Patent Description:
Intrabody probes, such as catheters, may include position sensors at their distal ends. For example, <CIT> describes a method for attaching a sensor to an inflatable balloon. The method is particularly useful in the construction of a tissue ablation catheter for forming a lesion along a substantially circumferential region of tissue wherein a sensor is used for monitoring the temperature of the tissue being ablated. In an embodiment, one or more position sensor elements (not shown) are located in, or near, the expandable member. A circumferential ablation member with the ablation element that forms an ablative circumferential band that circumscribes an expandable member embodied as a balloon. In a sequential mode of operation for the ablation member, the position sensor of the position monitoring assembly may be coupled to the expandable member.

As another example, <CIT> describes a catheter for measuring physiological signals in a heart comprises a structure at a distal end of the catheter wherein the structure has a plurality of arms, an electrode fixed to each arm and a device for generating position information located on each arm. The arms are located near the long axis of the catheter during insertion of the catheter within a heart and the arms are spreadable apart and away from the long axis of the catheter when the structure is within the heart. In a preferred embodiment of the invention, a position sensor having one or more coils is embedded in a lobe, preferably near an electrical sensor, so as to more exactly determine the relative position of the electrical sensor.

<CIT> describes a system for diagnosis or treatment of tissue in a body. The system includes an ablation catheter having an ablation delivery member disposed proximate a distal end of a shaft of the catheter and configured to deliver ablation energy to ablate the tissue. In one embodiment, the ablation delivery member comprises an ablation electrode and may also be configured to generate a signal indicative of electrical activity in the tissue. The catheter further includes one or more sensing electrodes disposed proximate the ablation delivery member. The sensing electrodes are configured to generate signals indicative of electrical activity in the tissue. In an embodiment, the sensing electrodes function as position sensors.

International patent application publication <CIT> describes a system and a method for tracking the position, and orientation of a probe such as a catheter whose transverse inner dimension may be at most about <NUM> millimeters. Three planar antennas that at least partly overlap are used to transmit electromagnetic radiation simultaneously, with the radiation transmitted by each antenna having its own spectrum. In the case of single-frequency spectra, the antennas are provided with mechanisms for decoupling them from each other. A receiver inside the probe includes sensors of the three components of the transmitted field, with sensors for at least two of the three components being pairs of sensors, such as coils, disposed symmetrically with respect to a common reference point. In an example, a cardiac catheter includes four electrodes mounted on an outer surface of an inflatable latex balloon and an electrode mounted on the distal end of an inner sleeve. The catheter comprises a set of three orthogonal electromagnetic field component sensors.

Certain optional features of the invention are defined in the dependent claims.

An embodiment of the present invention provides an expandable balloon coupled to a distal end of a shaft for insertion into an organ of a patient. The expandable balloon includes an expandable membrane, one or more electrodes and one or more respective conductive coils. The one or more electrodes are disposed over an external surface of the membrane. The one or more respective conductive coils are each disposed proximate a respective electrode and wound around the perimeter of the electrode. The one or more conductive coils are configured as magnetic sensors.

In some embodiments, the expandable balloon further includes one or more respective leads, each configured to provide a common electrical contact for an electrode and for a coil wound around the electrode.

In some embodiments, the conductive coil is disposed on a flexible printed board (PBC), and wherein the flexible PCB is attached to the expandable membrane.

In an embodiment, the one or more electrodes are radiofrequency (RF) ablation electrodes. In an alternative embodiment, the one or more electrodes are sensing electrodes to sense signals produced by cardiac tissues.

There is additionally provided, in accordance with an embodiment of the present invention, a system including an expandable balloon and a processor. The expandable balloon is coupled to a distal end of a shaft for insertion into an organ of a patient, wherein the expandable balloon includes an expandable membrane, one or more electrodes, and one or more respective conductive coils. The one or more electrodes are disposed over an external surface of the membrane. The one or more respective conductive coils are each disposed proximate a respective RF ablation electrode, wherein the one or more conductive coils are configured as magnetic sensors. The processor is configured to, based on signals received from the one or more conductive coils, estimate a spatial configuration of the expandable balloon inside the organ.

In some embodiments, the processor is configured to estimate the spatial configuration of the expandable balloon by estimating a location of the balloon inside the organ.

In some embodiments, the processor is configured to estimate the spatial configuration of the expandable balloon by estimating an orientation of the balloon inside the organ.

In an embodiment, the processor is configured to estimate the orientation by estimating at least one of a deflection of the balloon relative to a longitudinal axis defined by the distal end of the shaft and a roll angle about the longitudinal axis.

In another embodiment, the processor is configured to estimate the spatial configuration of the expandable balloon by estimating a shape of the balloon inside the organ.

In some embodiments, the processor is configured to estimate the shape by identifying an extent of expansion of the balloon.

In an embodiment, the processor is configured to estimate the shape by detecting whether the balloon is fully expanded or not.

There is furthermore provided, in accordance with an embodiment of the present invention, a manufacturing method, including disposing one or more electrodes over an external surface of a membrane of an expandable balloon for insertion into an organ of a patient. a respective conductive coil is wound around a perimeter of each electrode, wherein the conductive coil is configured as a magnetic sensor.

A balloon catheter typically comprises an expandable balloon that is coupled to a distal end of a shaft for insertion into a cavity of an organ of a patient. For the best outcome of a balloon treatment, a physician may need to determine an exact location, orientation and shape of the balloon inside the organ. For example, in a balloon ablation procedure performed inside the left atrium of the heart, the physician may need to know the exact location and orientation of the balloon relative to an opening of a pulmonary vein so as to evenly ablate tissue over an entire circumference of the opening.

In the context of this disclosure, the term "balloon location and orientation" refers to either or both of (i) a location plus direction in space of the longitudinal axis defined by a distal end of the shaft, and (ii) a location plus tilt or deflection of the balloon relative to the longitudinal axis. When the expanded balloon is free of constraints the surface of the balloon revolves around a direction parallel to the longitudinal axis. In such case, ablation elements, such as electrodes, which lay on an equator of the balloon (the equator defining a plane perpendicular to the direction of the balloon) are aligned perpendicular to the longitudinal axis.

However, when the balloon is constrained and/or deflected upon contact with cavity wall tissue, the balloon direction is not necessarily parallel to the longitudinal axis. As a result, the ablation electrodes are tilted at some unknown angle. For example, the electrodes may be tilted relative to an opening of the pulmonary vein to be ablated by the electrodes, resulting in uneven ablation.

Embodiments of the present invention that are described hereinafter provide an expandable radiofrequency balloon catheter comprising one or more magnetic sensors, such as single-axis magnetic sensors, each of embodied as a conductive coil wound around a respective electrode disposed over an external surface of the expandable membrane of the balloon. In some embodiments, the electrode is an RF ablation electrode. Using the disclosed sensors, a processor of a magnetic tracking system estimates a spatial configuration of the balloon inside the organ, comprising a location and/or orientation and/or shape of the balloon, accurately enough in demanding clinical applications, as described below.

Additionally or alternatively, the processor may be configured to estimate at least one of a deflection of the balloon relative to a longitudinal axis defined by the distal end of the shaft and a roll angle (i.e., rotation angle) about the longitudinal axis. These parameters are also considered examples of the "spatial configuration" of the balloon. In this way, the physician can advance the balloon to target tissue otherwise difficult to access, and only then expand the balloon. After the balloon is fully expanded, the magnetic position system, using the disclosed coils, is capable of tracking the balloon location and/or direction even if the balloon is constrained and/or deflected relative to a longitudinal axis defined by a distal end of a shaft.

In some embodiments, the spatial configuration of the expandable balloon further comprises a shape of the balloon example, by identifying an extent of expansion of the balloon. In an embodiment, the processor is configured to estimate the shape by detecting whether the balloon is fully expanded or not. In some embodiments, using the disclosed coil sensors the physician can determine the balloon orientation even when the balloon is only partially expanded (e.g. partially inflated).

Typically, with multiple RF ablation electrodes disposed over the membrane, multiple respective magnetic sensors can be disposed over an entire circumference of the expandable balloon. In some embodiments, the disclosed coil encompasses an area approximately equal to that of the ablation electrode, which is sufficient, for a coil with several windings around the electrode perimeter, to generate a location signal. Typically, each winding width is several tens of microns, so that the overall width of the perimeter is kept below half a millimeter.

In some embodiments, a single lead is used to electrically connect both the ablation electrode and the wound coil to respective interfaces of the system (i.e., a single lead, which is configured to provide a common electrical contact to an RF ablation electrode and the coil wound around the RF ablation electrode), so only one additional lead is required for the coil (i.e., to close a circuit by connecting the other end of the coil). In some embodiments, the ablation electrode is separated into two or more sub-electrodes, and both of the leads to the ablation electrode are used to connect to the coil, so that no extra leads are required.

Typically, the processor is programmed in software containing a particular algorithm that enables the processor to conduct each of the processor-related steps and functions outlined hereinafter.

The ability to estimate the shape of the balloon is enabled, for example, by the fact that the coils (the position sensors) are fitted on the membrane, away from the longitudinal axis of the catheter. By providing magnetic tracking capabilities of balloon position, orientation and shape as described above, embodiments of the present invention enable a physician operating the balloon catheter to align the balloon inside a cavity relative to target tissue, so as for example, to uniformly ablate tissue.

Furthermore, the disclosed coils may eliminate the need to incorporate additional means for tracking the balloon catheter position and orientation. For example, the disclosed technique may enable providing a "smooth" balloon, by eliminating the need to fit an additional position and/or orientation sensing element at a protruding distal edge of the balloon catheter.

<FIG> is a schematic pictorial illustration of a catheter-based position tracking and ablation system <NUM> comprising a balloon catheter <NUM>, in accordance with an embodiment of the present invention. System <NUM> is used to determine the position and direction of balloon catheter <NUM>, seen in an inset <NUM> coupled to a distal end of a shaft <NUM>. System <NUM> is further used for providing information regarding the balloon state of inflation (e.g., if balloon <NUM> is fully expanded). Typically, balloon catheter <NUM> is used for therapeutic treatment, such as spatially ablating cardiac tissue, for example at the left atrium.

Physician <NUM> navigates balloon catheter <NUM> to a target location in a heart <NUM> of a patient <NUM> by manipulating shaft <NUM> using a manipulator <NUM> near the proximal end of the catheter and/or deflection from a sheath <NUM>. Balloon catheter <NUM> is inserted, in a folded configuration, through sheath <NUM>, and only after the balloon is retracted from the sheath <NUM> does balloon catheter <NUM> regain its intended functional shape. By containing balloon catheter <NUM> in a folded configuration, sheath <NUM> also serves to minimize vascular trauma on its way to the target location.

For position and direction measurements, balloon catheter <NUM> incorporates conductive coils <NUM>, which are disposed on an outer surface of the balloon membrane <NUM> and are used as magnetic position sensors, as described below. Each coil is wound around a perimeter of a radiofrequency (RF) ablation electrode <NUM>, where the ablation electrode and the coil share an electrical lead, and are both connected by wires running through shaft <NUM> to interface circuits <NUM> in a console <NUM>. A detailed view of coil <NUM> wound around the perimeter of ablation electrode <NUM>, where both are disposed over membrane <NUM>, is shown in inset <NUM> of <FIG>.

Console <NUM> comprises a processor <NUM>, typically a general-purpose computer and a suitable front end and interface circuits <NUM> for transmitting and receiving signals, such as RF signals and position signals, respectively. Interface circuits <NUM> may receive electrocardiograms from surface electrodes <NUM>, which are seen in the exemplified system as attached by wires running through a cable <NUM> to the chest and to the back of patient <NUM>.

Console <NUM> comprises a magnetic-sensing sub-system. Patient <NUM> is placed in a magnetic field generated by a pad containing magnetic field radiators <NUM>, which are driven by unit <NUM>. The magnetic fields irradiated by radiators <NUM> generate signals in coils <NUM>, which are then provided as corresponding electrical inputs to processor <NUM>, which uses the generated signals to calculate a position and/or direction of balloon catheter <NUM>.

The method of position sensing using external magnetic fields is implemented in various medical applications, for example, in the CARTO™ system, produced by Biosense Webster Inc. , and is described in detail in <CIT>, <CIT>, <CIT>,<CIT>,<CIT>and<CIT>, in <CIT>, and in <CIT>, <CIT> and<CIT>.

Processor <NUM> is typically programmed in a suitable software code to carry out the functions described herein. The software may be downloaded to the computer in electronic form, over a network, for example, or it may, alternatively or additionally, be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory. In particular, processor <NUM> runs a dedicated algorithm as disclosed herein, including in <FIG>, that enables processor <NUM> to perform the disclosed steps, as further described below.

<FIG> shows only elements related to the disclosed techniques, for the sake of simplicity and clarity. System <NUM> typically comprises additional modules and elements that are not directly related to the disclosed techniques, and thus are intentionally omitted from <FIG> and from the corresponding description.

<FIG> is a schematic pictorial illustration of balloon catheter <NUM> of <FIG> comprising one or more coil sensors <NUM>, in accordance with an embodiment of the present invention. As seen, balloon <NUM> is coupled to the distal end of shaft <NUM> that defines a longitudinal axis <NUM>. Balloon catheter <NUM> comprises RF ablation electrodes <NUM> that are evenly disposed over an equator <NUM> of expandable membrane <NUM>. Each coil <NUM> is wound around the perimeter of each RF ablation electrode <NUM>. As further seen, balloon catheter <NUM> is free of constraints, and thus equator <NUM> lies in a plane perpendicular to longitudinal axis <NUM>.

In an embodiment, coil <NUM> is disposed on a flexible printed circuit board (PCB) <NUM>, and flexible PCB <NUM> is attached to expandable membrane <NUM>. In some embodiments coil <NUM> is made of a wire wound and encapsulated over to the flexible PCB. In another embodiment, coil <NUM> is patterned (e.g., printed) over flexible PCB <NUM>.

Inset <NUM> shows balloon catheter <NUM> in two directions, the "free" direction parallel to axis <NUM>, and a "deflected" direction <NUM>'. As seen, when the balloon is deflected, for example, due to contact with wall tissue, the center location of the balloon changes from a location <NUM> to a deflected location <NUM>'. Moreover, equator <NUM> is deflected to an equator <NUM>', which means that electrodes <NUM> are aligned around the new direction <NUM>'. Location <NUM>' and direction <NUM>' can be tracked using the disclosed coil sensors disposed over membrane <NUM>, as described below. In some embodiments, based on signals from the coil sensors, processor <NUM> estimates a roll angle <NUM> of balloon catheter <NUM> around axis <NUM>.

<FIG> shows that each RF ablation electrode <NUM> and a respective coil <NUM> share a lead <NUM>, as further described below. In an embodiment, shown in inset <NUM>, each coil <NUM> is made of several turns <NUM> (i.e., windings <NUM>). Each turn <NUM> of coil <NUM> has a width of several tens of microns, so that the overall width <NUM> of the perimeter (i.e., of coil <NUM>) is kept to no more of several hundred microns. Each ablation electrode has an area of several tens of mm<NUM>, so that a coil wound several turns around the electrode perimeter has an effective area of several hundred mm<NUM>, which is sufficient for generating the required signal. A typical width of a turn on coil <NUM> is about <NUM>-<NUM> microns, so six or seven turns results in an effective area of about <NUM>-<NUM><NUM>.

The illustration shown in <FIG> is chosen purely for the sake of conceptual clarity. Other geometries of ablation electrodes are possible. Elements which are not relevant to the disclosed embodiments of the invention, such as irrigation ports and temperature sensors, are omitted for the sake of clarity.

<FIG> is a schematic diagram of an electrical connection scheme of RF ablation electrode <NUM> and coil sensor <NUM> of <FIG>, in accordance with an embodiment of the present invention. The content of frame 40a schematically shows the disclosed electrical circuit formed with each ablation electrode <NUM> (represented by a resistor 51a), and the wound coil <NUM> (represented by a coil 50a). As seen, coil 50a shares a lead <NUM> with resistor 51a, wherein coil 50a generates a tracking signal iSignal.

Signals generated by coil 50a are transmitted using lead <NUM> and subsequently by a wire in shaft <NUM> (not shown) to electrical readout circuitry 44c included in interface circuits <NUM> inside console <NUM>, schematically shown by a frame 44a. An RF source 43c to electrode 51a is also seen inside frame 44a. Using a single lead <NUM> to connect both coil 50a and resistor 51a (i.e., RF ablation electrode <NUM>) to interface circuits <NUM> saves separate dedicated wiring.

The schematic diagram shown in <FIG> is chosen purely for the sake of conceptual clarity. Other connection schemes that utilize a shared lead, such as a lead shared as a common electrical ground, are possible. In an embodiment, coil <NUM> may be connected via a reinforced isolated amplifier that converts the generated signal from a high-voltage domain to a low-voltage domain. Additional elements may be used as well, such as electronic demodulation circuits.

<FIG> is a flow chart that schematically illustrates a method and algorithm for tracking the expandable balloon of <FIG> using one or more coil sensors which may be used with a system in accordance with an embodiment of the present invention. The algorithm of <FIG> ensures that one skilled in the computer art can generate the necessary software code, as well as any other needed auxiliary steps, for a general-purpose computer to carry out the specific purposes of tracking the location or shapes of the expandable balloon of <FIG>. The algorithm according to the present embodiment carries out a process that begins with physician <NUM> positioning a partially expanded balloon catheter <NUM> at a target location inside a cardiac cavity of heart <NUM>, such as at an ostium of a pulmonary vein, at a balloon positioning step <NUM>. Next, at a balloon tracking step <NUM>, system <NUM> uses coils <NUM> to measure a position and an orientation of balloon catheter <NUM>, e.g., relative to a given cross section (i.e., slice) of the ostium. Next, physician <NUM> decides if the partially expanded balloon catheter <NUM> is aligned correctly relative to the ostium, at a decision step <NUM>.

If physician <NUM> finds that balloon catheter <NUM> is well aligned, then physician <NUM> fully inflates the balloon and performs a treatment, such as an RF ablation, in an RF balloon treatment step <NUM>.

<FIG> is a flow chart that schematically illustrates a method and algorithm for estimating a spatial configuration of the expandable balloon of <FIG> which may be used with a system in accordance with an embodiment of the present invention. By virtue of the embodiments described herein, we have devised an algorithm, as shown in <FIG>, for determining locations as well as other operational parameters of a balloon catheter while the balloon is located within biological tissues. In particular, the method can be achieved with the following algorithm exemplified in <FIG>: irradiating (<NUM>) one or more magnetic fields inside an organ of a patient, and generating (<NUM>) signals resulting from the generated magnetic fields. The signals are generated by one or more conductive coils from the magnetic fields irradiating upon the coils, each of which is disposed proximate each electrode disposed over an external surface of a membrane of an expandable balloon coupled to a distal end of a shaft inserted in an organ of the patient. The step continues with using a magnetic tracking system, based on the generated signals and estimating (<NUM>) a spatial configuration of the expandable balloon inside the organ. It is noted that the estimating may include estimating one or more of the following: estimating the location of the balloon inside the organ, estimating the orientation of the balloon inside the organ, estimating at least one of a deflection of the balloon relative to a longitudinal axis defined by the distal end of the shaft and a roll angle about the longitudinal axis, and estimating a shape of the balloon inside the organ. The step of estimating a shape may include identifying an extent of expansion of the balloon or detecting whether the balloon is fully expanded or not.

The example flow chart shown in <FIG> is chosen purely for the sake of conceptual clarity. The present embodiment also comprises additional steps of the algorithm, such as acquiring intra-cardiac electrocardiograms, which have been omitted from the disclosure herein purposely in order to provide a more simplified flow chart given that one skilled in this art has the requisite background knowledge for programming such algorithm in the field of electrophysiology. In addition, other steps, such as temperature measurements and applying irrigation, are omitted for clarity of presentation.

Although the embodiments described herein mainly address cardiac applications, the methods and systems described herein can also be used in other applications, such as in otolaryngology, neurology, cardiology, blood vessel treatment and renal denervation.

Claim 1:
An expandable balloon (<NUM>) coupled to a distal end of a shaft for insertion into an organ of a patient, the expandable balloon comprising:
an expandable membrane (<NUM>);
one or more electrodes (<NUM>) disposed over an external surface of the membrane (<NUM>), each electrode of the one or more electrodes comprising a perimeter; and
one or more respective conductive coils (<NUM>), each disposed proximate a respective electrode (<NUM>) wherein the one or more conductive coils (<NUM>) are configured as magnetic sensors, characterized in that each of the one or more conductive coils is wound around the perimeter of the respective electrode (<NUM>).