EP2812739A1

EP2812739A1 - Configuring optical fibers to emit radiation by bending

Info

Publication number: EP2812739A1
Application number: EP13743215.9A
Authority: EP
Inventors: Ori WESBERG; Moshe Eshkol
Original assignee: Asymmetric Medical Ltd
Current assignee: Asymmetric Medical Ltd
Priority date: 2012-01-31
Filing date: 2013-01-31
Publication date: 2014-12-17
Also published as: EP2812739A4; WO2013114376A1; WO2013114376A8; CN104220908A; JP2015510142A

Abstract

Optical fibers are provided herein, which comprise a core and a cladding and have at least one region of the cladding that is arranged to emit electromagnetic radiation from the core upon bending the optical fibers beyond a bending threshold. The optical fibers are integrated in devices that either use bended fibers or induce the bending upon contacting a target, to emit the radiation at the target.

Description

CONFIGURING OPTICAL FIBERS TO EMIT RADIATION BY BENDING

BACKGROUND

1. TECHNICAL FIELD

[0001] The present invention relates to the field of optical fibers, and more particularly, to optical fibers configured to emit radiation by bending.

2. DISCUSSION OF RELATED ART

[0002] Optical fibers are a common way of delivering electromagnetic radiation, e.g. laser light, to a target. Optical fibers deliver the radiation in a tight beam originating from the end face directly or projected sideways by a mirror. An optical fiber assembly generally consists of four parts: core, cladding, coating and jacket. The core is the region in which light is guided; it is usually covered by a lower index cladding, in the case of a Total Internal Reflection (TIR) fiber. In case of a Photonic Crystal Fiber (PCF), e.g. having a beehive-like structure, an OmniGuide having photonic bandgap mirrors, a Bragg fiber etc., the cladding actually consists of a complex structure of higher index of refraction materials (disclosed e.g. in US7142756 which is incorporated herein by reference in its entirety). In a metallic waveguide, the core is lower index and the cladding is a coated metal, usually Ag coated by silver-iodide Agl. In all these fiber types light is confined to the core region under normal conditions, while in extreme bends light escapes the core and can even escape the entire fiber.

[0003] It is well known that waveguides and fibers suffer losses in bends. These losses are caused by the rays' higher angle of incidence on the core/clad (mirror) interface. This is often a major limitation most manufacturers try to avoid; see for example the Corning ClearCurve Fiber (disclosed e.g. in US5278931 which is incorporated herein by reference in its entirety). Another approach is to use outside cabling, as in US4078853, which is incorporated herein by reference in its entirety, to limit fiber bending and thus loss. Other devices take advantage of the optical power loss in the construction of sensors based on the loss in bends (disclosed e.g. in US4770047 which is incorporated herein by reference in its entirety).

[0004] In another example, US5138676 which is incorporated herein by reference in its entirety, discloses tight bending with low loss that is achieved by reducing fiber outer diameter (OD) and confining light with respect to the lower-index surrounding. OD reduction is performed by either removing part of the cladding or drawing down the fiber in the bent section. Other aspects are disclosed by US5278931, US4078853, US4770047 and US5138676, which are incorporated herein by reference in their entirety.

[0005] Tissue cutting and treatment are performed in three major methods: scalpels (cold steel techniques), electro- and laser-surgery. The main use of laser surgery is in ablation or coagulation of soft tissue. In laser surgery, an optical fiber is often used to deliver the laser energy to the desired site with minimal losses on the way.

[0006] In the case of soft tissue cutting and most other medical uses of fibers, laser light is emitted from the tip of the fiber at the treatment site. The fiber is used to safely deliver the energy to die exact location in spot form as in VersaPulse by Lumenis. In some cases local redirection of the fiber tip is used for improved targeting as disclosed e.g. in US7238180, which is incorporated herein by reference in its entirety.

[0007] In other cases, the fiber is manipulated to allow laser emission at a 90° angle to the fiber tip, term "side firing", which makes it easier to use in cases where it is geometrically harder to bend the fiber tip in the required direction. The straight angle is achieved using a mirror or a side fire mechanism. Sometimes when the side fire approach is used, specific treatment of the fiber edge is required in order to prevent local damage and facilitate effective tip side firing as disclosed e.g. in US20070106286, which is incorporated herein by reference in its entirety. In some cases tip side fire is enabled by tapering the fiber core as disclosed e.g. in US20110002584, which is incorporated herein by reference in its entirety. Alternatively, side firing is achieved by increasing the index of refraction of the cladding on one side by preferential heating, using an external laser source (disclosed e.g. in US6606431, which is incorporated herein by reference in its entirety). [0008] The following US patents teach devices that utilize laser radiation for cutting. These patents are incorporates herein by reference in their entirety. US 4266547 teaches a laser knife acting linearly between an emitter and an acceptor; US 5151097 teaches a laser emitter that emits radiation through an uncovered area in an element that is otherwise covered by a light impervious material; US 5470331 teaches a laser light transmissive probe system that is provided with an opposed pair of laser light transmissive probes for pinching tissue; US 6283962 teaches a medical ablation device and US 6221069 teaches an apparatus having an outer probe having a form of hook and an inner probe for contacting the outer probe and heating a target tissue disposed therebetween. US patents 5531741 and 6409719, which are incorporates herein by reference in their entirety, teach devices that utilize an optical fiber to illuminate a scene in which stents are implants.

BRIEF SUMMARY

[0009] One aspect of the present invention provides an optical fiber comprising a core and a cladding, the optical fiber having at least one specified region of the cladding that is arranged to emit electromagnetic radiation from the core upon bending the optical fiber at the at least one specified region beyond a specified bending threshold.

[0010] These, additional, and/or other aspects and/or advantages of the present invention are: set forth in the detailed description which follows; possibly inferable from the detailed description; and/or learnable by practice of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a better understanding of embodiments of the invention and to show how the same may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings in which like numerals designate corresponding elements or sections throughout.

[0012] In the accompanying drawings: Figure 1A is a high level schematic block diagram of an emitting region of an optical fiber, according to some embodiments of the invention;

Figure IB is a schematic illustration of the dependency of the emitted radiation through the specified region on the bending radius, according to some embodiments of the invention;

Figure 1C is a schematic illustration of the dependency of the emitted radiation through the specified region on the bending radius (y axis) and on the ratio ΠΕΛΙΚ (X axis), according to some embodiments of the invention;

Figures 2A-2I are high level schematic illustrations of various embodiments of the optical fiber having an asymmetric cladding in cross section, according to some embodiments of the invention;

Figure 2J illustrates an embodiment of the fiber with a coating that has a gap or is missing at the specified emission region, according to some embodiments of the invention;

Figure 2K illustrates an embodiment of a metallic waveguide having a gap at the specified emission region, according to some embodiments of the invention;

Figure 3A is a high level schematic illustration of the fiber with a flat supportive structure attached on an opposite side of the fiber with respect to the emitting region and the target, according to some embodiments of the invention

Figure 3B is a high level schematic illustration of the fiber with lateral circle segments, according to some embodiments of the invention;

Figure 3C is a high level schematic illustration of the fiber with a circular segment at the fiber tip, according to some embodiments of the invention;

Figures 4A-4C and 4E-4J are high level schematic illustrations of devices using bend emission, according to some embodiments of the invention;

Figure 4D illustrates an experimental comparison between a fiber snare device according to some embodiments of the invention and an electrosurgical snare regarding the emission profile;

Figures 5A-5C illustrate configurations of controlling the electromagnetic radiation transmitted through the fiber, according to some embodiments of the invention; Figures 6A-6J are high level schematic illustrations of a device having optical fibers exhibiting bend emission wound on a supportive structure such as a balloon, according to some embodiments of the invention;

Figure 7A-7E illustrate the cladding of the fiber, becoming asymmetric in cross section upon application of a strain at the specified region, according to some embodiments of the invention;

Figures 8A and 8B demonstrate bend emission for the fiber configuration illustrated in Figure 2H (serrated fiber), according to some embodiments of the invention;

Figure 9 is a high level schematic flowchart of a method of configuring emission from an optical fiber and removing an obstruction therewith, according to some embodiments of the invention;

Figures 10A and 10B schematically illustrate a fiber having three emission sectors in the emission region and a hook device using this fiber, according to some embodiments of the invention;

Figures 11A-11E schematically illustrate a device configured as tweezers, according to some embodiments of the invention;

Figures 12A and 12B schematically illustrate a device with a feedback loop for controlling emitted radiation, according to some embodiments of the invention;

Figure 13 schematically illustrates fiber having multiple emission sectors in the emission region, according to some embodiments of the invention;

Figure 14 schematically illustrates a device for cutting vessels, according to some embodiments of the invention; and

Figures 15A and 15B illustrate a device for treating target by pressing device upon it, according to some embodiments of the invention.

DETAILED DESCRIPTION

[0013] With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

[0014] Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

[0015] Figure 1A is a high level schematic block diagram of an emitting region of an optical fiber 110, according to some embodiments of the invention. Optical fiber 110 comprises a core 130 having a refractive index n_K and a cladding 115 having a refractive index n - Optical fiber 110 has at least one specified region of cladding 115 that is arranged to emit electromagnetic radiation from core 130 upon bending optical fiber 110 at the specified region beyond a specified bending threshold with respect to a bending radius r 105. The emission of electromagnetic radiation from core 130 upon bending optical fiber 110 is related to in the following as bend-emission (BE). The bend emission depends on various fiber and radiation characteristics such as the size, structure and materials of the fiber, bending radius 105, radiation frequency and so forth. The fiber is designed to enable bend emission in the specified region and sectors only, while continuing to prevent transmission through the cladding in other parts of the fiber.

[0016] It is noted that bend-emission may be configured to occur inwards or outwards with respect to the direction of bending. It is further noted that the disclosed principles are also applicable to other types of waveguides, e.g. RF waveguide (see e.g. Figure 2K illustrating a metallic waveguide), which may be tailored for specific geometrical parameters allowing highly controlled and specific emission patterns.

[0017] Bend emission may be achieved by bending fiber 110 prior to an actual application thereof, e.g. bending fiber 110 to have a snare-like form, and angled form, a stent-like form etc. (see examples below), and then controlling the bend emission by the light source upon placing the bended regions of fiber 110 in an operative position. Alternatively or complementary, bend emission may be under geometrical control, achieved by making use of the natural curvature of the targeted object to generate the desirable energy discharge profile from the waveguide. Certain regions in fiber 110 may be designed to bend-emit upon curving in contact with the target, as exemplified below, and the energy that is emitted in bends in these regions is actually used to achieve the desired goal. In such case, emission may be controlled by the actual bending, in addition or in place of controlling the light source.

[0018] Any type of fiber 110 may be arranged to emit radiation upon a specific bending, e.g. a waveguide (which may comprise metallic waveguides), a solid core optical fiber, a hollow fiber and a photonic crystal fiber (such as a holey fiber, a Bragg fiber or any other micro-structured fiber). The non-emitting sector(s) may be micro-structured (e.g. with a grating or air holes) to reduce an effective refractive index thereof below a refractive index of the emission sector and/or to direct radiation toward the emission sector.

[0019] Optical fiber 110 may be single-mode or multi-mode, in the latter case, the specified emission region and bending threshold may be selected with respect to the required modes, to control the emitted energy. In addition, the specified emission region and bending threshold may be selected with respect to, and controlled by, the beam polarization.

[0020] Bends in fiber 110 that may be used in emitting regions 120B include both micro- bends (local deviations from the fiber's linearity, with relative small bending radii) and macro-bends (changes of angle of the fiber's direction, usually larger bending radii). For example, the emitted radiation from a macro-bend may be estimated, for single mode fibers, by the expression: Exp (8.5-519-D-( (2^MFR))³) in dB/m, where D is the bending radius in mm, λ is the wavelength in urn, λ,_» is the fiber cut-off wavelength in μιη and MFR is the mode fiber radius in μιη.

[0021] Figure 1A illustrates the condition for bend emission, according to some embodiments of the invention, by illustrating an example of a possible trajectory of light travelling down fiber 110. The light reaches the beginning of the bended specified region 120B at an angle a that is not yet sufficient for BT due to the bend radius which is not sufficiently small at this point (i.e. a is still larger than θ_ΕΠ,_ωη8 The light is thus reflected to cladding side 115A and is internally reflected at angle β which is larger than 0_ci_adding = and stays within core 130. Upon reflection from cladding 115A the light reaches sector 120B with cladding 115B at an angle γ which is now smaller than 6_emi_tting region= sin^'^nE nic), as the bending radius reaches at this point the threshold radius and goes beyond a specified bending threshold of the specified region of fiber 110 (i.e. bending radius becomes smaller than the threshold radius). The transmitted light exits region 120B at an angle Θ. The exact calculation follows Wang et al. (2007) "Investigation of Macrobending Losses of Standard Single Mode Fiber with Small Bend Radii", in Microwave and optical letters 49:9, 2133-2138. Bend-emission can be approximated as starting to occurr at angle 9b_end that is defined using bending radius r 105 as: 9bend = ID being the internal diameter i.e. core diameter. The condition for bend-emission is that sin^"'(nM/n_K) = 6_ciaddin_g < Qbend < 0_emitun_{g reg}ion= sin^" '(n_E/n_K).

[0022] Other than the prior art, the present invention utilizes conditional and controllable side emissions from an optical fiber. In contrast to side firing fibers, fibers of the present invention do not emit any radiation when straight or bended below the bending threshold. The side emission is activated only upon the bending of the fiber at a predetermined bending radius, for example by an obstruction that is to be removed by the fiber, or according to a specific device design.

[0023] During treatment by emitted radiation 152, parts of the treated target (e.g. a flow obstruction or a polyp) are removed, causing the target to be decimated and flattened. In some embodiments, target flattening reduced the bending of fiber 110 (increases the bending radius thereof) and causes a reduction in bend emission until conclusion of the treatment. Such effect may be desired and taken into account when selecting the bending threshold. In some embodiments, a different specified region may take over the treatment, and be activated by a different bending threshold to allow multi-stage treatment.

[0024] Figure IB is a schematic illustration of the dependency of the emitted radiation through the specified region on bending radius 105, according to some embodiments of the invention. Figure IB illustrates a broad peak of emitted radiation at about 1-3 mm of bending radius, in which over 90% of the electromagnetic radiation transferred through optical fiber 110 is emitted through the specified region. Furthermore, Figure IB illustrates that radiation is emitted from cladding 115 upon bending, not specifically from the specified region (dashed line), is much smaller in intensity and occurs at much smaller bending radii (mostly under 0.5 mm). Hence, Figure IB illustrates the good controllability of the emitted radiation by the design of the specified region.

[0025] In one example, the specified region has a cladding 115A having a refractive index ΠΜ in a non-emitting sector 120A and a cladding 115B having a refractive index n_E in an emission sector 120B. In case of a solid core fiber, the refractive indices satisfy ηκ≥ηΕ>ΠΜ· In case of a hollow (air) core fiber, the refractive indices satisfy η_Μ,ΠΕ>ηκ. In the latter case, embodiments may comprise either ΠΜ≥ΠΕ or nE≥iiM depending on the indices of refraction and on the material's absorption, scattering and micro-structure.

[0026] Figure 1C is a schematic illustration of the dependency of the emitted radiation through the specified region on bending radius 105 (y axis) and on the ratio ηε/η (x axis), according to some embodiments of the invention. The lines in Figure 1C indicate ratios of electromagnetic radiation emitted through the specified region to electromagnetic radiation transferred through optical fiber 110, namely 0.2, 0.4, 0.6 and 0.8, which are also the values indicated on the y axis of Figure IB. Figure 1C illustrates increasing emission with g nR ratio nearing 0.99 (with constant radius 105) and increasing emission with decreasing bending radius 105 (with constant ΠΕΛΙΚ ratio), i.e. with stronger bending of optical fiber 110.

[0027] In embodiments, one or more optical fibers 110 may be incorporated in a device 100 (see e.g. Figures 5C, 6A and 6C) having at least one light source arranged to transmit electromagnetic radiation through one or more optical fibers 110. The following description starts with embodiments of optical fiber 110 and continues with embodiments of device 100. For the sake of brevity of description, it is understood that any one of the optical fiber embodiments may be implemented in any one of the device embodiments, and all possible combinations are included therefore in the present invention.

[0028] Figures 2A-2I are high level schematic illustrations of various embodiments of optical fiber 110 having an asymmetric cladding 115 in cross section, according to some embodiments of the invention. Figures 2A-2I illustrate cross sections through the specified region. Generally, the emitting sector is numbered 120B (and 120C, in case of several emitting sectors) while the non-emitting sector is numbered 120A. The respective coating sections are numbered 115B and 115A respectively. Figures 2A-2I illustrate one or two emitting sectors as examples, fiber 110 may be arranged to comprise more than two emitting sectors 120B, 120C, multiple different sectors at different specified regions along fiber 110 and any other region and sector configuration according to given requirements.

[0029] Figure 2A illustrates fiber 110 with two differing cladding types 115A, 115B having different refraction indices n_M, n_E respectively. ¾ is generally closer to n_K so that bending fiber 110 at the specified region beyond the bending threshold results is emission 152 of radiation through section 120B in the specified region, as exemplified in the calculations below.

[0030] In embodiments, the normalized refractive index difference between the cladding of the specified emission region and the cladding of non emitting regions may be larger than ca. 0.1 % (e.g. as ), and may be larger than ca. 0.5%. Differences may be larger or smaller, depending on the exact materials and structures used and operational (predefined or resulting) bending radii 105 (as a non-limiting rule of thumb, the larger the difference in refractive indices, the smaller is the threshold bending radius).

[0031] Two non-limiting examples, which refer to commercial S1O2 fibers having a refractive index of n_K=1.457 (at 633nm) are (i) ΠΜ=1.456 and n_E=1.457 and (ii) n_M=1.000 and n_E=1.450.

[0032] Figure 2B illustrates fiber 110 with two differing cladding types 115A, 115B having different types of microstructures 116A, 116B respectively, in the illustrated cases different Bragg type structuring of cladding 115. In the illustrated example, Bragg structures 116A are more extensive in cladding 115A than Bragg structures 116B in cladding 115B, resulting in emission 152 through sector 120B upon bending beyond the threshold. Other embodiments may comprise one sided Bragg micro-structuring or multiple zones with differing Bragg micro-structuring. Furthermore, structure 116B may have no Bragg layers and may be constructed of a single material.

[0033] Figure 2C illustrates fiber 110 with two differing cladding types 115A, 115B the latter having microstructures 117A, 117B such as holes (e.g. air holes), that reduce n_M in non-emitting region 120A with respect to ΠΕ in emitting region 120B. In general, optical fiber 110 may be an asymmetric photonic crystal fiber, which can also be used for additional purposes. Optical fiber 110 may be an asymmetric Photonic Crystal Fiber (PCF), e.g. according to one of the illustrated embodiments, which can also be used for additional purposes. Microstructures 117A, 117B may be present in emitting region 120B and in non-emitting region 120A to different extents (regarding the number of microstructures 117A, 117B, their parameters and their spatial expansion), or be present on one side only, e.g. only microstructures 117A in non-emitting region 120A, to prevent emission therefrom.

[0034] Figure 2D illustrates fiber 110 having cladding 115 designed to have a large air gap 118 in non-emitting region 120A and additionally core 130 that may be asymmetrically positioned (i.e. off-center or eccentrically) with fiber 110. Core 130 may further be non-circular (e.g. elliptic in Figure 2D) to define the bending threshold according to requirements. The form and extent of air gap 118, the specific design of cladding 115 and of core 130 may be adapted to specific bend-emission parameters and specifications.

[0035] Figure 2E illustrates another asymmetric fiber configuration, comprising asymmetric core 130 positioned off-center of fiber 110 and cladding 115 comprising multiple air holes 119 arranged to define non-emitting region 120A. The exact configuration of core 130 and cladding 115 may be selected according to specific bend- emission parameters and specifications.

[0036] Figure 2F illustrates another example of asymmetric fiber 110, namely an embodiment having a specified form and position of the emitting sector 115B of cladding 115 and of core 130.

[0037] Figure 2G illustrates optical fiber 110 having multiple emission sectors, that may be designed at various positions in the cross section of fiber 110. In the illustrated case as a non-limiting example, two opposite emission sectors 120B, 120C, that may have similar or different emission characteristics. Emission sectors 120B, 120C may be at different angles to each other and may comprise more than two emission sectors. Emission sectors 120B, 120C may be associated with different cores 130B, 130A respectively, e.g. to be configured to emit electromagnetic radiation 152B, 152A with different parameters (e.g. wavelength, intensity). Emission sector 120C may be associated with additional core 130A. Emission sectors 120B, 120C may have different bending thresholds, also in respect to the direction of emission (may emit upon inwards or outwards bending).

[0038] Electromagnetic radiation, such as laser energy, may be delivered to either or both cores 130B, 130A simultaneously or sequentially. Without loss of generality, fiber 110 may have several specified regions and/or several emission sectors 120B, 120C etc. which may be constructed axially so as to deliver energy along fiber 110 to different specified regions and/or the emission sectors may be constructed tangentially to deliver energy to several regions along fiber 110 simultaneously or sequentially.

[0039] Figure 2H illustrates optical fiber 110 having radially serrated cladding 115 at the specified region, in which spaces 121A, 121B between the serrations are defined according to the specified bending threshold. Upon bending fiber 110, serrations on one side of fiber 110 move closer to each other (spaces 121A become smaller with respect to a straight fiber 110), while serrations on the opposite side of fiber 110 spread apart (spaces 121B become larger with respect to a straight fiber 110). Emitting region 120B may be on either side of fiber 110, depending on the relation between ηκ and ΠΜ· For ^ηκ>ηΜ (solid core), the crowding together of the serrations increases the effective refractive index of cladding 115 to near ηκ and emitting region 120B is hence on the concave side, while the spreading apart of the serrations reduces the effective refractive index of cladding 115 and non-emitting region is hence on the convex side of fiber 110.

[0040] The serrations on the concave side can guide the energy in a periodic manner (see Figure 8B), focusing energy to desired regions along the specified region. Figure 8 A (see below) illustrates the energy delivery in a simulated 90° bend in optical fiber 110. The energy delivery through the cladding is in solid line and the radiation through the specified region is in dashed line. The emitted radiation is focused periodically due to the serration in the concave bended region. In addition, serrations also enable mechanically the bending of fiber 110 in smaller bend radii.

[0041] Figure 21 illustrates another example of asymmetric fiber 110, namely an embodiment having a specified form and position of the emitting sector 115B of cladding 115 and of core 130. Core 130 is elongated and eccentric relative to cladding 115, and has an effective radius 131. The cross sectional structure may be designed to direct emitted radiation 152 to a focal point 154, e.g. on a radial symmetry axis of emitting sector 115B. A core-cladding interface 153 may be shaped to influence the emission characteristics.

[0042] The fiber's cross section may be configured to emit radiation 152 not only in a specific direction but also in a specific profile. The light from core 130 may be optically manipulated to exit the waveguide in a narrow flat profile or alternatively in a dispersive profile as needed. Core-cladding interface 153 may be designed to serve as a lens to focus the naturally dispersive energy. For example, Figure 21 illustrates a cross-sectional view of one of the profiles that serves to focus the energy. In this case, trajectory 153 of emitted radiation 152 reaches core-cladding interface 153 and is then focused inward to focal point 154 closer thereto than would have been emitted radiation from a radially symmetric interface, due to the shorter effective radius 131 of core 130. The unique assembled structure allows to asymmetrically emit the energy away from core 130 to one side only and also manipulates interface 153 in a very specific manner that dictates the exact emission profile. Other profiles may be generated by fiber cross sectional profiles exemplified in Figures 2D-2F.

[0043] The index of refraction also depends on temperature. Generally, an increase of temperature causes an increase in the index of refraction. In one embodiment, in which fiber 110 is inherently asymmetric as in Figure 21, energy discharge 152 may be asymmetric as well. Since energy 152 is discharged on the inner side of the bend, this side gets warmer, creating a positive feedback loop which increases discharge 152 and thus the accuracy and safety as well since this effect occurs only at the treatment site. The increase of temperature leads to an increase in the index of higher refraction in emitting section 120B and thus to increased energy discharge and more heating, reinforcing the discharge mechanism. Straightening the bend halts and reverses the process. The precise target energy of the tissue's cutting/heating is tuned to enhance and increase the effectiveness of bend emitted radiation 152. The cladding material may be chosen with specific absorption to control the effect of bend-emission.

[0044] Figure 2 J illustrates an embodiment of fiber 110 with a coating 140 that has a gap or is missing at specified emission region 120B, according to some embodiments of the invention. Coating 140 may have an inner reflective surface that yields or enhances the bend emission and its directionality. Generally, coating 140 may be asymmetric in cross section at specified region 120B. Other parts of fiber 110 or the device (see below) may be configured to enhance beam emission.

[0045] Figure 2K illustrates an embodiment of a metallic waveguide having a gap at specified emission region 120B, according to some embodiments of the invention. The design and applicative concepts for fiber 110 and device 100 that are presented herein, may be applied to metallic waveguides, delivering e.g. electromagnetic radiation. The gap in the metallic waveguide may used to emit radiation 152 therethrough for applying a treatment.

[0046] Figure 3A is a high level schematic illustration of fiber 110 with a supportive structure 141 attached on an opposite side of fiber 110 with respect to emitting region 120B and the target, according to some embodiments of the invention. Supportive structure 141 may be used to orient fiber 110 to position emitting region 120B at a correct orientation with respect to the target and reflect excessive energy upon the target. Supportive structure 141 may be associate in various embodiments of device 100 (see below).

[0047] For construction purposes, fiber 110 may be attached to or embedded in reinforcing structure or stabilizer 141, to ensure stability and prevent breakage. Reinforcing structure 141 may be a semi-tube (e.g. similar to coating 140 in Figure 2J) or a ribbon (e.g. as in Figure 3A), made of plastic or metal. In some cases fiber 110 may be inserted into stabilizer 141 after it is set in the desired location, for example, after stabilizer 141 has been inserted around obstruction 95 (e.g. a polyp or a tumor) to be excised. Furthermore, reinforcing structure 141 may serve for inward reflection of emitted energy 152.

[0048] Figure 3B is a high level schematic illustration of fiber 110 with lateral circle segments 142, according to some embodiments of the invention. Segments 142 have arcs that define the emission sectors and further emit electromagnetic radiation 152 at a plane defined by the arcs. Fiber 110 may comprise one or more such segments 142 at the specified region. Segments 142 may be part of cladding 115, e.g. produced by cutting into cladding material, be part of coating 140 or be attached structures. Segments 142 may further focus radiation 152 onto the target.

[0049] Figure 3C is a high level schematic illustration of fiber 110 with a circular segment 143 such as a disc, at the fiber tip, according to some embodiments of the invention. Circular segment 143 has at least one circle segment 143 having an arc defining at least one tip emission sector emitting electromagnetic radiation 152 at a plane defined by the arc. Tip emission sector may operate upon bending of fiber 110 or independently therefrom.

[0050] Embodiments of the invention further comprise optical fibers with an asymmetric cross section, and in particular optical fibers with asymmetric cladding, in which the asymmetry defines at least one emission sector and at least one non-emitting sector in cross section. The difference in the refractive indices between the emitting and non- emitting sectors may be larger than 0.1%, larger than 0.5% or larger than the difference in the refractive indices between the emitting sector and the fiber's core.

[0051] The following illustrations depict examples for devices 100 which implement optical fibers 110 exhibiting bend-emission. Each device 100 may be implemented using any embodiment of optical fiber 110 described above according to the device's specifications, under constraints resulting from manufacturing issues but not from conceptual issues.

[0052] Figures 4A-4C and 4E-4J are high level schematic illustrations of devices 100 using bend emission, according to some embodiments of the invention. Figures 4A-4C illustrate a fiber snare device 100, Figure 4D illustrates an experimental comparison between a fiber snare device and an electrosurgical snare regarding the emission profile; Figure 4E, 4F, 4H and 41 illustrate fiber hook devices; Figure 4G illustrates a device for treating flow obstructions and Figure 4J illustrates a device with an optical element designed to generate plane emission from the fiber.

[0053] Device 100 comprises at least one optical fiber 110 and at least one light source 70 (see e.g. Figure 5C), arranged to transmit electromagnetic radiation through the at least one optical fiber 110. Optical fiber 110 comprises at least one core 130 and cladding 115. Each optical fiber 110 has at least one specified region that is arranged to emit electromagnetic radiation from core 130, upon bending optical fiber 110 at the region(s) beyond a specified bending threshold. Emitting regions 120B may be single or multiple, and may be used to deliver radiation at different intensities and wavelength ranges, possibly for different purposes, such as cutting, ablation, different kinds of treatment and marking.

[0054] For example, optical fiber 110 may be formed as a snare (Figures 4A, 4B) with an apical bended region arranged to emit electromagnetic radiation 152 in a plane defined by the snare. Device 100 may improve on prior art electrosurgical snares by creating a much more precise and cleaner cut of an obstruction 95, e.g. of polyps, as illustrated in Figure 4B. The plane of emission 152 is in the inner part of the snare and emission 152 results from the bending of optical fiber 110 at the apical region of the snare. In embodiments, no or very low radiation is emitted outwards, in region 120A. As an applicative example, Figure 4B illustrates snare-like optical fiber 110 applied through a channel 77 of an endoscope 76.

[0055] In embodiments, optical fiber 110 of the snare may have an additional emitting region 120C, e.g. defined by a sector 115C of the cladding at an angle to main emitting sector 115B of the cladding. Region 120C may emit electromagnetic radiation 151 having different characteristics than electromagnetic radiation 152 used for cutting, for example, weaker radiation or radiation in a different wavelength range, that may be useful e.g. for ablating the edges of obstruction 95 to prevent bleeding and prevent infection. It is noted that such ablation is more effective than prior art laser ablation, as radiation 151 is applied smoothly and in the correct direction due to the structure of the snare itself (see Figure 4B).

[0056] A further advantage of fiber snare 110 with respect to a prior art electrosurgical snare is illustrated in experimental results depicted in Figure 4D, namely the cutting plane of fiber snare 110 is much narrower than the cutting plane of electrosurgical snare, causing hence less damage to adjacent tissue and producing a cleaner cut.

[0057] Figures 4E and 4F illustrate fiber hook device 100 in which optical fiber 110 is bended at an angle and held by a holder 111 or self-sustained (respectively) and the bend is arranged to emit electromagnetic radiation 152 in a plane defined by the predefined bending angle (respectively). Such fiber hook device 100 may operate similarly to the fiber snare under different geometries of obstruction 95. For example, fiber hook may replace a similar electrosurgical hook in treating upper GI lesions by Endoscopic Submucosal Dissection (ESD).

[0058] In embodiments of device 100, light source 70 may comprise at least two light sources 70 configured to transmit at least one treatment beam and at least one guiding beam through at least one optical fiber 110. For example, a guiding beam may be used to mark the treatment plane of fiber snare 110 or fiber hook 110 without affecting obstruction 95. Such a guiding beam may be very useful for surgical planning and may further enhance the accuracy of operation using device 100.

[0059] Figure 4G illustrates treatment of flow obstructions 95 by a supportive structure 122 that allows continued flow 86 through lumen 85, such as of a vessel 90 (e.g. an artery). Bending of fibers 110 attached to supportive structure 122 applies radiation 152 as treatment of obstructions 95, and upon their removal, the bending flattens and treatment ceases.

[0060] Figures 4H and 41 illustrate fiber 110 as a J shaped device in which emitted radiation 152 is emitted in a plane from the curved part of the "J", either outwardly, as illustrated in Figure 4H, or inwardly, as illustrated in Figure 41, selected according to clinical needs and design consideration (a single device 100 may have both functions, e.g. have a different fiber for each purpose, or operate differently at different wavelength regions, or different devices may be designed for these emission patterns). Figure 41 further illustrates an embodiment in which the fiber tip is designed to direct energy emitted therefrom sideways, in the plane of radiation, e.g. by designing a reflective element 165 (e.g. a coating or an attached mirror) at the tip which is coupled to circular segment 143 designed to direct emitted tip energy sideways in the emission plane.

[0061] Figure 4J illustrates device 100 with an optical element 144 designed to generate plane emission 152 from fiber 110, according to some embodiments of the invention. For example, optical element 144 may be designed to reflect radiation 152 emitted from the bended emission region 120B of fiber 110 in a designated plane (e.g. as an enhancement of the snare-like device described above).

[0062] Figures 5A-5C illustrate configurations of controlling the electromagnetic radiation transmitted through fiber 110, according to some embodiments of the invention. With respect to the design of device 100, the transmitted radiation that is not emitted must be controlled and regulated.

[0063] In an embodiment illustrated in Figure 5C, transmitted radiation may go through fiber 110 from source 70 and introductory fiber 161 to exiting fiber 168 and an absorptive sink 169 at the fiber's end (of course introductory fiber 161, treatment fiber 110 and exiting fiber 168 may be implemented as a single fiber, with only fiber 110 exhibiting bend emission in the specified region). Such configuration may also be applied when fibers 110 are weaved around balloon 122 (see below) and then guide the transferred radiation to exiting fiber 168. Absorptive sink 169 may also be located at the end of device 100, as illustrated in Figure 6A below.

[0064] In embodiments illustrated in Figures 5A and 5B, a tip 163 of optical fiber 110 is reflective to reflect non-emitted electromagnetic radiation. In Figure 5A, the reflectance is achieved by a Bragg grating 164 of appropriate characteristics, in Figure 5B, the reflectance is achieved by a coating 165 (or an attached mirror 165) and exiting fiber 168 is arranged to receive reflected electromagnetic radiation. Using reflective tip 163 not only helps dealing with excessive radiation, but also doubles the potential bending emission, by running the radiation twice through the specified region.

[0065] Figures 6A-6J are high level schematic illustrations of device 100 having optical fibers 110 exhibiting bend emission, that are wound on a supportive structure 122 such as a compliant or non-compliant balloon, according to some embodiments of the invention.

[0066] Figure 6A illustrates supportive structure 122 embodied as balloon 122, to which fibers 110 are attached. Balloon 122 may be inflated by pump 75 and inserted via delivery system 76 and channel 77, such as an endoscope, possibly guided by a guide wire 138 (see Figure 6F). Balloon 122 may be fixated and controlled by a guide 139 close thereto. Balloon 122 may comprise absorptive sink 169 at its end, or wound fibers 110 may be circular and guide back excessive radiation (as illustrated schematically in Figure 5C).

[0067] Fibers 110 may be wound and attached to balloon 122 in different configurations. Figure 6B illustrates a balloon cross section with fibers 110 evenly distributed on the skin of balloon 122. Figure 6C illustrates an embodiment with fibers 110 wound transversely to the direction of application of balloon 122. Figures 6D, 6E, 6H and 61 illustrate more complex winding patterns involving spiral windings in two directions. Winding of fibers 110 may be transverse or longitudinal with respect to the length axis of balloon 122 or exhibit any combination thereof or other form. In general, optical fibers 110 may be wound in a configuration that is perpendicular, parallel or oblique to a longitudinal axis of balloon 122 or in a combination thereof.

[0068] Winding of fibers 110 may be stent-like, having a collapsible stent-like configuration (Figure 6F) and an expanded stent-like configuration (Figure 6G). Figures 6H and 61 may also be implemented in a stent-like design. Figures 6H and 61 illustrate implanted stents 100 comprising active fibers 110 which upon energy transfer 166 from a source 167 within or outside the body emit energy 152 through bended emission regions 120B (not shown in this figure). Figure 6H illustrates device 100 which may be implanted in a region of obstruction 95 such as plaque or other diseased region in e.g. the esophagus (Gastroesophageal reflux disease GERD) or bronchi (asthma), to enable gradual ablation of plaque/tissue 95, or localized treatment by drug activation PDT. For example, one or more fibers 110 may be incorporated in a stent of any kind to deliver radiation that activates a drug that is associated with the stent. Furthermore, device 100 may comprise in any of the embodiments, a drug eluting means such as a needle, arranged to elute a drug in the vicinity of the radiation emission. The radiation may be then utilized to activate the drug or the drug may be used to enhance the effect of the laser treatment. Figure 61 illustrates device 100 in which emitted energy 152 may be used to inhibit or activate nerve firing 96, for example in the renal arteries to block sympathetic outflow from the kidney and thus reduce systemic blood pressure, to block pain signals in certain cases, or to control the sensation of hunger in eating disorders or obesity. Such states may also be treated by fibers 110 and devices 100 illustrated in other embodiments. Figure 6J illustrates device 100 comprising fibers 110 wound around a stent 112 or replacing one or more of the wires of braided stent 112. Bended fiber 110 may be arranged to emit radiation that supports the placing of stent 112, ablates tissue surrounding stent 112 (e.g. before, during or after the healing process) or interacting with eluted drugs.

[0069] In embodiments, any optical fiber may be used in combination with a stent for activating a treatment such as ablation, activation of a radiation sensitive drug or activation of nerve endings for various purposes. Regular emission from fiber tips may be used in addition to or in place of bend emission to deliver the required radiation and apply specified treatments.

[0070] Supportive structure 122 of device 100 is configured to position optical fibers 110 with respect to a target 95 (such as a flow obstruction) in a way that causes bending of all, some or at least one optical fiber 110 beyond the specified bending threshold thereof over target 95, to emit electromagnetic radiation 152 at target 95. In the case of balloon 122, inflating balloon 122 may cause fibers 110 to bend upon contacting target 95 beyond the emission threshold.

[0071] The topographically induced bending can be utilized to deliver energy specifically to those areas where the treatment is required, such as flow obstructing plaque (see e.g. Figures 4G and 6C below). Balloon 122, that may be delivered with a standard catheter delivery system, is inflated in-situ, causing fibers 110 on the surface of balloon 122 to be pressed against the artery and plaque and be imprinted with the topography. The imprint causes bends in the fiber that induce the desired bend emission which is used to treat the lesions.

[0072] Figure 6C illustrates flow obstructions 95 such as vascular lesions in an arterial bifurcation. While prior art treatment of lesions in bifurcations is particularly difficult due to the geometry of the treated area, device 100 utilizes the difficult geometry to enhance the treatment, as the bending of balloon 122 and fibers 110 attached to it is enhanced by the difficult geometry and thus facilitates treatment. In embodiments, removal of obstructions 95 may complete the treatment simply by the resulting increase in the bending radius beyond the specified threshold. Device 110 clearly allows treatment of several obstructions, as illustrates in Figures 4F and 6C. Lesion 95 is located at sides of vessel 85 and at the apex of the bifurcation. Emission regions 120B, 120C may be multiple, and fibers 110 may be configured to emit radiation based on different thresholds in regions 120B, 120C and thus enable specialized treatment of the bifurcation. For example, parameters of different emission regions may be determined by geometrical considerations of target 95 and operation surrounding and its relation to the structure of device 100 as well as by treatment considerations (types of applied treatments at different regions, radiation intensity, safety considerations etc.). [0073] Figure 6E illustrates an embodiment of device 100 that is operated by an external source 166. External source 166 may activate device 100 by any kind of radiation or field applied to device 100. Such device 100 may have a balloon as supportive structure 122, or fibers 110 may be stent-like, having a collapsible stent-like configuration (Figure 6F) and an expanded stent-like configuration (Figure 6G). Device 100 may be used acutely during procedure or be implanted for permanent use.

[0074] In embodiments, fibers 110 may be arranged as resonators that amplify induced radiation from source 166 and thus generate the required radiation for treatment without using an internal light source 70.

[0075] Figures 6F and 6G illustrate a collapsed configuration and an expanded configuration of device 100 (configured either as a balloon or as a stent) in treating an obstruction in a heart 60. Such embodiments may comprise a stop point for fibers energy or an energy sink, as illustrated e.g. in Figures 5A-5C and 6A.

[0076] Figure 7A-7E illustrate cladding 115 of fiber 110, becoming asymmetric in cross section upon application of a strain 171 at the specified region, according to some embodiments of the invention.

[0077] Normally, fiber materials like silica tend to have lower values of tensile stress than compressive stress. Basically this means that when bending a symmetrical fiber the breaking point is typically determined by reaching the tensile stress limit. In one embodiment, the effective tensile stress limit is geometrically increased using hollow structures such as tubes. Fiber 110 may be constructed as a hollow tube (Figures 7A, 7B), or the hollow tube may be located only on the outer convex rim of bended fiber 110 (e.g. the large air gap 118 in Figure 2D). The hollow tube may have a circular, oval, or other cross-section so as to increase the natural tendency to collapse inward (Figure 7A). When fiber 110 is bent, strain 171 increases on the outer rim of fiber 110 (Figure 7B). Since the center is hollow, an inward collapse is possible. This collapse means a larger bending radius 105 (172A to 172B in Figure 7C), which in turn means effectively weaker stress, hence the possibility of smaller bend radiuses (sharper bends) for the same stress breakage values. The tube wall thickness and material are accommodated to the possibility of bending. This method allows tighter bending of fiber 110 without breaking it. Another possible embodiment is to use serrations on the outside of the fiber bend region, as in Figure 2H, which also effectively reduces the stress values on the outer convex rim.

[0078] In embodiments, cladding 115 may be arranged to become asymmetric in cross section upon application of strain 171 at the specified region. The asymmetry may be expressed in a form of cladding 115, a thickness of cladding 115 and/or in the refractive index of cladding 115. The asymmetry may be configured to focus emitted electromagnetic radiation 152.

[0079] Figures 7A-7C illustrate three type of strains 171. Figure 7A illustrates an asymmetric cross-section of fiber 110, e.g. an elliptic cross-section, which is deformed from state 170A to state 170B with an increased eccentricity. Figure 7B illustrates circular cross-section fiber 110 that is deformed on one side from state 170A to state 170B, resulting in a change in strain 171. Figure 7C illustrates bended fiber 110, in which bending strain is decreased by strain 171 while the bending radius of fiber 110, increases from 172A in state 170 A to 172B in state 170B.

[0080] Figure 7D illustrates that a bend of fiber 110 from state 170A to state 170B results in different strains in an inner side 173A of fiber 110 and in an outer side 173B of fiber 110, both sides with respect to the bending. Hence different strains are experienced by sides 173A, 173B, which may result in changes in the refractive indices of the two sides, causing bend emission to occur on either side, depending on fiber type and design.

[0081] In embodiments, photoelasticity may be used to change the index of refraction under stress, in order to fine-tune the ability of the waveguide (e.g. fiber 110) to discharge energy asymmetrically. The index of refraction of most materials depends on stress. Typically in glass, when stress is increased the index of refraction increases as well. Photoelasticity is caused by the deformation of the electron shells of atoms and molecules and by the orientation of optically anisotropic molecules or components of such molecules; in polymers, it is caused by the uncoiling and orientation of polymer chains. For a small uniaxial tension or compression, Brewster's law is satisfied, such that the optical path equals the index of refraction times the geometrical, or the stress index multiplied by the stress and the geometrical path.

[0082] When a waveguide like an optical fiber is bent, a symmetry break occurs in the stress distribution in the fiber's cross-section. Inner side 173A is compressed and outer side 173B expands, resulting in an increase in tensile stress. Solving the Euler-Bernoulli beam equation implies that pure (convex) bending causes zero stress at the neutral axis (Figure 7D), tensile stress at convex rim 173B, and compressive stress at concave rim 173A; it also implies that the maximum tensile stress occurs at the convex surface and the maximum compressive stress at the concave surface.

[0083] The bend causes a symmetry break between cladding 115 on the inside of the bend, the radiation emitting section, and cladding 115 on the outside of the bend. Typically, the cladding's refraction index is lower than that of core 130 by about 0.5%. A bend in the fiber effectively closes the index gap in compressed side 173A and on the other hand increases the gap on outer side 173B. This makes the light confinement weaker on the inner side making it leakier.

[0084] The asymmetry due to the bend guides the discharge 152. By bending the waveguide and the subsequent increase in the index of refraction specifically at inner side of the bend 173A, the direction of the discharge 152 is controlled. The index differential at the boundary between core 130 and cladding 115 is tailored in accordance with the desired bend that causes discharge 152.

[0085] Figure 7E illustrates bended fiber 110 in cross section, with different thicknesses of cladding 115 that result in sector 120B focusing the emitted electromagnetic radiation 152. The deformation of cladding 115, and the subsequent index change, may further assist in focusing radiation 152 by emitting sector 120B.

[0086] The cross-section of fiber 110 may be designed to control the stress profile. Figure 7E, for example, illustrates emitting sector 120B as a concave part of cladding 115 that is structured to serve as a converging lens at emitting sector 120B. In this case, compressive stresses are increased in the concave side, which changes the indices of refraction in this area, so that in effect a lens in the concave side of cladding 115 is obtained.

[0087] Figures 8A and 8B demonstrate bend emission for the fiber configuration illustrated in Figure 2H (serrated fiber), according to some embodiments of the invention.

[0088] Figure 8A illustrates the power output as percent of the transmitted radiation from the specified region upon bending (broken line) in comparison to emitted radiation through cladding 115A outside emitting sector 120B (solid line). Clear emission peaks are evident at an arc length range of 40-160 μηι of the circular fiber cross section, i.e. in the specified bended sector.

[0089] Figure 8B is a direct photograph of transmitted light in fiber 110, showing emission through the bended side 120B of fiber 110. Generally speaking, the mechanical tension in the bent fiber lowers the refractive index on the external side and increases the refractive index on the inner side, to generate bend emission as a combined result of the geometry and material influence of the bending.

[0090] Figure 9 is a high level schematic flowchart of a method 200 of configuring emission from an optical fiber (stage 201) and removing an obstruction therewith (stage 278), according to some embodiments of the invention.

[0091] Method 200 comprises arranging at least one specified region in the optical fiber to emit transferred electromagnetic radiation from a core through a cladding of the optical fiber upon bending of the optical fiber at the at least one specified region beyond a specified bending threshold (stage 210).

[0092] Method 200 may further comprise configuring the cladding to be asymmetric in cross section at the at least one specified region (stage 220) and to comprise at least one emission sector and at least one non-emitting sector. Method 200 may further comprise setting an effective refractive index ¾ of the at least one emission sector closer to a core refractive index ηκ than a cladding refractive index ΠΜ (stage 230), to yield transmission through the at least one emission sector upon bending of the optical fiber at the at least one specified region beyond a specified bending threshold.

[0093] Setting the effective refractive index n_E (stage 230) may be carried out by at least one of: changing TIM to n_E (stage 232); serrating the cladding (stage 234); micro- structuring the cladding (stage 236); optionally positioning the core asymmetrically or eccentrically within the cladding (stage 238); applying an asymmetric coating onto the cladding (stage 242); and straining the fiber (stage 244), e.g. mechanically, thermally, or using radiation (e.g. ultraviolet light).

[0094] Method 200 may comprise configuring the at least one specified region to emit the electromagnetic radiation in a plane defined by the fiber (stage 250) and removing the obstruction (stage 278) by crossing the obstruction by the plane (stage 280). [0095] Method 200 may further comprise attaching at least one optical fiber with the at least one specified region to a supportive structure (stage 260) and configuring the supportive structure to position the at least one optical fiber with respect to a target in a way that causes bending of the at least one optical fiber beyond the specified bending threshold thereof over the target (stage 270), to emit the electromagnetic radiation at the target (stage 275).

[0096] Removing the obstruction (stage 278) may be carried out by applying to the obstruction at least one specified region of at least one optical fiber arranged to emit transferred electromagnetic radiation from a core through a cladding of the optical fiber upon bending of the optical fiber at the at least one specified region beyond a specified bending threshold (stage 277).

[0097] The at least one optical fiber may be applied to the obstruction (stage 277) by inflating a balloon (stage 295) to which the at least one optical fiber is attached (stage 290) against the obstruction to yield bending of the at least one optical fiber at the at least one specified region beyond a specified bending threshold.

[0098] In embodiments, device 100 and method 200 are used to assist in medical procedures, specifically by soft tissue cutting utilizing fiber-optic bends for laser energy discharge. The natural curvature in clinical settings is used to induce safe, controlled and predetermined laser discharge from the fiber's side for various purposes like soft tissue, cartilage and bone cutting, ablation and coagulation. Furthermore the controlled discharge may be used for other purposes without limitation such as sensing, material processing and other applications.

[0099] Device 100 and method 200 may be used for cutting and/or removing polyps, lesions, soft tissue sarcomas, benign and malignant tumors and other soft tissue applications. In another embodiment it is used for moderate tissue damage treatments like atrial fibrillation, denervation or nerve inhibition and/or excitation and drug activation through photodynamic therapy. Device 100 and method 200 may be used to provide means of transporting of light energy to the desired location, adjusted to the specific geometry and emission of energy to the tissue to allow safe ablation/coagulation/cutting of the tissue in a precise and controlled manner. Device 100 and method 200 may be used in different parts of the animal or human body, such as: the colon, ileum, cecum, esophagus, stomach and all other parts of the digestive system; the urethra, urinary bladder, ureter, kidney or any other part of the urinary system also the vagina, cervix, uterus, ovaries, prostate gland, penis and all other parts of the reproductive system; the nasal and oral cavities, the epiglottis, trachea, bronchus, lungs and all other parts of the respiratory system; the brain, spinal cord and all other parts of the nervous system; as well as all parts of the circulatory system, veins, arteries the heart etc. It may also operate on parts of the skin or dermatology related procedures, plastic and general surgery procedures.

[00100] In embodiments, device 100 and method 200 may be used to treat atherosclerosis by laser atherectomy by delivering the laser energy specifically to the calcified lesion by using its topography to induce the tight bends in the fiber, which in turn causes the beam to "leak" out of the fiber and be transmitted to the lesion. Thus, device 100 and method 200 take advantage of the geometry of the lesion to target the discharge exclusively at the treatment site.

[00101] The following are some non-limiting examples for bending thresholds with respect to various obstructions. It should be noted, as illustrated below, that generally there are two dimensions related to the bending, or curvature radius. One is in the radius of vessel 90 (in a plane perpendicular to the vessel) and the other is related to the longitudinal way along vessel 90 (in a longitudinal cross section of vessel 90). As a result, fiber 110 may be asymmetric and have different dimensions in different directions, or be oriented in different ways along device 100 (and with respect to vessel 90). Bending, or curvature thresholds may differ in different directions, as in the longitudinal axis the reference radius (that of vessel 90 without any obstruction 95) is very large, while in the cross sectional axis the reference radius (without obstruction 95) is much smaller. Hence, different emission parameters may be defined for these directions and may be used to apply coarser of finer treatments, possibly simultaneously in different regions or sequentially and complementary in one region of obstruction 95.

[00102] In non limiting examples, the following may be typical parameters for the bending threshold in cases of different obstructions. In case of coronary lesions having a radius between 0.1 mm and 2 mm, the specified bending threshold may be about two times the lesion radius, or up to five times the lesion radius to achieve a more thorough removal of the lesion. Fiber 110 and device 100 may be adapted or selected according to the specific lesion that is to be treated therewith.

[00103] In case of vascular lesions having a radius between 1 mm and 10 mm, the specified bending threshold may be about two times the lesion radius, or up to five times the lesion radius to achieve a more thorough removal of the lesion. Fiber 110 and device 100 may be adapted or selected according to the specific lesion that is to be treated therewith.

[00104] In case of airway obstruction having a radius between 0.5 mm and 5 mm for small obstructions and having a radius between 5 mm and 20 mm for large obstructions, the specified bending threshold may be about two times the obstruction radius, or up to five times the obstruction radius to achieve a more thorough removal of the obstruction. Fiber 110 and device 100 may be adapted or selected according to the specific obstruction that is to be treated therewith.

[00105] In case of gastrointestinal obstructions having a radius between 10 mm and 100 mm, the specified bending threshold may be about two times the obstruction radius, or up to five times the obstruction radius to achieve a more thorough removal of the obstruction. Fiber 110 and device 100 may be adapted or selected according to the specific obstruction that is to be treated therewith.

[00106] In case of obstructions in water or sewage pipes, having a radius between 50 mm and 500 mm, the specified bending threshold may be about two times the obstruction radius, or up to five times the obstruction radius to achieve a more thorough removal of the obstruction. Fiber 110 and device 100 may be adapted or selected according to the specific obstruction that is to be treated therewith.

[00107] Device 100 may be part of an arterial catheter system which includes a flexible elongate member or catheter with an outer surface, a distal region adapted to enter an artery and a proximal region extending from a patient's vessel, permitting control outside the patient's body by a physician. At the distal region of the catheter is the atherosclerosis treating assembly which may include suction and/or drug administration surface and a balloon expansion unit.

[00108] Figures 10A and 10B schematically illustrate fiber 110 having three emission sectors 120B, 120C and 120D in the emission region and a hook device 100 using this fiber, according to some embodiments of the invention. Emission sectors 120B, 120C and 120D have cladding materials 115B, 115C and 115D respectively, which are different from cladding material 115A in non-emitting sectors 120A and may also be different from each other in the characteristics of emitted radiation 152B, 152C, 152A respectively. For example, central emission sector 120B may be configured to cut tissue, while lateral emission sectors 120C and 120D may be configured to coagulate the sides of the cut by emitting radiation 152C and 152D with specified parameters (e.g. different wavelength ranges, different bending thresholds and different intensities than emitted radiation 152B).

[00109] Figures 11A-11E schematically illustrate device 100 configured as tweezers, according to some embodiments of the invention. Figures 11A and 11B illustrate an open, non-emitting, position and an active position of device 100, respectively. Fiber 110 is integrated within tweezers device 100 in a way that causes bending of fiber 110 upon handling tissue with device 100 and radiation emission from the bended regions which enhances treatment of the handled tissue. For example, fiber 110 may be associated with one arm 310 of tweezers device 100 and fiber bending may occur upon pressing the fiber against a second arm 311 of tweezers device 100. Any of the tweezers' arms may comprise protrusions 313 and/or corresponding recesses 312 to enhance fiber bending upon handling tissue by tweezers 100. Tweezers-like device 100 may comprises surface features designed to control the bending of optical fiber 110 upon tissue contact. Figure llC illustrates tweezers device 100 having multiple fibers 110 which may have differing emission characteristics, e.g. configured to apply different effects to the treated tissue.

[00110] Tweezers device 100 hence allows mechanical handling while using laser for cutting tissue. The emission may be dependent on the extent of the force applied by the physician through the extent of resulting bending of fiber(s) 110. The closer arms 310, 311 are pressed together, the larger becomes the fiber bending and the emitted radiation.

[00111] Figure 11C schematically illustrates designing the surface area of arms 310, 311, i.e. protrusions 313 and recesses 312, to cause different levels of bending of fibers 110 upon using the tweezers. The surfaces of the arms may be designed to cause different intensities of radiation from fibers 110 (as fibers 110 are bended at different levels) and thus applying different levels of treatment to the handled tissue. Fiber parameters and arm surface parameters may be combined to induce variable treatment levels and effects along and across tweezers device 100. For example, a middle more curvy line in Figure 11C may lead to more emission from the central fiber 110 and thereby cut tissue, while the lateral less curvy lines may lead only to a soldering effect on the tissue by the lesser bending of lateral fibers 110. Figure 11D illustrates an embodiment that comprises an additional sensing fiber 315 that may be used to control emitted radiation by fiber 110 by sensing the radiation level emitted therefrom. Some of emitted radiation 152 may enter sensing fiber 315 when the fiber 110 is close to fiber 315 due to the closing of tweezers device 100 and when no tissue obstructs the radiation path. The intensity of the entering radiation may be used to indicate treatment efficiency and provide information on the handled tissue. Any other sensor may be used in place or in addition to additional fiber 315, e.g. a temperature or an impedance sensor.

[00112] Figures HE and 11F illustrate an open, non-emitting, position and an active position of device 100, respectively. Fiber 110 is integrated within tweezers device 100 in a way that causes bending of fiber 110 upon handling tissue with device 100 and radiation emission from the bended regions which enhances treatment of the handled tissue. For example, fiber 110 may be associated with one arm 310 of tweezers device 100 and fiber bending may occur upon pressing the fiber against a second arm 311 of tweezers device 100. In the illustrated embodiment, tweezers-like device 100 comprises one arm 320 that is curved and stiff and a second arm 322 which is flexible to which fiber 110 is attached. Arms 320, 322 may comprise reciprocally engaging tips 321A, 321B respectively that engage upon full closure of device 100. Fiber 110 may be arranged to emit at the resulting bending of flexible second arm 322. Multiple fiber embodiments may be designed to provide varying tissue handling effects.

[00113] In embodiments, fiber 110 may reach tip 321A of arm 322 and be used additionally as a tip-emitting fiber ("straight shot laser").

[00114] Figures 12A and 12B schematically illustrate device 100 with a feedback loop for controlling emitted radiation 152, according to some embodiments of the invention. For example, the feedback loop may be used for sensing data from additional sensing fiber 315 or other sensor illustrated in Figure 11D. Figure 12A illustrates radiation source 70 and a radiation detector 330 which measures radiation after emitted radiation 152 was emitted along the fiber, to determine the extent of radiation emission 152 and hence of treatment. Radiation detector may be replaced or enhanced by a temperature sensor. Figure 12B illustrates tweezers device 100 with fiber 110's emitting regions, from which radiation is emitted. Data from detector 330 may be used to control radiation parameters such as activation, wavelength range and intensity as well as parameters of device 100 - e.g. provide feedback to the treating physician, change device 100' s electronic parameters etc. Detector 330 may measure changes in bend-emitted radiation 152 via the natural changes that occur to the tissues' index of refraction as it is being coagulated or cut.

[00115] Figure 13 schematically illustrates fiber 110 having multiple emission sectors 120B, 120C, 120D, 120E and 120F in the emission region, according to some embodiments of the invention. The emission sectors may be designed to have different bending thresholds, such that emission intensity from fiber 110 has a specified profile with respect to the circumference of the emission region. For example, central sectors may have the lowest bending thresholds (i.e. the largest threshold bending radii) to emit first and most intense for e.g. a cutting treatment, while peripheral sectors may have higher bending thresholds (i.e. smaller threshold bending radii) to emit last and weaker for less intensive tissue treatment e.g. a coagulation or soldering treatment. In embodiments, the configuration of the emission sectors may be symmetric around central sector 120D.

[00116] In addition to providing an emission profile, devices 100 and fibers 110 may be designed to correlate the forces applied thereupon to the intensity of radiation 152, as larger forces produce stronger bending of fibers 110, resulting in more intense radiation. Such designs may enhance the feel provided by device 100 and make the feel more similar to cutting with a regular scalpel mechanically.

[00117] Figure 14 schematically illustrates device 100 for cutting vessels, according to some embodiments of the invention. Device 100 comprises a fixating arm 340 (e.g. a hook) and a cutting arm that comprises fiber 110 that is optionally supported by supporting structure 141 and a second fixating arm 345 that stabilizes target 95 (such as a blood vessel) and fiber 110' s contact thereto. The cutting arm may comprise a single fiber 110, e.g. fiber 110 with multiple emission sectors as illustrated in Figure 13, or multiple fibers 110 with similar or varying characteristics, optionally attached to supporting structure 141. In embodiments, fixating arms 340 and 345 may be part of the supportive structure, as a variation of tweezers-like device 100. Upon pressing fixating arm 340 against the cutting arm (supported by second fixating arm 345) around target 95 such as a blood vessel, cutting of vessel 95 and immediate soldering of the cut ends of vessel 95 are carried out, e.g. by activation of different treatment effects as described above. Alternatively, the cutting arm with second fixating arm 345 may press vessel 95 against fixating arm 340 and either arm may emit radiation to apply the treatment upon vessel 95.

[00118] Figures 15A and 15B illustrate device 100 for treating target 95 by pressing device 100 upon it, according to some embodiments of the invention. Device 100 may be mechanically configured similarly to tweezers device 100 illustrates in Figures HE and 11F, and emit radiation externally, onto target 95 against which device 100 is pressed. Device 100 may have a single arm 350 that supports fiber 110 and allows bending of fiber 110 upon contact with target 95, in accordance with the applied pressure and in correspondence to the form of target 95. For example, fiber 110 may be loosely or movably attached to the tip of arm 350, fiber 110 may be flexible or device 100 may be designed to provide for some lengthening of fiber 110 upon contact with target 95.

[00119] The illustrated tweezers with arms 310 and 311, 320 and 322, 340 and 345 may be embodiments of supportive structure 141 described above.

[00120] In the above description, an embodiment is an example or implementation of the invention. The various appearances of "one embodiment", "an embodiment" or "some embodiments" do not necessarily all refer to the same embodiments.

[00121] Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment.

[00122] Embodiments of the invention may include features from different embodiments disclosed above, and embodiments may incorporate elements from other embodiments disclosed above. The disclosure of elements of the invention in the context of a specific embodiment is not to be taken as limiting their used in the specific embodiment alone.

[00123] Furthermore, it is to be understood that the invention can be carried out or practiced in various ways and that the invention can be implemented in embodiments other than the ones outlined in the description above.

[00124] The invention is not limited to those diagrams or to the corresponding descriptions. For example, flow need not move through each illustrated box or state, or in exactly the same order as illustrated and described.

[00125] Meanings of technical and scientific terms used herein are to be commonly understood as by one of ordinary skill in the art to which the invention belongs, unless otherwise defined.

[00126] While the invention has been described with respect to a limited number of embodiments, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of some of the preferred embodiments. Other possible variations, modifications, and applications are also within the scope of the invention., the scope of the invention should not be limited by what has thus far been described, but by the appended claims and their legal equivalents.

Claims

CLAIMS What is claimed is:

1. An optical fiber comprising a core having a refractive index and a cladding having a refractive index, the optical fiber having at least one specified region of the cladding that is arranged to emit electromagnetic radiation from the core upon bending the optical fiber at the at least one specified region beyond a specified bending threshold.

2. The optical fiber of claim 1, wherein the cladding is asymmetric in cross section at the at least one specified region and comprises at least one emission sector and at least one non-emitting sector.

3. The optical fiber of claim 2, wherein the at least one emission sector has a refractive index larger than a refractive index of the cladding.

4. The optical fiber of claim 3, wherein a difference of the refractive index of the at least one emission sector from the refractive index of the cladding is larger than 0.1%.

5. The optical fiber of claim 2, wherein the at least one non-emitting sector is micro- structured to reduce an effective refractive index thereof below a refractive index of the at least one emission sector.

6. The optical fiber of claim 2, wherein the at least one non-emitting sector is micro- structured to direct radiation toward the at least one emission sector.

7. The optical fiber of claim 6, wherein the at least one micro-structured non-emitting sector comprises at least one of: a grating, and air holes.

8. The optical fiber of claim 2, wherein the optical fiber is an asymmetric Bragg fiber, an asymmetric photonic crystal fiber or an asymmetric holey fiber.

9. The optical fiber of claim 2, wherein the at least one emission sector comprises at least two emission sectors that differ in their specified bending threshold for emission.

10. The optical fiber of claim 9, comprising at least one additional core, wherein the core is associated with one emission sector and at least one additional core associated with corresponding emission sectors.

11. The optical fiber of claim 1, wherein the cladding is radially serrated at the at least one specified region.

12. The optical fiber of claim 1 , wherein the cladding comprises, at the at least one specified region, at least one circle segment having an arc defining the at least one emission sector and further emitting the electromagnetic radiation at a plane.

13. The optical fiber of claim 1, wherein the core is asymmetric in cross section at the at least one specified region and comprises at least one emission sector and at least one non-emitting sector.

14. The optical fiber of claim 1, wherein the core is asymmetrically positioned within the optical fiber at the at least one specified region to define at least one emission sector and at least one non-emitting sector.

15. The optical fiber of claim 1, selected from: a solid core fiber, a hollow fiber, a metallic wave guide, a Bragg fiber and a photonic crystal fiber.

16. The optical fiber of claim 1, further comprising a coating.

17. The optical fiber of claim 16, wherein the coating is missing in the at least one specified region.

18. The optical fiber of claim 16, wherein the coating is asymmetric in cross section at the at least one specified region and comprises at least one emission sector and at least one non-emitting sector.

19. The optical fiber of claim 16, wherein the coating comprises, at the at least one specified region, at least one circle segment having an arc defining the at least one emission sector and further emitting the electromagnetic radiation at a plane.

20. The optical fiber of claim 1 , wherein the cladding comprises, at a tip of the fiber, at least one circle segment having an arc defining at least one tip emission sector emitting the electromagnetic radiation at a plane.

21. The optical fiber of claim 1, wherein the cladding is arranged to become asymmetric in cross section upon application of a strain at the at least one specified region.

22. The optical fiber of claim 21, wherein the asymmetry is in at least one of: a form of the cladding, a thickness of the cladding and the refractive index of the cladding.

23. The optical fiber of claim 21, wherein the asymmetry is configured to focus or enhance the emitted electromagnetic radiation.

24. A device comprising: at least one optical fiber comprising at least a core and a cladding, each optical fiber having at least one specified region of the cladding that is arranged to emit electromagnetic radiation from the core upon bending the optical fiber at the at least one specified region beyond a specified bending threshold; and

at least one light source, arranged to transmit electromagnetic radiation through the at least one optical fiber.

25. The device of claim 24, wherein the at least one optical fiber is formed as a snare arranged to emit the electromagnetic radiation in a plane defined by the snare.

26. The device of claim 25, further comprising a second specified region arranged to emit electromagnetic radiation with specified characteristics at an angle to the plane defined by the snare.

27. The device of claim 24, wherein the at least one optical fiber is bended at an angle and the bend is arranged to emit the electromagnetic radiation in a plane defined by the angle.

28. The device of claim 24, wherein the at least one optical fiber comprises a plurality of optical fibers in a collapsible stent-like configuration.

29. The device of claim 24, wherein the at least one optical fiber is associated with a stent.

30. The device of claim 24, wherein the at least one light source is configured to be activated by induction.

31. The device of claim 24, wherein the at least one light source comprises at least two light sources configured to transmit at least one treatment beam and at least one guiding beam through the at least one optical fiber.

32. The device of claim 24, wherein a tip of the at least one optical fiber is reflective.

33. The device of claim 24, wherein a tip of the at least one optical fiber is arranged to emit radiation.

34. The device of claim 24, further comprising an absorptive sink at an end of the at least one optical fiber.

35. The device of claim 24, further comprising a supportive structure configured to position the at least one optical fiber with respect to a target in a way that causes bending of the at least one optical fiber, to emit the electromagnetic radiation at the target.

36. The device of claim 35, wherein the supportive structure is attached to the at least one optical fiber on an opposite side with respect to the target.

37. The device of claim 35, wherein the supportive structure is a balloon and the at least one optical fiber comprises a plurality of optical fibers wound around the balloon, and wherein the bending of the optical fibers is carried out by inflating the balloon to contact the target.

38. The device of claim 37, wherein the target comprises at least one obstructions.

39. The device of claim 37, wherein the plurality of optical fibers are wound in a configuration that is at least one of: perpendicular, parallel or oblique to a longitudinal axis of the balloon.

40. The device of claim 37, wherein the plurality of optical fibers are wound in a collapsible stent-like configuration.

41. The device of claim 35, wherein the supportive structure is tweezers-like.

42. The device of claim 41, wherein the at least one optical fiber is arranged to apply a specified emission profile across the tweezers-like supportive structure.

43. The device of claim 35, wherein the tweezers-like supportive structure comprises surface features designed to control the bending of the at least one optical fiber upon tissue contact.

44. The device of claim 24, further comprising a detector associated with the at least one optical fiber and arranged to measure and indicate the emitted radiation.

45. A method of configuring emission from an optical fiber, the method comprising arranging at least one specified region in the optical fiber to emit transferred electromagnetic radiation from a core through a cladding of the optical fiber upon bending of the optical fiber at the at least one specified region beyond a specified bending threshold.

46. The method of claim 45, wherein the arranging comprises configuring the cladding to be asymmetric in cross section at the at least one specified region and to comprise at least one emission sector and at least one non-emitting sector, and setting an effective refractive index n_E of the at least one emission sector closer to a core refractive index ηκ than a cladding refractive index n_\i, to yield transmission through the at least one emission sector upon bending of the optical fiber at the at least one specified region beyond a specified bending threshold.

47. The method of claim 46, wherein the setting the effective refractive index n_E is carried out by at least one of: changing Ώ.Μ to ¾; serrating the cladding; micro- structuring the cladding; positioning the core asymmetrically or eccentrically within the cladding; applying an asymmetric coating onto the cladding; and straining the fiber.

48. The method of claim 45, further comprising configuring the at least one specified region to emit the electromagnetic radiation in a plane defined by the fiber.

49. The method of claim 45, further comprising attaching at least one optical fiber with the at least one specified region to a supportive structure and configuring the supportive structure to position the at least one optical fiber with respect to a target in a way that causes bending of the at least one optical fiber, to emit the electromagnetic radiation at the target.

50. A method of removing an obstruction, the method comprising applying to the obstruction at least one specified region of at least one optical fiber arranged to emit transferred electromagnetic radiation from a core through a cladding of the optical fiber upon bending of the optical fiber at the at least one specified region beyond a specified bending threshold.

51. The method of claim 50, wherein the at least one optical fiber is applied to the obstruction by inflating a balloon to which the at least one optical fiber is attached against the obstruction to yield bending of the at least one optical fiber at the at least one specified region beyond a specified bending threshold.

52. The method of claim 50, wherein the at least one specified region is configured to emit the electromagnetic radiation in a plane defined by the fiber, and the applying is carried out by crossing the obstruction by the plane.