Integrated electromagnetic and impedance sensor for catheters

Abstract

Methods and apparatus for performing medical ablation procedures. In one example, a catheter for performing pulsed field ablation has an integrated electromagnetic and impedance sensor in which at least one element is used to support both position and shape tracking. The element sharing enables the footprint of the distal portion of the catheter to remain relatively small even with a new capability having been added thereto.

Description

INTEGRATED ELECTROMAGNETIC AND IMPEDANCE SENSOR FORCATHETERS

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 588,163, filed October 5, 2023, the entire content of which is incorporated herein by reference.FIELD

[0002] The present disclosure relates to methods, systems, and devices for improving navigation and positioning of catheters.BACKGROUND

[0003] Catheters are used in many clinical procedures, e.g., to provide access to the cardiopulmonary system. Control of such catheters is typically performed by clinicians through a handle, e.g., by actuating opposing pull-wires. An electromagnetic (EM) sensor embedded in the catheter tip is typically used for the catheter-position tracking as the catheter is being handled by the clinician. In some cases, a catheter may have a treatment element whose shape is changeable. For such catheters, shape tracking in addition to position tracking is important.SUMMARY

[0004] Disclosed herein are, among other things, various aspects, features, and embodiments of methods and apparatus for performing medical ablation procedures. In one example, a catheter for performing pulsed field ablation (PFA) has an integrated electromagnetic (EM) and impedance sensor in which at least one element is used to support both position and shape tracking. The element sharing enables the footprint of the distal portion of the catheter to remain relatively small even with a new capability having been added thereto.

[0005] One example provides a medical apparatus including an elongated body passable through patient’s vasculature and having a distal portion and a proximal portion in mechanical and electrical communication with each other. The medical apparatus also includes an EM sensor located in the distal portion and electrically connected through the elongated body to the proximal portion using a first electrical wire, a second electrical wire, and a third electrical wire.The EM sensor includes a first electrode and an EM coil having a magnetic core. The first electrode is electrically connected to the proximal portion via the first electrical wire. The EM coil is electrically connected to the proximal portion via the second electrical wire and the third electrical wire. The medical apparatus also includes a carrier arm mechanically connected to the distal portion and having a plurality of second electrodes mounted thereon. The plurality of second electrodes is electrically connected to the proximal portion via an electrical bus disposed within the elongated body.

[0006] In some examples, the above medical apparatus is configured to (i) determine a position of the EM sensor with respect to patient’s anatomy based on a voltage between the second electrical wire and the third electrical wire generated by the EM coil in response to an external magnetic field; (ii) independently determine the position of the first electrode based on a signal from the first electrode detected via the first electrical wire in response to periodic currents driven through a patient’s body with a plurality of third electrodes; and (iii) determine positions of the plurality of second electrodes with respect to the patient’s anatomy based on signals from the plurality of second electrodes detected via the electrical bus and further based on a coordinate system established based on the twice-determined position of the first electrode.

[0007] Another example provides a medical apparatus including an elongated body passable through patient’s vasculature and having a distal portion and a proximal portion in mechanical and electrical communication with each other. The medical apparatus also includes an EM sensor located in the distal portion and electrically connected through the elongated body to the proximal portion using a first electrical wire and a second electrical wire. The medical apparatus also includes a carrier arm having a first end and a second end. The first end is fixedly attached to the distal portion of the elongated body. The second end is fixedly attached to a shaft that is longitudinally movable with respect to the distal portion with a guidewire disposed within the elongated body. The carrier arm also has a plurality of first electrodes mounted thereon and electrically connected to the proximal portion via an electrical bus disposed within the elongated body. The medical apparatus also includes a coil-shaped electrode wound around a section of the carrier arm adjacent to the first end and electrically connected to the proximal portion via a third electrical wire disposed within the elongated body.

[0008] In some examples, the above medical apparatus is configured to (i) determine a position of the EM sensor with respect to patient’s anatomy based on a voltage between the first electrical wire and the second electrical wire generated by the EM sensor in response to an external magnetic field; (ii) determine the position of the coil-shaped electrode based on a signal from the coil-shaped electrode detected via the third electrical wire in response to periodic currents driven through a patient’s body with a plurality of second electrodes; and (iii) determine positions of the plurality of first electrodes with respect to the patient’s anatomy based on signals from the plurality of first electrodes detected via the electrical bus and further based on a coordinate system established based on the positions of the EM sensor and the coil-shaped electrode.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a block diagram illustrating a medical system according to some examples.

[0010] FIG. 2 illustrates a side view of an EM sensor that can be used in the medical system of FIG. 1 according to one example.

[0011] FIG. 3 illustrates a side view of an EM sensor that can be used in the medical system of FIG. 1 according to another example.

[0012] FIGS. 4A-4B show three-dimensional (3D) perspective views illustrating a modification of the EM sensor of FIG. 3 according to one example.

[0013] FIG. 5 shows a 3D perspective view illustrating an EM-sensor assembly that can be used in the medical system of FIG. 1 according to one example.

[0014] FIG. 6 shows a 3D perspective view illustrating the distal portion of a catheter used in the medical system of FIG. 1 according to one example.

[0015] FIG. 7 shows a 3D perspective view illustrating the distal portion of a catheter used in the medical system of FIG. 1 according to another example.

[0016] FIG. 8 shows a 3D perspective view illustrating the distal portion of a catheter used in the medical system of FIG. 1 according to yet another example.

[0017] FIG. 9 shows a 3D perspective view illustrating the distal portion of a catheter used in the medical system of FIG. 1 according to yet another example.

[0018] FIG. 10 is a schematic diagram illustrating a cross-sectional side view of a section of the carrier arm used in a catheter of the medical system of FIG. 1 according to one example.

[0019] FIG. 11 is a block diagram illustrating impedance -based mapping operations implemented in the medical system of FIG. 1 according to one example.

[0020] FIG. 12 is a flowchart illustrating a mapping and navigation method implemented in the medical system of FIG. 1 according to one example.DETAILED DESCRIPTION

[0021] Some embodiments disclosed herein are directed to fluoro-free navigation of catheters to their targeted locations within the patient’s body. Although example embodiments are described herein below in reference to catheters typically used for cardiac mapping and ablation, various embodiments are not so limited. Based on the provided description, a person of ordinary skill in the pertinent art will be able to make and use additional embodiments suitable for other types of catheters without any undue experimentation.

[0022] Some embodiments provide modifications of established EM sensor design and technology. For example, some embodiments preserve the performance characteristics of EM- sensor elements while adding thereto a new capability to collect impedance information. In one example, an EM-sensor modification directed at providing such added capability includes extending the magnetic core of the EM sensor beyond the insulative EM-sensor potting, thereby subjecting an electrically conducting surface of the magnetic core to patient’s blood and providing an electrically conductive path between the magnetic core and the navigation system. In some examples, the electrically conducting surface is plated with a suitable biocompatible material that is different from the material used to form the bulk of the magnetic core.

[0023] Some embodiments use integrated components suitable for shared use in electromagnetic and impedance-based navigation techniques. In some examples, EM-based sensing is used to provide an accurate overall catheter positioning while impedance -basedsensing is used to determine the orientation and shape of the array of treatment electrodes within the deployed distal portion of the catheter. Some embodiments enable both sensing techniques without increasing an operational footprint of the distal portion compared to that of a corresponding catheter providing only for electromagnetic sensing.

[0024] FIG. 1 is a block diagram illustrating a medical system 100 according to various examples. In the example shown, the system 100 includes a medical device 110 and an electronic controller 160 in direct or indirect communication with the medical device 110. In operation, the medical device 110 is used to deliver energy, for example, PFA or electroporation energy, for treating or ablating an area of target tissue. The medical device 110 also incorporates a plurality of navigation elements that enable position and shape tracking of a distal portion 101 of a catheter 102 of the medical device 110. As an illustration, two of such navigation elements, i.e., an EM sensor 120 and a reference electrode 122, are indicated in FIG. 1. Additional ones of such navigation elements used in at least some embodiments of the catheter 102 and the medical system 100 are shown in FIGS. 2-11 and described in more detail below in reference thereto.

[0025] The distal portion 101 of the catheter 102 has electrodes 118 used for therapeutic interaction with the selected treatment site in or on the patient’s body. In operation, the electrodes 118 deliver energy, for example, PFA energy, electroporation energy, non-therapeutic pulses and waveforms, and / or other transferred energy, to the treatment site. The catheter 102 also includes an elongated body 104 to enable placement of the electrodes 118 in proximity to the treatment site of the patient for performing diagnosis, collecting EGM signals, determining the degree of contact with the tissue, and / or delivering treatment. The elongated body 104 has a proximal portion 106, is connected to the distal portion 101, and typically includes one or more lumens that provide mechanical, electrical, and / or fluid communication between the proximal portion 106 and the distal portion 101. In some examples, the elongated body 104 has a central or guidewire lumen for hosting a shaft 132 and a carrier arm 128 in a retracted position. The shaft 132 is longitudinally movable within and with respect to the outer shaft of the catheter 102. In operation, longitudinal movement of the shaft 132 is used to cause the carrier arm 128 to transition between at least a first (e.g., substantially linear) configuration and a second (e.g., looped) configuration. As an illustration, FIG. 1 shows the carrier arm 128 in a looped configuration.

[0026] The proximal portion 106 typically includes or is connected to a handle (not explicitly shown in FIG. 1) that can be used to manipulate the catheter 102. Additionally, the proximal portion 106 includes an electrical connector 108 for electrically connecting various circuit elements of the distal portion 101 to pertinent circuitry of the system 100 that is external to the catheter 102. As an example, three corresponding electrical connections are explicitly shown in FIG. 1: (i) an electrical bus connection 138 between a voltage and waveform generator 140 and the electrodes 118; (ii) an electrical connection 146 between a mapping and navigation module 150 and the reference electrode 122; and (iii) an electrical twisted-pair connection 148 between the mapping and navigation module 150 and the EM sensor 120. In other instances, a different number of connections may be used. The proximal portion 106 also typically has one or more actuation or control features that enable the corresponding practitioner to control, deflect, steer, or otherwise manipulate the distal portion 101 via the proximal portion 106.

[0027] The mapping and navigation module 150 is typically used for guiding a medical treatment procedure. In the example shown, the medical device 110 is coupled to the electronic controller 160 through the mapping and navigation module 150. In some other examples, both the medical device 110 and the mapping and navigation module 150 are directly coupled to the electronic controller 160. The mapping and navigation module 150 is designed to help visualize the real-time position and orientation of the distal portion 101 of the catheter 102 within the patient’s body, e.g., to increase the accuracy of targeted ablation and reacquisition of pacing sites for re-ablation.

[0028] In one example, the mapping and navigation module 150 operates to calculate the position of the reference electrode 122 using three or more magnetic sources of a magnetic-field generator 130 as references. The magnetic sources of the magnetic field generator 130 are positioned such that a volume 134 of the magnetic fields generated thereby envelopes the distal portion 101. The magnetic fields in the volume 134 are calibrated and can be controlled with the electronic controller 160 via a control path 144. Based on the response of the EM sensor 120 to such magnetic fields and the known fixed location of the reference electrode 122 with respect to the EM sensor 120, position of the reference electrode 122 is accurately determined and tracked in real time.

[0029] During a medical treatment procedure, the reference electrode 122 and the electrodes 118 are surrounded by patient’s blood, which provides electrically conducive paths between the electrodes 118, the reference electrode 122, and other electrodes, which can be placed on the skin of the patient or introduced into the patient’s body using another catheter (e.g., see FIG. 11). Impedances of various conductive paths can be measured with the electronic controller 160 appropriately operating the generator 140 and the mapping and navigation module 150. Based on the measured impedances, the electronic controller 160 determines the positions of the reference electrode 122 and the individual ones of the electrodes 118. Based on the determined positions and known geometric and structural characteristics of the carrier arm 128, the shape of the carrier arm 128 together with the roll, pitch, and yaw angles thereof with respect to a longitudinal axis 116 of the distal portion 101 can also be determined. Since the laboratoryframe Cartesian coordinates (x, y, z) of the reference electrode 122 and its position with respect to pertinent anatomic features of the patient’s body are being accurately tracked using the EM sensor 120 as explained above, the Cartesian coordinates of the individual electrodes 118 and their positions with respect to the pertinent anatomic features of the patient’s body can also be accurately tracked solely based on the impedance measurements. The mapping and navigation module 150 can then be used to visualize the position and geometric configuration of the distal portion 101 within the patient’s body for the medical practitioner.

[0030] FIG. 2 illustrates a side view of an EM sensor 200 that can be used in the catheter 102 according to one example. In some examples, the EM sensor 200 is used to implement the EM sensor 120 (FIG. 1). The EM sensor 200 includes an EM coil 210 made of an insulated metal (e.g., copper) wire. A voltage induced in the EM coil 210 by the magnetic fields of the volume 134 is sensed by the mapping and navigation module 150 via lead wires 208 and 212 electrically connected thereto through the electrical connection 148. The EM coil 210 is wound around a cylindrical core 220 made of a suitable magnetic material, such as iron or cobalt-based ferrite. The presence of the cylindrical core 220 in the center of the EM coil 210 significantly increases the sensitivity of the EM sensor 200 to magnetic fields and, as such, improves the precision with which the position of the distal portion 101 can be tracked in the system 100. Both the EM coil 210 and the magnetic core 220 are fully encapsulated by a potting material (e.g., a polymer) 230. In the example shown, the potting 230 causes the magnetic core 220 of the EM sensor 200 to beelectrically floating, as the magnetic core 220 does not have a direct electrical connection to any other circuit elements of the medical device 110.

[0031] FIG. 3 illustrates a side view of an EM sensor 300 that can be used in the catheter 102 according to another example. The EM sensor 300 represents a modification of the EM sensor 200 illustrated in FIG. 2, with the modification being directed at integrating the reference electrode 122 into the EM sensor. Beneficially, the incorporation of the reference electrode 122 into the EM sensor 300 provides for an additional functionality substantially without increasing the footprint of the resulting modified EM sensor 300 compared to that of the EM sensor 200 illustrated in FIG. 2.

[0032] In the EM sensor 300, a distal end 306 of the magnetic core 220 is extended beyond the potting 230 to create a surface of the core that is exposed to and is in electrical contact with patient’s blood when the catheter 102 is deployed in the patient’s body. At an opposite, proximal end 304 of the magnetic core 220 of the EM sensor 300, there is an electrical lead wire 302 that is attached to the core. The lead wire 302 is further connected to the electrical connection 146, which enables the exposed surface of the magnetic core 220 of the EM sensor 300 to be used as the reference electrode 122.

[0033] In some examples, the surface 122 of the distal end 306 of the cylindrical core 220 in the EM sensor 300 is unmodified and comprises substantially the same material as the bulk of the cylindrical core 220. In some other examples, the surface 122 is covered by a thin film of an electrically conducting material. In some examples, the material for the thin film is selected from the group consisting of platinum-iridium alloy, gold, titanium, MP35N, 35NLT, austenitic stainless steel, and tantalum. Herein, the abbreviation MP35N refers to a vacuum induction melted (VIM), vacuum arc re-melted (VAR) superalloy with cobalt, nickel, chromium, and molybdenum as its primary alloying elements. MP35N’s nominal chemical composition by weight is approximately 35% cobalt, 35% nickel, 20% chromium, and 10% molybdenum. The abbreviation 35NLT refers to a cobalt-based superalloy produced by a melt practice that results in improved fatigue life for wires and electrodes used in the medical field. In additional embodiments, other suitable biocompatible, electrically conducting materials can similarly be used to cover the surface of the distal end 306 of the cylindrical core 220 in the EM sensor 300.

[0034] FIGS. 4A-4B show 3D perspective views illustrating a modification of the EM sensor 300 according to one embodiment. More specifically, FIG. 4A shows a 3D perspective view of the embodiment of the EM sensor 300 illustrated in FIG. 3, with the corresponding labeling. FIG. 4B shows a 3D perspective view of a modified EM sensor 300a in which an electrically conducting cap 402 is attached to the exposed distal end 306 of the magnetic core 220. The cap 402 has a larger diameter than the magnetic core 220 and, as such, increases the effective surface area of the exposed distal end 306 of the magnetic core serving as the reference electrode 122. The use of a reference electrode 122 having a relatively large surface area is beneficial, e.g., because the corresponding measured impedance signals tend to have a higher signal-to-noise ratio (SNR) with a larger area of the electrodes used for the measurements. Importantly, the increase of the surface area of the reference electrode 122 with the core cap 402 is achieved substantially without adversely affecting the functional footprint of the resulting modified EM sensor 300a. In some examples, an exterior surface of the core cap 402 is covered by a thin film of an electrically conducting material, e.g., selected from the group consisting of platinumiridium alloy, gold, titanium, MP35N, 35NLT, austenitic stainless steel, and tantalum.

[0035] FIG. 5 shows a 3D perspective view illustrating an EM-sensor assembly 500 that can be used in the catheter 102 according to yet another example. The assembly 500 includes the EM sensor 200 (also see FIG. 2) and a reference electrode assembly 506 attached thereto. The assembly 506 includes a metal tube 510 form-fitted onto the corresponding end portion of the EM sensor 200. The EM-sensor assembly 500 also includes an electrical lead wire 502 that is attached and electrically connected to the metal tube 510. The electrical lead wire 502 is further connected to the electrical connection 146, which enables an exposed surface of the metal tube 510 to be used as a part of the reference electrode 122 in at least some examples.

[0036] In the example shown, the metal tube 510 is capped with a metal end cap 520 as indicated in FIG. 5. The end cap 520 has a larger diameter than the metal tube 510 and, as such, increases the effective surface area of the resulting reference electrode 122. In some examples, the metal end cap 520 is optional and may be absent.

[0037] FIG. 6 shows a 3D perspective view illustrating the distal portion 101 of the catheter 102 according to one example. In the example shown, the distal portion 101 includes the EMsensor 300 described above in reference to FIG. 3. The EM sensor 300 is located in a distal-end section 610 of the elongated body 104 and is oriented parallel to the shaft 132. The distal end 306 of the magnetic core 220 of the EM sensor 300 protrudes through an end face 612 of the distal-end section 610 as indicated in FIG. 6 and, as such, is exposed to patient’s blood when the illustrated distal portion 101 is deployed in the patient’s body. During impedance measurements, the blood-exposed surface of the distal end 306 of the magnetic core 220 is operated as the reference electrode 122 as explained above.

[0038] The elongated body 104 has a lumen 620 that provides for mechanical and electrical communication between the proximal portion 106 and the distal portion 101 of the catheter 102 (also see FIG. 1). For example, the lumen 620 accommodates the electrical lead wires 208, 212, and 302 of the EM sensor 300 as indicated in FIG. 6. The lumen 620 also accommodates a plurality of electrical conductors of the electrical bus connection 138, which are variously electrically connected via the carrier arm 128 to the electrodes 118. Additionally, the lumen 620 accommodates one or more guidewires (not explicitly shown in FIG. 6) used to actuate longitudinal movement of the shaft 132. As already explained above, such longitudinal movement of the shaft 132 is used to cause the carrier arm 128 to transition between a linear configuration and a looped configuration. For illustration purposes, FIG. 6 shows the carrier arm 128 in a looped configuration.

[0039] FIG. 7 shows a 3D perspective view illustrating the distal portion 101 of the catheter 102 according to another example. The distal portion 101 illustrated in FIG. 7 is generally similar to the distal portion 101 illustrated in FIG. 6. However, the distal portion 101 illustrated in FIG. 7 includes the EM sensor 300a described above in reference to FIG. 4B, whereas the distal portion 101 illustrated in FIG. 6 includes the EM sensor 300 described above in reference to FIG. 3. As such, in the distal portion 101 illustrated in FIG. 7, the reference electrode 122 is implemented primarily using the core cap 402 (also see FIG. 4B). Description of the other labeled elements of the distal portion 101 illustrated in FIG. 7 can be found above in the description of FIG. 6.

[0040] FIG. 8 shows a 3D perspective view illustrating the distal portion 101 of the catheter 102 according to yet another example. The distal portion 101 illustrated in FIG. 8 is generallysimilar to the distal portion 101 illustrated in FIG. 6. However, the distal portion 101 illustrated in FIG. 8 includes the EM sensor assembly 500 described above in reference to FIG. 5, whereas the distal portion 101 illustrated in FIG. 6 includes the EM sensor 300 described above in reference to FIG. 3. As such, in the distal portion 101 illustrated in FIG. 7, the reference electrode 122 is implemented using the metal tube 510 and the metal end cap 520, which are described in more detail in reference to FIG. 5. Description of the other labeled elements of the distal portion 101 illustrated in FIG. 8 can be found above in the description of FIG. 6.

[0041] FIG. 9 shows a 3D perspective view illustrating the distal portion 101 of the catheter 102 according to yet another example. The distal portion 101 illustrated in FIG. 9 is generally similar to the distal portion 101 illustrated in FIG. 6. However, the distal portion 101 illustrated in FIG. 9 includes the EM sensor 200 described above in reference to FIG. 2, whereas the distal portion 101 illustrated in FIG. 6 includes the EM sensor 300 described above in reference to FIG. 3. The reference electrode 122 is implemented in the distal portion 101 illustrated in FIG. 9 using an electrical coil 910, which is described in more detail below in reference to FIG. 10. The electrical coil 910 is wound around a section of the carrier arm 128 adjacent to the end face 612 of the distal-end section 610 and is electrically connected to the electrical connection 146 using an electrical lead wire 908 (also see FIG. 1). Due to its position, the electrical coil 910 is exposed to patient’s blood when the distal portion 101 is deployed in the patient’s body.Description of the other labeled elements of the distal portion 101 illustrated in FIG. 9 can be found above in the description of FIG. 6.

[0042] FIG. 10 is a schematic diagram illustrating a cross-sectional side view of a section of the carrier arm 128 with the electrical coil 910 wound thereon according to one example. The shown section of the carrier arm 128 includes a tube 1002 that encloses the wires of the electrical bus connection 138 connecting the electrodes 118 to the voltage and waveform generator 140 (also see FIG. 1). In the example shown, the electrical coil 910 comprises a coated metal wire including a core 1010 and a coating 1012. In some examples, the wire core 1010 comprises silver, copper, nickel, and / or aluminum. The coating 1012 is made of a suitable biocompatible, conductive material, such as the above mentioned MP35N. In additional examples, other suitable materials for the coating 1012 are similarly used.

[0043] The electrical coil 910 has partial electrical insulation 1020 that covers the side of the coil facing the tube 1002 of the carrier arm 128. The insulation 1020 is bonded to the tube 1002 to fix the position of the electrical coil 910 with respect to the distal-end section 610 of the elongated body 104 (also see FIG. 9). Note that the side of the electrical coil 910 facing away from the tube 1002 does not have electrical insulation, which enables that side to function as the reference electrode 122.

[0044] In various examples, the implementation of the reference electrode 122 illustrated in FIGS. 9 and 10 provides one or more of the following benefits:(1) A single -piece electrode structure 908 / 910 offers lean manufacturing opportunities. For example, no welding of an electrical lead wire 908 to the coil 910 or additional materials are needed to secure the corresponding electrode 122 in the catheter 102. Additionally, surface texturing of the coil conductor (e.g., for lower effective impedance) can be created with the same laser that is used for insulation stripping.(2) Partial ablation of the coil-conductor insulation 1020 on the outer diameter of the coil 910 can be used both to partially strip the insulation of the coil and to fuse the remaining insulation 1020 to the tube 1002, thereby fixing the coil location relative to the EM sensor 200.(3) Convenient options are available for surface coating and / or texturing of the exposed coil metal to reduce the effective impedance of the corresponding reference electrode 122.For example, texturing can be done with the same laser used to ablate the insulation 1020 in the same technological setup.

[0045] FIG. 11 is a block diagram illustrating impedance -based mapping operations implemented in the system 100 according to one example. The impedance-based mapping operations use the reference electrode 122 implemented in accordance with any of the abovedescribed examples. In the example shown, the distal portion 101 of the catheter 102 has nine electrodes 118, which are labeled 1181- 1189- In other examples, a distal portion 101 having a different (from nine) number of electrodes 118 can similarly be used.

[0046] The distal portion 101 is deployed in a heart 14 of a patient 12. For illustration purposes, the carrier arm 128 of the catheter 102 is shown in a looped configuration. Sevensurface electrodes, labeled 71-76 and 90, respectively, are placed on the skin of the patient 12, e.g., as illustrated in FIG. 11. In the example shown, the surface electrode 90 is a large area electrode patch. In other examples, a different electrode type can be used in place of the patch 90. The surface electrodes 71-76 are implemented using six electrode patches arranged in three pairs, illustratively 71 / 72, 73 / 74, and 75 / 76. In some examples, each of such pairs is aligned along a respective one of three different axes, such as along the Front / Back, Left / Right, and Neck / Leg directions, respectively.

[0047] In operation, the three pairs 71 / 72, 73 / 74, and 75 / 76 of electrode patches are used to drive constant-amplitude sine-wave currents of three different respective frequencies from one patch to another. The dashed double-headed arrows in FIG. 11 schematically represent those currents according to one example. The position of the reference electrode 122 in the laboratoryframe Cartesian coordinates (x, y, z) is determined based on three frequency-demodulated voltages measured between the reference electrode 122 and a separate stationary reference electrode. In some examples, the surface electrode 90 is used as such separate stationary reference electrode for those measurements. In some other examples, an electrode on another catheter, which is placed in the coronary sinus, is similarly used as such separate stationary reference electrode for those measurements. As an illustration, a second catheter 60 including electrodes 61-64 is shown in FIG. 11. In one example, the electrode 64 of the catheter 60 serves as the separate stationary reference electrode for the measurements described above. Two independent measurements of the position of the reference electrode 122, one using the EM sensor 120 and the other using the measurements of demodulated voltages at the three frequencies, are used to cross-register the EM-based and impedance-based navigation coordinates. Once the cross-registration has been completed, coordinates of any other electrodes can be determined and tracked based solely on impedance measurements. For example, from that point on, the locations of the electrodes 118i- 1189 may become visible on the navigation system screen and be used to contribute to the creation of the anatomical map, thereby decreasing the map creation time due to an increase in the amount of available navigation data. Furthermore, the position and orientation of electrodes of additional catheters, including those without magnetic sensors, can subsequently be tracked within the mapped volume. For example, positions of the electrodes 61-64 of the catheter 60 can be tracked in this manner.

[0048] FIG. 12 is a flowchart illustrating a mapping and navigation method 1200 implemented in the system 100 according to one example. The method 1200 includes positioning the distal portion 101 of the catheter 102 adjacent to the tissue targeted for therapy (in a block 1202). In some examples, the targeted tissue is a heart tissue (see, e.g., the heart 14, FIG. 11). The method 1200 also includes the electronic controller 160 operating the magnetic field generator 130 and the mapping and navigation system 150 to determine the position and orientation of the EM sensor 120 with respect to the pertinent anatomic features of the patient (in a block 1204). In different examples of the block 1204, the EM sensor 120 is implemented using one of the EM sensor 200, the EM sensor 300, the EM sensor 300a, and the EM-sensor assembly 500. Operations of the block 1204 also include the mapping and navigation system 150 and / or the electronic controller 160 determining the position of the reference electrode 122, with respect to the anatomy of the patient 12, based on the fixed position of the reference electrode 122 with respect to the EM sensor 120 in the distal portion 101.

[0049] The method 1200 also includes independently determining the position of the reference electrode 112 using impedance-based navigation (in a block 1206). In some examples, operations of the block 1206 include: (i) driving sine- wave currents of three different respective frequencies from one patch to another in the three pairs 71 / 72, 73 / 74, and 75 / 76 of electrode patches; and (ii) determining the position of the reference electrode 122 based on three frequency-demodulated voltages measured between the reference electrode 122 and the surface patch electrode 90, e.g., as illustrated in FIG. 11. The method 1200 also includes crossregistering the coordinate systems corresponding to EM- and impedance -based navigation (in a block 1208). The cross-registration is performed in the block 1208 using the EM-based measurements of the position of the reference electrode 122 obtained in the block 1204 and the independent impedance -based measurements of the same position of the reference electrode 122 obtained in the block 1206.

[0050] The method 1200 also includes determining the positions of the treatment electrodes 118 with respect to the anatomy of the patient 12 using impedance-based navigation and the above-mentioned cross-registration (in a block 1210). Operations of the block 1210 include measuring the respective positions of the treatment electrodes 118 in a manner similar to the measurements performed in the block 1206 and then using the cross-registration of thecoordinate systems corresponding to EM- and impedance-based navigation performed in the block 1208 to bring in the anatomic features previously available through the EM-based navigation subsystem. The method 1200 also includes the electronic controller 160 displaying, on a display screen, the determined geometry of the distal portion 101 with respect to the anatomy of the patient 12 (in a block 1212). In some examples, operations of the block 1212 include: (i) displaying the position of the reference electrode 112 with respect to the anatomy of the patient 12 based on the results of the blocks 1204, 1206 and (ii) displaying the estimated shape of the carrier arm 128 with respect to the anatomy of the patient 12 based on the results of the block 1210.

[0051] According to an example embodiment disclosed above, e.g., in the summary section and / or in reference to any one or any combination of some or all of FIGS. 1-12, provided is a medical apparatus comprising: an elongated body passable through patient’s vasculature and including a distal portion and a proximal portion in mechanical and electrical communication with each other; an integrated EM sensor located in the distal portion and electrically connected through the elongated body to the proximal portion using a first electrical wire, a second electrical wire, and a third electrical wire, the integrated EM sensor including a first electrode and an EM coil having a magnetic core, the first electrode being electrically connected to the proximal portion via the first electrical wire, the EM coil being electrically connected to the proximal portion via the second electrical wire and the third electrical wire; and a reconfigurable carrier arm mechanically connected to the distal portion and having a plurality of second electrodes mounted thereon, the plurality of second electrodes being electrically connected to the proximal portion via an electrical bus disposed within the elongated body.

[0052] In some embodiments of the above medical apparatus, the medical apparatus is configured to: determine a position of the first electrode with respect to patient’s anatomy based on a voltage between the second electrical wire and the third electrical wire generated by the EM coil in response to an external magnetic field; independently determine the position of the first electrode based on a signal from the first electrode detected via the first electrical wire in response to periodic currents driven through a patient’s body with a plurality of third electrodes; and determine positions of the plurality of second electrodes with respect to the patient’s anatomy based on signals from the plurality of second electrodes detected via the electrical busand further based on a coordinate system cross-referenced based on the twice-determined position of the first electrode.

[0053] In some embodiments of any of the above medical apparatus, the first electrode comprises a distal end of the magnetic core extending beyond an insulative potting of the EM coil.

[0054] In some embodiments of any of the above medical apparatus, the first electrical wire is attached to an opposite proximal end of the magnetic core.

[0055] In some embodiments of any of the above medical apparatus, a surface of the distal end is covered by a film of an electrically conducting material that is different from a bulk ferromagnetic material of the magnetic core.

[0056] In some embodiments of any of the above medical apparatus, the electrically conducting material is selected from the group consisting of platinum-iridium alloy, gold, titanium, MP35N, 35NLT, austenitic stainless steel, and tantalum.

[0057] In some embodiments of any of the above medical apparatus, the first electrode further comprises an electrically conducting cap attached to the distal end of the magnetic core.

[0058] In some embodiments of any of the above medical apparatus, the distal end of the magnetic core has a first diameter; and wherein the electrically conducting cap has a second diameter that is larger than the first diameter.

[0059] In some embodiments of any of the above medical apparatus, the magnetic core comprises a first material; and wherein the electrically conducting cap a different second material.

[0060] In some embodiments of any of the above medical apparatus, the first material is a ferromagnetic material; and wherein the different second material is selected from the group consisting of platinum-iridium alloy, gold, titanium, MP35N, 35NLT, austenitic stainless steel, and tantalum.

[0061] In some embodiments of any of the above medical apparatus, the first electrode comprises a metal tube form-fitted onto an insulative potting of the EM coil.

[0062] In some embodiments of any of the above medical apparatus, the first electrode further comprises an end cap attached to the metal tube.

[0063] In some embodiments of any of the above medical apparatus, the metal tube has a first diameter; and wherein the end cap has a second diameter that is larger than the first diameter.

[0064] In some embodiments of any of the above medical apparatus, the first electrical wire is attached to the metal tube.

[0065] In some embodiments of any of the above medical apparatus, a first end of the reconfigurable carrier arm is fixedly attached to the distal portion of the elongated body; and wherein a second end of the reconfigurable carrier arm is fixedly attached to a shaft that is longitudinally movable with respect to the distal portion with a guidewire disposed within the elongated body.

[0066] According to another example embodiment disclosed above, e.g., in the summary section and / or in reference to any one or any combination of some or all of FIGS. 1-12, provided is a medical apparatus comprising: an elongated body passable through patient’s vasculature and including a distal portion and a proximal portion in mechanical and electrical communication with each other; an EM sensor located in the distal portion and electrically connected through the elongated body to the proximal portion using a first electrical wire and a second electrical wire; a reconfigurable carrier arm having a first end thereof fixedly attached to the distal portion of the elongated body and a second end thereof fixedly attached to a shaft that is longitudinally movable with respect to the distal portion with a guidewire disposed within the elongated body, the reconfigurable arm further having a plurality of first electrodes mounted thereon and electrically connected to the proximal portion via an electrical bus disposed within the elongated body; and a coil-shaped electrode wound around a section of the reconfigurable arm adjacent to the first end, the coil-shaped electrode being in a fixed position relative to the EM sensor andelectrically connected to the proximal portion via a third electrical wire disposed within the elongated body.

[0067] In some embodiments of the above medical apparatus, the medical apparatus is configured to: determine a position of the EM sensor with respect to patient’s anatomy based on a voltage between the first electrical wire and the second electrical wire generated by the EM sensor in response to an external magnetic field; independently determine the position of the coil-shaped electrode based on a signal from the coil-shaped electrode detected via the third electrical wire in response to periodic currents driven through a patient’s body with a plurality of second electrodes; and determine positions of the plurality of first electrodes with respect to the patient’s anatomy based on signals from the plurality of first electrodes detected via the electrical bus and further based on a coordinate system established based on the twice-determined position of the coil-shaped electrode.

[0068] In some embodiments of any of the above medical apparatus, the coil-shaped electrode comprises a coated wire having a metal core made of a first electrically conducting material and a coating made of a second electrically conducting material.

[0069] In some embodiments of any of the above medical apparatus, the first electrically conducting material is selected from the group consisting of silver, copper, nickel, and aluminum; and wherein the second electrically conducting material is selected from the group consisting of platinum-iridium alloy, gold, titanium, MP35N, 35NLT, austenitic stainless steel, and tantalum.

[0070] In some embodiments of any of the above medical apparatus, the medical apparatus further comprises a dielectric layer fixedly attached between the section of the reconfigurable arm and a side of the coil-shaped electrode facing the section.

[0071] With regard to the processes, systems, methods, heuristics, etc. described herein, it should be understood that, although the steps of such processes, etc. have been described as occurring according to a certain ordered sequence, such processes could be practiced with the described steps performed in an order other than the order described herein. It further should be understood that certain steps could be performed simultaneously, that other steps could be added,or that certain steps described herein could be omitted. In other words, the descriptions of processes herein are provided for the purpose of illustrating certain implementations and should in no way be construed to limit the claims.

[0072] Accordingly, it is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments and applications other than the examples provided would be apparent upon reading the above description. The scope should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the technologies discussed herein, and that the disclosed systems and methods will be incorporated into such future embodiments. In sum, it should be understood that the application is capable of modification and variation.

[0073] All terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those knowledgeable in the technologies described herein unless an explicit indication to the contrary in made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary.

[0074] Unless explicitly stated otherwise, each numerical value and range should be interpreted as being approximate as if the word “about” or “approximately” preceded the value or range.

[0075] The use of figure numbers and / or figure reference labels (if any) in the claims is intended to identify one or more possible embodiments of the claimed subject matter in order to facilitate the interpretation of the claims. Such use is not to be construed as necessarily limiting the scope of those claims to the embodiments shown in the corresponding figures.

[0076] Although the elements in the following method claims, if any, are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

[0077] Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term “implementation.”

[0078] Unless otherwise specified herein, the use of the ordinal adjectives “first,” “second,” “third,” etc., to refer to an object of a plurality of like objects merely indicates that different instances of such like objects are being referred to, and is not intended to imply that the like objects so referred-to have to be in a corresponding order or sequence, either temporally, spatially, in ranking, or in any other manner.

[0079] Unless otherwise specified herein, in addition to its plain meaning, the conjunction “if’ may also or alternatively be construed to mean “when” or “upon” or “in response to determining” or “in response to detecting,” which construal may depend on the corresponding specific context. For example, the phrase “if it is determined” or “if [a stated condition] is detected” may be construed to mean “upon determining” or “in response to determining” or “upon detecting [the stated condition or event]” or “in response to detecting [the stated condition or event].”

[0080] Throughout the detailed description, the drawings, which are not to scale, are illustrative only and are used in order to explain, rather than limit the disclosure. The use of terms such as height, length, width, top, bottom, is strictly to facilitate the description of the embodiments and is not intended to limit the embodiments to a specific orientation. For example, height does not imply only a vertical rise limitation, but is used to identify one of the three dimensions of a three-dimensional structure as shown in the figures. Such "height" would be vertical where the electrodes are horizontal but would be horizontal where the electrodes are vertical, and so on.

[0081] Also, for purposes of this description, the terms “couple,” “coupling,” “coupled,” “connect,” “connecting,” or “connected” refer to any manner known in the art or later developed in which energy is allowed to be transferred between two or more elements, and the interpositionof one or more additional elements is contemplated, although not required. Conversely, the terms “directly coupled,” “directly connected,” etc., imply the absence of such additional elements. The same type of distinction applies to the use of terms “attached” and “directly attached,” as applied to a description of a physical structure. For example, a relatively thin layer of adhesive or other suitable binder can be used to implement such “direct attachment” of the two corresponding components in such physical structure.

[0082] The described embodiments are to be considered in all respects as only illustrative and not restrictive. In particular, the scope of the disclosure is indicated by the appended claims rather than by the description and figures herein. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

[0083] The functions of the various elements shown in the figures, including any functional blocks labeled as “processors” and / or “controllers,” may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor or controller, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” or “controller” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), and nonvolatile storage. Other hardware, conventional and / or custom, may also be included. Similarly, any switches shown in the figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementer as more specifically understood from the context.

[0084] As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry); (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuit(s) withsoftware / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions); and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.” This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0085] It should be appreciated by those of ordinary skill in the art that any block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the disclosure. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

[0086] The following examples are a non-limiting list of clauses in accordance with one or more techniques of this disclosure.

[0087] Example 1. A medical apparatus, comprising: an elongated body passable through patient’s vasculature and including a distal portion and a proximal portion in mechanical and electrical communication with each other; an electromagnetic (EM) sensor located in the distal portion and electrically connected through the elongated body to the proximal portion using a first electrical wire, a second electrical wire, and a third electrical wire, the EM sensor including a first electrode and an EM coil having a magnetic core, the first electrode being electrically connected to the proximal portion via the first electrical wire, the EM coil being electrically connected to the proximal portion via the second electrical wire and the thirdelectrical wire; and a carrier arm mechanically connected to the distal portion and having a plurality of second electrodes mounted thereon, the plurality of second electrodes being electrically connected to the proximal portion via an electrical bus disposed within the elongated body.

[0088] Example 2. The medical apparatus of Example 1 , wherein the medical apparatus is configured to: determine a position of the EM sensor with respect to patient’s anatomy based on a voltage between the second electrical wire and the third electrical wire generated by the EM coil in response to an external magnetic field; independently determine the position of the first electrode based on a signal from the first electrode detected via the first electrical wire in response to periodic currents driven through a patient’s body with a plurality of third electrodes; and determine positions of the plurality of second electrodes with respect to the patient’s anatomy based on signals from the plurality of second electrodes detected via the electrical bus and further based on a coordinate system established based on the position of the EM sensor and the independently determined position of the first electrode.

[0089] Example 3. The medical apparatus of Example 1, wherein the first electrode comprises a distal end of the magnetic core extending beyond an insulative potting of the EM coil.

[0090] Example 4. The medical apparatus of Example 3, wherein the first electrical wire is attached to an opposite proximal end of the magnetic core.

[0091] Example 5. The medical apparatus of Example 3, wherein a surface of the distal end is covered by a film of an electrically conducting material that is different from a bulk ferromagnetic material of the magnetic core.

[0092] Example 6. The medical apparatus of Example 5, wherein the electrically conducting material is selected from the group consisting of platinum-iridium alloy, gold, titanium, MP35N, 35NLT, austenitic stainless steel, and tantalum.

[0093] Example 7. The medical apparatus of Example 3, wherein the first electrode further comprises an electrically conducting cap attached to the distal end of the magnetic core.

[0094] Example 8. The medical apparatus of claim 7, wherein the distal end of the magnetic core has a first diameter; and wherein the electrically conducting cap has a second diameter that is larger than the first diameter.

[0095] Example 9. The medical apparatus of claim 7, wherein the magnetic core comprises a first material; and wherein the electrically conducting cap a different second material.

[0096] Example 10. The medical apparatus of Example 9, wherein the first material is a ferromagnetic material; and wherein the different second material is selected from the group consisting of platinum-iridium alloy, gold, titanium, MP35N, 35NLT, austenitic stainless steel, and tantalum.

[0097] Example 11. The medical apparatus of Example 1 , wherein the first electrode comprises a metal tube form-fitted onto an insulative potting of the EM coil.

[0098] Example 12. The medical apparatus of Example 11, wherein the first electrode further comprises an end cap attached to the metal tube.

[0099] Example 13. The medical apparatus of Example 12, wherein the metal tube has a first diameter; and wherein the end cap has a second diameter that is larger than the first diameter.

[0100] Example 14. The medical apparatus of Example 11, wherein the first electrical wire is attached to the metal tube.

[0101] Example 15. The medical apparatus of Example 1, wherein a first end of the carrier arm is fixedly attached to the distal portion of the elongated body; and wherein a second end of the carrier arm is fixedly attached to a shaft that is longitudinally movable with respect to the distal portion with a guidewire disposed within the elongated body.

[0102] Example 16. A medical apparatus, comprising: an elongated body passable through patient’s vasculature and including a distal portion and a proximal portion in mechanical and electrical communication with each other; an electromagnetic (EM) sensor located in the distal portion and electrically connected through the elongated body to the proximal portionusing first electrical wire and a second electrical wire; a carrier arm having a first end thereof fixedly attached to the distal portion of the elongated body and a second end thereof fixedly attached to a shaft that is longitudinally movable with respect to the distal portion with a guidewire disposed within the elongated body, the carrier arm further having a plurality of first electrodes mounted thereon and electrically connected to the proximal portion via an electrical bus disposed within the elongated body; and a coil-shaped electrode wound around a section of the carrier arm adjacent to the first end, the coil-shaped electrode being in a fixed position relative to the EM sensor and electrically connected to the proximal portion via a third electrical wire disposed within the elongated body.

[0103] Example 17. The medical apparatus of Example 16, wherein the medical apparatus is configured to: determine a position of the EM sensor with respect to patient’s anatomy based on a voltage between the first electrical wire and the second electrical wire generated by the EM sensor in response to an external magnetic field; determine the position of the coil-shaped electrode based on a signal from the coil-shaped electrode detected via the third electrical wire in response to periodic currents driven through a patient’s body with a plurality of second electrodes; and determine positions of the plurality of first electrodes with respect to the patient’s anatomy based on signals from the plurality of first electrodes detected via the electrical bus and further based on a coordinate system established based on the positions of the EM sensor and the coil-shaped electrode.

[0104] Example 18. The medical apparatus of Example 16, wherein the coil-shaped electrode comprises a coated wire having a metal core made of a first electrically conducting material and a coating made of a second electrically conducting material.

[0105] Example 19. The medical apparatus of Example 18, wherein the first electrically conducting material is selected from the group consisting of silver, copper, nickel, and aluminum; and wherein the second electrically conducting material is selected from the group consisting of platinum-iridium alloy, gold, titanium, MP35N, 35NLT, austenitic stainless steel, and tantalum.

[0106] Example 20. The medical apparatus of Example 16, further comprising a dielectric layer fixedly attached between the section of the carrier arm and a side of the coilshaped electrode facing the section.

Claims

CLAIMS:

1. A medical apparatus, comprising: an elongated body (104) passable through patient’s vasculature and including a distal portion (101) and a proximal portion (106) in mechanical and electrical communication with each other; an electromagnetic “EM” sensor (120) located in the distal portion and electrically connected through the elongated body to the proximal portion using a first electrical wire (302), a second electrical wire (208), and a third electrical wire (212), the EM sensor including a first electrode (122) and an EM coil (210) having a magnetic core (220), the first electrode being electrically connected to the proximal portion via the first electrical wire, the EM coil being electrically connected to the proximal portion via the second electrical wire and the third electrical wire; and a carrier arm (128) mechanically connected to the distal portion and having a plurality of second electrodes (118) mounted thereon, the plurality of second electrodes being electrically connected to the proximal portion via an electrical bus (138) disposed within the elongated body.

2. The medical apparatus of claim 1, wherein the medical apparatus is configured to: determine a position of the EM sensor with respect to patient’s anatomy based on a voltage between the second electrical wire and the third electrical wire generated by the EM coil in response to an external magnetic field; independently determine the position of the first electrode based on a signal from the first electrode detected via the first electrical wire in response to periodic currents driven through a patient’s body with a plurality of third electrodes; and determine positions of the plurality of second electrodes with respect to the patient’ s anatomy based on signals from the plurality of second electrodes detected via the electrical bus and further based on a coordinate system established based on the position of the EM sensor and the independently determined position of the first electrode.

3. The medical apparatus of claim 1, wherein the first electrode comprises a distal end (306) of the magnetic core extending beyond an insulative potting (230) of the EM coil.

4. The medical apparatus of claim 3, wherein the first electrical wire is attached to an opposite proximal end (304) of the magnetic core.

5. The medical apparatus of claim 3, wherein a surface of the distal end is covered by a film of an electrically conducting material that is different from a bulk ferromagnetic material of the magnetic core.

6. The medical apparatus of claim 5, wherein the electrically conducting material is selected from the group consisting of platinum-iridium alloy, gold, titanium, MP35N, 35NLT, austenitic stainless steel, and tantalum.

7. The medical apparatus of claim 3, wherein the first electrode further comprises an electrically conducting cap (402) attached to the distal end of the magnetic core.

8. The medical apparatus of claim 7, wherein the distal end of the magnetic core has a first diameter; and wherein the electrically conducting cap has a second diameter that is larger than the first diameter.

9. The medical apparatus of claim 7, wherein the magnetic core comprises a first material; and wherein the electrically conducting cap a different second material.

10. The medical apparatus of claim 9, wherein the first material is a ferromagnetic material; and wherein the different second material is selected from the group consisting of platinumiridium alloy, gold, titanium, MP35N, 35NLT, austenitic stainless steel, and tantalum.

11. The medical apparatus of claim 1 , wherein the first electrode comprises a metal tube (510) form- fitted onto an insulative potting of the EM coil.

12. The medical apparatus of claim 11, wherein the first electrode further comprises an end cap (520) attached to the metal tube.

13. The medical apparatus of claim 12, wherein the metal tube has a first diameter; and wherein the end cap has a second diameter that is larger than the first diameter.

14. The medical apparatus of claim 11, wherein the first electrical wire (502) is attached to the metal tube.

15. The medical apparatus of claim 1, wherein a first end of the carrier arm is fixedly attached to the distal portion of the elongated body; and wherein a second end of the carrier arm is fixedly attached to a shaft (132) that is longitudinally movable with respect to the distal portion with a guidewire disposed within the elongated body.

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