Patent Description:
Various techniques for verifying catheter contact with tissue were proposed in the patent literature. For example, <CIT> describes a cardiac ablation instrument that includes a catheter body and a tear-shaped balloon connected to the catheter body. The instrument further includes a radiant energy emitter that is axially movable within a central lumen of the catheter body. A radiant energy transparent body surrounds the energy emitter and includes a plurality of illumination fibers disposed circumferentially about the energy emitter. A detector communicates with a contact sensing element and is configured to determine an amount of at least one-color component of the reflected light. The amount of the at least one-color component being indicative of contact between the balloon and a target tissue site.

As another example, <CIT> describes devices and methods for providing and using an ablation catheter. The catheter may include an expandable member having a plurality of electrodes, where each electrode is in association with at least one contact sensor and at least one light emitting element. Light is emitted in response to the contact of the contact sensor with the tissue to be ablated. A light sensor disposed centrally to the catheter gathers light emitted from the light emitting elements and sends a signal to a system controller for display.

<CIT> describes ablation and visualization systems and methods to access quality of contact between a catheter and tissue. In some embodiments, a method for monitoring tissue ablation is provided, that comprises advancing a distal tip of an ablation catheter to a tissue in need of ablation; illuminating the tissue with UV light to excite NADH in the tissue, wherein the tissue is illuminated in a radial direction, an axial direction, or both; determining from a level of NADH fluorescence in the illuminated tissue when the distal tip of the catheter is in contact with the tissue; and delivering ablation energy to the tissue to form a lesion in the tissue.

<CIT> provides a medical device, system, and method having a flexible shaft and a multi-core fiber within the flexible shaft. The multi-core fiber includes a plurality of optical cores dedicated for shape sensing sensors, and a plurality of optical cores dedicated for force sensing sensors. A tip assembly can comprise a tip electrode and a coupler comprising at least one fiber support tube center. A distal portion of the coupler can be coupled to a proximal portion of the tip electrode. The tip assembly can further comprise a multi-core fiber comprising a plurality of cores and a fiber support tube. A proximal portion of the fiber support tube can be coupled to the at least one fiber support tube center.

<CIT> provides an ablation and monitoring system comprises a catheter, an optical coherence tomography (OCT) system, and an ablation generator. The catheter comprises one or more optical fibers to transmit a light beam to a tissue material and collect a reflected light from the tissue material. The OCT system is in optical communication with the catheter via the one or more optical fibers, providing the light beam to the one or more optical fibers and receiving the reflected light from the one or more optical fibers. The ablation generator is in electrical communication with the OCT system and with the catheter. The ablation generator provides radio frequency energy to the catheter for ablating the tissue material, monitors and assesses the ablation based on an information signal received from the OCT system.

An embodiment of the present invention provides a medical system according to claim <NUM>.

There is additionally provided, in accordance with an unclaimed embodiment of the present invention, a method including inserting a distal-end assembly of a catheter into a cavity of an organ of a patient, for performing a medical operation on tissue in the cavity. Transmitted light is guided in an optical fiber inside the distal-end assembly, to interact with the tissue of the cavity. Returned light that interacted with the tissue is guided via the same optical fiber. A contact of the distal-end assembly with the tissue is identified based on the returned light measured by a detector, and the identified contact is indicated to a user.

During a catheterization procedure of an organ of the body, such as cardiac electro-anatomical mapping and/or ablation, there may be a need to verify that electrodes disposed over an expandable membrane coupled to a distal end of a probe, such as a catheter, are in physical contact with wall tissue of a cavity of the organ, such as with a wall tissue of a cardiac chamber.

Embodiments of the present invention that are described hereinafter provide systems in which a distal-end assembly of a catheter includes means to emit light into surrounding media and collect light that interacts with the surrounding media, such as light reflected and/or scattered by a wall tissue of a cavity of the organ.

The disclosed techniques can be used with various distal-end assemblies. For example, the distal-end assembly may comprise an expandable frame, such as used in balloon and basket catheters, or comprise other frames, such as of basket, lasso, multi-arm, and tip catheters. In case of an expandable frame, the distal-end assembly may comprise a transparent expandable membrane (the remainder mostly covered by electrodes, e.g., of a balloon or a basket catheter).

In one embodiment, an optical fiber is installed in the expandable frame and used to transmit light from an external light source, such as a Light Emitting Diode (LED). The same optical fiber is used to convey returned light that interacts with a wall tissue of the cavity to an external detector (e.g., a photodiode). A distal end of the fiber, located inside the transparent expandable membrane of the distal end assembly, comprises a coupler, such as a grating coupler or a diffuser, configured to emit the transmitted light and to couple the returned light into the fiber.

An optical circulator is coupled at the proximal end of the optical fiber to separate the returned light from the transmitted light. The measurement from the detector (e.g., photodiode) is analyzed by a processor to indicate an occurrence of physical contact between the distal-end assembly and the tissue (by analyzing changes in the intensity of the returned light). The LED, the optical circulator, and the photodiode may be inside an external unit, also called hereinafter "contact detection module.

In another embodiment, the light source, the detector and the circulator are fitted at the distal-end assembly. For example, the LED, the circulator and the photodiode may all be located inside the transparent expandable membrane. In this embodiment, electrical signals are conveyed by a cable running in the catheter's shaft, to drive the LED and to convey measured electrical signals from the photodiode, in the opposite direction, to the processor.

In some embodiments, the processor initially measures the intensity of the returned light when the catheter is in the blood pool but prior to contact of the expanded membrane with tissue, therefore providing a reference value for the intensity. Since the intensity of the returned light changes when the transparent membrane contacts tissue relative to the reference value, the processor uses this change for contact detection.

A system is provided that includes at least (a) a catheter, comprising a distal-end assembly for performing a medical operation on tissue in a cavity of an organ of a patient, the distal-end assembly comprising an optical fiber configured to guide transmitted light to interact with the tissue of the cavity, and to return returned light that interacted with the tissue, (b) a light source configured to produce the transmitted light, (c) a detector configured to measure the returned light, (d) a circulator configured to couple the transmitted light from the light source to the optical fiber, and to couple the returned light from the optical fiber to the detector, and (e) a processor, configured to identify a contact of the distal-end assembly with the tissue based on the returned light measured by the detector, and to indicate the identified contact to a user.

By offering a single optical-fiber-based tissue contact detection, a balloon catheter can be made with smaller diameter, allowing better flexibility of the shaft, and improved maneuverability, and therefore enable improved access to some target body locations.

<FIG> is a schematic, pictorial illustration of a catheter-based diagnostics and/or ablation system <NUM> comprising a transparent balloon catheter <NUM>, in accordance with an embodiment of the present invention. System <NUM> comprises a catheter <NUM>, wherein a shaft <NUM> of the catheter is inserted by a physician <NUM> through the vascular system of a patient <NUM> through a sheath <NUM>. The physician then navigates a distal end 22a of shaft <NUM> to a target location inside a heart <NUM> of the patient.

In the embodiment described herein, catheter <NUM> may be used for any suitable diagnostic and/or therapeutic purpose, such as electrophysiological sensing and/or irreversible electroporation (IRE) and/or radiofrequency (RF) ablation to electro-physiologically isolate a PV ostium <NUM> tissue in left atrium <NUM> of heart <NUM>.

Once distal end 22a of shaft <NUM> has reached the target location, physician <NUM> retracts sheath <NUM> and expands balloon <NUM>, typically by pumping saline into balloon <NUM>. Physician <NUM> then manipulates shaft <NUM> such that electrodes <NUM> disposed on the balloon <NUM> catheter engage an interior wall of a PV ostium <NUM> to perform electrophysiological sensing, and/or apply IRE and/or RF ablation via electrodes <NUM> to ostium <NUM> tissue.

As seen in inset <NUM>, and in more detail in <FIG>, expandable balloon <NUM> comprises multiple equidistant smooth-edge electrodes <NUM>. A transparent membrane <NUM> of balloon <NUM> enables optical detection of contact with tissue, as described in <FIG>. Due to the flattened shape of the distal portion of balloon <NUM>, the distance between adjacent electrodes <NUM> remains approximately constant even where electrodes <NUM> cover the distal portion. Balloon <NUM> configuration, when used for IRE, therefore allows more effective electroporation (e.g., with approximately uniform electric field strength) between adjacent electrodes <NUM> while the smooth edges of electrodes <NUM> minimize unwanted thermal effects.

In the context of the present disclosure and in the claims, the term "approximately" for any numerical values or ranges indicates a suitable dimensional tolerance that allows the part or collection of components to function for its intended purpose as described herein.

The proximal end of catheter <NUM> is connected to a console <NUM> comprising an IRE pulse generator <NUM> configured to apply the IRE pulses between adjacent electrodes <NUM>. The electrodes are connected to IRE pulse generator <NUM> by electrical wiring running in shaft <NUM> of catheter <NUM>. An optical tissue-contact detection module <NUM> of console <NUM> is used with balloon <NUM>, as described in <FIG>.

An optical fiber (seen in <FIG>) runs inside shaft <NUM> and is coupled at its proximal end to module <NUM>. A distal end of the fiber includes a coupler (seen in <FIG>) to emit the transmitted light and to couple the return light into the fiber.

Console <NUM> comprises a processor <NUM>, typically a general-purpose computer, with suitable front end and interface circuits <NUM> for receiving signals from catheter <NUM> and from external electrodes <NUM>, which are typically placed around the chest of patient <NUM>. For this purpose, processor <NUM> is connected to external electrodes <NUM> by wires running through a cable <NUM>.

During a procedure, system <NUM> can track the respective locations of electrodes <NUM> inside heart <NUM>, using the Active Current Location (ACL) method, provided by Biosense-Webster (Irvine California), which is described in <CIT>.

In other embodiments, physician <NUM> can modify, from a user interface <NUM>, any of the parameters, such as a wavelength, used by module <NUM>. User interface <NUM> may comprise any suitable type of input device, e.g., a keyboard, a mouse, a trackball, among others.

Processor <NUM> is typically programmed in software to carry out the functions described herein, including analyzing signals acquired by module <NUM>, to indicate an occurrence of membrane <NUM> contact with tissue. 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>, which enables processor <NUM> to perform the disclosed steps, as further described below.

<FIG> is a schematic, pictorial illustration of transparent balloon catheter <NUM> and of the contact detection module <NUM> of <FIG>, in accordance with an embodiment of the invention. The description below refers to balloon <NUM>, but the techniques described below may be applied, mutatis mutandis, to any catheter having other types of expandable frames, such as, but not limited to, a basket catheter.

Balloon <NUM> comprises transparent membrane <NUM> with electrodes <NUM> disposed on the surface of membrane <NUM>. In some embodiments, when placed in contact with tissue of heart <NUM>, electrodes <NUM> are configured to sense intracardiac electrical signals from the tissue and/or to ablate tissue.

In some embodiments, electrodes <NUM> are configured to apply, to the tissue, ablation pulses received from IRE generator <NUM> and controlled by processor <NUM> and/or by physician <NUM>, as described in <FIG> above.

In the shown embodiment, catheter <NUM> further comprises an optical fiber <NUM>, which runs in shaft <NUM> and ends within the internal volume of balloon <NUM> with an optical coupler <NUM>. Light emitted by coupler <NUM> propagates inside a saline solution used for inflating balloon <NUM> and interacts with media external to membrane <NUM>, such as with blood and/or wall tissue (seen in <FIG>).

The light emitted by coupler <NUM> is generated by an optical source (e.g., an LED) <NUM> inside unit <NUM>, and transmitted to fiber <NUM> using a circulator <NUM>. A return light is transmitted by circulator <NUM> to a photodetector <NUM>. Using a circulator therefore provides separation of the incident light from the return light, which enables the detection of changes, even slight ones, in the intensity of the return light, due to physical contact of transparent membrane <NUM> with wall tissue.

Returned light measured by photodetector <NUM> are conveyed as an electrical signal to processor <NUM> for the processor to perform the analysis required to determine the occurrence of the membrane contact with wall tissue, as described above.

The configuration shown in <FIG> is provided by way of example. The principles described herein may similarly be applied to other types of ablation catheters, such as a basket-type distal end having a transparent membrane fitted to its expandable frame. Various types of couplers, such as those corrugated to emit in several directions, or having surface roughness to scatter light, may also be used.

<FIG> is a schematic, pictorial illustration of a fiber grating coupler <NUM> inside transparent membrane <NUM> of balloon catheter <NUM> of <FIG>, in accordance with an embodiment of the invention. As seen, coupler <NUM> is patterned on optical fiber <NUM> at a distal end of fiber <NUM>, with fiber <NUM> ending with an opaque termination, to minimize a reflected light.

Proper selection of coupler <NUM> parameters can make it highly efficient. Specifically, the coupling coefficient of the grating can be maximized by adjusting the groves and length of the grating. In this way, a substantial fraction (e.g., ><NUM>%) of the incident light intensity can be coupled out to interact with surrounding media.

Directions at which light is coupled by coupler <NUM> out into a surrounding media <NUM>, and from which interacted light is coupled back into fiber <NUM>, are defined with angles θm given by the grating equation: <MAT> where n<NUM> is the media refractive index (e.g., n<NUM> is approximately <NUM> for saline solution media), neff is the effective refraction index (e.g., approximately <NUM>) of the fiber guided light of peak intensity wavelength λ<NUM> (e.g., <NUM> red light), and Λ is the period of the grating (e.g., several microns). Selecting Λ ≫ λ<NUM> ensures that there are many diffraction orders that cover a wide area of the membrane. Alternatively, a smaller period Λ (e.g., Λ ≧ λ<NUM>) may be selected, to cover, for example, with few diffraction orders, a selected perimeter strip of the membrane where contact determination is most important.

The configuration shown in <FIG> is provided by way of example. Other embodiments may induce more uniform emission of light over membrane <NUM> in other ways (e.g. a multiperiod grating or roughening).

<FIG> is a flow chart that schematically illustrates a method for detecting tissue contact with transparent balloon catheter <NUM> of <FIG>, in accordance with an unclaimed embodiment of the present invention. The algorithm, according to the presented embodiment, carries out a process that begins when physician <NUM> navigates balloon catheter <NUM> to a target tissue location in an organ of a patient, such as at PV ostium <NUM>, using, for example, electrodes <NUM> as ACL sensing electrodes, and bringing membrane <NUM> of expanded balloon <NUM> into contact with ostium tissue, at catheter placement step <NUM>.

In the process, unit <NUM> transmits light, which is emitted inside the cavity using coupler <NUM> (seen in <FIG>), to interact with surrounding media, possibly including wall tissue in contact with membrane <NUM>, at transmitted light emission step <NUM>.

At an acquisition step <NUM>, unit <NUM> acquires and measures a return light from surrounding media, possibly including wall tissue in contact with membrane <NUM>.

At a checking step <NUM>, processor <NUM> checks if a change of intensity of the return light occurred, e.g., to a degree indicative of a contact.

If the answer is no, the processor issues an indication of insufficient contact made with wall tissue (<NUM>), for example as a textual message on a display, and the process returns to step <NUM>.

If the answer is yes, the processor issues an indication of a sufficient contact made with wall tissue (<NUM>). In an optional embodiment, the processer may further issue a notice that the balloon is in position for ablation (<NUM>).

Although the embodiments described herein mainly address cardiac applications, the methods and systems described herein can also be used in other medical applications, such as in neurology and otolaryngology.

Claim 1:
A medical system (<NUM>), comprising:
a catheter (<NUM>), comprising a distal-end assembly for performing a medical operation on tissue in a cavity of an organ of a patient, the distal-end assembly comprising an optical fiber (<NUM>) configured to guide transmitted light to interact with the tissue of the cavity, and to guide returned light that interacted with the tissue;
a light source (<NUM>) configured to produce the transmitted light;
a detector (<NUM>) configured to measure the returned light;
a circulator (<NUM>) configured to couple the transmitted light from the light source to the optical fiber, and to couple the returned light from the optical fiber to the detector; and
a processor (<NUM>), configured to identify a contact of the distal-end assembly with the tissue based on the returned light measured by the detector, and to indicate the identified contact to a user, wherein the processor is configured to identify the contact based on a change in measured intensity of the returned light relative to a reference value for the intensity of the returned light while the distal-end assembly is not in contact with the tissue.