Accurate measurement of distal end dimensions

Abstract

The invention is entitled "Accurate measurement of distal tip size". In one embodiment, a system comprises: a generator coil generating respective magnetic fields; a catheter comprising a distal tip comprising magnetic coil sensors for outputting electrical signals based on detection of the respective magnetic fields; and processing circuitry for receiving the electrical signals from the magnetic coil sensors, selecting at least one magnetic field of the magnetic fields having a magnetic field gradient according to at least one of the received electrical signals, calculating a difference between magnetic field sizes of at least one selected magnetic field detected by the first and second magnetic coil sensors according to the electrical signals, and calculating a size of the distal tip based on the difference between the magnetic field sizes of the at least one selected magnetic field and the magnetic field gradient of the at least one selected magnetic field.

Description

Technical Field

[0001] This invention relates to medical systems, and specifically, but not exclusively, to catheter devices. Background Technology

[0002] Numerous medical procedures involve placing probes, such as catheters, inside a patient's body. Position sensing systems have been developed to track these probes. Magnetic position sensing is one method known in the art. In magnetic position sensing, a magnetic field generator is typically placed at a known location outside the patient's body. A magnetic field sensor within the distal end of the probe generates electrical signals in response to these magnetic fields; these signals are processed to determine the coordinate position of the distal end of the probe. These methods and systems are described in U.S. Patents 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612, and 6,332,089, in PCT International Patent Publication WO 1996 / 005768, and in U.S. Patent Application Publications 2002 / 0065455, 2003 / 0120150, and 2004 / 0068178. Impedance- or current-based systems can also be used to track position.

[0003] Treatment of arrhythmias is a medical procedure in which these types of probes or catheters have proven extremely useful. Arrhythmias, and specifically atrial fibrillation, have always been a common and dangerous medical condition, especially in the elderly.

[0004] The diagnosis and treatment of cardiac arrhythmias involve mapping the electrical properties of cardiac tissue, particularly the endocardium and cardiac volume, and selectively ablating cardiac tissue by applying energy. Such ablation can stop or alter unwanted electrical signals propagating from one part of the heart to another. Ablation methods disrupt unwanted electrical pathways by creating a non-conductive ablation focus. Various forms of energy delivery for creating ablation focuses have been disclosed, including the use of microwaves, lasers, and more commonly, radiofrequency energy to create conduction blocks along the cardiac tissue walls. In a two-step procedure (mapping followed by ablation), electrical activity at various points within the heart is typically sensed and measured by advancing a catheter containing one or more electrical sensors into the heart and acquiring data at multiple points. This data is then used to select the target endocardial region to be ablated.

[0005] Electrode catheters have been widely used in medical practice for many years. They are used to stimulate and map electrical activity in the heart, as well as to ablate sites of abnormal electrical activity. In use, the electrode catheter is inserted into a major vein or artery, such as the femoral vein, and then guided to the ventricle of interest. A typical ablation procedure involves inserting a catheter with one or more electrodes at its distal end into the ventricle. A reference electrode can be provided, typically taped to the patient's skin, or a second catheter positioned in or near the heart can be used to provide the reference electrode. RF (radio frequency) current is applied between the tip electrode of the ablation catheter and the reference electrode, flowing through the medium between these two electrodes (i.e., blood and tissue). The current distribution depends on the amount of contact between the electrode surface and the tissue compared to blood, which has a higher conductivity than tissue. Due to the resistance of the tissue, heating occurs. The tissue is heated sufficiently to destroy the cells in the heart tissue, resulting in the formation of a non-conductive ablation focus within the heart tissue. Summary of the Invention

[0006] According to an embodiment of this disclosure, a medical system is provided, comprising: generator coils configured to generate corresponding magnetic fields having correspondingly different frequencies in a region of a body part of a living subject; a catheter configured to be inserted into the body part of the living subject and including a distal end comprising magnetic coil sensors configured to output electrical signals based on the detection of the corresponding magnetic fields, and including a first magnetic coil sensor having a first axis and a second magnetic coil sensor having a second axis disposed on the distal end, wherein the first axis and the second axis are substantially... The system comprises: an upper parallel; and a processing circuit configured to receive electrical signals from the magnetic coil sensors, select at least one magnetic field having a magnetic field gradient based on at least one of the received electrical signals, calculate, based on the received electrical signals, the difference between the magnetic field magnitudes of the at least one selected magnetic field detected by the first magnetic coil sensor and the second magnetic coil sensor, and calculate the size of the distal end based on the calculated difference between the magnetic field magnitudes of the at least one selected magnetic field and the magnetic field gradient of the at least one selected magnetic field, the size of the distal end being a function of the distance between the magnetic coil sensors.

[0007] Further according to an embodiment of this disclosure, the calculated dimension is the distance between these magnetic coil sensors.

[0008] Further according to embodiments of this disclosure, the calculated dimension is the dimension of the shape of the distal end of the catheter.

[0009] Additionally, according to an embodiment of this disclosure, the processing circuit is configured to calculate the dimension of the distal end based on a calculated difference between the magnetic field magnitudes of the at least one selected magnetic field divided by the magnetic field gradient of the at least one selected magnetic field.

[0010] Furthermore, according to embodiments of this disclosure, the at least one selected magnetic field includes a magnetic field having the highest magnetic field gradient among these magnetic fields, and the processing circuit is configured to calculate the dimension of the distal end based on a calculated difference between the magnitudes of these magnetic fields of the at least one selected magnetic field and the highest magnetic field gradient.

[0011] Further according to an embodiment of the present disclosure, the catheter has a longitudinal axis; and the distal end of the catheter includes an expandable distal end assembly; the magnetic field sensors are configured to move relative to each other along the longitudinal axis of the catheter as the expandable distal end assembly expands and collapses; the distance between the magnetic coil sensors increases when the expandable distal end assembly collapses; and the distance between the magnetic coil sensors decreases when the expandable distal end assembly expands.

[0012] Further according to the embodiments of this disclosure, the first axis, the second axis, and the longitudinal axis are substantially coaxial.

[0013] Additionally, according to embodiments of this disclosure, the scalable distal end assembly is a basket-type distal end assembly, which includes a plurality of flexible strips and electrodes disposed on the flexible strips.

[0014] Furthermore, according to embodiments of this disclosure, the system includes a display, and wherein the processing circuitry is configured to obtain the shape of the distal end assembly based at least on the calculated dimensions, and to render a representation of the distal end assembly onto the display based on the obtained shape of the distal end assembly.

[0015] Further according to an embodiment of this disclosure, the calculated dimension is the distance between these magnetic coil sensors.

[0016] Further according to an embodiment of the present disclosure, the processing circuit is configured to: calculate the relative orientation between the first axis of the first magnetic coil sensor and the second axis of the second magnetic coil sensor; and estimate the shape of the distal end assembly based on the calculated relative orientation.

[0017] According to another embodiment of this disclosure, a medical method is also provided, comprising: generating magnetic fields having correspondingly different frequencies in a region of a body part of a living subject; inserting a catheter into the body part of the living subject; having magnetic coil sensors having substantially parallel axes disposed at a distal end of the catheter, outputting electrical signals according to the corresponding magnetic fields of the magnetic fields; and receiving the electrical signals from the magnetic coil sensors; selecting at least one magnetic field having a magnetic field gradient based on at least one of the received electrical signals; calculating, based on the received electrical signals, a difference between the magnetic field magnitudes of the at least one selected magnetic field detected by a first magnetic coil sensor and a second magnetic coil sensor; and calculating, based on the calculated difference between the magnetic field magnitudes of the at least one selected magnetic field and the magnetic field gradient of the at least one selected magnetic field, the size of the distal end being a function of the distance between the magnetic coil sensors.

[0018] Furthermore, according to embodiments of this disclosure, the calculated dimension is the distance between these magnetic coil sensors.

[0019] Furthermore, according to embodiments of this disclosure, the calculated dimension is the dimension of the shape of the distal end of the catheter.

[0020] Further according to an embodiment of the present disclosure, the calculation of the dimension includes: calculating the dimension of the distal end based on a calculated difference between the magnitudes of the at least one selected magnetic field and the magnetic field gradient of the at least one selected magnetic field.

[0021] Further according to embodiments of the present disclosure, the at least one selected magnetic field includes a magnetic field having the highest magnetic field gradient among these magnetic fields, and the calculation of the size includes: calculating the size of the distal end based on the calculated difference between the magnitudes of these magnetic fields of the at least one selected magnetic field and the highest magnetic field gradient.

[0022] Additionally, according to embodiments of this disclosure, the method includes moving the magnetic field sensors relative to each other along the longitudinal axis of the catheter as the expandable distal end assembly of the catheter expands and collapses.

[0023] Furthermore, according to the embodiments of this disclosure, the first axis, the second axis, and the longitudinal axis are substantially coaxial.

[0024] Further according to an embodiment of the present disclosure, the method includes: obtaining the shape of the distal end component based at least on the calculated dimensions, and rendering a representation of the distal end component to a display based on the obtained shape of the distal end component.

[0025] Further according to an embodiment of this disclosure, the calculated dimension is the distance between these magnetic coil sensors.

[0026] Additionally, according to embodiments of this disclosure, the method includes: calculating the relative orientation between the first axis of the first magnetic coil sensor and the second axis of the second magnetic coil sensor; and estimating the shape of the distal end assembly based on the calculated relative orientation. Attached Figure Description

[0027] The invention will be understood from the following detailed description taken in conjunction with the accompanying drawings, wherein:

[0028] Figure 1 This is a schematic diagram of a system for electroanatomical mapping according to an embodiment of the present invention, the system comprising a catheter;

[0029] Figure 2A A schematic diagram of the distal end of a basket catheter in a collapsed form;

[0030] Figure 2B For being in unfolded form Figure 2A A schematic diagram of the distal end of a basket catheter; and

[0031] Figure 3 For including Figure 1 The flowchart shows the steps in the system's operation method. Detailed Implementation

[0032] Overview

[0033] The system (manufactured by Biosense Webster, Inc., Irvine, California) employs Advanced Catheter Position (ACL) hybrid orientation tracking technology. In ACL technology, the distribution of measured currents associated with probe electrodes on the catheter is correlated with a current-position matrix (CPM), which maps the current distribution to the catheter's position previously acquired from magnetic position-calibrated orientation signals. ACL technology allows for the localization and visualization of catheters (even those without magnetic field sensors) only within the volume where the CPM has been calculated using catheters with magnetic coil sensors. A prerequisite for constructing the CPM is inserting a catheter equipped with a magnetic field sensor into the body and moving the catheter within the body's volume to calculate the CPM for that volume.

[0034] Additionally, ACL technology can be used to track basket catheters, which have electrodes on the basket. However, in some cases, ACL technology for measuring current or impedance may not provide sufficiently high accuracy.

[0035] One solution is to use signals from magnetic sensors mounted on the catheter to calculate the elongation of the expandable distal end-effector assembly (such as a basket-type or balloon-type distal end-effector assembly) based on the distance between the magnetic sensors. The magnetic sensors can be positioned on the catheter in such a way that the distance between the sensors provides an indication of the elongation and therefore shape of the distal end-effector assembly. Magnetic sensors generally provide more accurate orientation than using an ACL. However, the position measured by magnetic sensors is affected by errors on the order of millimeters (e.g., 2 mm or 3 mm), and in some applications these errors can even be excessive. For example, for a small basket-type catheter, the distance between the magnetic sensors can vary by about 10 or 15 mm between the basket collapsing and the basket expanding. Therefore, an error of 3 mm can be considered a large error. Errors can be reduced by using biaxial sensors (DAS) or triaxial sensors (TAS), which generally provide more accurate orientation measurements. However, in many applications, the catheter may not be able to accommodate two DAS or TAS, or even just one DAS or TAS. Detailed information on magnetic position sensing is provided in commonly owned U.S. Patents 5,391,199; 5,443,489, 5,558,091; 6,172,499; 6,690,963; 6,788,967; and 6,892,091, which are incorporated herein by reference, with copies provided in the appendix.

[0036] Embodiments of the present invention provide a system and method that use a magneto-based tracking technique to accurately calculate the dimensions of the distal end of a catheter (e.g., an expandable distal end assembly, such as a basket or balloon distal end assembly) based on two magnetic coil sensors and a magnetic field generator that generates corresponding (different frequencies) alternating magnetic fields for sensor detection. The magnetic field detected by the sensors indicates the orientation of the sensors in a given coordinate space.

[0037] The accuracy of the calculation is based on two factors: the positioning of the two magnetic coil sensors and an accurate error elimination calculation method.

[0038] The magnetic coil sensors are positioned along the longitudinal axis of the distal end of the conduit, such that the axes of the two sensors are substantially parallel, and in some embodiments, the two sensors are positioned substantially coaxial with the longitudinal axis. This allows the two sensors (e.g., relative to a magnetic field gradient) to sense different alternating magnetic fields in a similar manner, such that in the calculations described in more detail below, one alternating magnetic field can be used by both sensors, and error cancellation between the two sensors may be effective. As used in the specification and claims, the term "substantially parallel" is defined as parallel within a tolerance of 10 degrees. However, the closer the axes of the two sensors are to being perfectly parallel, the more accurate the calculations performed based on the sensor outputs will be. As used in the specification and claims, the term "substantially coaxial" is defined as the axes of the sensors being within 10 degrees of the longitudinal axis, and the area between the windings of the sensors intersecting the longitudinal axis.

[0039] Error cancellation calculation methods include calculating the corresponding magnetic field gradient (in a direction parallel to the sensor axis) of the corresponding magnetic field detected at the distal end (e.g., at one or more locations within the sensor). As used in the specification and claims, the term "magnetic field gradient" is defined as the variation of a magnetic field over a distance in a particular direction. In some embodiments, the approximate orientation of one or more magnetic field sensors can be calculated using any suitable method, and then, based on a known function of different magnetic fields in three-dimensional (3D) space, the magnetic field gradient (in a direction parallel to the sensor axis) at the distal end can be obtained for each magnetic field.

[0040] Select one magnetic field (e.g., the one with the highest magnetic field gradient). In some implementations, select a subset of magnetic fields (e.g., those with the highest magnetic field gradient) and calculate the average magnetic field gradient of the selected magnetic fields.

[0041] Calculate the difference between the magnitudes of the selected magnetic fields detected by the sensors. When a subset of magnetic fields is selected, calculate the average difference between the magnitudes of the selected magnetic fields detected by the sensors.

[0042] The distance between the sensors can then be calculated based on the (average) magnetic field gradient of the selected magnetic field and the (average) difference between the magnetic field magnitude of the selected magnetic field. In some implementations, the distance can be calculated by dividing the difference between the (average) magnetic field magnitudes of the selected magnetic fields by the (average) magnetic field gradient of the selected magnetic field. Another dimension of the distal end assembly can be calculated based on the calculated distance between the sensors. The shape of the distal end assembly can then be obtained using the distance and / or dimension, allowing a representation of the distal end assembly to be rendered to a display.

[0043] System Description

[0044] Now for reference Figure 1 This is a schematic illustration of a catheter tracking system 20 according to an embodiment of the present invention. System 20 includes a catheter 40 configured for insertion into a body portion of a living subject (e.g., patient 28). A physician 30 navigates the catheter 40 (e.g., a basket catheter manufactured by Biosense Webster Ltd., Irvine, CA, USA), shown in detail in illustration 45, to a target location in the heart 26 of patient 28 by manipulating a deflectable segment of the insertion cannula 22 of the catheter 40 and / or deflecting it from the sheath 23 using a manipulator 32 located near the proximal end 29 of the insertion cannula 22. In the illustrated embodiment, physician 30 uses the catheter 40 to perform electroanatomical mapping of the cardiac chambers.

[0045] The catheter 40 includes a distal end 33. The distal end 33 of the catheter 40 includes a component 35 (e.g., such as...). Figure 1 As shown in the basket-type or balloon-type assembly, multiple electrodes 48 (only some are labeled for simplicity) are disposed on the assembly. Assembly 35 is disposed on the distal side of insertion tube 22 and can be connected to insertion tube 22 at its distal end 33 via a connecting member of insertion tube 22. The connecting member of insertion tube 22 can be formed as an integral part of the rest of insertion tube 22 or as a separate element connected to the rest of insertion tube 22.

[0046] Component 35 also includes a plurality of flexible strips 55 (two are labeled for simplicity), with electrodes 48 coupled to each of the plurality of flexible strips. Component 35 may include any suitable number of electrodes 48. In some embodiments, component 35 may include 10 flexible strips 55 and 120 electrodes, with 12 electrodes disposed on each flexible strip 55.

[0047] The catheter 40 includes a actuator 37. The actuator 37 is typically a tube disposed within the lumen of the insertion tube 22 and extending from the proximal end 29 to the distal end 33 of the insertion tube 22. The distal end of the actuator 37 is typically connected to a first end of the flexible strip 55 via a connecting member of the actuator 37. The connecting member of the actuator 37 may be formed as an integral part of the remainder of the actuator 37 or as a separate element connected to the remainder of the actuator 37. The distal end of the insertion tube 22 is typically connected to a second end of the flexible strip 55 via a connecting member of the distal end 33. The actuator 37 is typically controlled via a manipulator 32 to deploy the assembly 35 and to change the ellipticity of the assembly 35 according to the longitudinal displacement of the actuator 37 relative to the insertion tube 22.

[0048] The actual basket assembly 35 structure can vary. For example, the flexible strip 55 can be made of a printed circuit board (PCB) or a shape memory alloy.

[0049] By way of example only, the embodiments described herein primarily relate to basket-type distal end-effector assembly 35. In alternative embodiments, the disclosed technology can be used with catheters having balloon-based distal end-effector assemblies or any other suitable type of distal end-effector assembly.

[0050] The catheter 40 is inserted through the sheath 23 in a folded configuration, and the catheter 40 can only be reshaped by the retraction pusher 37 after it has exited the sheath 23. By including the catheter 40 in the folded configuration, the sheath 23 also serves to minimize vascular trauma along its route to the target location.

[0051] The distal end 33 of the conduit 40 includes magnetic coil sensors 50A and 50B. Magnetic coil sensor 50A, shown in illustration 45, is located at the distal edge of the insertion tube 22 (i.e., at the proximal edge of the basket assembly 35). Sensor 50A can be a uniaxial sensor (SAS), or a DAS or TAS. Similarly, sensor 50B can be a SAS, DAS, or TAS. Magnetic coil sensors 50A and 50B, along with electrode 48, are connected to various drive circuits in the console 24 via wires passing through the insertion tube 22.

[0052] In some embodiments, system 20 includes a magnetic sensing subsystem to estimate the ellipticity of the basket assembly 35 of catheter 40 and its elongation / retraction state within the heart chambers of heart 26 by estimating the elongation of the basket assembly 35 from a distance between sensors 50A and 50B, as referenced. Figure 2B and Figure 3 More detailed description. The patient 28 is placed in a magnetic field generated by a pad comprising multiple magnetic field generator coils 42, which are driven by unit 43. The magnetic field generator coils 42 are configured to generate corresponding alternating magnetic fields with correspondingly different frequencies in regions of body parts (e.g., heart 26) of a living subject (e.g., patient 28). Magnetic coil sensors 50A and 50B are configured to output electrical signals based on the detection of corresponding magnetic fields. For example, if nine magnetic field generator coils 42 are present that generate nine correspondingly different alternating magnetic fields with nine correspondingly different frequencies, the electrical signal output by the magnetic coil sensor 50 will include components of the nine different frequency alternating magnetic fields. The magnitude of each magnetic field in the magnetic field varies with distance from the corresponding magnetic field generator coil 42, such that the position of the magnetic coil sensor 50 can be determined based on the magnetic field sensed by the magnetic coil sensor 50. Therefore, the transmitted alternating magnetic field generates electrical signals in sensors 50A and 50B, such that the electrical signals indicate the orientation and orientation of the magnetic coil sensor 50. Magnetic coil sensors 50A and 50B are referenced. Figure 2B A more detailed description was provided.

[0053] The generated signal is transmitted to console 24 and becomes a corresponding electrical input to processing circuit 41. Processing circuit 41 can use the signal to calculate the elongation of basket assembly 35 in order to estimate basket ellipticity and elongation / retraction state based on the calculated distance between sensors 50A and 50B, as described below. Figure 2B and Figure 3 A more detailed description is provided below; and the relative orientation between the axes of sensors 50A and 50B is calculated to estimate the shape of the scalable distal end assembly 35 (e.g., basket shape) based on the relative orientation, as described in more detail below.

[0054] The bending of the flexible strip 55 and / or the orientation of the electrode 48 (or other feature structure) on the flexible strip 55 relative to a fixed point on the conduit 44 (such as the distal end of the insertion tube 22) can be measured for various distances between the magnetic sensors 50A and 50B and for various relative orientation angles between the magnetic sensors 50A and 50B. For example, the orientation of the electrode 48 relative to a fixed point on the conduit 40 can be measured for every 0.2 mm movement of the actuator 37 relative to the insertion tube 22 and for every 1 degree of relative orientation between the magnetic sensors 50A and 50B (up to the maximum lateral movement of the assembly 35). At each different distance / relative orientation combination, the calculated distance and calculated relative orientation angle between the magnetic sensors 50A and 50B, along with the orientation data of the electrode 48, are recorded. This data can then be used to estimate the bending of the flexible strip 55 and / or the orientation of the electrode 48 (or other feature structure) on the flexible strip 55 relative to a fixed point on the conduit 40 (such as the distal end of the insertion tube 22) based on the calculated distance and relative orientation angle between the magnetic sensors 50A and 50B.

[0055] Alternatively, the bending of the flexible strip 55 can be estimated based on the following assumptions: (a) each flexible strip in the flexible strip 55 has a fixed and known length; (b) each flexible strip in the flexible strip 55 is connected to the actuator 37 via a connector, wherein the distal end of the flexible strip 55 is substantially perpendicular (within ±10 degrees of error) to the longitudinal axis 58; (c) each flexible strip in the flexible strip 55 is connected to the insertion tube 22 via a connector that connects the proximal end of the flexible strip 55 to the insertion tube 22, substantially parallel (within ±10 degrees of error) to the longitudinal axis 58 of the insertion tube 22. Based on the above assumptions (a)-(c), and the calculated orientation of the connector based on the orientation calculated by the magnetic sensors 50A, 50B, the bending of each flexible strip in the flexible strip 55 can be calculated using a cubic polynomial. In some embodiments, the bending of the flexible strip 55 and / or the orientation of the electrode 48 (or other feature structure) on the flexible strip 55 relative to a fixed point on the conduit 40 (such as the distal end of the insertion tube 22) can be calculated based on a calculated distance and orientation between magnetic sensors 50A, 50B and a model of the conduit 40, which provides the bending of the flexible strip 55 and / or the orientation of the electrode 48 for the calculated distance based on the mechanical properties and dimensions of the flexible strip 55.

[0056] Orientation and / or orientation sensing methods using external magnetic fields and magnetic coil sensors, such as sensors 50A and 50B, are implemented in various medical applications, for example, in the biosense-Webster product. The system is implemented and 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, PCT Patent Publication WO 96 / 05768 and U.S. Patent Application Publications 2002 / 0065455A1, 2003 / 0120150A1 and 2004 / 0068178A1.

[0057] Processing circuitry 41 (typically part of a general-purpose computer) is further connected via suitable front-end and interface circuitry 44 to receive signals from body surface electrodes 49. Processing circuitry 41 is connected to surface electrodes 49 via a wire extending through cable 39 to the chest of patient 28. Catheter 40 includes a connector 47 disposed at the proximal end 29 of insertion tube 22 for coupling to processing circuitry 41.

[0058] In some embodiments, based on the calculated azimuth coordinates of the insertion tube 22 and the flexible strip 55, the processing circuitry 41 (e.g., according to a mapping method or according to a scan of a body portion previously registered with system 20 (e.g., CT or MRI)) renders a representation 31 of at least a portion of the catheter 40 and the body portion onto a display 27, referencing... Figure 3 To describe in more detail.

[0059] The processing circuit 41 is typically programmed with software to perform the functions described herein. This software may be downloaded electronically to a computer via a network, or alternatively or additionally set and / or stored on a non-transitory tangible medium (such as magnetic storage, optical storage, or electronic storage).

[0060] Figure 1 The exemplary illustrations shown are chosen solely for the sake of conceptual clarity. For the sake of simplicity and clarity, Figure 1 Only elements relevant to the technology disclosed in this invention are shown. System 20 typically includes additional modules and elements that are not directly related to the technology disclosed in this invention and are therefore intentionally omitted from view. Figure 1 The corresponding descriptions are omitted. The elements of system 20 and the methods described herein can be further applied, for example, to control the ablation of tissues of the heart 26.

[0061] Now for reference Figure 2A and Figure 2B . Figure 2A This is a schematic diagram of the distal end 33 of the basket catheter 40 in a collapsed form. Figure 2B For being in unfolded form Figure 2A A schematic diagram of the distal end 33 of the basket catheter 40.

[0062] Component 35 is typically an expandable distal end assembly (e.g., a basket-type distal end assembly) comprising flexible strips 55 (some labeled for simplicity) circumferentially disposed around the distal portion 52 of the pusher 37, wherein a first end of the strip 55 is connected to the distal end 33 of the insertion tube 22 (e.g., a coupling member of the distal end 33) and a second end of the strip 55 is connected to the distal portion 52 of the pusher 37 (e.g., a coupling member of the distal portion 52). The flexible strips 55 are configured to bend radially outward when the pusher 37 retracts. A plurality of electrodes 48 (some labeled for simplicity) are disposed on each of the flexible strips 55.

[0063] Magnetic coil sensor 50A is a coil-based orientation sensor disposed at the distal end 33 of the insertion tube 22, for example, in a connecting member at the distal end 33. Magnetic coil sensor 50A includes a coil 54A having an axis 56A. Magnetic coil sensor 50B is a coil-based orientation sensor disposed on the distal portion 52 of the actuator 37, for example, in a connecting member of the distal portion 52, connecting the distal end of the flexible strip 55 to the actuator 37. Magnetic coil sensor 50B includes a coil 54B having an axis 56B. The distal end 33 of the conduit 40 has a longitudinal axis 58. Magnetic coil sensors 50A and 50B are disposed on the distal end 33, wherein axis 56A and axis 56B are substantially parallel. In some embodiments, axis 56A, axis 56B, and longitudinal axis 58 are substantially coaxial.

[0064] The actuator 37 is configured to advance and retract through the insertion tube 22. Magnetic field sensors 50A and 50B are configured to move relative to each other along the longitudinal axis 58 of the conduit 40 as the expandable distal end assembly 35 expands and collapses. When the expandable distal end assembly 35 collapses, the distance d between the magnetic coil sensors 50A and 50B increases, and when the expandable distal end assembly 35 expands (i.e., extends), the distance d between the magnetic coil sensors 50A and 50B decreases.

[0065] Each sensor 50A, 50B can be SAS, DAS, or TAS. Sensors 50A and 50B can be the same type of sensor or different types of sensors. If both sensors 50A and 50B are uniaxial sensors, the conduit 40 typically includes another orientation sensor to track the roll of assembly 35.

[0066] See now Figure 3 It includes Figure 1 Flowchart 100 of the steps in the operation method of system 20. See also: Figure 2B .

[0067] As previously mentioned, magnetic coil sensors 50A and 50B are configured to output electrical signals due to the inductive effect of each coil in response to a corresponding magnetic field. For example, if there are nine magnetic field generator coils 42 generating nine corresponding different alternating magnetic fields with nine corresponding different frequencies, the electrical signal output by the magnetic coil sensor 50 will include components of the nine corresponding different frequency alternating magnetic fields. The magnitude of each magnetic field varies with the distance from the corresponding magnetic field generator coil 42, such that the position of the magnetic coil sensor 50 can be determined based on the magnetic field sensed by the magnetic coil sensor 50. Therefore, the transmitted alternating magnetic field generates electrical signals in sensors 50A and 50B, such that the electrical signals indicate the position and orientation of the magnetic coil sensor 50. Processing circuitry 41 is configured to receive electrical signals from magnetic coil sensors 50A and 50B (block 102).

[0068] Processing circuit 41 is configured to calculate the magnetic field detected by magnetic coil sensors 50A and 50B, and the corresponding magnetic field gradient (e.g., a direction parallel to the axes 56A, 56B of coils 54A, 54B) of the corresponding magnetic field detected at the distal end 33 (block 104). That is, processing circuit 41 calculates the magnetic field and associated magnetic field gradient based on at least one electrical signal received by circuit 41 from one or more of the magnetic coil sensors 54A and 54B. In some embodiments, the approximate orientation (position and orientation) of one or more of the magnetic field sensors 50A, 50B can be calculated using any suitable method, and then, based on a known function of the different magnetic fields in three-dimensional (3D) space, the magnetic field gradient at the distal end 33 (e.g., a direction parallel to the axes 56A, 56B of coils 54A, 54B) can be obtained for each magnetic field. The orientation of the distal end 33 can be calculated based on the average orientation of the magnetic coil sensors 50A and 50B or based on the most accurate sensor among the magnetic coil sensors 50A and 50B. For example, if sensor 50B is a DAS or TAS, the position and orientation of sensor 50B can be calculated based on all or some of the sensing coils of that sensor.

[0069] Processing circuit 41 is configured to select a magnetic field (block 106) having a corresponding magnetic field gradient from the calculated magnetic field gradient. In some embodiments, the selected magnetic field has the highest calculated magnetic field gradient (i.e., the magnetic field with the highest gradient is selected). The highest magnetic field gradient generally indicates that the selected magnetic field will provide the highest sensitivity in the direction parallel to the axes 56A, 56B of the coils 54A, 54B of the magnetic coil sensors 50A, 50B, and therefore will provide the highest accuracy in calculating the distance d between the sensors 50A, 50B.

[0070] In some embodiments, processing circuit 41 is configured to select a subset of magnetic fields (e.g., the one with the highest magnetic field gradient) and calculate the average magnetic field gradient of the selected magnetic fields. Therefore, processing circuit 41 is configured to select at least one magnetic field having a magnetic field gradient (e.g., the average calculated magnetic field gradient) based on at least one electrical signal received from the coil by circuit 41 (which is used to calculate the magnetic field and the magnetic field gradient of the corresponding magnetic field). Processing circuit 41 is configured to calculate the difference between the magnetic field magnitudes (e.g., the magnetic field with the highest gradient) of the selected magnetic field detected by magnetic coil sensor 50A and magnetic coil sensor 50B (box 108). For example, if the magnetic field magnitude of the selected magnetic field detected by magnetic coil sensor 50A is equal to B1 and the magnetic field magnitude of the selected magnetic field detected by magnetic coil sensor 50B is equal to B2, then the difference between the magnetic field magnitudes (e.g., the magnetic field with the highest gradient) of the selected magnetic field detected by magnetic coil sensor 50A and magnetic coil sensor 50B is equal to B2 minus B1.

[0071] In some implementations, when a subset of magnetic fields is selected, the processing circuit 41 is configured to calculate the difference (which is an average difference) between the magnitudes of the selected magnetic fields (e.g., the magnetic field with the highest gradient) detected by magnetic coil sensors 50A and 50B. For example, if the average magnitude of the selected magnetic field detected by magnetic coil sensor 50A is equal to B3 and the average magnitude of the selected magnetic field detected by magnetic coil sensor 50B is equal to B4, then the average difference between the magnitudes of the selected magnetic fields (e.g., the magnetic field with the highest gradient) detected by magnetic coil sensors 50A and 50B is equal to B4 minus B3.

[0072] Processing circuit 41 is configured to calculate the size of the distal end 33 based on a calculated difference (e.g., average difference) between the magnetic field magnitudes of the selected magnetic fields (e.g., B2 minus B1 or B4 minus B3) and a corresponding calculated magnetic field (average) gradient (e.g., the highest calculated magnetic field gradient) of the selected magnetic field, the size of which is a function of the distance d between the magnetic coil sensors 50A and 50B (block 110). In some embodiments, processing circuit 41 is configured to calculate the size of the distal end 33 based on a calculated (average) difference (e.g., B2 minus B1 or B4 minus B3) between the magnetic field magnitudes of the selected magnetic fields divided by a corresponding calculated (average) magnetic field gradient (e.g., the highest calculated magnetic field gradient) of the selected magnetic field. The calculated size may be the distance between the magnetic coil sensors 50A, 50B. In some embodiments, the calculated size is the shape of the distal end 33 of the conduit, for example, the distance between the proximal and distal points of the distal end assembly 35 or the circumference of the assembly 35 at the equator. Processing circuit 41 is configured to obtain (e.g., by calculation or from a lookup table) the shape of the distal end assembly 35 as a derivative of the calculated dimensions (box 112). Processing circuit 41 is optionally configured to calculate the relative orientation between the axes of sensors 50A and 50B to estimate or derive the shape of the expandable distal end assembly 35 (e.g., a basket shape) based on the relative orientation. Processing circuit 41 is configured to render a representation 31 of the distal end assembly 35 to display 27 as a derivative of the obtained shape of the distal end assembly 35. Figure 1 (Box 114). A technique for deriving the shape of an scalable distal end assembly 35 based on the distance between magnetic position sensors is described in U.S. Patent Application 16 / 854538 (Attorney’s File No. BIO6130USNP), filed April 21, 2020, which is incorporated herein by reference, a copy of which is attached to the appendix.

[0073] As used herein, the term “about” or “approximately” for any numerical value or range indicates a suitable dimensional tolerance that allows a collection of parts or components to achieve the intended purpose as described herein. More specifically, “about” or “approximately” may refer to a range of ±20% of the enumerated value; for example, “about 90%” may refer to a range of values ​​from 72% to 108%.

[0074] For clarity, the various features of the invention described in the context of individual embodiments may also be provided in combination in a single embodiment. Conversely, for brevity, the various features of the invention described in the context of individual embodiments may also be provided individually or in any suitable sub-combination.

[0075] The above embodiments are cited by way of example, and the invention is not limited to the specific examples shown and described above. Rather, the scope of the invention includes combinations and sub-combinations of the various features described above, as well as variations and modifications thereof, which will occur to those skilled in the art upon reading the above description and are not disclosed in the prior art.

Claims

1. A medical system comprising: A generator coil, the generator coil being configured to generate corresponding magnetic fields with different frequencies in regions of a body part of a live subject; A catheter, which can collapse and expand between a collapsed and expanded form along its longitudinal axis, and is configured to connect to an insertion tube of an expandable distal end assembly, and A magnetic coil sensor, configured to output an electrical signal in response to a corresponding magnetic field, the magnetic coil sensor comprising: A first magnetic coil sensor having a first axis, the first magnetic coil sensor being disposed on the distal end of the insertion tube, and A second magnetic coil sensor with a second axis is disposed on a push tube inside an expandable distal end assembly, and the respective axes of the first and second magnetic coil sensors are substantially parallel to each other. A first magnetic coil sensor and a second magnetic coil sensor are configured to move relative to each other along the longitudinal axis of the conduit during the expansion and collapse of the expandable distal end assembly, such that (i) the distance between the first magnetic coil sensor and the second magnetic coil sensor increases when the expandable distal end assembly collapses toward a collapsed form, and (ii) the distance between the first magnetic coil sensor and the second magnetic coil sensor decreases when the expandable distal end assembly expands toward an expanded form; and A processing circuit configured to receive the electrical signal from the magnetic coil sensor; Select at least one magnetic field having a magnetic field gradient defined by at least one of the received electrical signals; Calculate the difference between the magnitudes of at least one selected magnetic field detected by the first magnetic coil sensor and the second magnetic coil sensor based on the received electrical signal; and The size of the scalable distal end assembly is calculated based on the calculated difference between the magnetic field magnitudes of the at least one selected magnetic field and the magnetic field gradient of the at least one selected magnetic field, the size of the distal end being a function of the distance between the magnetic coil sensors.

2. The medical system according to claim 1, wherein, The calculated dimension is the distance between the first and second magnetic coil sensors.

3. The medical system according to claim 1, wherein, The calculated dimensions are the dimensions of the shape of the expandable distal end assembly of the catheter.

4. The medical system according to claim 1, wherein, The processing circuit is configured to calculate the size of the expandable distal end assembly by dividing a calculated difference between the magnetic field magnitudes of the at least one selected magnetic field by the magnetic field gradient of the at least one selected magnetic field.

5. The medical system according to claim 1, wherein: The at least one selected magnetic field includes a magnetic field having the highest magnetic field gradient among the magnetic fields; and The processing circuit is configured to calculate the size of the expandable distal end based on a calculated difference between the magnetic field magnitudes of the at least one selected magnetic field and the highest magnetic field gradient.

6. The medical system according to claim 1, wherein, The first axis and the second axis are substantially parallel in the collapsed form.

7. The medical system according to claim 6, wherein, The first axis, the second axis, and the longitudinal axis are substantially coaxial.

8. The medical system according to claim 6, wherein, The scalable distal end assembly is a basket-type distal end assembly, which includes a plurality of flexible strips and electrodes disposed on the flexible strips.

9. The medical system of claim 6, further comprising a display, and wherein the processing circuitry is configured to: obtain the shape of the distal end assembly based at least on the calculated dimensions; and Based on the obtained shape of the distal end component, the representation of the distal end component is rendered onto the display.

10. The medical system according to claim 9, wherein, The calculated dimension is the distance between the magnetic coil sensors.

11. The medical system according to claim 1, wherein, The processing circuit is configured to: Calculate the relative orientation between the first axis of the first magnetic coil sensor and the second axis of the second magnetic coil sensor; and The shape of the distal end assembly is estimated based on the calculated relative orientation.

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