is also applicable to any other medical procedures that require accurate sensing of mechanical force between medical devices pressed against tissue, with modifications as necessary.

[0049] System Description Figure 1 is a schematic diagram of a catheter-based position tracking and ablation system 10 according to one embodiment of the present invention.

[0050] System 10 includes one or more catheters inserted percutaneously by a physician 24 into a cardiac chamber or vascular structure of the heart 12 through the patient's vascular system. Typically, a delivery sheath catheter is inserted into the left or right atrium near a desired location in the heart 12. One or more catheters can then be sequentially inserted into the delivery sheath catheter to reach the desired location. 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 embodiment of a basket catheter 14 configured for ablation to sense IEGM is shown herein. In another embodiment, catheter 14 may be an ablation and sensing tip catheter fitted with a contact force mechanism described in U.S. Patent No. 8,535,308, assigned to the assignee of this application.

[0051] As shown in inset 45, physician 24 brings the basket assembly 28 (hereinafter also referred to as the "expandable distal end assembly 28") attached to the shaft 44 of the catheter 14 into contact with the heart wall to sense the target site within the heart 12. For ablation, physician 24 similarly brings the distal end of the ablation catheter to the target site for ablation.

[0052] As shown in inset 65, the basket catheter 14 is an exemplary catheter comprising one, preferably more than one, electrodes 26 distributed across a plurality of splines 22 in an optionally expandable distal end assembly 28 and configured to ablate and / or sense IEGM signals. The catheter 14 further comprises (i) a proximal position sensor 29 (e.g., a biaxial sensor (DAS) 29 with two orthogonal EMCs or a triaxial sensor (TAS) with three orthogonal EMCs) embedded in the distal end 46 of a shaft 44 near the basket assembly 28, and (ii) three distal position sensors 39 (e.g., a monoaxial sensor (SAS) 39 with a single EMC) for tracking the position of the distal end of the basket assembly 28. Optionally and preferably, the position sensors 29 and 39 are magnetic-based position sensors comprising a magnetic coil for sensing three-dimensional (3D) position. An embodiment reference electrode 31 positioned at the base of the assembly 28 is also shown.

[0053] Now, let us refer again to the overall view in Figure 1. In some embodiments, during the navigation of the distal end assembly 28 within the heart 12, the processor 56 receives signals from magnetic position sensors 29 and 39.

[0054] This position sensing method, which uses an external magnetic field, is implemented in various medical applications, for example, in the CARTO® system manufactured by Biosense Webster Inc. (Irvine, Calif.), and is described in detail in U.S. Patents 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612, and 6,332,089, International Publication 96 / 05768, and U.S. Patent Application Publications 2002 / 0065455(A1), 2003 / 0120150(A1), and 2004 / 0068178(A1), all of which are incorporated herein by reference.

[0055] The magnetic position sensors (29, 39) (i.e., coil assemblies) may further operate with an external position pad 25 which includes a plurality of magnetic coils 32 configured to generate a magnetic field within a given working volume. To prevent signal interference, the frequencies of these fields are different from any given frequency used in local transmitter-receiver mode for contact force detection. The real-time orientation of the basket assembly 28 of the catheter 14 is thus calculated from the tracked locations of the sensors 29 and 39 (locations generated using the position pad 25 and tracked using a magnetic field sensed by the magnetic-based position sensors 29 and 39). This relative orientation is revealed by the angle formed between the distal end 46 and the longitudinal axis 42 of the expandable assembly 28 (leading to the distal edge 16 of the assembly).

[0056] Details of magnetic-based position sensing technology are described in U.S. Patents No. 5,5391,199, No. 5,443,489, No. 5,558,091, No. 6,172,499, No. 6,239,724, No. 6,332,089, No. 6,484,118, No. 6,618,612, No. 6,690,963, No. 6,788,967, and No. 6,892,091.

[0057] System 10 includes one or more electrode patches 38 placed for skin contact on a patient 23 to establish a position reference for the position pad 25 and impedance-based tracking of the electrodes 26. For impedance-based tracking, a current is directed to the electrodes 26 and sensed by the electrode skin patches 38, thereby allowing the position of each electrode to be triangulated through 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.

[0058] The recorder 11 displays the electrophysiogram 21 captured by the surface ECG electrode 18 and the intracardiac electrophysiogram (IEGM) captured by the electrode 26 of the catheter 14. The recorder 11 may include pacing capabilities for pacing the rhythm of the heart and / or may be electrically connected to a standalone pacer.

[0059] System 10 may include an ablation energy generator 50 adapted to conduct ablation energy to one or more electrodes located 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, or a combination thereof, including unipolar or bipolar high-voltage DC pulses that can be used to induce irreversible electroporation (IRE).

[0060] The patient interface unit (PIU) 30 is configured to establish electrical communication between the catheter, the electrophysiological equipment, the power supply, and the workstation 55 that controls the operation of the system 10. The electrophysiological equipment of the system 10 may include, for example, multiple catheters, a position pad 25, a body surface ECG electrode 18, an electrode patch 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 location and performing ECG calculations.

[0061] The workstation 55 includes memory 57, a processor unit 56 having memory or storage device in which appropriate operating software is loaded, and user interface functions. The workstation 55 may optionally provide several functions, including (i) modeling the endocardial anatomical structure in three dimensions (3D) and rendering the model or anatomical map 20 to be displayed on a display device 27, (ii) displaying an activation sequence (or other data) compiled from a recorded electrophoresis diagram 21 on the display device 27 as a representative visual representation or image superimposed on the rendered anatomical map 20, (iii) displaying the real-time position and orientation of multiple catheters in the cardiac chambers, and (iv) displaying a site of interest on the display device 27, such as the location where ablation energy is applied. A single commercial product embodying each element of System 10 is available as the CARTO® 3 system, commercially available from Biosense Webster, Inc., 31A Technology Drive, Irvine, CA 92618.

[0062] Figure 1 illustrates a basket assembly, but the figure and the disclosed method are applicable to multilayer assemblies and balloon assemblies with necessary modifications.

[0063] This particular configuration of System 10 is shown as an example to illustrate the specific problems addressed by the embodiments of the present invention and to demonstrate the application of these embodiments in improving the performance of such systems. However, the embodiments of the present invention are by no means limited to this particular type of representative system, and the principles described herein may be similarly applied to other types of medical systems and procedures.

[0064] Distal end assembly and force zeroing measurement Figure 2 is a schematic diagram of an expandable distal end assembly (EDEA) 28 in an expanded position at three exemplary positions 60A, 60B, and 60C within the heart 12, according to one embodiment of the present invention.

[0065] When the distal end assembly 28 is located within the center 60A of the heart 12, no mechanical force is exerted on the distal end assembly 28 by the tissue 47 of the heart 12, and therefore, a neutral shape suitable for zero-point force calibration is maintained.

[0066] When the distal end assembly 28 is located near and in contact with the tissue at position 60B of the heart 12, some small mechanical force is applied to the distal end assembly 28 by the tissue 47. However, this mechanical force is lower than a specific threshold of about 1 gram required to deform the neutral shape of the distal end assembly 28.

[0067] Finally, when the distal end assembly 28 is positioned in contact with the tissue 47 at position 60C of the heart 12, a significant mechanical force is exerted on the distal end assembly 28. This mechanical force is higher than a specific threshold required to deform the neutral shape of the distal end assembly 28.

[0068] As can be understood, of the three positions 60A, 60B, and 60C, the measurement performed at position 60A is most suitable for functioning as a zero-point force calibration measurement. In some embodiments, the processor 56 identifies this measurement and stores it for later use.

[0069] The inset on the right side of Figure 2 provides a more detailed view of the structure of the distal end assembly 28. In this embodiment, the distal end assembly 28 is a basket assembly comprising multiple splines 22.

[0070] In some embodiments, one or more ablation electrodes 26 are connected to each spline 22 and configured to apply ablation pulses(s) to the tissue of the heart 12. The ablation pulses(s) are intended to kill cells in the tissue in question and, instead of tissue, produce damage that prevents or reduces the propagation of electrophysiological (EP) waves through the ablated tissue.

[0071] In some embodiments, one or more ablation electrodes 26 are also used to sense impedance for TPI and to sense ECG signals for mapping purposes. This dual functionality of the electrodes improves the system's ability to accurately determine the proximity and contact state of the electrodes with the tissue, thereby improving the accuracy of both the ablation and mapping techniques.

[0072] In some embodiments, the distal end assembly 28 comprises a plurality of electrodes (26), a transmitter 88, and one or more receivers 99. The transmitter 88 is coupled to a rigid component of the distal end assembly 28. In other embodiments, the transmitter 88 may be coupled to any other suitable rigid component of the distal end assembly 28, such as a shaft 44. In the context of this disclosure and the claims, the term “rigid” means a component of the catheter 14 that moves with the catheter, and whose location is not affected by any force, such as a contact force applied to the distal end assembly 28, as will be described in detail below. In other words, the transmitter 88 has the same angular velocity and the same angular acceleration as the distal end of the shaft 44.

[0073] In some embodiments, one or more receivers 99 are coupled to each elastic component of the distal end assembly 28. In this embodiment, one receiver 99 is coupled to each spline 22 of the basket. Although only three receivers 99 are shown in the embodiment of Figure 2, it should be noted that even though some of the receivers 99 are obscured by the isometric perspective of the distal end assembly 28, the receivers 99 are still coupled to each spline 22 and are therefore not shown in the exemplary configuration of Figure 2.

[0074] In some embodiments, the transmitter 88 and the receiver 99 may each be implemented using electrical coils connected to the spline 22. The coils of the transmitter 88 and the receiver 99 are electrically connected to the processor 56 using any preferred connection technique.

[0075] In some embodiments, the receiver 99 is electrically connected to the processor 56 (for example, via the traces of the aforementioned flexible PCB and via the catheter 14). Furthermore, the transmitter 88 is electrically connected to the processor 56 (for example, via a wire operating between (i) the distal end of the shaft 44 or the irrigator 60 and (ii) the proximal end of the catheter 14). Additionally or alternatively, the transmitter 88 may be electrically connected to a pulse generator (not shown) controlled by the processor 56 and configured to apply one or more pulses using the transmitter 88 as described below.

[0076] In other embodiments, the electrical connection between (i) the transmitter 88 and / or receiver 99 and (ii) the processor 56 may be made using wireless devices (not shown) connected to the proximal and distal ends of the catheter 14.

[0077] In some embodiments, the processor 56 is configured to control the transmitter 88 to apply a transmit signal, which is referred to herein as the first signal. In response to receiving the first signal, typically at least one of all the receivers 99 is configured to generate a received signal, which is referred to herein as the second signal.

[0078] In some embodiments, a second signal generated by a given receiver 99 indicates the distance between the transmitter 88 and the given receiver 99, as described below.

[0079] In some embodiments, during the zero-point force calibration procedure and prior to the ablation procedure, physician 24 inserts the distal end assembly 28 into the cavity of the heart 12. The physician 24 then expands the distal end assembly 28 to the expanded position (as shown in the embodiment of Figure 2), presses the zeroing button, and manipulates the distal end assembly 28 within the heart 12 to perform the zero-point force calibration procedure.

[0080] In some embodiments, during the zero-point force calibration procedure, the physician 24 moves the EEDA 28 to multiple locations within the heart 12, for example, positions 60A, 60B, and 60C. As described above, the zero-point force calibration measurement performed at position 60A is the most suitable measurement to function as a zero-point force calibration measurement.

[0081] In some embodiments, at the end of the zero-point force calibration procedure, physician 24 presses a zeroing button to mark the end of the zero-point force calibration procedure.

[0082] In some embodiments, during the zeroing force calibration procedure, the processor 56 is configured to control the transmitter 88 to apply the transmission signal until the physician 24 completes the zeroing procedure.

[0083] In some embodiments, the processor 56 is configured to estimate the mechanical force applied to the spline with a typical sensitivity of about 5 grams, which is referred to herein as gram weight (GF), although typical values ​​of the mechanical force applied in such a procedure range from about 0 grams to 100 grams.

[0084] Accordingly, the disclosed technology improves the quality of the ablation procedure by improving the accuracy of the estimated mechanical force applied between the ablation electrode 26 and the tissue of the heart 12, which are intended to be ablated during the RF ablation procedure described above. The disclosed technology is also applicable, with modifications as necessary, to any other medical procedure that requires accurate and stable sensing of mechanical force between medical devices pressed against tissue.

[0085] This configuration of the distal end assembly 28 is provided in Figure 2 as an example to illustrate the specific problems addressed by embodiments of the present invention and to demonstrate the application of these embodiments in improving the performance of such distal ends for treating arrhythmias in a patient's heart. However, embodiments of the present invention are not limited to this particular type of exemplary distal end assembly, and the principles described herein may also be applied to other types of catheters used in any suitable type of medical system and procedure that require the measurement or estimation of mechanical force applied to any suitable type of medical device that is pressed against any suitable tissue of a patient.

[0086] Figure 3 is a schematic flowchart illustrating a method for estimating zero-point force calibration values ​​for a distal end assembly 28 located within the tissue of a heart 12, according to one embodiment of the present invention.

[0087] This method begins in step 100, prior to catheter insertion, and during calibration prior to inserting the catheter into the body, the positions of each electrode in a standard configuration are uploaded to the processor 56.

[0088] In the position sensing step 102, the processor 56 calculates the actual location of each electrode within the heart.

[0089] Subsequently, in the position error calculation step 104, the processor 56 calculates the root mean square error (RMSE) between the pre-loaded standard positions and the actual locations of each electrode.

[0090] In the optimization step (not shown in the flowchart), the system is configured to optimize the zero-point force calibration measurement by identifying the best zeroing time within a threshold. This optimization is based on a cost function that considers multiple factors, including minimum RMSE, minimum TPI, and minimum ECG gain.

[0091] In decision step 106, the processor 56 compares the calculated RMSE with a predetermined threshold.

[0092] If the RMSE exceeds the threshold (Yes branch), the process proceeds to step 108, which disables the zero-point force calibration option.

[0093] In step 108, any zero-point force calibration measurements commanded by the user are disabled. This method then returns to repeat steps 102-106.

[0094] If the RMSE is not above the threshold (NO branch), the process proceeds to step 110, which enables the zero-point force calibration option, and the zero-point force calibration option is enabled.

[0095] In step 110, the zero-point force calibration measurement is recorded and used in the subsequent deformation measurement step 112, which is to estimate the mechanical force exerted on the deformable components by the cardiac wall tissue during the subsequent deformation measurement, for example, during an ablation procedure.

[0096] The flow in Figure 3 is an illustrative flow shown purely for the sake of conceptual clarity. Any other suitable flow can be used in alternative embodiments. For example, in some embodiments, the processor monitors the impedance and / or intracardiac electrogram (ICEG) at each of several electrodes and enables or disables zero-point force calibration measurements based on predetermined criteria defined for the impedance and / or ICEG, and based on a comparison of the deviation with a deviation threshold.

[0097] In some embodiments, the deviation threshold is dynamically updated based on the deviation calculated over a defined period. In some embodiments, the deviation threshold is user-defined.

[0098] In one embodiment, the command to initiate zero-point force calibration is based on user input requesting zero-point force calibration. In another embodiment, the command is automated based on the processor identifying a predetermined event.

[0099] In one embodiment, the processor renders a virtual representation of the EDEA and updates the shape of the virtual representation based on the monitored actual locations of multiple electrodes.

[0100] In another embodiment, the EDEA takes the form of a basket containing multiple deformable splines, and the actual locations of the multiple electrodes are determined based on the mechanical model of the EDEA and the outputs from multiple magnetic-based position sensors mounted on the deformable splines. Typically, a standard configuration of the EDEA is predetermined ex vivo during a calibration procedure.

[0101] While the embodiments described herein primarily address the estimation of force zeroing measurements applied between an expandable distal end assembly of an RF ablation catheter and the tissue intended to be ablated, the methods and systems described herein may also be used in other applications, such as any application requiring accurate measurement of contact force applied between any suitable medical device and any suitable tissue of a patient's organ, for example, in the organs of a patient's ear, nose, and throat (ENT) system. [Examples]

[0102] Example 1: A system comprising a catheter, a processor, and an electronic display device. The catheter includes an expandable distal end assembly (EDEA) on which multiple electrodes are positioned. The processor is configured to store in memory the standard positions of the multiple electrodes of the catheter relative to a reference point, monitor the actual locations of the multiple electrodes while the EDEA is in vivo, and enable or disable zero-point force calibration based on comparing the deviation of the actual locations from the standard positions with a deviation threshold. If zero-point force calibration is enabled, the processor is further configured to activate zero-point force calibration based on receiving a command and to calculate a force based on the deviation of the actual locations and the output from the zero-point force calibration. The configured electronic display device is configured to display the calculated force.

[0103] Example 2: A system according to Example 1, wherein the processor is configured to disable a zero-point force calibration measurement based on the deviation exceeding a deviation threshold, and to restart another zero-point force calibration measurement based on the deviation falling below a deviation threshold.

[0104] Example 3: A system according to Example 1, wherein the processor is configured to monitor one or both of the impedance and intracardiac electrogram (ICEG) at each of a plurality of electrodes, and to enable or disable zero-point force calibration measurement based on predetermined criteria defined for one or both of the impedance and ICEG, and based on a comparison of the deviation with a deviation threshold.

[0105] Example 4: A system according to Example 1, wherein the deviation threshold is dynamically updated based on deviations calculated over a defined period.

[0106] Example 5: A system as described in Example 1, wherein the deviation threshold is user-defined.

[0107] Example 6: A system as described in Example 1, wherein the command is based on user input requesting zero-point force calibration.

[0108] Example 7: A system as described in Example 1, wherein commands are automated based on the processor identifying a predetermined event.

[0109] Example 8: A system according to Example 1, wherein the processor is configured to render a virtual representation of the EDEA and update the shape of the virtual representation based on the actual locations of a plurality of monitored electrodes.

[0110] Example 9: The system according to Example 1, wherein the EDEA is in the form of a basket containing a plurality of deformable splines, and the actual locations of the plurality of electrodes are determined based on the mechanical model of the EDEA and the outputs from a plurality of magnetic-based position sensors mounted on the deformable splines.

[0111] Example 10: A system as described in Example 1, wherein the standard configuration of the EDEA is predetermined in vitro during the calibration procedure.

[0112] Example 11: A method comprising storing in memory the standard positions of multiple electrodes positioned on an expandable distal end assembly (EDEA) of a catheter relative to a reference point. The actual locations of the multiple electrodes are monitored while the EDEA is in vivo. Zero-point force calibration is enabled or disabled based on comparing the deviation of the actual locations from the standard positions with a deviation threshold. When zero-point force calibration is enabled, it is activated based on receiving a command. Forces are calculated based on the deviation of the actual locations and output from zero-point force calibration. The calculated forces are displayed.

[0113] It will be understood that the embodiments described above are cited as examples and that the present invention is not limited to those specifically shown and described above. Rather, the scope of the present invention includes both combinations and partial combinations of the various features described above, as well as variations and modifications thereof not disclosed in the prior art, which would be conceivable to those skilled in the art by reading the foregoing description. Documents incorporated into this patent application by reference should be considered integral parts of this application, except that any term in these incorporated documents is defined in a manner inconsistent with the definitions made herein, either explicitly or implicitly.

[0114] [Implementation Method] (1) A system, A catheter comprising an expandable distal end assembly (EDEA) including a plurality of electrodes positioned on top of the catheter, and It is a processor, The standard positions of the multiple electrodes of the catheter relative to the reference point are stored in memory. While the EDEA is in the body, the actual location of the multiple electrodes is monitored. Based on comparing the deviation of the actual location from the standard location with a deviation threshold, zero-point force calibration is enabled or disabled. When the zero-point force calibration is enabled, the zero-point force calibration is activated based on the receipt of a command. A processor configured to calculate force based on the deviation of the actual location and the output from the zero-point force calibration, and A system comprising an electronic display device configured to display the calculated force. (2) The system according to Embodiment 1, wherein the processor is configured to disable the zero-point force calibration measurement based on the deviation exceeding the deviation threshold and to restart another zero-point force calibration measurement based on the deviation falling below the deviation threshold. (3) The system according to Embodiment 1, wherein the processor is configured to monitor one or both of the impedance and intracardiac electrogram (ICEG) at each of the plurality of electrodes, and to enable or disable the zero-point force calibration measurement based on predetermined criteria defined for one or both of the impedance and ICEG, and based on the comparison of the deviation with the deviation threshold. (4) The system according to Embodiment 1, wherein the deviation threshold is dynamically updated based on the deviation calculated over a defined period. (5) The system according to Embodiment 1, wherein the deviation threshold is user-defined.

[0115] (6) The system according to Embodiment 1, wherein the command is based on user input requesting the zero-point force calibration. (7) The system according to Embodiment 1, wherein the command is automated based on the processor identifying a predetermined event. (8) The system according to Embodiment 1, wherein the processor is configured to render a virtual representation of the EDEA and update the shape of the virtual representation based on the actual locations of the monitored plurality of electrodes. (9) The system according to Embodiment 1, wherein the EDEA is in the form of a basket comprising a plurality of deformable splines, and the actual locations of the plurality of electrodes are determined based on a mechanical model of the EDEA and outputs from a plurality of magnetic-based position sensors mounted on the deformable splines. (10) The system according to Embodiment 1, wherein the standard configuration of the EDEA is predetermined in vitro during a calibration procedure.

[0116] (11) A method, The standard positions of multiple electrodes placed on the expandable distal end assembly (EDEA) of the catheter relative to a reference point are stored in memory, While the EDEA is in the body, the actual location of the multiple electrodes is monitored, Based on comparing the deviation of the actual location from the standard location with a deviation threshold, zero-point force calibration is enabled or disabled. When the aforementioned zero-point force calibration is enabled, the zero-point force calibration is activated based on the receipt of a command, The force is calculated based on the deviation of the actual location and the output from the zero-point force calibration, A method comprising displaying the calculated force. (12) The method according to Embodiment 11, wherein enabling or disabling the zero-point force calibration includes disabling the zero-point force calibration measurement based on the deviation exceeding the deviation threshold, and restarting another zero-point force calibration measurement based on the deviation falling below the deviation threshold. (13) The method according to Embodiment 11, wherein enabling or disabling the zero-point force calibration includes monitoring one or both of the impedance and intracardiac electrogram (ICEG) in each of the plurality of electrodes, and enabling or disabling the zero-point force calibration measurement based on predetermined criteria defined for one or both of the impedance and ICEG, and based on the comparison of the deviation with the deviation threshold. (14) The method according to Embodiment 11, comprising dynamically updating the deviation threshold based on the deviation calculated over a defined period. (15) The method according to embodiment 11, wherein the deviation threshold is user-defined.

[0117] (16) The method according to Embodiment 11, wherein the command is based on user input requesting the zero-point force calibration. (17) The method according to embodiment 11, wherein the command is automated based on the identification of a predetermined event. (18) The method according to Embodiment 11, comprising rendering a virtual representation of the EDEA and updating the shape of the virtual representation based on the actual locations of the monitored plurality of electrodes. (19) The method according to Embodiment 11, wherein the EDEA is in the form of a basket including a plurality of deformable splines, and the actual location of the plurality of electrodes is determined by a mechanical model of the EDEA and outputs from a plurality of magnetic-based position sensors mounted on the deformable splines. (20) The method according to Embodiment 11, wherein the standard configuration of the EDEA is determined in vitro during the calibration procedure.

Claims

1. It is a system, A catheter comprising an expandable distal end assembly (EDEA) including a plurality of electrodes positioned on top of the catheter, and It is a processor, The standard positions of the multiple electrodes of the catheter relative to the reference point are stored in memory. While the EDEA is in the body, the actual locations of the multiple electrodes are monitored. Based on comparing the deviation of the actual location from the standard location with a deviation threshold, zero-point force calibration is enabled or disabled. When the zero-point force calibration is enabled, the zero-point force calibration is activated based on the receipt of a command. A processor configured to calculate force based on the deviation of the actual location and the output from the zero-point force calibration, and A system comprising an electronic display device configured to display the calculated force.

2. The system according to claim 1, wherein the processor is configured to disable the zero-point force calibration measurement based on the deviation exceeding the deviation threshold, and to restart another zero-point force calibration measurement based on the deviation falling below the deviation threshold.

3. The system according to claim 1, wherein the processor is configured to monitor one or both of the impedance and intracardiac electrogram (ICEG) at each of the plurality of electrodes, and to enable or disable the zero-point force calibration measurement based on predetermined criteria defined for one or both of the impedance and the ICEG, and based on the comparison of the deviation with the deviation threshold.

4. The system according to any one of claims 1 to 3, wherein the deviation threshold is dynamically updated based on the deviation calculated over a defined period.

5. The system according to any one of claims 1 to 3, wherein the deviation threshold is user-defined.

6. The system according to any one of claims 1 to 3, wherein the command is based on user input requesting the zero-point force calibration.

7. The system according to any one of claims 1 to 3, wherein the command is automated based on the processor identifying a predetermined event.

8. The system according to any one of claims 1 to 3, wherein the processor is configured to render a virtual representation of the EDEA and update the shape of the virtual representation based on the actual locations of the monitored plurality of electrodes.

9. The system according to any one of claims 1 to 3, wherein the EDEA is in the form of a basket including a plurality of deformable splines, and the actual locations of the plurality of electrodes are determined based on a mechanical model of the EDEA and outputs from a plurality of magnetic-based position sensors mounted on the deformable splines.

10. The system according to any one of claims 1 to 3, wherein the standard configuration of the EDEA is predetermined in vitro during a calibration procedure.

11. It is a method, The standard positions of multiple electrodes placed on the expandable distal end assembly (EDEA) of the catheter relative to a reference point are stored in memory, While the EDEA is in the body, the actual location of the multiple electrodes is monitored, Based on comparing the deviation of the actual location from the standard location with a deviation threshold, zero-point force calibration is enabled or disabled. When the aforementioned zero-point force calibration is enabled, the zero-point force calibration is activated based on the receipt of a command, The force is calculated based on the deviation of the actual location and the output from the zero-point force calibration, A method comprising displaying the calculated force.

12. The method according to claim 11, wherein enabling or disabling the zero-point force calibration includes disabling the zero-point force calibration measurement based on the deviation exceeding the deviation threshold, and restarting another zero-point force calibration measurement based on the deviation falling below the deviation threshold.

13. The method according to claim 11, wherein enabling or disabling the zero-point force calibration includes monitoring one or both of the impedance and intracardiac electrogram (ICEG) in each of the plurality of electrodes, and enabling or disabling the zero-point force calibration measurement based on predetermined criteria defined for one or both of the impedance and the ICEG, and based on the comparison of the deviation with the deviation threshold.

14. The method according to any one of claims 11 to 13, comprising dynamically updating the deviation threshold based on the deviation calculated over a defined period.

15. The method according to any one of claims 11 to 13, wherein the deviation threshold is user-defined.

16. The method according to any one of claims 11 to 13, wherein the command is based on user input requesting the zero-point force calibration.

17. The method according to any one of claims 11 to 13, wherein the command is automated based on the identification of a predetermined event.

18. The method according to any one of claims 11 to 13, comprising rendering a virtual representation of the EDEA and updating the shape of the virtual representation based on the actual locations of the monitored plurality of electrodes.

19. The method according to any one of claims 11 to 13, wherein the EDEA is in the form of a basket including a plurality of deformable splines, and the actual location of the plurality of electrodes is determined based on a mechanical model of the EDEA and outputs from a plurality of magnetic-based position sensors mounted on the deformable splines.

20. The method according to any one of claims 11 to 13, wherein the standard configuration of the EDEA is determined in advance in vitro during a calibration procedure.

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