Guiding device for axial guidance of a fiber imaging probe

Abstract

The present description relates to a guiding device (300) of a fiber imaging probe comprising a flexible optical fiber (115) and a rigid distal end (111).The guiding device comprises: a head (310) comprising a distal end, a proximal end, an enclosure with a longitudinal guiding axis (Δg) configured to receive in a fixed and removable manner the rigid distal end of the imaging probe; a hollow body (320) comprising a distal end configured to be fixed in a removable manner on the proximal end of the head; an envelope (330) that can be manipulated by hand by a user, comprising a distal end configured to be brought into contact with a sample, the hollow body being configured to be moved in translation inside an enclosure of the envelope along the longitudinal guiding axis; axial adjustment means configured to adjust the distance between the distal end of the head secured to the hollow body and the distal end of the envelope. FIG. 3B.

Description

Title of the invention: Guiding device for axially guiding a fiber imaging probe Technical field

[0001] The present description relates to a guidance device for axially guiding a fiber imaging probe. The present description also relates to a fiber imaging device comprising a fiber imaging probe equipped with such a guidance device and an imaging system using such a fiber imaging device. The present description applies in particular to in vivo imaging of the skin or body cavities, as well as to the imaging of biological samples and to the imaging of 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 standardization of lifestyles. The development of non-invasive optical tools for cancer diagnosis and prognosis therefore appears to be of the utmost importance.

[0003] A major challenge arises from the fact that most tissue lesions are located deep in the 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 fluorescence (2PEF for "2 photon excited fluorescence"), three-photon fluorescence (3PEF for "3 photon excited fluorescence"), coherent anti-Stokes Raman scattering (CARS for "Coherent Anti-Stokes Raman Scattering"). One objective is therefore to develop an endoscope suitable for non-linear imaging, or "non-linear endoscope", minimally invasive, with performances close to those 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 non-linear endoscope comprises a fiber imaging probe configured on the one hand to convey short, high-power light pulses optical 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 imaging probe notably comprises a flexible imaging fiber configured to convey the light pulses to the biological tissue and to collect the non-linear optical signal, and a rigid distal end. The distal end notably comprises a distal optic with an optical axis, a proximal end configured to receive a distal end of the imaging fiber, and may comprise scanning means (or "scanner") 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 with low dispersion and low non-linearity are particularly sought, suitable for the delivery of short and intense pulses. For example, double-clad hollow-core fibers have been described for use in a non-linear endoscope. See [Ref. 2]. Such fibers are notable for their low dispersion and low non-linearity and are thus particularly advantageous for non-linear 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 using a 3-axis stage with micrometric adjustment, in vivo non-linear imaging of the skin requires manual manipulation of the fiber imaging probe.

[0010] Although the fiber imaging probe is flexible and can be handled by hand, the high axial resolution of such a probe limits its use for in vivo imaging of the skin. Indeed, with such a non-linear imaging probe, micrometric axial precision (from a few hundred nanometers to a few micrometers) is sought for positioning. It is thus difficult to position the probe manually 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 suitable for guiding such a fiber imaging probe, which can be handled by hand and is compatible with high imaging precision. Summary of the invention

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

[0013] Furthermore, 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 guiding 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 guidance 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 guide axis and being configured to fixedly and removably receive the rigid distal end of the imaging probe such that the distal optic is located 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 guide axis; - a hollow body comprising a distal end and a proximal end, the distal end of the hollow body being configured to be removably attached 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 guide axis; - axial adjustment means configured to adjust the distance between the distal end of the head secured to the hollow body and the distal end of the casing.

[0016] A guiding device according to the first aspect is easily maneuverable by hand by an operator and makes 3D imaging possible, in particular of biological tissues and 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 envelope in contact with the sample is perfectly controlled. In-vivo imaging of the skin and body cavities, such as the oral cavity, is thus greatly facilitated. Such a guiding device can also be advantageously used for imaging any type of sample that cannot be arranged between slide and coverslip.These may 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 guidance device (head, body and envelope) allows rapid assembly on a fiber imaging probe (less than 5 minutes) despite the flexibility of the optical fiber and the fragility of such a probe. The guiding device can also be adapted to different fiber imaging probes (different external diameters of optical fiber and / or distal end of the probe). Each of the parts can also be easily replaced.

[0018] According to one or more exemplary embodiments, the distal end of the envelope is closed with a window transparent to operating wavelengths of the imaging probe, the imaging wavelengths being able for example to be in ranges between 200 nm and 2.5 microns. The window is for example made of a biocompatible material and which has good resistance to impacts and scratches, for example an aluminosilicate glass, the thickness of which can be for example between 50 microns and 200 microns. The window is advantageously impervious to liquids (for example water, grease, oil, bodily fluids, etc.) so as to limit any contact between the fiber imaging probe and the sample (projections, fluids, etc.). The window can thus protect the distal optics of the fiber imaging probe and contribute to ensuring biocompatibility with the environment.

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

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

[0021] According to one or more exemplary embodiments, the hollow body comprises a wall, an outer surface of which comprises 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 in the casing along the guide axis while minimizing friction. Alternatively, it is possible to adjust an outer diameter of the hollow body with an inner diameter of the enclosure of the casing to allow sliding.

[0022] According to one or more exemplary embodiments, the axial adjustment means comprise: - a first clamping ring configured to be fixed on a collar arranged on an outer surface of the wall of the hollow body; - a second clamping ring configured to be fixed on a collar arranged on an outer surface of the wall of the envelope; - 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 in the enclosure of the casing.

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

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

[0025] Of course, other means, known to those skilled in the art, can be implemented to allow the sliding, and more generally the translation, of the hollow body inside the enclosure of the casing along the longitudinal guide axis. These means include, for example and in a non-limiting manner: a piezoelectric actuator configured to cause the sliding of the hollow body in the enclosure of the casing, any mechanical system allowing the transformation of a rotational movement of the casing into a translational movement of the hollow body (cam system, worm wheel gear, rack with thumbwheel, screw / nut system, pinion and rack system, etc.).

[0026] According to one or more exemplary embodiments, an external surface of the wall of the head comprises a rim configured to abut a rim of an internal surface of the enclosure of the envelope. The cooperation thus achieved between the head and the envelope makes it possible to prevent 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 envelope, if present. The abutting position of the head may also correspond to an initial reference position for sliding the head and body assembly in the envelope.

[0027] According to one or more exemplary embodiments, at least a portion of the head enclosure is rotationally symmetrical with an axis of symmetry which defines the longitudinal guide axis.

[0028] According to a second aspect, the present description relates to a fiber imaging device comprising: - a fiber 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 optical; and - a guiding device according to the first aspect, configured to be held in the hand by a user and configured to axially guide said imaging probe along the longitudinal guiding axis substantially coincident with said optical axis.

[0029] According to one or more exemplary 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 non-linear interaction of the pulses with the sample.

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

[0031] The hollow core comprises, for example, a core within which there is a gas, for example air, or vacuum, and at the periphery of which there is a micro-structured part, for example made of air and glass. The core is single-mode or weakly multi-mode, i.e. capable of propagating one or a few modes, at most approximately 10 modes. The hollow core is configured for guiding light in a first wavelength range. For example, the first wavelength range is between approximately 700 nm and approximately 1800 nm.

[0032] The inner cladding of the double-clad hollow core fiber is, for example, a highly multimode inner cladding, i.e., an inner cladding capable of propagating 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 may be used for a fiber imaging probe according to the second aspect.

[0034] Thus, according to one or more exemplary embodiments, the flexible optical fiber is a fiber with a solid core and double sheath, as described for example in [Ref. 8].

[0035] According to one or more exemplary embodiments, the fiber imaging probe comprises the 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 exemplary embodiments, the distal optic comprises one or more microlenses, with diameters of, for example, between approximately 1 mm and approximately 4 mm, the lens(es) being advantageously achromatic. In the case of an assembly of microlenses, these may be of different focal lengths. The distal optic may also comprise a microlens with a refractive index gradient. The microlens(es) may be glued into a rigid tube, for example made of stainless steel. The distal optic makes it possible to spatially shape an imaging beam.

[0037] The distal optic may be interchangeable.

[0038] According to one or more exemplary embodiments, the fiber imaging probe comprises scanning means (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 which may be housed inside the hollow body of the guidance device.

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

[0040] In the present description, ultra-short pulses are understood to mean pulses with a duration of less than approximately 1 ps, advantageously less than approximately 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 photon excited fluorescence"), three-photon fluorescence (3PEF for "3 photon excited fluorescence"), coherent anti-Stokes Raman scattering (CARS for "Coherent Anti-Stokes Raman Scattering").

[0042] According to one or more exemplary embodiments, in the case of motorized axial adjustment means, the processing unit may be configured to control the axial adjustment means for adjusting the distance between the distal end of the head of the guide device and the distal end of the casing of the guide device. As the distal end of the envelope is configured to be brought into contact with the sample, the processing unit thus controls in particular the distance between the distal end of the head and the sample, and thus the depth at which it is imaged.

[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 one first non-linear optical signal for adjusting 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 of imaging a sample using a non-linear imaging system according to the third aspect, the method comprising: - the placement of the rigid distal end of the fiber imaging probe in the enclosure of the head of the guidance device; - fixing the hollow body of the guide device on the proximal end of the head of the guide device; - the installation of the casing of the guide device, the hollow body being slidably mounted in the casing; - adjusting 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 guide device; - generating at least one first image of said sample at at least one first depth depending on said at least one first predetermined distance.

[0045] According to one or more exemplary embodiments, the method comprises manually moving the guidance device laterally to generate, at said at least one 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 one first depth.

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

[0047] The sample is for example made up of a part of a biological tissue or material, for example a sample made up of a region of the 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 slide and coverslip. It can be a biological sample, but also a sample constituting a part of an inorganic solid object, such as for example 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 characteristics of the invention will appear on reading the description, illustrated by the following figures:

[0049] [Fig. 1], represents a diagram illustrating a nonlinear 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 sectional view of a guidance device according to an example conforming to the present description (translation plate not cut to facilitate understanding);

[0052] [Fig.3B], represents a diagram illustrating the sectional view of the guiding device re shown in [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 guide device according to the present description;

[0054] [Fig.4B], represents a diagram illustrating a sectional view of the head such that re presented in [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 the present description;

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

[0057] [Fig.5C], represents a diagram illustrating a sectional view of the hollow body such as re presented in [Fig.5A];

[0058] [Fig. 6A], represents a diagram illustrating a side view of the envelope in an exemplary guide device according to the present description;

[0059] [Fig.ôB], represents a diagram illustrating a 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 in accordance with the present description;

[0061] [Fig.8A], an in vivo 2-photon fluorescence image of a sample of the human forearm, on 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 buccal (tongue), at a depth of about 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.l] represents a diagram illustrating a non-linear 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 comprises 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.l] are configured for transporting the pulses in free space and comprise, for example, one or more optics 162 and a dichroic element 150. Alternatively, the transport means are fibered.

[0067] The non-linear imaging system 100 further comprises detection means 130 configured for the detection of at least one first non-linear optical signal resulting from the non-linear 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 non-linear optical signal.

[0068] By ultra-short pulses, we understand in the present description pulses of duration less than approximately 1 ps, advantageously less than approximately 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 photon excited fluorescence"), three-photon fluorescence (3PEF for "3 photon 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 the present description comprises a fiber imaging probe equipped with a guidance device 300.

[0071] The fiber 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 the optical fiber 115.

[0072] The distal optic 112 comprises for example one or more microlenses, with diameters of for example between approximately 1 mm and approximately 4 mm, the lens(es) being advantageously achromatic. In the case of an assembly of microlenses, these may be of different focal lengths. The distal optic may also comprise a microlens with a refractive index gradient. The microlens(es) may be glued into a rigid tube, for example made of stainless steel. The distal optic makes it possible to spatially shape an imaging beam. The distal optic may be interchangeable.

[0073] The fiber imaging probe may also comprise 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 images taken in section 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 according to the abbreviation of the English expression “Hollow Core Double Clad”) and referenced 201, 202, 203, 204.

[0076] Such HC-DC fibers comprise 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 low index polymer, i.e. with a refractive index lower than that of the inner cladding.

[0077] The HC-DC fibers further comprise in these examples a micro-structured portion 232 at the periphery of the hollow core, for example made of air and glass, and making it possible to ensure the guidance of the light in the hollow core. The hollow core generally comprises a core within which there is a gas, for example air, or vacuum. The core is single-mode or weakly multi-mode, i.e. capable of propagating one or a few modes, at most approximately 10 modes. For example, for biological sample imaging applications, the first wavelength range is between approximately 700 nm and approximately 1800 nm. The inner cladding is strongly multi-mode, i.e. capable of propagating several hundred to several tens of thousands of modes. For example, for imaging applications of biological samples, the second wavelength range is between about 350 nm and about 2400 nm.

[0078] More specifically, the examples of the 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 due to their microstructure 232 and consequently due to their light guiding mechanism in the hollow core.

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

[0080] [Fig. 3A] represents a diagram illustrating a sectional view of a guidance device 300 according to an example in accordance with the present description. In the figure, the translation stage is not cut to facilitate understanding. [Fig. 3B] represents a diagram illustrating the sectional view of the guidance device shown in [Fig. 3A]. In [Fig. 3B], the fiber imaging probe is shown (not cut to facilitate understanding).

[0081] As illustrated in [Fig.3A] and [Fig.3B], the guide 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 comprises in particular an enclosure with a longitudinal guide axis Ag, the enclosure 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 located 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 guide axis Ag.

[0083] As illustrated in [Fig.3B], the fiber imaging probe comprises in this example a rigid distal end 111 with the distal optic 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 guiding device illustrated in [Fig.3A], [Fig.3B] can be adapted to other fiber imaging probes.

[0084] The hollow body 320 comprises in particular a distal end configured to be removably fixed on a proximal end of the head and the casing 330, adapted to be manipulated 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 guide device 300 further comprises axial adjustment means configured to adjust the distance between the distal end of the head 310 secured 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 comprise a translation plate 360.

[0086] The guiding device 300 is manipulable by hand, forming an “imaging pen”. It comprises three separate parts (310, 320, 330), allowing quick and easy installation on different fiber imaging probes. The parts 310, 320, 330 can be made by known polymer additive manufacturing methods, for example in “Figure 4 Rigid Gray” polymer from 3D Systems ®, a biocompatible polymer according to ISO 10993-5. Other materials can be used.

[0087] The three-piece design of the guide device allows in particular the translation of the hollow body 320 secured to the head 310 in the enclosure of the casing 330. The removable mounting of the head 310 and the body 320 facilitates the insertion of the rigid distal part 111 of the fiber imaging probe. The rigid distal part being able to 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 part (the head 310), with less risk of scratching the distal optic 112. The head with the imaging probe can then be fixed robustly and precisely in the hollow body 320 of greater length.

[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 in the enclosure of the casing, as will be described in more detail later.

[0089] The translation stage may be a miniature translation stage that can be controlled by hand and allows for rigorous and precise translation along the longitudinal guide axis. Of course, it is possible to use a motorized translation stage.

[0090] [Fig.4A] represents a diagram illustrating a side view of the head 310 in an exemplary guide device 300 according to the present description and [Fig.4B] represents a diagram illustrating a 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 guide axis Ag.

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

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

[0094] Due to the three-piece design of the guide 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 imaging probe. In exemplary embodiments, the housing 420 of the head 310 can include multiple internal diameters to fit other fiber imaging probes without the need to change other parts of the guide device.

[0095] As illustrated in [Fig.4A] and [Fig.4B], an outer surface of the wall 410 of the head may include a rim 412 configured to abut a rim of an inner surface of the enclosure of the shell 330. The cooperation thus achieved between the head and the shell makes it possible to prevent 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 shell, if present. The abutting position of the head may also correspond to an initial reference position for sliding the head and body assembly into the shell.

[0096] As illustrated in [Fig.4A] and [Fig.4B], the wall 410 of the head may comprise one or more tapped holes 430. The fixing on the rigid distal part of the fiber imaging probe may then be ensured for example by two headless 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 on the hollow body. A flange 414 may allow the thread to be completed.

[0098] A 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] [Fig.5A] represents a diagram illustrating a projected view of the hollow body 320 in an example of a guide device according to the present description. [Fig.5B] represents a diagram illustrating a side view of the hollow body as shown in [Fig.5A] and [Fig.5C] represents a diagram illustrating a 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 attached to the proximal end 425 of the head.

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

[0102] In practice, the hollow body comprises an enclosure 520 formed inside the wall 510 of larger diameter than that of the head and has a greater length. The hollow body 320 allows the immobilization and protection of the fiber imaging probe in the guidance device and allows the sliding of the body / head assembly in the enclosure of the envelope. In the example of [Fig.5A], [Fig.5B], [Fig.5C], the sliding is made possible by means of three reliefs forming rails 512 arranged symmetrically around the wall 510.

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

[0104] As illustrated in [Fig.5A], [Fig.5B], [Fig.5C], the body 320 may comprise, to provide additional security, one or more threaded holes 530 configured to receive screws for holding the fiber imaging probe in the guide device. Prior to its attachment to the fiber imaging probe, the body 310 is attached at its distal end 523 to the head 310 of the guide device. It is for example screwed by means of the thread 540 which cooperates with the thread 440 of the head. The body is blocked by the rim 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] [Fig.6A] shows a diagram illustrating a side view of the casing 330 in an exemplary guide device according to the present description. [Fig.6B] shows a diagram illustrating a sectional view of the casing as shown in [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 envelope 330 thus comprises a wall 610 adapted for holding in the hand by a user and an enclosure 620 inside the wall, the hollow body 320 being configured to be moved in translation inside the enclosure of the envelope along the longitudinal guide axis. The envelope further comprises a distal end 623 configured to be brought into contact with a sample.

[0109] In exemplary embodiments, 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 having good resistance to impacts and scratches, for example an aluminosilicate glass, the thickness of which may be for example between 50 microns and 200 microns. The window is advantageously impervious to liquids (for example water, grease, oil, bodily fluids, etc.) so as to limit any contact between the fiber imaging probe and the sample (projections, fluids, etc.). The window can thus protect the distal optics of the fiber imaging probe and contribute to ensuring biocompatibility with the environment.

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

[0112] The sliding of the body secured to the head in the enclosure 620 of the envelope makes it possible to change the imaging plane without lateral movement. In the exemplary 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 envelope. The sliding can be stopped within the envelope by means of an inner rim 625 blocking the head at a predetermined distance from the distal end 625 of the envelope. The distal optic is thus at a predetermined distance from the distal end of the envelope.

[0113] As illustrated in [Fig.6A], [Fig.6B], a collar 615 may be arranged on an outer surface of the wall 610 to receive the clamping ring 350 ([Fig.3A]). The collar is in this example a larger diameter ring 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, in operation, the sliding of the hollow body in the enclosure of the casing.

[0114] A length of the envelope, measured between the distal end 623 and the end proximal 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] [Fig.7] represents 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 different parts described with reference to the previous figures are mounted with each other. 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, for example between approximately 9 cm and approximately 11 cm. A maximum dimension of the assembly comprising the clamping rings 340, 350 and the plate 360, measured in a plane perpendicular to the longitudinal guide axis, is for example between approximately 30 mm and approximately 40 mm.

[0116] The present description also relates to a method of imaging a sample by means of a non-linear imaging system as described for example by means of [Fig.l]. The sample is for example a biological tissue and material, for example a sample consisting of a region of the 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 slide and coverslip. It can be a biological sample, but also a sample constituting a part of an inorganic solid object, such as for example a painting, a geological object, a sample of textile fabric, an archaeological relic or any manufactured product.

[0117] The method comprises placing the rigid distal end of the fiber imaging probe in the enclosure 420 of the head 310 of the guiding device. The hollow body 320 is then fixed to the proximal end 425 of the head of the guiding device, for example by screwing. The casing 330 of the guiding device is then placed, the body being slidably mounted in the casing.

[0118] The method then comprises adjusting 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 guide device and then generating at least one first image of said sample at at least one first depth depending on said at least one first predetermined distance. The field of view of this first image depends on the scanning means (scanner) of the imaging probe.

[0119] To increase the field of view, the method may comprise laterally moving the guidance device to generate, at said at least one first depth, a plurality of images at different lateral positions of the imaging probe, and determining it mination, from said plurality of images, of a mapping at said at least one first depth. The mapping can be generated in a known manner by merging the images of the plurality of images.

[0120] The method may also comprise moving the distal end of the head, using the axial adjustment means of the guide 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; certain tissues scatter light and do not allow imaging beyond a determined depth, for example equal to a few hundred microns.

[0122] Note that the processing unit 140 ([Fig.l]) can be configured for controlling the 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, the focus is on an element of the sample that emits 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 carried out to find the focus around this position (by looking for the place where there is the most signal) and make a clear image. The recovered images can be processed to reconstruct the complete map in three dimensions.

[0124] [Fig.8A] and [Fig.8B] on the one hand and [Fig.9] on the other hand thus show experimental images obtained by means of a non-linear imaging system according to the present description.

[0125] The nonlinear system used in these examples is a system as illustrated in [Fig.l] 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 having high sensitivity for wavelengths between 300 nm and 720 nm.

[0127] [Fig.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 optical bandpass filter in front of detector 130. The scanner-equipped fiber imaging probe (114, [Fig.3B]) is configured for image acquisition with a 300 micron field of view and a 6Hz acquisition rate; it is thus possible to acquire 6 images per second, 300 microns field of view.

[0128] Image 8A shows keratinocytes that would be impossible to visualize with this same fiber imaging probe without the guidance device 300 due to a lack of precision and stability. This image demonstrates the feasibility of non-linear imaging of in-vivo and unlabeled biological tissues using the guidance device according to the present description.

[0129] [Fig.8B] shows an image of the same sample, but it is a SHG image selected using a 447+ / - 30nm bandpass optical filter in front of the detector 130. The axial adjustment means are set to image in depth at about 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 6Hz; it is thus possible to acquire 6 images per second, of 600 microns of field of view.

[0130] It is observed in image 8B of the collagen fibers that it would again be impossible to visualize with this same fiber imaging probe without the guiding device 300 due to a lack of precision and stability. The axial adjustment also makes it possible to achieve the correct depth. This image also demonstrates the feasibility of non-linear imaging of in-vivo and unlabeled biological tissues using the guiding device according to the present description.

[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 optical bandpass filter in front of the 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, of 120 microns of field of view.

[0132] The axial adjustment means are adjusted to image in depth at approximately 100 microns. In [Fig.9], we see mainly the fluorescence of flavin adenine dinucleotide (FAD) which is 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 imaging probe due to a lack of stability and precision. This image demonstrates the feasibility of non-linear imaging of unlabeled in-vivo biological tissues, in a restricted space such as a body cavity, thanks to the guidance device which is the subject of the present description.

[0133] Although described through a certain number of exemplary embodiments, the methods and devices according to the present description include different variants, modifications and improvements which will appear obvious to those skilled in the art, it being understood that these different variants, modifications and improvements are 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., “Endoscopy fiber probe for nonlinear spectroscopic imaging”, Optica, Vol. 4, No. 5 / May 2017.

Claims

Claims

1. A guiding device (300) configured for guiding a fiber imaging probe, the fiber 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 guiding 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 guiding 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 attached 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 secured to the hollow body and the distal end of the casing.;

2. Guiding device according to claim 1, in which the hollow body is slidably mounted inside the enclosure of the casing along the longitudinal guiding axis.

3. A guiding device according to claim 2, wherein the hollow body comprises a wall (510) an outer surface of which comprises 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 in the enclosure of the casing.

5. A guide device according to any preceding claim, wherein an outer surface of the wall (410) of the head (310) comprises a rim (412) configured to abut a rim (625) of an inner surface of the enclosure of the casing.

6. A guiding device according to any preceding claim, 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 guiding device (300) according to any one of the preceding claims, configured to axially guide said imaging probe along the longitudinal guiding axis (Ag) substantially coincident with said optical axis (Ap).

8. The fiber imaging device of 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 non-linear 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 cable supplying the scanning means, housed inside the hollow body.

10. A non-linear 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 non-linear optical signal resulting from the non-linear optical interaction between said light pulses and the sample; - a processing unit (140) configured to generate an image from said at least one first non-linear optical signal.

11. Non-linear imaging system according to claim 10, wherein: - the axial adjustment means of the guide 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 of imaging a sample using a non-linear imaging system according to any one of claims 10 or 11, the method comprising: - placing the rigid distal end (111) of the fiber imaging probe in the enclosure of the head (310) of the guiding device; - fixing the hollow body (320) of the guiding device on the proximal end of the head of the guiding device; - placing the casing (330) of the guiding device, the hollow body being slidably mounted in the casing; - adjusting 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 guiding device; - generating at least a first image of said sample at at least a first depth depending on said at least a first predetermined distance.

13. An imaging method according to claim 12, further comprising: - laterally moving the guide device to generate, at said at least one first depth, a plurality of images at different lateral positions of the imaging probe, and - determining, from said plurality of images, a mapping at said at least one first depth.

14. Imaging method according to any one of claims 12 or 13, further comprising: - moving the distal end of the head, using the axial adjustment means of the guide device, and - generating at least a second image of said sample at at least a second depth depending on a second distance between the distal end of the head and the distal end of the envelope.

Images