Patent ID: 12186013

DETAILED DESCRIPTION OF EMBODIMENTS

Overview

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 (e.g., 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.

In an embodiment, a system is provided that includes (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.

System Description

FIG.1is a schematic, pictorial illustration of a catheter-based diagnostics and/or ablation system20comprising a transparent balloon catheter40, in accordance with an embodiment of the present invention. System20comprises a catheter21, wherein a shaft22of the catheter is inserted by a physician30through the vascular system of a patient28through a sheath23. The physician then navigates a distal end22aof shaft22to a target location inside a heart26of the patient.

In the embodiment described herein, catheter21may 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 ostium51tissue in left atrium45of heart26.

Once distal end22aof shaft22has reached the target location, physician30retracts sheath23and expands balloon40, typically by pumping saline into balloon40. Physician30then manipulates shaft22such that electrodes50disposed on the balloon40catheter engage an interior wall of a PV ostium51to perform electrophysiological sensing, and/or apply IRE and/or RF ablation via electrodes50to ostium51tissue.

As seen in inset25, and in more detail inFIG.2, expandable balloon40comprises multiple equidistant smooth-edge electrodes50. A transparent membrane44of balloon40enables optical detection of contact with tissue, as described inFIG.2. Due to the flattened shape of the distal portion of balloon40, the distance between adjacent electrodes50remains approximately constant even where electrodes50cover the distal portion. Balloon40configuration, when used for IRE, therefore allows more effective electroporation (e.g., with approximately uniform electric field strength) between adjacent electrodes50while the smooth edges of electrodes50minimize 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 catheter21is connected to a console24comprising an IRE pulse generator38configured to apply the IRE pulses between adjacent electrodes50. The electrodes are connected to IRE pulse generator38by electrical wiring running in shaft22of catheter21. An optical tissue-contact detection module48of console24is used with balloon40, as described inFIG.2.

An optical fiber (seen inFIG.2) runs inside shaft22and is coupled at its proximal end to module48. A distal end of the fiber includes a coupler (seen inFIG.2) to emit the transmitted light and to couple the return light into the fiber.

Console24comprises a processor41, typically a general-purpose computer, with suitable front end and interface circuits37for receiving signals from catheter21and from external electrodes49, which are typically placed around the chest of patient28. For this purpose, processor41is connected to external electrodes49by wires running through a cable39.

During a procedure, system20can track the respective locations of electrodes50inside heart26, using the Active Current Location (ACL) method, provided by Biosense-Webster (Irvine California), which is described in U.S. Pat. No. 8,456,182, whose disclosure is incorporated herein by reference.

In other embodiments, physician30can modify, from a user interface47, any of the parameters, such as a wavelength, used by module48. User interface47may comprise any suitable type of input device, e.g., a keyboard, a mouse, a trackball, among others.

Processor41is typically programmed in software to carry out the functions described herein, including analyzing signals acquired by module48, to indicate an occurrence of membrane44contact 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, processor41runs a dedicated algorithm as disclosed herein, including inFIG.4, which enables processor41to perform the disclosed steps, as further described below.

Detecting Tissue Contact with a Balloon Catheter Using Optical Measurements

FIG.2is a schematic, pictorial illustration of transparent balloon catheter40and of the contact detection module48ofFIG.1, in accordance with an embodiment of the invention. The description below refers to balloon40, 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.

Balloon40comprises transparent membrane44with electrodes50disposed on the surface of membrane44. In some embodiments, when placed in contact with tissue of heart26, electrodes50are configured to sense intra-cardiac electrical signals from the tissue and/or to ablate tissue.

In some embodiments, electrodes50are configured to apply, to the tissue, ablation pulses received from IRE generator38and controlled by processor41and/or by physician30, as described inFIG.1above.

In the shown embodiment, catheter40further comprises an optical fiber60, which runs in shaft22and ends within the internal volume of balloon40with an optical coupler66. Light emitted by coupler66propagates inside a saline solution used for inflating balloon40and interacts with media external to membrane44, such as with blood and/or wall tissue (seen inFIG.1).

The light emitted by coupler66is generated by an optical source (e.g., an LED)202inside unit48, and transmitted to fiber60using a circulator204. A return light is transmitted by circulator204to a photodetector206. 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 membrane44with wall tissue.

Returned light measured by photodetector206are conveyed as an electrical signal to processor41for the processor to perform the analysis required to determine the occurrence of the membrane contact with wall tissue, as described above.

The configuration shown inFIG.2is 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.

A Balloon Catheter Using an Optical Grating Coupler

FIG.3is a schematic, pictorial illustration of a fiber grating coupler366inside transparent membrane44of balloon catheter40ofFIG.1, in accordance with an embodiment of the invention. As seen, coupler366is patterned on optical fiber360at a distal end of fiber360, with fiber360ending with an opaque termination, to minimize a reflected light.

Proper selection of coupler366parameters 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., >30%) of the incident light intensity can be coupled out to interact with surrounding media.

Directions at which light is coupled by coupler366out into a surrounding media300, and from which interacted light is coupled back into fiber360, are defined with angles □mgiven by the grating equation:

sin⁡(θm)=1n0⁢(neff-m⁢λ0Λ),m=1,2,3⁢…
where n0is the media refractive index (e.g., n0is approximately 1.33 for saline solution media), neffis the effective refraction index (e.g., approximately 1.5) of the fiber guided light of peak intensity wavelength λ0(e.g., 630 nm red light), and Λ is the period of the grating (e.g., several microns). Selecting Λ>>λ0ensures that there are many diffraction orders that cover a wide area of the membrane. Alternatively, a smaller period Λ (e.g., Λ≥λ0) 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 inFIG.3is provided by way of example. Other embodiments may induce more uniform emission of light over membrane44in other ways (e.g. a multiperiod grating or roughening).

Method of Detecting Tissue Contact with a Balloon Catheter Using Optical Measurement

FIG.4is a flow chart that schematically illustrates a method for detecting tissue contact with transparent balloon catheter40ofFIG.1, in accordance with an embodiment of the present invention. The algorithm, according to the presented embodiment, carries out a process that begins when physician30navigates balloon catheter40to a target tissue location in an organ of a patient, such as at PV ostium51, using, for example, electrodes50as ACL sensing electrodes, and bringing membrane44of expanded balloon40into contact with ostium tissue, at catheter placement step402.

In the process, unit48transmits light, which is emitted inside the cavity using coupler360(seen inFIG.3), to interact with surrounding media, possibly including wall tissue in contact with membrane44, at transmitted light emission step404.

At an acquisition step406, unit48acquires and measures a return light from surrounding media, possibly including wall tissue in contact with membrane44. At a checking step408, processor41checks 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 (410), for example as a textual message on a display, and the process returns to step402.

If the answer is yes, the processor issues an indication of a sufficient contact made with wall tissue (412). In an optional embodiment, the processer may further issue a notice that the balloon is in position for ablation (414).

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.

It will thus be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art. Documents incorporated by reference in the present patent application are to be considered an integral part of the application except that to the extent any terms are defined in these incorporated documents in a manner that conflicts with the definitions made explicitly or implicitly in the present specification, only the definitions in the present specification should be considered.