BR112018001899B1 - RADIOFREQUENCY ABLATION CATHETER WITH OPTICAL TISSUE EVALUATION - Google Patents

Abstract

RADIOFREQUENCY ABLATION CATHETER WITH OPTICAL TISSUE EVALUATION. Systems and methods for performing ER ablation while monitoring the procedure using low coherence interferometry (LCI) data are described. A catheter includes a distal section, a proximal section, a multiplexer, and a sheath attached between the distal section and the proximal section. The distal section includes several interlocking optical ports configured to transmit exposure radiation toward a sample and receive radiation that has been reflected or scattered from the sample. The interconnected optical ports are formed on a substrate having rigid sections and flexible sections arranged around the distal section. A support holds the interconnected optical elements in a fixed spatial relationship.

Description

FUNDAMENTALS

[001] This order claims priority over order No. of Série 62/198,591 filed on July 29, 2015, which is hereby incorporated by reference in its entirety.

Field

[002] Embodiments of the invention relate to designs and methods of using an RF ablation catheter along with optical tissue inspection. Fundamentals

[003] RADIOFREQUENCY (RF) ablation is a medical technique to produce tissue necrosis. It is used to help treat different pathologies, including cancer, Barrett's esophagus, or cardiac arrhythmias, among others. Application of alternating current with an oscillating frequency above several hundred kHz prevents stimulation of excitable tissue while providing heat via the Joule effect. The increase in tissue temperature causes the denaturation of biological molecules, including proteins such as collagen. Traditionally, RF ablation is done by placing an external electrode on the patient's body and applying an alternative potential to the tip of a catheter that is placed in contact with the tissue to be treated inside the patient's body. The ablation effect depends on several factors, including applied electrical energy, quality of electrical contact, local tissue properties, presence of blood flow near the tissue surface, and effect of irrigation. Due to the variability of these parameters, it is difficult to obtain consistent results.

[004] In fact, this procedure has shown only limited effectiveness when used in atrial fibrillation, with individual success rates heavily dependent on the skill and ability of the clinician performing the same. Even in qualified centers, in the acute phase after ablation, successful treatment rates rise up to 80%, while recurrences in the one-year follow-up period can reach 20%. Some factors associated with recurrent cases are discontinuous ablation lines and incomplete wall ablation. Incomplete ablation that results in edema rather than complete necrosis cannot be correctly identified with current tools.

[005] Another problem with catheter ablation is the long intervention times that are required in point-to-point procedures in the atrium. In these cases, continuous lines are created in a predefined pattern around anatomical structures to achieve the desired electrical isolation effect. Since the ablation is done locally, a large number of individual lesions are commonly concatenated. Ensuring the continuity of such a pattern in a beating heart requires painstaking work and attention. Since the procedure is often performed with the support of fluoroscopy, it can represent a significant radiation dose for both the clinician and the patient.

BRIEF SUMMARY

[006] The use of point-to-point RF ablation to help mitigate the effects of atrial fibrillation is improved by providing direct and immediate information about lesion transmurality, lesion continuity, and total energy delivered to the tissue being ablated. In the embodiments presented here, systems and methods for performing RF ablation while monitoring the procedure using low coherence interferometry (LCI) data are described.

[007] In one embodiment, a catheter includes a distal section, a proximal section, a multiplexer, and a sheath coupled between the distal section and the proximal section. The distal section includes one or more electrodes, a plurality of optical ports, and a holder. The one or more electrodes are configured to apply RF energy to a portion of a sample in contact with the one or more electrodes, such that the portion of the sample is ablated. The plurality of interconnected optical ports are configured to transmit one or more beams of exposure radiation away from the distal section of the catheter and receive one or more beams of scattered radiation that have been reflected or scattered from the sample, wherein the plurality of interconnected optical ports are formed on a substrate with rigid sections and flexible sections. The support is configured to hold the optical elements interconnected in a fixed spatial relationship. The multiplexer is configured to split the one or more exposure radiation beams from the source radiation beam and combine one or more scattered radiation beams.

[008] In another embodiment, a catheter includes a distal section, a proximal section, a multiplexer, and a sheath coupled between the distal section and the proximal section. The distal section includes one or more electrodes configured to apply RF energy to a portion of a sample in contact with the one or more electrodes, such that the portion of the sample is ablated. The distal section also includes a plurality of optical elements that transmit one or more beams of exposure radiation away from the distal section of the catheter and receive one or more beams of scattered radiation that have been reflected or scattered from the sample. The proximal section includes an optical source that generates a source beam of radiation and a detector that generates depth-resolved optical data associated with one or more beams of scattered radiation. The multiplexer generates one or more exposure radiation beams from the radiation source beam.

[009] In another embodiment, a catheter includes a distal section, a proximal section, a processing device, and a sheath coupled between the distal section and the proximal section. The distal section includes one or more electrodes configured to apply RF energy to a portion of a sample in contact with the one or more electrodes such that the portion of the sample is ablated. The distal section also includes a plurality of optical elements configured to transmit one or more beams of exposure radiation away from the distal section of the catheter and receive one or more beams of scattered radiation that have been reflected or scattered from the sample. The proximal section includes an optical source configured to generate a radiation source beam and a detector configured to generate depth resolved optical data associated with one or more scattered radiation beams. The processing device updates a model of the sample's thermal properties based on at least the depth-resolved optical data.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[010] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments of the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the relevant art to make and use the invention.

[011] Figure 1 illustrates a catheter, according to one embodiment.

[012] Figures 2A-2B illustrate cross sections of a catheter, according to the modalities.

[013] Figures 3A - 3G show a distal end of a catheter, according to modalities.

[014] Figures 4A-4B show a distal end of a catheter, according to the embodiments.

[015] Figure 5 illustrates a block diagram of an LCI system, according to one embodiment.

[016] Figures 6A - 6B illustrate the polarization axes of the image capture light and a sample.

[017] Figure 7 shows an example of temperature distribution in a sample, according to a modality.

[018] Figure 8 shows an example of temperature distribution in a sample, according to a modality.

[019] Figure 9 displays optical results in view of tissue denaturation, according to one modality.

[020] Figure 10 represents a method, according to an embodiment.

[021] Figure 11 represents a method, according to another modality.

[022] Figure 12 represents a method, according to yet another embodiment.

[023] Figure 13 illustrates an example of a useful computer system to implement various modalities.

[024] Embodiments of the present invention will be described with reference to the accompanying drawings.

DETAILED DESCRIPTION

[025] While specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. One skilled in the relevant art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the present invention. It will be apparent to one skilled in the relevant art that this invention can also be employed in a variety of other applications.

[026] It should be noted that references in the specification to "1 embodiment", "one embodiment", "one exemplary embodiment", etc., indicate that the embodiment described may include a particular feature, structure or feature, but each embodiment may not necessarily include the particular feature, structure or feature. Furthermore, such phrases do not necessarily refer to the same modality. Furthermore, when a particular feature, structure or feature is described in connection with an embodiment, it would be within the knowledge of one skilled in the art to effect such feature, structure or feature in connection with other embodiments described or not explicitly described.

[027] It should be noted that although this application may specifically refer to cardiac ablation, the modalities described here may also target other pathologies. The principles of using RF energy to treat other conditions are similar and therefore the techniques used to apply RF energy are similar.

[028] Embodiments of a catheter that combine RF ablation with LCI are described here to provide improved control during the ablation procedure. Furthermore, methods for combining LCI information with a computational model of heat transfer allow estimating the energy distribution and temperature distribution in the tissue under ablation. These methods can be implemented by a computing device to provide signal/image processing that feeds LCI information into a given computational model. The model, or any output from the model, can be provided to a user of the catheter, such as a physician or technician. Alternatively or additionally, any aspect of the model can be used to provide automatic control over the ablation process using, for example, a feedback loop. In some embodiments, the catheter further includes one or a combination of pressure, temperature, position or shape sensors. Additional subsystems, such as an irrigation system or impedance measurement tools, can be included in the catheter. Although the embodiments described herein describe the use of an RF ablation catheter, other ablation techniques can also be used without departing from the scope or spirit of the invention, such as, for example, laser ablation.

[029] Here, the terms "electromagnetic radiation", "light" and "radiation beam" are used to describe the same electromagnetic signals that propagate through the various elements and systems described. Catheter modalities

[030] Figure 1 illustrates a catheter 100 according to one embodiment. Catheter 100 includes a proximal portion 102, a distal portion 104, and a sheath 106 coupled between the proximal portion 102 and the distal portion 104. In one embodiment, the sheath 106 includes one or more radio-opaque markers for navigational purposes. In one embodiment, the catheter 100 includes a communication interface 110 between the catheter 100 and a processing device 108. The communication interface 110 can include one or more wires between the processing device 108 and the catheter 100. In other examples, the communication interface 110 is an interface component that enables wireless communication, such as Bluetooth, WiFi, cellular, etc. The communication interface 110 can communicate with one or more transceiver elements located within the proximal portion 102 or distal portion 104 of the catheter 100.

[031] In one embodiment, the sheath 106 and the distal part 104 are disposable. As such, the proximal part 102 can be reused by attaching a new sheath 106 and proximal part 104 each time a new procedure must be performed. In another embodiment, the proximal portion 102 is also disposable.

[032] The proximal part 102 can house various electrical and optical components used in the operation of the catheter 100. For example, a power supply can be included in the proximal part 102 to apply RF energy to an electrode located in the distal part 104 for tissue ablation. The power supply can be designed to generate an alternating current at frequencies of at least between 350 and 500 kHz. As such, one or more conductive wires (or any electrical transmission medium) may lead from the power supply to the distal portion 104 within the sheath 106. Additionally, the proximal portion 102 may include an optical source for generating a beam of radiation. The optical source can include one or more laser diodes or light emitting diodes (LEDs). The beam of radiation generated by the optical source may have a wavelength within the infrared range. In one example, the radiation beam has a central wavelength of 1.3 µm. The optical source can be designed to produce a beam of radiation at just a single wavelength, or it can be a swept source and designed to produce a range of different wavelengths. The generated radiation beam can be guided to the distal portion 104 through an optical transmission medium connected between the proximal portion 102 and the distal portion 104 within the sheath 106. Some examples of optical transmission means include single-mode and multimode optical fibers and integrated optical waveguides. In one embodiment, the electrical transmission measurement and the optical transmission measurement are provided by the same hybrid medium that allows electrical and optical signal propagation.

[033] In one embodiment, the proximal portion 102 includes one or more components of an interferometer for performing LCI using light generated from the optical source. Further details of the LCI system are discussed with reference to Figure 5. Due to the nature of interferometric data analysis, in one embodiment, the optical transmission medium used to guide light to and from distal end 104 does not affect the state and degree of polarization of the light. In another embodiment, the optical transmission medium affects the polarization in a constant and reversible manner.

[034] The proximal portion 102 may include additional interface elements with which a user of the catheter 100 can control the operation of the catheter 100. For example, the proximal portion 102 may include a deflection control mechanism that controls a deflection angle of the distal portion 104. The deflection control mechanism may require a mechanical movement of an element in the proximal portion 102, or the deflection control mechanism may use electrical connections to control the movement of the distal portion. 104. Proximal portion 102 may include various buttons or switches that allow a user to control when RF energy is applied to distal end 104, or when beams of radiation are transmitted from distal end 104, allowing acquisition of optical data.

[035] The distal part 104 includes one or more external electrodes for ablation, according to an embodiment. For simplicity, in the remainder of the description, it is assumed that only one ablation electrode is present. Distal portion 104 also includes a plurality of optical sight ports. In one embodiment, one or more of the optical sight ports are machined into each of the or more electrodes.

[036] The electrode used for ablation is in electrical connection with at least one cable that runs along the length of the sheath 106. Optical vision ports are distributed on the outside of the distal part 104, resulting in a plurality of display directions, according to one embodiment. In one embodiment, each of the multiple display directions is substantially non-coplanar. The optical sight ports can also be designed with irrigation functionality to cool the distal portion 104 and surrounding tissue from overheating during ablation. More details on the design of the distal portion 104 are discussed with reference to Figures 3A - 3G and 4A - 4B.

[037] Figures 2A and 2B illustrate cross-sectional views of the sheath 106, according to the embodiments. The sheath 106 may include all elements interconnecting the proximal part 102 with the distal part 104. The sheath 106a illustrates an embodiment that houses an irrigation channel 202, RF conductive means 204, deflection mechanism 206, electrical connections 208 and optical transmission means 210. Figure 2A illustrates a protective cover 212 wrapped around the electrical connections 208 and optical transmission means 210. Electrical connections 208 may be used to provide signals to optical modulation components located in the distal portion 104. One or more optical transmission means 210 guide light generated from the optical source (exposure light) toward the distal portion 104, while another subset of optical transmission means 210 guide light returning from the distal portion 104 (scattered or reflected light) back to the proximal portion 102. In another example, the same one or more means Optical Transmitters 210 guide light in both directions.

[038] The irrigation channel 202 can be a hollow tube used to guide the cooling fluid to the distal part 104. The irrigation channel 202 can include heating and/or cooling elements disposed along the channel to affect the temperature of the fluid. In another embodiment, the irrigation channel 202 can also be used as an avenue for sucking flow that surrounds the distal portion 104 back to the proximal portion 102.

[039] The RF conductive means 204 can be a wire or cable used to supply RF energy to the ablation electrode located in the distal part 104. The deflection mechanism 206 can include electrical or mechanical elements designed to provide a signal to the distal part 104 in order to change an angle of deflection of the distal part 104. The deflection system allows the orientation of the distal part 104 through the action of a mechanical control placed in the proximal part 1 02, according to a modality. This system can be based on a series of aligned and uniformly spaced cuts in the sheath 106 intended to provide the unidirectional deflection of the distal part 104, in combination with a wire that connects the control of the deflection mechanism in the proximal part 102 with the tip of the catheter in the distal part 104. In this way, a certain movement of the proximal part can be projected towards the distal part. Other modalities that involve combining multiple control wires attached to the catheter tip may allow deflection of the catheter tip along different directions.

[040] Figure 2B illustrates a cross section of the sheath 106b. Sheath 106b represents an embodiment that has most of the same elements as sheath 106a of Figure 2A, except that there are no electrical connections 208. Sheath 106b can be used in situations where modulation (e.g., multiplexing) of the generated radiation beam is performed at proximal portion 102.

[041] Figures 3A to 3G illustrate views inside the distal part 104, according to various embodiments. For example, Figure 3A illustrates the distal portion 104a having a plurality of vision ports 302', a plurality of optical fibers 304, an electrode 306 that also acts as an outer body of the distal portion 104, and one or more irrigation channels 310 located substantially at one end of the distal portion 104a. The plurality of viewports 302 may be arranged around the outside of the distal portion 104a in any pattern to achieve multiple views of a sample 308. RF energy may be applied to electrode 306 to ablate a portion of the sample 308. Electrode 306 may represent one or more electrodes at distal portion 104a. In one embodiment, optical fibers 304 can be any other type of waveguide structures, such as waveguides defined within an optical integrated circuit. In another embodiment, the optical fibers 304 can be waveguide structures defined on a flexible substrate. A multiplexing unit 312 may also be defined with the same flexible substrate that includes the waveguide structures.

[042] In Figures 3A and 3B, optical fibers 304 are used in each of the multiple viewing ports 302 to transmit and receive light through each of the multiple viewing ports 302. Exposure light is transmitted through the viewing ports 302 away from the distal portion 104a and into the sample 308, while light that is scattered or reflected by the sample 308 is received through the viewing ports 302. vision port of the plurality of vision ports 302 may include more than one optical fiber, for example, a fiber bundle. The light generated from the optical source at the proximal portion 102 may be split between each of the vision ports 302 using the multiplexing unit 312. Alternatively, the multiplexing unit 312 may select one of the plurality of vision ports 302 for the light to travel to or from. Multiplexing unit 312 receives an incoming beam of radiation over optical transmission line 316. Optical transmission line 316 can include any number of optical transmission elements (e.g., optical fibers) and can be similar to optical transmission medium 210 of Figures 2A and 2B. Electrical wires 318 may be included to carry control signals to multiplexing unit 312 from proximal portion 102 of catheter 100.

[043] The multiplexing unit 312 may include associated electronics 314 that provide control signals to various modulation elements of the multiplexing unit 312. The multiplexing unit 312 may use any multiplexing method that allows separation of contributions from the light collected by the various viewports 302. One such multiplexing method is time-domain multiplexing, in which the multiplexing unit 312 alternates between different output waveguides in a controlled manner such that, at any given time, only one of the associated viewports 302 is active. Another suitable multiplexing method is frequency domain multiplexing, in which the light passing through each of the viewports 302 is modulated in such a way that the time-frequency behavior of signals corresponding to different viewports 302 can be differentiated by a processing device. Coherence domain multiplexing can also be used in the multiplexing unit 312, introducing a different group delay for the light passing through each viewport 302, so that signals corresponding to different viewports 302 appear in different coherence positions and can therefore be differentiated by a processing device. In one embodiment, these methods are not exclusive and can be combined to find the best design compromise. Some of the multiplexing methods, such as coherence domain multiplexing, do not require any electrical actuation of the multiplexing unit 312. Thus, in one embodiment, implementations based on coherence domain multiplexing do not require electrical transmission media for control signals.

[044] In one embodiment, the multiplexing unit 312 is produced on a silicon photonic optical chip using a network of thermoelectric optical switches. Other materials suitable for use in the multiplexing unit 312 include silicon nitride, silicon dioxide, oxynitride, lithium niobate, III-V semiconductor materials, silicon carbide, and optical grade polymers. Other modulation effects to support optical switching operation include electro-optical effect, charge carrier density effects, photomechanical effects, refractive index modulation based on liquid crystals, etc. The multiplexing function can also be achieved through microelectromechanical devices (MEMS) as miniaturization and packaging constraints can be met. The connections between the electrical wires 318 and the multiplexing unit 312 can be achieved by bonding or soldering individual wires, or through an intermediate substrate that allows for "flipchip" assembly in an individual or batch process. In one embodiment, this intermediate substrate is flexible.

[045] In one embodiment, the multiplexing unit 312 is manufactured on a flexible substrate. One process for forming the optical elements on a flexible substrate includes a substrate transfer post-processing step applied to Silicon on Insulator (SOI) chips or wafers, as described in more detail in Application Publication No. US 2013/0201485 the disclosure of which is hereby incorporated by reference in its entirety. In one embodiment, the resulting flexible device is thinner (< 100 µm) than the initial thickness (500-700 µm). The multiplexing unit 312 may be implemented by an optical integrated chip that is partially flexible. The plurality of waveguides 304 (e.g., optical fibers) are suitably flexible to reach the various vision ports 302 arranged around the distal portion 104a, in accordance with one embodiment. As illustrated in Figure 3C - 3G, the integrated optical chip can be formed from a series of interconnected rigid sections incorporated by flexible sections. The associated electronics 314 can be attached to the underside or top side of an integrated chip that includes the multiplexing unit 312. In another embodiment, both the multiplexing units 312 and the associated electronics 314 are disposed on a flexible substrate. In one example, the flexible substrate having the multiplexing unit 312 and associated electronics 314 is rolled into a cylindrical shape to fit the distal portion 104a of the catheter 100.

[046] As shown in Figure 3A, the distal portion 104a may include one or more irrigation channels 310 to supply fluid to a plurality of holes (not shown) on the outside of the distal portion 104a. Fluid supplied through irrigation channels 310 can be used for cooling during the ablation procedure. In other embodiments, irrigation channels 310 can be designed to deliver therapeutic fluids to sample 308.

[047] The distal portion 104a may also include a force sensor 317. In one embodiment, the force sensor 317 is designed to measure a force applied to the distal portion 104a during operation along one or more reference axes. Force sensor 317 may include a rigid element from the sheath (eg, a rigid wire) mechanically connected to one part of the sensor, while an outer electrode is connected to a different part of the sensor. The general assembly of the catheter and any mechanical fasteners acting between the lead 306 and the sheath must ensure sufficient voltage transfer to force sensor 317. In another embodiment, force sensor 317 can be a pressure sensor based on, for example, a strain gauge.

[048] The force sensor 317 can have its reading element defined on the same substrate as the multiplexing unit 312, according to one embodiment. The reading principle can be based on an interferometric analysis of voltage-related distance change, on a piezoelectric device, on a capacitance measurement, or on the basis of an electromagnetic measurement. According to one embodiment, the signals generated from the force sensor 317 propagate through additional cables, or optical transmission, passing through the sheath 106. Alternatively, the signals can propagate through the same electrical and optical paths used for the multiplexing unit 312 and its associated electronics 314. In the latter case, the multiplexed optical path and data path of force sensor 317 can be separated through a suitable signal multiplexing technique. Additionally, if the irrigation channels 310 are drilled at a low and constant flow, the pressure can be measured indirectly by adding a pressure transducer to the proximal portion 102 of the catheter 100.

[049] In one embodiment, a temperature sensor 319 can be included in the distal part 104a, measuring the temperature substantially at the tip of the catheter during operation. Temperature sensor 319 can be a thermocouple, an element with a known resistive dependence on temperature, an element in which an optical parameter changes with temperature, or any other type of temperature sensor. The temperature sensor 319 may be included as a defined element on the same substrate as the multiplexing unit 312. According to one embodiment, the signals generated from the temperature sensor 319 propagate via additional cables and/or optical transmission means traversing the sheath 106 or via the same electrical and optical paths used for the multiplexing unit 312 and its associated electronics 314. In the latter case, the multiplexed optical path and temperature sensor data paths 319 can be separated using a suitable signal multiplexing technique.

[050] Figure 3B illustrates another embodiment of the distal part, represented as distal part 104b. Distal portion 104b includes many of the same elements as described in distal portion 104a. However, the distal portion 104b does not include the multiplexing unit 312 and associated electronics 314. A fiber bundle 305 is used to supply light to the plurality of optical fibers 304 within the distal portion 104b. In a catheter embodiment that utilizes the distal portion 104b, a multiplexing unit may be located proximally 102 or external to the catheter 100 (such as, for example, with the processing device 108).

[051] In either embodiment of the distal portion 104 illustrated in Figures 3A and 3B, the plurality of viewports 302 may include one or more lenses and/or mirrors or similar optical elements designed to focus light passing through any one of the viewports 302. The material used within each viewport 302 is substantially transparent to the wavelength of light used for optical interrogation, in accordance with one embodiment. The optical element may be coated with an anti-reflective layer to minimize optical losses. Mirrors can be produced locally by selectively evaporating a layer of metal through a mask onto surfaces to be reflected and can be flat or provide a focusing function. The distal portion body 104 may be formed using injection molded plastic and designed to support the multiplexing unit housing 312. In one embodiment, the optical element used in the plurality of vision ports 302 includes gradient index lenses and/or lenses with tapered tips.

[052] In one embodiment, one or more of the plurality of viewports 302 include a scanning element (not shown) that allows the beam of radiation exiting through the viewport 302 (the exposure radiation) to be swept in a given direction. The scanning element may include a microelectromechanical system (MEMS) component, or use electro-optical modulators to orient the output angle of the radiation beam from an associated viewport. More details and examples relating to scanning the radiation beams can be found in Application Publication No. US 2014/0078510, the description of which is incorporated herein by reference in its entirety.

[053] Figures 3C-3G illustrate additional embodiments of distal portion 104. These embodiments include many of the same elements as those depicted in Figures 3A and 3B unless otherwise noted. Each of the arrangements depicted in Figures 3C-3G illustrate distal parts that include a photonic integrated circuit with rigid sections joined by flexible sections. As illustrated in Figure 3C, a single substrate 320 can be used as the basis for all rigid beam input/output sections 322. Each rigid beam input/output section 322 is connected to at least one thin flexible section 324. The beam input/output sections 322 can provide optical ports and are optically and mechanically interconnected by flexible sections 324 to form the tip of the distal portion 104. The substrate 320 thus has a plurality of integral branches, with each branch including rigid beam input/output sections 322 interconnected by flexible sections 324. The branches bend around the tip of the distal end at the flexible sections 324. In this way, different shapes and arrangements can be accommodated. A bracket can be used to correct the spatial relationship of the branches and the corresponding rigid beam input/output sections 322.

[054] The flexible waveguides can extend through the flexible sections to optically connect the optical ports to the multiplexer 312. The flexible sections can be formed by partially removing substrate material to thin the substrate. A polyimide layer can be added to reinforce the tapered portion. The multiplexer 312 can be formed in a rigid section as shown in Figure 3C or implemented across the rigid and flexible sections. Although it is easier to form beam ports on rigid sections, beam ports can also be formed on flexible sections. In one embodiment, optocouplers, for example, 2x1 or 2x2, may be suitably dispersed across the rigid and/or flexible sections to form part of the multiplexer 312.

[055] The beam input/output sections 322 can produce focused or unfocused beams from optical ports. Furthermore, the beam may exit in the plane of a beam entry/exit section 322 (as shown in Figure 3D) or it may exit at an oblique angle to the plane of the beam entry/exit section 322, such as orthogonal to the plane (as shown in Figures 3E-3G). Radiation can then be received from the sample along the same optical path. Figures 3E - 3G illustrate various embodiments of a device designed to direct a beam of radiation. More details and alternative arrangements can be found in Order No. US 62/064,355, the disclosure of which is hereby incorporated by reference in its entirety.

[056] Figure 3D shows two beam input/output sections 322 optically and mechanically coupled by the flexible section 324. The waveguides 334 run along the plane of the substrate to optical ports 326. Optical ports 326 direct radiation beams 342 substantially parallel to the plane of propagation along each respective beam input/output section 322. The optical ports 326 may be aligned with the vision ports 302 to pass light to an area of interest. The beam input/output sections 322 are not limited to a single optical port, but can have a plurality of optical ports.

[057] Figures 3E - 3G illustrate the concept of directing a radiation beam at a substantially perpendicular angle to a substrate surface. However, the modalities differ in the placement and formation of certain elements. For example, Figure 3E illustrates a substrate 320 formed of a plurality of beam input/output sections 322 mechanically and optically coupled by flex section 324. The area below the flex section has been removed to provide flexibility. One or more waveguides 334 are formed in each of the beam input/output sections 322. The waveguides 334 may extend through the flexible section 324 to allow for optical coupling between the optical ports. Waveguide 334 includes a core layer 336 surrounded by cladding layers 338a and 338b. A reflector 340 is formed in the waveguide plane 334 and is designed to reflect a beam of radiation 342 towards the viewport 302.

[058] The substrate 320 can be any suitable material that allows surface and/or bulk micro-machining modeling steps to be carried out. In one example, substrate 320 is a crystalline material such as silicon, gallium arsenide, indium phosphide, etc. In other examples, substrate 320 is amorphous such as glass or polysilicon. The core layer 336 of the waveguide 334 may comprise a material having a higher refractive index than the cladding layers 338a and 338b in order to limit a beam of radiation propagating through the waveguide 334. The waveguide 334 may have a crystalline structure or be a polymer. Examples of waveguide 334 materials include, but are not limited to, silicon, silicon nitride, indium gallium arsenide, doped silicon, PMMA, Parylene, and SU-8. In one example, cladding layers 338a and 338b are silicon dioxide, while both substrate 320 and core layer 336 are silicon. Waveguide 334 can be a strip waveguide, crest waveguide, an optical fiber laid over the surface of substrate 320, or any other type.

[059] The reflector 340 can be formed by engraving the layers that form the waveguide 334, according to one embodiment. A wet anisotropic etching agent can be used to remove material along the crystal planes to form the surface of the reflector 340. The surface can be further smoothed by thermal oxidation of the silicon oxide removal process by rapidly exposing the reflector 340 to another chemical etching agent such as hydrofluoric acid (HF). Dry chemical etching techniques can also be employed to create the angled surface of reflector 340. For example, reactive ion etching (RIE) using a grayscale type mask to produce photoresist at different heights can be used to produce non-planar structures.

[060] The reflector 340 is placed at a short distance from one end of the waveguide 334, according to an embodiment. This distance cannot be too great, or else the beam of radiation exiting the waveguide 334 will spread too far and undesirable optical losses will occur. In this embodiment, both reflector 340 and waveguide 334 are modeled in plane on a first surface of substrate 320. Reflector 340 may be designed to have a surface that is angled. For example, the reflector 340 may have a surface that is angled at a substantially 45 degree angle to the first surface of the substrate 320. This angle causes the radiation beam to be directed at an angle that is substantially perpendicular to the surface of the substrate 320. In another example, the reflector 340 has a surface that is angled at a substantially 54.74 degree angle to the first surface of the substrate 320. 3E, light is reflected upward and away from rigid beam entry/exit sections 322 to viewport 302. Viewport 302 may include an optical focusing element, such as a lens, for focusing the diverging beam of radiation.

[061] Figure 3F shows an alternative arrangement that does not need an additional focusing element. Instead, an optical element 344 is disposed on the waveguide 334 and on an upper surface of the rigid beam input/output section 322, according to one embodiment. In this embodiment, optical element 344 is a lens. The lens can be designed to focus the radiation beam 342 or to collide the radiation beam 342. The optical element 344 can be fabricated using nanoprint lithography or standard lithography etching using a grayscale mask. Thermal reflux of a transparent polymer can also be used to form the curved lens shape. The optical element 344 can be fabricated using RIE directly on the substrate 320. The advantage of using RIE can be realized when the substrate material has a high refractive index (e.g., material such as silicon, InP, etc.), thus the performance of the lens is much less dependent on the refractive index of the surrounding medium. The curvature and position of the lens' focusing surface can be adjusted so that the focal point and focal length of the lens achieve the desired collimation or focusing performance. In one example, an intermediate polymer layer is introduced between the optical element 344 and the waveguide 334 to establish a lens working distance. Optical element 344 can be further coated with an anti-reflective dielectric battery to minimize light loss. Although the conveyor motion depicted has an optical element 344 on the same side of the substrate 320 as the waveguide 334, the waveguide 334 may be formed opposite the optical element 344 with an opening in the rigid beam entry/exit section 322 to allow radiation to pass through the substrate 320.

[062] A monolithic support 350 includes recesses 352 to physically retain and orient rigid beam input/output sections. 322. The cross-sectional view in Figure 3F illustrates how the substrate 320 can bend around the support 350. The support spatially secures the rigid beam entry/exit sections 322 around the tip of the distal end 104, and the flexible section 324 spans the portion of the support between the recesses 352. Although two entry/exit sections 322 are shown in detail, each of the cavities 352 would normally have an entry section /corresponding rigid beam output 322 therein. Additional slots may be provided in support 350 for flexible sections 324. Support 350 may alternatively be formed as a frame rather than a monolithic element.

[063] Figure 3G shows another alternative arrangement that includes a focusing element, thus alleviating the need for a focusing element in the view port 302. Instead of a refracting element shown in Figure 3F, the arrangement in Figure 3G includes the optical element 344 with a reflective coating 336. The reflective coating 336 can be formed on a parabolic surface of the optical element 344 to focus or collimate light from the waveguide 334. Optical element 344 and reflective coating 336 may be formed on rigid beam input/output section 322 as described above. Alternatively, reflective coating 336 can be formed on a parabolic surface formed within recess 352 of support 350, so that no additional optical element is needed. Reflective coating 336 can be designed for on-axis or off-axis reflection. For on-axis reflection, a substantially annular aperture may be formed in the beam entry/exit section 322 to allow the beam 342 to pass through the substrate 320 and around the flat reflector 340.

[064] Furthermore, the features described above in relation to Figures 3D-3G can be combined to provide multiple means of directing the radiation beam 342.

[065] Figure 4A illustrates an exterior view of the distal part 104, according to one embodiment. The plurality of viewing ports 302 can be located anywhere around the entire outer surface of the distal portion 104 to provide any number of angles for viewing a tissue sample (e.g., an atrial wall) around the distal portion 104. Additionally, the distal portion 104 can include a plurality of the openings 402 that are associated with the irrigation channels 310 illustrated in Figures 3A and 3B. Apertures 402 may also be placed anywhere around the outer surface of distal portion 104 and used to expel liquid into the area surrounding distal portion 104, or to draw liquid from the area surrounding distal portion 104.

[066] Figure 4B illustrates an exploded view of the distal part 104, according to one embodiment. The plurality of optical elements 404 can be located anywhere around the entire outer surface of a cap 410 to provide any number of angles for viewing a tissue sample (eg, an atrial wall) around the distal portion 104. The cap 410 is designed to fit around the holder 350 and the substrate 320. Rigid beam input/output sections 322 fit within recesses 352 of the bracket 350 Cover 410 fits over support 350 and substrate 320 and is secured by alignment and locking mechanisms 412 and 414. Recess 412 fits within indentation 414 to secure cover 410 to support 350 while allowing optical connection to proximal portion 102. When securing cover 410 to support 350, optical elements 404 are aligned with the optical output of the input/output sections. rigid beam 322. LCI System Modality

[067] Various embodiments of the present application include an LCI system integrated within the catheter 100 for optically interrogating the tissue surrounding the distal part 104. Figure 5 illustrates an example of an LCI system 501 for capturing an image of a sample 510, according to one embodiment. For example, sample 510 could be a portion of an atrial wall to be ablated. A delay unit 512 may include multiple light modulation elements. These modulation elements can perform phase and/or frequency modulation to counteract unwanted optical effects on the light, and select one or more sample depths 510 to be imaged. The use of the term "light" can refer to any band of the electromagnetic spectrum. In one embodiment, the term "light" refers to infrared radiation having a wavelength of about 1.3 µm.

[068] The LCI system 501 further includes an optical source 502, a splitting element 504, a sample arm 506, a reference arm 508 and a detector 514. In the shown embodiment, the delay unit 512 is located within the reference arm 508. However, it should be understood that the delay unit 512 may instead be located in the sample arm 506. Alternatively, various elements of the sample unit delay 512 can be present in both the sample arm 506 and the reference arm 508. For example, elements of the delay unit 512 that introduce a variable delay to the light can be located in the sample arm 506, while elements that modulate different polarization modes of light can be located in the reference arm 508. In one example, the sample arm 506 and the reference arm 508 are optical waveguides, such as patterned waveguides or fibers optics. In one embodiment, all components of the LCI 501 system are integrated into a flat light wave circuit (PLC). In another embodiment, at least the components within the delay unit 512 are embedded on the same substrate as a PLC. Other implementations can be considered as well, such as, for example, fiber optic systems, free space optical systems, photonic crystal systems, etc.

[069] It should be understood that the LCI system 501 may include any number of other optical elements not shown for reasons of clarity. For example, LCI system 501 may include mirrors, lenses, grids, dividers, micromechanical elements, etc., along the paths of sample arm 506 or reference arm 508.

[070] The splitting element 504 is used to direct the light received from the optical source 502 to the sample arm 506 and the reference arm 508. The splitting element 504 can be, for example, a bidirectional coupler, an optical splitter, or any other optical modulation device that converts a single beam of light into two or more beams of light.

[071] Light traveling down the sample arm 506 finally penetrates the sample 510. The sample 510 can be any sample suitable to be imaged, such as tissue. Light scatters and reflects from various depths within sample 510 and scattered/reflected radiation is collected back into sample arm 506. In another embodiment, scattered/reflected radiation is collected back into a waveguide other than the transmitting waveguide. The scan depth can be chosen via the delay imposed on the light within delay unit 512.

[072] The light within the sample arm 506 and the reference arm 508 is recombined before being received at the detector 514. In the embodiment shown, the light is recombined by the splitting element 504. In another embodiment, the light is recombined in a different optical coupling element than the splitting element 504. The detector 514 can include any number of photodiodes, charge coupling devices, and/or CMOS structures to transduce the received light into a signal electric. The electrical signal contains depth resolved optical data relating to sample 510 and may be received by a processing device for further analysis and signal processing procedures. As used herein, the term "depth resolved" defines data in which one or more portions of data relating to specific depths of a captured image sample can be identified.

[073] In one embodiment, optical source 502, detector 514 and delay unit 512 are located in the proximal part 102 of the catheter 100. The splitting element 504 and at least part of one or both of the sample arm 506 and the reference arm 508 can be located in the proximal part 102 or in the distal part 104 of the catheter 100. In another embodiment, all elements of the LCI system 501 are located in the distal portion 104 of catheter 100. Optical source 502 may include one or more light emitting diodes (LEDs) or laser diodes. For example, LEDs can be used when performing time-domain and/or spectral-domain analysis, while tunable lasers can be used to scan the wavelength of light over a range of wavelengths. In another embodiment, optical source 502 and detector 514 are located external to catheter 100, for example with processing device 108.

[074] The LCI 501 system is illustrated as an interferometer design similar to a Michelson interferometer, according to one embodiment. However, other interferometer designs are also possible, including Mach-Zehnder or Mireau interferometer designs. Example of Methods and Modes of Operation

[075] The catheter 100 can be used to perform ablation by applying high-frequency alternating current to the tissue in contact with the distal part 104 of the catheter 100. Oscillation frequencies ranging from 350 to 500 kHz can be used. It should be understood that other frequencies can also be used and that any frequencies above about 1 kHz rarely produce electrical stimulation of excitable cells. An adjustable power high frequency power source that supplies the RF energy to electrode 306 at distal portion 104 may be used. The underlying physics of heat transfer to tissue is based on a high electrical impedance of the tip-tissue interface. The impedance of this tissue-electrode interface, at the ablation frequency, can be substantially greater than that of the return electrode. For a given current delivered through the body, a larger voltage drop can be generated at this interface producing heat at the desired location. In this way, a small volume of tissue surrounding the tip of the catheter is ablated, instead of the entire volume of tissue from the tip of the catheter to the ground contact, which is normally placed on the patient's back during cardiac ablation treatment. By adjusting the RF power and the ablation time, the total energy delivered to the tissue can be precisely controlled. Other ablation techniques based on cryogenic or optical means (eg laser ablation) can also be used for the treatment of different pathologies.

[076] In embodiments where the optical multiplexing unit 312 in the catheter 100 uses time domain multiplexing, only a subset of the vision ports 302 in contact with tissue will be considered while the ablation is taking place, according to an embodiment. In this way, the line acquisition rate can be maximized for the active viewports during the ablation process. The LCI line sequence of the ablated region can be collected over a period of time. Signal processing algorithms can be used to monitor lesion progress by observing changes in the signal over time. Such algorithms may be executed by processing device 108. For example, an M-scan involves a repeated axial scan at the same physical location as a function of time. In particular, an M-scan representation can be constructed with the acquisition starting immediately before the delivery of RF energy. According to one embodiment, signal and image processing software running by processing device 108 receives timing information associated with application of RF energy by catheter 100. In this way, data can be collected only during times when tissue ablation is occurring.

[077] In one embodiment, signal and image processing software accounts for tissue birefringence. The birefringence of tissue fibers can be altered due to a number of potential factors outside of the ablation procedure. Connective biological fibers such as collagen are known to exhibit birefringent properties. When complete tissue necrosis is achieved by heat transfer, collagen fibers denature. This denaturation produces a loss of the birefringent behavior of these fibers. Irreversible denaturation of collagen fibers occurs at about 60°C. Cell death is caused by a combination of an applied supraphysiological temperature and its duration. However, a partial loss of birefringence may be indicative of partial tissue damage (edema), which may compromise the effectiveness of the procedure. In one example, at temperatures below 60°C, collagen denaturation caused by triphonic hydrogen bonds breaks down and can reversibly reduce birefringence. In other examples, the combination of exposure time and elevated temperature produces denaturation and cell death.

[078] The use of polarization-sensitive LCI (PS-LCI) techniques allows monitoring of birefringent changes in the tissue and therefore can lead to an estimate of the degree of denaturation induced in the tissue. In one embodiment, the signal and image processing software is capable of combining data on polarization-related tissue properties with structural data associated with a full range of depth-resolved optical data collected by the LCI system. Data regarding the polarization of tissue fibers can also be extracted from the depth resolved optical data. An image of the sample can be generated by a processing device based on the difference in the birefringent properties of various portions of the sample. For example, the birefringence exhibited by the ablated sample portion is different from the birefringence exhibited by non-abblated sample portions.

[079] Birefringent materials can be characterized by two orthogonal linear polarizations with a certain orientation. Each polarization has a different index of refraction, known as slow and fast axes. Figures 6A and 6B illustrate this concept, according to one embodiment. In Figure 6A, the distal portion 104 of a catheter is shown with light exiting from one of the plurality of viewports 302 onto the sample 308. In both Figures 6A and 6B, FAs and SAs represent the fast axis and slow axis, respectively, of the LCI system. FAt and SAt represent the fast axis and slow axis, respectively, associated with sample 308. Sample 308 may be, for example, a tissue sample.

[080] Tissue-specific contrast may depend on the magnitude of tissue birefringence as well as the orientation of the tissue birefringence axes (FAt and SAt) relative to the polarization state of the incident light. However, tissue birefringence axes can change over time due to catheter-generated stress and temperature. Furthermore, the polarization state of the incident light may change with time due to temperature and stress generated in the optical transmission medium during the image capture procedure. This forms an angular mismatch (θ in Figure 6B) between the incident light axes and the related axes associated with sample 308.

[081] In one embodiment, a correction module configured to correct the angular mismatch θ is implemented within the LCI system. The correction module can be implemented in hardware, for example with on-chip bias components. The on-chip components may form part of the delay unit 512 in the LCI system 501. In another example, the correction module may be implemented with fiber-based polarization controllers. In another example, the correction module may be implemented in software and executed by a computing device, such as processing device 108 in Figure 1.

[082] According to an embodiment, the correction module is designed to rotate the polarization state of the incident light in the range of π/2 radians while monitoring the birefringence of the backscattered sample signal. As a result of this swept polarization orientation, the polarization state exhibiting an optimal value (eg a maximum signal contrast) can be obtained and corrected. Alternatively, a continuous scan of the incident light polarization state can also be used in synchronization with optical data acquisition. thermal modeling

[083] The collected optical resolved depth data can also be used in a processing device to generate and/or improve a thermal model of heat dissipation within the ablated sample, according to an embodiment. The speed and extent of changes detected in the LCI signals are excellent indicators of thermal energy delivery to the tissue and can be quantified based on, for example, the biofuel model, as in equation 1 below.

[084] This equation represents the heat transfer in a biological sample using an external source. In this equation, p is the mass density, c is the specific heat, T is the temperature, k represents the thermal conductivity, q is the heat source (Joule effect), Qp is the convection heat loss, and Qw is the metabolic heat.

[085] According to one embodiment, changes in the polarization of light received from the sample can be linked to a specific temperature threshold in the tissue being ablated, which in turn can be linked to a defined denaturation process of the biomolecules. Based on the time to induce this process at a given distance from the ablation electrode and the general progression of the lesion over time and depth, a good assessment of energy transfer can be made.

[086] Figure 7 illustrates how heat is delivered to the tissue from a tip of the ablation catheter 702, according to one embodiment. The tip of the catheter 702 is brought into contact with a sample surface 704, for example a tissue interface, and RF energy is delivered to the sample to ablate a portion of the sample. A heat gradient generated by the delivery of RF energy is formed in the sample as represented by isothermal boundary areas 708a-c. For example, boundary area 708a may be associated with the warmer temperatures generated by the application of RF energy, while boundary areas 708b and 708c represent progressively cooler temperatures. Catheter tip 702 also includes a plurality of viewing ports, such as those previously described with reference to Figures 3A and 3B, that allow M scans 706a-c to be taken at different angles and/or locations within the sample, according to one embodiment. Each M-scan can be considered equivalent to the received scattered/reflected light returning from multiple depths within the sample.

[087] In one embodiment, the data received from the M scans 706a-c provide information on the denaturation process that occurs along each scanned line. For example, the data received from each M 706a-c scan can be used to generate and/or improve a thermal model of the heat distribution present in the sample.

[088] Figure 8 illustrates another example of how heat is delivered to tissue 804 from an ablation catheter tip 802 and monitored using four viewing ports (14). In one embodiment, the relative position of the catheter tip 802 is inferred by calculating the first reflection of light at each viewport (1-4) which defines a distance from the viewport to the tissue 804. This can provide an estimate of tissue contact and therefore an approximation of the impedance of the tissue-electrode interface. In one embodiment, distances d1, d2, d3 and d4 represent the first reflection and thus the distance from each viewport associated with tissue 804. The curves labeled t1 to t4 represent the denaturation temperature profile at times t1 to t4. In one embodiment, the illustrated curves obtained from each display (1-4) represent the variation of the phase/delay difference measured in PS-LCI with respect to time. Different decay rates are observed according to the direction of the M-scan coming from each of the viewports (14). These decay rates may also depend on irrigation, which cools the surface and leads to a more conical heat diffusion pattern. In one embodiment, correlating the information obtained by the PS-LCI signal from each viewport (1-4) provides spatial sampling of the isothermal line at which collagen denatures. By using the PS-LCI data, the dynamics of collagen denaturation, energy delivery and/or tissue ablation can be estimated.

[089] Figure 9 illustrates an example curve that represents the average phase/group delay obtained from the M-scans against the ablation time. Data regarding the change in certain parameters over time, such as those illustrated in Figure 9, can be used to generate and/or improve the thermal model of the sample during ablation.

[090] The thermal model can be presented to a catheter user to provide additional information about the ablation procedure. In another embodiment, data from this thermal model can be used to automatically control the ablation process. For example, the thermal model can be used to control a duty cycle of applied RF energy, or to turn off application of RF energy if the temperature rises above a threshold.

[091] General thermal properties of the tissue sample, including heat capacity and heat diffusivity, together with other heat transfer effects derived from the thermal model, such as convection near the surface, can be used to calculate more clinically relevant parameters, such as depth and width of the created lesion. The known thermal parameters of the fabric can be used to generate a baseline model of heat transfer in the fabric based on the finite element method or simple analytical relationships. Inputs to the model can then be further refined using information obtained from the resolved optical depth data collected by the LCI system. The thermal model outputs can be used to calculate a required treatment time on thicker samples where the LCI M-scans do not provide sufficient depth information. For example, to ensure direct transmurality, thermal model parameters can be used to optimize tissue heating close to sensitive structures, as well as provide an initial estimate of the lateral extent of the formed lesion. These model outputs can be presented to the user (eg on a display) or used to directly control the application of RF energy. A combination of information from LCI, the computational model, and other relevant information, such as catheter tip temperature or tissue-electro impedance, can be used to predict tissue temperature distribution during ablation and understand the kinetics of lesion growth.

[092] In one embodiment, two phases are distinguished when using the computational model along with the collected information: a phase where denaturation occurs within the axial penetration depth of LCI radiation, and a phase where denaturation occurs beyond the axial penetration limit. During the first phase, the time evolution of the isothermal line in which collagen birefringence is lost can be monitored together with the temperature of the catheter tip. In one embodiment, a processing device attached to the catheter takes advantage of this information to estimate parameters involved in heat transfer, such as thermal diffusivity, as well as to characterize irrigation effects, among others. Once these parameters have been defined, computational models can be used to predict the evolution of tissue ablation beyond the limit of axial penetration of LCI radiation. Information about impedance can also be correlated with previously collected data.

[093] The thermal model of the sample can also be reinforced through structural information about the sample. For example, such information can be obtained from preoperative magnetic resonance imaging (MRI) or computed tomography (CT) scans and, when appropriately combined with navigational information, can provide information about wall thickness, shape, composition, and tissue in close proximity to the distal portion of the catheter.

[094] Figure 10 illustrates an example of method 1000 for performing RF ablation during LCI data collection, according to an embodiment. Method 1000 can be performed by various catheter components 100 in conjunction with a processing device 08.

[095] At block 1002, a portion of a sample is ablated. Ablation can be due to the application of RF energy by an electrode at the distal end of a catheter, or through other ablation methods, such as laser ablation. The sample portion can be, for example, a portion of an atrial wall being ablated to help correct a cardiac arrhythmia.

[096] In block 1004, the sample's LCI optical data is collected while the ablation is taking place. LCI optical data may include data relating to the portion being ablated and/or portions of the sample not currently being ablated. Collection of optical LCI data may involve transmitting one or more beams of exposure radiation through correspondingly arranged apertures at a distal end of the catheter and receiving one or more beams of scattered or reflected radiation from the sample.

[097] In block 1006, depth-resolved optical data is generated based on the radiation beams received from the sample. For example, a detector can generate an electrical signal based on received radiation beams. The generated electrical signal can then be received by a processing device for analysis and further signal processing to perform certain actions and/or generate models based on the resolved depth optical data. For example, depth-resolved optical data can be used to determine a degree of ablation for the portion of the sample being ablated.

[098] In block 1008, a sample heat dissipation model is provided from the resolved depth optical data. The thermal model can either be generated or updated based on depth resolved optical data, such as data collected from multiple M-scans. General thermal properties of the tissue sample, including heat capacity and heat diffusivity, in conjunction with other heat transfer effects derived from the thermal model, such as convection near the surface, can be used to calculate more clinically relevant parameters, such as the depth and width of the created lesion, according to a modality. The thermal model can also be generated based on data other than the collected optical resolved depth data. For example, the temperature at the distal end of the catheter and/or impedance measured at the distal end of the catheter can be collected and used when generating the thermal model. In one embodiment, the thermal model can be used to monitor the tissue ablation process beyond the penetration range of LCI radiation. In another example, the heat dissipation model is used to avoid delivering too much RF energy that could result in perforation of the atrial wall, thus translating into serious complications for the patient during the procedure.

[099] In addition, the thermal model can be presented to a user or used to determine whether the user should be alerted in any way. For example, while the ablation procedure is taking place, if the temperature of the ablated region rises above a certain threshold as determined by the thermal model, a warning signal can be transmitted to the user. Examples of warning signals include sounding an audible warning, activating a light, or flashing a light. Tactile alerts can be emissions as well, such as a slight vibration in the portion of the catheter system being manually manipulated by the user. In another example, while the ablation procedure is taking place, if the temperature of a portion of the sample close to the portion being ablated rises above a given threshold, as determined by the thermal model, a warning signal may be transmitted to the user. Alternatively, the ablation procedure can be automatically controlled based on outputs from the thermal model.

[100] In another embodiment, the thermal model is associated with a predictive/adaptive controller to ensure safe delivery of RF energy. An adaptive controller can be used to directly control the parameters of the RF energy used for ablation based on the thermal model. In another embodiment, the predictive control model, neural networks, or genetic algorithms can be used to minimize a cost function defined in terms of patient safety and accurate energy delivery.

Catheter Navigation

[101] Depth-resolved optical data generated from the LCI system can also be used to assist in navigating the catheter to an ablation site, according to one modality. In one example, data collection can occur by switching between available viewports at the distal end of a catheter in a predefined or random manner. In another embodiment, the system can simultaneously monitor signals from different viewports at the distal end of the catheter. According to one embodiment, while the catheter is being navigated through a cardiac chamber, a processing device can be configured to use the optical data to monitor close proximity or tissue contact at one or more of the optical viewing ports. A significant change in amplitude of LCI scans is observable between blood, saline, and tissues to be ablated (such as the different layers of the atrial wall). Therefore, the processing device can be configured to characterize whether the sample being imaged from a given viewport is blood, saline, or tissue. The effective dispersion and scatter coefficient, which can be calculated from the resolved depth optical data, will vary between blood, saline, and tissues. For example, at a wavelength of 1.3 μm, the coefficient is around 8-10 mm-1 in the endocardial wall, around 15-20 mm-1 in blood, and can be considered negligible in saline solutions. The endocardial surface of the atrial wall additionally produces a reflection peak, followed by a rotation in the polarization signal. This characteristic signal can be used to assess tissue contact and distance to the atrial wall from any given viewport at the distal end of the catheter. Scans acquired sequentially for the same viewport can be compared over time. In one embodiment, this information can be used to help navigate the catheter by determining a distance between the distal end of the catheter and any perceived tissue.

[102] Additionally, the processing device can be configured to validate the assumption of continuous contact and stationary position relative to the tissue to be ablated during the ablation procedure. In one embodiment, validation is performed by checking for abrupt variations that may appear in the LCI signals and the polarization information, and by monitoring a distance to the first reflection typically appearing at the surface of the tissue wall. If slippage or loss of contact during ablation is detected, a notification to the user can be produced. Alternatively, a feedback control system can be implemented to stabilize the catheter during the ablation procedure.

[103] In one embodiment, the processing device utilizes two sources of information in order to assess tissue contact during the navigation phase, but other parameters resulting from the analysis of the LCI signals can be viewed, including those extracted using neural networks, small wave analysis, or others known to those skilled in the art. For example, the processing device can use LCI signal information as well as pressure sensor data (or data collected from an impedance sensor) to evaluate tissue contact. Given the fast line acquisition rate that is possible (several kilohertz), averaging, filtering, or other forms of signal blending can be used to increase image/signal quality. Furthermore, the acquired LCI signals can be accumulated to form an M-scan and this information presented to the active view port(s).

[104] Figure 11 illustrates another example method 1100 for navigating a catheter during LCI data collection, according to an embodiment. Method 1100 may be performed by various catheter components 100 in conjunction with processing device 108.

[105] In block 1102, optical LCI data from a sample around the catheter is collected. The sample may include blood, saline, and tissue from an atrial wall as the catheter is navigated through the heart chamber. Optical LCI data may include data relating to a portion of the sample being ablated and/or portions of the sample that should not be ablated. Collection of optical LCI data may involve transmitting one or more beams of exposure radiation through corresponding apertures disposed at a distal end of the catheter and receiving one or more beams of scattered or reflected radiation from the sample.

[106] In block 1104, depth resolved optical data is generated based on the radiation beams received from the sample. For example, a detector can generate an electrical signal based on received radiation beams. The generated electrical signal can then be received by a processing device for further signal analysis and processing to perform certain actions and/or generate models based on the resolved depth optical data.

[107] In block 1106, depth-resolved optical data is used to characterize the sample. For example, one or more parameters of the resolved depth optical data can be compared to determine whether the sample is blood, saline, or tissue. In another example, the electrical impedance of the sample can be calculated using a bipolar alternating current injection with a different frequency than that used for ablation. In one embodiment, a processing device is configured to run software to analyze the resolved depth optical data. Determining the sample type can be presented to a user of the catheter, used to generate a map or image of the area around the catheter, or used to directly aid in the navigation of the catheter. For example, the processing device may provide tissue type data, as extracted from the resolved depth optical data, to a navigation system configured to move the catheter through a patient's body. Information about tissue type and ablation results can be displayed on an anatomical map of the tissue to be ablated. These data can be useful to ensure the continuity of the lesion at the end of, or during, a procedure.

[108] At block 1108, a determination is made as to whether or not the sample is tissue. If the sample currently being analyzed is non-tissue, method 1100 repeats at each block 1102 or block 1104. When other LCI data around the catheter needs to be collected, a method 100 repeats at block 1102. Alternatively, a method 100 may repeat at block 1104, so that depth-resolved optical data can be generated and analyzed from a different portion of the LCI data already collected. For example, additional LCI data is collected from the area around the catheter (block 1102) only after all currently collected LCI data has been analyzed (block 1104). If the sample is determined to be fabric, method 1000 proceeds to block 1110.

[109] In block 1110, a distance between the tissue and the distal end of the catheter is determined. This determination can be made using a processing device configured to analyze the resolved depth optical data and calculate an approximation of the distance between the tissue and the distal end of the catheter. For example, a time of flight of light reflected from a tissue surface can be extracted from the depth-resolved optical data and used to determine distance. The distance information generated by the processing device can be displayed to the user to aid in navigation, or used to automatically control the movement of the catheter. Optical Coherence Tomography Image Capture

[110] In one embodiment, the processing device provides an additional mode in which information derived from the resolved depth optical data is used to determine the 3D spatial position and orientation of the catheter tip. The catheter can be swept through a portion of the sample while the LCI data is being collected, to provide spatially resolved data for 3D modeling. The processing device can be configured to accumulate the depth-resolved optical data associated with one or more LCI scans from the active optical view port, and arrange the data according to a spatial position of the catheter within one or more optical coherence tomography (OCT) images or 3D reconstructions. In one embodiment, the processing device adapts an LCI system scan rate and optical multiplexer function to match the variable lateral scan rate of the catheter. OCT images can be purely structural or can include information about tissue refractivity (eg, birefringence). These images can be helpful in ensuring lesion quality, continuity, and transmurality at the extremity of or during a procedure.

[111] Figure 12 illustrates another example method 1200 for collecting OCT images of a sample around a catheter. Method 1200 may be performed by various catheter components 100 in conjunction with processing device 108.

[112] In block 1202, optical LCI data from a sample around the catheter is collected. The sample may include blood, saline, and atrial wall tissue as the catheter is navigated through the heart chamber. Optical LCI data may include data relating to a portion of the sample being ablated and/or portions of the sample that should not be ablated. Collection of optical LCI data may involve transmitting one or more beams of exposure radiation through corresponding apertures disposed at a distal end of the catheter and receiving one or more beams of scattered or reflected radiation from the sample.

[113] At block 1204, the catheter is swept over a portion of the sample. According to one embodiment, the scan takes place while LCI data is being collected. Alternatively, the catheter itself can be substantially stationary while scanning elements located in the catheter's viewing ports cause exposure of light exiting the viewing ports to be scanned in a given direction.

[114] In block 1206, depth resolved optical data is generated based on the radiation beams received from the sample. For example, a detector can generate an electrical signal based on received radiation beams. The generated electrical signal can then be received by a processing device for further signal analysis and processing to perform certain actions and/or generate models based on the resolved depth optical data.

[115] At block 1208, an OCT image of the portion of the sample scanned by the catheter is generated based on the depth-resolved optical data. A processing device may be configured to generate a 3-D model of the sample portion by combining the depth-resolved optical data taken during the scan. The OCT image can be presented to a user, for example as an image on a display device, to provide the user with a better visual representation of the sample around the catheter. The processing device can also be configured to determine relevant parameters about the sample from the OCT data, such as, for example, a refractivity coefficient associated with birefringence.

Computer System Modality Example

[116] Various image processing methods and other embodiments described thus far can be implemented, for example, using one or more of the well-known computer systems, such as computer system 1300 shown in Figure 13. In one embodiment, computer system 1300 can be an example of processing device 108 illustrated in Figure 1.

[117] Computer system 1300 includes one or more processors (also called central processing units, or CPUs), such as a processor 1304. Processor 1304 is connected to a communication infrastructure or bus 1306. In one embodiment, a processor 304 represents a Field Programmable Gate Set (FPGA). In another example, processor 1304 is a digital signal processor (DSP).

[118] One or more processors 1304 may each be a graphics processing unit (GPU). In one embodiment, a GPU is a processor that is specialized electronic circuitry designed to quickly process mathematically intensive applications in electronic devices. The GPU can have a highly parallel structure that is efficient for parallel processing of large blocks of data, such as mathematically intensive data common to computer graphics applications, images and videos.

[119] Computer system 1300 further includes user input/output device(s) 1303, such as monitors, keyboards, pointing devices, etc., that communicate with communication infrastructure 1306 through user input/output interface(s) 1302.

[120] Computer system 1300 further includes main or primary memory 1308, such as random access memory (RAM). Main memory 1308 may include one or more levels of cache. Main memory 1308 has control logic (i.e., computer software) and/or data stored therein.

[121] Computer system 1300 may further include one or more secondary storage devices or a memory 310. Secondary memory 1310 may include, for example, a hard disk drive 1312 and/or a removable storage device or a removable storage unit 1314. Drive 1314 may be a floppy disk drive, a magnetic tape drive, a compact disc drive, an optical storage device, tape backup device, and/or any other device /storage unit.

[122] Removable storage unit 1314 may interface with a removable storage unit 1318. Removable storage unit 3118 includes a computer usable or readable storage device having stored on the same computer software (control logic) and/or data. Removable storage unit 1318 can be a floppy disk, magnetic tape, compact disk, Digital Versatile Disk (DVD), optical storage disk, and/or any other computer data storage device. Removable storage unit 1314 reads from and/or writes to removable storage unit 1318 in a well known manner.

[123] Secondary memory 1310 may include other means, instruments, or approaches for allowing computer programs and/or other instructions and/or data to be accessed by computer system 1300. Such means, instruments, or other approaches may include, for example, a removable storage unit 1322 and an interface 1320. a removable memory chip (such as an EPROM or PROM) and associated socket, a memory stick and universal serial bus (USB) port, a memory card and associated memory card slot, and/or any other removable storage unit and associated interface.

[124] Computer system 1300 may further include a communication or network interface 1324. Communication interface 324 allows computer system 1300 to communicate and interact with any combination of remote devices, remote networks, remote entities, and the like. (individually and collectively referenced by reference number 1328). For example, communication interface 1324 may allow computer system 1300 to communicate with remote devices 1328 over communication path 1326, which may be wired and/or wireless, and which may include any combination of local area networks (LANs), wide area networks (WANs), the Internet, etc. Logic and/or control data may be transmitted to and from computer system 1300 via communication path 1326.

[125] In one embodiment, a tangible apparatus or article of manufacture comprising a usable tangible computer or readable medium having control logic (software) stored therein is also referred to herein as a computer program product or program storage device. This includes, but is not limited to, computer system 1300, main memory 1308, secondary memory 1310, and removable storage units 1318 and 1322, as well as tangible articles of manufacture incorporating any combination of the foregoing. Such control logic, when executed by one or more data processing devices (such as a computer system 300), causes such data processing devices to operate as described herein.

[126] Based on the teachings contained in the present specification, it will be apparent to persons skilled in the relevant art(s) how to make and use the invention using data processing devices, computer systems and/or computer architectures other than those shown in Figure 13. In particular, embodiments may operate with software, hardware and/or implementations of operating systems other than those described herein.

[127] It should be appreciated that the Detailed Description section, and not the Summary and Summary sections, are intended to be used to interpret the claims. The Summary and Summary sections may set forth one or more, but not all, exemplary embodiments of the present invention as contemplated by the inventor(s), and, thus, are not intended to limit the present invention and the appended claims in any way.

[128] Embodiments of the present invention have been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined here for convenience of description. Alternative limits may be defined provided that the specified functions and relationships thereof are properly performed.

[129] The foregoing description of specific variants will, therefore, fully disclose the general nature of the invention that others may, by application of knowledge within their skill in the art, readily modify and/or adapt for various applications of such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Accordingly, these adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed specifications, based on the teachings and guidance presented herein. It is to be understood that the phraseology or terminology used herein is for the purpose of description and not limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled person in the light of teaching and guidance.

[130] The breadth and scope of the present invention are not to be limited by any of the exemplary embodiments described above, but are to be defined only in accordance with the following claims and their equivalents.

Claims (20)

1. Catheter (100) comprising: a proximal section (102); a distal section (104), the distal section comprising: one or more electrodes (306) configured to apply ER energy to a portion of a sample (308) in contact with one or more electrodes (306) such that the sample portion (308) is ablated, a plurality of interconnected optical ports (326) configured to transmit one or more beams of exposure radiation away from the distal section (104) of the catheter (100) and receive one or more beams s of scattered radiation that has been reflected or scattered from the sample (308); and a support (350) configured to maintain the interconnected optical ports (326) in a fixed spatial relationship; and a multiplexer (312) configured to direct one or more exposure radiation beams from the radiation source beam (502) and combine the one or more scattered radiation beams (342), characterized in that the plurality of interconnected optical ports (326) are formed on a substrate (320) with rigid sections (322) and flexible sections (324). 2. Catheter (100) according to claim 1, characterized in that the plurality of interconnected optical ports (326) are formed in rigid sections (322) of the substrate (320). 3. Catheter (100), according to claim 2, characterized in that the rigid sections (322) are interconnected by the flexible sections (324). 4. Catheter (100) according to claim 1, characterized in that the multiplexer (312) is located within the distal section of the catheter (104). 5. Catheter (100) according to claim 1, characterized in that the multiplexer (312) is located within the proximal section (102) of the catheter. 6. Catheter (100) according to claim 1, characterized in that the distal section (104) further comprises a plurality of openings (402) arranged around an outer surface of the distal section (104). 7. Catheter (100) according to claim 6, characterized in that the plurality of optical ports (302) are configured to transmit each of the one or more beams (342) of exposure radiation through a corresponding aperture (402) in the plurality of apertures. 8. Catheter (100) according to claim 7, characterized in that each corresponding opening (402) includes an optical element (344). 9. Catheter (100) according to claim 1, characterized in that a plurality of rigid sections (322) have an optical element (344) configured to focus each of the one or more exposure radiation beams (342) from each respective optical port (302). 10. Catheter (100) according to claim 9, characterized in that the optical element (344) is a lens. 11. Catheter (100) according to claim 9, characterized in that the optical element (344) has a reflective coating (336). 12. Catheter (100) according to claim 11, characterized in that the reflective coating (336) is on a parabolic surface. 13. Catheter (100), according to claim 1, characterized in that the support (350) is monolithic. 14. Catheter (100) according to claim 1, characterized in that the support (350) is an open structure. 15. The catheter (100) according to claim 1, characterized in that the support (350) includes a plurality of recesses (352) for supporting each rigid section (322) of the substrate (320). 16. The catheter (100) of claim 15, characterized in that the plurality of recesses (352) include a reflector coating (336) configured to focus each of the one or more beams of exposure radiation (342) from each respective optical port (302). 17. Catheter (100) according to claim 16, characterized in that the reflective coating (336) is on a parabolic surface. 18. Catheter (100), according to claim 1, characterized in that the distal section (104) further comprises a cover (410) attached to the support (350) and configured to cover the support (350) and the plurality of interconnected optical ports (326). 19. Catheter (100) according to claim 18, characterized in that the cap (410) includes a plurality of optical elements (404) positioned in the cap (410) such that each optical element (404) is optically aligned with at least one of the plurality of optical ports (302). 20. Catheter (100) according to claim 19, characterized in that the plurality of optical elements (404) is refractive.