Magnetic based sheath detection

Abstract

A method includes receiving electrical signals from a plurality of coils embedded in a distal end assembly of a catheter delivered via a sheath inserted into a body of a patient, the electrical signals being received in response to application of an external magnetic field to the distal end assembly. A change in a value of an electrical signal output by a distal coil of the plurality of coils is determined. Based on a change in the value of the electrical signal, it is determined whether the distal end assembly is in a collapsed state within the sheath or has begun to be exposed from the sheath and the distal coil is in an at least partially expanded state outside the sheath. In response to detecting a change in the value, the value of the electrical signal from the distal coil is used to determine the position of the distal end of the sheath within the body.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to invasive medical probes, and in particular to estimation of the location of the distal end of a delivery sheath for an invasive medical probe within a human body. BACKGROUND

[0002] Techniques for determining the location and / or status of a probe have been previously presented in the patent literature. For example, U.S. Patent Application Publication 2019 / 0343423 describes a catheterization procedure by inserting a sheath into a human patient and moving a catheter having electrodes through the sheath lumen. A change in current through the electrodes between a first threshold and a second threshold is identified. In response to the change, it is reported that a portion of the catheter has transitioned between a sheath-in status and a sheath-out status. The sheath is defined and identified by historical data of readings of a magnetic sensor of the catheter during its movement.

[0003] The present disclosure will become more fully understood from the detailed description of embodiments thereof, referred to herein below and illustrated in the accompanying drawings, wherein: BRIEF DESCRIPTION OF DRAWINGS

[0004] Figure 1 is a schematic illustration of a catheter-based electroanatomical (EA) mapping and ablation system in accordance with examples of the present disclosure;

[0005] Figure 2A and Figure 2B is an illustration schematically showing a three-coil layout and a six-coil layout for a flat catheter in accordance with some examples of the present disclosure;

[0006] Figure 3 is a flowchart schematically showing a method and algorithm for detecting the location of the distal end of a sheath using a flat catheter assembly deployment in accordance with examples of the present disclosure; Figure 1 is a front view of the flat catheter assembly of

[0007] Figure 4A , Figure 4B and Figure 4C is a perspective view of the flat catheter assembly of Figure 1 in three schematic views: located within the distal end of the sheath, partially deployed outside the sheath, and fully deployed outside the sheath, respectively, in accordance with examples of the present disclosure;

[0008] Figure 5 is a flowchart schematically showing a method and algorithm for detecting the location of the distal end of a sheath using a flat catheter assembly deployment in accordance with examples of the present disclosure;

[0009] Figure 6 is a perspective view of the flat catheter assembly of Figure 1 (also referred to as an "end effector of a planar catheter") in accordance with examples of the present disclosure; and

[0010] Figure 7 is included in accordance with examples of the present disclosure Figure 6 illustration of a catheter assembly including an end effector. DETAILED DESCRIPTION

[0011] SUMMARY

[0012] Diagnostic and therapeutic catheters are often delivered through a sheath. Optimal deployment of the catheter can depend on the location of the distal edge of the sheath, i.e., where the catheter is located. However, since the sheath is typically a simple flexible tube without navigation means, it can be difficult to determine the location of the distal end of the sheath within the body (e.g., within the heart).

[0013] Examples of the present disclosure described below provide a technique that exploits special layouts of magnetic position sensors (e.g., coils) on a flat catheter that have unique spatial symmetries of the coil sets to (i) determine the location of the distal end of the sheath within the body during deployment of the catheter assembly outside the sheath, and (ii) determine the state of the catheter deployment (e.g., whether the catheter is still within the sheath, partially deployed outside the sheath, or fully deployed outside the sheath). Using this real-time information can allow the physician to optimize the catheter deployment (e.g., decide whether the location of the distal end of the sheath in the organ is most suitable for proceeding with the full deployment of the catheter assembly).

[0014] The disclosed catheter has a flat distal end assembly formed of certain self-expanding materials (such as flexible PCB) that includes three or more flat magnetic coils (e.g., wire ferrules) embedded in the flexible PCB. The magnetic ferrules pick up magnetic drive signals generated by a localization pad of a localization tracking system (e.g., a localization pad located under the patient) and output corresponding electrical signals.

[0015] When the distal end assembly is within the sheath and wrapped around its longitudinal axis, it generates pick-up signals from the magnetic sensors that are not suitable as position indication signals. However, the authors found that the almost symmetrical coil layout generated by the wrapped configuration makes these signals satisfy certain relationships that indicate that the flat assembly is either fully wrapped or partially wrapped outside the sheath.

[0016] Specifically, the authors point out that when the flat distal end assembly is slightly advanced beyond the distal end of the sheath, at least one distal coil outputs a signal that changes compared to its output when it is wrapped within the sheath. The processor of the tracking system uses the changed signal to determine the location of the distal end of the sheath within the body with certain precision (e.g., a few millimeters). To this end, the changed signal should have a value similar to (e.g., almost as large as) a standard corresponding position signal, although it will typically be different from the value of the fully deployed coil.

[0017] When the assembly is fully deployed (e.g., outside the sheath in its self- expanded shape), all coils output standard position-indicative signals. The position tracking system uses these signals to accurately determine the position of the distal end assembly in the body.

[0018] In one example, when the catheter is being delivered through the sheath, the processor of the tracking system receives signals from three magnetic sensors (e.g., X, Y named side collars, Z named distal collar, as shown) disposed on the flat distal end assembly of the catheter. The system monitors in real time the changes in the output of each of the three magnetic collars on the assembly. Figure 2A

[0019] When the distal end assembly is inside the sheath in its coiled configuration, the parts of any two side collars (X, Y) face each other around any external magnetic field direction. Therefore, the output signals (SX, SY) of the side collars (X, Y) are equal in magnitude but opposite in sign: SX = -SY. The signal output SZ of the distal collar Z is approximately zero due to its substantially asymmetric spatial layout with respect to the magnetic field direction, where each contribution of one of its parts is canceled by the respective part facing it with respect to the magnetic field.

[0020] More generally, the correspondence of the signals (SX, SY, and SZ) inside the sheath can be written as SZ = ε, SX = ε + A, and SY = ε - A, where ε is small or zero. As long as this relation is maintained, the processor can determine that the flat distal end assembly is coiled and therefore must be in the sheath.

[0021] When the flat distal end assembly is slightly out of the distal end of the sheath, the distal collar Z starts to self-expand into its expanded flat shape, and the output SZ of the distal collar Z becomes greater than a predefined threshold (e.g., greater than 25ε). At this point, the positioning system can use the position indication obtained from the distal collar to estimate the position of the distal end of the sheath in the body (e.g., inside the heart).

[0022] When the flat assembly is fully deployed, all collars are in the self-expanded flat shape. In this state, the signs of the side collars signals (SX, SY) are no longer opposite, and at this point, the position indication of the assembly obtained using the three collars is very accurate.

[0023] System Description

[0024] Figure 1 ​is a schematic illustration of a catheter-based electroanatomical (EA) mapping and ablation system 10 according to examples of the present disclosure; the system 10 includes a delivery sheath 37 inserted by a physician 24 via the skin into the vasculature of a patient to a chamber or vascular structure of a heart 12. Thereafter, a flat catheter 14 (shown in inset 45) is inserted into the delivery sheath 37 to be deployed outside the sheath 37 (e.g., in the blood pool of a heart chamber 33) and then advanced to a desired tissue location.

[0025] In Figure 1 the physician 24 advances a flat-type inflatable distal end assembly 28 (hereinafter also referred to as “inflatable distal end assembly 28”) fitted on a shaft 44 of the catheter 14 into contact with the heart wall to EA sense a target site in the heart 12.

[0026] As shown in inset 65, the flat assembly 28 includes a plurality of functional electrodes 26, which are optionally distributed on a plurality of splines 22 at the inflatable distal end assembly 28 and configured to sense IEGM signals. The assembly 28 has a longitudinal axis 42, which is parallel to a distal end 46 of the shaft 44 and is an axis of symmetry of the assembly 28.

[0027] The assembly 28 includes a magnetic position sensor 29, which includes Figure 2A three coils as shown in inset 67. The coils are embedded in the splines 22 and used to track the position and / or orientation of the inflatable distal end assembly 28. One of the coils is positioned closer to a distal edge 16 of the assembly 28 and is thus named “distal coil”. The magnetic position sensor 29 operates with an external localization pad 25, which includes a plurality of magnetic coils 32 configured to generate magnetic fields in a predefined workspace. Using the operation with the external localization pad 25 (each coil uses a different frequency), a processor can determine the position of the sensor 29 on a coordinate system of the position tracking system.

[0028] Details of the magnetic-based position sensing technology are described in U.S. Patents Nos. 5,5391,199; 5,443,489; 5,558,091; 6,172,499; 6,239,724; 6,332,089; 6,484,118; 6,618,612; 6,690,963; 6,788,967; and 6,892,091.

[0029] The system 10 includes one or more electrode patches 38 positioned in contact with the skin of the patient 23 to establish a positional reference for impedance-based tracking of the positioning pad 25 and the functional electrodes 26. For impedance-based tracking, current is directed toward the electrodes 26 and sensed at the electrode skin patches 38, such that the location of each electrode can be triangulated via the electrode patches 38.

[0030] Details of impedance-based position tracking technology are described in U.S. Patent Nos. 7,536,218; 7,756,576; 7,848,787; 7,869,865; and 8,456,182.

[0031] The recorder 11 displays electrograms 21 captured with the body surface ECG electrodes 18 and intracardiac electrograms (IEGMs) captured with the functional electrodes 26 of the catheter 14. The recorder 11 can include pacing capability for pacing cardiac rhythms and / or can be electrically connected to a separate pacemaker.

[0032] The system 10 can include an ablation energy generator 50 adapted to conduct ablation energy to a subset of the plurality of electrodes 26 at the distal assembly 28 of the catheter 14 configured for ablation. The energy generated by the ablation energy generator 50 can include, but is not limited to, radiofrequency (RF) energy or pulsed field ablation (PFA) energy (including monopolar or bipolar high-voltage DC pulses that can be used to implement irreversible electroporation (IRE)), or combinations thereof.

[0033] A patient interface unit (PIU) 30 is configured to establish electrical communication between the catheters, electrophysiology equipment, power sources, and a workstation 55 for controlling operation of the system 10. The electrophysiology equipment of the system 10 can include, for example, the plurality of catheters, the positioning pad 25, the body surface ECG electrodes 18, the electrode patches 38, the ablation energy generator 50, and the recorder 11. Optionally and preferably, the PIU 30 additionally includes processing capability for implementing real-time computation of catheter position and for performing ECG computation.

[0034] The workstation 55 includes a memory 57, a processor unit 56 with a memory or storage device loaded with appropriate operating software therein, and user interface capabilities. The workstation 55 can provide a number of functions, optionally including: (i) three-dimensional (3D) modeling of the endocardial anatomy, and rendering of the model or anatomic map 20 for display on the display device 27; (ii) display of activation sequences (or other data) compiled from the recorded electrograms 21 on the display device 27 as representative visual markers or images superimposed on the rendered anatomic map 20; (iii) display of real-time position and orientation of the plurality of catheters within the heart chamber; and (iv) display of sites of interest (such as where ablation energy has been applied) on the display device 27. One commercial product embodying elements of the system 10 is the CARTO® System, available from Biosense Webster, Inc., 31 A Technology Drive, Irvine, CA 92618. TM 3 System available from Biosense Webster, Inc., 31 A Technology Drive, Irvine, CA 92618.

[0035] Flat catheter coil layout

[0036] Figure 2A and Figure 2B are illustrations schematically showing a three-loop layout 283 and a six-loop layout 286 for a flat catheter, in accordance with some examples of the present disclosure.

[0037] Figure 2A The layout 283 of the three (X, Y, Z) loops (291, 292, 293) of the sensors 29 of the distal tip assembly 28 is further described in Figure 3 and FIG. 4. As shown, the layout includes a first side loop (291) and a second side loop (292) on respective first and second sides of the distal tip assembly, and a distal loop 293.

[0038] When the distal tip assembly is coiled within the sheath, the collars (291, 292, 293) are coiled on the longitudinal axis 42 and form a generally asymmetric spatial layout around the magnetic field direction.

[0039] When the flat distal tip assembly is slightly out of the distal end of the sheath, only the distal collar Z begins to self-expand into its deployed flat shape.

[0040] When the flat assembly is fully deployed, the side collars also self-expand into the flat shape.

[0041] Figure 2B The layout 286 of the six (M, N, O, P, R, S) loops 296 is shown. A greater number of loops can allow the position tracking system to determine the deployed state of the catheter outside the sheath in more detail.

[0042] Figure 3 is a schematic illustration of a flat catheter assembly 28 according to an example of the present disclosure. Figure 1 is a front view of the flat catheter assembly 28 of As shown, the flat assembly 28 is wound about a longitudinal axis 42 with the side loops 291 and 292 showing a facet opposite any magnetic field. This causes their pickup signals SXand SYto approximately satisfy the relationship SX= -SY.

[0043] The two portions 293a and 293b of the distal coil 293 also approximately show a facet opposite any magnetic field. This causes the coil 293 pickup signal SZto approximately satisfy the relationship SZ= ε (e.g., ε ~ 0).

[0044] Magnetic based sheath detection using flat catheter deployment

[0045] Figure 4A , Figure 4B and Figure 4C are schematic illustrations of the flat catheter assembly 28 of Figure 1 according to an example of the present disclosure: located within a distal end of a sheath 37, partially deployed outside the sheath 37, and fully deployed outside the sheath 37, respectively.

[0046] Table 1 below lists the signal values or relationships output / preserved by the coils (291, 292, and 293) in any of the three deployment configurations of Figures 4A-4C the flat catheter assembly 28 of

[0047] DRAWINGS Assembly deployment phase On collar Side collar 4A Inside sheath SZ = ε SX = -SY 4B Partially outside sheath SZ ≠ ε SX = -SY 4C Outside sheath SZ ≠ ε SX ≠ -SY

[0048] Table 1

[0049] Figure 4A is a schematic illustration of when wound within the sheath 37, the side coils 291 and 292 face each other, thereby producing pickup signals of approximately equal magnitude but opposite sign. Meanwhile, the two sides of the distal coil 293 also face each other, thereby producing a pickup signal of approximately zero.

[0050] Figure 4B is a schematic illustration of when the assembly 28 is partially wound within the sheath 37 (i.e., partially outside the sheath 37), the side coils 291 and 292 still face each other, thereby producing pickup signals of approximately equal magnitude but opposite sign. Meanwhile, the distal coil 293 has partially inflated to its flat shape outside the sheath edge 437, so the coil 293 produces an approximately true position signal SZ.

[0051] Figure 4CThe assembly 28 is shown schematically in its self-expanding flat shape entirely outside the sheath 37. In this case, the side coils 291 and 292 are expanded outside the sheath edge 437 and generate different true position signals (e.g., position signals of different amplitudes but same sign). The distal coil 293 is in its self-expanding flat shape and generates the true position signal SZ.

[0052] Method of magnetic based sheath detection using flat catheter deployment

[0053] Figure 5 is a flowchart schematically showing a method and algorithm for detecting the position of the distal end of the sheath 37 using the flat catheter assembly 28 deployment according to an example of the present disclosure. According to the present example, the algorithm performs a process that starts at a signal receiving step 502, where the processor 56 receives electrical signals output by the side coils (291, 292) and the distal coil 293 of the assembly 28 that are coiled within the sheath 37 as the assembly is advanced within the sheath 37.

[0054] At a signal relationship monitoring step 504, the processor 56 monitors in real-time the relationship between the values of the electrical signals received from the side coils 291 and 292 and the signal from the distal coil 293 in step 502, such as monitoring that these signals satisfy the entries given in Table 1 for Figure 4A as the catheter is in its coiled configuration within the sheath.

[0055] At a signal value change detection step 506, the processor detects a change in the value of the electrical signal output by the distal coil 293 that is indicative of a change in shape of the flat assembly 28 as it starts to exit the sheath 37. The amount of change detected is given in Table 1 for Figure 4B as the distal coil 293 is partially outside the sheath and has at least a partially self-expanding shape and a corresponding new entry.

[0056] At a sheath position estimation step 508, the processor estimates the position of the distal end of the sheath 37 in the body using the first substantial (e.g., greater than a predefined threshold) position signal from the distal coil 293 that is at least partially self-expanding.

[0057] Next, at a signal relationship change detection step 510, the processor detects a change in the relationship between the signals from the coils (291, 292) that is indicative of a further change in shape of the flat assembly. For the flat catheter assembly 28, this corresponds to detecting a change that is indicative of all the distal coils (291, 292, and 293) being fully deployed outside the sheath, where the corresponding new relationship is given in Table 1 for Figure 4C as the distal coil 293 is partially outside the sheath and has at least a partially self-expanding shape and a corresponding new entry.

[0058] At assembly position estimation step 512, the processor uses the position signals from all three coils to estimate the position of the flat assembly 28 within the body. This initial estimate can also be used to validate the sheath 37 position estimate of step 508.

[0059] Figure 5 The example flowchart shown in FIG. 6 is greatly simplified for conceptual clarity. Additional intermediate steps (e.g., changes in relationships) can be considered depending on coil layout and workflow. Additional steps can also include moving the sheath to a more optimal position before fully deploying the assembly 28 if the distal end position of the sheath (determined in step 508) is deemed unusable to retract the catheter into the sheath 37.

[0060] Bilaterally packaged planar catheter

[0061] Figure 6 is in accordance with an example of the present disclosure Figure 1 A perspective view illustration of a flat catheter assembly 28 (also referred to as "end effector 100 of a planar catheter") in accordance with an example of the present disclosure. The dual-sided end effector 100 is coupled to a catheter shaft 90. Importantly, the end effector 100 has an overall flat profile and is provided with electrodes 160 on both of its opposing (along axis V-V) planar facets (e.g., on tines 106). The two opposing facets can be identical or different in layout.

[0062] A plurality of pairs of electrodes 160 can be provided on the flexible circuit disposed on both opposing facets of the end effector 100, the electrodes being spaced apart by a first predetermined longitudinal distance Dl, and each pair of electrodes 160 being spaced apart from an adjacent pair of electrodes 160 by a second predetermined longitudinal distance D2, the second predetermined longitudinal distance D2 being greater than the first predetermined longitudinal distance Dl.

[0063] The electrodes 160 can sense tissue signals or transmit energy (AC or DC) from an energy generator to tissue. At least a portion of the electrodes 160 can be axially aligned, orthogonal to the longitudinal axis L-L, and at least one location of the electrodes defines a pair of opposing electrodes.

[0064] The end effector 100 can include a frame 120, a non-conductive flexible layer 130, and flexible circuits 110 and 150. A continuous block of flexible non-conductive material 130 can have portions 132 removed. Portions 132 can also be formed in one or all of the flexible circuit and frame 120. Portions 132 can pass through all layers of the multi-layer end effector 100, or only some of the layers. Portions 132 can be included to increase the ability of the end effector 100 to fold or bend into a reduced delivery configuration to allow the end effector 100 to pass through a delivery catheter.

[0065] The flexible circuit 110 and 150 can extend along a longitudinal axis L-L from the proximal portion 102 to the distal portion 104 of the end effector 100 and each can include two opposing faces. The frame 120 can include two opposing sides and can extend along a longitudinal axis L-L that is generally parallel to the flexible circuits 110 and 150. The non-conductive flexible layer 130 can at least partially encapsulate the first flexible circuits 110 and 150 and the frame 120.

[0066] In some examples, the flexible circuit layers 110 and 150 can be made primarily of polyimide. In other examples, they can be made of any of biocompatible polyimide, glass reinforced epoxy laminate, copper, or graphene, alone or in combination. The flexible circuit layers can include conductive traces.

[0067] The end effector 100 includes a position sensing coil layer 140 that includes a plurality of coils, such as coils (291, 292, 293) that are placed generally parallel to the frame 120 and are separated from the frame 120 by another of the non-conductive flexible layers 130. In some examples, the coils can be co-planar. Figure 2A

[0068] For the entire end effector, far field signals (including noise or artifacts) can be reduced or eliminated with the reference electrodes 161a and 161b disposed on two opposing sides near the proximal base 102 of the frame 100 such that the reference electrodes are not in contact with tissue but only with blood. The reference electrodes 161 are preferably exposed to the surrounding blood environment but can be encapsulated in a polymer such that the reference electrodes are not exposed through the non-conductive layer.

[0069] Irrigation can be provided through two irrigation ports 163a and 163b (one on each side) that are in fluid communication with an irrigation line (not shown) disposed in the catheter shaft 90. Instead of an irrigation line separate from the catheter shaft 90, a lumen can be created via squeezing the catheter shaft 90 to provide a lumen passageway. Note that the ports 163 can be configured to have sufficient flow diverter properties to cover the electrodes with irrigation fluid during an irrigation flow in order to prevent or reduce thrombus formation.

[0070] Details of the electrode spacing can be found in U.S. Provisional Patent Application S.N. 63 / 406,673 (Attorney Docket No. BIO6749USPSP3), filed September 14, 2022, which is incorporated by reference in its entirety into the present application as set forth in full in the Appendix to the priority application, U.S. Provisional Patent Application No. 63 / 505,764 (Attorney Docket No. 253757.000380BIO6846USPSP1), filed June 2, 2023. The present invention provides a system as​Figure 7 The catheter assembly 200 shown, which can include a tubular member 230 (also referred to as a "shaft" 230) extending along a longitudinal axis L-L and configured to deliver the end effector 100 outside of a sheath 210. The physician 24 can manipulate the catheter 200 with a handle 220. Suitable examples of the catheter assembly 200 and its subcomponents, such as the handle 220, the sheath 210, the tubular member 230, and other components not mentioned herein, are described in U.S. Patent Publication No. 2021 / 0369339, which is incorporated by reference in its entirety into the present application as set forth in full in the Appendix of the priority application filed on June 2, 2023, U.S. Provisional Patent Application 63 / 505,764 (Attorney Docket No. 253757.000380BIO6846USPSP1).

[0071] EMBODIMENTS

[0072] EMBODIMENT 1

[0073] A method comprising: receiving electrical signals from a plurality of coils (291, 292, 293) embedded in a distal end assembly (28, 283) of a catheter (14) delivered via a sheath (37) inserted into a body of a patient, the electrical signals being received in response to an external magnetic field applied to the distal end assembly (28, 283). Determining a change in a value of an electrical signal output by a distal coil (293) of the plurality of coils. Based on the change in the value of the electrical signal, determining whether the distal end assembly (28, 283) is in a collapsed state within the sheath (37) or has begun to emerge from the sheath and the distal coil (293) is in an at least partially inflated state outside of the sheath (37). In response to detecting the change in the value, the value of the electrical signal from the distal coil (293) is used to determine a location of a distal end of the sheath (37) within the body.

[0074] EMBODIMENT 2

[0075] According to the method of embodiment 1, and comprising: determining a relationship between the electrical signals output by two or more side coils (291, 292) of the plurality of coils (291, 292, 293), and upon detecting a change in the relationship, identifying, based on the electrical signals, that the distal end assembly (28, 283) has fully emerged from the sheath (37) and is fully inflated.

[0076] EMBODIMENT 3

[0077] According to the method of embodiment 2, and comprising: upon detecting a change in the relationship, calculating, based on the electrical signals, a position of the inflated distal tip assembly (28, 283) within the body.

[0078] EMBODIMENT 4

[0079] According to the method of embodiment 2, wherein the distal tip assembly (28, 283) comprises first and second side coils (291, 292) located on respective first and second sides of the distal tip assembly, and wherein determining the relationship comprises determining a relationship between the electrical signals output by the first and second side coils (291, 292).

[0080] EMBODIMENT 5

[0081] According to the method of embodiment 1, and comprising: determining that the change in the value of the electrical signal output by the distal coil (293) has occurred in the event that the change exceeds a predefined threshold.

[0082] EMBODIMENT 6

[0083] According to the method of embodiment 1, wherein the distal coil (293) is located at a distal edge of the distal tip assembly (28, 283).

[0084] EMBODIMENT 7

[0085] A system comprising: an interface (30) and a processor (56). The interface (30) is configured to receive electrical signals from a plurality of coils (291, 292, 293) embedded in a distal tip assembly (28, 283) of a catheter (14) delivered via a sheath (37) inserted into a body of a patient, the electrical signals being received in response to an external magnetic field applied to the distal tip assembly (28, 283). The processor (56) is configured to: (i) determine a change in a value of an electrical signal output by a distal coil (293) of the plurality of coils; (ii) based on the change in the value of the electrical signal, determine whether the distal tip assembly (28, 283) is in a collapsed state within the sheath (37) or has begun to emerge from the sheath and the distal coil (293) is in an at least partially inflated state outside the sheath; and (iii) in response to detecting the change in the value, use the value of the electrical signal from the distal coil (293) to determine a position of a distal end of the sheath (37) within the body.

[0086] Although the embodiments described herein are primarily directed to cardiac diagnostic applications, the methods and systems described herein can also be used in other medical applications.

[0087] It will be appreciated that the above- described embodiments are cited by way of example, and that the present disclosure is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present disclosure includes both combinations and sub-combinations of the various features described above, as well as variations and modifications thereof which would be subject to patentable equivalents and would be within the skills of persons of ordinary skill in the art upon reading the foregoing description.

Claims

1. A method comprising: receiving electrical signals from a plurality of coils embedded in a distal end assembly of a catheter delivered via a sheath inserted into a body of a patient, the electrical signals being received in response to an external magnetic field applied to the distal end assembly; determining a change in a value of an electrical signal output by a distal coil of the plurality of coils; based on the change in the value of the electrical signal, determining whether the distal end assembly is in a collapsed state within the sheath or has started to be exposed from the sheath and the distal coil is in an at least partially inflated state outside the sheath; and in response to detecting the change in the value, using the value of the electrical signal from the distal coil to determine a location of a distal end of the sheath within the body.

2. The method of claim 1, and comprising: determining a relationship between the electrical signals output by two or more side coils of the plurality of coils, and upon detecting a change in the relationship, based on the electrical signals, identifying that the distal end assembly has been fully exposed from the sheath and fully inflated.

3. The method of any of claims 1-2, and comprising: upon detecting the change in the relationship, based on the electrical signals, calculating a location of the inflated distal end assembly within the body.

4. The method of any one of claims 1 to 2, wherein, the distal end assembly comprises a first side coil and a second side coil located on respective first and second sides of the distal end assembly, and wherein determining the relationship comprises determining a relationship between the electrical signals output by the first side coil and the second side coil.

5. The method of claim 1, and comprising: the change in the value of the electrical signal output by the distal coil has occurred in the event that the change exceeds a predefined threshold.

6. The method of claim 1, wherein, the distal coil is located at a distal edge of the distal end assembly.

7. A system comprising: an interface configured to receive electrical signals from a plurality of coils embedded in a distal end assembly of a catheter delivered via a sheath inserted into a body of a patient, the electrical signals being received in response to an external magnetic field applied to the distal end assembly; and a processor configured to: determine a change in a value of an electrical signal output by a distal coil of the plurality of coils; based on the change in the value of the electrical signal, determine whether the distal end assembly is in a collapsed state within the sheath or has started to be exposed from the sheath and the distal coil is in an at least partially inflated state outside the sheath; and in response to detecting the change in the value, use the value of the electrical signal from the distal coil to determine a location of a distal end of the sheath within the body.

Images