Guidance device for axial guidance of a fiber optic imaging probe

Abstract

The present description relates to a guidance device (300) for a fiber imaging probe comprising a flexible optical fiber (115) and a rigid distal end (111).The guidance device comprises: a head (310) including a distal end, a proximal end, and a housing with a longitudinal guidance axis (Δg) configured to receive the rigid distal end of the imaging probe in a fixed and removable manner; a hollow body (320) including a distal end configured to be removablely attached to the proximal end of the head; a user-operable casing (330) including a distal end configured to be brought into contact with a sample, the hollow body being configured to be moved in translation within a housing of the casing along the longitudinal guidance axis; and axial adjustment means configured to adjust the distance between the distal end of the head attached to the hollow body and the distal end of the casing. FIG. 3B.

Description

Title of the invention: Guidance device for the axial guidance of a fiber optic imaging probe. Technical field

[0001] This description relates to a guidance device for the axial guidance of a fiber-optic imaging probe. This description also relates to a fiber-optic imaging device comprising a fiber-optic imaging probe equipped with such a guidance device and an imaging system using such a fiber-optic imaging device. This description is particularly applicable to in vivo imaging of skin or body cavities, as well as to imaging of biological samples and inorganic solid objects. State of the art

[0002] Invasive cancers are the leading cause of death in developed countries and the second leading cause in developing countries. These figures are increasing due to aging populations and the homogenization of lifestyles. The development of non-invasive optical tools for cancer diagnosis and prognosis is therefore of paramount importance.

[0003] A major challenge arises from the fact that most tissue lesions are located deep within tissues (lungs, stomach, liver, colon) and remain inaccessible to conventional optical imaging techniques. To overcome current technological limitations, non-invasive optical imaging tools have been developed for the rapid detection of metabolic and morphological changes in tissues.

[0004] In particular, it is known [Ref. 1] to combine the advantages of non-linear imaging techniques with those of the minimally invasive endoscopic technique. Non-linear imaging techniques include, in particular, second harmonic generation (SHG for "Second Harmony Generation"), third harmonic generation (THG for "Third Harmony Generation"), two-photon excited fluorescence (2PEF for "2 photons excited fluorescence"), three-photon excited fluorescence (3PEF for "3 photons excited fluorescence"), and coherent anti-Stokes Raman scattering (CARS for "Coherent Anti-Stokes Raman Scattering"). One objective is therefore to develop an endoscope adapted to non-linear imaging, or "non-linear endoscope", minimally invasive, with performance close to that of massive non-linear microscopes (i.e. non-endoscopic), and ideally multimodal, i.e. combining several non-linear imaging modalities in the same device.

[0005] Such a nonlinear endoscope comprises a fiber-reinforced imaging probe configured on the one hand to deliver short, high-power light pulses optically to the biological tissue, so as to obtain a non-linear response from the tissue, and on the other hand to efficiently collect the non-linear signal generated by the tissue and route it to the detection chain.

[0006] Such a fiber-based imaging probe includes, in particular, a flexible imaging fiber configured to deliver light pulses to the biological tissue and to collect the nonlinear optical signal, and a rigid distal end. The distal end includes, in particular, a distal optic with an optical axis, a proximal end configured to receive a distal end of the imaging fiber, and may include scanning means configured to move the distal end of the optical fiber in a plane substantially perpendicular to the optical axis.

[0007] For the fiber imaging probe, optical fibers exhibiting low dispersion and low nonlinearity are particularly sought, as they are suitable for transmitting short, intense pulses. Double-clad hollow-core fibers have, for example, been described for use in a nonlinear endoscope. See [Ref. 2]. Such fibers are notable for their low dispersion and low nonlinearity and are thus particularly advantageous for nonlinear endoscopy.

[0008] It appears that nonlinear imaging can also find applications in in vivo skin imaging. See [Ref. 3].

[0009] However, unlike ex vivo imaging of biological samples which can be positioned on supports manipulated by means of a 3-axis stage with micrometric adjustment, in vivo nonlinear imaging of the skin requires manual manipulation of the fiber imaging probe.

[0010] Although the fiber optic imaging probe is flexible and can be manipulated manually, its high axial resolution limits its use for in vivo skin imaging. Indeed, with such a nonlinear imaging probe, micrometer-level axial accuracy (from a few hundred nanometers to a few micrometers) is required for positioning. It is therefore difficult to manually position the probe to image the imaging plane at the desired axial distance and with sufficient stability to acquire a clear image.

[0011] The present description thus relates to a device adapted for guiding such a fiber imaging probe, which can be handled by hand and is compatible with high imaging accuracy. Summary of the invention

[0012] In the present description, the term "include" means the same as "include" or "contain", and is inclusive or open and does not exclude other elements not described or represented.

[0013] In addition, in the present description, the term "approximately" or "substantially" is synonymous with (means the same as) a lower and / or upper margin of 10%, for example 5%, of the respective value.

[0014] According to a first aspect, the invention relates to a guidance device configured for guiding a fiber imaging probe, the fiber imaging probe comprising at least a first flexible optical fiber and a rigid distal end comprising a distal optic with an optical axis.

[0015] The guiding device according to the first aspect comprises: - a head comprising a distal end and a proximal end, the head comprising a wall and an enclosure within said wall, the enclosure having a longitudinal guiding axis and being configured to receive in a fixed and removable manner the rigid distal end of the imaging probe such that the distal optic is at a predetermined distance from the distal end of the head and such that the optical axis of the distal optic is substantially coincident with the longitudinal guiding axis; - a hollow body comprising a distal end and a proximal end, the distal end of the hollow body being configured to be removably fixed to the proximal end of the head; - an envelope adapted to be handled by hand by a user, comprising a distal end configured to be brought into contact with a sample, the envelope comprising a wall and an enclosure inside said wall, the hollow body being configured to be moved in translation inside the enclosure of the envelope along the longitudinal guiding axis; - axial adjustment means configured to adjust the distance between the distal end of the head attached to the hollow body and the distal end of the casing.

[0016] A guidance device according to the first aspect is easily operated by hand and enables 3D imaging, particularly of tissues and biological materials, with precision and stability without a bulky adjustment stage. Indeed, the distance between the distal end of the head (which receives the distal end of the imaging probe) and the distal end of the sheath in contact with the sample is perfectly controlled. In-vivo imaging of skin and body cavities, such as the oral cavity, is thus greatly facilitated. Such a guidance device can also be advantageously used for imaging any type of sample that cannot be arranged between a slide and coverslip.These can be biological samples, but also samples constituting part of a massive inorganic object, such as a painting, a geological object, a sample of textile fabric, an archaeological relic, or any manufactured product.

[0017] The modular design of the 3-part guiding device (head, body and The envelope allows for rapid assembly onto a fiber optic imaging probe (less than 5 minutes) despite the flexibility of the optical fiber and the fragility of such a probe. The guidance device can also be adapted to different fiber optic imaging probes (different outer diameters of optical fiber and / or distal probe tip). Each component can also be easily replaced.

[0018] According to one or more embodiments, the distal end of the sheath is closed with a transparent window at the operating wavelengths of the imaging probe, the imaging wavelengths being, for example, in the ranges between 200 nm and 2.5 microns. The window is, for example, made of a biocompatible material that exhibits good resistance to shock and scratches, such as an aluminosilicate glass, the thickness of which may be, for example, between 50 microns and 200 microns. The window is advantageously liquid-tight (e.g., water, grease, oil, bodily fluids, etc.) so as to limit any contact between the fiber-reinforced imaging probe and the sample (splashes, fluids, etc.). The window can thus protect the distal optics of the fiber-reinforced imaging probe and contribute to ensuring biocompatibility with the medium.

[0019] According to one or more exemplary embodiments, for example for imaging of a biological sample containing soft tissue requiring greater stability, the distal end of the envelope may remain open and act as a clamp to reinforce adhesion to the tissue.

[0020] According to one or more embodiments, the hollow body is mounted to slide inside the enclosure along the longitudinal guide axis. In other embodiments, the translation of the hollow body inside the enclosure can be achieved by means of a screwing / unscrewing system.

[0021] According to one or more embodiments, the hollow body comprises a wall whose outer surface includes a plurality of guide rails configured to slide in grooves of an inner surface of the wall of the casing. Such guide rails allow the hollow body to slide within the casing along the guide axis while minimizing friction. Alternatively, it is possible to match an outer diameter of the hollow body with an inner diameter of the casing to allow sliding.

[0022] According to one or more embodiments, the axial adjustment means comprise: - a first clamping ring configured to be fixed onto a collar arranged on an external surface of the wall of the hollow body; - a second clamping ring configured to be fixed to a collar arranged on an external surface of the casing wall; - an axial translation plate configured to cooperate with said first clamping ring and said second clamping ring so as to cause, in operation, the sliding of the hollow body within the enclosure of the casing.

[0023] Such an arrangement allows for easy, removable, and robust attachment of the translation plate. In particular, mounting the translation plate with its axis substantially aligned with the longitudinal guide axis is facilitated, thus limiting the risk of deviation of the fiber optic probe.

[0024] According to one or more embodiments, the axial adjustment means can be manually controlled by a user. They include, for example, a manual translation stage. According to one or more embodiments, said axial adjustment means can be motorized. They include, for example, a motorized translation stage, configured, for example, for automated control.

[0025] Of course, other means, known to those skilled in the art, can be used to enable the sliding, and more generally the translation, of the hollow body inside the casing along the longitudinal guide axis. These means include, for example and without limitation: a piezoelectric actuator configured to drive the sliding of the hollow body within the casing, any mechanical system enabling the transformation of a rotational movement of the casing into a translational movement of the hollow body (cam system, worm gear, rack and pinion, screw / nut system, rack and pinion system, etc.).

[0026] According to one or more embodiments, an external surface of the head wall includes an edge configured to abut against an edge of an internal surface of the casing. The resulting interaction between the head and the casing prevents direct contact between the distal end of the head and a surface of the sample, or between the distal end of the head and the window at the distal end of the casing, if present. The abutted position of the head can also serve as an initial reference position for sliding the head and body assembly within the casing.

[0027] According to one or more embodiments, at least a part of the head enclosure has rotational symmetry with an axis of symmetry which defines the longitudinal guiding axis.

[0028] According to a second aspect, the present description relates to a fiber-optic imaging device comprising: - a fiber optic imaging probe comprising: - at least one first flexible optical fiber; - a rigid distal end comprising a distal optic having an optical axis and a proximal end configured to receive a distal end of the fiber optics; and - a guidance device according to the first aspect, configured to be hand-held by a user and configured to axially guide said imaging probe along the longitudinal guidance axis substantially coinciding with said optical axis.

[0029] According to one or more embodiments, said flexible optical fiber is a double-clad hollow-core optical fiber comprising a hollow core configured to carry light pulses to a sample to be imaged and an inner cladding configured to carry an optical signal resulting from a nonlinear interaction of the pulses with the sample.

[0030] A double-clad hollow core fiber in a fiber-reinforced imaging probe according to the second aspect is described for example in [Ref. 4], [Ref. 5], [Ref. 6], [Ref. 7].

[0031] The hollow core comprises, for example, a core containing a gas, for example air or a vacuum, and at the periphery of which is a microstructured portion, for example made of air and glass. The core is single-mode or weakly multimode, that is, capable of propagating one or a few modes, up to a maximum of about 10 modes. The hollow core is configured for guiding light in a first wavelength range. For example, the first wavelength range is between about 700 nm and about 1800 nm.

[0032] The inner cladding of the double-clad hollow-core fiber is, for example, a highly multimode inner cladding, that is, an inner cladding capable of propagating from several hundred to several tens of thousands of modes, for example, between 100 and 100,000. The inner cladding is configured for guiding light in a second wavelength range. For example, the second wavelength range is within the transparency band of the glass that constitutes the inner cladding of the double-clad hollow-core fiber, for example, between approximately 350 nm and approximately 2400 nm for a silica double cladding.

[0033] Other known flexible optical fibers can be used for a fiber-based imaging probe according to the second aspect.

[0034] Thus, according to one or more embodiment examples, the flexible optical fiber is a solid core, double-clad fiber, as described for example in [Ref. 8].

[0035] According to one or more embodiments, the fiber imaging probe comprises a first flexible optical fiber and a second flexible optical fiber. One of the optical fibers is configured to carry light pulses to a sample to be imaged, and the other optical fiber is configured to carry an optical signal resulting from a nonlinear interaction of the pulses with the sample. Such an arrangement is described, for example, in [Ref. 9].

[0036] According to one or more embodiments, the distal optics comprise one or more microlenses, with diameters, for example, between approximately 1 mm and approximately 4 mm in diameter, the lens(es) being advantageously achromatic. In the case of a microlens assembly, these can have different focal lengths. The distal optics may also include a refractive index gradient microlens. The microlens(es) can be bonded within a rigid tube, for example, made of stainless steel. The distal optics allows for the spatial shaping of an imaging beam.

[0037] The distal optics can be interchangeable.

[0038] According to one or more embodiments, the fiber imaging probe includes scanning means configured to move the distal end of the optical fiber in a plane substantially perpendicular to the optical axis. The scanning means may be powered by an electrical cable that can be housed inside the hollow body of the guidance device.

[0039] According to a third aspect, the present description relates to a nonlinear imaging system for a sample comprising: - a fiber optic imaging device according to the second aspect; - a light emission source configured for the emission of ultrashort light pulses and means of transporting said light pulses in said at least a first optical fiber of the imaging probe of the imaging device; - detection means configured for the detection of at least one first nonlinear optical signal resulting from the nonlinear optical interaction between said light pulses and the sample; - a processing unit configured to generate an image from said at least one first nonlinear optical signal.

[0040] In the present description, ultra-short pulses are understood to mean pulses of duration less than about 1 ps, advantageously less than about 200 fs.

[0041] The linear imaging system can be configured, in a known manner, for imaging using second harmonic generation (SHG for "Second Harmony Generation"), third harmonic generation (THG for "Third Harmony Generation"), two-photon fluorescence (2PEF for "2 photons excited fluorescence"), three-photon fluorescence (3PEF for "3 photons excited fluorescence"), coherent anti-Stokes Raman scattering (CARS for "Coherent Anti-Stokes Raman Scattering").

[0042] According to one or more embodiments, in the case of motorized axial adjustment means, the processing unit can be configured to control the axial adjustment means for adjusting the distance between the distal end of the guide device head and the distal end of the guide device housing. Since the distal end of the envelope is configured to be in contact with the sample, the processing unit controls, in particular, the distance between the distal end of the head and the sample, and thus the depth at which imaging takes place.

[0043] In such a system, the adjustment of the distance between the distal end of the head and the distal end of the envelope can be automated, for example as a function of said at least a first nonlinear optical signal to adjust the focus, and / or as a function of predetermined depth values ​​at which the sample is to be imaged.

[0044] According to a fourth aspect, the present description relates to a method for imaging a sample using a nonlinear imaging system according to the third aspect, the method comprising: - the placement of the rigid distal end of the fiber optic imaging probe within the housing of the guidance device head; - the fixing of the hollow body of the guiding device onto the proximal end of the head of the guiding device; - the installation of the housing for the guide device, the hollow body being mounted to slide within the housing; - the setting of a first predetermined distance between the distal end of the head and the distal end of the envelope in contact with the sample by means of the axial adjustment means of the guiding device; - the generation of at least one first image of said sample at at least one first depth as a function of said at least one predetermined first distance.

[0045] According to one or more embodiments, the method includes manually moving the guidance device laterally to generate, at said at least a first depth, a plurality of images at different lateral positions of the imaging probe, and determining, from said plurality of images, a map at said at least a first depth.

[0046] According to one or more embodiments, the method comprises moving the distal end of the head, by means of the axial adjustment means of the guidance device, and generating at least a second image of said sample at at least a second depth as a function of a second distance between the distal end of the head and the distal end of the envelope.

[0047] The sample is, for example, a portion of a biological tissue or material, such as a sample consisting of a region of skin or a wall of a body cavity, like the oral cavity. A sample can generally be any type of sample that cannot be arranged between a slide and coverslip. It can be a biological sample, but also a sample constituting part of a solid inorganic object, such as a painting, an object geological, a sample of textile fabric, an archaeological relic or any manufactured product. Brief description of the figures

[0048] Other advantages and features of the invention will become apparent from the description, illustrated by the following figures:

[0049] [Fig. 1], represents a diagram illustrating a non-linear imaging system comprising a fiber imaging probe equipped with a guidance device according to the present description;

[0050] [Fig.2], represents cross-sectional images of examples of optical fibers used in a fiber imaging probe according to the present description, here double-clad hollow core fibers;

[0051] [Fig. 3A] represents a diagram illustrating a cross-sectional view of a guiding device according to an example conforming to this description (translation plate not cut to facilitate understanding);

[0052] [Fig. 3B], represents a diagram illustrating the cross-sectional view of the guiding device re presented on [Fig.3A], with the fiber imaging probe (uncut fiber imaging probe for ease of understanding);

[0053] [Fig.4A], represents a diagram illustrating a side view of the head in an example of a guidance device as described herein;

[0054] [Fig.4B], represents a diagram illustrating a cross-sectional view of the head such as re presented on [Fig.4A];

[0055] [Fig. 5A], represents a diagram illustrating a projected view of the hollow body in a example of a guidance device according to this description;

[0056] [Fig. 5B], represents a diagram illustrating a side view of the hollow body such as re presented on [Fig.5A];

[0057] [Fig. 5C], represents a diagram illustrating a cross-sectional view of the hollow body as shown presented on [Fig.5A];

[0058] [Fig. A], represents a diagram illustrating a side view of the envelope in an example of a guiding device according to the present description;

[0059] [Fig.ôB], represents a diagram illustrating a cross-sectional view of the envelope as shown in [Fig.ôA];

[0060] [Fig.7], represents a diagram illustrating a side view of a fiber imaging probe with a guidance device, according to an example conforming to the present description;

[0061] [Fig.8A], an in vivo 2-photon fluorescence image of a sample of the human forearm, at the surface of the skin, with a field of view of 300 microns.

[0062] [Fig.8B], an in vivo SHG image of the same sample as that imaged in [Fig.8A], at a depth of approximately 200 microns, with a field of view of 600 microns.

[0063] [Fig.9], an in vivo 2-photon fluorescence image of a cavity sample human oral cavity (tongue), at a depth of approximately 100 microns, with a field of view of 120 microns. Detailed description of the invention

[0064] In the figures, the elements are not shown to scale for better visibility.

[0065] Fig. 1 represents a diagram illustrating a nonlinear imaging system 100 of a sample 10 and comprising a fiber imaging device 110 with a fiber imaging probe equipped with a guidance device 300 according to the present description.

[0066] The nonlinear imaging system 100 further includes a light emission source 120 configured for the emission of ultrashort light pulses and means for transporting the light pulses in an optical fiber 115 of the imaging probe of the imaging device 110. The transport means illustrated in [Fig. 1] are configured for free-space pulse transport and include, for example, one or more optics 162 and a dichroic element 150. Alternatively, the transport means are fiber-linked.

[0067] The nonlinear imaging system 100 further includes detection means 130 configured for the detection of at least one first nonlinear optical signal resulting from the nonlinear optical interaction between the light pulses and the sample 10 and a processing unit 140 configured to generate an image from said at least one first nonlinear optical signal.

[0068] In the present description, ultra-short pulses are understood to mean pulses of duration less than about 1 ps, advantageously less than about 200 fs.

[0069] The linear imaging system can be configured, in a known manner, for imaging using second harmonic generation (SHG for "Second Harmony Generation"), third harmonic generation (THG for "Third Harmony Generation"), two-photon fluorescence (2PEF for "2 photons excited fluorescence"), three-photon fluorescence (3PEF for "3 photons excited fluorescence"), coherent anti-Stokes Raman scattering (CARS for "Coherent Anti-Stokes Raman Scattering").

[0070] The fiber imaging device 110 which is the subject of this description includes a fiber imaging probe equipped with a guidance device 300.

[0071] The fiber-optic imaging probe comprises at least a first flexible optical fiber 115 and a rigid distal end 111 comprising a distal optic 112 having an optical axis Ap and a proximal end configured to receive an end distal of optical fiber 115.

[0072] The distal optics 112 comprise, for example, one or more microlenses with diameters ranging, for example, from approximately 1 mm to approximately 4 mm, the lens(es) advantageously being achromatic. In the case of a microlens assembly, these may have different focal lengths. The distal optics may also comprise a refractive index gradient microlens. The microlens(es) may be bonded in a rigid tube, for example, made of stainless steel. The distal optics allow for the spatial shaping of an imaging beam. The distal optics may be interchangeable.

[0073] The fiber imaging probe may also include scanning means 114 (or "scanner") configured to move the distal end of the optical fiber in a plane substantially perpendicular to the optical axis. The scanning means may be powered by an electrical cable 118.

[0074] The flexible optical fiber 115 is, for example, a double-clad hollow-core optical fiber comprising a hollow core configured to carry light pulses to a sample to be imaged and an inner cladding configured to carry an optical signal resulting from a non-linear interaction of the pulses with the sample.

[0075] Fig. 2 represents cross-sectional images of examples of optical fibers used in a fiber imaging probe according to the present description, here hollow core double-clad fibers (or HC-DC for short) and referenced 201, 202, 203, 204.

[0076] Such HC-DC fibers include, in exemplary embodiments, a hollow core 231 configured for guiding light in a first wavelength range and a double cladding. The double cladding comprises a highly multimode inner cladding 235, configured for guiding light in a second wavelength range, and an outer cladding, not shown in the images, for example, an outer cladding made of a low-index polymer, i.e., with a refractive index lower than that of the inner cladding.

[0077] In these examples, the HC-DC fibers also include a microstructured portion 232 at the periphery of the hollow core, for example, made of air and glass, which guides the light within the hollow core. The hollow core generally comprises a core containing a gas, for example, air, or a vacuum. The core is single-mode or weakly multimode, that is, capable of propagating one or a few modes, up to a maximum of about 10 modes. For example, for biological sample imaging applications, the first wavelength range is between about 700 nm and about 1800 nm. The inner cladding is highly multimode, that is, capable of propagating from several hundred to several tens of thousands of modes. For example, for imaging applications of biological samples, the second range of wavelengths is between approximately 350 nm and approximately 2400 nm.

[0078] More specifically, the examples of HC-DC fibers illustrated by means of images 201 - 204 are described respectively in [Ref. 4], [Ref. 5], [Ref. 6], [Ref. 7]. They differ in particular with regard to their microstructure 232 and consequently with regard to their light guidance mechanism in the hollow core.

[0079] Of course, other imaging optical fibers can be used in the context of this description.

[0080] Figure 3A shows a schematic diagram illustrating a cross-sectional view of a guidance device 300 according to an example conforming to this description. In the figure, the translation stage is not cut off for ease of understanding. Figure 3B shows a schematic diagram illustrating the cross-sectional view of the guidance device shown in Figure 3A. In Figure 3B, the fiber imaging probe is shown (not cut off for ease of understanding).

[0081] As illustrated in [Fig.3A] and [Fig.3B], the guiding device comprises a head 310, a hollow body 320 and a casing 330, each of these parts being described in more detail by means of the following figures.

[0082] The head 310 includes in particular a housing with a longitudinal guiding axis Ag, the housing of the head 310 being configured to receive in a fixed and removable manner the rigid distal end 111 of the fiber imaging probe such that the distal optic 112 is at a predetermined distance from a distal end of the head and such that the optical axis Ap of the distal optic is substantially coincident with the longitudinal guiding axis Ag.

[0083] As illustrated in [Fig. 3B], the fiber imaging probe in this example comprises a rigid distal end 111 with the distal optics 112, scanning means 114, and a sleeve 116 configured to reinforce the junction between the imaging fiber 115 and the rigid distal end. Of course, the guidance device illustrated in [Fig. 3A], [Fig. 3B] can be adapted to other fiber imaging probes.

[0084] The hollow body 320 includes in particular a distal end configured to be removably fixed on a proximal end of the head and the casing 330, adapted to be handled by hand by a user, comprising an enclosure inside which the hollow body 320 can be moved in translation along the longitudinal guide axis Ag.

[0085] The guiding device 300 further includes axial adjustment means configured to adjust the distance between the distal end of the head 310 attached to the hollow body 320 and the distal end of the casing 330. In the example of [Fig.3A] and [Fig.3B], the axial adjustment means include a translation plate 360.

[0086] The guidance device 300 is hand-operated, forming an "imaging pen." It comprises three separate parts (310, 320, 330), allowing for quick and easy attachment to various fiber-optic imaging probes. Parts 310, 320, and 330 can be manufactured using known polymer additive manufacturing processes, for example, from 3D Systems®'s "Figure 4 Rigid Gray" polymer, a biocompatible polymer according to ISO 10993-5. Other materials may also be used.

[0087] The three-piece design of the guidance device allows, in particular, the translation of the hollow body 320, which is integral with the head 310, within the enclosure of the casing 330. The removable assembly of the head 310 and the body 320 facilitates the insertion of the rigid distal portion 111 of the fiber optic probe. Since the rigid distal portion can have a length of between approximately 4 cm and approximately 10 cm, advantageously between approximately 4 cm and approximately 7 cm, its insertion is facilitated in a shorter piece (the head 310), with less risk of scratching the distal optics 112. The head with the imaging probe can then be securely and precisely fixed in the longer hollow body 320.

[0088] In the example of [Fig.3A] and [Fig.3B], the axial adjustment means comprise a first clamping ring 340 configured to be fixed on a collar arranged on an outer surface of a wall of the hollow body 320 and a second clamping ring 350 configured to be fixed on a collar arranged on an outer surface of a wall of the casing 330. The adjustment means further comprise an axial translation plate 360 ​​configured to cooperate with said first clamping ring and said second clamping ring so as to cause, in operation, the sliding of the hollow body within the casing, as will be described in more detail later.

[0089] The translation stage can be a miniature, manually controllable stage allowing for precise and accurate translation along the longitudinal guide axis. Of course, a motorized translation stage can also be used.

[0090] Fig. 4A represents a diagram illustrating a side view of the head 310 in an example of a guiding device 300 according to this description and Fig. 4B represents a diagram illustrating a cross-sectional view of the head as shown in Fig. 4A.

[0091] As illustrated in [Fig.4A] and [Fig.4B], the head 310 comprises a distal end 423 and a proximal end 425. The head is generally formed of a wall 410 inside which is formed an enclosure 420 having a longitudinal guiding axis Ag.

[0092] As explained previously, the head 310 is configured to receive the rigid distal end of the imaging probe in a fixed and removable manner such that the distal optic is located at a predetermined distance from the distal end 423 of the head and in such a way that the optical axis Ap of the distal optic is substantially coincident with the longitudinal guiding axis Ag.

[0093] As illustrated in the figures, in exemplary embodiments, at least a portion of the head housing 420 has rotational symmetry with an axis of symmetry that defines the longitudinal guiding axis Ag. In practice, the shape of the head housing 420 of the head 310 is adapted to the rigid distal portion of the fiber-reinforced imaging probe such that the distal optics is located at the said predetermined distance from the distal end 423 of the head, for example at a distance between approximately 10 microns and approximately 50 microns.

[0094] Due to the three-piece design of the guidance device, the head 310 is interchangeable and can be designed with different shapes of the housing 420 to fit the rigid distal portion of the fiber optic imaging probe. In some embodiments, the housing 420 of the head 310 can have several internal diameters to accommodate other fiber optic imaging probes without needing to change the other parts of the guidance device.

[0095] As illustrated in [Fig. 4A] and [Fig. 4B], an external surface of the head wall 410 may include a rim 412 configured to abut against a rim of an internal surface of the casing 330. This interaction between the head and the casing prevents direct contact between the distal end of the head and a sample surface, or between the distal end of the head and the window at the distal end of the casing, if present. The abutted position of the head may also correspond to an initial reference position for sliding the head and body assembly within the casing.

[0096] As illustrated in [Fig.4A] and [Fig.4B], the wall 410 of the head may include one or more tapped holes 430. The attachment to the rigid distal part of the fiber imaging probe can then be ensured, for example, by two set screws screwing into the head 310 and pressing lightly on the rigid distal part.

[0097] As illustrated in [Fig. 4A] and [Fig. 4B], a thread 440 may be present on an outer surface of the wall 410 of the head, at the proximal end 425 of the head, to allow assembly onto the hollow body. A flange 414 may terminate the thread.

[0098] The length of the head, measured between the distal end 423 and the proximal end 425 along the longitudinal guide axis, is, for example, between approximately 20 mm and approximately 30 mm. A maximum dimension of the head, measured in a plane perpendicular to the longitudinal guide axis, is, for example, between approximately 8 mm and approximately 12 mm.

[0099] Figure 5A represents a diagram illustrating a projected view of the hollow body 320 in An example of a guiding device according to this description. [Fig. 5B] shows a diagram illustrating a side view of the hollow body as shown in [Fig. 5A] and [Fig. 5C] shows a diagram illustrating a cross-sectional view of the hollow body as shown in [Fig. 5A].

[0100] As illustrated in [Fig.5C], the hollow body 320 comprises a distal end 523 and a proximal end 525, the distal end 523 of the hollow body being configured to be removably fixed to the proximal end 425 of the head.

[0101] In exemplary embodiments, the hollow body is mounted to slide inside the enclosure along the longitudinal guide axis. The hollow body may then comprise, as illustrated in the figures, a wall 510 whose outer surface comprises a plurality of guide rails 512 configured to slide in grooves (622, [Fig. 6B]) of an inner surface of the enclosure wall.

[0102] In practice, the hollow body comprises a housing 520 formed inside the wall 510, which has a larger diameter than the head and is longer. The hollow body 320 secures and protects the fiber optic imaging probe within the guidance device and allows the body / head assembly to slide within the housing. In the example of [Fig. 5A], [Fig. 5B], [Fig. 5C], this sliding is made possible by means of three raised sections forming rails 512 arranged symmetrically around the wall 510.

[0103] As illustrated in [Fig. 5A], [Fig. 5B], [Fig. 5C], a collar 515 can be arranged on an outer surface of the wall 510 to receive the clamping ring 340 ([Fig. 3A]). In this example, the collar is a ring of larger diameter arranged at the proximal end of the body.

[0104] As illustrated in [Fig. 5A], [Fig. 5B], [Fig. 5C], the body 320 may include, for additional security, one or more threaded holes 530 configured to receive screws for securing the fiber optic imaging probe in the guidance device. Before being attached to the fiber optic imaging probe, the body 310 is fixed at its distal end 523 to the head 310 of the guidance device. For example, it is screwed in by means of the thread 540 which cooperates with the thread 440 of the head. The body is held in place by the flange 414 which terminates the thread 440 ([Fig. 4A], [Fig. 4B]).

[0105] A length of the hollow body, measured between the distal end 523 and the proximal end 525 along the longitudinal guide axis, is for example between approximately 80 mm and approximately 90 mm. A maximum dimension of the hollow body measured in a plane perpendicular to the longitudinal guide axis is for example between approximately 15 mm and approximately 20 mm.

[0106] Figure 6A shows a diagram illustrating a side view of the casing 330 in an example of a guiding device according to this description. Figure 6B shows a diagram illustrating a cross-sectional view of the casing as shown on the [Fig.6A],

[0107] The envelope 330 allows the handling of the fiber device consisting of the guidance device and the fiber imaging probe.

[0108] The casing 330 thus comprises a wall 610 adapted for hand-holding by a user and a housing 620 inside the wall, the hollow body 320 being configured to be moved in translation within the housing of the casing along the longitudinal guide axis. The casing further comprises a distal end 623 configured to be brought into contact with a sample.

[0109] In embodiment examples, as illustrated in [Fig.6B], the distal end 623 of the envelope is closed with a window 630 transparent to operating wavelengths of the imaging probe.

[0110] The window 630 is, for example, made of a biocompatible material with good impact and scratch resistance, for example, an aluminosilicate glass, the thickness of which may be, for example, between 50 microns and 200 microns. The window is advantageously liquid-tight (for example, water, grease, oil, bodily fluids, etc.) so as to limit any contact between the fiber optic probe and the sample (splashes, fluids, etc.). The window can thus protect the distal optics of the fiber optic probe and help ensure biocompatibility with the medium.

[0111] In exemplary embodiments, for example for imaging a biological sample containing soft tissue requiring greater stability, the distal end 623 of the envelope may remain open and act as a clamp to reinforce adhesion to the tissue.

[0112] The sliding of the body attached to the head within the enclosure 620 of the casing allows for a change of imaging plane without lateral movement. In the embodiment illustrated in the figures, the rails 512 of the body 320 slide without lateral movement in the fitted notches 622 formed in an inner surface of the wall 610 of the casing. The sliding can be stopped within the casing by means of an inner rim 625 that locks the head at a predetermined distance from the distal end 625 of the casing. The distal optics are thus located at a predetermined distance from the distal end of the casing.

[0113] As illustrated in [Fig. 6A], [Fig. 6B], a flange 615 can be arranged on an outer surface of the wall 610 to receive the clamping ring 350 ([Fig. 3A]). In this example, the flange is a ring of larger diameter arranged at the proximal end of the casing. The axial translation plate 360 ​​([Fig. 3B]) cooperates with the clamping ring 340 mounted on the body and the clamping ring 350 mounted on the casing so as to cause, during operation, the sliding of the hollow body within the casing.

[0114] A length of the envelope, measured between the distal end 623 and the end The proximal dimension 625 along the longitudinal guide axis is, for example, between approximately 80 mm and approximately 90 mm. A maximum dimension of the envelope measured in a plane perpendicular to the longitudinal guide axis is, for example, between approximately 15 mm and approximately 20 mm.

[0115] Figure 7 shows a diagram illustrating a side view of an example of a fiber imaging device with a fiber imaging probe and a guide device 300, once the various parts described with reference to the preceding figures have been assembled together. A total length of the fiber imaging device measured along the longitudinal guide axis (between the distal end of the casing 330 and the proximal end of the hollow body 320) is, for example, between approximately 7 cm and approximately 15 cm, or, for example, between approximately 9 cm and approximately 11 cm. A maximum dimension of the assembly including the clamping rings 340, 350 and the mounting plate 360, measured in a plane perpendicular to the longitudinal guide axis, is, for example, between approximately 30 mm and approximately 40 mm.

[0116] This description also relates to a method for imaging a sample using a nonlinear imaging system such as that described, for example, in [Fig. 1]. The sample is, for example, a biological tissue or material, such as a sample consisting of a region of skin or a wall of a body cavity, such as the oral cavity. A sample can generally be any type of sample that cannot be arranged between a slide and coverslip. It can be a biological sample, but also a sample constituting part of a solid inorganic object, such as a painting, a geological object, a textile sample, an archaeological artifact, or any manufactured product.

[0117] The method comprises placing the rigid distal end of the fiber-reinforced imaging probe into the housing 420 of the guide head 310. The hollow body 320 is then fixed to the proximal end 425 of the guide head, for example by screwing. The housing 330 of the guide is then put in place, with the body being slidably mounted within the housing.

[0118] The method then comprises setting a first predetermined distance between the distal end of the head and the distal end of the envelope in contact with the sample by means of the axial adjustment means of the guidance device, and then generating at least one first image of said sample at at least one first depth as a function of said at least one predetermined distance. The field of view of this first image depends on the scanning means of the imaging probe.

[0119] To increase the field of view, the method may include the lateral displacement of the guidance device to generate, at said at least a first depth, a plurality of images at different lateral positions of the imaging probe, and the determination from said plurality of images, a map is generated at said at least one first depth. The map can be generated in a known way by merging the images from the plurality of images.

[0120] The method may also include moving the distal end of the head, by means of the axial adjustment means of the guidance device, and generating at least a second image of said sample at at least a second depth.

[0121] The maximum depth is determined in particular according to the distal optics used. In practice, the depth is adapted according to the type of sample; some tissues scatter light and do not allow imaging beyond a certain depth, for example equal to a few hundred microns.

[0122] Note that the processing unit 140 ([Fig.1]) can be configured for the control of axial adjustment means, for example by means of the translation plate 360, [Fig.7],

[0123] For example, the processing unit controls the axial adjustment means according to the collected nonlinear signal. At the maximum signal intensity, for example, focus is placed on an element of the sample emitting the signal. Then, the sample can be scanned in depth. For example, an automatic movement of a chosen step is programmed, then a precise adjustment is made to find the focus around this position (by searching for the area with the strongest signal) and produce a clear image. The recovered images can be processed to reconstruct the complete three-dimensional map.

[0124] Figs. 8A and 8B on the one hand and Fig. 9 on the other hand thus show experimental images obtained using a nonlinear imaging system according to the present description.

[0125] The nonlinear system used in these examples is a system as illustrated in [Fig.1] with a fiber imaging device as illustrated in [Fig.3A], [Fig.3B] and [Fig.7],

[0126] The illumination source is a pulsed titanium sapphire laser with an excitation wavelength of 860 nm and an average power of 100 mW. The pulse duration is 200 fs. The optical fiber 115 is a double-clad hollow-core fiber as described in [Fig. 2] (204). The detector 130 is a HAMAMATSU PHOTONICS® H7422-40 photodetector with high sensitivity for wavelengths between 300 nm and 720 nm.

[0127] Figure 8A shows an in vivo 2-photon fluorescence image of a human forearm sample, at the skin surface, selected using a 565 ± 66.5 nm bandpass optical filter in front of detector 130. The fiber imaging probe equipped with a scanner (114, Figure 3B) is configured for image acquisition with a field of view of 300 microns and a frame rate of 6 Hz; it is thus It is possible to acquire 6 images per second, with a field of view of 300 microns.

[0128] Image 8A shows keratinocytes that could not be visualized with the same fiber-reinforced imaging probe without the 300 guidance device due to a lack of precision and stability. This image demonstrates the feasibility of non-linear imaging of unlabeled in-vivo biological tissues using the guidance device described herein.

[0129] Figure 8B shows an image of the same sample, but this is an SHG image selected using a 447 + / - 30 nm bandpass optical filter in front of detector 130. The axial adjustment means are set to image to a depth of approximately 200 microns. The fiber imaging probe equipped with a scanner (114, [Fig. 3B]) is configured for image acquisition with a field of view of 600 microns and an acquisition rate of 6 Hz; thus, it is possible to acquire 6 images per second, with a field of view of 600 microns.

[0130] Image 8B shows collagen fibers that would again be impossible to visualize with the same fiber-reinforced imaging probe without the 300 guidance device due to a lack of precision and stability. The axial adjustment also allows the correct depth to be achieved. This image also demonstrates the feasibility of non-linear imaging of in-vivo and unlabeled biological tissues using the guidance device described herein.

[0131] Fig. 9 shows an in vivo 2-photon fluorescence image of a sample consisting of a region of the oral cavity (the tongue), the 2-photon fluorescence being selected using a 565+ / - 66.5 nm bandpass optical filter in front of detector 130. The fiber imaging probe equipped with a scanner (114, Fig. 3B) is configured for image acquisition with a field of view of 120 microns and an acquisition rate of 6 Hz; it is thus possible to acquire 6 images per second, with a field of view of 120 microns.

[0132] The axial adjustment means are set to image to a depth of approximately 100 microns. In [Fig. 9], the predominant fluorescence is that of flavin adenine dinucleotide (FAD), a coenzyme present in the cytoplasm of cells. Without the guidance device, it would not be possible to image the interior of the oral cavity with the fiber-reinforced imaging probe due to a lack of stability and precision. This image demonstrates the feasibility of nonlinear imaging of unlabeled in vivo biological tissues in a confined space such as a body cavity, using the guidance device described herein.

[0133] Although described through a number of embodiments, the processes and devices according to this description include various variants, modifications and improvements which will be obvious to those skilled in the art, it being understood that these various variants, modifications and improvements make part of the scope of the invention as defined by the following claims. REFERENCES

[0134] [Ref. 1]: V. Kucikas et al. “Two-Photon Endoscopy: State of the Art and Perspectives”. Mol Imaging Biol (2021).

[0135] [Ref. 2]: D. Septier et al. "Lahel-free highly multimodal nonlinear endoscope", Optics Express 30, 25020-25033 (2022).

[0136] [Ref. 3] K. Kônig, “Review: Clinical in vivo multiphoton FLIM tomography”, Methods Appl. Fluoresc. 8 (2020) 034002.

[0137] [Réf. 4] Y. Y. Wang et al. "Eow loss broadband transmission in hypocycloid-core Kagome hollow-core photonic crystal fiber," Opt. Lett. 36, 669-671 (2011).

[0138] [Réf. 5] G. Bouwmans et al. "Properties ofa hollow-core photonic bandgap fiber at 850 nm wavelength" Opt. Express 11, 1613-1620 (2003).

[0139] [Réf. 6] F. Couny et al. "Génération and Photonic Guidance of Multi-Octave Optical-Frequency Cornbs", Vol 318, Issue 5853, pp. 1118-1121 (2007).

[0140] [Réf. 7] A. Kudlinski, et al., “Double clad tubular anti-resonant hollow core fiberfor nonlinear microendoscopy”, Opt. Express 28 (10), p. 15062-15070 (2020).

[0141] [Ref. 8] G. Ducourthial “Development ofa real-time flexible multiphoton microendoscope for label-free imaging in a live animal”, Sci. Rep. 5, 18303; doi: 10.1038 / srep 18303 (2015).

[0142] [Ref. 9] A. Lukic et al., “Endoscopie fiber probe for nonlinear spectroscopic imaging”, Optica, Vol. 4, No. 5 / May 2017.

Claims

Demands

1. A guidance device (300) configured for guiding a fiber optic imaging probe, the fiber optic imaging probe comprising at least a first flexible optical fiber (115) and a rigid distal end (111) comprising a distal optic (112) having an optical axis (Ap), the device comprising: - a head (310) comprising a distal end (423) and a proximal end (425), the head comprising a wall (410) and an enclosure (420) inside said wall, the enclosure having a longitudinal guidance axis (Ag) and being configured to receive in a fixed and removable manner the rigid distal end of the imaging probe such that the distal optic is at a predetermined distance from the distal end of the head and such that the optical axis (Ap) of the distal optic is substantially coincident with the longitudinal guidance axis (Ag);- a hollow body (320) comprising a distal end (523) and a proximal end (525), the distal end of the hollow body (523) being configured to be removably fixed to the proximal end (425) of the head; - a casing (330) adapted to be handled by hand by a user, comprising a distal end (623) configured to be brought into contact with a sample, the casing comprising a wall (610) and an enclosure (620) inside said wall, the hollow body being configured to be moved in translation inside the enclosure of the casing along the longitudinal guide axis; - axial adjustment means configured to adjust the distance between the distal end of the head attached to the hollow body and the distal end of the casing.

2. A guidance device according to claim 1, in which the hollow body is mounted to slide inside the enclosure of the casing along the longitudinal axis of guidance.

3. A guidance device according to claim 2, wherein the hollow body comprises a wall (510) having an outer surface comprising a plurality of guide rails (512) configured to slide in grooves (622) of an inner surface of the wall of the casing.

4. A guiding device according to any one of claims 2 or 3, wherein the axial adjustment means comprise: - a first clamping ring (340) configured to be fixed on a collar (515) arranged on an outer surface of the wall (510) of the hollow body (320); - a second clamping ring (350) configured to be fixed on a collar (615) arranged on an outer surface of the wall (610) of the casing (330); - an axial translation plate (360) configured to cooperate with said first clamping ring and said second clamping ring so as to cause, in operation, the sliding of the hollow body within the casing.

5. A guidance device according to any one of the preceding claims, wherein an external surface of the wall (410) of the head (310) includes a rim (412) configured to abut with a rim (625) of an internal surface of the enclosure of the casing.

6. A guidance device according to any one of the preceding claims, wherein the distal end of the envelope is closed with a window (630) transparent to operating wavelengths of the imaging probe.

7. Fiber imaging device (110) comprising: - a fiber imaging probe comprising: - at least one first flexible optical fiber (115); - a rigid distal end (111) comprising a distal optic (112) having an optical axis (Ap) and a proximal end configured to receive a distal end of the optical fiber; and - a guidance device (300) according to any one of the preceding claims, configured to axially guide said imaging probe along the longitudinal guidance axis (Ag) substantially coinciding with said optical axis (Ap).

8. Fiber imaging device according to claim 7, wherein said flexible optical fiber is a double-clad hollow-core optical fiber (201-204) comprising a hollow core (231) configured to carry light pulses to a sample to be imaged and an inner cladding (235) configured to carry an optical signal resulting from a nonlinear interaction of the pulses with the sample.

9. A fiber imaging device according to any one of claims 7 or 8, wherein the fiber imaging probe further comprises: - scanning means (114) configured to move the distal end of the optical fiber in a plane substantially perpendicular to the optical axis; and - an electrical power cable for the scanning means, housed inside the hollow body.

10. Nonlinear imaging system (100) of a sample (10) comprising: - a fiber imaging device (110) according to any one of claims 7 to 9; - a light emission source (120) configured for the emission of ultrashort light pulses and means for transporting said light pulses in said at least one first optical fiber (115) of the imaging probe; - detection means (130) configured for the detection of at least one first nonlinear optical signal resulting from the nonlinear optical interaction between said light pulses and the sample; - a processing unit (140) configured for generating an image from said at least one first nonlinear optical signal.

11. Nonlinear imaging system according to claim 10, wherein: - the axial adjustment means of the guidance device being motorized, the processing unit (140) is further configured to control the axial adjustment means for adjusting the distance between the distal end of the head and the distal end of the envelope.

12. A method for imaging a sample using a nonlinear imaging system according to any one of claims 10 or 11, the method comprising: - placing the rigid distal end (111) of the fiber-reinforced imaging probe in the housing of the head (310) of the guidance device; - attaching the hollow body (320) of the guidance device to the proximal end of the head of the guidance device; - placing the casing (330) of the guidance device, the hollow body being mounted to slide within the casing; - setting a first predetermined distance between the distal end of the head and the distal end of the casing in contact with the sample by means of the axial adjustment means of the guidance device; - generating at least one first image of said sample at at least one first depth as a function of said at least one predetermined distance.

13. Imaging method according to claim 12, further comprising: - lateral displacement of the guidance device to generate, at said at least a first depth, a plurality of images at different lateral positions of the imaging probe, and - determination, from said plurality of images, of a map at said at least a first depth.

14. An imaging method according to any one of claims 12 or 13, further comprising: - the displacement of the distal end of the head, by means of the axial adjustment means of the guidance device, and - the generation of at least a second image of said sample at at least a second depth as a function of a second distance between the distal end of the head and the distal end of the envelope.

Images