FR3130545A1 - Device for measuring the electrical and thermal activity of a living being - Google Patents

Abstract

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

Description

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

Technical field of the invention

The present invention relates to a device for measuring the electrical and thermal activity of a living being.

State of the art

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 foci(s).

By increasing the precision of the localization of the epileptogenic focus, the chances of success of the surgery implemented thereafter are increased.

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

It is in particular known to implant a probe in the living being, in order to measure the electrical activity of the tissues and thus help in the detection of the epileptogenic foci or foci.

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

The identification of the epileptogenic zone in SEEG is based on the visual analysis or with software of the intracerebral tracings. However, there are no robust electrophysiological criteria allowing us to affirm that the zone of onset of seizures has been delimited without ambiguity, so that the analysis of failures, but also of successes, comes up against the absence of objective measurement. tissue epileptogenicity.

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

The object 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.

This object is achieved by a measuring device comprising a probe which can be implanted 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 treatment to which the measurement means are connected, said measurement means comprising a plurality of measurement electrodes positioned along the rod, each electrode or group of several electrodes being configured to supply 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 supply second measurement data to said processing unit, the processing unit being configured to correlate the first measurement data with the second measurement data.

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.

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

According to one feature, each temperature measurement element is produced using a technology chosen from:

• A Bragg grating with temperature sensitivity,
• thermistor,
• Thermocouple,
• Micro-bolometer.

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

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

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

According to another particular embodiment, each temperature measuring element is formed by a sensor of the PT100 or PT1000 type.

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.

According to another particular embodiment, the branches are secured to a rod inserted in the axis of the probe, movable in translation under the action of a spring.

It is known that variations in temperature 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, increasing accuracy.

Thermal mapping is going to be spatially more accurate and could guide precise resection, increasing the success rate of surgery and reducing postoperative complications. Alert systems and loop systems based on crisis detection could also be improved by combining bimodal measures.

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

In particular, the probe should advantageously meet the following criteria:

• Manufacturing mode allowing the integration of multiple temperature measurement points on the path of the probe;
• Suitable for standard SEEG surgery;
• Long-term biocompatibility;
• MRI compatible;
• Technology compatible with the production of SEEG probes;

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 device of the invention;
• FIGS. 2A and 2B illustrate several variant embodiments of the probe;
• FIGS. 3A and 3B represent an alternative embodiment of the probe used in the device of the invention;
• FIGS. 4A and 4B show two other variant embodiments of the probe used in the device of the invention;

Detailed description of at least one embodiment

With reference to the , the invention relates to a measurement device 1 comprising mainly a measurement probe 10 and a processing unit UC responsible for processing the measurements made by the probe 10. The probe is intended to be implanted, at least in part, at the interior of a living being 2.

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

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 CPU processing unit. Wireless links 12 can also be provided to ensure exchanges of data between the probe 10 and the processing unit UC. The electrical connection can be made via a transcutaneous connector.

The section of the rod of the body 100 of the probe advantageously has a constant transverse section, advantageously circular, for example of a standard diameter used in StereoElectroEncephalography (SEEG) of 0.8 mm.

The probe 10 will for example be provided for an implantation lasting less than 28 days.

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

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 place with low electrical activity.

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 level of the processing unit. Multiple electrical measurement points are thus available along the probe.

Each electrode 101 can take 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 can also be a winding made of a conductive material. A sealing/moulding material, such as silicone or polyurethane, may prove necessary to manufacture a probe 10 of constant section along its length.

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

In a non-limiting manner, the probe 10 can for example comprise as many electrodes 101 as there are temperature measuring elements 102 .

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

Thanks to these temperature measurement elements 102, the device 1 is able to provide thermal mapping of the brain, synchronized with a conventional mapping obtained by SEEG.

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 heat source and have the lowest thermal inertia.

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.

In known manner, a Bragg grating uses one or more optical fibers functioning as a mirror which only reflects at a very precise wavelength. When the optical fiber is mechanically stressed or when its temperature changes, the reflected wavelength varies proportionally. It would therefore be possible to insert one or more optical fibers into the body of the probe to make in-vivo temperature measurements.

FIGS. 2A and 2B show distinct embodiments of the probe, using temperature measurement elements 102, each made according to a thermistor, also called a resistance thermometer (called RTD = “Resistance temperature detector”). According to this technology, we know in particular the sensors called PT100 and PT1000. Such a sensor can be in the form of an insulated and wound platinum wire or a thin layer deposit.

In a sensor of the PT100 or PT1000 type 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. It is possible in particular to produce two or three thicknesses of winding, in particular if it is desired to obtain a compact sensor in the direction of the length.
• The resistance is 100 Ohms (for the PT100) or 1000 Ohms (for the PT1000);

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

The figures show two embodiments, in which the measuring elements 102 are inserted between the electrodes. On the , each measuring element 102 is in the form of an annular ring, for example made by winding platinum wire, around the probe.

On the , a segmented ring, for example made of zirconia or PEEK (for "PolyEtherEtherKetone", polyetheretherketone thermoplastic polymer) supports a winding of platinum wire. Each ring is inserted between two electrodes 101 for electrical measurement.

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

For a platinum track 200 nm thick with a track width of 50 µm, the target length for a PT100 type sensor is around 1 cm. For the same thickness with a track 10 µm wide, the target length for a PT1000 type sensor is around 2 cm. Platinum is MRI compatible. A 20 to 50 nm thick titanium bonding layer also compatible with MRI can also be used.

According to a particular embodiment illustrated by FIGS. 3A and 3B, the probe 10 can have branches 200 that can be deployed like an umbrella along its stem. The probe 10 thus comprises several pairs of branches juxtaposed over at least part of its length. Each branch 200 can pass from a first retracted position inside the body of the probe ( ) at a second position projecting radially with respect to the side wall of the body of the probe ( ). This principle is described in particular in patent EP1932561B1 . In each pair, the two branches 200 deploy radially symmetrically with respect to the axis of the probe 10. The position of the branches 200 can be changed by integrating a rod 201 into the body 100 of the probe 10, operable in translation by a spring 202. The branches 200 are integral with said rod and form a one-piece assembly operable in translation. Opposite each branch, the body of the probe has a sufficient opening arranged to be traversed by the branch.

In the context of the invention, each branch 200 can carry an electrical measurement electrode 101 and a temperature measurement element 102, as on the . But it is also possible to alternate from one arm to the other along the probe 10, the presence of an electrical measurement electrode 101 and the presence of a temperature measurement element 102, as on the .

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

FIGS. 4A and 4B show two other examples of distribution of electrodes 101 and temperature measuring elements 102 on branches 200. On the , 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 bears on each of its branches, at least one electrode 101 and the adjacent second pair bears on each of its branches, at least one temperature measuring element 102 . This pattern is for example reproduced along the probe 10.

On the , the alternation is carried out in a different way. 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 probe 10.

These achievements 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 .

The placement of its probe 10 is done by insertion into the cranial box through the holes previously made in line with the potential targets. The insertion is made on a trajectory passing through the epileptogenic foci or foci so that both electrophysiological and thermal recordings are available in the distal part of the probe 10. The proximal part outside the cranial box is compatible with electrical/optical connectors for connection to electrophysiological acquisition and electrical resistance measurement systems. The temperature is deduced from the one-to-one relationship between the electrical resistance and the temperature coming from previous calibrations. These systems can be wired or wireless (telemetry).

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

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

The invention thus has many advantages. The main advantage is the distribution of the temperature sensors on or around the trajectory investigated by the measurement probe or nearby in a so-called umbrella configuration in order to produce a temperature map, which can be an additional predictive biomarker of the crisis. 'epilepsy.

The solution proposed makes it possible to improve the diagnosis of epileptogenic foci and to support a decision of surgical resection or, in the hypothesis of an implanted system of localized cooling or electrical stimulation, 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 (10)

Measuring device (1) comprising a probe (10) implantable in a living being, said probe (10) comprising a body formed of an elongated rod between a proximal end and a distal end, said probe (10) comprising means for measurement, and a processing unit (UC) to which the measurement means are connected, the said measurement means comprising a plurality of measurement electrodes (101) positioned along the rod, each electrode (101) or group of several electrodes being configured to supply first measurement data to said processing unit (UC), characterized in that the measurement means also comprise several temperature measurement elements (102) juxtaposed along the rod, each temperature being configured to supply second measurement data to said processing unit (UC), and in that the processing unit (UC) is configured to correlate the first measurement data with the second measurement data. 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). Device according to Claim 1, characterized in that the temperature measuring elements (102) are positioned on the electrodes (101). Device according to one of Claims 1 to 3, characterized in that each temperature measuring element (102) is made using a technology chosen from:

• A Bragg grating with temperature sensitivity,
• thermistor,
• Thermocouple,
• Micro-bolometer.

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. 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. Device according to claim 1, characterized in that each temperature measuring element (102) is produced by a thin layer deposition. Device according to one of Claims 1 to 7, characterized in that each temperature measuring element (102) is formed by a sensor of the PT100 or PT1000 type. Device according to Claim 1, characterized in that the probe (10) comprises several deployable branches (200) distributed over at least part of its length, and in that each branch (200) carries an electrode and/or a temperature measurement. Device according to Claim 9, characterized in that the branches are integral with a rod (201) inserted in the axis of the probe, which can be moved in translation under the action of a spring (202).