FR3126318A1 - Implantable brain illumination device with optical probe monitoring solution - Google Patents

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 transmission power of the first optical signal and of 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 reflecting means arranged to reflect said second optical signal and generate a return optical signal through said optical fiberMeans for measuring the power of the return optical signal. Figure to be published with abstract: Figure 1

Description

Implantable brain illumination device with optical probe monitoring solution

Technical field of the invention

The present invention relates to an implantable cerebral illumination device, having in particular means for monitoring its optical probe.

State of the art

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

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

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

However, given the risks associated with the implantation of such a device in the brain, it is understood that such a device must be perfectly designed.

Such a device is known from patent application US2012/259393A1 . However, the solution presented in this document is not complete.

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

Other solutions are also described in documents US2014/074182A1 and US7003184B2 .

This type of device can also be provided with means making it possible to control the dose of signal received by the patient. Patent EP3237063 B 1 thus proposes a device provided 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 with a view to monitoring the injected signal. The device is however complex at the optical and connector level and does not allow reliable measurement of the applied dose.

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.

Patent EP3302687B1 describes a solution using a photodetector at the laser source, but it does not make it possible to decorrelate the backscattered light at the various optical interfaces and therefore to make an accurate measurement of the return signal.

The object of the invention is to provide 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 suitable for fulfilling such a role. In particular, it must fulfill one or more of the following objectives:

• Allow monitoring of the injected light dose;
• Enable probe integrity monitoring;
• Use bio-compatible materials;
• Minimize medical risks during its implantation and explantation;
• Ensure the aesthetic and physical comfort of the patient;
• Be easy to manufacture and easily reproducible;
• Enable effective treatment;

This object 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 of 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,
• A selective filter optical device located at the distal end of the optical fiber, comprising reflecting 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.

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

According to another feature, the multilayer deposit includes a final layer formed of a passivation layer.

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

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

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.

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

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 intended for the optical probe and to reflect a second part of the first optical signal or the second optical signal to a first photodiode of the optical module.

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

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

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

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.

According to one feature, the control and power supply unit is configured to analyze the return optical signal with a view to detecting faults at the level of the optical probe.

Brief description of figures

Other characteristics and advantages will appear in the detailed description which follows given with regard to the appended drawings in which:

• There schematically represents the illumination device according to the invention, according to a first embodiment;
• FIGS. 2A, 2B and 2C represent three variant embodiments of the optical probe used in the device of the invention;
• There shows in detail the end of the optical fiber of the optical probe of the device of the invention;
• There illustrates an embodiment of the multilayer deposition at the end of the optical fiber, with a passivation layer;
• FIGS. 4A to 4C show different variant embodiments of the optical module of the device of the invention;
• There represents an example of a reflectivity curve obtained for a multilayer deposit used in the invention;
• There shows reflectivity curves illustrating an operating principle of the device of the invention;

Detailed description of at least one embodiment

In the rest 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.

The invention relates more particularly to an implantable device for deep brain illumination. 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 – treatment such as neuroprotection, 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, Alzheimer's, Huntington's disease, etc.

In a non-limiting way, the device 1 can possibly integrate solutions proposing other stimulation modes (electrical, injection, etc.), in order to form so-called hybrid solutions. However, these solutions are not the subject of the present application.

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

With reference to the , 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 by an optical probe 3 advantageously integrating a single waveguide (optical fiber 30) responsible for guiding the optical signals generated by the optical module 2.

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

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

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

Advantageously, the control and supply unit forms part of an overall optical stimulation system, also including said device of the invention.

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

An electrical connector 21 can be arranged on said box 20 to come and connect the control and power supply unit IPG thereto.

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

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

The second optical signal emitted at a second wavelength (for example 730 nm), 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.

Advantageously, the optical module 2 is configured to be able to deliver at least three distinct optical signals, having three distinct wavelengths.

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

The optical module 2 comprises several light sources 22a, 22b, 22c housed in its casing 20, each capable of emitting a separate 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.

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.

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

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

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

The optical module 2 comprises a beam splitter device 25 housed in its casing 20, placed downstream of said lens 24 and optimized to transmit a first part of the optical signal emerging from the lens 24 to the optical probe 3 and to reflect a second part of the optical signal leaving the lens 24 to 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.

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 (power of the signal multiplied by time).

The separator 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 transmitted optical signal power and return optical signal power measurements, 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 may conclude that there is a fault at the level of the optical sensor 3.

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

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 of the separator device 25.

At the output, the optical module 2 may comprise a window 28, for example in sapphire intended to be traversed by the optical signal emitted by the selected light source.

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

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

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

The optical probe 3 comprises a single waveguide, for example an optical fiber 30, which is fixed, via its proximal end, to the output of the optical module 2 via 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.

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 providing the seal and advantageously replacing the porthole 28 of the optical module. This embodiment variant is visible on the .

As can be seen on the , in a non-limiting manner, the optical fiber 30 can conventionally comprise a core 300, around which are deposited a coating 301 (“coating”) and a mechanical protective sheath 302. The optical fiber 30 can of course have another architecture.

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

A centering ring 33, advantageously made of radio-opaque material, can be slipped around this stripped end.

According to a feature of the invention, at its distal end, the optical probe 3 is equipped with an optical device 34 ( And ) 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 suitable for transmitting this third wavelength.

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%.

In general, 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%.

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

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.

The optical device 34 can be made 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 on the , a final layer is a passivation layer 340.

The layers of the deposit are chosen in an appropriate way in index and in thickness to obtain the optical functions of transmission and reflection at the wavelengths, according to the principles described above.

In a non-limiting way, from the inside out, the deposit can comprise for example an alternation of layers made of Al ₂ O ₃ and of MgF ₂ ,

Any other assembly of layers could be envisaged, from the moment the intended functions are fulfilled.

There shows the reflectance curve obtained for the optical device produced 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 670 nm as well as at the third wavelength of 808 nm but that it is generally reflective at the second wavelength of 730 nm. It can thus ensure a transmission of the signals necessary for the processing and a reflection of the test signals intended for the monitoring of the probe.

On the , the signal is emitted at the end of the probe, via the distal end of the optical fiber 30.

Advantageously and optionally, the optical probe 3 can 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 can be an independent part made for example of silicone or epoxy resin loaded with TiO ₂ or photo inscribed in a silica waveguide.

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.

At the distal end of the diffuser 35, the probe may include a radiopaque element 37 to facilitate monitoring 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.

Advantageously, as shown in the , 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.

Over its entire length, the optical probe 3 comprises an outer sheath formed of a coating 39 (for example of optical silicone or equivalent). This coating comes to take the optical fiber and all the elements described above.

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.

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 request or automatically, at regular intervals or not. It is controlled by the IPG control and power supply unit. After emission, the optical test signal is first picked up, via the separator device 25, by the first photodiode 26. The signal is then reflected (ideally at least 50%) by the optical device 34, to provide an optical signal return test, which is returned by the separator device 25 to the second photodiode 27.

The control and power supply unit can then perform various processing operations, in particular analyzing whether the return optical test signal remains similar over time, to:

• Detect any faults at the level of the optical probe 3;
• Check the optical connection of optical probe 3 on optical module 2;

The processing optical signals transmitted at the other wavelengths should generate very weak return signals, compared to the return test optical 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.

It is possible to provide different arrangements of the optical module 2 and of its elements with respect to the optical probe 3. The inputs of the waveguide can be axial ( ) or radial ( And ) and the axial outlet.

The module housing can for example be oriented in the axis of the optical fiber 30 ( And ) or at right angles to it ( ). The various variant embodiments described are of course adaptable to each of these various configurations and arrangements.

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.

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 of less than 650 nm can be considered.

In the case of double (or more) wavelength illumination used for tissue treatment and where the power consumption of the device is not a constraint, it is possible to use one of the two wavelengths to the test signal by accepting to lose signal for one of the two sources (670nm for example in the diagram with a choice of reflectivity of 24%, 18%, 12%...) with transmission without losses at 810nm. There 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 retaining the possibility of easily distinguishing the return optical test signal, in relation to signals which would be reflected at other wavelengths (processing signal at 810nm).

The solution of the invention has many advantages, including:

• It makes it possible to precisely adjust the dose of illumination provided at the end of the probe;
• It makes it possible to go back to the type of defect in the event of failure, by determining if it is a simple degradation of the waveguide (which can be acceptable), measurable by a loss of propagation, if it is is a break in the optical fiber or an optical connection problem;
• Solution compatible with multiple illumination wavelengths;
• Device compatible with a standard IPG type power and control unit, requiring only software adaptation;
• Compact device (for example diameter 0.8 or 1.3mm at the level of the probe) suitable for deep stimulation surgery, using only one optical fiber for the propagation of the various signals, for processing and testing;
• Modular and removable solution with optional optical connector between the probe and the optical module;
• MRI compatibility;
• Long-term biocompatibility;
• Possibly adaptable, electrical and/or optical stimulation with choice of the stimulation wavelength;

Claims (13)

Device (1) implantable illumination 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 transmission power of the first optical signal and of 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:
• A selective filter optical device (34) located at the distal end of the optical fiber (30), comprising reflecting 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.

Device according to Claim 1, characterized in that the optical device (34) comprises a multilayer deposit. Device according to Claim 2, characterized in that the multilayer deposit comprises a last layer formed by a passivation layer (340). Device according to one of Claims 1 to 3, characterized in that the optical fiber (30) is stripped at its distal end. Device according to one of Claims 1 to 4, characterized in that the optical module (2) comprises several light sources (22a, 22b, 22c), each dedicated to the emission of a distinct optical signal. Device according to Claim 5, characterized in that the optical module (2) comprises a waveguide (23), comprising several inputs, to each of which is connected a separate light source and a single output. Device according to Claim 6, characterized in that the optical module (2) comprises a lens (24) arranged downstream of the output of the waveguide. Device according to Claim 7, characterized in that the optical module comprises a beam splitter device (25), arranged downstream of the said lens (24) to transmit a first part of the first optical signal or of the second optical signal emitted intended for 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). Device according to Claim 8, characterized in that the beam splitter device is arranged to reflect the said return optical signal towards a second photodiode (27) of the optical module (2). Device according to one of Claims 1 to 9, characterized in that the optical probe (3) comprises a diffuser (35) positioned at the distal end of the optical fiber (30). Device according to Claim 10, characterized in that the optical probe (3) comprises a mirror (38) arranged axially, partially around the diffuser (35). 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 the one of claims 1 to 11. System according to Claim 12, characterized in that the control and power supply unit is configured to analyze the return optical signal in order to detect faults at the level of the optical probe.