TECHNICAL FIELD

The present disclosure relates generally to electrophysiological imaging for guiding treatment procedures, and, in particular, to electrophysiological systems and methods for imaging volumes of the body and guiding balloon therapy procedures. For example, a mapping and guidance system can include a processing circuit configured to control an electrophysiology catheter to guide a balloon to be positioned at a treatment site.

BACKGROUND

Therapeutic balloons have been used recently to treat a variety of different ailments and disorders, including blood vessel occlusions and heart arrhythmias. For example, atrial fibrillation (AF) is an abnormal heart rhythm characterized by rapid and irregular beating of the atria, and may be associated with heart palpitations, fainting, lightheadedness, shortness of breath, or chest pain. The disease is associated with an increased risk of heart failure, dementia, and stroke. AF may be caused by electrical pulses generated by secondary pacers at the ostium of the pulmonary veins. Accordingly, one way of treating AF is by pulmonary vein isolation, which can include ablating the inner wall of the left atrium to form lesions that isolate the ostium of the pulmonary veins from the rest of the left atrium. Ablation can be performed in various ways, including radiofrequency (RF) ablation, ultrasonic ablation, and cryoablation. RF ablation is a conventional ablation procedure that involves powering an RF electrode to create contiguous, transmural lesions using heat energy. RF ablation suffers from some drawbacks, such as a longer procedure time and small gaps in the lesions that cause AF to return over time, and even immediately.

Balloon-based therapy procedures, such as balloon angioplasty and balloon ablation can provide several advantages, including a shorter procedure time and the ability to treat an entire circumferential area (e.g., a blood vessel, pulmonary vein ostium) with a single deployment. For example, in cryoablation, an inflatable cryoballoon is inflated and cooled to a temperature (e.g., below -65° C) that causes an electrically-isolating lesion or firewall in the tissue. In conventional systems, the cryoballoon is maneuvered to and positioned at the ablation site, typically the ostium of a pulmonary vein. The cryoballoon is inflated, cooled, and positioned to fully occlude blood flow of the pulmonary vein from the left atrium. In this way, it can be assured that the lesion formed from the cryoablation will electrically isolate the pulmonary vein from the left atrium. As another example, a RF balloon comprising a plurality of electrodes can be maneuvered to and positioned at the ablation site, typically the ostium of a pulmonary vein. The RF balloon is positioned such that it fully occludes blood flow of the pulmonary vein from the left atrium. In this way, it can be assured that the lesion formed from the energy delivered by the electrodes electrically isolates the pulmonary vein from the left atrium.

Some challenges with balloon therapy include guiding the ablation balloon (e.g., cryoballoon) to the ablation site, and ensuring that the balloon is placed and oriented to maintain contact with a full circumference of the ostium. If the balloon is misaligned during ablation, the resulting lesion can include one or more gaps which result in reconduction and recurrence of the arrhythmia thereby requiring a re-do procedure when the AF symptoms return.

In conventional methods, angiographic and/or fluoroscopic procedures are used to guide the balloon to the ablation site. Once the inflated balloon is in place, a contrast agent or dye is introduced into the pulmonary vein to detect leaks or gaps in the interface between the balloon and the ostium of the pulmonary vein prior to ablating the tissue. When gaps exist, a portion of contrast agent will leak through into the left atrium. This leaked portion can be detected under fluoroscopy, which indicates that the balloon is not yet fully occluding blood flow from the pulmonary vein into the left atrium, and therefore is not optimally positioned to completely isolate the pulmonary vein from the left atrium. Accordingly, the physician can adjust the balloon until no residual leaks of the contrast agent are seen.

There are some shortcomings to using angiography and contrast agent to guide balloon ablation procedures. For example, patients and physicians may prefer to avoid x-ray radiation emitted during angiography and fluoroscopy procedures. Furthermore, guiding the balloon to the ablation site may be an imprecise and difficult processes that requires special expertise. It may be unadvisable to use contrast agent for some patients, and the contrast agent may not adequately identify leaks between the ostium of the pulmonary vein and the balloon. For example, at least 20% of the population has some type of contraindication for contrast agents, including allergic reactions and kidney failure.

Aspects of the present disclosure provide devices, systems, methods and computer programs for guiding a balloon therapy procedure by providing a visualization of the volumetric position of at least a part of the balloon within an anatomical cavity of a patient.

For example, in one (aspect) embodiment, a processor circuit is configured to control a plurality of electrodes (e.g., EP catheter electrodes) to detect an electromagnetic (EM) field, and determine the location of the balloon based on the detected EM field and a geometric parameter associated with the balloon. In some embodiments, the geometric parameter may include an assumption or known geometric characteristic of the balloon (e.g., size, position relative to catheter), and can be used by the processor circuit as an input to a location determination function for identifying and visualizing the inflated balloon. In some embodiments, the visualization is output to a display along with a map or image of the anatomical cavity. The visualization may be updated based on detected movement of the balloon to provide a real time view of the location of the balloon within the anatomical cavity.

According to one embodiment of the present disclosure, an apparatus for guiding balloon therapy within an anatomical cavity comprises a processor circuit configured for communication with a plurality of electrodes. In some embodiments, the processor circuit is configured to: control the plurality of electrodes to detect an electromagnetic field within the anatomical cavity; receive a geometrical parameter associated with a balloon configured to provide the balloon therapy within the anatomical cavity; determine, based on the detected electromagnetic field and the geometrical parameter associated with the balloon, a location of the balloon within the anatomical cavity; and output a signal representative of a visualization of the location of the balloon within the anatomical cavity.

In some embodiments, the processor circuit is configured to: control the plurality of electrodes to detect the electromagnetic field at a first time before the balloon is inflated and a second time after the balloon is inflated, compute, based on the electromagnetic field detected at the first time, a first conductance map of the anatomical cavity corresponding to the first time; compute, based on the electromagnetic field detected at the second time, a second conductance map of the anatomical cavity corresponding to the second time; compare the first conductance map and the second conductance map to determine a change in a conductance field of the anatomical cavity between the first time and the second time; and determine, based on the geometrical parameter and the determined change in the conductance field, the location of the balloon within the anatomical cavity. In some embodiments, the processor circuit is configured to control a plurality of catheter- mounted electrodes to detect the electromagnetic field at the first time and the second time. In some embodiments, the processor circuit is configured to control the plurality of catheter- mounted electrodes to emit the electromagnetic field at the first time and the second time. In some embodiments, the processor circuit is configured to control the plurality of catheter- mounted electrodes to detect the electromagnetic field based on combinations of a receiving electrode of the plurality of catheter-mounted electrodes and an emitting frequency. In some embodiments, the processor circuit is configured to control a plurality of external electrodes to emit the electromagnetic field at the first time and the second time.

In some aspects, the processor circuit is configured to: control a plurality of catheter-mounted electrodes to detect the electromagnetic field within the anatomical cavity; control the plurality of catheter-mounted electrodes to detect a fault condition in which each catheter-mounted electrode of the plurality of catheter-mounted electrodes is occluded; and determine the location of the balloon within the anatomical cavity based on the detected fault condition and the geometric parameter associated with the balloon. In some embodiments such occlusion is due to shielding by a part (such as sheath) of a balloon, a balloon catheter comprising a balloon and/or a sheath for receiving a balloon catheter and/or the catheter mounted electrodes. In some embodiments, the geometrical parameter comprises one or more of: a relative positioning of the balloon relative to the plurality of electrodes; a shape of the balloon; a boundary condition of the balloon within the anatomical cavity; or a geometric dimension of the balloon when inflated. In some embodiments, the visualization of the location of the balloon comprises a graphical representation of a shape of the balloon when inflated, within the anatomical cavity. In some embodiments, the processor circuit is configured to update the graphical representation of the shape of the balloon positioned relative to the anatomical cavity, in real time, based on the detected electromagnetic field. In some embodiments, the processor circuit is configured to output the signal representative of a visualization of the location of the balloon to a display in communication with the processor circuit.

According to another embodiment of the present disclosure, a system for guiding balloon therapy within an anatomical cavity comprises: an apparatus as described herein; and an electrophysiology catheter comprising an elongate tip member configured to be positioned distally of the balloon. In some embodiments, the plurality of electrodes is positioned on the elongate tip member. According to another embodiment of the present disclosure, a method for guiding balloon therapy within an anatomical cavity comprises: controlling a plurality of electrodes to detect an electromagnetic field within the anatomical cavity; receiving a geometrical parameter associated with a balloon configured to provide the balloon therapy within the anatomical cavity; determining, based on the detected electromagnetic field and the geometrical parameter associated with the balloon, a location of the balloon within the anatomical cavity; and outputting a signal representative of a visualization of the location of the balloon within the anatomical cavity.

In some embodiments, controlling the plurality of electrodes comprises: controlling the plurality of electrodes to detect the electromagnetic field at a first time before inflating the balloon; and controlling the plurality of electrodes to detect the electromagnetic field at a second time after inflating the balloon. In some embodiments, determining the location of the balloon within the anatomical cavity comprises: computing, based on the electromagnetic field detected at the first time, a first conductance map of the anatomical cavity corresponding to the first time; computing, based on the electromagnetic field detected at the second time, a second conductance map of the anatomical cavity corresponding to the second time; comparing the first conductance map and the second conductance map to determine a change in a conductance field of the anatomical cavity between the first time and the second time; and determining, based on the geometrical parameter and the determined change in the conductance field, the location of the balloon within the anatomical cavity.

In some embodiments, controlling the plurality of electrodes to detect the electromagnetic field comprises controlling a plurality of catheter-mounted electrodes to detect the electromagnetic field. In some embodiments, the method further comprises controlling the plurality of catheter-mounted electrodes to emit the electromagnetic field. In some embodiments, controlling the plurality of catheter-mounted electrodes to detect the electromagnetic field comprises controlling the plurality of catheter-mounted electrodes to detect the electromagnetic field based on combinations of a receiving electrode of the plurality of catheter-mounted electrodes and an emitting frequency.

In some embodiments, controlling the plurality of electrodes to emit the electromagnetic field comprises controlling a plurality of external electrodes to emit the electromagnetic field. In some embodiments, controlling the plurality of electrodes comprises controlling a plurality of catheter-mounted electrodes to detect the electromagnetic field within the anatomical cavity. In some embodiments, determining the location of the balloon within the anatomical cavity comprises: controlling the plurality of catheter-mounted electrodes to detect a fault condition in which each catheter-mounted electrode of the plurality of catheter-mounted electrodes is occluded; and determining, based on the detected fault condition and the geometric parameter associated with the balloon, the location of the balloon within the anatomical cavity.

In some embodiments, the geometrical parameter comprises one or more of: a relative positioning of the balloon relative to the plurality of electrodes; a shape of the balloon; a boundary condition of the balloon within the anatomical cavity; or a geometric dimension of the balloon when inflated. In some embodiments, outputting the visualization of the location of the balloon comprises outputting a graphical representation of a shape of the balloon when inflated, within the anatomical cavity. In some embodiments, the method further comprises updating the graphical representation of the shape of the balloon positioned relative to the anatomical cavity, in real time, based on the detected electromagnetic field.

In accordance with another embodiment of the present disclosure, a computer program product includes: a non-transitory computer-readable medium having program code recorded thereon, the program code including: code for controlling a plurality of electrodes to detect an electromagnetic field within an anatomical cavity; code for receiving a geometrical parameter associated with a balloon configured to provide therapy within the anatomical cavity; code for determining, based on the detected electromagnetic field and the geometrical parameter associated with the balloon, a location of the balloon within the anatomical cavity; and code for outputting a visualization of the location of the balloon within the anatomical cavity.

Additional aspects, features, and advantages of the present disclosure will become apparent from the following detailed description.

In some embodiments the processor is configured to cause the processing circuit to control the electrodes. In such embodiments the processor circuit is configured to control the electrodes while the processor is capable of providing instructions to do so. As will be further described herein, the processor circuit may include signal processing devices for providing the signals to any electrodes or receive the signal from any electrodes. The processing circuit may include devices to transform the signals into EM field data (e.g. in digital format) representative of the detected fields so that the data may be processed by the processor. BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the present disclosure will be described with reference to the accompanying schematic drawings, of which:

Fig. 1 is a graphical depiction of a cryoballoon and EP catheter positioned at the PV ostium with complete occlusion, according to aspects of the present disclosure.

Fig. 2 is a diagrammatic view of an EP-guided cryoablation system, according to aspects of the present disclosure.

Fig. 3 is a diagrammatic view of a processor circuit, according to aspects of the present disclosure.

Fig. 4 is a flow diagram of a method for providing EP -based balloon visualization and guidance for a balloon ablation procedure, according to aspects of the present disclosure.

Fig. 5 is a graphical view of a user interface for EP-guided balloon ablation, according to aspects of the present disclosure.

Fig. 6 is a graphical view of a graphical user interface for providing EP-based balloon visualization and guidance for a balloon ablation procedure.

Fig. 7 is a flow diagram of a method for providing EP-based balloon visualization and guidance for a balloon ablation procedure using conductance mapping, according to aspects of the present disclosure.

Fig. 8 is a diagrammatic view of a natives matrix of electrical signals used to determine PV occlusion by a balloon, according to aspects of the present disclosure.

Fig. 9 is a flow diagram of a method for providing EP-based balloon visualization and guidance for a balloon ablation procedure using an EP electrode fault detection technique, according to aspects of the present disclosure.

Fig. 10 is a cross-sectional view of a therapeutic balloon positioned at a stenosed segment within a vessel, according to aspects of the present disclosure.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It is nevertheless understood that no limitation to the scope of the disclosure is intended. Any alterations and further modifications to the described devices, systems, methods and computer programs, and any further application of the principles of the present disclosure are fully contemplated and included within the present disclosure as would normally occur to one skilled in the art to which the disclosure relates. For example, although the following disclosure may refer to embodiments that include balloon therapy procedures, cryoablation, cyroballoons, cryocatheters, balloon angioplasty, RF balloon ablation, or RF balloons, it will be understood that such embodiments are exemplary, and are not intended to limit the scope of the disclosure to those applications. For example, it will be understood that the devices, systems, methods and computer programs described herein are applicable to a variety of treatment procedures in which a balloon is used to occlude a body lumen or body cavity. In particular, it is fully contemplated that the features, components, and/or steps described with respect to one aspect and/or one embodiment having particular advantages may be combined with the features, components, and/or steps described with respect to other aspects and/or embodiments of the present disclosure and result in the same or similar advantages. For the sake of brevity, however, the numerous iterations of these combinations will not be all described separately.

As mentioned above, fluoroscopy-based approaches used in guiding balloon therapy procedures, including navigation and deployment of the balloon at the therapy site (e.g., blood vessel stenosis, pulmonary vein ostium), suffer from various drawbacks. It may be desirable to provide an approach for guiding a balloon treatment procedure without using fluoroscopy and/or contrast agent. The present disclosure provides systems, methods, devices and computer programs for assisting in and guiding a balloon therapy procedure using electrical field detection for balloon visualization within an anatomical map. As will be further described below, an electrophysiology system also referred to as dielectric imaging or mapping system or electroanatomical imaging or mapping system can be used to provide for image- or map guided delivery of a balloon, such as an ablation balloon (RF-, Cryo- or other), an angioplasty balloon, or a scoring balloon into an anatomical cavity, such as the left atrium or a blood vessel, and to facilitate deployment and placement of the balloon at the treatment site.

The devices, systems, methods and computer programs are advantages as they may be used in balloon therapy guidance. They allow visualization and/or tracking of a location and or orientation of balloons of any type without having to use electrodes disposed on or over the surface of the balloon for tracking. This will become further apparent from the description herein. This is to say that although balloons exist that have electrodes disposed thereon for ablation purposes, these electrodes do not have to be used for locating the balloon. They may however be used in some embodiments to detect a fault condition with or of

In that regard, Fig. 1 is a graphical view of an inflated ablation balloon 132 positioned at the ostium of the pulmonary vein (PV) 10. In an exemplary embodiment, the balloon 132 is cryoballoon, but other types can be used. The cryoballoon 132 is configured to be inflated and then, when in contact with the treatment site such as in this case the ostium of the PV at least partially filled with a cooling fluid to cool the cryoballoon to a temperature (e.g., below -65° C) that causes an electrically-isolating lesion or firewall in the tissue of the treatment site (in this case the PV ostium). For example, the cryoballoon 132 may be in fluid communication with a source or reservoir of cooling fluid via one or more fluid lines positioned within a flexible elongate member 134. Further, the cryoballoon 132 may be in fluid communication with an air or gas source, e.g., for balloon inflation, via one or more fluid lines positioned within the flexible elongate member 134.

The balloon 132 may be coupled to a distal portion of a flexible elongate member 134 that is protruding out a distal end of a sheath 136. In some embodiments, the flexible elongate member is slidable within the sheath 136. In some embodiments the flexible elongate member comprises a lumen in which an EP catheter 120 may be slidably inserted. In some embodiments the sheath 136 is first introduced into the left atrium, and used to guide the EP catheter 120 to the ablation site, since the EP catheter 120 can be slidably introduced in the sheath 136. The flexible elongate member 134 including the balloon 132 in deflated or folded state may then be moved over the EP catheter 120 and within the sheath 136 to the ablation site, inflated or deployed and positioned such that a full circumference of the inflated or deployed balloon 132 is in contact with an entire circumference of the ostium of the PV 10 (or other anatomic lumen to be treated), and such that the ablation can be delivered around the entire circumference. In this way, a full contiguous occlusion can be achieved in one ablation attempt, which increases the likelihood that the ablation results in complete electrical isolation of the inner part of the PV from the left atrium. The approaches described in the present disclosure advantageously allow visualized guidance and placement of the ablation balloon (or other balloon) at the treatment site.

Fig. 2 is an EP cryoablation system 100 according to aspects of the present disclosure. The EP cryoablation system 100 of Fig. 2 includes a cryoballoon catheter 130. Although a cryo-ablation system is shown, the description of this system will also apply to systems for another balloon therapy such as RF therapy. In such cases the system 100 may comprise a balloon suitable for such other balloon therapy and the corresponding equipment necessary for performing such therapy (e.g. RF generators and the like).

The system of Fig. 2 includes an EP catheter 120. In some embodiments, the EP catheter 120 extends through a lumen of the cryoballoon catheter 130 and as described herein before is slidable within the lumen of the catheter 130. The EP catheter 120 is communicatively coupled to an EP catheter interface 112, which is communicatively coupled to a mapping and guidance system 114.

The cryoballoon catheter 130 may include an inflatable cryoballoon 132 coupled to a distal portion of a flexible elongate member 134, which may comprise a sheath 135. The EP catheter 120 may be positioned at least partially within a lumen of the flexible elongate member 134 such that a distal portion 122 of the EP catheter 120, which comprises a plurality of electrodes positioned on an elongate tip member, may protrude out a distal end of the cryoballoon catheter 130. For example, the cryoballoon catheter 130 may comprise a lumen configured to slidably receive the EP catheter 120. The EP catheter 120 may comprise a flexible elongate member configured to be positioned within the cryoballoon catheter 130. In some embodiments, the cryoballoon catheter 130 may be introduced into the body cavity first and the EP catheter 120 may be advanced distally within the cryoballoon catheter 130 until the distal portion 122 of the EP catheter 120 protrudes out the distal end of the cryoballoon catheter 130 at a region of interest (ROI) such as e.g., an ablation site.

The distal portion 122 of the EP catheter may comprise a plurality of electrodes positioned on the elongate tip member. In some embodiments, the EP catheter comprises between 8 and 10 electrodes. However, the EP catheter can include other numbers of electrodes, including 2, 4, 6, 14, 20, 30, 60, or any other suitable number of electrodes, both larger and smaller. The elongate tip member may be configured to be positioned distally of the cryoballoon, and may be biased, shaped, or otherwise structurally configured to assume a shape, such as a circular shape, in which the electrodes are spaced from one another about one or more planes. For example, the EP catheter can be a spiral mapping catheter (SMC) in which electrodes are distributed along an elongate tip member in a spiral configuration. Alternatively the EP catheter may be a lasso catheter in which electrodes distributed along an elongate tip member may be configured in a lasso shape. In some embodiments, commercially-available EP catheters can be used with the system 100, including the Achieve™ and Achieve Advance™ Mapping catheters manufactured by Medtronic™. The EP catheter can be designed for use with the Arctic Front™ Family of Cardiac Cryoablation Catheters and/or the FlexCath™ Advance Steerable Sheath, manufactured by Medtronic™. In some embodiments, the cryoballoon 132 comprises a plurality of electrodes positioned on an exterior surface of the cryoballoon 132 and configured to obtain data used to determine occlusion at an ablation site. Further details regarding EP catheters and assemblies can be found in, for example, U.S. Patent No. 6,002,955, titled “Stabilized Electrophysiology Catheter and Method for Use,” the entirety of which is hereby incorporated by reference.

The EP cryoablation system 100 further comprises a plurality of body patch electrodes 140 and a reference patch electrode 142 communicatively coupled to a patch electrode interface 116, which is in communication with the mapping and guidance system 114. For example, the patch electrodes 140 and the reference electrode 142 may be coupled to the patch electrode interface 116 via electrical cables. Some or all of the communicative coupling may be realized via wireless connections and in such case the necessary hardware and software components as known in the art are included.

In the embodiment shown in Fig. 2, the system 100 comprises six external body patch electrodes 140 and one reference electrode 142. However, in some embodiments, the system 100 comprises fewer or more body patch electrodes 140 than are shown in Fig. 2, including 1, 2, 4, 8, 19, 12, 20, or any other suitable number of body patch electrodes, both lager and smaller. Further, in some embodiments, the system 100 may include more than one reference electrode 142, including 2, 4, 5, or any other suitable number of reference patch electrodes. The patch electrodes 140 and reference electrode 142 may be used e.g. by the mapping and guidance system 114, for or in generating images, maps or models of a body cavity (anatomical cavity), such as the chambers of the heart, body lumens that provide access to the body cavity, and other features identified to be electrically isolated from the body cavity (e.g., the pulmonary vein). For example, the patch electrodes 140 may be used in pairs to generate electrical fields in different directions and at different frequencies within a body cavity of a patient. The patch electrodes 140 may be controlled by the mapping and guidance system 114 and/or the patch electrode interface 116 to generate the electrical fields.

Mapping data (imaging data) is obtained by the electrodes of the EP catheter 120 by detecting distortions in the electrical fields generated by the patches. For example, while generating crossing electrical fields in the anatomical cavity by injecting alternating currents with the external electrode patches at mutually different frequencies, the EP catheter electrodes may be used to sense and record voltages representative of the distortions at different locations within the anatomical cavity by visiting such locations through moving around of the catheter in the cavity. The voltage cloud data so obtained may then be transformed into a location (positional coordinate) cloud data by, during the transformation, use constraints relating voltages to distances such as for example the known distances between catheter electrodes and the sensed voltages at any one time. From the coordinate cloud data a cavity wall may then be represented by constructing a mesh that may represent the image map or model of the body volume. For example, a point cloud can be converted into a polygon mesh or triangular mesh model (or other surface model) using a surface reconstruction approach. A variety of suitable approaches is discussed in Berger, Matthew, et al. "A survey of surface reconstruction from point clouds." Computer Graphics Forum. Vol. 36. No. 1. 2017.

The mapping data may then be used to generate the image, map or model of the body volume, such as a cavity of the heart. The mapping and guidance system 114 may thereto generate image data representative of the image, map or model and output the data to e.g. a display 118 (display device communicatively coupled to the system 114) through a suitable output (not explicitly shown) such that the display may visualize the generated image, map or model of the cavity for a user such as the patient or physician to observe.

Further, the mapping and guidance system 114 may be configured to determine a location of the EP catheter within the body cavity and generate location data representative of the location. Again, as described for the mapping herein above, the electrodes of the EP catheter may sense the generated electric field within the cavity and form that their location in the cavity, and therewith with respect to the generated images, maps or models, may be determined. For example, the data may represent a visualization that indicates a position of the EP catheter 120 within the image, map or model. The system 114 may be configured to generate an overlay of the location data over the image data and output the combined data the (or another) display 118 for the user to observe the position of the EP catheter 120 within the image, map or model. For example, based on the mapping data, the mapping and guidance system 114 may be configured to determine the position of the electrodes of the EP catheter, and output a visualization indicating the position of each of the electrodes on the map (see Fig. 5, indicator 312).

Further, based on the determined position of the electrodes of the EP catheter, the mapping and guidance system 114 may be configured to determine or estimate a location of the cryoballoon 132 within the body cavity. For example, in some embodiments, the EP catheter 120 is first advanced to a ROI, such as the ostium of a PV, and anchored into place. The cryoballoon catheter 130 may then be advanced over the EP catheter to the region of interest. The balloon may be in deflated form during such advancement or at least partially in inflated form for example when nearing the ROI. If the distance and position of the cryoballoon 132 or part thereof (such as e.g. the distal end or portion) relative to one or more of the electrodes of the EP catheter 120 are fixed and known, the mapping and guidance system 114 may be configured to identify or infer a location of the cryoballoon 132 by a translation of the coordinates of the EP catheter 120 using such fixed and knows distance and position. For example, the distance between the cryoballoon 132 and the one or more electrodes of the EP catheter 120 may be added/subtracted to the coordinates of the one or more electrodes of the EP catheter to identify the location of the cryoballoon 132. Accordingly, the mapping and guidance system 114 may be configured to generate the location data as described herein before and output a visualization of the position of the cryoballoon 132 with respect to the image, map or model of the body cavity.

A more detailed explanation of electroanatomical mapping (dielectric mapping) and the use of body patch electrodes and catheter electrodes to image, map or model body volumes and cavities and visualize the locations of EP catheters within such images, maps and models can be found in, for example, U.S. Patent No. 10,278,616, titled “Systems and Methods for Tracking an Intrabody Catheter,” filed May 12, 2015, and U.S. Patent No. 5,983,126, titled “Catheter Location System and Method,” filed August 1, 1997, WO2018/130974, titled “Systems and methods for reconstruction of intra-body electrical readings to anatomical structure, and WO2019/034944, titled “reconstruction of an anatomical structure from intrabody measurements”: the entireties of which are hereby incorporated by reference.

In the diagram shown in Fig. 2, the EP catheter interface 112, mapping and guidance system 114, and patch electrode interface 116 are illustrated as separate components. However, in some embodiments, the interfaces 112, 116 and the mapping and guidance system 114 may be components of a single console or computing device with a single housing. In other embodiments, the interfaces 112, 116 and the mapping and guidance system 114 may comprise separate hardware components (e.g., with separate housings) communicatively coupled to one another by electrical cables, wireless communication devices, fiber optics, or any other suitable means of communication. Further, in some embodiments, the EP catheter interface 112 may also function as an interface for the cryoballoon catheter 130 to control inflation of the cryoballoon 132, cooling/heating of the cryoballoon 132, etc. In other embodiments, the cryoballoon catheter 130 is controlled by a separate interface or control system, such as a console. The mapping and guidance system 114 is coupled to a display device 118, which may be configured to provide visualizations of a cryoablation procedure to a physician. For example, the mapping and guidance system 114 may be configured to generate EP images of the body cavity, visualizations of the propagation of EP waves across the tissue of the body cavity, indications of occlusion by the cryoballoon at an ablation site, or any other suitable visualization. These visualizations may then be output by the mapping and guidance system 114 to the display device 118.

Fig. 3 is a schematic diagram of a processor circuit 150, according to embodiments of the present disclosure. The processor circuit 150 may be implemented in the mapping and guidance system 114, the EP catheter interface 112, the patch electrode interface 116, and/or the display device 118. The processor circuit 150 can carry out one or more steps described herein.

As shown, the processor circuit 150 may include a processor 160, a memory 164, and a communication module 168. There may be more than one communication module, for example one for communicating with interface 112, another for communicating with interface 116 and one for communicating with a user interface such as display, mouse, keyboard or pedal. These elements may be in direct or indirect communication with each other, for example via one or more buses.

The communication module 168 can include any electronic circuitry and/or logic circuitry and/or software to facilitate direct or indirect communication of data between the processor circuit 150, the mapping and guidance system 114, the EP catheter 120, the cryoballoon catheter 130, and/or the display 118. In that regard, the communication module 168 can be an input/output (I/O) device. In some instances, the communication module 168 facilitates direct or indirect communication between various elements of the processor circuit 150 and/or the system 100 (Fig. 2).

The processor circuit and/or appropriate communications modules include the required inputs and outputs (separate or combined as I/O) (e.g. input and output connectors) for communicating with parts of the system 100 that need to be connected to the processor circuit. For example, there may be an input/output for connecting to the electrode patches and EP catheter electrodes if the processor circuit is implemented in the system 114 and the interfaces 112 and 116. Alternatively, if the processor circuit is not implemented in one or more interfaces 112 and 116, then the processor circuit includes the appropriate inputs and outputs for connecting to the interfaces 112 and 116 to be able to control the patch and catheter electrodes. The processor circuit also includes an input/output for connecting to the user interfaces as described herein before.

The processor 160 may include a central processing unit (CPU), a digital signal processor (DSP), an ASIC, a controller, an FPGA, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. The processor 160 may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The memory 164 may include a cache memory (e.g., a cache memory of the processor 160), random access memory (RAM), magnetoresistive RAM (MRAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, solid state memory device, hard disk drives, other forms of volatile and non volatile memory, or a combination of different types of memory. In an embodiment, the memory 164 includes a non-transitory computer-readable medium. The non-transitory computer-readable medium may store instructions. For example, the memory 164, or non- transitory computer-readable medium may have program code recorded thereon, the program code including instructions for causing the processor circuit 150, or one or more components of the processor circuit 150 such as the processor 160, to control the processor circuit, an apparatus, the system 100 or the system 114, to perform the operations described herein. For example, the processor circuit 150 can execute one or more operations of the methods 200, 500, 700. Instructions 166 may also be referred to as code or program code. The terms “instructions” and “code” should be interpreted broadly to include any type of computer- readable statement(s). For example, the terms “instructions” and “code” may refer to one or more programs, routines, sub-routines, functions, procedures, etc. “Instructions” and “code” may include a single computer-readable statement or many computer-readable statements. The memory 164, with the code recorded thereon, may be referred to as a computer program product.

In some embodiments, the processor circuit 150 may further comprise an electrical signal generator and/or an electrical signal measurer (not separately shown in Fig. 2 or 3) configured to control the electrodes of the EP catheter to emit and/or detect and/or process (provide, sense, filter, transform and/or digitize) electrical signals, including voltages, impedances, and currents. Such signal processors may have ADC’s, DAC’s and other electronic circuitry to perform the required functions. The signal processor may be capable of digitizing any data to be received or obtained by (via an appropriate data input) and processed by the processor 160 described herein before.

In other embodiments, the electrical signal generator and/or electrical signal measurer and/or electrical signal processor is separate from the processor circuit as described herein before. It may be part of the imaging and mapping system. The processing circuit may then take the form of a computer or workstation for controlling several elements of subsystems of the system 100 and possibly system 114.

The mapping and guidance system 114 may take the form of one single integrated device for example having the processing circuit, signal generator, signal measurer and signal processor within one housing and having the appropriate inputs and outputs for the communication connections needed to connect parts of the system 100 as described herein before. In other embodiments, the system 114 may comprise separate components that are interconnectable such as to perform the required described functions. For example, the system may comprise the signal generator and/or signal measurer and/or signal processor as one or more separate apparatuses that are connectable to a processor circuit in the form of e.g. a computer or workstation. In some embodiments, the processor circuit and/or the imaging and mapping system has a remotely distributed form with the distributed elements interconnected or interconnectable via a data transfer network such as LAN or WLAN. For example a signal generator, signal measurer and signal processor interfaces 112 and 116 catheters and electrode patches may be located in an operating room while a workstation including at least part of or all of the processing circuit is located outside such room the remotely separated parts having the appropriate hardware and software to enable the communication over the network so as to enable partly control or data acquisition by the workstation.

Fig. 4 is a flowchart illustrating a method 200 for use in performing a balloon therapy procedure, such as balloon ablation or balloon angioplasty, according to some embodiments of the present disclosure. It will be understood that parts of (e.g. navigating a catheter may be done by a physician if not automated by a robot) or entire steps of some or all of the steps of the method 200 may be performed using one or more components of the system 100 shown in Fig. 2, including the EP catheter 120, the cryoballoon catheter 130, the mapping and guidance system 114, and/or the patch electrodes 140, 142.

In step 202, an EP catheter is navigated to an anatomical cavity, such as a chamber of the heart or a diseased blood vessel. In some embodiments, navigating the EP catheter to the anatomical cavity is performed using EP imaging techniques to image the full anatomical cavity. For example, in some embodiments, a guidewire with electrodes, a sheath with electrodes, and/or the EP catheter is inserted into an entry site, such as the femoral vein in the patient’s leg and navigated to the anatomical cavity (e.g., left atrium) while the access route is imaged, using e.g. the system 100, to guide the placement of the guidewire, sheath, or catheter at the right atrium. In some embodiments, the EP catheter is introduced into the left atrium using a transseptal procedure. In some embodiments, the transseptal procedure may involve the use of a transseptal needle or RF needle to penetrate the transseptal wall to introduce the catheter or sheath into the left atrium.

In step 204, the anatomical cavity is mapped or imaged e.g. using the system 100. As e.g. described herein before the system records the relevant mapping data while moving the EP catheter within the anatomical cavity. For example, for a balloon angioplasty procedure, the vessel walls may be imaged by a guidewire carrying two or more electrodes along a length of the vessel, including a diseased or stenosed portion of the vessel. For balloon ablation, an atrial wall, pulmonary vein (PV) ostia, left atrial appendage (LAA), LAA ridge, mitral valve, or other features of the left atrium may be imaged using the EP catheter 120. Anatomical variations can be detected without the use of contrast media. Accordingly, some or all of the anatomical landmarks relevant to performing the ablation procedure can be mapped using the EP catheter and output to a display to guide preplanning of the ablation process and deployment of the balloon. In some embodiments, the left atrium, right atrium, coronary sinus ostium, septal wall, fossa ovalis, or other features may be imaged using the EP catheter 120.

In some embodiments, mapping of the anatomical cavity is performed in step 204 using the electrodes of the EP catheter to detect distortions in electrical fields generated by external patch electrodes placed on the body of a patient. The distortions in the electrical fields may be caused by the shape and structure of the tissue, and thus the detected distortions can be used to generate a map of the left atrium. In some embodiments, each EP catheter electrode is configured to emit an electrical signal at a particular frequency. Further, all of the EP catheter electrodes may be configured to detect the electrical signals emitted by the other EP catheter electrodes at the other frequencies, in addition to the electrical signal emitted by the electrode. For example, a first electrode may be configured to emit a first electrical signal at a first frequency, and a second electrode may be configured to emit a second electrical signal at a second frequency. In an exemplary embodiment, the first electrode is used to detect the first electrical signal at the first frequency, and the second electrical signal is used to detect the second electrical signal at the second frequency. However, in other embodiments, the first electrode may detect the second electrical signal at the second frequency in addition to its own first electrical signal at the first frequency. Similarly, the second electrode may detect the first electrical signal at the first frequency in addition to its own second electrical signal at the second frequency.

In some embodiments, mapping the anatomical cavity comprises guiding an EP catheter to a plurality of 3D locations, or voxels, within the anatomical cavity, and obtaining voltage measurements at each location with the plurality of electrodes to create a voltage field map, which can then be used by the processor circuit to compute geometrical measurements (e.g., distance) associated with the tissue structures within the anatomical cavity. Further, in some aspects, the processor circuit may generate, based on the voltage measurements, a conductance map showing a conductance field of the anatomical cavity. A conductance field in some embodiments may represent an electrical field within the cavity.

With reference to step 204 of the method 200, Fig. 5 shows a user interface 300 that includes three-dimensional images or views of the left atrium. For example, a first atrial view 310 is a perspective three-dimensional view of the internal structure of the left atrium 20 and pulmonary veins 10. The view 310 includes an EP catheter indicator 312 that shows a location and/or orientation of the electrodes at the distal portion or an EP catheter. In some embodiments, the view 310 can be manipulated (e.g., oriented, re-sized, moved) by a user to provide different views or angles of the left atrium. A second atrial view 320 may comprise a flattened panoramic view of the left atrium 20. For example, the second view 320 may be generated by translating, stretching, distorting, or otherwise modifying the first view 310. The second view 320 shows the ostia of the pulmonary veins in a 3D flattened configuration, which may be advantageous for planning and performing ablation procedures, particularly in order to carry out the full ablation procedure without repeated manipulation and frequent changes in projection of the 3D reconstructed image. The views 310, 320 can be used in step 206 to locate the desired treatment site, and to guide placement of a therapeutic balloon at the treatment sites, and/or otherwise plan the treatment procedure. In some embodiments, one or more locations of the EP catheter are recorded during the mapping procedure described with respect to step 204. For example, an initial location of the EP catheter, or any intermediate location of the EP catheter, may be recorded and displayed on the user interface 300 described above.

In step 208, the processor circuit controls a plurality of electrodes to emit an electromagnetic (EM) field within the anatomical cavity. In some embodiments, the electrodes used to emit the EM field include a plurality of body patch electrodes, a plurality of catheter-mounted electrodes, and/or any other suitable type of electrode. Further, it will be understood that the EM field may include multiple EM fields having different parameters or properties, such as different frequencies. In an exemplary embodiment, the electrodes of the EP catheter shown in Fig. 1 may be used to emit the EM field. In some embodiments, a different plurality of catheter-mounted electrodes may be used, including electrodes of a coronary sinus (CS) catheter. In that regard, in some instances, a CS catheter is inserted into an anatomical structure near the anatomical cavity imaged in step 204 to monitor one or more aspects of a balloon ablation procedure. For example, a cryoballoon ablation procedure may involve a risk of neural damage to nerves near the ablation site, such as a phrenic nerve. The CS catheter may include a plurality of electrodes at a distal end of the CS catheter used to obtain EP data of tissue structures near the phrenic nerve to monitor an extent of the cryoballoon ablation. Accordingly, because the CS catheter may already be placed near the anatomical cavity in which the EP catheter and the balloon are positioned, the electrodes of the CS catheter may also be used to emit the EM field of step 208.

In step 210, the processor circuit controls a plurality of electrodes to detect the EM field emitted in step 208. In some embodiments, the electrodes used to detect the EM field include a plurality of body patch electrodes, a plurality of catheter-mounted electrodes, and/or any other suitable type of electrode. In some embodiments, the same plurality of electrodes is used to detect and emit the EM field in steps 208 and 210. For example, in some embodiments, the electrodes of the EP catheter are used to both emit and detect the electrical field, as explained further below. In some embodiments, a first plurality or set of electrodes is used to emit the EM field, and a different, second plurality or set of electrodes is used to detect the EM field. For example, in some embodiments, a plurality of external body patch electrodes is used to emit one or more EM fields within the anatomical cavity, and a plurality of catheter-mounted electrodes (e.g., EP catheter electrodes and/or CS catheter electrodes) is used to detect the EM fields. In some embodiments, a combination of external body patch electrodes and/or catheter-mounted electrodes is used to emit the EM fields, and the same or a different combination of external body patch electrodes and/or catheter-mounted electrodes is used to detect the EM fields. In some embodiments, the processor circuit is configured to control the electrodes to detect the EM field to determine a position of a catheter within the anatomical cavity. In some embodiments, the processor circuit is configured to control the electrodes to detect the EM field to detect or identify a disturbance or change in the EM field that is caused by an inflated balloon, for example. In some embodiments, the processor circuit is configured to control the electrodes to detect the EM field to detect a fault condition in which one or more catheter-mounted electrodes are drawn into a sheath, such as a sheath of a balloon ablation catheter (e.g. electrodes of EP catheter 120 and sheath 136 described in relation to Fig. 1), as described further below. The control of the processor circuit may preferably be under guidance or control of the processor circuit.

In a variant of the method 200, the steps 208 and 210 are replaced with or comprise a step in which the processor circuit receives or obtains image data or mapping data representative of an image, map or model of the anatomical cavity. In such case the method and the steps 208 and 201 step may not include the control of electrodes to generate the mapping data or the generation of the image data. The image data

In step 212, the processor circuit receives one or more geometrical parameters associated with the balloon. In some aspects, step 212 may involve retrieving or recalling the one or more geometrical parameters from a memory of the processor circuit or from a a memory not part of the processor circuit via an input of the processor circuit. The geometrical parameters may include or represent a set of assumptions of known geometrical conditions of the balloon for example when in deflated or inflated state, including that the electrodes used to emit and/or detect the EM field are positioned distally of the balloon, that a final location of the inflated balloon is in a plane of a previously-imaged pulmonary vein ostium, a shape of the inflated balloon, that the balloon is a continuation of the catheter sheath, a volume of the inflated balloon, a size of the inflated balloon, a dimension of the inflated balloon, and/or any other suitable geometrical parameter associated with the balloon. The one or more geometrical parameters may pertain to at least a section of the balloon for example a most distal section closest to the EP catheter electrodes during the procedure.

In step 214, the processor circuit determines or computes a location of the balloon within the anatomical cavity based on the one or more geometric parameter and the detected EM field.

For example, in some embodiments, detecting the EM field may include detecting or measuring a conductance field, and reconstructing a conductance map. A detected disturbance or change in the conductance field upon any manipulation of the balloon (e.g. one or more of inflation, deflation movement (e.g. along the EP catheter)) may be used by the processor circuit to determine an estimated or approximated location of the balloon. Further, the geometrical parameter(s) may be used to improve the accuracy and/or reliability of the estimated or approximated location. An embodiment using this approach is described below with respect to the method 500 of Fig. 7. In another approach, the processor circuit is configured to determine the location of the balloon based on a fault condition detected during step 210 in which one or more catheter-mounted electrodes are retracted into a sheath or catheter body. In that case, the processor circuit may determine where the fault condition occurred within the anatomical cavity, and infer or compute the location using the location of the fault condition and a geometric parameter associated with the balloon, such as the location of the inflated balloon relative to the distal tip of the sheath. An embodiment using this approach is described below with respect to the method 700 of Fig. 9.

In step 216, the processor circuit outputs a signal representative of a visualization of the location within the anatomical cavity. In some aspects, outputting the visualization may include generating the signal representative of the visualization based on the determined location, and outputting the signal to a display in communication with the processor circuit. The signal may comprise any suitable type of communication, such as an electrical signal (e.g., digital electrical signal) representative of image data. For example, the electrical signal may be in a format suitable for display by a display device (e.g., computer monitor, television screen, mobile computing device display, etc.).

In some embodiments, step 216 includes outputting a view or map of the anatomical cavity as performed in step 204, and including the visualization of the location and/or shape of the inflated balloon with respect to the anatomical map of the cavity. For example, the visualization may be overlaid on an anatomical map generated as described above with respect to Fig. 2. In that regard, Fig. 6 depicts a graphical user interface 400 in which the visualization of the location, shape, and size of the balloon 414 is shown within the map of the anatomical cavity. In particular, the map 410 of Fig. 6 is a map of the left atrium, and an indicator of the inflated balloon 414 positioned within the PV ostium. The map 410 may be generated using a plurality of electrodes mounted on a circular catheter or guidewire to detect distortions in electrical fields caused by the tissues of the anatomical structures as described above. The visualization includes an indicator of the inflated balloon 414, an indicator of the balloon catheter 416, and an indicator of the EP electrodes 412. The location of the EP catheter may be determined by detecting changes in an inhomogeneous electrical field created by the atrial wall and other tissues, as described above, while the visualizations of the inflated balloon 414 and/or the catheter bodies are based at least partially on the geometric parameters as in step 214. In an exemplary embodiment, the graphical user interface 400 provides a live, or real-time view of the inflated balloon, such that a current location of the balloon is shown and updated in real time (in accordance with hardware and processing limitations) as the balloon moves around the anatomical cavity.

In some instances, a shape of the visualization 414 of the inflated balloon may be updated in the graphical user interface to represent changes to the shape of the balloon caused by the tissue structures during the treatment procedure. For example, in some embodiments, when the processor circuit determines that the inflated balloon is in contact with and pressing against the PV ostium, the processor circuit may modify the visualization 414 to show a distortion to the shape as the balloon is compressed by the ostium. In that regard, one or more portions of the visualization 414 of the balloon, such as the portion of the balloon in contact with the ostium, may appear somewhat flat in comparison with the spherical visualization shown in Fig. 6. Further, in some embodiments, one or more aspects of the visualization 414 of the inflated balloon may be updated or modified by the processor circuit in response to the treatment procedure (e.g., ablation, radiation) commencing. For example, a color, brightness, or other visual aspect may be updated to show that the treatment procedure has begun.

In some embodiments, a therapeutic balloon may comprise a material having very low conductivity. In some instances, the conductivity of the balloon may be orders of magnitude lower than the surrounding blood or myocardium. Accordingly, a location of the therapeutic balloon can be determined by measuring or detecting a change in a conductance field within the cavity by one or more electrodes (e.g., EP catheter electrodes, CS catheter electrodes, body patch electrodes) upon manipulation of the balloon in the cavity. Fig. 7 is a flow diagram illustrating a method 500 for visualizing a balloon in a guided balloon ablation procedure, according to aspects of the present disclosure. It will be understood that part of some or all of the steps of the method 500 may be performed using one or more components of the system 100 shown in Fig. 2, including the EP catheter 120, the cryoballoon catheter 130, the mapping and guidance system 114, and/or the patch electrodes 140, 142. Further, other components may also be used, such as a CS catheter carrying a plurality of catheter- mounted electrodes. Further, it will be understood that the method 500 may correspond to one or more steps of the method 200 described with respect to Fig. 4, such as emitting an EM field within an anatomical cavity in step 208, detecting the EM field in step 210, receiving a geometrical parameter in step 212, determining the location of the balloon in step 214, and outputting the visualization of the balloon in step 216.

In step 502, a processor circuit, which may form part of the mapping and guidance system 114, controls a plurality of electrodes to detect an EM field at a first time. The balloon is not yet inflated at the first time. In an exemplary embodiment, detecting the EM field comprises controlling a plurality of catheter-mounted electrodes (e.g., of an EP catheter, CS catheter, etc.) to obtain electrical measurements, such as voltage measurements, impedance measurements, conductance measurements, etc. For example, an EP catheter may be advanced into the left atrium near the ostium or into the pulmonary vein near the ostium to detect the EM field. As described further below, the positioning of the EP catheter relative to the anatomical features of the patient may be used as a geometrical parameter to identify the location of the balloon. In some embodiments, the same electrodes that are controlled to detect the EM field at the first time are the same electrodes that are used to emit the EM field at the first time. For example, a plurality of catheter-mounted electrodes of an EP catheter may be controlled according to a natives matrix to emit and detect the EM field.

In step 504, the balloon is inflated after the plurality of electrodes measures the EM field in step 502. In some embodiments, the processor circuit is configured to control the inflation or deployment of the ablation balloon and/or the injection of the coolant. In some embodiments, the processor circuit controls the inflation or deployment of the balloon based on a user input received using a user interface device. In some embodiments, a separate control system or processor circuit is used to control the deployment of the balloon. In some embodiments, a separate balloon control system transmits to the processor circuit of the guidance system a signal indicating that the balloon has been inflated. In some embodiments, the balloon is inflated manually by an operator or physician.

In step 506, the processor circuit 150 controls the plurality of electrodes to detect the EM field at a second time, after the first time and after inflating the balloon. In some embodiments, the same electrodes that are controlled to detect the EM field at the second time are the same electrodes that are used to emit the EM field at the second time. For example, a plurality of catheter-mounted electrodes of an EP catheter may be controlled according to a natives matrix to emit and detect the EM field. As described above, in some embodiments, step 506 comprises obtaining voltage measurements using the plurality of electrodes. Because the balloon comprises a nonconductive or dielectric material, the presence of the inflated balloon within the EM field may cause a disturbance or modification to the EM field. Thus, the EM measurements obtained by the electrodes during steps 502 and 506 can be used to identify differences in the EM field (e.g., a conductance field), as for example further described below.

Fig. 8 is a graphical view of a natives matrix 600 representing the signals analyzed by the processor circuit to detect the presence of an inflated balloon, according to one embodiment of the present disclosure. In one aspect, the natives matrix defines combinations of a receiving electrode of a plurality of electrodes and an emitting frequency used to measure an EM field. The voltages of each block are defined as V , where i represents which electrode is receiving, andj represents the emitting electrode, or the frequency at which the i ^th electrode is measuring the signal. Thus, V3 _, 5, for example, is the voltage measured by electrode number 3 at the frequency of electrode number 5. In the table of Fig. 8, the voltages, or electrical signals, that are used to detect the presence of the inflated balloon are not shaded, and the voltages that are not used are shaded. Thus, the voltages that are used comprise a diagonal of the matrix 600, which are the electrical signals that are generated and detected using the same electrodes. For example, the signal Vi _, 1, which is the signal generated and received by the first electrode, is used to detect the presence or location of the inflated balloon, while Vi _, 2, may not be used. However, in other embodiments, any suitable combination of voltages is used. For example, some or all of the non-native voltages are used to detect the balloon. For example, in some embodiments, a mirror-image diagonal of voltages is used in addition to the diagonal in the matrix 600 of Fig. 8. Further, in some embodiments, current, conductance, and/or electrical impedance are used instead of, or in addition to voltage. For example, in some embodiments, the system may be configured to compare impedance measurements to detect the location of the balloon using a given electrode. Further, although the matrix 600 is an 8-by-8 matrix corresponding to an eight- electrode EP catheter, the matrix 600 of electrical signals may include any suitable number of signals, both larger or smaller. For example, as described above, in some embodiments, 2, 4, 6, 8, 10, 12, 15, 20, 30, 60, or any other suitable number of electrodes may be used to detect the presence or location of the balloon. Accordingly, in some embodiments, the matrix 600 may include a 2-by-2 matrix, a 4-by-4 matrix, a lO-by-10 matrix, a 20-by-20 matrix, a 60-by- 60 matrix, or any other suitable matrix.

Referring again to Fig. 7, in step 508, the processor circuit computes or generates a first conductance map based on the first EM detected at the first time. In step 510, the processor circuit computes or generates a second conductance map based on the second EM detected at the second time. In some embodiments, the conductance maps are computed based on voltage measurements obtained by catheter-mounted electrodes (e.g., EP catheter, CS catheter). In step 512, the processor circuit compares the first conductance map to the second conductance map to determine a change in a conductance field of the anatomical cavity between the first time and the second time, which represents the changes to the conductance field caused by the presence of the inflated balloon. In some embodiments, step 512 includes subtracting one conductance map from the other conductance map. For example, the first conductance map may be subtracted or deducted from the second conductance map to determine the change in the electric field. In that regard, the conductance map may comprise a matrix of conductance values for a plurality of voxels in a conductance field. Subtracting one conductance field from the other may comprise subtracting values from one conductance field from the spatially-corresponding values from the other conductance field.

In step 514, the processor circuit determines the location of the inflated balloon based on the detected change in the conductance field and the geometric parameter.

In some embodiments, the detected change in the conductance field provides an estimate or approximation for the location of the balloon, and the geometric parameter (e.g., distal position of EP catheter (e.g. one or more of its electrodes) relative to the inflated balloon, shape of the inflated balloon, size of the inflated balloon, balloon mechanics, final pose of the balloon relative to the tissue structures of the anatomical cavity, etc.) are used to improve the precision and/or accuracy of the estimated location. In other embodiments, the detected change in the conductance field and the geometric parameter are used as inputs to a relationship to compute the location of the inflated balloon.

In alternative embodiments to those that make use of conductance maps, the conductance map is replaced by a voltage map, dielectric map or impedance map or any one representing such mappings. In fact, any parameter mapping obtainable form measurements form the EP catheter and representative of an EM field within the anatomical cavity may be used at the first and second times to determine differences of mapping between the first time and the second time in order to determine a balloon location.

In the embodiment above, step 504 included inflation of the balloon. Alternatively, or additionally other balloon manipulations may be done to generate mapping differences between the first time and second time from which a balloon location may be determined. For example, such manipulations may include one or more of: balloon deflation or translation such as e.g. translation along the EP catheter. However other translations may be used too.

Once the location of the balloon has been determined, the location of the balloon can be visualized on a display to guide placement of the ablation balloon at the ablation site. As described above, in an exemplary embodiment, the processor circuit is configured to update the visualization of the location of the balloon in real time to provide a live view of the balloon within the anatomical cavity. To this end the processor may be configured to repeat steps 502 to 514 one or more times while the inflation action of step 504 is now replaced by a movement action of the balloon due to the placement during the procedure. In that way a new location may be determined after a particular movement of the balloon.

In the aforementioned embodiments, it has been explained how the electrodes may be controlled to detect the desired EM fields. In a variation of the embodiments the processor circuit is configured to receive or cause it to receive detected EM field data representative of a location of the balloon within an anatomical cavity. For example, such EM field data may be the ones as detected as described herein before by controlling of the electrodes. According to another embodiment of the present disclosure, a fault condition detection scheme can be used, in addition to one or more geometrical parameters associated with the balloon, to detect the location of the balloon. Fig. 9 is a flow diagram illustrating a method 700 for determining and visualizing a location of an ablation balloon within an anatomical cavity, according to embodiments of the present disclosure. It will be understood that part or all of some or all of the steps of the method 700 may be performed using one or more components of the system 100 shown in Fig. 2, including the EP catheter 120, the cryoballoon catheter 130, the mapping and guidance system 114, and/or the patch electrodes 140, 142. Further, other components may also be used, such as a CS catheter carrying a plurality of catheter-mounted electrodes. Further, it will be understood that the method 700 may correspond to one or more steps of the method 200 described with respect to Fig. 4, such as emitting an EM field within an anatomical cavity in step 208, detecting the EM field in step 210, receiving a geometrical parameter in step 212, determining the location of the balloon in step 214, and outputting the visualization of the balloon in step 216.

In step 702, the processor circuit controls a plurality of catheter-mounted electrodes to detect a position of the electrodes relative to the features of the anatomical cavity. In an exemplary embodiment, the processor circuit controls an EP catheter comprising a plurality of electrodes at a distal end of the EP catheter. The EP catheter is positioned at least partially within a lumen of a balloon ablation catheter or sheath, (e.g. catheter 120 within sheath 136 as shown in Fig. 1, for example). Further, the distal portion of the EP catheter having the catheter-mounted electrodes is positioned at a predetermined location near the desired ablation site (e.g., within PV or PV ostium). As described herein before, the processor circuit may be configured to detect distortions in EM fields generated by external patch electrodes placed on the body of a patient. The distortions in the EM fields may be caused by the shape and structure of the tissue, and thus the detected distortions in the EM fields can be used to generate a map of the anatomical cavity and/or to determine a position of the EP catheter relative to the tissue structures of the anatomical cavity. In some embodiments, the processor circuit is configured to obtain a continuous stream of position data based on voltage measurements obtained by the catheter-mounted electrodes. In that regard, the processor circuit may be configured to detect several EP catheter (electrode) positions each second, in some embodiments. Further, in some embodiments, a different plurality of electrodes may be used to detect the position in step 702, such as a plurality of CS catheter electrodes.

In step 704, the EP catheter is retracted in a sheath (e.g., sheath 136, Fig. 1), such as the sheath of the balloon catheter. In some embodiments, the EP catheter is manually retracted by the physician. In other embodiments, the processor circuit controls an actuator apparatus or interface device to retract the EP catheter into the sheath. As the EP catheter is retracted into the sheath, the electrodes continue obtaining electrical data or voltage signals while the electrodes of the EP catheter become covered or occluded by the sheath. This results in detectable changes to the voltage measurements obtained by the EP catheter electrodes. Such changes, and optionally the associated instances, may be termed fault conditions for an electrode or set of electrodes.

In step 706, the processor circuit detects, based on the changes in the electrical measurements, a fault condition for each of the electrodes, as well as the location of the EP catheter when the fault condition occurred. For example, the processor circuit may employ an outlier detection scheme to detect the fault condition. In some embodiments, the fault condition is detected only when all electrodes are retracted into the sheath. In other embodiments a fault condition is detected for one or more (subset) electrodes, or for each electrode individually. Since the location of the EP catheter electrode is known at the moment of a fault condition, the location of the cause of the fault condition (in this case the tip of the sheath the EP catheter is being retracted into) is also known by detection of the fault condition.

In some embodiments, the processor circuit is configured to output a graphical representation of the faulted electrodes to the display to indicate to the physician how many and which of the electrodes have been retracted into the sheath. In some embodiments the processor circuit is configured to output a graphical representation of the non-faulted electrodes to the display. The graphical representation may include a model of a section of the catheter having the electrodes, where the model is based on the actual known dimensions (e.g. diameter of the catheter and the distance between electrodes on it). The model may be scaled to any anatomical cavity model that it is overlayed with and that is also output to the display.

Thus, with such detection of fault condition a location of the distal tip of the sheath 136 can be or has been determined, for example a location of this tip with respect to the anatomical cavity (and any mapping of it) can now be or is now known.

In step 708, the EP catheter is then advanced out of the sheath such that the detected fault condition is no longer applicable to the electrodes at the distal end of the EP catheter. Preferably it is advanced out of the sheath so that the most proximal electrode of the EP catheter is only just exposed (kept very near the sheath opening) to again just provide a valid voltage reading which reading is suitable to determine the electrode location. In other embodiments, the EP catheter is advanced out of the sheath until a less proximal electrode is just exposed with some of the electrodes thus still inside the sheath. Any exposed electrodes (outside of the sheath) may be located by the system and such electrodes may be used to infer the location of the sheath tip. Such electrodes which have a known relative relationship to the balloon catheter may be called tracking electrodes. For example, the electrode that has only just been exposed is near the tip and may be assumed to reflect the location of the tip of the sheath. Alternatively, or additionally, using the known (e.g. from a lookup table in a memory accessible by the processor circuit) interelectrode distances on the EP catheter, other electrodes than the one nearest the sheath tip may also be used to infer or determine the sheath tip position. The distance between such tracking electrode and the sheath tip may however also require determination of the shape of the segment of the EP catheter tip between the electrode nearest to the sheath tip and the tracking electrode used for locating the tip as otherwise an error in the distance calculation may be made. Determination of such segmental shape will be further elucidated herein below.

In step 710, the balloon is deployed and advanced out of the sheath 136 to the desired treatment location (e.g., PV ostium).

In step 712, the processor circuit determines the location of the balloon based on the location associated with the detected fault condition and the geometric parameter associated with the balloon. With reference to Fig. 1, the processor circuit may be able to determine the location of the balloon 132 based on known geometric relationships between the different components. For example, it may be assumed that the location of the deployed balloon 132 will be between the location recorded when the fault condition was detected (e.g., tip of the sheath 136), and the location of the EP catheter electrodes 124 within the PV ostium 10. Further, the volumetric location of the inflated balloon may be determined based on a measured angle trajectory and a plane of the PV ostium previously imaged by the EP catheter.

In some embodiments, the processor circuit is configured to generate and output the visualization of the volumetric location of the balloon immediately or soon after the EP catheter is advanced back out of the sheath.

In some embodiments, once the EP catheter is advanced back out of the sheath to the previous location, the EP catheter and the inflated balloon are advanced together so as to maintain the relative longitudinal (along the length axis of the catheter) positioning between the EP catheter electrodes and the inflated balloon.

In other embodiments, the balloon may be advanced independently of the EP catheter to the ablation site.

In some embodiments, such as those wherein the EP catheter and inflated balloon are advanced together, the relative position of the balloon and the EP catheter is preferably fixed or kept constant. In such case the location of the balloon may be tracked over time by means of tracking the location of one or more of the location electrodes of the EP catheter as determined using the fault condition procedure (e.g. steps 702 to 706). Preferably the location electrode is one that is nearest or at the tip of the balloon catheter sheath. The location of the balloon may then be determined by using one or more geometric parameters of the balloon catheter, such as for example the distance between balloon catheter sheath tip and a known part of the actual balloon, possibly in combination with a shape of the inflated balloon if in inflated state

In some embodiments, the orientation of the balloon catheter sheath section that comprises the balloon may be taken into account during the determination of the balloon location. This may help making the balloon location determination more accurate. As mentioned herein before, the volumetric location of the inflated balloon may be determined based on a measured angle trajectory and a plane of the PV ostium previously imaged by the EP catheter. Alternatively, or additionally a reconstructed model (visualization) of at least a part of the EP catheter may be used for such orientation or angle trajectory determination. For example, in some embodiments, the shape of the EP catheter tip comprising the electrodes may be partially or entirely determined from the relative locations of the EP catheter electrodes. The orientation of such shape may then be determined which, in turn may be sued to determine the orientation of the balloon catheter section carrying the balloon and therewith the balloon. Such orientation in combination with a location of the balloon catheter section using the fault detection procedure can be used to determine the location and trajectory over time of such balloon. For example, prior to, during or just after a fault detection, the EP catheter, or for example at least a section of it that is near the sheath of the balloon catheter and extended from that sheath, may be manipulated to have a straight shape. Locating the electrodes on such straight shape section may be used to infer a direction or orientation in space of such EP catheter. Assessment of such shape may for example be done by comparing geodesic distance (calculable from the known interelectrode distances on the EP catheter section) with a spatial distance between two electrodes (preferably the electrodes are the electrodes furthers apart from a group of electrodes larger than 3, 4 or even 5. All of the EP catheter tip electrodes may be used when part of a straight designed section. In embodiments a section may be considered straight for example if the ratio between the latter and former does not deviate more than 10% from 1. Because of the design constraints of the Balloon catheter and the EP catheter, the balloon catheter sheath having the balloon will have substantially the same orientation as that of the EP catheter section.

A further determination of shape may also be used. For example, the EP catheter may be manipulated to attain a spiral or lasso shape. In such case the locations of the electrodes may be used to define a virtual axis around which the EP catheter spiral is centered or which is centered within and perpendicular to a virtual plane that includes the lasso shaped part of the EP catheter. The directions or orientations of such axis may be related to the determined orientation of the balloon catheter sheath as determined herein before. For example, one or more angles between axis and determined orientation of the balloon catheter may be determined and used to reconstruct the balloon catheter orientation from a determined axis based on catheter electrode locations as detected at any one particular time. Known vector mathematical operations may be used to determine the axes from relative spatial locations of electrodes of the relevant sections of the catheter. Other shapes of different EP catheters may be used according to similar principles defining relevant orientational axes of such shapes to relate to the orientation of a sheath tip.

In some embodiments, the shape of the EP catheter or sections thereof as described e.g. herein before, and preferably in combination with the relative position of the EP catheter with respect to the balloon catheter, may be kept fixed during advancement of the balloon catheter and EP catheter together. A relatively accurate location (and optionally orientation) of the balloon can thus be determined during advancement of the balloon to the PV. Such location and orientation may be made part of the visualization to be output to the user. In embodiments, the geometric properties preferably include design parameters of the balloon defining its shape in at least inflated form. This allows reconstruction of a balloon model. A further parameter preferably provided is at least one design parameter (e.g. distance) indicative of the location of such model or part thereof with regard to the balloon catheter sheath tip. The embodiments of the present disclosure provide for image-guided balloon therapy by detecting and visualizing an inflated balloon, such as a cryoballoon, angioplasty balloon, or scoring balloon, within an anatomical cavity of a patient. However, it will be understood that the embodiments described above are exemplary and are not intended to limit the scope of the present disclosure. Thus, any type of balloon ablation therapy and the corresponding balloons used in such therapies may be visualized using the principles of the present disclosure. Furthermore, in some embodiments, the approaches of the methods 200, 500, 700 described above may be to detect and/or visualize other types of therapeutic and/or diagnostic devices to guide other types of therapies, such as balloon angioplasty, laser balloon therapy, balloon breast brachytherapy, drug delivery using drug- coated balloons, neuro-radiology, etc.

For example, with reference to Fig. 10, a gui dewire 820 having a plurality of electrodes 824 at a distal end of the guidewire 820 can be advanced into a stenosed section 32 of a blood vessel 30 to obtain EP data and/or anatomical mapping data of the vessel 30. Accordingly, an anatomical map of the vessel 30 may be generated and displayed. It will be understood that the anatomical map of the vessel 30 may appear similar to the maps generated for other parts of the anatomy, such as the map of the left atrium and pulmonary veins shown in Fig. 6. In that regard, the anatomical map of the vessel 30 may show a cross- sectional view, a partially-transparent view, a volumetric view, or any other suitable view. In some embodiments, the processor circuit is further configured to visualize a location of the guidewire 820 within the map of the vessel 30. Next, an angioplasty balloon catheter 830 is advanced over the guidewire 820 to the stenosed region 32. The angioplasty balloon 834 is then inflated to apply expand or dilate the stenosed region 32. When the balloon 834 is inflated, the electrodes 824 of the guidewire 820 can be used to detect changes in the conductance field caused by the presence of the inflated balloon 834, as described with respect to the method 500. Alternatively, the guidewire 820 can be temporarily withdrawn into the sheath of the catheter 830 while its location is recorded, and then advanced out of the catheter 830 to determine the relative location of the balloon 834, as described with respect to the method 700. A visualization of the location of the balloon 834 can then be output to the display to guide placement of the balloon 834 at the stenosed segment 32. In still other embodiments, a drug-coated balloon, a radiation balloon, a scoring balloon, or any other suitable treatment balloon is advanced over a guidewire or catheter to a treatment site. Using one or more of the approaches described above, the therapy balloon can be spatially localized and visualized within the vessel relative to the treatment site (e.g., stenosis, lesion, tumor, etc.) to ensure proper placement and deployment of the therapy balloon. This approach may be particularly advantageous in neuro radiology and/or vascular balloon therapy procedures in which the therapeutic balloons are too small to carry electrodes for visualization.

Further, in some embodiments, once a therapeutic device, such as an ablation balloon, has been positioned at the ablation site using the techniques described above, the processor circuit may perform other guidance techniques, such as leak detection, to verify that the balloon fully occludes the ablation site (e.g., PV ostium). For example, a balloon ablation guidance system may use one or more of the techniques described in U.S.

Publication No. 2018/0125575, titled “LESION ASSESSMENT BY DIELECTRIC PROPERTY ANALYSIS,” filed May 11, 2016, U.S. Patent Application Publication No. 2018/0116751, titled “CONTACT QUALITY ASSESSMENT BY DIELECTRIC PROPERTY ANALYSIS,” filed May 11, 2016, and/or European Patent Application 19184189.9, titled “ELECTROPHY SIOLOGIC AL GUIDANCE OF BALLOON ABLATION AND ASSOCIATED DEVICES, SYSTEMS, AND METHODS,” filed July 3, 2019, the entireties of which are hereby incorporated by reference. Further, it will be understood that one or more techniques described above, such as the techniques of the methods 500 and 700, may be combined to detect and visualize a location of an ablation balloon to guide an ablation procedure.

It will be understood that one or more of the steps of the methods 200, 500, 700, such as generating the map of a body cavity, detecting the location of the inflated balloon, and outputting visualizations to a display indicating the detected location of the balloon, can be performed by one or more components of an EP-guided ablation system, such as a processor circuit of a mapping and guidance system, an EP catheter, a cryoballoon catheter, an RF ablation balloon catheter, external body patch electrodes, or any other suitable component of the system. For example, the described ablation procedures may be carried out by the system 100 described with respect to Fig. 2, which may include the processor circuit 150 described with respect to Fig. 3. In some embodiments, the processor circuit can use hardware, software or a combination of the two to perform the analyses and operations described above. For example, the result of the signal processing steps of the methods 200, 500, 700 may be processed by the processor circuit executing a software to make determinations about the locations of the electrode in the 3D image, etc.

It will also be understood that the embodiments described above are exemplary and are not intended to limit the scope of the disclosure to a given clinical application. For example, as mentioned above, the devices, systems, and techniques described above can be used in a variety of balloon ablation applications that involve occlusion of a body cavity or body lumen. For example, in some embodiments, the techniques described above can be used to guide a cryoablation procedure using a cryocatheter comprising a cryoballoon as described above. In other aspects, the techniques described above can be used to guide an RF ablation procedure in which a plurality of RF ablation electrodes positioned on the surface of an inflatable balloon are used to create an electrically-isolating lesion in cardiac tissue. For example, the HELIOSTAR RF balloon catheter, manufactured by Biosense Webster, Inc., includes 10 ablation electrodes positioned on an external surface of the inflatable balloon, and 10 electrodes on a circular mapping catheter positioned distally of the balloon and configured to be positioned inside the pulmonary vein. Such a balloon may be visualized according to the principles of the current disclosure without using the 10 electrodes positioned on the external surface of the inflatable balloon, but by only using one or more of the 10 electrodes on the circular mapping catheter.

Further, while the ablation procedures are described with respect to the heart and associated anatomy, it will be understood that the same methods and systems can be used to guide ablation procedures in other body volumes, including other regions of interest in the heart, or other body cavities and/or lumens. For example, in some embodiments, the EP guided ablation procedures described herein can be used to guide treatment procedures in any number of anatomical locations and tissue types, including without limitation, organs including the liver, heart, kidneys, gall bladder, pancreas, lungs; ducts; intestines; nervous system structures including the brain, dural sac, spinal cord and peripheral nerves; the urinary tract; as well as valves within the blood, chambers or other parts of the heart, and/or other systems of the body. The anatomy may be a blood vessel, as an artery or a vein of a patient’s vascular system, including cardiac vasculature, peripheral vasculature, neural vasculature, renal vasculature, and/or any other suitable lumen inside the body. In addition to natural structures, the approaches described herein may be used to examine man-made structures such as, but without limitation, heart valves, stents, shunts, filters and other devices in the kidneys, lungs, or any other suitable body volume. Further, the balloon detection and visualization techniques described above can be employed in various applications to determine the location of a balloon. For example, the procedures described above can be used for intravascular balloon-based stenosis treatment, or any other suitable application.

Further examples according to the present disclosure are defined herein below.

Example 1. An apparatus for guiding balloon therapy within an anatomical cavity, comprising: a processor circuit configured for communication with a plurality of electrodes, wherein the processor circuit is configured to: control the plurality of electrodes to detect an electromagnetic field within the anatomical cavity; receive a geometrical parameter associated with a balloon configured to provide the balloon therapy within the anatomical cavity; determine, based on the detected electromagnetic field and the geometrical parameter associated with the balloon, a location of the balloon within the anatomical cavity; and output a signal representative of a visualization of the location of the balloon within the anatomical cavity.

Example 2. The apparatus of example 1, wherein the processor circuit is configured to: control the plurality of electrodes to detect the electromagnetic field at a first time before the balloon is inflated and a second time after the balloon is inflated, compute, based on the electromagnetic field detected at the first time, a first conductance map of the anatomical cavity corresponding to the first time; compute, based on the electromagnetic field detected at the second time, a second conductance map of the anatomical cavity corresponding to the second time; compare the first conductance map and the second conductance map to determine a change in a conductance field of the anatomical cavity between the first time and the second time; and determine, based on the geometrical parameter and the determined change in the conductance field, the location of the balloon within the anatomical cavity.

Example 3. The apparatus of example 2, wherein the processor circuit is configured to control a plurality of catheter-mounted electrodes to detect the electromagnetic field at the first time and the second time. Example 4. The apparatus of example 3, wherein the processor circuit is configured to control the plurality of catheter-mounted electrodes to emit the electromagnetic field at the first time and the second time.

Example 5. The apparatus of example 4, wherein the processor circuit is configured to control the plurality of catheter-mounted electrodes to detect the electromagnetic field based on combinations of a receiving electrode of the plurality of catheter-mounted electrodes and an emitting frequency.

Example 6. The apparatus of example 3, wherein the processor circuit is configured to control a plurality of external electrodes to emit the electromagnetic field at the first time and the second time.

Example 7. The apparatus of example 1, wherein the processor circuit is configured to: control a plurality of catheter-mounted electrodes to detect the electromagnetic field within the anatomical cavity; control the plurality of catheter-mounted electrodes to detect a fault condition in which each catheter-mounted electrode of the plurality of catheter-mounted electrodes is occluded; and determine the location of the balloon within the anatomical cavity based on the detected fault condition and the geometric parameter associated with the balloon.

Example 8. The apparatus of example 1, wherein the geometrical parameter comprises one or more of: a relative positioning of the balloon relative to the plurality of electrodes; a shape of the balloon; a boundary condition of the balloon within the anatomical cavity; or a geometric dimension of the balloon when inflated.

Example 9. The apparatus of claim 1, wherein the visualization of the location of the balloon comprises a graphical representation of a shape of the balloon when inflated, within the anatomical cavity, and wherein the processor circuit is configured to update the graphical representation of the shape of the balloon positioned relative to the anatomical cavity, in real time, based on the detected electromagnetic field. Example 10. The apparatus of claim 1, wherein the processor circuit is configured to output the signal representative of the visualization of the location of the balloon to a display in communication with the processor circuit.

Example 11. A system for guiding balloon therapy within an anatomical cavity, comprising: the apparatus as in any of example 1-10; and an electrophysiology catheter comprising an elongate tip member configured to be positioned distally of the balloon, wherein the plurality of electrodes is positioned on the elongate tip member.

Example 12. A method for guiding balloon therapy within an anatomical cavity, comprising: controlling a plurality of electrodes to detect an electromagnetic field within the anatomical cavity; receiving a geometrical parameter associated with a balloon configured to provide the balloon therapy within the anatomical cavity; determining, based on the detected electromagnetic field and the geometrical parameter associated with the balloon, a location of the balloon within the anatomical cavity; and outputting a signal representative of a visualization of the location of the balloon within the anatomical cavity.

Examplel3. The method of example 12, wherein controlling the plurality of electrodes comprises: controlling the plurality of electrodes to detect the electromagnetic field at a first time before inflating the balloon; and controlling the plurality of electrodes to detect the electromagnetic field at a second time after inflating the balloon; and wherein determining the location of the balloon within the anatomical cavity comprises: computing, based on the electromagnetic field detected at the first time, a first conductance map of the anatomical cavity corresponding to the first time; computing, based on the electromagnetic field detected at the second time, a second conductance map of the anatomical cavity corresponding to the second time; comparing the first conductance map and the second conductance map to determine a change in a conductance field of the anatomical cavity between the first time and the second time; and determining, based on the geometrical parameter and the determined change in the conductance field, the location of the balloon within the anatomical cavity.

Example 14. The method of example 12, wherein controlling the plurality of electrodes comprises controlling a plurality of catheter-mounted electrodes to detect the electromagnetic field within the anatomical cavity, and wherein determining the location of the balloon within the anatomical cavity comprises: controlling the plurality of catheter-mounted electrodes to detect a fault condition in which each catheter-mounted electrode of the plurality of catheter-mounted electrodes is occluded; and determining, based on the detected fault condition and the geometric parameter associated with the balloon, the location of the balloon within the anatomical cavity.

Example 15. A computer program product comprising: a non-transitory computer-readable medium having program code recorded thereon, the program code including: code for controlling a plurality of electrodes to detect an electromagnetic field within an anatomical cavity; code for receiving a geometrical parameter associated with a balloon configured to provide therapy within the anatomical cavity; code for determining, based on the detected electromagnetic field and the geometrical parameter associated with the balloon, a location of the balloon within the anatomical cavity; and code for outputting a signal representative of a visualization of the location of the balloon within the anatomical cavity. Persons skilled in the art will recognize that the apparatus, systems, and methods described above can be modified in various ways. Accordingly, persons of ordinary skill in the art will appreciate that the embodiments encompassed by the present disclosure are not limited to the particular exemplary embodiments described above. In that regard, although illustrative embodiments have been shown and described, a wide range of modification, change, and substitution is contemplated in the foregoing disclosure. It is understood that such variations may be made to the foregoing without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the present disclosure.