Accurate Basket Catheter Tracking

Abstract

The present invention is titled "Accurate Basket Catheter Tracking". In one embodiment, a system includes: a catheter that includes an insertion tube and a first orientation sensor; a pusher that includes a second orientation sensor; and an inflatable assembly that includes a flexible strip circumferentially disposed around a distal portion of the pusher, wherein a first end of the strip is connected to a distal end of the insertion tube and a second end of the strip is connected to the distal portion of the pusher, and the flexible strip bends radially outward when the pusher retracts; a processing circuit configured to: receive respective orientation signals from the first orientation sensor and the second orientation sensor; calculate position and orientation coordinates of the orientation sensors, which are constrained to be coaxial and have the same orientation; calculate a distance between the calculated position coordinates of the orientation sensors; and find orientation coordinates of the flexible strip in response to at least the calculated distance.

Description

Technical Field

[0001] The present invention relates to medical devices and, more particularly, to tracking the orientation of a catheter. Background Art

[0002] A number of medical procedures involve placing a probe, such as a catheter, within a patient. Position sensing systems have been developed to track such probes. Magnetic position sensing is one method known in the art. In magnetic position sensing, a magnetic field generator is typically placed at a known location outside of the patient. A magnetic field sensor within the distal end of the probe generates an electrical signal in response to these magnetic fields, and the electrical signal is processed to determine the coordinate position of the distal end of the probe. These methods and systems are described in U.S. Pat. Nos. 5,391,199, 6,625,563, 6,690,963, 6,484,118, 6,239,724, 6,618,612, and 6,332,089, in PCT International Publication WO 1996 / 005768, and in U.S. Patent Application Publications 2003 / 0120150 and 2004 / 0068178, the disclosures of which are incorporated herein by reference in their entirety. Position can also be tracked using impedance or current-based systems.

[0003] European Patent Publication 3,178,384 to Hoitink et al. describes a catheter having a dual-node multi-ray electrode assembly at the distal end of the catheter body. The dual-node multi-ray electrode assembly includes a proximal multi-ray array and a distal node. The proximal multi-ray array has a plurality of ridges connected at one end, and each ridge has at least one ablation electrode. The dual-node multi-ray electrode assembly can have an expanded configuration and a collapsed configuration, in which the ridges are generally arranged along the longitudinal axis of the catheter body. The distal node can be configured to be deployed within a blood vessel, and the proximal multi-ray array can be configured to engage tissue forming a blood vessel ostium with the ablation electrodes. In some embodiments, the relative distance between the proximal multi-ray array and the distal node is adjustable.

[0004] U.S. Patent Publication 2017 / 0181706 to Montag et al. describes using a frame formed by a plurality of conductive wire loops for cardiac catheterization. The wire loops are modeled as polygons, and each polygon is subdivided into a plurality of triangles. The wire loops are exposed to magnetic flux at corresponding frequencies, and signals are read from the loops. The theoretical magnetic flux in a polygon is calculated as the sum of the theoretical magnetic fluxes in its triangles. The positioning and orientation of the frame within the heart are determined by correlating the calculated theoretical magnetic flux with the signals.

[0005] U.S. Patent Publication 2015 / 0025365 by Esguerra et al. describes a catheter with a uniaxial sensor that is mounted directly along a portion of the catheter whose orientation / position is of interest. The magnet-based uniaxial sensor is on a linear or non-linear single-axis sensor (SAS) assembly. The catheter includes a catheter body and a distal 2D or 3D configuration provided by a support member, and at least one (if not at least three) uniaxial sensors are mounted serially along the length of the support member. The magnet-based sensor assembly can include at least one coil member wound around the support member, where the coil member is connected to a corresponding cable member via a junction area, and the cable member is adapted to transmit signals providing position information from the coil member to a mapping and positioning system. The junction area provides strain relief adaptation for at least one coil member and the corresponding cable member to prevent separation.

[0006] U.S. Patent Publication 2015 / 0150472 by Harlev et al. describes a non-contact cardiac mapping method that includes: (i) inserting a catheter into a heart chamber having an endocardial surface, the catheter including a plurality of spatially distributed electrodes; (ii) measuring signals at the catheter electrodes in response to electrical activity in the heart chamber, where the catheter is spaced apart from the endocardial surface; and (iii) determining physiological information at a plurality of positions on the endocardial surface based on the measured signals and the orientation of the electrodes relative to the endocardial surface.

[0007] U.S. Patent Publication 2006 / 0009689 by Fuimaono et al. describes an improved basket catheter that is particularly useful for mapping the heart. The catheter includes an elongated catheter body having a proximal end and a distal end and at least one lumen therethrough. A basket electrode assembly is mounted at the distal end of the catheter body. The basket assembly has a proximal end and a distal end and includes a plurality of ridges connected at its proximal and distal ends. Each ridge includes at least one electrode. The basket assembly has an expanded configuration in which the ridges bend radially outward; and a collapsed configuration in which the ridges are disposed generally along the axis of the catheter body. The catheter also includes a distal position sensor mounted at or near the distal end of the basket electrode assembly, and a proximal position sensor mounted at or near the proximal end of the basket electrode assembly. In use, the coordinates of the distal position sensor relative to the coordinates of the proximal sensor can be determined while obtaining known information about the curvature of the ridges of the basket mapping assembly in order to find the position of at least one electrode of each ridge.

[0008] U.S. Patent Publication 2002 / 0198676 by Kirsch et al. describes a system for determining the orientation, alignment, and system gain factor of a probe. The system includes a plurality of magnetic field sources and at least one magnetic field sensor such that the combination of the magnetic field sensor and the magnetic field sources produces unique measured magnetic field values. The system includes a probe whose gain, orientation, and alignment affect these unique measured magnetic field values. A processor is configured to receive and iteratively process these unique measured magnetic field values to determine a system gain factor indicative of the gain of the probe and a plurality of position factors indicative of the orientation and alignment of the probe. The number of unique measured magnetic field values produced must be at least equal to the sum of the number of calculated gain and position factors.

[0009] The Background section of Kirsch et al. mentions that determining the position and orientation of a probe from magnetic field measurements is not straightforward because the measured magnetic field is a non-linear function of position and orientation. To determine the position and orientation of the probe from the measured magnetic field values, the position and orientation of the probe are first assumed or "guessed" to be at a predicted position and orientation. An iterative process is used to compare the value of the magnetic field at the guessed position and orientation of the probe with the measured field values. If the magnetic field value at the guessed position and orientation is close to the measured value, it is assumed that the guessed position and orientation accurately represent the actual position and orientation of the probe. The iterative process uses a physical model of the probe environment. The physical model specifies the position and orientation of each field source. From the specified position and orientation, the laws of electrodynamics determine the field values. Summary of the Invention

[0010] According to an embodiment of the present disclosure, a system is provided that includes a catheter configured to be inserted into a body part of a living subject and includes an insertion tube, a pusher, and an expandable assembly. The insertion tube includes a distal end and a first coil-based orientation sensor disposed at the distal end. The pusher includes a second coil-based orientation sensor disposed thereon and a distal portion and is configured to be advanced and retracted through the insertion tube. The expandable assembly includes a plurality of flexible strips circumferentially disposed around the distal portion of the pusher, wherein a first end of the strip is connected to the distal end of the insertion tube and a second end of the strip is connected to the distal portion of the pusher. The flexible strip is configured to bend radially outward when the pusher is retracted; at least one magnetic field radiator configured to transmit an alternating magnetic field into the region where the body part is located. The first orientation sensor and the second orientation sensor are configured to output corresponding first and second orientation signals in response to the transmitted alternating magnetic field; and a processing circuit configured to receive the first and second orientation signals from the first and second orientation sensors, use orientation calculations to calculate the position and orientation coordinates of the first and second orientation sensors, wherein the position and orientation coordinates of each of the orientation sensors are calculated iteratively and interdependently in response to the corresponding received orientation signals and are subject to the constraint that the first and second orientation sensors are coaxial, calculate the distance between the calculated position coordinates of the first orientation sensor and the calculated position coordinates of the second orientation sensor, and estimate the corresponding orientation of the flexible strip in response to at least the calculated distance.

[0011] Further according to an embodiment of the present disclosure, the system includes a display, wherein the processing circuit is configured to calculate the volume of the expandable assembly in response to an orientation signal from at least one of the first orientation sensor or the second orientation sensor and present a representation of at least a portion of the catheter and the body part to the display in response to the estimated corresponding orientation of the flexible strip.

[0012] Still further according to an embodiment of the present disclosure, the processing circuit is configured to use orientation calculations to calculate the position and orientation coordinates of one of the first and second orientation sensors and calculate the position coordinates of the other of the first and second orientation sensors, which is subject to the constraint that the calculated orientation coordinates of the other sensor will be equal to the calculated orientation coordinates of one sensor within a given tolerance.

[0013] Additionally, according to an embodiment of the present disclosure, the processing circuit is configured to calculate the initial position and initial orientation coordinates of the first orientation sensor and the second orientation sensor using orientation calculations, calculate the average of the initial orientation coordinates of the first orientation sensor and the second orientation sensor, and calculate the position and orientation coordinates of the first orientation sensor and the second orientation sensor using orientation calculations, which is constrained by the orientation coordinates of the first orientation sensor and the second orientation sensor being equal to the calculated average of the initial orientation coordinates with a given tolerance.

[0014] Furthermore, according to an embodiment of the present disclosure, the processing circuit is configured to calculate the position and orientation coordinates of the first orientation sensor and the second orientation sensor, which is constrained by the calculated orientation coordinates of the first orientation sensor and the second orientation sensor being equal within a given tolerance.

[0015] According to another embodiment of the present disclosure, a system is also provided, which includes: a catheter configured to be inserted into a body part of a living subject and including an insertion tube, a pusher, and an inflatable assembly. The insertion tube includes a distal end and a first coil-based orientation sensor disposed at the distal end. The pusher includes a second coil-based orientation sensor disposed thereon and a distal portion and is configured to be advanced and retracted through the insertion tube. The inflatable assembly includes a plurality of flexible strips circumferentially disposed around the distal portion of the pusher, wherein a first end of the strip is connected to the distal end of the insertion tube, and a second end of the strip is connected to the distal portion of the pusher. The flexible strip is configured to bend radially outward when the pusher is retracted; at least one magnetic field radiator configured to transmit an alternating magnetic field into the region where the body part is located. The first orientation sensor and the second orientation sensor are configured to output corresponding first orientation signals and second orientation signals in response to the transmitted alternating magnetic field; and a processing circuit configured to receive the first orientation signal and the second orientation signal from the first orientation sensor and the second orientation sensor, calculate the distance and relative orientation angle between the first orientation sensor and the second orientation sensor in response to the received orientation signals, and estimate the corresponding orientation of the flexible strip in response to at least the calculated distance and relative orientation angle, taking into account the distortion of one or more of the flexible strips from a symmetric arrangement when the value of the relative orientation angle is greater than zero.

[0016] Further according to an embodiment of the present disclosure, the system includes a display, wherein the processing circuit is configured to calculate the volume of the inflatable assembly in response to an orientation signal from at least one of the first orientation sensor or the second orientation sensor, and present a representation of at least a portion of the catheter and the body part to the display in response to the estimated corresponding orientation of the flexible strip.

[0017] According to yet another embodiment of the present disclosure, there is also provided a method that includes: inserting a catheter into a body part of a living subject, the catheter including an insertion tube, a first coil-based orientation sensor disposed at a distal end of the insertion tube, a pusher including a second coil-based orientation sensor disposed thereon, an inflatable assembly including a flexible strip circumferentially disposed around a distal portion of the pusher, wherein a first end of the strip is connected to the distal end of the insertion tube and a second end of the strip is connected to the distal portion of the pusher; retracting the pusher such that the flexible strip bends radially outward; transmitting an alternating magnetic field into the region where the body part is located; outputting respective first and second orientation signals by the first and second orientation sensors in response to the transmitted alternating magnetic field; receiving the first and second orientation signals from the first and second orientation sensors; using orientation calculations to calculate position and orientation coordinates of the first and second orientation sensors, wherein the position and orientation coordinates of each of the orientation sensors are calculated iteratively and interdependently in response to the respective received orientation signals and are subject to the constraint that the first and second orientation sensors are coaxial; calculating a distance between the calculated position coordinates of the first orientation sensor and the calculated position coordinates of the second orientation sensor; and estimating a respective orientation of the flexible strip in response to at least the calculated distance.

[0018] Further according to an embodiment of the present disclosure, the method includes calculating a volume of the inflatable assembly in response to an orientation signal from at least one of the first orientation sensor or the second orientation sensor, and presenting a representation of at least a portion of the catheter and the body part to a display in response to the estimated respective orientation of the flexible strip.

[0019] Additionally, according to an embodiment of the present disclosure, the method includes using orientation calculations to calculate position and orientation coordinates of one of the first and second orientation sensors, and calculating position coordinates of the other of the first and second orientation sensors, which is subject to the constraint that the calculated orientation coordinates of the other sensor will be equal to the calculated orientation coordinates of the one sensor within a given tolerance.

[0020] Furthermore, according to an embodiment of the present disclosure, the method includes using orientation calculations to calculate initial position and initial orientation coordinates of the first and second orientation sensors, calculating an average of the initial orientation coordinates of the first and second orientation sensors, and using orientation calculations to calculate position and orientation coordinates of the first and second orientation sensors, which is subject to the constraint that the orientation coordinates of the first and second orientation sensors will be equal to the calculated average of the initial orientation coordinates within a given tolerance.

[0021] Further in accordance with an embodiment of the present disclosure, the method includes calculating the position and orientation coordinates of a first orientation sensor and a second orientation sensor, subject to the constraint that the calculated orientation coordinates of the first orientation sensor and the second orientation sensor will be equal within a given tolerance.

[0022] In accordance with yet another embodiment of the present disclosure, there is also provided a method that includes inserting a catheter into a body part of a living subject, the catheter including an insertion tube, a first coil-based orientation sensor disposed at a distal end of the insertion tube, a pusher including a second coil-based orientation sensor disposed thereon, an inflatable assembly including a flexible strip circumferentially disposed around a distal portion of the pusher, wherein a first end of the strip is connected to the distal end of the insertion tube and a second end of the strip is connected to the distal portion of the pusher; retracting the pusher such that the flexible strip bends radially outward; transmitting an alternating magnetic field into the region where the body part is located; outputting corresponding first and second orientation signals by the first orientation sensor and the second orientation sensor in response to the transmitted alternating magnetic field; receiving the first and second orientation signals from the first orientation sensor and the second orientation sensor; calculating the distance and relative orientation angle between the first orientation sensor and the second orientation sensor in response to the received orientation signals; and estimating the corresponding orientation of the flexible strip in response to at least the calculated distance and relative orientation angle, taking into account the twist of one or more of the flexible strips from a symmetric arrangement when the value of the relative orientation angle is greater than zero.

[0023] Even further in accordance with an embodiment of the present disclosure, the method includes calculating the volume of the inflatable assembly in response to an orientation signal from at least one of the first orientation sensor or the second orientation sensor, and presenting a representation of at least a portion of the catheter and the body part to a display in response to the estimated corresponding orientation of the flexible strip. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be understood from the following detailed description in conjunction with the accompanying drawings, in which:

[0025] Figure 1 is a schematic illustration of a system for electroanatomical mapping in accordance with an embodiment of the present invention, the system including a catheter;

[0026] Figure 2A is a schematic view of the distal end of a basket catheter in a collapsed form;

[0027] Figure 2B is in a deployed form Figure 2A of the distal end of a basket catheter;

[0028] Figure 3A includes the use of Figure 2A and Figure 2Bof the basket catheter Figure 1 Flowchart of steps in the method of operating the system;

[0029] Figure 3B For including Figure 3A Flowchart of sub - steps in the method of operation;

[0030] Figure 3C For including Figure 3A Flowchart of alternative sub - steps in the method of operation;

[0031] Figure 4A Schematic view of the distal end of the basket catheter;

[0032] Figure 4B For Figure 4A Schematic view of the distal end of the basket catheter after deformation to the side; and

[0033] Figure 5 For including the use of Figure 4A and Figure 4B of the basket catheter Figure 1 Flowchart of steps in the method of operating the system. Detailed Description

[0034] Overview

[0035] 3 The system (manufactured by Biosense Webster, Inc., Irvine, California) applies advanced catheter location (ACL) hybrid - orientation tracking technology. In ACL technology, the distribution of the measured current associated with the probe electrodes on the catheter is correlated with a current - position matrix (CPM) that maps the current distribution to the position of the catheter previously acquired from magnetically position - calibrated orientation signals. The ACL technology allows the catheter (even a catheter without a magnetic field sensor) to be located and visualized only in the volume in which the CPM has been calculated using a catheter equipped with a magnetic sensor. A prerequisite for constructing the CPM is to insert a catheter equipped with a magnetic field sensor into the body and move the catheter within the volume of the body to calculate the CPM for that volume.

[0036] The ACL technology can be used to track a basket catheter that has electrodes on the basket. However, in some cases, the ACL technology for measuring current or impedance may not provide a high enough accuracy.

[0037] Embodiments of the present invention use magnetic-based tracking technology to calculate the orientation coordinates of a basket catheter based on two coil-based orientation sensors to provide an accurate calculation of the orientation of the basket and its electrodes. At least one magnetic field radiator transmits an alternating magnetic field into the region where the body part is located, and the coil-based orientation sensors output corresponding orientation signals in response to the transmitted alternating magnetic field, such that the corresponding orientation signals read from the coils provide information about the orientation of the coils.

[0038] In some embodiments, the catheter includes an insertion tube that includes a lumen and a first coil-based orientation sensor disposed at the distal end of the insertion tube. The catheter also includes a pusher that includes a second coil-based orientation sensor disposed thereon. The pusher is advanced and retracted through the lumen, as will be explained in more detail below. The orientation sensors can be selected from single-axis, biaxial, or triaxial sensors, as described with reference to the disclosed embodiments.

[0039] The catheter also includes an expandable assembly (e.g., a basket assembly) that includes a flexible strip circumferentially disposed around the distal portion of the pusher, wherein a first end of the strip is connected to the distal end of the insertion tube and a second end of the strip is connected to the distal end of the pusher. The flexible strip bends radially outward when the pusher is retracted and flattens when the pusher is pushed in the direction of the distal end of the catheter. Each flexible strip of the flexible strip includes a plurality of electrodes disposed thereon.

[0040] Although the strip is flexible, the strip is rigid enough such that the calculated inter-coil distance between the first coil-based orientation sensor and the second coil-based orientation sensor should provide an accurate estimate of the shape of the flexible strip. However, the difference between the inter-coil distances can be about 4 mm for some baskets and about 10 mm for other baskets when the basket is fully deployed and when the basket is fully closed, depending on the size of the basket. Additionally, the resolution of the magnetic-based tracking technology can be about 1 mm. Thus, the inter-coil distance calculated using the magnetic-based tracking technology may not be accurate enough to accurately predict the shape of the flexible strip.

[0041] Some embodiments use a novel orientation calculation to more accurately calculate the inter-coil distance based on the assumption that the first coil-based orientation sensor and the second coil-based orientation sensor are coaxial. In other words, one of the sensors includes a coil that is coaxial with the coil of the other sensor and with the axis of the insertion tube of the catheter. By way of example only, the novel orientation calculation can improve the accuracy of the orientation measurement from about 1 mm to about 0.1 mm.

[0042] The system includes processing circuitry that receives respective orientation signals from a first orientation sensor and a second orientation sensor. The processing circuitry uses orientation calculations to calculate position and orientation coordinates of the first orientation sensor and the second orientation sensor, where the position and orientation coordinates of each of the orientation sensors are calculated iteratively and dependently on each other in response to the respective orientation signals. The orientation calculations are interdependent such that the position coordinates calculated for one of the sensors based on the signals received from the sensors depend on the orientation coordinates calculated for that sensor, and vice versa. Similarly, an error in calculating the position coordinates (e.g., due to noise or any other factor) results in inaccurate calculation of the orientation, and vice versa.

[0043] Any suitable iterative orientation calculation may be used. For example, U.S. Patent Publication 2002 / 0198676 to Kirsch et al. (which is incorporated herein by reference) describes iterative orientation calculations in its background section and some improvements in its detailed description. The background section of Kirsch et al. mentions that determining the position and orientation of a probe from magnetic field measurements is not straightforward because the measured magnetic field is a non-linear function of position and orientation. To determine the position and orientation of the probe based on the measured magnetic field values, the position and orientation of the probe are first assumed or "guessed" to be at a predicted position and orientation. An iterative process is used to compare the value of the magnetic field at the guessed position and orientation of the probe with the measured field value. If the magnetic field value at the guessed position and orientation is close to the measured value, it is assumed that the guessed position and orientation accurately represent the actual position and orientation of the probe. The orientation calculations described in the publication of Kirsch et al. may provide a suitable iterative orientation calculation, with necessary modifications, for the embodiments of the present disclosure. For example, the iterative orientation calculations described by Kirsch et al. may be subject to constraints with respect to orientation, as described below.

[0044] European Patent Publication 1,126,787 to Golden et al. (which is incorporated herein by reference) describes iterative orientation calculations, which may provide a suitable iterative orientation calculation, with necessary modifications, for the embodiments of the present disclosure.

[0045] Based on the interdependent and iterative nature of the calculations, an improvement in the accuracy of position measurement may be achieved by constraining the orientation calculations based on the known geometry of the catheter such that the first orientation sensor and the second orientation sensor are coaxial, and thus the two sensors have the same orientation used in the orientation calculations of the two sensors.

[0046] In some embodiments, the processing circuitry calculates the position and orientation coordinates of the first orientation sensor and the second orientation sensor, subject to the constraint that the calculated orientation coordinates of the first orientation sensor and the second orientation sensor will be equal within a given tolerance. Forcing the orientation coordinates to be approximately equal generally results in more accurately calculated position coordinates.

[0047] In other embodiments, the processing circuitry uses orientation calculations to calculate the position and orientation coordinates of one of the sensors (Sensor A) in the sensor, and then calculates the position coordinates of the other sensor (Sensor B), subject to the constraint that the calculated orientation coordinates of Sensor B will be equal to the already calculated orientation coordinates of Sensor A within a given tolerance (such as plus or minus 2 degrees).

[0048] In still other embodiments, the processing circuitry uses orientation calculations based on signals received from the sensors to calculate the initial position and initial orientation coordinates of the two sensors, and then calculates the average of the initial orientation coordinates of the two sensors. The processing circuitry then uses orientation calculations based on signals received from the respective sensors to calculate the position and orientation coordinates of each sensor, and is subject to the constraint that the finally calculated orientation coordinates of each sensor will be equal to the calculated average of the initial orientation coordinates within a given tolerance (such as plus or minus 2 degrees).

[0049] The calculated position coordinates of the first sensor and the second sensor can be used to calculate the distance between the first orientation sensor and the second orientation sensor.

[0050] Based on knowledge of the mechanical characteristics of the flexible strip and / or by performing pre-calibration to find which coil-to-coil distances correspond to which bends of the flexible strip (at various distances between the sensors), the corresponding orientation of the flexible strip can be estimated in response to the calculated distance and the roll of the basket, the roll of which can be calculated from the signals of the biaxial or triaxial orientation sensors provided on the catheter. The processing circuitry presents a representation of at least a portion of the catheter and the body part to the display in response to the estimated corresponding orientation of the flexible strip and the calculated roll.

[0051] In some embodiments, improved distance measurements can be provided by one of the sensors acting as a local transmitter and the other sensor acting as a local receiver. The transmitter can then transmit a signal to the receiver at a frequency different from the frequency used by the magnetic field radiator described above. The locally transmitted and received signals can provide additional information about the positions of the two sensors (such as the distance between the sensors based on the strength of the received signal), and this can be used to increase the accuracy of basket visualization.

[0052] In some embodiments, where the pusher and the basket are flexible enough to be pushed to one side relative to the axis of the insertion tube (e.g., when pressing against tissue in a body part), the processing circuit may calculate the distance and the relative orientation angle between the first orientation sensor and the second orientation sensor in response to the received orientation signals. Then, a non-zero relative orientation angle indicates that the expandable assembly (e.g., the basket) is deflected to one side relative to the axis of the insertion tube, and when the expandable assembly is centered about the axis of the insertion tube, at least some of the flexible strips in the flexible strip are distorted compared to the shape of the flexible strip. Based on the knowledge of the mechanical properties of the flexible strip and / or by performing pre-calibration to find which relative orientation angle corresponds to which deformation of the flexible strip (at the distance between the sensors), the respective orientation of the flexible strip (including the distorted flexible strip) can be estimated in response to at least the calculated distance and relative orientation angle, taking into account the distortion of one or more flexible strips in the flexible strip from a symmetric arrangement when the value of the relative orientation angle is greater than zero.

[0053] System Description

[0054] Documents incorporated herein by reference are to be considered an integral part of this application, except that, to the extent any term is defined in these incorporated documents in a manner that conflicts with the definition explicitly or implicitly made in this specification, only the definition in this specification shall be considered. As used herein, the term “about” or “approximately” with respect to any numerical value or range indicates a suitable dimensional tolerance that allows the collection of components or elements to achieve its intended purpose as described herein. More specifically, “about” or “approximately” can refer to a range of values of ±20% of the recited value, e.g., “about 90%” can refer to a range of values from 71% to 99%.

[0055] Now refer to Figure 1 , which is a schematic illustration of a catheter tracking system 20 according to an embodiment of the present invention. The system 20 includes a catheter 40 configured to be inserted into a body part of a living subject (e.g., patient 28). A physician 30 navigates the basket catheter 40 (e.g., a basket catheter manufactured by Biosense Webster, Inc. of Irvine, CA, USA), shown in detail in illustration 45, to a target location in the heart 26 of the patient 28 by manipulating the deflectable section of the insertion tube 22 of the catheter 40 and / or deflecting from the sheath 23 using a manipulator 32 near the proximal end 29 of the insertion tube 22. In the illustrated embodiment, the physician 30 uses the catheter 40 to perform electroanatomical mapping of the heart chamber.

[0056] The insertion tube 22 includes a distal end 33. The catheter 40 includes a component 35 (e.g., a basket component), and a plurality of electrodes 48 (only some are labeled for simplicity) are disposed on the component. The component 35 is disposed distally of the insertion tube 22 and can be connected to the insertion tube 22 via a coupling member of the insertion tube 22 at the distal end 33. The coupling member of the insertion tube 22 can be formed as an integral part of the remainder of the insertion tube 22 or as a separate element connected to the remainder of the insertion tube 22.

[0057] The component 35 further includes a plurality of flexible strips 55 (only one is labeled for simplicity), and the electrodes 48 are coupled to each flexible strip. The component 35 can include any suitable number of electrodes 48. In some embodiments, the component 35 can include ten flexible strips 55 and 120 electrodes, with 12 electrodes disposed on each flexible strip 55.

[0058] The catheter 40 includes a pusher 37. The pusher 37 is generally a tube disposed in the lumen of the insertion tube 22 and spanning from the proximal end 29 to the distal end 33 of the insertion tube 22. The distal end of the pusher 37 is generally connected to the first end of the flexible strip 55 via a coupling member of the pusher 37. The coupling member of the pusher 37 can be formed as an integral part of the remainder of the pusher 37 or as a separate element connected to the remainder of the pusher 37. The distal end of the insertion tube 22 is generally connected to the second end of the flexible strip 55 via a coupling member of the distal end 33. The pusher 37 is generally controlled via a manipulator 32 to deploy the component 35 and change the ellipticity of the component 35 according to the longitudinal displacement of the pusher 37 relative to the insertion tube 22.

[0059] The actual structure of the basket component 35 can vary. For example, the flexible strip 55 can be made of a printed circuit board (PCB) or a shape memory alloy.

[0060] By way of example only, the embodiments described herein mainly relate to the basket distal end component 35. In alternative embodiments, the disclosed techniques can be used with catheters having balloon-based distal end components or any other suitable type of distal end component.

[0061] The catheter 40 is inserted through the sheath 23 in a folded configuration, and the catheter 40 only resumes its intended functional shape after the catheter 40 exits the sheath 23. By including the catheter 40 in a folded configuration, the sheath 23 also serves to minimize vascular trauma along its path to the target location.

[0062] The catheter 40 incorporates a magnetic sensor 50A at the distal edge of the insertion tube 22 (i.e., at the proximal edge of the basket assembly 35) (see illustration 45). Generally, although not necessarily, the sensor 50A is a single-axis sensor (SAS). A second magnetic sensor 50B can be included at any suitable orientation on the pusher 37. By way of example only, the sensor 50B can be a triaxial sensor (TAS) or a biaxial sensor (DAS) or an SAS, based on, for example, size considerations.

[0063] The magnetic sensors 50A and 50B, and the electrodes 48, are connected via wires passing through the insertion tube 22 to various drive circuits in the console 24.

[0064] In some embodiments, the system 20 includes a magnetic sensing subsystem to estimate the ellipticity of the basket assembly 35 of the catheter 40 and its elongation / retraction state within the heart chamber of the heart 26 by estimating the elongation of the basket assembly 35 from the distance between the sensors 50A and 50B. The patient 28 is placed in a magnetic field generated by a pad incorporating one or more magnetic field generator coils 42, which are driven by the unit 43. The magnetic field generated by the coils 42 transmits an alternating magnetic field into the region where the body part is located. The transmitted alternating magnetic field generates signals in the sensors 50A and 50B, which indicate the orientation and / or direction. The generated signals are transmitted to the console 24 and become corresponding electrical inputs to the processing circuit 41. The processing circuit 41 uses the signals to calculate the elongation of the basket assembly 35 and estimates the basket ellipticity and the elongation / retraction state based on the calculated distance between the sensors 50A and 50B, which is described in more detail below with reference to FIGS. 2 - Figure 5 described in more detail.

[0065] The method of sensing the orientation and / or direction using an external magnetic field and magnetic sensors such as 50A and 50B is implemented in various medical applications, for example, in systems manufactured by Biosense-Webster, and is described in detail in U.S. Patents 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612 and 6,332,089, PCT Patent Publication WO96 / 05768, and U.S. Patent Application Publications 2002 / 0065455A1, 2003 / 0120150A1 and 2004 / 0068178A1, the disclosures of which are incorporated herein by reference.

[0066] The processing circuit 41 (usually part of a general-purpose computer) is further connected via a suitable front-end and interface circuit 44 to receive signals from the surface electrodes 49. The processing circuit 41 is connected to the surface electrodes 49 via wires extending through the cable 39 to the chest of the patient 28.

[0067] The catheter 40 includes a connector 47 disposed at the proximal end 29 of the insertion tube 22 for connection to the processing circuit 41.

[0068] In one embodiment, in response to the calculated orientation coordinates of the insertion tube 22 and the flexible strip 55, the processing circuit 41 presents a representation 31 of at least a portion of the catheter 40 and the body part to the display 27 based on a scan (e.g., CT or MRI) of the body part previously registered with the system 20, which is described in more detail with reference to FIGS. 2 - Figure 5 described in more detail.

[0069] The processing circuit 41 is typically programmed in software in a general - purpose microprocessor to convert the general - purpose microprocessor into a specific processor and perform the functions described herein. The software can be downloaded electronically over a network to a computer, for example, or alternatively or additionally it can be set and / or stored on a non - transitory tangible medium (such as magnetic memory, optical memory, or electronic memory).

[0070] Figure 1 The exemplary illustrations shown are chosen solely for clarity of concept. For simplicity and clarity, Figure 1 only the elements related to the technology disclosed in the present invention are shown. The system 20 generally includes additional modules and elements that are not directly related to the technology disclosed in the present invention, and thus the additional modules and elements are intentionally omitted from Figure 1 and the corresponding description. The elements of the system 20 and the methods described herein can be further applied, for example, to controlling the ablation of tissue of the heart 26.

[0071] Now refer to Figure 2A and Figure 2B . Figure 2A FIG. [X] is a schematic view of the distal end of the basket catheter 40 in a collapsed form. Figure 2B FIG. [Y] is a schematic view of the distal end of the Figure 2A basket catheter 40 in a deployed form.

[0072] Magnetic sensor 50A is a coil-based orientation sensor that is disposed at the distal end 33 of the insertion tube 22, such as in a coupling member at the distal end 33. Magnetic sensor 50B is a coil-based orientation sensor that is disposed on the distal portion 52 of the pusher 37, such as in a coupling member of the distal portion 52, and couples the distal end of the flexible strip 55 to the pusher 37. The pusher 37 is configured to be advanced and retracted through the insertion tube 22. Each of the sensors 50A, 50B can be a SAS, DAS, or TAS. The sensors 50A, 50B can be the same type of sensor or different types of sensors. If both of the sensors 50A, 50B are single-axis sensors, the catheter 40 typically includes another orientation sensor to track the roll of the assembly 35. The magnetic sensors 50A, 50B are configured to output corresponding first and second orientation signals in response to the transmitted alternating magnetic field transmitted by the magnetic field generator coil 42( Figure 1 )).

[0073] Assembly 35 is typically an expandable assembly that includes flexible strips 55 (only some are labeled for simplicity) circumferentially disposed around the distal portion 52 of the pusher 37, wherein a first end of the strip 55 is connected to the distal end 33 of the insertion tube 22 (such as a coupling member of the distal end 33) and a second end of the strip 55 is connected to the distal portion 52 of the pusher 37 (such as a coupling member of the distal portion 52). The flexible strip 55 is configured to bend radially outward when the pusher 37 retracts. A plurality of electrodes 48 (only some are labeled for simplicity) are disposed on each of the flexible strips in the flexible strip 55.

[0074] Now refer to Figure 3A , which is a flowchart 60 of steps in a method of operating a system 20 that includes a basket catheter 40 that uses Figure 2A and Figure 2B . Figure 1 of the system 20.

[0075] Processing circuitry 41( Figure 1 ) is configured to receive (block 62) the first and second orientation signals from the magnetic sensors 50A, 50B, respectively. In some embodiments, the magnetic sensor 50A can provide one or more orientation signals corresponding to one or more coils of the magnetic sensor 50A. Similarly, the magnetic sensor 50B can provide one or more orientation signals corresponding to one or more coils of the magnetic sensor 50B.

[0076] The processing circuit 41 is configured to calculate (block 64) the position and orientation coordinates of the magnetic sensors 50A, 50B based on the received signals and using azimuth calculations, wherein the position and orientation coordinates of each of the magnetic sensors 50A, 50B are calculated iteratively and interdependently in response to the respective received azimuth signals, and are subject to the constraint that the magnetic sensors 50A, 50B (including the coils) are coaxial and thus have the same orientation.

[0077] In some embodiments, the processing circuit 41 is configured to calculate the position and orientation coordinates of the magnetic sensors 50A, 50B, which are subject to the constraint that the calculated orientation coordinates of the magnetic sensors 50A, 50B will be equal within a given tolerance (such as plus or minus 2 degrees). The steps of block 64 are described in Figure 3B and Figure 3C in more detail.

[0078] The processing circuit 41 is configured to calculate (block 66) the distance between the calculated position coordinates of the magnetic sensor 50A and the calculated position coordinates of the magnetic sensor 50B. The calculated distance indicates the bending of the flexible strip 55 ( Figure 2B ) and the general shape of the basket assembly 35 ( Figure 2B ), as will be described in more detail below with reference to the steps of block 70.

[0079] The processing circuit 41 is configured to calculate (block 68) the volume of the expandable assembly 35 in response to azimuth signals from the magnetic sensor 50A and / or from the magnetic sensor 50B and / or from another azimuth sensor of the catheter 40. As previously mentioned, the sensors providing data for calculating the volume are typically DAS or TAS.

[0080] The bending of the flexible strip 55 and / or the azimuth of the electrodes 48 (or other features) on the flexible strip 55 relative to a fixed point on the catheter 40 (such as the distal end of the insertion tube 22) can be measured for various distances between the magnetic sensors 50A, 50B. For example, the azimuth of the electrodes 48 relative to the fixed point on the catheter 40 can be measured for each 0.2 mm movement of the pusher 37 relative to the insertion tube 22, and after each 0.2 mm movement, the calculated distance between the magnetic sensors 50 is recorded along with the azimuth of the electrodes 48. This data can then be used to find the bending of the flexible strip 55 and / or the azimuth of the electrodes 48 (or other features) on the flexible strip 55 relative to a fixed point on the catheter 40 (such as the distal end of the insertion tube 22) in response to the calculated distance between the magnetic sensors 50.

[0081] In some embodiments, the bending of the flexible strip 55 and / or the orientation of the electrodes 48 (or other features) on the flexible strip 55 relative to a fixed point on the catheter 40, such as the distal end of the insertion tube 22, can be calculated based on the calculated distances between the magnetic sensors 50 and a model of the catheter 40 that provides the bending of the flexible strip 55 and / or the orientation of the electrodes 48 for the calculated distances based on the mechanical properties and dimensions of the flexible strip 55.

[0082] The processing circuit 41 is configured to estimate (block 70) the respective orientation of the flexible strip 55 in response to the calculated distances, the calculated volumes, and the calculated position and orientation coordinates of one or more of the magnetic sensors 50. The calculated distances provide the respective orientation of the flexible strip 55 relative to the fixed point on the catheter 40. The calculated volumes, position, and orientation coordinates of one or more of the magnetic sensors 50 provide the respective orientation of the flexible strip 55 relative to the magnetic coordinate system used in the system 20.

[0083] The processing circuit 41 is configured to present (block 72) a representation 31 of at least a portion of the catheter 40 and a body part (e.g., the heart 26) to the display 27 ( Figure 1 ) in response to the estimated respective orientation of the flexible strip 55 and the calculated orientation of the insertion tube 22 (e.g., based on signals received from the magnetic sensor 50A). Figure 1 )

[0084] Now refer to Figure 3B , which is a flowchart 74 of sub-steps in an operating method including Figure 3A . The following sub-steps are sub-steps of the step of block 64 of Figure 3A .

[0085] The processing circuit 41 ( Figure 1 ) is configured to calculate (block 76) the position and orientation coordinates of one of the magnetic sensors 50A, 50B using orientation calculations in response to the received signal from one sensor. The processing circuit 41 is configured to calculate (block 78) the position coordinates of the other of the magnetic sensors 50A, 50B using orientation calculations, which is constrained by the calculated orientation coordinates of the other sensor being equal to the calculated orientation coordinates of one sensor within a given tolerance (such as plus or minus 2 degrees).

[0086] Now refer to Figure 3C , which is a flowchart 80 of alternative sub-steps in an operating method including Figure 3A . The following sub-steps are sub-steps of the step of block 64 of Figure 3A .

[0087] The processing circuit 41 ( Figure 1)configured to calculate (block 82) the initial position and initial orientation coordinates of the two magnetic sensors 50 using azimuth calculation.

[0088] The processing circuit 41 is configured to calculate (block 84) the average value of the initial orientation coordinates of the magnetic sensors 50. For example, if the orientation coordinates are represented by two angles θ, say, representing yaw and pitch respectively, then the orientation of the magnetic sensor 50A is θ A 、 and the orientation of the magnetic sensor 50B is θ B 、 The average orientation of the magnetic sensors 50 is equal to θ av 、 where θ av is the average of θ A and θ B and is and is the average of.

[0089] The processing circuit 41 is configured to calculate (block 86) the position and orientation coordinates of the magnetic sensors 50 using azimuth calculation based on the signals received from the magnetic sensors 50, and is constrained by the calculated average value that the orientation coordinates of the two magnetic sensors 50 will be equal to the initial orientation coordinates within a given tolerance (such as plus or minus 2 degrees).

[0090] Now refer to Figure 4A and Figure 4B . Figure 4A Schematic diagram of the distal end of the basket catheter 90. Figure 4B For Figure 4A schematic diagram of the distal end of the basket catheter 90 after being deformed to the side. The basket catheter 90 is substantially the same as the catheter 40 of Figure 2A and Figure 2B , except that the basket catheter 90 includes a pusher 92 and an expandable assembly 94 (e.g., a basket), and the expandable assembly can be pushed to the side relative to the axis of the insertion tube 96 of the basket catheter 90. For example, when the expandable assembly 94 abuts against the tissue and is pushed, the expandable assembly 94 can be deformed. Similar to the catheter 40 of Figure 2A , the basket catheter 90 includes a plurality of flexible strips 98 (only some are labeled for simplicity), electrodes 100 provided on each of the flexible strips 98 (only some are labeled for simplicity), and two magnetic sensors 102A, 102B (similar to Figure 2Amagnetic sensor 50). The magnetic sensor 102A is disposed at the distal end of the insertion tube 96 (e.g., in a coupling member that couples the insertion tube 96 to the assembly 94), and the magnetic sensor 102B is disposed at the distal end of the pusher 92 (e.g., in a coupling member that couples the pusher 92 to the distal end of the flexible strip 98).

[0091] Figure 4B It is shown that as the expandable assembly 94 is pushed against the tissue, some of the flexible strips 98 in the flexible strip 98 are more curved than other flexible strips. For example, the flexible strip 98-1 is more curved than the other flexible strips 98. Additionally, some of the flexible strips 98 (e.g., the flexible strip 98-2) are less curved than they would be if the expandable assembly 94 were not pushed against the tissue. From Figure 4B It can also be clearly seen that the magnetic sensors 102 are not coaxial, and the axis of the magnetic sensor 102B points away from the axis of the insertion tube 96 that includes the magnetic sensor 102A.

[0092] Now refer to Figure 5 , which is a flowchart 110 of steps in a method of operating a system 20 that includes a basket catheter 90 using Figure 4A and Figure 4B . Also refer to Figure 1 and Figure 4A and Figure 4B .

[0093] The processing circuit 41 ( Figure 1 ) is configured to receive (block 112) a first orientation signal and a second orientation signal from the magnetic sensors 102A, 102B, respectively. In some embodiments, the magnetic sensor 102A may provide one or more orientation signals corresponding to one or more coils of the magnetic sensor 102A. Similarly, the magnetic sensor 102B may provide one or more orientation signals corresponding to one or more coils of the magnetic sensor 102B.

[0094] The processing circuit 41 is configured to calculate (block 114) the distance and relative orientation angle between the magnetic sensors 102 in response to the received orientation signals. A relative orientation angle having a value greater than zero generally indicates that the expandable assembly 94 is deflected to one side relative to the axis of the insertion tube 96, and when the expandable assembly 94 is centered about the axis of the insertion tube 96, at least some of the flexible strips 98 in the flexible strip 98 are distorted compared to the shape of the flexible strip 98.

[0095] The processing circuit 41 is configured to calculate (block 116) the volume of the expandable assembly 94 in response to orientation signals from one or more of the magnetic sensors 102 or from another sensor disposed on the basket catheter 90.

[0096] The bending of the flexible strip 98 and / or the orientation of the electrodes 100 (or other feature structures) on the flexible strip 98 relative to a fixed point on the catheter 90, such as the distal end of the insertion tube 96, can be measured for various distances between the magnetic sensors 102 and for various relative orientation angles between the magnetic sensors 102. For example, the orientation of the electrodes 100 relative to the fixed point on the catheter 90 can be measured for approximately every 0.2 mm of movement of the pusher 92 relative to the insertion tube 96 and for every 1-degree relative orientation between the magnetic sensors 102 (up to the maximum lateral movement of the expandable assembly 94). At each different distance / relative orientation combination, the calculated distance between the magnetic sensors 50 and the calculated relative orientation angle are recorded along with the orientation data of the electrodes 100. Then, this data can be used to estimate the bending of the flexible strip 98 and / or the orientation of the electrodes 100 (or other feature structures) on the flexible strip 100 relative to a fixed point on the catheter 90, such as the distal end of the insertion tube 96, in response to the calculated distance and relative orientation angle between the magnetic sensors 102.

[0097] In addition or alternatively, the bending of the flexible strip 98 can be estimated based on the following assumptions: (a) each flexible strip in the flexible strip 98 has a fixed and known length; (b) each flexible strip in the flexible strip 98 is connected to a coupling member that couples the pusher 92 to the distal end of the flexible strip 98, substantially perpendicular (within an error of plus or minus 10 degrees) to the longitudinal axis of the coupling member; (c) each flexible strip in the flexible strip 98 is connected to a coupling member that couples the proximal end of the flexible strip 98 to the insertion tube 96, substantially parallel (within an error of plus or minus 10 degrees) to the longitudinal axis of the insertion tube 96. Based on the above assumptions (a)-(c), and based on the calculated orientation of the coupling member based on the calculated orientation of the magnetic sensors 102, a cubic polynomial can be used to calculate the bending of each flexible strip in the flexible strip 98. In some embodiments, the bending of the flexible strip 98 and / or the orientation of the electrodes 100 (or other feature structures) on the flexible strip 98 relative to a fixed point on the catheter 90, such as the distal end of the insertion tube 96, can be calculated based on the calculated distance and orientation between the magnetic sensors 102 and a model of the catheter 90 that provides the bending of the flexible strip 98 and / or the orientation of the electrodes 100 for the calculated distance based on the mechanical properties and dimensions of the flexible strip 98.

[0098] The processing circuit 41 is configured to estimate (block 118) the respective orientation of the flexible strip 98 in response to at least the calculated distance and relative orientation angle, taking into account the twist of one or more of the flexible strips 98 from a symmetric arrangement when the value of the relative orientation angle is greater than zero. The calculated distance and relative orientation angle between the magnetic sensors 102 provide the respective orientation of the flexible strip 98 relative to the fixed points of the catheter 90. The calculated roll, position, and orientation coordinates of one or more of the magnetic sensors 102 provide the respective orientation of the flexible strip 98 relative to the magnetic coordinate system used in the system 20.

[0099] The processing circuit 41 is configured to present (block 120) a representation 31 of at least a portion of the catheter 90 and a body part (e.g., the heart 26) to the display 27 ( Figure 1 ) in response to the estimated respective orientation of the flexible strip 98 and the calculated orientation of the insertion tube 96 (e.g., based on signals received from the magnetic sensor 102A). Figure 1 )

[0100] For clarity, the various features of the invention described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, for brevity, the various features of the invention described in the context of a single embodiment may be provided separately or in any suitable sub-combination.

[0101] The above embodiments are cited by way of example, and the invention is not limited to what is specifically shown and described above. Instead, the scope of the invention includes combinations and sub-combinations of the various features described above, as well as their variations and modifications, which would occur to those skilled in the art upon reading the above description and which are not disclosed in the prior art.

Claims

1. A system for tracking the orientation of a catheter, comprising: a catheter configured to be inserted into a body part of a living subject and comprising: an insertion tube including a distal end and a first coil-based orientation sensor disposed at the distal end; a pusher including a second coil-based orientation sensor disposed thereon and a distal portion, and configured to be advanced and retracted through the insertion tube; and an inflatable assembly including a plurality of flexible strips circumferentially disposed around the distal portion of the pusher, wherein a first end of the strip is connected to the distal end of the insertion tube and a second end of the strip is connected to the distal portion of the pusher, the flexible strip being configured to bend radially outward when the pusher is retracted; at least one magnetic field radiator configured to transmit an alternating magnetic field into the region in which the body part is located, the first orientation sensor and the second orientation sensor being configured to output corresponding first and second orientation signals in response to the transmitted alternating magnetic field; and a processing circuit configured to: receive the first orientation signal and the second orientation signal from the first orientation sensor and the second orientation sensor; calculate the position and orientation coordinates of the first orientation sensor and the second orientation sensor using orientation calculations, wherein the position coordinates and the orientation coordinates of each of the orientation sensors are calculated iteratively and interdependently in response to the respective received orientation signals and are subject to the constraint that the first orientation sensor and the second orientation sensor are coaxial; calculate the distance between the calculated position coordinates of the first orientation sensor and the calculated position coordinates of the second orientation sensor; and estimate the respective orientation of the flexible strip in response to at least the calculated distance.

2. The system according to claim 1, wherein Further comprising a display, wherein the processing circuit is configured to: calculate the volume of the inflatable assembly in response to the orientation signal from at least one of the first orientation sensor or the second orientation sensor; and present a representation of at least a portion of the catheter and the body part to the display in response to the estimated respective orientation of the flexible strip.

3. The system according to claim 1, wherein The processing circuit is configured to: calculate the position coordinates and the orientation coordinates of one of the first orientation sensor and the second orientation sensor using the orientation calculations; and calculate the position coordinates of the other of the first orientation sensor and the second orientation sensor, subject to the constraint that the calculated orientation coordinates of the other sensor will be equal to the calculated orientation coordinates of the one sensor within a given tolerance.

4. The system according to claim 1, wherein The processing circuit is configured to: calculate the initial position coordinates and the initial orientation coordinates of the first orientation sensor and the second orientation sensor using the orientation calculations; calculate the average of the initial orientation coordinates of the first orientation sensor and the second orientation sensor; and using the orientation calculation to calculate the position coordinates and the orientation coordinates of the first orientation sensor and the second orientation sensor, which is constrained by the calculation that the orientation coordinates of the first orientation sensor and the second orientation sensor will be equal within a given tolerance.

5. The system according to claim 1, characterized in that, The processing circuit is configured to calculate the position coordinates and the orientation coordinates of the first orientation sensor and the second orientation sensor, which is constrained by the calculation that the calculated orientation coordinates of the first orientation sensor and the second orientation sensor will be equal within a given tolerance.

6. A system for tracking the orientation of a catheter, comprising: a catheter configured to be inserted into a body part of a living subject and comprising: an insertion tube including a distal end and a first coil-based orientation sensor disposed at the distal end; a pusher including a second coil-based orientation sensor disposed thereon and a distal portion, and configured to be advanced and retracted through the insertion tube; and an inflatable assembly including a plurality of flexible strips circumferentially disposed around the distal portion of the pusher, wherein a first end of the strip is connected to the distal end of the insertion tube and a second end of the strip is connected to the distal portion of the pusher, and the flexible strip is configured to bend radially outward when the pusher is retracted; at least one magnetic field radiator configured to transmit an alternating magnetic field into the region in which the body part is located, and the first orientation sensor and the second orientation sensor are configured to output corresponding first orientation signals and second orientation signals in response to the transmitted alternating magnetic field; and a processing circuit configured to: receive the first orientation signal and the second orientation signal from the first orientation sensor and the second orientation sensor; calculate a distance and a relative orientation angle between the first orientation sensor and the second orientation sensor in response to the received orientation signals; and estimate the respective orientation of the flexible strip in response to at least the calculated distance and the relative orientation angle, taking into account the twist of one or more of the flexible strips from a symmetric arrangement when the value of the relative orientation angle is greater than zero.

7. The system according to claim 6, wherein, Further comprising a display, wherein the processing circuit is configured to: calculate a volume of the inflatable assembly in response to the orientation signal from at least one of the first orientation sensor or the second orientation sensor; and present a representation of at least a portion of the catheter and the body part to the display in response to the estimated respective orientation of the flexible strip.

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