Device for measuring the electrical and thermal activity of a living being

Abstract

The invention relates to a measuring device (1) comprising a probe (10) implantable in a living being, said probe (10) comprising measuring means, and a processing unit (PU) to which the measuring means are connected, said measuring means comprising a plurality of measuring electrodes (101), each electrode (101) or group of several electrodes being configured to provide first measurement data to said processing unit (PU), the measuring means also comprising several juxtaposed temperature measuring elements (102), each temperature measuring element being configured to provide second measurement data to said processing unit (PU), the processing unit (PU) being configured to correlate the first measurement data with the second measurement data. Figure to be published with the abstract: Figure 1

Description

Title of the invention: Device for measuring the electrical and thermal activity of a living being Technical field of the invention

[0001] The present invention relates to a device for measuring the electrical and thermal activity of a living being. State of the art

[0002] The precise localization of an epileptogenic focus in an epileptic patient represents a challenge and often employs a multitude of technical means. Currently, the only definitive curative treatment in the case of focal drug-resistant epilepsy is surgical resection of the epileptogenic focus(es).

[0003] By increasing the precision of the localization of the epileptogenic focus, the chances of success of the surgery subsequently implemented are increased.

[0004] The use of intracranial recordings is essential in order to provide the neurosurgeon with as precise a view as possible of the brain region to be resected. These recordings can use electrodes placed on the surface of the cortex, electrodes introduced into the brain itself (deep electrodes), or a combination of these two approaches.

[0005] It is known in particular to implant a probe in the living being, to measure the electrical activity of the tissues and thus help in the detection of the epileptogenic focus(es).

[0006] These deep electrodes are part of a technique known as StereoElectroEncephalography (SEEG).

[0007] The identification of the epileptogenic zone in SEEG is based on visual or software analysis of intracerebral tracings. However, there are no robust electrophysiological criteria to confirm that the seizure onset zone has been unambiguously delineated, so that the analysis of failures, but also of successes, is hampered by the absence of an objective measurement of tissue epileptogenicity.

[0008] For this reason, it is essential to integrate complementary sensors to enrich the clinical investigation of SEEG probes and increase the spatial and temporal precision of the mapping while reducing post-excision complications.

[0009] The aim of the invention is to propose a device offering the possibility of providing measurements complementary to those obtained by SEEG, for example to better locate one or more epileptogenic foci. Statement of the invention

[0010] This aim is achieved by a measuring device comprising a probe implantable in a living being, said probe comprising a body formed of an elongated rod between a proximal end and a distal end, said probe comprising measuring means, and a processing unit to which the measuring means are connected, said measuring means comprising a plurality of measuring electrodes positioned along the rod, each electrode or group of several electrodes being configured to provide first measurement data to said processing unit, the measuring means also comprising several temperature measuring elements juxtaposed along the rod, each temperature measuring element being configured to provide second measurement data to said processing unit, the processing unit being configured to correlate the first measurement data with the second measurement data.

[0011] According to a particular embodiment, the electrodes and the temperature measuring elements are arranged alternately over at least part of the length of the probe.

[0012] According to another particular embodiment, the temperature measuring elements are positioned on the electrodes or under the electrodes.

[0013] According to a particular feature, each temperature measuring element is produced using a technology chosen from: - A Bragg grating with temperature sensitivity, - Thermistor, - Thermocouple, - Micro-bolometer.

[0014] According to a particular embodiment, each temperature measuring element is produced in the form of a platinum wire wound around the body of the probe.

[0015] According to another particular embodiment, each temperature measuring element is produced in the form of a platinum wire arranged on an annular or segmented ring fixed to the body of the probe.

[0016] According to another particular embodiment, each temperature measuring element is produced by a thin-layer deposition.

[0017] According to another particular embodiment, each temperature measuring element is formed from a PT 100 or PT 1000 type sensor.

[0018] According to another particular embodiment, the probe comprises several deployable branches distributed over at least part of its length, and in that each branch carries an electrode and / or a temperature measuring element.

[0019] According to another particular embodiment, the branches are integral with a rod inserted into the axis of the probe, movable in translation under the action of a spring.

[0020] It is known that temperature variations accompany epileptic seizures. Temperature and electrophysiological signals have different dynamics and could therefore complement each other. Thermal effects are very focal / local, and thermal measurements allow thermographic reconstruction of brain space, thus increasing accuracy.

[0021] Thermal mapping will be spatially more precise and could guide precise resection, increasing the success rate of surgery and reducing postoperative complications. Alert systems and loop systems based on seizure detection could also be improved by combining bimodal measurements.

[0022] The chosen approach is therefore to create a bimodal electrical and thermal recording probe. For example, we propose a deep probe with multiple contacts (4, 6, 8, 10 or 12 contacts) which will integrate both electrical and thermal modalities for pre-surgical diagnosis of epilepsy.

[0023] In particular, the probe must advantageously meet the following criteria: - Manufacturing method allowing the integration of multiple temperature measurement points on the probe trajectory; - Suitable for standard SEEG surgery; - Long-term biocompatibility; - MRI compatible; - Technology compatible with the production of SEEG probes; Brief description of the figures

[0024] 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 device of the invention; - Figures 2A and 2B illustrate several variants of the probe; - Figures 3A and 3B represent an alternative embodiment of the probe used in the device of the invention; - Figures 4A and 4B show two other variant embodiments of the probe used in the device of the invention;

[0025] Detailed description of at least one embodiment

[0026] With reference to [Fig. 1], the invention relates to a measuring device 1 mainly comprising a measuring probe 10 and a processing unit UC responsible for processing the measurements carried out by the probe 10. The probe is intended to be implanted, at least in part, inside a living being 2.

[0027] The processing unit UC advantageously comprises a microprocessor and storage means.

[0028] The measuring probe comprises a body 100 made of biocompatible material in the form of an elongated rod, along an axis (X), between a proximal end and a rounded distal end. At its proximal end, the probe 10 is connected to the processing unit UC, for example via a multi-strand cable 11 (possibly including optical waveguides), to ensure the exchange of electrical signals between the probe 10 and the processing unit UC. Wireless links 12 may also be provided to ensure data exchanges between the probe 10 and the processing unit UC. The electrical connection may be made via a transcutaneous connector.

[0029] The section of the rod of the body 100 of the probe advantageously has a constant cross-section, advantageously circular, for example with a standard diameter used in StereoElectroEncephalography (SEEG) of 0.8 mm.

[0030] The probe 10 will for example be designed for implantation lasting less than 28 days.

[0031] The probe 10 carries a plurality of electrodes 101 intended to measure electrical activity inside the living being 2. The electrodes 101 advantageously operate according to the technique known as StereoElectroEncephalography (SEEG).

[0032] In the case of a SEEG type measurement, the electrodes 101 are often associated in pairs, to measure potential differences. It is possible to set up a so-called "monopolar" assembly in which an active electrode and a reference electrode are used or a so-called "bipolar" assembly in which two active electrodes are used. In a monopolar assembly, the reference electrode is positioned in a location with low electrical activity.

[0033] According to a feature of the probe 10, the electrodes 101 are arranged along the probe 10 and are staggered along the latter, advantageously in a regular manner. The number of electrodes 101 used may in particular depend on the number of measurement channels available at the processing unit. This provides multiple electrical measurement points along the probe.

[0034] Each electrode 101 may be in the form of an annular or segmented ring made of conductive material, threaded around the body 100 of the probe 10 or integrated into said body. It may also be a winding made of a conductive material. A sealing / molding material, such as silicone or polyurethane, may be necessary to manufacture a probe 10 of constant section along its length.

[0035] According to a particular aspect of the invention, the probe 10 also comprises several temperature measuring elements 102. These temperature measuring elements 102 are each responsible for carrying out a separate temperature measurement.

[0036] In a non-limiting manner, the probe 10 may for example comprise as many electrodes 101 as temperature measuring elements 102.

[0037] The temperature measuring elements 102 can be arranged directly on the electrodes 101, between the electrodes 101 or under the electrodes 101.

[0038] Thanks to these temperature measuring elements 102, the device 1 is capable of providing a thermal map of the brain, synchronized with a conventional map obtained by SEEG.

[0039] The temperature measuring elements 102 have the function of measuring a localized and rapid variation in temperature. Each temperature measuring element 102 must be as close as possible to the thermal source and have the lowest thermal inertia.

[0040] In a non-limiting manner, each temperature measuring element 102 can be chosen, for example, from: - Bragg grating with temperature sensitivity, - Thermistor, - Thermocouple, - Micro-bolometer.

[0041] As is known, a Bragg grating uses one or more optical fibers functioning as a mirror that reflects only at a very precise wavelength. When the optical fiber is mechanically stressed or when its temperature changes, the reflected wavelength varies proportionally. One or more optical fibers could therefore be inserted into the body of the probe to make in-vivo temperature measurements.

[0042] Figures 2A and 2B show distinct embodiments of the probe, using temperature measuring elements 102, each made according to a thermistor, also called resistance thermometer (called RTD = "Resistance temperature detector"). According to this technology, sensors called PT100 and PT 1000 are known in particular. Such a sensor can be in the form of an insulated and wound platinum wire or a thin-film deposit.

[0043] In a PT100 or PT1000 type sensor with insulated and wound wire, we have for example the following parameters: - The diameter of the insulated platinum wire is, for example, 15 μm and the insulation has a thickness of 2 μm. In particular, two or three winding thicknesses can be produced, especially if one wishes to obtain a compact sensor in the length direction. - The resistance is 100 Ohms (for the PT 100) or 1000 Ohms (for the PT 1000);

[0044] Different integrations can be provided. It is possible to interpose a temperature measuring element 102 between two electrodes 101. It is also possible to directly integrate the temperature measuring element 102 into the electrode.

[0045] The figures show two exemplary embodiments, in which the measuring elements 102 are interposed between the electrodes. In [Fig.2A], each measuring element 102 is in the form of an annular ring, for example made by winding platinum wire around the probe.

[0046] In [Fig.2B], a segmented ring, for example made of zirconia or PEEK (for "Poly-EtherEtherKetone", thermoplastic polymer polyetheretherketone) supports a winding of platinum wire. Each ring is interposed between two electrical measuring electrodes 101.

[0047] It is also possible to produce the temperature sensor by thin-film deposition. Platinum tracks between two layers of insulation, for example polyimide or parylene type, are produced. According to this principle, the variation of the electrical resistance of platinum as a function of temperature is also used.

[0048] For a platinum track with a thickness of 200 nm and a track width of 50 pm, the length to be targeted for a PT 100 type sensor is of the order of 1 cm. For the same thickness with a track 10 pm wide, the length to be targeted for a PT 1000 type sensor is of the order of 2 cm. Platinum is MRI compatible. A titanium bonding layer with a thickness of 20 to 50 nm, also MRI compatible, can also be used.

[0049] According to a particular embodiment illustrated by figures 3A and 3B, the probe 10 may have branches 200 that can be deployed in an umbrella shape along its stem. The probe 10 thus comprises several pairs of branches juxtaposed over at least part of its length. Each branch 200 can move from a first position retracted inside the body of the probe ([Fig.3A]) to a second position projecting radially relative to the side wall of the body of the probe ([Fig.3B]). This principle is described in particular in patent EP1932561B1. In each pair, the two branches 200 are deployed radially in a symmetrical manner relative to the axis of the probe 10. The change of position of the branches 200 can be achieved by integrating a rod 201 into the body 100 of the probe 10, actuable in translation by a spring 202. The branches 200 are integral with said rod and form a single-piece assembly actuable in translation.Opposite each branch, the body of the probe has a sufficient opening arranged to be crossed by the branch.

[0050] In the context of the invention, each branch 200 can carry an electrical measuring electrode 101 and a temperature measuring element 102, as in [Fig. 3A]. But it is also possible to alternate from one arm to the other along the probe 10, the presence of an electrical measuring electrode 101 and the presence of a temperature measuring element 102, as in [Fig. 3B].

[0051] The production principles described above for the temperature measuring elements 102 remain applicable to the production of the probe 10 with deployable arms.

[0052] Figures 4A and 4B show two other examples of distribution of the electrodes 101 and the temperature measuring elements 102 on the branches 200. In [Fig.4A], the electrodes 101 and the temperature measuring elements 102 are arranged alternately, from one pair of branches 200 to the other. The first pair thus carries on each of its branches, at least one electrode 101 and the second adjacent pair carries on each of its branches, at least one temperature measuring element 102. This pattern is for example reproduced along the probe 10.

[0053] In [Fig.4B], the alternation is carried out in a different manner. The first pair comprises only at least one electrode 101 on its first branch and only at least one temperature measuring element 102 on its second branch. And the adjacent pair carries only at least one temperature measuring element 102 on its first branch and only at least one electrode 101 on its second branch. This pattern can be reproduced over the entire length of the probe 10.

[0054] These embodiments are to be taken in a non-limiting manner and it should be understood that any other arrangement could be imagined. Each branch can in particular carry several electrodes 101 and / or several temperature measuring elements 102.

[0055] The probe 10 is placed by insertion into the cranium through the holes previously made in line with the potential targets. The insertion is made on a trajectory passing through the epileptogenic focus(es) so that both electrophysiological and thermal recordings are available in the distal part of the probe 10. The proximal part outside the cranium is compatible with electrical / optical connectors for connection to electrophysiological acquisition and electrical resistance measurement systems. The temperature is deduced from the bijective relationship between the electrical resistance and the temperature from prior calibrations. These systems can be wired or wireless (telemetry).

[0056] The use of such wired systems is limited in time due to the risks of tearing and infection in clinical practice. Acquisitions are usually made over one to two weeks. The devices are qualified in terms of biocompatibility for a period of use of less than or equal to 28 days.

[0057] In the case of a mixed probe 10 with "deployable" branches, the branches 200 are in the probe during descent and when the stylet is withdrawn, the spring 202, then in compression, relaxes and pushes the branches into a volume of a few millimeters to a few centimeters. For the withdrawal of the probes, the branches are retracted by putting the spring back into compression by means of the stylet.

[0058] The invention thus has numerous advantages. The main advantage is the distribution of the temperature sensors on or around the trajectory investigated by the measuring probe or nearby in a so-called umbrella configuration in order to achieve a temperature map, which may be a complementary biomarker predictive of epileptic seizures.

[0059] The proposed solution makes it possible to improve the diagnosis of epileptogenic foci and to support a decision for surgical resection or, in the case of an implanted localized cooling or electrical stimulation system, to trigger a cooling sequence or an electrical charge, in order to best block the epileptic seizure based on electrophysiological and / or thermal biomarkers.

Claims

Claims

1. Measuring device (1) comprising a probe (10) implantable in a living being, said probe (10) comprising a body formed by an elongated rod between a proximal end and a distal end, said probe (10) comprising measuring means, and a processing unit (UC) to which the measuring means are connected, said measuring means comprising a plurality of measuring electrodes (101) positioned along the rod, each electrode (101) or group of several electrodes being configured to provide first measurement data to said processing unit (UC), characterized in that: - The measuring means also comprise several temperature measuring elements (102), each temperature measuring element being configured to provide second measurement data to said processing unit (UC), - The probe comprising several deployable branches (200) distributed over at least part of its length,each branch (200) carrying an electrode and / or a temperature measuring element, - The processing unit (UC) is configured to correlate the first measurement data with the second measurement data.,

2. Device according to claim 1, characterized in that the electrodes (101) and the temperature measuring elements (102) are arranged alternately over at least part of the length of the probe (10).

3. Device according to claim 1, characterized in that the temperature measuring elements (102) are positioned on the electrodes (101).

4. Device according to one of claims 1 to 3, characterized in that each temperature measuring element (102) is produced using a technology chosen from: - A Bragg grating having temperature sensitivity, - Thermistor, - Thermocouple, - Micro-bolometer.

5. Device according to claim 1, characterized in that each temperature measuring element (102) is produced in the form of a platinum wire wound around the body (100) of the probe.

6. Device according to claim 1, characterized in that each temperature measuring element (102) is produced in the form of a platinum wire arranged on an annular or segmented ring fixed to the body (100) of the probe.

7. Device according to claim 1, characterized in that each temperature measuring element (102) is produced by a thin-layer deposition.

8. Device according to one of claims 1 to 7, characterized in that each temperature measuring element (102) is formed from a PT 100 or PT 1000 type sensor.

9. Device according to claim 1, characterized in that the branches are integral with a rod (201) inserted into the axis of the probe, movable in translation under the action of a spring (202).

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