Hybrid Approach to Distortion Detection

Abstract

A system for distinguishing between magnetic field distortion and physical motion in a hybrid magnetic and impedance tracking system may include a first drive patch (31) and a second drive patch (32) configured to generate an electric field in the body to locate an electrode (124) on a medical device (106), a magnetic positioning system configured to generate a magnetic field, a magnetic sensor (300) configured to receive a signal from the magnetic positioning system, and an electronic control unit configured to receive position data from the impedance positioning system and magnetic sensor position data from the magnetic positioning system, and may be configured to detect a position change of the magnetic sensor and use the drive patch position data and the magnetic sensor position data to determine whether the detected position change of the magnetic sensor is caused by magnetic field distortion or physical motion.

Description

Technical Field

[0001] The present disclosure relates generally to positioning of medical devices within the human body. More specifically, the present disclosure relates to detecting and distinguishing magnetic field distortion and position change distortion in a hybrid magnetic tracking and impedance-based tracking system. Background Art

[0002] Electrophysiology (EP) catheters have been used in an increasing number of procedures. For example, catheters have been used in diagnostic, therapeutic, mapping, and ablation procedures, to name a few. Typically, a catheter is manipulated through a patient's vasculature to a desired site, such as a site within the patient's heart, and carries one or more electrodes that can be used for diagnosis, mapping, ablation, or other treatment. Precise positioning of the catheter and knowledge by the clinician of the precise location within the patient's body are required to improve procedural success rates.

[0003] In order to position the catheter at the desired location in the body, some type of positioning system must be used. In order to determine the relative position of the catheter to the patient's anatomy, magnetic positioning systems have been developed that provide the catheter position within a well-known controlled magnetic field, and impedance positioning systems have been developed that use electrical currents to provide the position of the catheter within three electrode pairs. The externally generated magnetic field includes precise magnetic gradients (field lines) that are sensed by the catheter (e.g., by an element such as a coil) located within the magnetic field. The current induced in the sensor by the magnetic field is analyzed using an algorithmic process and used to determine the position of the catheter within the patient's body. Once the catheter is positioned within the patient's body as desired, the clinician can operate the catheter, for example, to ablate tissue to interrupt a potentially pathogenic heart rhythm.

[0004] However, magnetic positioning systems are susceptible to errors caused by magnetic distortion within the magnetic field, caused by, for example, foreign ferrous or metallic objects intruding into the magnetic field. The introduction of such distortion can cause the system to present an inaccurate position of the catheter within the patient. Summary of the invention

[0005] It is desirable to provide a system for determining the position of a medical device within the body. In particular, it is desirable to provide a system that will reduce position errors.

[0006] In one embodiment, a system for distinguishing between magnetic field distortion and physical motion in a hybrid magnetic and impedance tracking system for navigating a medical device within a patient may include: an impedance positioning system including a first drive patch and a second drive patch configured to be coupled to an external surface of the patient's body, the first and second drive patches configured to generate an electric field within the body for locating electrodes on the medical device; a magnetic positioning system configured to generate a magnetic field; a magnetic sensor coupled to one of the first and second drive patches and configured to receive a signal from the magnetic positioning system; and an electronic control unit configured to receive drive patch position data from the impedance positioning system and magnetic sensor position data from the magnetic positioning system. The electronic control circuit may be configured to detect a change in position of the magnetic sensor and use the drive patch position data and the magnetic sensor position data to determine whether the detected change in position of the magnetic sensor is caused by magnetic field distortion or physical motion of the magnetic sensor.

[0007] In another embodiment, a system for distinguishing magnetic field distortion and physical movement in a hybrid magnetic and impedance tracking system for navigating a medical device in a patient may include: a magnetic positioning system configured to generate a magnetic field; a magnetic sensor including a first sensor coil, a second sensor coil oriented orthogonally to the first sensor coil, and a third sensor coil oriented orthogonally to the first and second sensor coils, and configured to receive a signal from the magnetic positioning system; a plurality of impedance patches configured to generate an electric field in the patient for locating electrodes on the medical device; and an electronic control unit configured to receive information from the magnetic sensor and the plurality of impedance patches. The electronic control unit may be configured to determine a magnetic sensor vector and an impedance vector, the electronic control circuit may be configured to detect a change in position of the magnetic sensor, and use the magnetic sensor vector and the impedance vector to determine whether the detected change in position is caused by magnetic field distortion or physical movement of the magnetic sensor, and the electronic control unit may be configured to initiate a correction algorithm, wherein the correction algorithm is configured to correct the change in position of the medical device based on the magnetic field distortion or by physical movement of the magnetic sensor.

[0008] In yet another embodiment, a method for distinguishing between magnetic field distortion and physical motion in a hybrid magnetic and impedance tracking system for navigating a medical device within a patient may include: receiving a first set of one or more signals from a magnetic sensor at a first time indicating a magnetic field sensed by each of a plurality of sensor coils within the magnetic sensor; receiving a first set of one or more signals from an impedance sensor indicating a position within a coordinate system; receiving a second set of one or more signals from the magnetic sensor at a second time indicating a magnetic field sensed by each sensor coil; receiving a second set of one or more signals from the impedance sensor indicating a position within a coordinate system; determining a magnetic sensor vector; determining an impedance vector; detecting a change in position of the magnetic sensor; comparing the magnetic sensor vector to a first threshold and comparing the impedance vector to a second threshold to determine whether the detected change in position of the magnetic sensor is caused by magnetic field distortion or because physical motion of the magnetic sensor has occurred. If the magnetic sensor vector exceeds the first threshold and the impedance vector is below the second threshold, the detected change in position may be caused by magnetic field distortion; and if the magnetic sensor vector exceeds the first threshold and the impedance vector exceeds the second threshold, the detected change in position may be caused by physical motion of the magnetic sensor.

[0009] The foregoing and other aspects, features, details, utilities and advantages of the present invention will become apparent by reading the following description and claims and by examining the accompanying drawings. Additional features, advantages and embodiments of the present disclosure may be set forth or apparent by considering the detailed description and the accompanying drawings. In addition, it should be understood that the foregoing brief summary and the following detailed description, drawings and appendices are intended to provide further explanation, but not to limit the scope of the present disclosure as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic diagram of a hybrid magnetic and impedance tracking system consistent with various aspects of the present disclosure.

[0011] Figure 2A is a partial isometric view of a catheter assembly including a catheter and an introducer configured for positioning in a hybrid magnetic and impedance tracking system consistent with various aspects of the present disclosure.

[0012] Figure 2B is consistent with all aspects of the present disclosure Figure 2A An enlarged partial side view of the distal tip assembly of a catheter.

[0013] Figure 3A is a top view of a magnetic detection sensor consistent with various aspects of the present disclosure with portions of the sensor housing broken away to show internal features.

[0014] Figure 3B is consistent with all aspects of the present disclosure Figure 3AAn isometric view of a magnetic detection sensor.

[0015] Figure 3C It is consistent with various aspects of the present disclosure to Figure 3A and 3B An enlarged top view of an embodiment of a magnetic detection sensor separated from the sensor coil array configuration.

[0016] Figure 3D A flow chart detailing a method of calculating an amplitude position and orientation associated with the mechanical position and orientation of sensor coils relative to each other is shown.

[0017] Figure 4 An isometric view of the placement of magnetic sensors on an impedance patch in a hybrid magnetic and impedance tracking system.

[0018] Figure 5 is a side view of placing a magnetic detection sensor on a patient during a medical procedure consistent with various aspects of the present disclosure.

[0019] Figures 6A-6C are diagrammatic representations of several embodiments of systems experiencing distortion. DETAILED DESCRIPTION

[0020] Cardiac positioning systems are able to display the three-dimensional (3D) position of conventional electrophysiology catheters within an overlaid model or image of the heart chambers. These positioning systems can also display cardiac electrical activity as waveform traces and dynamic 3-D isoelectric maps on models of the heart chambers. The contoured surfaces of these 3D models are based on the anatomy of the patient's own heart chambers. These positioning systems can use impedance-based and / or magnetic-based positioning techniques to present catheter positions and model creation.

[0021] When magnetic positioning is used, the magnetic field generated from a local source is inherently susceptible to distortion caused by the intrusion of metal or ferrous objects or their placement in the vicinity of the generated magnetic field. Such distortion may cause inaccuracies in the calculated or determined position of the medical device and associated anatomical models and other representations. In addition, when using magnetic positioning systems and impedance positioning systems, patient motion may cause distortions and inaccuracies in the calculated or determined position of the medical device and associated anatomical models and other representations. The navigation system can use various sensors to monitor the patient's motion in order to compensate for such motion when determining the position of the medical device. In addition, as discussed herein, the navigation system can pair magnetic sensors and impedance sensors to determine whether magnetic distortion or patient motion has occurred.

[0022] Magnetic sensors embedded in intracardiac devices are used to determine the position and orientation of the device relative to one or more known reference positions. These devices may include catheters, sheaths, guidewires, and other devices known to those of ordinary skill in the art. In addition, impedance sensors embedded in intracardiac devices can be used to determine the position and orientation of such devices. This position and orientation information can be used to navigate the device and can also be used to optimize the positioning of the device based on magnetism and impedance. When navigating a medical device in space, the displayed or otherwise reported position of the device can be significantly offset (e.g., visually offset on a screen showing a representation of the position of the device) when the underlying magnetic field changes / distorts, or the position of the patient changes (although there is no actual change (or minimal actual change) in the physical position of the device in the patient). It can be understood that such offsets may cause the model created using the reported position of the device to be inaccurate. The magnetic position and orientation data from the device can also be used in conjunction with impedance-based positioning techniques and used to optimize / scale nonlinear impedance fields. As described in more detail below with reference to the accompanying drawings, embodiments of the present disclosure identify the presence of such distortions in the magnetic field and changes in readings due to patient movement, the presence of other devices inserted into the patient, and interference from the surrounding environment. Embodiments of the present disclosure may further differentiate between distortions within the magnetic field and changes in readings due to patient motion after determining that distortion or motion is present.

[0023] Figure 1 The human anatomy used to navigate a patient 11 during a medical procedure is shown (for simplicity, the Figure 1 Schematic diagram of a hybrid magnetic and impedance tracking system 8 (depicted as an ellipse in FIG. 1 ). For example, Figure 1 As shown, the system 8 can be used to map a patient's heart 10 and navigate a cardiac catheter through the chambers of the heart. The hybrid magnetic and impedance tracking system 8 determines whether an object (e.g., a portion of a diagnostic or ablation catheter, such as Figure 2A and 2B The hybrid magnetic and impedance tracking system 8 can be used to determine the position (and, in some embodiments, orientation) of an electrode assembly 112 (depicted in FIG. 1 ) typically in a three-dimensional space, and represent these positions as position information determined relative to at least one reference. Specifically, the hybrid magnetic and impedance tracking system 8 can be used to determine the position of a cardiac catheter within a magnetic and / or impedance field, and then superimposed on, for example, an image or model of the heart 10. In other embodiments, magnetic resonance imaging data and other reference data can be superimposed on the three-dimensional space to provide a clinician with a virtual working environment in which the real-time position of the cardiac catheter relative to the patient's heart 10 is referenced.

[0024] The hybrid magnetic and impedance tracking system 8 may include various visualization, localization, mapping, and navigation components. For example, the hybrid magnetic and impedance tracking system 8 may include, in part, a magnetic field-based system such as the CARTOTM The hybrid magnetic and impedance tracking system 8 may include, in part, a magnetic field-based system, such as the MEDIGUIDE 3000 system available from Abbott Laboratories, as shown generally in reference to one or more of U.S. Patent Nos. 6,498,944, 6,788,967, and 6,690,963, the disclosures of which are hereby incorporated by reference in their entirety as if fully set forth herein. In another embodiment, the hybrid magnetic and impedance tracking system 8 may include, in part, a magnetic field-based system, such as the MEDIGUIDE 3000 system available from Abbott Laboratories, TM Technical systems, generally shown in reference to one or more of U.S. Patent Nos. 6,233,476; 7,197,354; 7,386,339; U.S. Patent Application No. 14 / 208,120, entitled “Medical Device Navigation System,” filed on March 13, 2014, U.S. Provisional Patent Application No. 61 / 834,223, entitled “Medical Device Navigation System,” filed on June 12, 2013, and International Application No. PCT / IB2014 / 059709, entitled “Medical Device Navigation System,” filed on March 13, 2014, the disclosures of which are hereby incorporated by reference in their entirety as if fully set forth herein. In yet another embodiment, the hybrid magnetic and impedance tracking system 8 may include a hybrid electric field-based and magnetic field-based system, such as, but not limited to, the systems described in co-pending U.S. Patent Application No. 13 / 231,284, filed on September 13, 2011, entitled “Catheter Navigation Using Impedance and Magnetic Field Measurements” and U.S. Patent Application No. 13 / 087,203, filed on April 14, 2011, entitled “System and Method for Registration of Multiple Navigation Systems to a Common Coordinate Frame,” each of which is hereby incorporated by reference in its entirety as if fully set forth herein, or the CARTO SYSTEM commercially available from Biosense Webster. TM 3 system. In some embodiments, the hybrid magnetic and impedance tracking system 8 may include or be used in combination with other commonly available systems, such as, but not limited to, fluoroscopy, computed tomography (CT), and magnetic resonance imaging (MRI) based systems. For purposes of clarity and illustration only, the positioning system 8 will be described below as including a hybrid magnetic and impedance tracking system.

[0025] The hybrid magnetic and impedance tracking system 8 may include various visualization, localization, mapping, and navigation components. For example, the hybrid magnetic and impedance tracking system 8 may include, in part, an impedance localization system and / or a hybrid magnetic and impedance tracking system, such as EnSite TM NavX TM Electroanatomical mapping system, EnSite TM Velocity TM Electroanatomical Mapping Systems and EnSitePrecision TM Electroanatomical mapping systems, all commercially available from Abbott Laboratories, or generally referred to by reference to U.S. Patent No. 7,263,397 (the '397 patent), or U.S. Patent Publication No. 2007 / 0060833 A1, U.S. Application No. 11 / 227,580, filed September 15, 2005 (the '580 application), or U.S. Publication No. 2018 / 0296111 A1, U.S. Application No. 15 / 953,155, filed April 13, 2018 (the '155 application). The '397 patent, the '580 application, and the '155 application are all incorporated herein by reference as if fully set forth herein. Various EnSite TM The system is based on the principle that when an electric current is passed through the chest, a voltage drop occurs across internal organs (such as the heart), and this voltage drop can be measured and used to determine the location of the medical device within the body.

[0026] Figure 1 A hybrid positioning system comprising two positioning systems (an impedance-based positioning system and a magnetic-based positioning system) can be further exemplified. Figure 1 As shown, the hybrid magnetic and impedance tracking system 8 may include multiple magnetic field transmitters (e.g., 12, 14, 16, 18, 19, and 21) that transmit a magnetic field across the patient's body 11. These magnetic field transmitters, which can be placed on the patient or attached / applied to the patient, or fixed to an external device, define three substantially orthogonal axes, such as the x-axis, the y-axis, and the z-axis. The magnetic field transmitters are electrically coupled to a magnetic field generator. The magnetic field generator generates one or more magnetic fields that can be simultaneously transmitted, time-division multiplexed, and / or frequency-division multiplexed by the magnetic field transmitters. The switch 13 samples signals received from one or more receivers 17, 22, and 31 (e.g., catheters, patient reference sensors, internal reference sensors, magnetic sensors, etc.).

[0027] The system can additionally include three pairs of patch electrodes placed on opposing surfaces of the body (e.g., chest and back, left and right sides of the chest, and neck and legs) and forming substantially orthogonal x, y, and z axes, and a reference electrode, which is typically placed near the stomach and provides a reference value and serves as the origin of the navigation system coordinate system. Figure 1 Two pairs of these orthogonally positioned driven patches 31, 32, 33, 34 are shown. A sinusoidal current can be driven through each pair of patch electrodes to create an electric field and a voltage measurement of one or more electrodes associated with the medical device can be obtained. The measured voltage is proportional to the distance between the device electrode and the patch electrode. The measured voltage is compared to the potential at the reference electrode and the position of the device electrode within the navigation system coordinate system is determined.

[0028] The received signal from the receiver indicating the magnetic field from one or more transmitters passing through the patient's body 11, and / or the impedance data from the plurality of drive patches are then converted from analog to digital signals for further processing by the computer system 7. The computer system 7 performs calculations on the data received from the receiver and / or the drive patches to determine, for example, the position of the cardiac catheter in the patient's heart. In the illustrated embodiment, the computer system can be coupled to the magnetic tracking system and the impedance tracking system. In other embodiments, the magnetic tracking system and the impedance tracking system can be coupled to separate devices, or additional components can be present in the system. In addition, the actual catheter position may be obscured by magnetic distortions in the magnetic field caused by other ferrous / metallic bodies. These magnetic distortions are associated with the error rate of the perceived position of the catheter compared to the actual position of the catheter. The computer may additionally include an electronic control unit. As described throughout the application, the computer can receive, calculate, determine and send data from the various devices and systems described herein.

[0029] For the clinician's reference during the procedure, the sensed position of the catheter within the magnetic field may be presented on the display 6 relative to a known reference point (eg, heart chamber, artery, etc.).

[0030] In one embodiment, a medical device such as a catheter can be extended into the left ventricle of the patient's heart 10. In other embodiments, the medical device can be extended to the left atrium, the coronary sinus, the pulmonary vein, or another artery, vein, or lumen in the body. In some of these embodiments, the medical device can be used outside the vascular system. The catheter includes a plurality of sensor coils and electrodes spaced apart along its length. As used herein, the term "sensor coil" generally refers to any element (e.g., a magnetic sensor) whose position in a magnetic field can be measured by the system. Because each sensor coil is located in the magnetic field, positioning data can be collected for each sensor coil at the same time. In addition, each electrode is located in the field created by the impedance-driven patch, and positioning data can also be collected for each electrode at the same time.

[0031] The hybrid magnetic and impedance tracking system 8 may include a fixed reference 22 to define the origin of the coordinate system of the magnetic-based positioning system. This fixed reference provides a relative position relative to which the position of the sensor coil on the catheter is measured. Such a fixed reference can also be located at a fixed internal or external location. Similarly, multiple references can be used for the same or different purposes (e.g., to correct for breathing, patient displacement, system drift, etc.). If the fixed reference includes a magnetic reference sensor, the magnetic reference sensor may be susceptible to metal interference and physical movement of the magnetic reference sensor, whether through patient movement, skin movement or stretching, accidental movement, or other methods. In addition, because the fixed reference 22 is used to define the origin of the magnetic-based positioning system coordinate system, physical movement of the fixed reference will not be observed in the tracking tool position data. The combination of magnetic field distortion and physical movement of the fixed reference 22 may require a system that can distinguish between error types. The present system can distinguish between physical patient movement and perceived movement caused by magnetic field distortion by using a combination of position data from an impedance-based navigation system and magnetic position data from a magnetic-based navigation system. The magnetic reference sensor can be physically connected to a patch applied to the patient or other device that allows the use of a hybrid magnetic and impedance tracking system (i.e., EnSite Precision TM ) device for tracking. Since the positions of the patch and the magnetic reference sensor are now linked together, the relative positions of the patch and the magnetic reference sensor can be monitored. As described herein, if the impedance position data of the patch or other impedance device and the magnetic reference sensor position data move together, this can be attributed to patient (physical) movement. However, if the reference magnetic position data changes, while the impedance position data does not change, it can be determined that the magnetic reference sensor is disturbed by interference.

[0032] A computer system, which may include a conventional general purpose computer, a special purpose computer, a distributed computer, or any other type of computer, and may include one or more processors, such as a single central processing unit (CPU) or multiple processing units, commonly referred to as a parallel processing environment, can control the hybrid magnetic and impedance tracking system 8 and / or execute instructions to practice various aspects of the embodiments described herein.

[0033] Figure 2A2 is a simplified isometric view of a catheter assembly 100, including a catheter 106, which includes a catheter tip assembly (or electrode assembly or distal tip assembly) 112 at a distal portion and is operably adapted to perform a diagnostic or therapeutic procedure under the control of a clinician. The proximal portion 104 of the catheter 106 may include a joystick or other mechanism (not shown). In the present embodiment, the catheter 106 is a mapping catheter. The catheter 106 includes a flexible shaft 102 extending between the proximal portion 104 and the catheter tip assembly 112. The catheter assembly 100 also includes an electrical connector (not shown) configured to establish an electrical connection between the catheter tip assembly 112 and an external electronic assembly (not shown) to perform, for example, positioning, mapping, ablation and / or pacing procedures. FIG. 2 also shows an introducer 114 that includes a portion of the catheter assembly 100. The catheter tip assembly 112 may include a plurality of sensor coils (or positioning coils or sensors), such as, for example, in the present application. Figure 3A , 3B and 3C, or the sensors shown in U.S. Pat. No. 6,690,963 (see, for example, sensors 30, 32, 34 depicted in FIGS. 2 and 3), which are incorporated herein by reference as if fully set forth herein. For example, these localization coils may be located Figure 2B In the area shown by the dotted box 122 in FIG.

[0034] Figure 2B An enlarged side view of the tip assembly 112 is shown in more detail. The tip assembly 112 includes a tip electrode 124 ( Figure 2B 128R-2, 128R-3, and 128R-4; and a plurality of electrical conductors 120 (e.g., one conductor electrically connected to each of the three ring electrodes and a separate conductor electrically connected to the tip electrode 124). If the positioning coil is located in the area depicted by the dashed box 122, for example, additional electrical connectors can extend proximally from the tip assembly 112.

[0035] Figure 3A and 3B 3 is a diagram of one embodiment of a magnetic sensor 300 including a circuit board 310 electrically coupled to a first sensor coil 315, a second sensor coil 320, and a third sensor coil 325, respectively. In some embodiments, the magnetic sensor may include a fixed reference to define the origin of a coordinate system of a magnetic-based positioning system. In other embodiments, the magnetic sensor may include a reference to a magnetic field. Figure 3A and 3BMore or fewer sensor coils used in. In one embodiment, the magnetic sensor may include 5 sensor coils. In another embodiment, the magnetic sensor may include 6 sensor coils. Each sensor coil is fixed relative to the magnetic sensor housing 305 and the circuit board 310, and in the illustrated embodiment, the sensor coils are fixed in orthogonal orientations relative to each other. In other embodiments, the sensor coils may be fixed in different orientations. In some embodiments, the sensor coils may include parallel, offset or additional orientations. During operation, the magnetic sensor 300 is placed in the generated magnetic field, and each of the individual sensor coils receives energy indicating the magnetic field strength and orientation. In a specific embodiment, the vector sum of the received energy is calculated to determine the perceived changes in the positions of the sensor coils relative to each other. The perceived changes indicate magnetic distortion in the magnetic field near the magnetic sensor. In medical magnetic positioning applications (as discussed in more detail above), such magnetic distortion affects the ability of the system to accurately locate, for example, the position of a catheter in a patient's body.

[0036] Before transmitting the received signals from the first sensor coil 315, the second sensor coil 320, and the third sensor coil 325 to the computing circuit for processing and determining the amount of magnetic field distortion, the circuit within the circuit board 310 can perform many signal processing functions, including, for example, analog-to-digital conversion, preamplification, and signal noise filtering. After signal processing, the received signals are transmitted to the magnetic positioning system processor circuit via the cable 330, which is coupled to the circuit board 310 via the pad 335. In further embodiments, the magnetic sensor can wirelessly transmit the received signals from each sensor coil to the processor circuit of the magnetic positioning system using a wireless data transmission protocol known to those skilled in the art.

[0037] Figure 3C An embodiment of a sensor coil array 370 (including a first sensor coil 315, a second sensor coil 320, and a third sensor coil 325, respectively) is shown, which is connected from the housing 305, the circuit board 310, and Figure 3A and 3B Other components shown are exploded. Figure 3C As shown, the sensor coils are oriented orthogonally to each other and are fixed at precise distances from each other. As described above, while the illustrated embodiments of the sensor coils are oriented orthogonally to each other, additional orientations are possible. During operation of the magnetic sensor in a magnetic field, the output of the sensor coil array is used to calculate an amplitude position and orientation associated with the mechanical position and orientation of the sensor coils relative to each other.

[0038] Figure 3D One method of calculating the amplitude position and orientation associated with the mechanical position and orientation of the sensor coils relative to each other is shown.

[0039] In step 381, a vector sum of the distances between the centers of the longitudinal axes of the three sensor coils is calculated at a first time. The vector sum may also be considered an initial indicator value. In response to distortions in the magnetic field, the sensed position of one (or more) of these sensor coils may shift from its known / fixed position relative to the other sensor coils. As a result, the corresponding vector sum may be affected accordingly.

[0040] In step 383, an updated vector sum of the distances between the centers of the longitudinal axes of the three sensor coils is calculated at a second time. The updated vector sum can also be considered as a current index value.

[0041] In step 385, the change between the initial vector φ and the updated vector φ may be determined.

[0042] In step 387, the change between the initial vector sum and the updated vector sum can be compared to a determined threshold. The determined threshold can indicate distortion of the generated magnetic field. Such distortion can make readings from the generated magnetic field unreliable.

[0043] In step 389, it is determined whether the generated magnetic field is distorted.

[0044] In further embodiments, after an initial index value is determined (where the magnetic field is not distorted), subsequent amplitude positions and orientations may be correlated in time. As described above, these later amplitude values ​​may differ from the initial index value due to local magnetic distortion within the magnetic field, resulting in a perceived shift in the position and orientation of the sensor coils relative to each other (even if the orientation and position of the sensor coils relative to each other are fixed). The initial index value may be compared to subsequent index values ​​to determine when an acceptable level of magnetic field distortion during a medical procedure is exceeded. The delta value (the change in value between the initial index value and the subsequent index value) is associated with a distortion-related drift in catheter positioning.

[0045] In one embodiment, an acceptable incremental magnetic distortion value (e.g., a soft threshold) may be determined by a clinician and / or an acceptable incremental magnetic distortion value (e.g., a hard threshold) may be determined by a processor circuit. In another embodiment, an acceptable incremental magnetic distortion value may be preset within the system. In yet another embodiment, the system may suggest one or more acceptable incremental magnetic distortion values ​​based on various factors for the clinician to select. In one such embodiment, the magnetic positioning system may indicate that the distortion is affecting the perceived position of the catheter within the patient when the soft threshold is exceeded, but continue to display the perceived position of the catheter on the display. In another embodiment, when the incremental value of the indicator value exceeds the hard threshold, the magnetic positioning system can no longer update the display with the newly calculated perceived position of the catheter due to inaccurate perception of the position information. This information may be communicated to the clinician using auditory, visual, tactile, or other sensory feedback. In some embodiments, this operation may be referred to as a magnetic mode. The magnetic mode may include stopping displaying the position of the medical device or providing a visual indicator showing that the position is no longer accurate. In some embodiments, the visual indicator may include a ghosting image or a flashing electrode to illustrate that the position is no longer accurate. In other embodiments, the hybrid magnetic and impedance tracking system may restore or limit position sensing to impedance position data only when the system detects that the delta value exceeds a hard threshold and the magnetic positioning system is unable to update the display. In one embodiment, the hybrid magnetic and impedance tracking system may automatically change the position sensing of the medical device to rely solely on impedance position sensing when the system determines that magnetic distortion is affecting the system. In other embodiments, the hybrid magnetic and impedance tracking system may signal the user that magnetic distortion is present, and the user may then select the option to proceed by sensing only impedance position data for the medical device. In some embodiments, this operation may be referred to as impedance mode. In various embodiments, the impedance position sensing mode may continue until the magnetic distortion is no longer affecting the system, at which point the system may automatically switch back to using the same magnetic tracking system as before the magnetic distortion was present. In other embodiments, the impedance position sensing mode may continue until the magnetic distortion is no longer affecting the system, at which point the system may signal the user if they want to switch back to using the same magnetic tracking system as before the magnetic distortion was present. In other embodiments where the switch to impedance-only mode does not occur, the magnetic positioning system may resume updating the display using the sensed position of the catheter within the patient once the calculated index value falls back below the hard threshold. In other embodiments, when the incremental value of the indicator value exceeds the hard threshold, the system can continue to display the sensed position of the catheter on the display. In various embodiments, the system can display it to the clinician, as described herein.

[0046] like Figure 3CAs shown, a specific experimental / detailed configuration of the sensor coil array 370 is presented. The first sensor coil 315 is oriented orthogonal to both the second sensor coil 320 and the third sensor coil 325. Therefore, each sensor coil is oriented to be in a plane with one of the three-dimensional axes and receives magnetic field energy substantially coaxial with the sensor coil. In the illustrated embodiment, the center point of the first coil can be spaced 5.596 millimeters (mm) from the center point of the second sensor coil, and the center point distance between the first and second sensor coils and the center point distance between the third and second sensor coils can be 3.006 mm, the angular offset of the second and third sensor coils relative to the first sensor coil is 22 degrees, and the angular offset of the first and third sensor coils relative to the second sensor coil is also 22 degrees. In other embodiments, other relative positions and orientations of the sensor coil array can also be used.

[0047] In utilizing the sensor coil array 370 (eg Figure 3C During operation of the magnetic positioning system of FIG. 1 , the calculated amplitude value of the sensed magnetic field relies on a fixed spacing of the sensor coils to determine when magnetic distortion in the magnetic field causes excessive offset in the catheter position data.

[0048] While magnetic sensors as described herein can be used by themselves to detect magnetic field distortion, there may be situations where the distortion causes all coils within the magnetic sensor to move in the same direction. As a result, the distortion cannot be properly detected. To mitigate these situations, at least one magnetic sensor can be placed on at least one impedance patch.

[0049] Figure 4An isometric view of multiple magnetic sensors disposed on multiple impedance patches in a hybrid magnetic and impedance tracking system 401 is shown. In the illustrated embodiment, a first magnetic sensor 403 may be placed on a first impedance patch 405, a second magnetic sensor 407 may be placed on a second impedance patch 409, and a third magnetic sensor 411 and a fourth magnetic sensor 413 may be placed on a third impedance patch 415. In the illustrated embodiment, the third impedance patch 415 may include a reference patch. In addition, as shown, the third impedance patch 415 may include two magnetic sensors coupled thereto. In various embodiments, the magnetic sensors may be disposed on different patches within an orthogonal patch system. In one embodiment, a first magnetic sensor may be disposed on a neck patch, a second magnetic sensor may be disposed on a right side patch, and the third and fourth magnetic sensors may be disposed on a reference electrode. In another embodiment, a first magnetic sensor may be disposed on a chest patch, a second magnetic sensor may be disposed on a back patch, a third magnetic sensor may be disposed on a right side patch, and a fourth magnetic sensor may be disposed on a reference electrode. In other embodiments, additional arrangements and numbers of magnetic sensors may be placed on the impedance sensors. The impedance patch may be placed on the patient as described throughout this application.

[0050] Figure 5 An embodiment of a hybrid distortion detection system 501 is shown. The illustrated system depicts the placement of magnetic sensors on impedance patches relative to a patient 513 during a medical procedure utilizing magnetic positioning of a medical device within a patient. The illustrated embodiment depicts one possible placement of a front impedance patch 503, a rear impedance patch 505, and a reference impedance patch 507. The illustrated embodiment also includes a first magnetic sensor 519 coupled to the front impedance patch 503, a second magnetic sensor 521 coupled to the rear impedance patch 505, and a third magnetic sensor 523 coupled to the reference impedance patch 507. In this embodiment, the front impedance patch 503 is placed in front of the patient 513 (e.g., on the patient's chest), while the rear impedance patch 505 is placed behind the patient (e.g., between the patient's back and the operating table 517). As described herein, the impedance system may also include additional orthogonally oriented patches (not shown). In one embodiment, the first magnetic sensor and the second magnetic sensor are ideally positioned adjacent to (and opposite to) the anatomical structure of the patient on which the procedure is being performed. As Figure 5 As shown, first and second magnetic sensors are opposed to each other relative to a heart 515 that is being treated via a catheter 511 that extends into the heart.

[0051] As described herein, the magnetic field transmitter surrounding the patient emits a magnetic field for determining the position of the catheter. Specifically, the catheter, including a coil in its tip region, senses a magnetic field near the coil. Then, the processing circuit can determine the position of the coil in the magnetic field based on the magnetic field sensed at the catheter tip, thereby determining the position of the catheter tip. In addition, the impedance patch can be used to determine the position of at least one electrode on the catheter. However, other iron objects entering the magnetic field will create magnetic distortion in the field, thereby affecting the positioning of the catheter in the field. The patient's additional movement will also affect the positioning of the catheter in the field. Therefore, the first magnetic sensor 519 detects magnetic distortion near the front of the patient (for example, medical equipment and instruments), and the second magnetic sensor 521 detects magnetic distortion near the back of the patient (for example, iron objects associated with the operating room table, or other objects in the magnetic field below). In such a configuration, magnetic distortion can be identified and the effect of magnetic distortion on the catheter can be determined (for example, whether the magnetic field near the catheter is overly affected by magnetic distortion). Since at least one magnetic sensor is arranged on the impedance patch, additional information about magnetic field distortion and patient movement can also be determined.

[0052] During a medical procedure, multiple impedance patches and multiple sensor coils can be placed within a magnetic field. Each corresponding sensor coil in each corresponding magnetic field distortion sensor can receive energy indicating magnetic field strength and orientation. Orthogonally positioned impedance patches can be coupled with at least one magnetic sensor including multiple sensor coils, which can be placed within a magnetic field generated by a hybrid positioning system for detecting magnetic distortion or physical movement near a medical device within a patient. The hybrid positioning system utilizes impedance-based and magnetic field-based positioning methods to more accurately determine the position of the medical device. In each corresponding magnetic field distortion sensor, each corresponding sensor coil can receive energy indicating magnetic field strength and orientation. In the case where no change in impedance position is observed, the perceived change in received energy over time indicates magnetic distortion in the magnetic field near the magnetic sensor. Alternatively, while also observing changes in impedance position, the perceived change in received energy over time indicates physical movement of the impedance patch and the magnetic sensor attached thereto.

[0053] An example of such a system is the EnSite Precision TM EnSite Precision TM The mapping system can utilize both impedance-based and magnetic field-based localization methods (e.g., a hybrid system). The impedance measurement patch can be electrically coupled to the patient. TMIn some embodiments of the mapping system, impedance measurement patches can be placed on the patient's chest, either side of the patient's chest, and at least one leg of the patient. Based on the changing impedance values ​​detected by the impedance measurement patches, the impedance-based position of the medical device can be determined.

[0054] In one embodiment, a vector sum of the received energies is calculated to determine a perceived change in the position of the sensor coils relative to each other (and / or a perceived change in the position of the magnetic field distortion sensors relative to each other). The perceived change indicates magnetic distortion in the magnetic field adjacent to the impedance patch and the sensor coils.

[0055] During operation of the magnetic sensors in the magnetic field, the output of each magnetic distortion sensor can be used to calculate the amplitude position and orientation associated with the mechanical position and orientation of the magnetic distortion sensors relative to each other. In a specific embodiment, for example, the vector sum of the distances between the magnetic distortion sensors is calculated. In response to the distortion in the magnetic field, the sensed position of one (or more) magnetic distortion sensors can be displaced from its known / fixed position relative to other magnetic distortion sensors. As a result, the corresponding vector sum is affected accordingly. The change in the vector sum from the initial indicator value, above a determined threshold, indicates the distortion of the magnetic field generated. After determining the initial indicator value (where the magnetic field is not distorted), the subsequent amplitude position and orientation can be correlated in time. Due to local magnetic distortion within the magnetic field, these subsequent amplitude values ​​may be different from the initial indicator value, resulting in erroneous reports of the position and orientation of the magnetic distortion sensors relative to each other (even if the orientation and position of the magnetic distortion sensors relative to each other are fixed). The initial indicator value can be compared with the subsequent indicator value to determine when an acceptable level of magnetic field distortion during a medical procedure is exceeded. The incremental value (the change in value between the initial indicator value and the subsequent indicator value) is associated with the drift associated with the distortion in the catheter positioning.

[0056] In addition, during the operation of the impedance patch, the output of at least one impedance position can be used to calculate the movement of the impedance position. In response to the movement of the impedance patch, the sensed position of one (or more) impedance devices can be changed. As a result, a vector of such position change can be obtained. A vector change above a determined threshold can indicate the physical movement of the patch. In one embodiment, an acceptable vector value (e.g., a soft threshold) for impedance movement can be determined by a clinician and / or an acceptable vector value (e.g., a hard threshold) for impedance movement can be determined by a processor circuit. In another embodiment, an acceptable vector value for impedance movement can be preset in the system. In yet another embodiment, the system can suggest one or more acceptable vector values ​​for impedance movement based on various factors for the clinician to select.

[0057] Figures 6A-6C Motion detection is shown as it may occur in different situations. Fig. 6ADepicted are the motions that occur when magnetic field distortion is present. Fig. 6A It includes impedance patch position 603, first magnetic sensor position 605, second magnetic sensor position 607 and magnetic sensor vector 609. Magnetic field distortion can be detected when the system detects a change in the position of at least one magnetic sensor and does not detect a change in patch impedance. Figure 6B Depicted are the movements that would occur if patient motion were present. Figure 6B Includes a first impedance patch position 621, a second impedance path position 623, a first magnetic sensor position 625, a second magnetic sensor position 627, a magnetic sensor vector 631, and an impedance patch vector 629. When the system detects a change in position of at least one magnetic sensor and also detects a change in impedance, the system can determine that patient or other physical movement of the patch and magnetic sensor has occurred. Figure 6C Includes a first impedance patch position 641, a first magnetic sensor position 643, a first catheter position 645, a first catheter tip electrode position 649, a first catheter ring electrode position 647, a second magnetic sensor position 651, a second catheter position 653, a second catheter tip electrode position 657, a second catheter ring electrode position 655, a magnetic sensor vector 659, and a catheter vector 661. When the system detects a change in the position of at least one magnetic sensor and also detects a change in the catheter vector, the system can determine that patient or other physical movement of the catheter electrodes and magnetic sensors has occurred. Both the impedance patch vector and the catheter vector are affected by changes in impedance readings. These vectors may also be referred to as impedance vectors.

[0058] In one embodiment, the catheter vector may include a vector associated with motion observed in a single electrode. In another embodiment, the catheter vector may include a vector associated with motion of multiple electrodes present on the catheter. In yet another embodiment, the catheter vector may include a vector associated with motion observed from multiple electrodes on multiple catheters. In one embodiment, the catheter may include a reference catheter. The reference catheter may be placed by a physician in an area of ​​the heart that is less likely to fall out during a procedure. In one embodiment, the reference catheter may be placed in the coronary sinus. In other embodiments, the reference catheter may be set in other locations in or around the patient's heart or other organs. In another embodiment, the catheter may include a catheter in the atrium, ventricle, or other part of the heart. In some embodiments, the catheter may include a mapping catheter or an ablation catheter.

[0059] The mapping system can use the above information to determine the type of error present in the system. As described above, if the system records the position change and / or movement of the detection position of the magnetic sensor, but does not record the position change of the impedance system, it is determined that there is magnetic distortion. Alternatively, if the system records the position change and / or movement of the detection position of the magnetic sensor and also records the position change of the impedance system, it is determined that there is physical movement. By determining the amount of distortion and / or movement present in the system, and the type of movement, the system can determine whether there is magnetic distortion or physical movement. As described above, in one embodiment, the system can use a threshold to determine whether the amount of movement sensed by the system is large enough to detect. If magnetic distortion or physical movement is detected, in one embodiment, the system can alert a doctor or physician to the error state. This information can be conveyed to the clinician using auditory, visual, tactile or other sensory feedback. In another embodiment, the system can notify the doctor and the doctor can physically correct the movement. In another embodiment, the system can notify the doctor and the system can correct any offset or movement that occurs within the system through an algorithm.

[0060] A mapping system as described herein can detect motion that occurs in millisecond time lengths. In one embodiment, the mapping system can check for changes in the values ​​of these millisecond time lengths and alert the physician if motion and / or distortion occurs. In other embodiments, the mapping system can look for changes in time lengths from one second to multiple seconds. In addition, the mapping system can detect normal, rhythmic motion, such as a patient's breathing. In some embodiments, the amount of motion of a position during a patient's breathing can be greater than a threshold. In some embodiments, the system can be configured to compensate for such respiratory motion. In one embodiment, the system can use a compensation algorithm to compensate for motion during breathing.

[0061] In other embodiments, the system may ignore periodic motion, such as breathing, and instead examine data for permanent changes. In one embodiment, the system may examine a time period of less than one second for permanent changes. In another embodiment, the system may examine a time period of 1-5 seconds for permanent changes. In yet another embodiment, the system may examine a time period of 1-10 seconds for permanent changes.

[0062] In response, the mapping system may ignore position data from the magnetic field-based portion of the system, or correct for distortion. For example, data from one or more magnetic distortion sensors may be used to determine the difference between the actual position (based on the known / fixed position of the magnetic distortion sensor within the system) and the perceived position (based on the magnetic field received by the magnetic field distortion sensor and the position determined by post-processing). The determined difference may indicate magnetic distortion or physical movement of the entire magnetic field due to the physical movement of an ferrous / metal object entering the magnetic field or the sensor. Based on the difference at each magnetic distortion sensor position, a transformation may be calculated to correct the distortion or movement at all positions within the magnetic field, including the magnetic distortion or movement experienced by a magnetically positioned medical device. In other embodiments, when the system determines that magnetic distortion is affecting the system, the hybrid magnetic and impedance tracking system may automatically change the position sensing of the medical device to rely only on impedance position sensing. In other embodiments, the hybrid magnetic and impedance tracking system may signal the user that magnetic distortion is present, and the user may then select the option to proceed by sensing only the impedance position data of the medical device. In some embodiments, this operation may be referred to as impedance mode. In various embodiments, the impedance position sensing mode may continue until the magnetic distortion no longer affects the system, at which point the system may automatically switch back to using the same magnetic tracking system as before the magnetic distortion was present. In other embodiments, the impedance position sensing mode may continue until the magnetic distortion no longer affects the system, at which point the system may signal the user whether they want to switch back to using the same magnetic tracking system as before the magnetic distortion was present.

[0063] In the embodiments described herein, the magnetic distortion sensor may be generally centered on the portion of the patient's body where the medical device is to be positioned. For example, in cardiac-related surgery, the magnetic distortion sensor may be positioned near the patient's heart to improve detection of magnetic distortion affecting the medical device therein.

[0064] It should be noted that the features shown in the drawings are not necessarily drawn to scale, and features of one embodiment may be used with other embodiments that those skilled in the art will recognize, even if not explicitly stated herein. Descriptions of well-known components and processing techniques may be omitted so as not to unnecessarily obscure the embodiments of the present disclosure. The examples used herein are intended only to facilitate an understanding of the manner in which the present disclosure may be implemented and to further enable those skilled in the art to implement the embodiments of the present disclosure. Therefore, the examples and embodiments herein should not be construed as limiting the scope of the present disclosure.

[0065] As used in this disclosure, the terms "includes," "comprising," and variations thereof mean "including but not limited to," unless expressly stated otherwise.

[0066] The terms "a", "an" and "the" used in this disclosure mean "one or more" unless expressly specified otherwise.

[0067] Although process steps, method steps, algorithms, etc. may be described in order, such processes, methods, and algorithms may be configured to work in alternative orders. In other words, any order or sequence of steps that may be described does not necessarily indicate that the steps need to be performed in that order. The steps of the processes, methods, and algorithms described herein may be performed in any practical order. In addition, some steps may be performed simultaneously.

[0068] When a single device or article is described herein, it will be apparent that more than one device or article may be used in place of the single device or article. Similarly, where more than one device or article is described herein, it will be apparent that a single device or article may be used in place of the more than one device or article. The functionality or features of a device may alternatively be embodied by one or more other devices that are not explicitly described as having such functionality or features.

[0069] Various embodiments of various devices, systems and / or methods are described herein. Many specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture and use of the embodiments described in the specification and shown in the drawings. However, it will be appreciated by those skilled in the art that these embodiments can be practiced without such specific details. In other cases, well-known operations, components and elements are not described in detail to avoid blurring the embodiments described in the specification. It will be appreciated by those of ordinary skill in the art that the embodiments described and illustrated herein are non-limiting examples, and it will therefore be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments, which scope is limited only by the appended claims.

[0070] References throughout this specification to "various embodiments," "some embodiments," "one embodiment," "an embodiment," etc. mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in at least one embodiment. Thus, the phrases "in various embodiments," "in some embodiments," "in one embodiment," "in an embodiment," etc., appearing in various places throughout this specification, do not necessarily all refer to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Thus, particular features, structures, or characteristics shown or described in conjunction with one embodiment may be combined, in whole or in part, with features, structures, or characteristics of one or more other embodiments without limitation, provided that such combination is not illogical or non-functional.

[0071] It should be understood that the terms "proximal" and "distal" may be used throughout the specification with reference to a clinician operating one end of an instrument for treating a patient. The term "proximal" refers to the portion of the instrument closest to the clinician, and the term "distal" refers to the portion farthest from the clinician. It should also be understood that for simplicity and clarity, spatial terms such as "vertical," "horizontal," "upward," and "downward" may be used herein with respect to the illustrated embodiments. However, surgical instruments may be used in many orientations and positions, and these terms are not intended to be limiting and absolute.

Claims

1. A system for distinguishing magnetic field distortion from physical motion in a hybrid magnetic and impedance tracking system for navigating a medical device within a patient, the system comprising: an impedance localization system, comprising a first driven patch and a second driven patch configured to be coupled to an external surface of a patient's body, the first driven patch and the second driven patch configured to generate an electric field in the body for localizing an electrode on the medical device; a magnetic positioning system configured to generate a magnetic field; a magnetic sensor coupled to one of the first drive patch and the second drive patch and configured to receive a signal from the magnetic positioning system; as well as An electronic control unit is configured to receive drive patch position data from the impedance positioning system and magnetic sensor position data from the magnetic positioning system, wherein the electronic control circuit is configured to detect a position change of the magnetic sensor and use the drive patch position data and the magnetic sensor position data to determine whether the detected position change of the magnetic sensor is caused by magnetic field distortion or physical movement of the magnetic sensor.

2. The system according to claim 1, wherein: The magnetic sensor also includes an output reference signal that establishes an origin of a coordinate system.

3. The system according to claim 1, wherein: The magnetic sensor includes a plurality of sensor coils positioned at fixed distances and orientations relative to each other, each of the sensor coils being configured and arranged to sense a magnetic field coplanar with the orientation of the sensor coil and output an electrical signal indicative of the sensed magnetic field.

4. The system according to claim 1, wherein: The electronic control unit determines a first magnetic sensor position, a second magnetic sensor position, and a magnetic field distortion sensor vector when determining whether magnetic field distortion or physical movement of the magnetic sensor has occurred.

5. The system according to claim 1, wherein: The electronic control unit determines an impedance vector when determining whether magnetic field distortion or physical movement of the magnetic sensor has occurred.

6. The system according to claim 1, wherein: The electronic control unit determines an original magnetic sensor position, a measured magnetic sensor position, an original driver patch position, and a measured driver patch position when determining whether magnetic field distortion has occurred.

7. The system according to claim 1, wherein: The electronic control unit determines a raw magnetic sensor position, a measured sensor position, a raw drive patch position, and a measured drive patch position when determining whether physical movement of the magnetic sensor has occurred.

8. The system according to claim 1, wherein: The magnetic sensor includes a first magnetic sensor, and wherein the system further includes a third driven patch and a second magnetic sensor coupled to the third driven patch.

9. The system according to claim 1, wherein: The impedance localization system is configured to determine a measured position of the medical device, and wherein the electronic control unit is configured to correct the measured position of the medical device due to distortion of the magnetic field or physical movement of the magnetic sensor.

10. The system according to claim 1, wherein: The electronic control unit is configured to output the position of the electrodes on the medical device when magnetic field distortion is detected while ignoring information from the magnetic positioning system.

11. A system for distinguishing magnetic field distortion from physical motion in a hybrid magnetic and impedance tracking system for navigating a medical device within a patient, the system comprising: a magnetic positioning system configured to generate a magnetic field; a magnetic sensor comprising a first sensor coil, a second sensor coil oriented orthogonally to the first sensor coil, and a third sensor coil oriented orthogonally to the first sensor coil and the second sensor coil and configured to receive a signal from the magnetic positioning system; a plurality of impedance patches configured to generate an electric field within a patient's body for positioning electrodes on a medical device; as well as An electronic control unit configured to receive information from the magnetic sensor and the plurality of impedance patches, wherein the electronic control unit is configured to determine a magnetic sensor vector and an impedance vector, wherein the electronic control circuit is configured to detect a position change of the magnetic sensor and use the magnetic sensor vector and the impedance vector to determine whether the detected position change is caused by magnetic field distortion or by physical movement of the magnetic sensor, and wherein the electronic control unit is configured to initiate a correction algorithm, wherein the correction algorithm is configured to correct the position change of the medical device based on the magnetic field distortion or by physical movement of the magnetic sensor.

12. The system according to claim 11, wherein: The first, second and third sensor coils are configured and arranged to receive energy indicative of magnetic field strength and magnetic field orientation substantially coaxially with the receiving sensor coil.

13. The system according to claim 11, wherein: The magnetic sensor is coupled to one of the plurality of impedance patches.

14. The system according to claim 11, wherein: The electronic control unit is configured to issue a notification when a threshold of magnetic field distortion or physical movement of the magnetic sensor has occurred.

15. A method for distinguishing between magnetic field distortion and physical motion in a hybrid magnetic and impedance tracking system for navigating a medical device within a patient, the method comprising: receiving, at a first time, from a magnetic sensor a first set of one or more signals indicative of a magnetic field sensed by each of a plurality of sensor coils within the magnetic sensor; receiving a first set of one or more signals from an impedance sensor indicative of a position within a coordinate system; receiving, at a second time, from the magnetic sensor a second set of one or more signals indicative of a magnetic field sensed by each sensor coil; receiving a second set of one or more signals from the impedance sensor indicative of a position within the coordinate system; determining a magnetic sensor vector; determining an impedance vector; detecting a position change of the magnetic sensor; comparing the magnetic sensor vector to a first threshold and comparing the impedance vector to a second threshold to determine whether a detected change in position of the magnetic sensor is caused by magnetic field distortion or because physical movement of the magnetic sensor has occurred; wherein if the magnetic sensor vector exceeds the first threshold and the impedance vector is below the second threshold, the detected position change is caused by magnetic field distortion; and Wherein, if the magnetic sensor vector exceeds the first threshold and the impedance vector exceeds the second threshold, the detected position change is caused by physical movement of the magnetic sensor.

16. The method of claim 15, further comprising notifying a physician when magnetic field distortion or physical movement of the magnetic sensor has occurred.

17. The method according to claim 15, wherein: The impedance sensor includes a patch.

18. The method according to claim 15, wherein: The magnetic sensor is coupled to the impedance sensor.

19. The method according to claim 15, wherein: The impedance sensor includes electrodes on a medical device.

20. The method of claim 19, further comprising running a correction algorithm, wherein the correction algorithm is configured to correct for changes in position of the medical device based on the magnetic field distortion or through physical movement of the magnetic sensor.

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