Implantable brain illumination device with optical probe monitoring solution

Abstract

The invention relates to an implantable illumination device (1) comprising: An optical module (2) configured to generate at least a first optical signal at a first wavelength and a second optical signal at a second wavelength, distinct from said first wavelength; Means for measuring the emission power of the first optical signal and the second optical signal; An optical probe (3) incorporating an optical fiber (30) arranged to guide the first optical signal and the second optical signal; An optical device (34) with a selective filter located at the distal end of the optical fiber (30), comprising reflection means arranged to reflect said second optical signal and generate a return optical signal through said optical fiber; Means for measuring the power of the return optical signal. Figure to be published with the abbreviation: Figure 1

Description

Title of the invention: Implantable brain illumination device with optical probe monitoring solution Technical field of the invention

[0001] The present invention relates to an implantable cerebral illumination device, having in particular means for monitoring its optical probe. State of the art

[0002] For the treatment of certain pathologies of a living being, it has been imagined to optically stimulate an internal zone of a living being.

[0003] For this purpose, devices have been proposed which include a light source and which are implanted at least partially or totally in the living being to illuminate the desired area.

[0004] In particular, we have noticed the interest of such devices for optically illuminating / irradiating certain areas of the human brain.

[0005] However, given the risks associated with implanting such a device in the brain, it is understandable that such a device must be perfectly designed.

[0006] Such a device is known from patent application US2012 / 259393A1. The solution presented in this document is however not complete.

[0007] Another solution is known from patent application WO2016 / 102351A1. The solution presented in this document is however difficult to implement.

[0008] Other solutions are also described in documents US2014 / 074182A and US7003184B2.

[0009] This type of device can also be equipped with means for controlling the signal dose received by the patient. Patent EP3237063 B 1 thus proposes a device equipped with several channels integrated in a catheter, at least one of the channels being dedicated to the emitted signal and another of the channels to guide a return signal in order to monitor the injected signal. The device is however complex in terms of optics and connections and does not allow reliable measurement of the applied dose.

[0010] Patent FR3074693B1 describes a monitoring solution with a return optical fiber twisted around the processing optical fiber. This solution has the same optical drawbacks as those of the solution described in the patent application cited above.

[0011] Patent EP3302687B1 describes a solution using a photodetector at the laser source, but it does not allow the backscattered light to be decorrelated at the different optical interfaces and therefore does not allow precise measurement of the return signal.

[0012] The aim of the invention is to propose an illumination device intended to be implanted at least in part in a living being, in particular to illuminate one or more areas of its brain, said device having an architecture adapted to fulfill such a role. It will in particular have to fulfill one or more of the following objectives: - Allow monitoring of the injected light dose; - Allow monitoring of the probe integrity; - Use bio-compatible materials; - Minimize medical risks during implantation and explantation; - Ensure the aesthetic and physical comfort of the patient; - Be easy to manufacture and easily reproducible; - Allow effective treatment; Statement of the invention

[0013] This aim is achieved by an implantable illumination device comprising: - An optical module configured to generate at least a first optical signal at a first wavelength and a second optical signal at a second wavelength, distinct from said first wavelength, - Means for measuring the transmission power of the first optical signal and the second optical signal, - An optical probe incorporating an optical fiber arranged to guide the first optical signal and the second optical signal between a so-called proximal end through which the first optical signal and the second optical signal are emitted and an opposite distal end located at the end of the optical probe, - An optical device with a selective filter located at the distal end of the optical fiber, comprising reflection means arranged to reflect said second optical signal and generate a return optical signal through said optical fiber, - Means for measuring the power of the return optical signal.

[0014] According to one feature, the optical device comprises a multilayer deposit.

[0015] According to another feature, the multilayer deposit comprises a final layer formed from a passivation layer.

[0016] According to another feature, the optical fiber is stripped at its distal end.

[0017] According to another feature, the optical module comprises several sources light, each dedicated to the emission of a distinct optical signal.

[0018] According to another feature, the optical module comprises a waveguide, comprising several inputs, to each of which is connected a separate light source and a single output.

[0019] According to another feature, the optical module comprises a lens arranged downstream of the output of the waveguide.

[0020] According to another feature, the optical module comprises a beam splitter device, arranged downstream of said lens to transmit a first part of the first optical signal or of the second optical signal emitted to the optical probe and to reflect a second part of the first optical signal or of the second optical signal towards a first photodiode of the optical module.

[0021] According to another feature, the beam splitter device is arranged to reflect said return optical signal towards a second photodiode of the optical module.

[0022] According to another feature, the optical probe comprises a diffuser positioned at the distal end of the optical fiber.

[0023] According to another feature, the optical probe comprises a mirror arranged axially, partially around the diffuser.

[0024] The invention also relates to an optical stimulation system comprising a control and power supply unit and an implantable illumination device, controlled by said control and power supply unit, said implantable illumination device being as defined above.

[0025] According to a feature, the control and power supply unit is configured to analyze the return optical signal in order to detect defects at the optical probe. Brief description of the figures

[0026] Other characteristics and advantages will appear in the detailed description which follows, given with reference to the appended drawings in which: - [Fig.l] schematically represents the illumination device according to the invention, according to a first embodiment; - Figures 2A, 2B and 2C represent three variant embodiments of the optical probe used in the device of the invention; - [Fig.3A] shows in detail the end of the optical fiber of the optical probe of the device of the invention; - [Fig.3B] illustrates an example of the realization of the multilayer deposition at the end of the optical fiber, with a passivation layer; - Figures 4A to 4C show different variant embodiments of the optical module of the device of the invention; - [Fig.5] represents an example of a reflectivity curve obtained for a multilayer deposit used in the invention; - [Fig.6] shows reflectivity curves illustrating an operating principle of the device of the invention;

[0027] Detailed description of at least one embodiment

[0028] In the remainder of the description, the terms "proximal" and "distal" are to be understood taking into account the direction of emission of the optical signals from the source towards the end of the probe.

[0029] The invention relates more particularly to an implantable deep brain illumination device. This device makes it possible in particular to achieve localized illumination (for example in the near infrared or with any other wavelength depending on the treatment envisaged - neuroprotection type treatment, optogenetics) of the target tissues (for example SNc, hippocampus, striatum, etc.) while minimizing medical risks during implantation. This device can be used in particular in the treatment of neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, Huntington's disease, etc.

[0030] In a non-limiting manner, the device 1 may possibly integrate solutions proposing other stimulation modes (electrical, injection, etc.), in order to form so-called hybrid solutions. These solutions are not, however, the subject of the present application.

[0031] Tissue illumination can have different objectives depending on the application: neuroprotection, optogenetics, stimulation, etc. Several targets are involved, for example: the substantia nigra compacta (SNc) which degenerates in Parkinson's disease, the hippocampus, the main nucleus involved in Alzheimer's disease, the striatum for Huntington's disease. Illumination can be provided directly into the tissues (with the risk of additional lesions) or by choosing trajectories passing through the ventricles (cavities allowing the circulation of cerebrospinal fluid CSF) and in contact or close to the structures to be treated (directional illuminators).

[0032] With reference to [Fig.l], the implantable illumination device 1 according to the invention comprises at least two main parts: - A first part comprising an optical module 2, - A second part formed of an optical probe 3 advantageously integrating a single waveguide (optical fiber 30) responsible for guiding the optical signals generated by the optical module 2.

[0033] The device 1 of the invention is intended to be connected to a control and electrical power supply unit. This control and electrical power supply unit advantageously comprises an implantable pulse generator (commonly called IPG for "Implantable Pulse Generator"), referenced IPG in the drawings.

[0034] The device comprises electrical connection means for connecting to said control and power supply unit.

[0035] In a known manner, an implantable pulse generator IPG mainly comprises an electronic card and a battery, rechargeable or not. The electronic card comprises a microcontroller responsible for managing the operation of the generator. The generator advantageously comprises several connection channels.

[0036] Advantageously, the control and power supply unit is part of an overall optical stimulation system, also including said device of the invention.

[0037] The optical module 2 advantageously comprises a single hermetic housing 20 containing the elements necessary for its operation. This housing 20 can be made of titanium or ceramic.

[0038] An electrical connector 21 may be arranged on said housing 20 to connect the IPG control and electrical power supply unit there.

[0039] The optical module 2 is configured to be capable of delivering at least two distinct optical signals, having distinct wavelengths.

[0040] The first optical signal emitted at a first wavelength (for example 670nm) is intended for tissue treatment.

[0041] The second optical signal emitted at a second wavelength (for example 730nm), distinct from the first wavelength, is intended to perform monitoring functions of the device 1, in particular verification of the integrity of the optical probe 3.

[0042] Advantageously, the optical module 2 is configured to be capable of delivering at least three distinct optical signals, having three distinct wavelengths.

[0043] The third optical signal, emitted at a third wavelength (for example 810nm), distinct from the first wavelength and the second wavelength, is for example also intended for the treatment of tissues, in addition to the first optical signal.

[0044] The optical module 2 comprises several light sources 22a, 22b, 22c housed in its housing 20, each capable of emitting a distinct optical signal at the desired wavelength. If the device is capable of emitting optical signals at three distinct wavelengths, it thus comprises three light sources.

[0045] These may be light sources of the light-emitting diode type, of the laser diode type or of the VCSEL (Vertical-Cavity Surface-Emitting Laser) diode type.

[0046] The optical module 2 may comprise a waveguide 23 housed in said housing 20, comprising several inputs, each light source 22a, 22b, 22c being connected to a separate input, and a common output for emitting a single optical signal at a time to the optical probe 3.

[0047] The IPG control and power supply unit makes it possible to control the power supply of the light sources 22a, 22b, 22c, to determine the power values ​​of the signals transmitted and received in return and to record these values.

[0048] The optical module 2 may comprise a lens 24 arranged downstream of said output of the waveguide 23 to collimate the generated light signal. It may in particular be a gradient index lens (so-called "GRIN" lens).

[0049] The optical module 2 comprises a beam splitter device 25 housed in its housing 20, placed downstream of said lens 24 and optimized to transmit a first part of the optical signal leaving the lens 24 to the optical probe 3 and to reflect a second part of the optical signal leaving the lens 24 towards a first photodiode 26 of the optical module 2, this first photodiode then being responsible for measuring the power of the optical signal injected into the optical probe 3.

[0050] Thanks to the presence of the first photodiode 26, the device makes it possible to precisely control the dose of light injected into the surrounding tissues (signal power multiplied by time).

[0051] The splitter device 25 is also chosen to reflect a return optical signal towards a second photodiode 27, then responsible for measuring the power of this return optical signal. From the measurements of the power of the emitted optical signal and the power of the return optical signal, the control and power supply unit IPG can calculate the attenuation and monitor whether it is constant over time. In the event of too great a drop, it can conclude that there is a fault at the optical probe 3.

[0052] The separating device 25 may comprise a separating cube and / or a separating blade. It may in particular be a 95 / 05% type cube, in order to limit the losses of signal useful for processing.

[0053] Any other optical means capable of fulfilling the functions described above could be used. It is thus possible to perform these functions by assembling several optical elements, whether at the level of the waveguide 23 and / or the splitter device 25.

[0054] At the output, the optical module 2 may comprise a porthole 28, for example made of sapphire intended to be crossed by the optical signal emitted by the selected light source.

[0055] It should be noted that the control and power supply unit IPG is configured to control the light sources 22a, 22b, 22c in an adapted manner, according to the treatment to be implemented (on one or more wavelengths) and the probe tests to be carried out (using the wavelength dedicated to the test).

[0056] The optical probe 3 of the device 1 is intended to guide the optical signal supplied at the output of the optical module.

[0057] The optical probe 3 is in the form of a flexible elongated rod, the distal part of which is shown in [Fig.2A], in [Fig.2B] and in [Fig.2C]. The optical probe 3 advantageously has a circular cross-section. For example, the diameter of the section of the probe may be between 0.5 and 2.5 mm, preferably between 0.8 and 1.3 mm to be compatible with the standard tools used in DBS and thus limit surgical risks.

[0058] The optical probe 3 comprises a single waveguide, for example an optical fiber 30, which is fixed, by its proximal end, to the output of the optical module 2 by means of an optical connector 31 or by gluing. The possibility of connecting the probe simplifies the surgical intervention and allows replacement of the optical module in the event of failure of one of the electrical components.

[0059] The optical probe 3 may comprise a lens 32, advantageously with an index gradient. Depending on the configuration, the lens 32 is integrated into the connector 31 or is fitted to the optical fiber 30 when the latter is glued to the optical module 2, the latter then ensuring sealing and advantageously replacing the porthole 28 of the optical module. This variant embodiment is visible in [Fig.4A].

[0060] As can be seen in [Fig.3A], in a non-limiting manner, the optical fiber 30 may conventionally comprise a core 300, around which a coating 301 and a mechanical protective sheath 302 are deposited. The optical fiber 30 may of course have another architecture.

[0061] At its distal end, the optical fiber 30 is stripped, in order to remove its mechanical protective sheath 302.

[0062] A centering ring 33, advantageously made of radiopaque material, can be threaded around this stripped end.

[0063] According to a feature of the invention, at its distal end, the optical probe 3 is equipped with an optical device 34 ([Fig.3A] and [Fig.3B]) having an anti-reflection function for at least the first wavelength emitted by the first light source 22a of the optical module 2 and a reflection function for the second wavelength emitted by the second light source 22b of the optical module 2. If the optical module 2 comprises a third light source 22c emitting an optical signal at the third wavelength, the optical device 34 is adapted to transmit this third wavelength.

[0064] The reflection function is fulfilled when at least 10% of the power of the emitted optical signal (measured using the first photodiode) is measured in return by the second photodiode 27, advantageously at least 50%.

[0065] Generally speaking, it should be understood that it is possible to adapt the level of reflection but that one of the objectives is to obtain a solution in which the parasitic reflections on the processing signal are low, for example less than 5%, advantageously less than 2%.

[0066] The transmission function (anti-reflection) is fulfilled when at least 70% of the power of the emitted optical signal is transmitted at the level of the optical device 34, ideally at least 93%, or even 99%.

[0067] This optical device 34 is adapted to the stripped distal end of the optical fiber 30, transversely to the axis of the fiber, to be crossed by the selected optical signal guided by the fiber 30.

[0068] The optical device 34 can be produced in the form of a multilayer deposit made at the distal end of the optical fiber, downstream of the self-centering ring 33, the layers being oriented transversely to the axis of the fiber. The deposit thus forms a plug engaged on the distal end of the optical fiber. As shown in [Fig.3B], a final layer is a passivation layer 340.

[0069] The layers of the deposit are chosen in a suitable manner in index and thickness to obtain the optical functions of transmission and reflection at the wavelengths, according to the principles described above.

[0070] In a non-limiting manner, from the inside to the outside, the deposit may comprise, for example, an alternation of layers made of A12O3 and MgF2,

[0071] Any other assembly of layers could be envisaged, provided that the intended functions are fulfilled.

[0072] [Fig. 5] shows the reflectance curve obtained for the optical device made by a multilayer deposition such as that described above. In this figure, it can be seen that the device is transparent at the first wavelength of 670nm as well as at the third wavelength of 808nm but that it is generally reflective at the second wavelength of 730nm. It can thus ensure transmission of the signals necessary for processing and reflection of the test signals intended for monitoring the probe.

[0073] In [Fig.2A], the signal is emitted at the end of the probe, via the distal end of the optical fiber 30.

[0074] Advantageously and optionally, the optical probe 3 may also comprise an optical diffuser 35 fixed, for example using an optical glue 36, on the distal end of the optical fiber 30. The diffuser may be an independent part made for example of silicone or epoxy resin loaded with TiO2 or photo inscribed in a silica waveguide.

[0075] This diffuser 35 makes it possible to diffuse the light signals coming from the sources and guided by the optical fiber 30. If the diffuser 35 is not present, at the output of the optical fiber, the beam is emitted axially at the end of the probe 3.

[0076] At the distal end of the diffuser 35, the probe may include a radiopaque element 37 to facilitate control of the placement of the probe, during and after surgery. This element 37 complements the radiopaque self-centering ring 33 described above to facilitate implantation of the device.

[0077] Advantageously, as shown in [Fig.2B], the optical probe 3 may comprise a mirror 38, for example with a half-moon cross-section, arranged along the length of the diffuser, making it possible to obtain a beam laterally to the probe.

[0078] Over its entire length, the optical probe 3 comprises an external sheath formed of a coating 39 (for example made of optical silicone or equivalent). This coating takes the optical fiber and all of the elements described above.

[0079] At its distal end, the optical probe 3 advantageously has a so-called atraumatic shape, for example oblong or hemispherical, this shape being produced by shaping said coating 39.

[0080] According to a particular aspect of the invention, the optical signal (at the second wavelength) is used for testing / monitoring. This test signal can be transmitted on demand or automatically, at regular intervals or not. It is controlled by the control and power supply unit IPG. After transmission, the optical test signal is first captured, via the splitter device 25, by the first photodiode 26. The signal is then reflected (ideally at least 50%) by the optical device 34, to provide a return optical test signal, which is sent back by the splitter device 25 to the second photodiode 27.

[0081] The control and power supply unit can then carry out various processing operations, in particular analyzing whether the return optical test signal remains similar over time, in order to: - Detect possible faults in optical probe 3; - Check the optical connection of optical probe 3 on optical module 2;

[0082] The optical processing signals emitted at other wavelengths must generate very weak return signals, in comparison with the return optical test signal. Thanks to this test principle, it is thus possible to monitor the state of the optical fiber and the level of propagation of the optical signal, by determining any losses, in the event of degradation at the level of the optical probe 3.

[0083] It is possible to provide different arrangements of the optical module 2 and its elements relative to the optical probe 3. The inputs of the waveguide can be axial ([Fig.4A]) or radial ([Fig.4B] and [Fig.4C]) and the output axial.

[0084] The module housing may for example be oriented in the axis of the optical fiber 30 ([Fig.4A] and [Fig.4C]) or at right angles to it ([Fig.4B]). different embodiment variants described are of course adaptable to each of these different configurations and arrangements.

[0085] It should be noted that the solution of the invention is compatible with an optical probe 30 inserted into the central channel of a DBS probe, for example associated with an electrical stimulation solution.

[0086] It may be useful to use several tissue treatment wavelengths, for example between 650 and 950nm. In this case, the use of a test source at a wavelength lower than 650nm may be considered.

[0087] In the case of dual wavelength (or more) illumination used for tissue treatment and where the electrical consumption of the device is not a constraint, it is possible to use one of the two lengths for the test signal by accepting to lose signal for one of the two sources (670nm for example in the diagram with a reflectivity of 24%, 18%, 12%...) with lossless transmission at 810nm. [Fig.6] illustrates this principle. It can be seen that the level of reflectivity obtained thanks to the optical device 34 located at the end of the optical fiber can be adapted to the desired signal to guarantee the principle of monitoring curves C1, C2, C3 and C4), while maintaining the possibility of easily distinguishing the return optical test signal, compared to signals which would be reflected at other wavelengths (treatment signal at 810nm).

[0088] The solution of the invention has numerous advantages, including: - It allows the dose of illumination supplied at the end of the probe to be precisely adjusted; - It allows us to trace the type of fault in the event of a failure, by determining whether it is a simple degradation of the waveguide (which may be acceptable), measurable by a loss of propagation, whether it is a break in the optical fiber or an optical connection problem; - Solution compatible with several illumination wavelengths; - Device compatible with a standard IPG type control and power supply unit, requiring only software adaptation; - Compact device (e.g. diameter 0.8 or 1.3mm at the probe level) suitable for deep stimulation surgery, using only one optical fiber for the propagation of the different signals, processing and testing; - Modular and removable solution with possible optical connector between the probe and the optical module; - MRI compatibility; - Long-term biocompatibility; Stimulation possibly adaptable, electrical and / or optical with choice of stimulation wavelength;

Claims

Claims

1. Implantable illumination device (1) comprising: - An optical module (2) configured to generate at least a first optical signal at a first wavelength and a second optical signal at a second wavelength, distinct from said first wavelength, - Means for measuring the emission power of the first optical signal and the second optical signal, - An optical probe (3) incorporating an optical fiber (30) arranged to guide the first optical signal and the second optical signal between a so-called proximal end through which the first optical signal and the second optical signal are emitted and an opposite distal end located at the end of the optical probe (3), - Characterized in that it comprises: - An optical device (34) with a selective filter located at the distal end of the optical fiber (30),comprising reflection means arranged to reflect said second optical signal and generate a return optical signal through said optical fiber - Means for measuring the power of the return optical signal, - The optical device (34) comprising a multilayer deposit, - The optical module (2) comprising several light sources (22a, 22b, 22c), each dedicated to the emission of a distinct optical signal, - The optical module (2) comprising a waveguide (23), comprising several inputs, to each of which is connected a distinct light source and a single output, - The optical module (2) comprising a lens (24) arranged downstream of the output of the waveguide.,

2. Device according to claim 1, characterized in that the multilayer deposit comprises a last layer formed from a passivation layer (340).

3. Device according to claim 1 or 2, characterized in that the optical fiber (30) is stripped at its distal end.

4. Device according to claim 1, characterized in that the optical module comprises a beam splitter device (25), arranged downstream of said lens (24) to transmit a first part of the first optical signal or of the second optical signal emitted to the optical probe (3) and to reflect a second part of the first optical signal or of the second optical signal towards a first photodiode (26) of the optical module (2).

5. Device according to claim 4, characterized in that the beam splitter device is arranged to reflect said return optical signal towards a second photodiode (27) of the optical module (2).

6. Device according to one of claims 1 to 5, characterized in that the optical probe (3) comprises a diffuser (35) positioned at the distal end of the optical fiber (30).

7. Device according to claim 6, characterized in that the optical probe (3) comprises a mirror (38) arranged axially, partially around the diffuser (35).

8. Optical stimulation system comprising a control and power supply unit and an implantable illumination device, controlled by said control and power supply unit, characterized in that the implantable illumination device is as defined in one of claims 1 to 7.

9. System according to claim 8, characterized in that the control and power supply unit is configured to analyze the return optical signal in order to detect defects at the optical probe.

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