Improved position tracking for balloon catheters

Abstract

A system includes auxiliary and main catheters and a processor. The main catheter comprises: a shaft for insertion into an organ of a patient; a first position sensor disposed on the distal end of the shaft; an expandable assembly coupled at the distal end of the shaft, the assembly including a hollow channel to allow a supplemental catheter to pass distally therethrough; and a plurality of second position sensors disposed along the distal end of the auxiliary catheter, the plurality of second position sensors configured to indicate a respective plurality of positions along the distal end of the auxiliary catheter. The processor is configured to receive indications of positions, apply a model of known mechanical characteristics of the distal end of the auxiliary catheter to the positions to calculate a curved profile of the auxiliary catheter inside the assembly, and estimate an orientation of the assembly relative to the distal end of the shaft based on the calculated curved profile.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application 63 / 521,206, filed on June 15, 2023, which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to invasive medical catheters, and particularly to cardiac catheters. Background Art

[0004] Modeling the shape of an invasive medical probe (such as a catheter) has been proposed previously in the patent literature. For example, U.S. Pat. No. 8,478,379 describes a method for visualizing a probe, the method comprising receiving an input indicating respective apparent coordinates of a plurality of points disposed along the length of the probe inside a subject's body, and applying a model of the known mechanical properties of the probe to the apparent coordinates to calculate a cost function for the shapes that the probe can take inside the body. A shape that responds to the cost function is selected, and corrected coordinates of the point along the length of the probe are generated based on the shape. The corrected coordinates are then used to display an image of the probe.

[0005] As another example, U.S. Patent 8,478,383 describes a method that includes receiving input of respective apparent positions of a plurality of points disposed along a length of a probe inside a body of a subject, and applying a model of known mechanical properties of the probe to the respective apparent positions to minimize a cost function regarding shapes that the probe can take inside the body. The method also includes: selecting a shape responsive to a minimized first cost function, and determining preliminary coordinates of the apparent positions responsive to the shape; minimizing a second cost function regarding the difference between the apparent positions and the preliminary coordinates; and generating corrected coordinates of the points along the length of the probe based on the minimized second cost function.

[0006] The present disclosure will be more fully understood through the following detailed description of examples of the present disclosure in conjunction with the accompanying drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a schematic illustration of a catheter-based electrophysiological (EP) mapping and ablation system according to one example of the present disclosure;

[0008] Figure 2A and Figure 2B According to the example of the present disclosure Figure 1 Schematic illustration of a main catheter and an auxiliary catheter extending through the main catheter in two deployment states;

[0009] Figure 3is a schematic illustration of a model geometry of an auxiliary conduit such as that in FIG. 2 according to an example of the present disclosure; and

[0010] Figure 4 is a schematic diagram illustrating the auxiliary catheter when deployed according to an example of the present disclosure. Figure 1 Flow chart of a method for tracking and visualizing the position of a balloon catheter. DETAILED DESCRIPTION

[0011] Overview

[0012] Examples of the present disclosure described herein provide a device for tracking the position (e.g., visualizing) of a main catheter including an expandable assembly (such as a balloon or basket assembly) inside a chamber of an organ (such as a cardiac catheter inside a heart). The main catheter has a hollow shaft, and the expandable assembly is fixed to the distal end of the shaft. A first position sensor (such as a tri-axis sensor (TAS)) is mounted at the distal end of the shaft to indicate the position and orientation of the distal end. The auxiliary catheter can extend through the expandable assembly and move relative to the expandable assembly.

[0013] The main catheter includes an expandable distal end assembly, such as a balloon assembly. An example of an auxiliary catheter described in detail below is a lasso-shaped catheter. The lasso-shaped catheter coaxially advances distally through the expandable balloon assembly.

[0014] The physician can manipulate the expandable assembly with an auxiliary catheter. The auxiliary catheter helps guide the expandable assembly to the desired location for treatment or diagnosis. The auxiliary catheter (also called a "guide catheter") is more flexible and smaller than the expandable assembly. This makes the auxiliary catheter easier and safer to manipulate within the ventricle.

[0015] Once the desired location (e.g., the pulmonary vein ostium) is found, the expandable assembly can be directed to that location. In order to track its position and / or orientation, the auxiliary catheter typically includes a plurality of second position sensors at its distal end, e.g., 3 uniaxial sensors (SAS), which are magnetic-based sensors. Typically, the auxiliary catheter also includes a plurality of electrodes. In some examples, the distal end of the auxiliary catheter is curved when in its expanded shape, e.g., a lasso shape.

[0016] The expandable assembly is deployed and expanded near the desired location. It is important to be able to track the location of the electrode so that the physician can determine where ablation occurs or where to capture EP signals on the tissue. However, when the physician presses the expandable assembly against the cardiac tissue, the expandable assembly may deflect. Due to the deflection, the position of the electrode on the balloon will be significantly different compared to the position of the electrode without deflection. Therefore, when the assembly is pressed against the tissue, the positioning of the electrode on the expandable assembly cannot be inferred based on the TAS on the distal end of the shaft. This is because the TAS at the distal end of the shaft does not provide any information about the deflection of the balloon relative to the shaft.

[0017] The disclosed examples use a position sensor on the secondary catheter to track the deflection of the expandable assembly. The disclosed tracking technique is further based on modeling the mechanical properties of a portion of the primary catheter and solving the model using the position signal to estimate the orientation of the expandable assembly.

[0018] The disclosed technology visualizes the shape of the secondary conduit to a user as it changes over time due to the medical procedure (e.g., due to the physician manipulating the expandable assembly) and the motion of the beating heart. The deflection of the expandable assembly relative to the axis is determined based on the shape of the secondary conduit.

[0019] In some examples, techniques are provided for position tracking of an expandable assembly coupled at the distal end of an axis inside an organ. Tracking and visualization are provided when the expandable assembly can bend relative to the axis. A model is provided that extends the catheter mechanics algorithm provided in the aforementioned U.S. Patent 8,478,379 to use non-fixed position sensors (modeled portions that are not fixed to the main catheter) so that they can slide relative to the main catheter. The sensors are fixed to the auxiliary catheter.

[0020] The auxiliary catheter section inside the rigid tube within the balloon is expected to remain nearly straight to achieve the relatively small diameter of the tube. This is modeled by adding a stiffness property to this section in the mechanical model. The stiffness property determines the degree to which the cost function increases when bending this section. High stiffness results in a high cost function value, so after cost minimization, this section tends to remain nearly straight. The degree to which the model allows the auxiliary catheter to bend within the tube is limited by the relative diameter of the tube relative to the auxiliary catheter.

[0021] In some examples, a model of a lasso catheter including three SAS is provided. A proximal magnetic-based position sensor (e.g., TAS) is mounted on the distal end of the shaft relative to which the lasso catheter slides. In the fully deployed form, the lasso has an almost straight proximal base portion and a curved distal portion forming a lasso shape. When the lasso base portion slides beside the TAS sensor, as described in U.S. Pat. No. 8,478,379, the three free parameters (to be determined) of the cost function of the disclosed model represent the position, orientation and shape of the auxiliary catheter and the position of the TAS sensor relative to a predetermined position. Specifically, in addition to the parameters in U.S. Pat. No. 8,478,379, a new free parameter, i.e., the length of the portion of the auxiliary catheter that slides distally through the TAS, represents the displacement of the TAS sensor relative to a predetermined position (e.g., one of the SAS positions). The cost function is minimized relative to all free parameters, thereby giving the position, orientation and shape of the auxiliary catheter that best fits all sensor measurements and the mechanical properties of the catheter.

[0022] The catheter mechanics algorithm architecture is used to interpolate between measured positions above the auxiliary catheter (in one example, the auxiliary catheter is a lasso catheter) to obtain its shape. The estimated shape of the auxiliary catheter extending through the balloon and the position of the position sensor mounted on the auxiliary catheter can be used to estimate and / or predict the balloon orientation and / or deflection, rather than operating under the assumption of no balloon deflection. In particular, after estimating the lasso-assisted catheter shape based on the SAS and TAS sensors, the processor estimates the balloon position and orientation. To do this, the processor uses the known position of the TAS sensor at the bottom of the balloon and the fact that the lasso-assisted catheter extends through the central distal end edge of the balloon.

[0023] This estimate is even more accurate when the lasso only partially extends through the expandable assembly such that at least one of the SAS is inside the hollow passageway inside the expandable assembly because the inner insert portion of the lasso-assisted catheter contains at least one SAS inside the assembly.

[0024] System Description

[0025] Figure 1 is a schematic illustration of a catheter-based electrophysiological (EP) mapping and ablation system 10 according to one example of the present disclosure.

[0026] System 10 includes a plurality of catheters that are inserted percutaneously through the patient's vascular system by physician 24 into chambers or vascular structures of heart 12 .

[0027] Typically, the delivery sheath 28 is catheterized into the left or right atrium near the desired location in the heart 12. Multiple catheters may then be inserted into the delivery sheath 28 to reach the desired location. In inset 45, a balloon catheter 14 is shown inserted into the left atrium 46 of the heart 12 via the sheath 28 using the shaft 22.

[0028] The multiple catheters may include catheters dedicated to sensing intracardiac electrograms (IEGMs) and / or for both sensing and ablation, as well as imaging catheters. An exemplary balloon catheter 14 configured for sensing IEGMs and for performing electrical ablation is shown herein. As further seen in inset 45, a physician 24 brings an expandable (e.g., balloon) assembly 44 mounted on the shaft 22 of the catheter 14 into contact with the heart wall to ablate a target site in the heart 12, such as a pulmonary vein ostium 47.

[0029] As seen in inset 45, an auxiliary catheter 40 having a section in the form of a preformed lasso catheter is passed distally to the balloon via a hollow passage (the passage shown in FIG. 2 ) inside the expandable assembly 44. The auxiliary catheter is used to guide and position the balloon at the ostium of the pulmonary vein 47. In addition, the helical portion of the auxiliary catheter includes a plurality of sensing electrodes (not shown) disposed thereon for acquiring IEGM around the pulmonary vein wall near the ostium.

[0030] As shown in inset 65, the balloon catheter 14 is an exemplary catheter including one and preferably a plurality of electrodes 26, which are evenly distributed around the circumference of the expandable component 44 and are configured to sense IEGM signals and perform ablation. The catheter 14 also includes: (i) an auxiliary catheter 40, which is configured to present a preformed lasso catheter when advanced distally of the expandable component 44, the auxiliary catheter having a generally curved base portion (which may be straight in the blood pool) and a lasso spiral portion; (ii) three magnetic position sensors 128, which are disposed above the distal end of the auxiliary catheter 40; and (iii) a proximal position sensor 29, which is disposed above the distal end 41 of the shaft 22 near the expandable component 44 for tracking the position of the distal end 41 of the shaft 22 and for tracking the orientation of the distal end of the shaft 22.

[0031] The magnetic-based position sensors 29 and 128 (further described in FIG. 2 ) can operate with a positioning mat 25 that includes a plurality of magnetic coils 32 configured to generate a magnetic field in a predefined workspace. Details of magnetic-based position sensing technology are described in U.S. Patents 5,5391,199, 5,443,489, 5,558,091, 6,172,499, 6,239,724, 6,332,089, 6,484,118, 6,618,612, 6,690,963, 6,788,967, and 6,892,091.

[0032] The system 10 includes one or more electrode patches 38 positioned in contact with the skin of the patient 23 to establish a position reference for the impedance-based tracking functionality of the positioning pad 25 and the electrodes 26. For impedance-based tracking, current is directed toward the electrodes 26 and sensed at the electrode skin patches 38 so that the position of each electrode can be triangulated via the electrode patches 38. Details of impedance-based position tracking techniques are described in U.S. Patents 7,536,218, 7,756,576, 7,848,787, 7,869,865, and 8,456,182.

[0033] Recorder 11 displays electrograms 21 captured using surface ECG electrodes 18 and intracardiac electrograms (IEGMs) captured using electrodes 26 of catheter 14. Recorder 11 may include pacing capabilities for pacing the cardiac rhythm and / or may be electrically connected to a separate pacemaker.

[0034] The system 10 may include an ablation energy generator 50 adapted to conduct ablation energy to one or more electrodes at the distal end of a catheter configured for ablation. The energy generated by the ablation energy generator 50 may include, but is not limited to, radio frequency (RF) energy or pulsed field ablation (PFA) energy (including monopolar or bipolar high voltage DC pulses that can be used to affect irreversible electroporation (IRE), or a combination thereof.

[0035] The patient interface unit (PIU) 30 is an interface configured to establish electrical communication between catheters, electrophysiology equipment, a power source, and a workstation 55 for controlling the operation of the system 10. The electrophysiology equipment of the system 10 may include, for example, multiple catheters, a positioning pad 25, surface ECG electrodes 18, electrode patches 38, an ablation energy generator 50, and a recorder 11. Optionally and preferably, the PIU 30 additionally includes processing capabilities for enabling real-time calculations of catheter positions and for performing ECG calculations.

[0036] The workstation 55 includes a processor 56 unit having a memory 57 or storage device loaded with appropriate operating software, and user interface capabilities. The workstation 55 can provide multiple functions, optionally including: (i) three-dimensional (3D) modeling of the endocardial anatomy and rendering the model or anatomical map 20 for display on the display device 27; (ii) displaying the activation sequence (or other data) compiled from the recorded electrograms 21 on the display device 27 as representative visual markers or images superimposed on the rendered anatomical map 20; (iii) displaying the real-time position and orientation of multiple catheters within the heart chamber; and (iv) displaying areas of interest (such as where ablation energy has been applied) on the display device 27. A commercial product embodying elements of the system 10 can be CARTO TM 3 System was purchased from Biosense Webster, Inc., 31A Technology Drive, Irvine, CA 92618.

[0037] Position-tracking balloon catheter with sliding lasso-assisted catheter

[0038] As described above, an example of a primary catheter is a balloon catheter. An example of an auxiliary catheter is a lasso catheter. As described above, the lasso catheter coaxially extends through the expandable balloon assembly.

[0039] As mentioned above, the disclosed technique aims to track the orientation (or deflection) of an expandable assembly relative to its axis. Two examples are discussed:

[0040] 1. Detect when at least one SAS mounted on the auxiliary catheter is in the expandable assembly, then determine the orientation by comparing the orientation of the shaft (known from the TAS) and the orientation of the SAS.

[0041] 2. When the SAS is outside the assembly, determine the orientation of the expandable assembly by drawing an imaginary line between the centroids of all three SASs and the 3D position of the TAS and comparing the orientation of this line to the orientation of the TAS.

[0042] Figure 2A and Figure 2B According to the example of the present disclosure Figure 1 Schematic illustration of a main catheter 14 and an auxiliary catheter 40 extending through the main catheter 14 in two deployed states.

[0043] The main catheter 14 includes an expandable balloon assembly 44, while the auxiliary catheter 40 is a lasso-shaped catheter 40. The orientation of the balloon assembly 44 when no force is applied is given by a longitudinal axis 62, wherein the longitudinal axis 62 is defined as being parallel to the orientation of the distal end portion 41 of the shaft 22. The orientation of the axis 62 is thus known from TAS 29. As shown, in practice, the balloon 44 can be deflected and oriented away from the axis 62, for example, in a deflected orientation 64 relative to the distal end 41 of the shaft 22.

[0044] exist Figure 2A In FIG. 4 , it can be seen that the secondary catheter 40 is partially advanced through the shaft 22, for example only to a point where the secondary catheter is still completely within the hollow passage 217 of the expandable assembly 44. Figure 2B , auxiliary catheter 40 is fully advanced via shaft 22 such that the distal end of auxiliary catheter 40 is fully deployed distal to expandable balloon assembly 44 and has resumed its pre-formed lasso form.

[0045] The catheter 14 includes a TAS 29 disposed on the shaft 22 of the balloon catheter. Using the TAS 29, the processor 56 tracks the position and orientation of the distal end of the shaft in three dimensions (3D). In particular, using signals from the TAS 29, the processor 56 can determine the orientation of the longitudinal axis 62 in the 3D coordinate system defined by the positioning pad 25.

[0046] The balloon catheter also includes a lasso-assisted catheter mounted through the axis of the balloon. Optionally, the lasso catheter 82 includes one or more electrodes that can be used to capture electrophysiological (EP) signals in the ventricle. The lasso mapping catheter includes three SAS 128 to track the position of, for example, an electrode 129 mounted on a lasso (e.g., such as described in U.S. Patent Application Publication 2021 / 0001084 assigned to the assignee of the current application).

[0047] exist Figure 2A , since the auxiliary catheter 40 is only partially advanced, the SAS sensor 128 remains within the hollow passage 217 within the expandable assembly 44. The presence of one SAS within the hollow passage 217 is sufficient for the processor 56 to estimate the deflected orientation 64 based on the SAS output signal, and subsequently infer the orientation 64 of the balloon 44 relative to the distal end of the shaft 22 (e.g., relative to the orientation 62).

[0048] As shown, the deflection is schematically shown as being generally parallel to the orientation 64 along the longitudinal axis of the rigid channel 217. Figure 2AIn the example of FIG. 4 , the auxiliary catheter 40 is substantially straight. Based on the estimated distance between the SAS position and the TAS 29, it is known that one or more SAS are inside the balloon, compared to the known length of the rigid channel 217. Using the readings from the TAS 29 and the SAS 128, the amount of balloon deflection is derived from the deflection of the auxiliary catheter 40 inside the rigid channel 217.

[0049] exist Figure 2B , a section 80 of the secondary catheter 40 inside the balloon 44 is straight along the deflected orientation 64 to be determined. A generally curved distal section 82 is located between the distal tip of the balloon (e.g., the distal pole of a balloon having a spherical shape) 65 and the estimated average position 66 of the lasso center point. The position 66 and the orientation 68 at the position 66 (i.e., the orientation 58) are estimated based on the signal provided by the SAS 128 when deployed in the lasso configuration.

[0050] Based on the output from TAS 29 and each SAS sensor 128, use the following Figure 3 The model described is applied to the entire auxiliary catheter to deduce the orientation 64. The centroid of the location of the SAS 128 is estimated 66.

[0051] Model of balloon catheter orientation

[0052] Figure 3 2 is a schematic illustration of the geometry of a model 360 of an auxiliary catheter such as FIG. 2 according to an example of the present disclosure. In model 360, points E0, E1, E2, and E3 represent the calculated positions of the position sensors based on the measured positions of points M0, M1, M2, and M3. The M0 data point comes from TAS29, which is not fixed to the auxiliary catheter, while data points M1 to M3 come from SAS128. The model must overcome the inherent accuracy limitations of any position measurement (e.g., 1 mm). Therefore, the model calculates points E1, E2, and E3 (inferred from measurements), assuming that these points are fixed to the axis, while point E0 can slide on the axis. The amount of sliding is represented by S, which in this example represents the distance (on the axis) to the fixed point E3. The cost function according to an example of the present disclosure is used to find the point E j and M j The model 630 comprises straight rigid segments 362, 364 and 366 connected by joints 368 and 370 that allow rotation (bending and torsion). The position of segment 362 is described by the position matrix x0, and the orientation of segment 62 is given by the matrix o0.

[0053] The orientation matrix o0 is the local reference frame of segment 362, whose {rotation (x)} and The axis is perpendicular to section 362, and the {winding (z)} axis points along section 362. Section 364 starts at the end of section 362 (i.e., via connection joint 368), and its orientation is given by matrix o1. Section 366 starts at the end of section 364 (i.e., via connection joint 370), and its orientation is given by matrix o2. Matrices o0, o1, and o2 describe the actual state (i.e., shape) of the main conduit, where external forces cause the main conduit to deviate from its free state (i.e., no external forces are applied to the main conduit). Although the model geometry 360 includes three sections, alternative model geometries may include fewer than three or more than three sections.

[0054] Referring to Figure 2, the position vector x0 and the orientation matrix o0 are related to TAS29 and orientation 62, respectively. The position vector x3 and the orientation matrix o3 are related to the average position 66 and orientation 68 calculated according to the SAS128 signal, respectively. The measured values of the position vector x2 and the orientation matrix o2 do not exist and have a weight of zero in the following relevant equations.

[0055] The physical properties of the auxiliary conduit that affect its shape are defined by the parameters {N, L k , G k (d), P k and S}, where:

[0056] N: The number of sections.

[0057] L k : The section lengths (not necessarily equal), 0 ≤ k < N.

[0058] G k (d): The rotation matrix as a function of the deflection parameter d for a deflectable main conduit (or a constant matrix for a preformed main conduit), 1 ≤ k < N. This matrix represents the relative rotation between section k and section (k - 1) when no external forces are applied (i.e., the main conduit is in its free shape).

[0059] P k : The list of position sensors, e.g., SAS on section k, where 0 ≤ k < N. Each position sensor is represented by its distance from the start of the section and its type (e.g., ACL electrode, SAS, or TAS magnetic sensor). The list for each section may contain any number of position transducers, including zero position transducers.

[0060] S: The distance along the axis from the fixed point to the sliding sensor.

[0061] The physical properties of the auxiliary conduit are described by the parameters {A k , B k}, which represent the resistance of the joint between section k and section (k - 1) to bending and torsion (e.g., deflection resistance or stiffness), respectively.

[0062] As the doctor moves the catheter within the patient, the processor receives position signals from the sensor at regular time intervals. For each position measurement based on the position sensor, the processor generates a corresponding position measurement, which may include a position vector (all types of transducers), a single-axis sensor (SAS), and / or a total orientation sensor (TAS). The measurement value parameters include:

[0063] M j : Position measurement.

[0064] M j or : Orientation measurement.

[0065] The processor applies a cost function to calculate the quality of the match between the main catheter model and the received position data. This match defines, according to the model, the probe shape with the lowest cost, which in turn gives the corrected coordinates of the points along the length of the auxiliary catheter corresponding to the positions of the position transducers. The state of the auxiliary catheter determined by the processor describes its position, shape, and its deflection value. The state is given by the variables {x0, r k , d}:

[0066] x0: The position of the starting point of the first section (i.e., in Figure 3 ).

[0067] r k : For 0 < k < N, the orientation of section k relative to section k - 1, and for k = 0, the global orientation of the first section:

[0068]

[0069] d: The value of the deflection parameter (for a deflectable main catheter). These values do not affect the position and shape of the auxiliary catheter, but they do affect the calculation of the cost function and thus the result of the auxiliary catheter mechanics algorithm.

[0070] The processor applies a minimization algorithm to the cost function in order to find the minimum-cost main catheter state that achieves the minimum value of the cost function (i.e., the best match).

[0071] The cost function has three parts: internal energy, position error, and orientation error. First, the processor calculates an internal energy score, which represents the deviation of the auxiliary catheter from its free shape (or the family of free shapes parameterized by the deflection variables of the deflectable main catheter). For joints 368 and 370, the orientation difference between the actual relative orientation and the current deflection is calculated as follows:

[0072]

[0073] The processor converts this orientation difference into bending and torsion angles:

[0074] {α k ,β k}=angle(dr k ) (2)

[0075] The processor uses the main control model parameters {A k , B k}Calculate the internal energy score:

[0076]

[0077] The processor then calculates a position error score that represents the position error between the position of the position transducer given by the dominant control model and state and the actual measurement. The processor represents the position of the position transducer according to the dominant control model and state as E j , and the corresponding measurement result is expressed as M j , and the weighted position error is calculated as follows:

[0078]

[0079] Where P is the number of position sensors, w j are weights that are adjusted as the algorithm runs.

[0080] The processor then calculates an orientation error score that represents the orientation error between the position of the position sensor given by the main conduit model and state and the actual measurement received. The orientation of each point along the auxiliary conduit represented by the model is a discontinuous function with abrupt changes (different from the position) at the model joints. After the orientation of all relevant position sensors is calculated according to the model The processor then calculates the orientation relative to the measured Angle difference:

[0081]

[0082] And the total weighted orientation error:

[0083]

[0084] The processor then calculates the cost function as a weighted combination of the three components (i.e., internal energy, position error, and orientation error):

[0085] Cost(x0,r k ,d)=λ int E int +λ pos E pos +λ or E or (7)

[0086] Value {λ int ,λ pos ,λ or}Describes the relative importance of the deviation of the auxiliary catheter from its free shape with respect to position and orientation errors.

[0087] As mentioned above, the processor makes the function cost {x0, r k , d} is minimized with respect to the main control state variables so as to achieve the best match between the main control model and the actual measurements received. The minimization can be done by any suitable numerical method. In one example of the present disclosure, the processor uses the Broyden-Fletcher-Goldfarb-Shanno (BFGS) minimization algorithm.

[0088] Since minimizing the cost function employs an iterative algorithm (i.e., each iteration of the algorithm improves the estimate of the solution), and the position and shape of the auxiliary catheter changes slowly between measurements, the inventors have found that it is generally sufficient to apply only one iteration of the cost function minimization algorithm for each consecutive measurement.

[0089] Improved position tracking method for balloon catheters

[0090] Figure 4 is a schematic diagram illustrating the auxiliary catheter 40 when deployed according to an example of the present disclosure. Figure 1 Flow chart of a method for position tracking and visualization of a balloon 44 catheter 14. The physician begins a clinical procedure by inserting the expandable assembly 44 into the patient's heart chamber via a sheath and expanding the expandable assembly therein. According to the example presented, the algorithm performs a process that begins with preloading the main catheter deflection module into the processor 56 at a module loading step 402. Typically, the deflection module will be available in a common menu of the mapping and ablation system.

[0091] Then, at a position data receiving step 404, processor 56 may receive relevant measurement data from position sensors 29 and 128 of primary and secondary catheters 14, 40, respectively.

[0092] At the catheter positioning step 406, the physician manipulates the catheter to bring the electrodes mounted on the distal portion of the basket assembly into firm contact with the tissue in order to ablate the target tissue (e.g., the ostium of a pulmonary vein). At this stage, the distance S between the TAS 29 and the SAS 128 is known, so the processor 56 can identify when the SAS is inside the expandable assembly 44 and when it is outside the expandable assembly.

[0093] Finally, at a primary catheter visualization step 408, after determining the minimum cost primary catheter state, the processor presents a map of the heart chamber on the display 27 showing the position and orientation of the balloon 44 inside the cavity.

[0094] Figure 4 The flowchart shown is chosen purely for conceptual clarity. This example may also include additional steps of the algorithm, such as estimating the contact force of the balloon 44 on the tissue. This step and other possible steps are intentionally omitted from the disclosure herein in order to provide a more simplified flowchart.

[0095] Example

[0096] Example 1

[0097] A system (10) includes an auxiliary catheter (40), a main catheter (14), and a processor (56). The main catheter (14) includes: (i) a shaft (22) for insertion into an organ of a patient; (ii) a first position sensor (29) disposed on a distal end of the shaft; (iii) an expandable component (44) coupled to the distal end of the shaft (22), the expandable component (44) including a hollow channel (217) to allow the auxiliary catheter (40) to pass distally through the expandable component (44); and (iv) a plurality of second position sensors (128) disposed along the distal end of the auxiliary catheter (40), the plurality of second position sensors being configured to indicate a corresponding plurality of positions along the distal end of the auxiliary catheter (40). The processor (560) is configured to (i) receive indications of multiple locations, (ii) apply a model of known mechanical properties of the distal end of the auxiliary catheter (40) to the multiple locations to calculate a bending profile of the auxiliary catheter (40) within the expandable component (44), and (iii) estimate the orientation of the distal end of the expandable component (44) relative to the shaft (22) based on the calculated bending profile.

[0098] Example 2

[0099] A system (10) according to Example 1, wherein the distal portion of the distal end of the auxiliary catheter (40) is configured to regain a pre-formed lasso form when leaving the hollow channel (217).

[0100] Example 3

[0101] A system (10) according to Example 1, wherein one or more of the position sensors (128) are magnetic position sensors disposed above the distal end of the auxiliary catheter (40).

[0102] Example 4

[0103] The system (10) of Example 1, wherein the expandable component (44) is an expandable balloon.

[0104] Example 5

[0105] A system (10) according to Example 1, wherein the model of the known mechanical properties of the auxiliary catheter (40) includes (i) multiple segments (362, 364, 366) of the auxiliary catheter (40), (ii) the length of each of the segments, (iii) a rotation matrix that defines the relative rotation of each segment in the segments relative to the previous segment, and (iv) multiple positions on the auxiliary catheter (40).

[0106] Example 6

[0107] A system (10) according to Example 1, wherein the processor (56) is configured to apply a model of known mechanical properties of the distal end of the auxiliary catheter (40) by assuming that at least one segment (362) of the auxiliary catheter is located within a straight rigid channel (217) of the expandable component (44).

[0108] Example 7

[0109] The system (10) of embodiment 1, wherein the processor (56) is further configured to display the orientation of the expandable component (44) to a user.

[0110] Example 8

[0111] A method comprising receiving indications of a plurality of positions from a first position sensor (29) disposed on a distal end of a shaft (22) for insertion into an organ of a patient, the distal end of the shaft (22) being coupled to an expandable assembly (44), the expandable assembly including a hollow passage (217) to allow an auxiliary catheter (40) to pass distally through the expandable assembly (44), and from a plurality of second position sensors (128) disposed along the distal end of the auxiliary catheter (40). A model of known mechanical properties of the distal end of the auxiliary catheter (40) is applied to the plurality of positions to calculate a bending profile of the auxiliary catheter (40) within the expandable assembly (44). Based on the calculated bending profile, an orientation of the expandable assembly (44) relative to the distal end of the shaft (22) is estimated.

[0112] Although the embodiments described herein are primarily directed to cardiac diagnostic applications, the methods and systems described herein may also be used in other medical applications.

[0113] It should be understood that the above embodiments are cited by way of example, and the present disclosure is not limited to what is specifically shown and described above. On the contrary, the scope of the present disclosure includes combinations and sub-combinations of the aforementioned various features and their variations and modifications, which should be expected by those skilled in the art when reading the above description and which are not disclosed in the prior art.

Claims

1. A system, comprising: Auxiliary catheter; A main conduit, the main conduit comprising: a shaft for insertion into an organ of a patient; a first position sensor disposed on a distal end of the shaft; an expandable assembly coupled to the distal end of the shaft, the expandable assembly including a hollow passage to allow the auxiliary catheter to pass distally therethrough; and a plurality of second position sensors disposed along a distal end of the secondary catheter, the plurality of second position sensors being configured to indicate a corresponding plurality of positions along the distal end of the secondary catheter; and A processor, the processor being configured to: receiving an indication of the plurality of locations; applying a model of known mechanical properties of the distal end of the secondary catheter to the plurality of locations to calculate a bending profile of the secondary catheter within the expandable assembly; and Based on the calculated bending profile, an orientation of the expandable component relative to the distal end of the shaft is estimated.

2. The system according to claim 1, wherein: A distal portion of the distal end of the auxiliary catheter is configured to re-acquire a pre-formed lasso form upon exiting the hollow passage.

3. The system according to claim 1, wherein: One or more of the position sensors are magnetic position sensors disposed over the distal end of the secondary catheter.

4. The system according to claim 1, wherein: The expandable component is an expandable balloon.

5. The system according to claim 1, wherein: The model of the known mechanical properties of the auxiliary conduit includes (i) multiple segments of the auxiliary conduit, (ii) the length of each of the segments, (iii) a rotation matrix defining the relative rotation of each of the segments relative to the previous segment, and (iv) the multiple positions on the auxiliary conduit.

6. The system according to claim 1, wherein: The processor is configured to apply the model of known mechanical properties of the distal end of the secondary catheter by assuming that at least a section of the secondary catheter is located within a straight rigid channel of the expandable assembly.

7. The system according to claim 1, wherein: The processor is further configured to display the orientation of the expandable component to a user.

8. A method comprising: receiving indications of the plurality of positions from a first position sensor disposed on a distal end of a shaft for insertion into an organ of a patient, the distal end of the shaft being coupled to an expandable assembly, the expandable assembly including a hollow passageway to allow passage of an auxiliary catheter distally therethrough, and from a plurality of second position sensors disposed along the distal end of the auxiliary catheter; applying a model of known mechanical properties of the distal end of the secondary catheter to the plurality of locations to calculate a bending profile of the secondary catheter within the expandable assembly; as well as Based on the calculated bending profile, an orientation of the expandable component relative to the distal end of the shaft is estimated.

9. The method according to claim 8, wherein: A distal portion of the distal end of the auxiliary catheter is configured to re-acquire a pre-formed lasso form upon exiting the hollow passage.

10. The method according to claim 8, wherein: One or more of the position sensors are magnetic position sensors disposed over the distal end of the secondary catheter.

11. The method according to claim 8, wherein: The expandable component is an expandable balloon.

12. The method according to claim 8, wherein: The model of the known mechanical properties of the auxiliary conduit includes (i) multiple segments of the auxiliary conduit, (ii) the length of each of the segments, (iii) a rotation matrix defining the relative rotation of each of the segments relative to the previous segment, and (iv) the multiple positions on the auxiliary conduit.

13. The method according to claim 8, wherein: The model applying known mechanical properties of the distal end of the secondary catheter includes assuming that at least a section of the secondary catheter is located within a straight rigid channel of the expandable assembly.

14. The method of claim 8, further comprising displaying the orientation of the expandable component to a user.

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