Magnetic-based sheath detection

Abstract

To estimate a location within a human body of a distal end of a delivery sheath for an invasive medical probe.SOLUTION: The method includes receiving electrical signals from multiple coils embedded in a distal-end assembly of a catheter delivered via a sheath inserted into a body of a patient, wherein the electrical signals are received in response to applying 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 a 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 emerge from the sheath and the distal coil is in an at least partially expanded state outside the sheath. In response to detecting the change in the value, the value of the electrical signal from the distal coil is used to determine a location of the distal end of the sheath within the body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates generally to invasive medical probes, and more particularly to estimating the position within the human body of a distal end of a delivery sheath for an invasive medical probe. [Background technology]

[0002] Techniques for determining the position and / or state of a probe have previously been proposed in the patent literature. For example, U.S. Patent Application Publication No. 2019 / 0343423 describes a catheterization procedure performed by inserting a sheath into a human patient and moving a catheter having electrodes through the sheath lumen. A change between a first threshold and a second threshold in the current through the electrodes is identified. In response to the change, the portion of the catheter that has transitioned between an in-sheath state and an out-of-sheath state is reported. The sheath is defined and identified by historical data of readings of the catheter's magnetic sensor during movement.

[0003] A more complete understanding of the present disclosure will be obtained from the following detailed description of the embodiments of the present disclosure when read in conjunction with the drawings. [Brief explanation of the drawings]

[0004] [Figure 1] FIG. 1 is a schematic, pictorial illustration of a catheter-based electroanatomical (EA) mapping and ablation system, according to one embodiment of the present disclosure. [Figure 2A] 1A-1C are pictorial diagrams that schematically illustrate a three-coil layout and a six-coil layout of a flat catheter, according to some embodiments of the present disclosure. [Figure 2B] 1A-1C are pictorial diagrams that schematically illustrate a three-coil layout and a six-coil layout of a flat catheter, according to some embodiments of the present disclosure. [Figure 3] 2 is a schematic front pictorial view of the catheter flat assembly of FIG. 1 in a coiled configuration within a sheath, according to one embodiment of the present disclosure. FIG. [Figure 4A]2A-2C are three schematic diagrams of the flat catheter assembly of FIG. 1, respectively, inside the distal end of the sheath, partially deployed from the sheath, and fully deployed outside the sheath, according to one embodiment of the present disclosure. [Figure 4B] 2A-2C are three schematic diagrams of the flat catheter assembly of FIG. 1, respectively, inside the distal end of the sheath, partially deployed from the sheath, and fully deployed outside the sheath, according to one embodiment of the present disclosure. [Figure 4C] 2A-2C are three schematic diagrams of the flat catheter assembly of FIG. 1, respectively, inside the distal end of the sheath, partially deployed from the sheath, and fully deployed outside the sheath, according to one embodiment of the present disclosure. [Figure 5] 1 is a flow chart that schematically illustrates a method and algorithm for detecting the position of the distal end of a sheath using a flat catheter assembly deployment, according to one embodiment of the present disclosure. [Figure 6] FIG. 2 is a perspective view of the planar catheter assembly (also referred to as a "planar catheter end effector") of FIG. 1, according to one embodiment of the present disclosure. [Figure 7] FIG. 7 is a diagram of a catheter assembly including the end effector of FIG. 6 according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0005] overview Diagnostic and therapeutic catheters are typically 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 resides. However, because the sheath is typically a simple flexible tube without navigation means, determining the location of the distal end of the sheath within the body (e.g., within the heart) can be difficult.

[0006] Examples of the present disclosure described below provide techniques that utilize a special layout of magnetic position sensors (e.g., coils) on a planar catheter, with inherent spatial symmetry of the set of coils, to (i) determine the position 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 catheter deployment (e.g., whether it is still within the sheath, partially outside, or fully deployed outside the sheath). Using this real-time information, a physician can optimize catheter deployment (e.g., determine whether the position of the distal end of the sheath within the organ is optimal to proceed with full deployment of the catheter assembly).

[0007] The catheter of the present disclosure has a flat distal end assembly formed from a specific self-expanding material, such as a flexible PCB, that includes three or more flat magnetic coils (e.g., wiring loops) embedded in the flexible PCB. The magnetic loops pick up magnetic drive signals generated by location pads (e.g., placed under the patient) of a position tracking system and output respective electrical signals.

[0008] While the distal tip assembly is within the sheath and wound about its longitudinal axis, it produces pickup signals from the magnetic sensors that are not suitable as position-indicative signals. However, the authors have found that the nearly symmetrical coil layout produced by the wound configuration causes these signals to satisfy a specific relationship that indicates whether the planar assembly is wound in its entirety or partially outside the sheath.

[0009] Specifically, the authors noted that when the flat distal tip assembly is advanced slightly beyond the distal end of the sheath, at least one distal coil outputs an altered signal compared to its output when wound within the sheath. The tracking system's processor uses the altered signal to determine the position of the distal tip of the sheath within the body to a certain accuracy (e.g., within a few millimeters). For this purpose, the altered signal should have a value similar (e.g., approximately the same magnitude) as the standard corresponding position signal, but typically differ from the value of a fully deployed coil.

[0010] When the assembly is fully deployed (e.g., outside the sheath and in a self-expanded configuration), all of the coils output standard position guidance signals that are used by a position tracking system to precisely determine the location of the distal tip assembly within the body.

[0011] In one embodiment, the tracking system's processor receives signals from three magnetic sensors located on the catheter's flat distal end assembly (e.g., the side loops labeled X, Y, and the distal loop labeled Z, as shown in FIG. 2A) while the catheter is being delivered through the sheath. The system monitors real-time changes in the output of each of the three magnetic loops on the assembly.

[0012] While the distal end assembly is in a coiled configuration within the sheath, portions of any two side loops (X, Y) face each other around any external magnetic field direction. As a result, the output signals (SX, SY) of the side loops (X, Y) are equal in magnitude but opposite in sign, i.e., SX = -SY. The signal output SZ of distal loop Z is approximately zero due to its inherently asymmetric spatial layout around the magnetic field direction, and each contribution by one of its portions is canceled by the respective portion facing it relative to the magnetic field.

[0013] More generally, the correspondence relationship of the signals within the sheath (SX, SY, and SZ) can be written as SZ = ε, SX = ε + A, SY = ε - A, where ε is small or zero. As long as this relationship holds, the processor can determine that the flat distal tip assembly is rolled and therefore must be within a sheath.

[0014] Once the flat distal tip assembly extends slightly beyond the distal end of the sheath, the distal loop Z begins to self-expand into its deployed flat shape, and the output SZ of the distal loop Z becomes greater than a predetermined threshold (e.g., greater than 25ε). At this point, the localization system can use the position indications obtained from the distal loop to estimate the location of the distal tip of the sheath within the body (e.g., within the heart).

[0015] When the planar assembly is fully deployed, all loops assume a self-expanded planar configuration. In this state, the side loop signals (SX, SY) are no longer opposite in sign, and at this point the assembly position indication obtained using the three loops is highly accurate.

[0016] System Description 1 is a schematic, pictorial illustration of a catheter-based electroanatomical (EA) mapping and ablation system 10, according to one embodiment of the present disclosure. System 10 includes a delivery sheath 37 that is percutaneously inserted by a physician 24 through a patient's vascular system into a cavity or vasculature of heart 12. A flat catheter 14 (shown in inset 45) is then inserted into delivery sheath 37, deployed outside sheath 37 (e.g., into the blood pool of a cardiac chamber 33), and then advanced to a desired tissue location.

[0017] In FIG. 1 , the physician 24 advances a flat-type expandable distal end assembly 28 (hereinafter also referred to as the “expandable distal end assembly 28”) attached to the shaft 44 of the catheter 14 to contact the heart wall so that the EA can sense a target site within the heart 12.

[0018] As seen in inset 65, planar assembly 28 includes a plurality of functional electrodes 26 optionally distributed across a plurality of splines 22 in expandable distal end assembly 28 and configured to sense IEGM signals. Assembly 28 has a longitudinal axis 42 that is parallel to distal end 46 of shaft 44 and is the axis of symmetry of assembly 28.

[0019] Assembly 28 includes a magnetic position sensor 29 comprising three coils, as seen in FIG. 2A. The coils are embedded in spline 22 and are used to track the position and / or orientation of expandable distal tip assembly 28. One of the coils is located closer to distal edge 16 of assembly 28 and is therefore designated the "distal coil." Magnetic position sensor 29 operates in conjunction with an external location pad 25, which includes multiple magnetic coils 32 configured to generate a magnetic field within a predetermined workspace. Using the operation of external location pad 25 (each coil using a different frequency), a processor can determine the position of sensor 29 within the coordinate system of a position tracking system.

[0020] Details of magnetic-based position sensing technology are described in U.S. Patent Nos. 5,5391,199, 5,443,489, 5,558,091, 6,172,499, 6,239,724, 6,332,089, 6,484,118, 6,618,612, 6,690,963, 6,788,967, and 6,892,091.

[0021] The system 10 includes one or more electrode patches 38 positioned for skin contact with the patient 23 to establish a position reference for the location pads 25, as well as impedance-based tracking of the functional electrodes 26. For impedance-based tracking, current is directed to the electrodes 26 and sensed at the electrode skin patches 38, allowing the position of each electrode to be triangulated via the electrode patches 38.

[0022] Details of impedance-based location 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.

[0023] Recorder 11 displays electrograms 21 captured by the body surface ECG electrodes 18 and intracardiac electrograms (IEGMs) captured by the functional electrodes 26 of catheter 14. Recorder 11 may include pacing capability for pacing the cardiac rhythm and / or may be electrically connected to a stand-alone pacer.

[0024] The system 10 may include an ablation energy generator 50 adapted to deliver ablation energy to a subset of the plurality of electrodes 26 on the distal assembly 28 of the catheter 14 configured for ablation. The energy generated by the ablation energy generator 50 may include, but is not limited to, radiofrequency (RF) energy or pulsed-field ablation (PFA) energy, including unipolar or bipolar high-voltage direct current pulses such as may be used to produce irreversible electroporation (IRE), or a combination thereof.

[0025] The patient interface unit (PIU) 30 is configured to establish electrical communication between the catheters, the electrophysiology equipment, a power source, and a workstation 55 for controlling the operation of the system 10. The electrophysiology equipment of the system 10 may include, for example, multiple catheters, location pads 25, body surface ECG electrodes 18, electrode patches 38, an ablation energy generator 50, and a recorder 11. Optionally and preferably, the PIU 30 additionally includes processing capability for performing real-time calculations of catheter position and for performing ECG calculations.

[0026] The workstation 55 includes a processor unit 56 having a memory 57, a memory or storage device having appropriate operating software loaded therein, and user interface functionality. The workstation 55 may optionally provide multiple functions, including (i) modeling the endocardial anatomical structure in three-dimension (3D) and rendering the model or anatomical map 20 for display on the display device 27, (ii) displaying activation sequences (or other data) compiled from recorded electrograms 21 in a representative visual representation or image superimposed on the rendered anatomical map 20 on the display device 27, (iii) displaying the real-time position and orientation of multiple catheters within the cardiac chambers, and (iv) displaying sites of interest, such as locations where ablation energy has been applied, on the display device 27. One commercially available product embodying elements of the system 10 is available as the CARTO™ 3 system, available from Biosense Webster, Inc., 31A Technology Drive, Irvine, CA 92618.

[0027] Flat catheter coil layout 2A and 2B are schematic, pictorial diagrams illustrating a three-coil layout 283 and a six-coil layout 286 for a flat catheter, according to some examples of the present disclosure.

[0028] Figure 2A shows a layout 283 of three (X, Y, Z) coils (291, 292, 293) of sensor 29 of distal tip assembly 28, further described in Figures 3 and 4. As shown, the layout includes first and second side coils (291, 292) disposed on respective first and second sides of the distal tip assembly, and distal coil 293.

[0029] When the distal end assembly is wound within the sheath, the loops (291, 292, 293) are wound on the longitudinal axis 42, forming a generally asymmetric spatial layout around the magnetic field direction.

[0030] As the flat distal end assembly slightly exits the distal end of the sheath, only the distal loop Z begins to self-expand into its deployed flat shape.

[0031] When the flat assembly is fully deployed, the side loops also self-expand into a flat shape.

[0032] 2B shows a layout 286 of six (M, N, O, P, R, S) coils 296. The greater the number of coils, the more precisely the position tracking system can determine the state of deployment of the catheter away from the sheath.

[0033] 3 is a schematic front view pictorial diagram of the planar assembly 28 of the catheter 14 of FIG. 1 in a coiled configuration within the sheath 37, according to one embodiment of the present disclosure. As can be seen, the planar assembly 28 is coiled about the longitudinal axis 42, with the side loops 291 and 292 exhibiting opposite facets relative to any magnetic field, such that their pickup signals SX and SY approximately satisfy the relationship SX=-SY.

[0034] The two portions 293a and 293b of the distal coil 293 also exhibit predominantly opposite facets to any magnetic field, so that the pickup signal SZ of the coil 293 approximately satisfies the relationship SZ = ε (e.g., ε ~ 0).

[0035] Magnetic-Based Sheath Detection Using Planar Catheter Deployment 4A, 4B, and 4C are schematic illustrations of the flat catheter assembly 28 of FIG. 1 inside the distal end of the sheath 37, partially deployed from the sheath 37, and fully deployed outside the sheath 37, respectively, according to one embodiment of the present disclosure.

[0036] Table 1 below lists the signal values ​​or relationships that the coils (291, 292, and 293) output / hold in any of the three deployment configurations of Figures 4A-4C.

[0037] [Table 1]

[0038] 4A shows schematically that side coils 291 and 292 face each other while wound within sheath 37, thereby generating pickup signals of approximately equal magnitude but opposite sign. At the same time, the two sides of distal coil 293 also face each other, thereby generating a pickup signal of approximately zero.

[0039] 4B shows schematically that while assembly 28 is partially wound within sheath 37 (i.e., partially wound outside sheath 37), side coils 291 and 292 still face each other, thereby generating pickup signals of approximately equal magnitude but opposite sign. At the same time, distal coil 293 has already partially expanded from sheath edge 437 into its flat shape, and therefore coil 293 generates an approximately true position signal SZ.

[0040] 4C schematically shows assembly 28 in a self-expanded, flattened configuration and completely outside sheath 37. In this case, side coils 291 and 292 are expanded away from sheath edge 437 and generate different true position signals (e.g., position signals of different magnitudes but with the same sign). Distal coil 293 is in its self-expanded, flattened configuration and generates true position signal SZ.

[0041] Method for magnetic-based sheath detection using planar catheter deployment 5 is a flow chart that schematically illustrates a method and algorithm for detecting the position of the distal end of the sheath 37 using deployment of a flat catheter assembly 28, according to one embodiment of the present disclosure. The algorithm, according to this embodiment, executes a process that begins with a signal reception step 502, in which the processor 56 receives electrical signals output by the side coils (291, 292) and distal coil 293 of the assembly 28 wound within the sheath 37 as the assembly is advanced within the sheath 37.

[0042] In a signal relationship monitoring step 504, the processor 56 monitors in real time the relationship between the electrical signals received from the side coils 291 and 292 in step 502 and the values ​​of the signal from the distal coil 293, such as by monitoring that these signals satisfy the entries shown in Table 1 of FIG. 4A when the catheter is in a coiled configuration within the sheath.

[0043] In a signal value change detection step 506, the processor detects a change in the electrical signal value output by the distal coil 293, which indicates a change in the shape of the planar assembly 28 as it begins to emerge from the sheath 37. The amount of detected change, which indicates that the distal coil 293 is partially out of the sheath and has an at least partially self-expanded shape with a corresponding new entry, is shown in Table 1 of FIG.

[0044] In a sheath position estimation step 508, the processor estimates the position of the distal end of the sheath 37 within the body using a first substantial (e.g., greater than a predetermined threshold) position signal from the at least partially self-expanded distal coil 293.

[0045] Next, in signal relationship change detection step 510, the processor detects a change in the relationship between the signals from the coils (291, 292), which indicates a further change in the shape of the planar assembly. In the case of planar catheter assembly 28, this would detect a change indicating that all distal coils (291, 292, and 293) are fully deployed outside the sheath, with the corresponding new relationship shown in Table 1 of FIG. 4C.

[0046] In an assembly position estimation step 512, the processor uses the position signals from all three coils to estimate the position of the planar assembly 28 within the body. This initial estimate may also be used to corroborate the position estimate of the sheath 37 in step 508.

[0047] 5 is simplified for conceptual clarity. For example, additional intermediate steps (e.g., changing relationships) may be considered depending on the coil layout and workflow. Additional steps may also include retracting the catheter into the sheath 37 based on the sheath's distal end position (determined in step 508) being deemed unusable, after which the sheath is moved to a more optimal position before fully deploying the assembly 28.

[0048] Double-sided sealed flat catheter 6 is a perspective view of the flat catheter assembly 28 of FIG. 1 (also referred to as a "flat catheter end effector 100"), according to one embodiment of the present disclosure. The double-sided end effector 100 is coupled to a catheter shaft 90. Importantly, the end effector 100 has a generally flat profile with electrodes 160 disposed on its two opposing (along axis VV) planar facets, e.g., tines 106. The layout of the two opposing facets may be the same or different.

[0049] Multiple pairs of electrodes 160 may be provided arranged on a flexible circuit on two opposing facets of the effector 100, the electrodes being spaced apart by a first predetermined longitudinal distance D1, 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 D1.

[0050] The electrodes 160 can sense tissue signals or transmit energy (AC or DC) from an energy generator to the tissue. At least some of the electrodes 160 can be axially aligned orthogonal to the longitudinal axis LL, with the position of at least one of the electrodes defining an opposing electrode pair.

[0051] The end effector 100 can include a framework 120, a non-conductive flexible layer 130, and flexible circuits 110 and 150. The continuous mass of flexible non-conductive material 130 can have portions 132 removed. The portions 132 can also be formed in one or all of the flexible circuit and framework 120. The portions 132 can pass through all layers of the multi-layer end effector 100, or only some of the layers. The portions 132 can be included to improve the ability of the end effector 100 to fold or bend into a contracted delivery configuration to allow the end effector 100 to pass through a delivery catheter.

[0052] The flexible circuits 110 and 150 may extend along a longitudinal axis LL from the proximal portion 102 to the distal portion 104 of the end effector 100 and may each include two opposing sides. The framework 120 may include two opposing sides and may extend along the longitudinal axis LL generally parallel to the flexible circuits 110 and 150. The non-conductive flexible layer 130 may at least partially encapsulate the first flexible circuits 110 and 150 and the framework 120.

[0053] In some examples, the flexible circuit layer 110 and 150 may be made primarily of polyimide. In other examples, it may be made of biocompatible polyimide, glass-reinforced epoxy laminate material, copper, or graphene, either alone or in combination. The flexible circuit layer may include conductive traces.

[0054] End effector 100 includes a position sensing coil layer 140 including multiple coils, such as coils (291, 292, 293) of FIG. 2A, that lie generally parallel to framework 120 and are separated from framework 120 by another non-conductive flexible layer 130. The coils may be coplanar in some examples.

[0055] Far-field signals (including noise or artifacts) can be reduced or canceled for the entire end effector using reference electrodes 161 a and 161 b located on opposite sides near the proximal base 102 of the framework 100 so that the reference electrodes do not contact tissue and only blood. The reference electrodes 161 are preferably exposed to the surrounding blood environment, but can be encapsulated in a polymer so that the reference electrodes are not exposed through a non-conductive layer.

[0056] Irrigation may include two irrigation ports 163a and 163b (one on each side) that are in fluid communication with an irrigation line (not shown) located within the catheter shaft 90. Instead of an irrigation line separate from the catheter shaft 90, a lumen may be formed by extrusion of the catheter shaft 90 to provide a luminal channel. Note that the ports 163 may be configured with sufficient flow diverter properties to allow the irrigation fluid to cover the electrodes during irrigation flow, to prevent or reduce clot formation.

[0057] Details of electrode spacing can be found in U.S. Provisional Patent Application No. SN63 / 406,673, filed September 14, 2022 (Attorney Docket No. BIO6749USPSP3), which is incorporated by reference in its entirety as if fully set forth in and attached as an appendix to priority application U.S. Provisional Patent Application No. 63 / 505,764, filed June 2, 2023 (Attorney Docket No. 253757.000380 BIO6846USPSP1). The present disclosure provides a catheter assembly 200, as shown in FIG. 7, which can include a tubular member 230 (also referred to as a "shaft" 230) extending along a longitudinal axis LL and configured to deliver the end effector 100 out of the sheath 210. A physician 24 can manipulate the catheter 200 using a handle 220. Suitable examples of the catheter assembly 200 and its subcomponents, such as the handle 220, sheath 210, tubular member 230, and others not mentioned herein, are described in U.S. Patent Application Publication No. 2021 / 0369339, which is incorporated by reference in its entirety as if fully set forth in and attached to U.S. Provisional Application No. 63 / 505,764, filed June 2, 2023 (Attorney Docket No. 253757, 000380 BIO6846USPSP1), a priority application. [Example]

[0058] Example 1 The method includes receiving electrical signals from a plurality of coils (291, 292, 293) embedded in a distal end assembly (28, 283) of a catheter (14) delivered through a sheath (37) inserted within a patient's body, the electrical signals being received in response to application of an external magnetic field to the distal end assembly (28, 283). A change in value of the electrical signal output by a distal coil (293) of the plurality of coils is determined. Based on the change in value of the electrical signal, it is determined whether the distal end assembly (28, 283) is in a collapsed state within the sheath (37) or is beginning to emerge from the sheath, with the distal coil (293) in an at least partially expanded state outside the sheath (37). In response to detecting the change in value, the value of the electrical signal from the distal coil (293) is used to determine the position of the distal end of the sheath (37) within the body.

[0059] Example 2 The method of Example 1, comprising: determining a relationship between 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 extended.

[0060] Example 3 3. The method of example 2, comprising, upon detecting a change in the relationship, calculating a position of the expanded distal end assembly (28, 283) within the body based on the electrical signal.

[0061] Example 4 The method of example 2, wherein the distal end assembly (28, 283) comprises a first side coil and a second side coil (291, 292) disposed on a first side and a second side of the distal end assembly, respectively, and determining the relationship comprises determining the relationship between electrical signals output by the first side coil and the second side coil (291, 292).

[0062] Example 5 2. The method of example 1, comprising determining that a change in the value of the electrical signal output by the distal coil (293) has occurred if the change exceeds a predetermined threshold.

[0063] Example 6 2. The method of claim 1, wherein the distal coil (293) is disposed at the distal edge of the distal end assembly (28, 283).

[0064] Example 7 The system includes 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 end assembly (28, 283) of a catheter (14) delivered through a sheath (37) inserted into a patient's body, the electrical signals being received in response to application of an external magnetic field to the distal end assembly (28, 283). The processor (56) is configured to (i) determine a change in the value of an electrical signal output by a distal coil (293) of the plurality of coils, (ii) determine, based on the change in the value of the electrical signal, whether the distal end assembly (28, 283) is in a collapsed state within the sheath (37) or is beginning to emerge from the sheath and the distal coil (293) is in an at least partially expanded state outside the sheath, and (iii) in response to detecting the change in value, use the value of the electrical signal from the distal coil (293) to determine the position of the distal end of the sheath (37) within the body.

[0065] Although the examples described herein primarily address cardiac diagnostic applications, the methods and systems described herein may also be used in other medical applications.

[0066] It will be understood that the above-described embodiments are given by way of example, and that the present disclosure is not limited to what is particularly shown and described hereinabove. Rather, the scope of the present disclosure includes both combinations and sub-combinations of the various features hereinabove, as well as variations and modifications thereof which would occur to one skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.

[0067] [Embodiment] (1) A method comprising: receiving electrical signals from a plurality of coils embedded in a distal tip assembly of a catheter delivered through a sheath inserted into a patient's body, the electrical signals being received in response to application of an external magnetic field to the distal tip assembly; determining a change in value of an electrical signal output by a distal coil of the plurality of coils; determining whether the distal tip assembly is in a collapsed state within the sheath or is beginning to emerge from the sheath and the distal coil is in an at least partially expanded state outside the sheath based on the change in the value of the electrical signal; and in response to detecting the change in value, using the value of the electrical signal from the distal coil to determine a position of a distal end of the sheath within the body. (2) The method of embodiment 1, including 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, identifying that the distal end assembly has fully emerged from the sheath and is fully expanded based on the electrical signals. (3) The method of embodiment 2, further comprising, upon detecting a change in the relationship, calculating a position of the expanded distal end assembly within the body based on the electrical signal. (4) The method of embodiment 2, wherein the distal end assembly comprises a first side coil and a second side coil disposed on a first side and a second side of the distal end assembly, respectively, and determining the relationship includes determining a relationship between the electrical signals output by the first side coil and the second side coil. (5) The method of claim 1, comprising determining that the change in the value of the electrical signal output by the distal coil has occurred if the change exceeds a predetermined threshold.

[0068] (6) The method of embodiment 1, wherein the distal coil is disposed at the 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 tip assembly of a catheter delivered through a sheath inserted into a patient's body, the electrical signals being received in response to application of an external magnetic field to the distal tip assembly; A processor, the processor comprising: determining a change in value of an electrical signal output by a distal coil of the plurality of coils; determining whether the distal tip assembly is in a collapsed state within the sheath or has begun to emerge from the sheath with the distal coil in an at least partially expanded state outside the sheath based on the change in the value of the electrical signal; and a processor configured to: in response to detecting the change in value, determine a position of a distal end of the sheath within the body using the value of the electrical signal from the distal coil. (8) The system described in embodiment 7, wherein the processor is further configured to determine 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, identify based on the electrical signals that the distal end assembly has fully emerged from the sheath and is fully expanded. (9) The system of embodiment 8, wherein the processor is further configured to calculate a position of the expanded distal end assembly within the body based on the electrical signal when the processor detects a change in the relationship. (10) The system of embodiment 8, wherein the distal end assembly comprises a first side coil and a second side coil disposed on a first side and a second side of the distal end assembly, respectively, and the processor is configured to determine the relationship by determining the relationship between the electrical signals output by the first side coil and the second side coil.

[0069] (11) The system of embodiment 7, wherein the processor is further configured to determine that the change in the value of the electrical signal output by the distal coil has occurred if the change exceeds a predetermined threshold. (12) The system of embodiment 7, wherein the distal coil is disposed at the distal edge of the distal end assembly.

Claims

1. 1. A system comprising: an interface configured to receive electrical signals from a plurality of coils embedded in a distal tip assembly of a catheter delivered through a sheath inserted into a patient's body, the electrical signals being received in response to application of an external magnetic field to the distal tip assembly; A processor, the processor comprising: determining a change in value of an electrical signal output by a distal coil of the plurality of coils; determining whether the distal tip assembly is in a collapsed state within the sheath or has begun to emerge from the sheath with the distal coil in an at least partially expanded state outside the sheath based on the change in the value of the electrical signal; and a processor configured to: in response to detecting the change in value, determine a position of a distal end of the sheath within the body using the value of the electrical signal from the distal coil.

2. 1. A method comprising: receiving electrical signals from a plurality of coils embedded in a distal tip assembly of a catheter delivered through a sheath inserted into a patient's body, the electrical signals being received in response to application of an external magnetic field to the distal tip assembly; determining a change in value of an electrical signal output by a distal coil of the plurality of coils; determining whether the distal tip assembly is in a collapsed state within the sheath or is beginning to emerge from the sheath and the distal coil is in an at least partially expanded state outside the sheath based on the change in the value of the electrical signal; and in response to detecting the change in value, using the value of the electrical signal from the distal coil to determine a position of a distal end of the sheath within the body.

3. 3. The method of claim 2, 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, identifying that the distal tip assembly has fully emerged from the sheath and is fully expanded based on the electrical signals.

4. The method of any one of claims 2 to 3, comprising, upon detecting a change in the relationship, calculating a position of the expanded distal tip assembly within the body based on the electrical signal.

5. 4. The method of claim 2, wherein the distal end assembly comprises a first side coil and a second side coil disposed on a first side and a second side of the distal end assembly, respectively, and wherein determining the relationship comprises determining a relationship between the electrical signals output by the first side coil and the second side coil.

6. The method of claim 2 , comprising determining that the change in the value of the electrical signal output by the distal coil has occurred if the change exceeds a predetermined threshold.

7. The method of claim 2 , wherein the distal coil is disposed at a distal edge of the distal tip assembly.

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