Magnetic shielding for medical magnetic measurement

Abstract

A biomagnetic measuring device (1) comprising: - a support (2) extending along a longitudinal direction (X) and intended to receive a patient's body (10), - a magnetically shielded enclosure (3) extending along the longitudinal direction (X) and comprising an open end (31) opposite the support (2), - magnetic sensors (7), - a sensor holding system (4), attached to the support (2) and configured to hold the magnetic sensors (7) opposite an organ of the patient's body (10) in a position for acquiring biomagnetic signals, - a controller (5) connected to the sensor holding system (4) by a cable (6), the cable (6) being configured to transmit an electrical signal and / or an optical signal to the magnetic sensors (7),The biomagnetic measuring device (1) is characterized in that the support (2) is fixed and the magnetically shielded enclosure (3) is mounted to move in translation relative to the support (2) along the longitudinal direction (X), so as to be able to surround a portion of the support (2) from the open end (31), and in that a portion of the cable (6) extending along the longitudinal direction (X) is fixed to the support (2). Figure for the abstract: Fig. 1,

Description

Title of the invention: Magnetic shielding for medical magnetic measurement technical field

[0001] This disclosure relates to the general field of medical imaging devices based on the acquisition of magnetic signals of physiological processes of organs. STATE OF THE ART

[0002] Various medical imaging devices exist for obtaining a representation of physiological processes in organs such as the brain or the heart. Some devices use electrodes placed on the body's surface to characterize the electrical currents flowing within the organ due to the resulting differences in electrical voltage across the body's surface. However, the propagation of electrical signals within the body is significantly disrupted at the interface between tissues with different resistivities or conductivities, for example, between bones and soft tissues, which makes the localization of the currents that created the measured voltages very imprecise.

[0003] The use of magnetic signals provides more precise spatial information because, unlike electrical signals, magnetic signals are not subject to the aforementioned disturbances. However, the measured signals are of very low amplitude, on the order of femto-Tesla to pico-Tesla. It is therefore necessary to develop highly sensitive magnetic field sensors and to record the signals in a magnetically shielded enclosure so that the recording is not disturbed by spurious signals.

[0004] Most current medical imaging devices include a magnetically shielded enclosure with a volume of 15 to 50 m3. The walls of the enclosure comprise several layers of materials with high magnetic permeability.

[0005] A first type of sensor enabling the necessary sensitivities to be achieved is a superconducting magnetometer (known as a SQUID, an acronym for "superconducting quantum interference device"). These sensors require a massive shielded enclosure. Indeed, the shielded enclosure must contain the patient and sensors arranged in a large container filled with a cryogenic fluid, as well as a significant thickness of insulation to thermally separate the patient from the container.

[0006] A second type of sensor comprises optically pumped atomic gases (or OPMs for "Optically Pumped Magnetometers"). This type of sensor This allows for measurements with similar sensitivity to the first type of sensor, without the use of cryogenic fluid. It is then possible to use a smaller shielded enclosure, on the order of 1 to 5 m³, for example, a magnetically shielded enclosure such as the one proposed by US 2019 / 0387647. However, these enclosures are expensive, impractical for an operator to use, and uncomfortable for the patient.

[0007] Alternatively, a cylindrical shielded enclosure can be used, into which the patient is introduced in a supine position, as proposed in US 2023 / 0204688 A1, or in A. Borna et al., “A 20-channel magnetoencephalography System based on optically pumped magnetometers” Phys. Med. Biol., vol. 62, no. 23, pp. 8909-8923, Nov. 2017. The associated measuring devices are more flexible, less expensive, and placed directly on the surface of the patient's body.

[0008] In such devices, the patient is generally lying on a mobile support. The sensors are usually positioned on the patient by an operator, near the organ to be observed, before the mobile support is inserted into the cylindrical shielded enclosure. This causes discomfort for the patient. Moreover, this operating method is impractical and presents an increased risk of sensor failure. Indeed, moving the mobile support and the patient equipped with the sensors can damage the cables connecting the sensor to the processing unit and the associated interface. To improve patient comfort, it is advantageous to reduce the weight of the sensors placed on the patient's body. Thus, it is preferable to use lightweight cables developed specifically for medical applications, which are thinner and therefore more fragile. This further increases the risk of failure.Furthermore, the positioning of the sensors may change during movement, resulting in a degradation of the quality of the signals obtained in the measurement. Description of the invention

[0009] One aim of the present disclosure is to propose a compact and comfortable device for the acquisition of biomagnetic signals from a patient's organ allowing simple and precise placement of biomagnetic sensors opposite the organ, limiting the risks of failure of the biomagnetic sensors.

[0010] This goal is achieved by the biomagnetic measuring device comprising:

[0011] - a support extending along a longitudinal direction and intended to receive a a patient's body,

[0012] - a magnetically shielded enclosure extending along the longitudinal direction and including an open end opposite the support,

[0013] - magnetic sensors,

[0014] - a sensor retention system, attached to the support and configured for to maintain the magnetic sensors opposite an organ of the patient's body in a position for acquiring biomagnetic signals,

[0015] - a controller connected to the sensor holding system by a cable, the cable being configured to transmit an electrical and / or optical signal to magnetic sensors,

[0016] the biomagnetic measuring device being characterized in that the support is immobile and the magnetically shielded enclosure is mounted movable in translation relative to the support in the longitudinal direction, so as to be able to surround a part of the support from the open end, and in that a portion of the cable extending in the longitudinal direction is fixed to the support.

[0017] The proposed device allows for the magnetic isolation of the patient organ at which biomagnetic signals are to be acquired. This is achieved by sliding the magnetically shielded enclosure towards the patient's organ after the magnetic sensors have been installed on the sensor support system. The support on which the patient is positioned remains stationary during placement and acquisition, thus increasing patient comfort. Furthermore, once the sensor support system is in the acquisition position, it remains fixed. This limits the risk of applying tension or torsion to the cables connecting the sensors to the device's control system or human-machine interface, which could lead to cable damage.Indeed, it is advantageous to use lighter, and therefore thinner and more fragile, cables to connect the sensor positioned opposite the patient's organ to the controller, particularly to transmit biomagnetic signals or ensure the sensors function. Furthermore, the cable can include an optical fiber, as is commonly used in OPM-type magnetometers, which is less resistant to twisting. This also prevents the sensors from shifting relative to the patient to a less suitable position, thus avoiding degradation of the biomagnetic signals.

[0018] The biomagnetic measuring device may have the following advantageous and non-limiting characteristics, taken alone or in any technically feasible combination:

[0019] - the cable includes an optical fiber;

[0020] - the controller is further configured to: - calculate a quality indicator for biomagnetic signals delivered by magnetic sensors; - compare the quality indicator to a threshold; and - if the quality indicator is above the threshold, order an additional translation of the magnetically shielded enclosure relative to the support in the longitudinal direction;

[0021] - the sensor retention system includes a positioning mechanism in the position for acquiring biomagnetic signals;

[0022] - the positioning mechanism includes a joint allowing a translational movement of the sensor support system relative to the support in the longitudinal direction, with a travel between 0.5 cm and 50 cm, preferably less than 25 cm;

[0023] - the positioning mechanism includes a joint allowing a rotational movement of the sensor holding system around the longitudinal direction, with a deflection between 1° and 45°, preferably less than 20°;

[0024] - the positioning mechanism includes a clamping device configured for exert pressure towards the patient's body organ, so as to keep the sensors in contact with the patient's body organ;

[0025] - the magnetic sensor retention system is a retention system optically pumped magnetometers;

[0026] - the patient's organ is the patient's brain;

[0027] - the device further includes a control device configured for command a translation of the magnetically shielded enclosure relative to the support in the longitudinal direction, so that the magnetically shielded enclosure moves from an installation position in which the magnetically shielded enclosure does not surround the sensor holding system to a magnetic isolation position in which the shielded enclosure surrounds the sensor holding system;

[0028] - the magnetically shielded enclosure is a telescopic enclosure comprising a plurality of concentric enclosures mounted mobile in translation relative to the support along the longitudinal direction;

[0029] - the support comprises an external enclosure extending along the longitudinal direction concentrically to the magnetically shielded enclosure, configured to receive the magnetically shielded enclosure when the sensor holding system is not in the biomagnetic signal acquisition position;

[0030] - the device further comprises a projection system configured to project an image inside the magnetically shielded enclosure.

[0031] According to another aspect, a method for acquiring biomagnetic signals using the biomagnetic measuring device described above is proposed, comprising the following steps:

[0032] - positioning of the patient's body on the support, the shielded enclosure magnetically being in an installation position in which it does not surround the sensor holding system;

[0033] - positioning of the sensor holding system in the acquisition position of biomagnetic signals opposite the organ of the patient's body;

[0034] - translation of the magnetically shielded enclosure along the longitudinal direction from the installation position to a magnetic isolation position, in which the magnetically shielded enclosure surrounds the sensor holding system;

[0035] - acquisition of biomagnetic signals by magnetic sensors. DESCRIPTION OF THE FIGURES

[0036] Other features, objectives and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0037] [Fig.1] Fig.1 schematically illustrates a biomagnetic measuring device according to a first embodiment, in an installation position.

[0038] [Fig.2] Fig.2 schematically illustrates the measuring device biomagnetic according to the first embodiment, in a position of magnetic isolation.

[0039] [Fig.3] Fig.3 schematically illustrates a measuring device biomagnetic according to a second embodiment, before the patient is installed.

[0040] [Fig.4] [Fig.4] schematically illustrates a sensor retention system for a magnetoencephalography.

[0041] [Fig. 5] Fig. 5 is a flowchart of the steps in a process for acquiring biomagnetic signals, according to another aspect of the invention.

[0042] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

[0043] With reference to [Fig.1], the biomagnetic measuring device 1 according to the present invention comprises a fixed support 2, a magnetically shielded enclosure 3, and magnetic sensors held by a sensor holding system 4.

[0044] Support

[0045] The support 2 extends along a longitudinal direction along the X-axis and is intended to receive the body of a patient 10. In the embodiment shown in Figures 1 and 3, the patient 10 is intended to lie on the support 2, or in other words, the support 2 is intended to receive the body of a patient 10 in a supine position. The support 2 generally comprises a surface 21 extending along the substantially horizontal X-axis. The surface 21 of the support 2 is preferably ergonomic, so that the patient lies comfortably. For example, the surface 21 is covered by a thin mattress. The surface 21 on which the patient lies can be flat or curved, as illustrated in [Fig.3].

[0046] During the use of the device, in particular during the installation of the patient or the acquisition of biomagnetic signals, the support 2 is fixed, i.e. immobile.

[0047] Magnetically shielded enclosure

[0048] The magnetically shielded enclosure 3 extends along the longitudinal direction X and includes an open end 31 facing the support 2, i.e., oriented towards the support 2, for example in a plane orthogonal to the X axis. The magnetically shielded enclosure 3 may have a cylindrical shape, for example, be a cylinder open at its base ([Fig. 3]). Alternatively, the shielded enclosure may have the shape of an open parallelepiped or, more generally, a polygonal prism open at one of its bases, or having an opening at both ends ([Fig. 1]).

[0049] The magnetically shielded enclosure 3 is mounted to move in translation relative to the support 2 along the longitudinal direction X. This allows the magnetically shielded enclosure 3 to be able to surround part of the support 2 from the open end 31, when an operator wishes to acquire biomagnetic signals from an organ of the patient 10. In other words, the magnetically shielded enclosure 3 is movable so as to be able to expose most of the body of the patient 10 at the beginning and end of the examination, and then to be able to slide along the axis X by the open end 31 so as to cover the body of the patient 10 at least in part, and reduce measurement disturbances during the medical examination.

[0050] This also allows the patient 10 to sit comfortably on the support 2, without being hindered by the presence of the magnetically shielded enclosure 3, and in particular facilitates obtaining biomagnetic measurements for patients with reduced mobility. Furthermore, once positioned at the start of the examination, the patient does not move.

[0051] Preferably, the position of the magnetically shielded enclosure 3 during acquisition is adapted to the type of examination to be performed. In particular, as illustrated in [Fig. 2], the magnetically shielded enclosure 3 does not necessarily completely cover the support 2 and the patient 10. This can reduce the feeling of claustrophobia during acquisition and further increase the comfort of the patient 10.

[0052] The magnetically shielded enclosure 3 is a magnetic shield. It typically comprises at least two layers of highly permeable material arranged concentrically around the X-axis. For example, the magnetically shielded enclosure 3 includes a layer of metallic alloy, for example, mu-metal or permalloy. This is referred to as "passive" shielding. Preferably, the magnetically shielded enclosure 3 also includes a layer of a highly conductive but non-permeable metallic material such as copper or aluminum. Increasing the number of layers advantageously reduces noise in biomagnetic measurements performed by sensors held in acquisition position.

[0053] It should be noted that these magnetic shields made of highly permeable materials must be distinguished from the much more common electrical shields, such as Faraday cages, or shields designed to attenuate electromagnetic or ionizing radiation. Indeed, these other shields are made of materials with high electrical conductivity and do not need to be made of materials with high magnetic permeability.

[0054] Alternatively or complementarily, the magnetically shielded enclosure 3 includes active shielding. "Active" shielding is defined as shielding obtained by a set of sensors and magnetic coils, configured to reduce some of the residual magnetic noise inside the magnetically shielded enclosure 3. More specifically, the magnetic coils can be driven to attenuate the magnetic noise measured by the associated sensors.

[0055] Sensor retention system

[0056] The sensor holding system 4 is integral with the support 2. For example, it includes one end rigidly fixed to the support 2. The sensor holding system 4 is configured to hold magnetic sensors opposite a body organ of the patient 10 in a position for acquiring biomagnetic signals. In other words, the sensor holding system 4 is typically intended to be equipped with one or more sensors, for example, a plurality of OPM-type magnetometers, which are arranged on the body of the patient 10.

[0057] The possible translational movement of the magnetically shielded enclosure 3 relative to the support 2 allows the sensor holding system to be easily positioned opposite the patient 10. Indeed, the operator, for example a healthcare professional, can install the biomagnetic sensors on the sensor holding system 4, without being hindered by the magnetically shielded enclosure 3. The operator has access to the body of the patient 10, and can easily manipulate the biomagnetic sensors in order to position the sensor holding system 4 in an optimal acquisition position.

[0058] More specifically, as illustrated in [Fig.1], the magnetically shielded enclosure can be in an installation position in which it does not surround the sensor holding system 4. After translation of the magnetically shielded enclosure 3 along the X axis, towards the patient 10, the magnetically shielded enclosure 3 can be in a magnetic isolation position, in which the magnetically shielded enclosure 3 surrounds the sensor holding system 4, as illustrated in [Fig.2].

[0059] Biomagnetic controller and sensors

[0060] The biomagnetic measuring device 1 further comprises a controller 5 connected to the sensor holding system 4 by a cable 6 configured to transmit a signal to the magnetic sensors, for example, an electrical signal and / or an optical signal. In particular, the cable 6 can be configured to transmit an optical signal, for example, laser radiation, to a magnetic sensor. The cable 6 can also be configured to electrically connect the sensor to the controller 5, for example, to power magnetic field generating coils or to power a plasma excitation circuit in the sensor's gas cell, and to transmit to the controller 5 biomagnetic signals acquired by the sensor, for example, by a photodiode of the sensor.

[0061] Each magnetic sensor is thus preferably connected by a cable 6 to the controller 5, the cables 6 being able to be gathered together in a sheath.

[0062] The controller 5 is a sensor control system. It is advantageously attached to the support 2. For example, the controller 5 includes a human-machine interface, allowing the operator to initiate the acquisition of biomagnetic signals. Preferably, the controller 5 can control the movement of the sensor holding system 4 around the acquisition position.

[0063] The biomagnetic measuring device 1 has the particularity that a portion of the cable 6 extending along the longitudinal direction X is fixed to the support 2. For example, a portion of the cable 6 can be fixed to the surface 21 of the support 2, or to a wall of the support 2. Alternatively or complementaryly, a portion of the cable 6 can be fixed inside the support 2.

[0064] Typically, each sensor held to the sensor holding system 4 is connected to the controller by a cable 6. Preferably, each cable 6 is fixed to the support 2 over most of its length along an axis substantially parallel to the X-axis of sliding of the magnetically shielded enclosure 3. The plurality of cables 6 can be gathered together in a common sheath.

[0065] Securing a portion of the cable 6 reduces the range of movement possible for the cable 6, and therefore reduces the risk of potential damage. In particular, the cable 6 is not subjected to mechanical stress during the translational movement of the magnetically shielded enclosure 3 relative to the support 2. This reduces the risk of device failures related to the cable 6.

[0066] For example, the controller 5 may include an electronic system, and optionally an optical system, for operating an OPM-type magnetic sensor, i.e., an optically pumped magnetometer. The biomagnetic measuring device 1 typically has a dynamic range between -250 nT and +250 nT, preferably between -50 nT and +50 nT. Advantageously, the amplitude of the magnetic field is less than 50 nT. The use of fields Low-amplitude magnetic fields reduce measurement errors caused by involuntary patient movement (e.g., 10). This allows for the acquisition of biomagnetic signals with high precision. The controller (5) can be used to monitor the acquired biomagnetic signals in real time.

[0067] In this embodiment, the sensor may comprise a cell containing an atomic gas, for example helium in the form of a plasma, which allows certain helium atoms to be brought to their first excited state. In another example, the cell may contain rubidium atoms in their ground state. The optical system comprises a laser configured to emit radiation passing through the sensor cell tuned to a specific atomic absorption line. A magnetic field in several directions is applied by a system of coils, for example Helmholtz coils, powered by current via cable 6. A photodiode can capture information relating to reflected radiation that has made a double pass through the cell, which is transmitted to the controller 5 via cable 6.The information is processed by controller 5 in order to determine a measurement of the weak magnetic fields coming from the brain of patient 10.

[0068] Laser radiation can be transmitted from a laser source to the sensor via an optical fiber, for example, an optical fiber maintaining the polarization of the laser radiation. As explained previously, the cable 6 can include both electrical wires for transmitting the electrical signals from the sensor, for example, from the photodiode, corresponding to biomagnetic signals, and an optical fiber held in a sheath for transmitting the radiation from the optical system. In some embodiments, the cable 6 does not include an optical fiber. The cable 6 can also include electrical wires for supplying current to means for exciting the gas contained in the sensor cell.

[0069] To improve patient comfort, particularly when using the biomagnetic measuring device to measure brain signals from patient 10, it is preferable to use the lightest possible cables. This reduces the weight exerted on patient 10 when the sensors are held in the biomagnetic signal acquisition position. Preferably, the cable comprises pico-coaxial wires with a diameter of less than one millimeter. For example, each magnetic sensor is connected to a cable comprising a sheath surrounding six pico-coaxial wires and an optical fiber. Alternatively or complementaryly, the cable 6 may comprise a printed cable with planar conductive tracks. Such cables are very fragile, despite the use of the sheath.

[0070] Furthermore, optical fiber is fragile and more susceptible to damage than standard copper wires. It is best not to twist or bend optical fiber cables, in particular to maintain a slight bend in the cable at all times.

[0071] Thus, in practice, for OPM-type magnetic sensors, it has been observed that the cables 6 are one of the main sources of failure. Therefore, it is particularly advantageous to maintain the cable 6 rigidly during the use of the biomagnetic measuring device 1. More generally, this allows the use of thinner and shorter cables 6, and thus reduces the weight borne by the patient 10 during the acquisition of biomagnetic signals. Furthermore, since the weight of the cable 6 is mainly borne by the support 2, it is also possible to use more reinforced cables 6 to increase the durability of the biomagnetic measuring device 1 without reducing the comfort of the patient 10.

[0072] Positioning of the magnetically shielded enclosure

[0073] Preferably, the translational movement of the magnetically shielded enclosure 3 is achieved by a sliding mechanism that does not induce strong vibrations or mechanical stresses on the highly permeable material layers. Thus, the biomagnetic measuring device 1 is not degraded by repeated use.

[0074] The sliding mechanism includes, for example, a slider, that is, a guide piece for the magnetically shielded enclosure 3 in the longitudinal direction. For example, as illustrated in [Fig. 1], the support 2 may include a rail forming a slide, and the sliding mechanism for the magnetically shielded enclosure 3 includes a plurality of wheels or rollers arranged in the rail. For example, as illustrated in [Fig. 3], the support 2 may include a rod or a cylindrical portion, and the sliding mechanism for the magnetically shielded enclosure 3 includes a ring for sliding on the rod.

[0075] The translational movement can be induced manually by the operator, for example by means of a crank or a handwheel connected to the sliding mechanism.

[0076] Preferably, the translational movement can be automatically controlled. Typically, the biomagnetic measuring device 1 then includes a control device configured to control the sliding mechanism and generate a translation of the magnetically shielded enclosure 3 relative to the support 2 in the longitudinal direction X. The controlled sliding mechanism may, for example, include a pneumatic system with cylinders. For example, the control device may include two push buttons, pressing the first button causing a translation of the magnetically shielded enclosure 3 in the longitudinal direction, and pressing the second button causing a translation of the magnetically shielded enclosure 3 in the opposite direction, so as to return to the installation position as illustrated in [Fig.1].

[0077] As explained previously, the control device allows the magnetically shielded enclosure 3 to move from an installation position in which the magnetically shielded enclosure 3 does not surround the sensor holding system to a magnetic isolation position in which the magnetically shielded enclosure 3 surrounds the sensor holding system 4.

[0078] The control device can be integrated into the controller 5. The operator can thus control both the movement of the magnetically shielded enclosure 3 and the acquisition of biomagnetic signals.

[0079] Advantageously, the position of the magnetically shielded enclosure 3 can be controlled according to a biomagnetic signal quality indicator. In this case, the controller is further configured to: - calculate the quality indicator of biomagnetic signals delivered by magnetic sensors; - compare the quality indicator to a threshold; and - when the quality indicator is above the threshold, order an additional translation of the magnetically shielded enclosure 3 relative to the support 2 along the longitudinal direction X.

[0080] This makes it possible not to cover too large a part of the patient's body. If the quality indicator is below the threshold, then the quality of the biomagnetic signals is sufficient. The sensors are therefore well positioned. Conversely, if the quality indicator is above the threshold, this may mean that there is significant noise, and that the organ in the patient's body from which magnetic signals are acquired is not sufficiently magnetically shielded. Moving the magnetically shielded enclosure 3 allows it to cover a larger portion of the patient's body 10, thus improving the quality of the measurements.

[0081] Typically, the quality indicator can be a noise indicator, corresponding, for example, to a standard deviation of the filtered signal in an appropriate frequency band, for example, a frequency range from 5 Hz to 80 Hz by removing a narrow band of frequencies around 50 Hz. The quality indicator can, according to another example, correspond to a signal-to-noise ratio (or SNR), around the alpha rhythm of brain signals from patient 10 (8 Hz to 12.5 Hz), measured when patient 10 has their eyes closed.

[0082] For example, if the quality indicator is a noise indicator, the threshold may be equal to 40 fT / Hz over the bandwidth from 5 Hz to 80 Hz, or if the quality indicator is a standard deviation of the noise, the threshold may be between 350 fT and 800 fT. Preferably, the choice of the threshold takes into account spurious brain signals, Heartbeats, blinks. In the example where the quality indicator is a signal-to-noise ratio on the alpha rhythm, the threshold can be between 2 and 5, typically equal to 3.

[0083] Preferably, the magnetically shielded enclosure 3 is a telescopic enclosure comprising a plurality of concentric enclosures mounted to move in translation relative to the support 2 along the longitudinal direction X. According to the sliding principle described above, the magnetically shielded enclosure 3 can be formed by several concentric layers of similar but not exactly equal diameter, the layers being able to slide relative to each other telescopically. This advantageously allows for a more compact biomagnetic measuring device 1. Indeed, the telescopic enclosure can cover a significant length of the patient's body 10 by sliding in shorter spaces. This reduces the overall size of the device 1 along the longitudinal direction (by increasing its thickness).It may also be simpler to move shorter segments of shielding, each segment constituting the magnetically shielded enclosure 3 being lighter.

[0084] Preferably, the support 2 comprises an outer enclosure 22, concentric with the magnetically shielded enclosure 3. As illustrated in the embodiment of [Fig. 3], the outer enclosure 22 can extend along the longitudinal direction X concentrically with the magnetically shielded enclosure. The outer enclosure 22 is configured to receive the magnetically shielded enclosure 3 when the sensor holding system 4 is not in the biomagnetic signal acquisition position, typically before the patient 10 is placed on the support 2. This allows, in particular, for the attachment of a human-machine interface for the controller 5, and also provides sufficient space for the installation of the device 1.

[0085] Positioning of the sensor retention system

[0086] In one embodiment, the support 2 may include a sensor attached to the support 2. For example, OPM type magnetic sensors may be made attached to the support 2, via the sensor holding system 4. In this case, the sensor holding system 4 is mounted on the stationary support 2, in the acquisition position.

[0087] Preferably, the sensor holding system 4 includes a positioning mechanism for the biomagnetic signal acquisition position. This allows the acquisition position to be adjusted according to the patient's morphology 10, for example their height or build, or according to the organ on which measurements are to be acquired.

[0088] Typically, the positioning mechanism includes a joint allowing translational movement of the sensor holding system 4 relative to the support along the longitudinal direction X. This allows the sensor support system 4 to be moved closer to or further from the patient's body 10, and allows the sensor to be installed in the acquisition position on the patient's body 10 at the start of the examination.

[0089] Preferably, the translational movement is possible with a travel between 0.5 cm and 50 cm, preferably less than 25 cm. The small travel of the sensor holding system 4 ensures fewer failures of the biomagnetic measuring device 1. Indeed, this allows the cable 6, which provides the connection between the sensor and the controller 5, to avoid tension and experience only very slight deformations during the examination.

[0090] The joint can also allow a translation of the sensor support system 4 relative to the support in another direction, for example in a direction orthogonal to the longitudinal direction X.

[0091] Preferably, the positioning mechanism includes a joint allowing rotation of the sensor holding system 4 around the longitudinal direction. This makes it possible to orient the sensors on the surface of the patient's body 10, typically ensuring that the sensors are oriented in a direction substantially orthogonal to the patient's body 10, opposite the organ of interest.

[0092] As before, the angular deflection is small, for example between 1° and 45°, preferably less than 20°. This prevents twisting of the cable 6 or reduces its radius of curvature when moving the sensor holding system 4 into the acquisition position. Preferably, the cable 6 includes a portion that is not fixed to the support 2, allowing sufficient length to perform the movements permitted by the positioning mechanism without exerting torsion or tension on the cable 6.

[0093] Preferably, the positioning mechanism includes a clamping device configured to exert pressure in the direction of the patient's body organ 10, so as to keep the sensor pressed against the patient's body organ 10.

[0094] Typically, the clamping device may include tension-elastic seals, which can be released when the sensor holding system 4 is in the acquisition position. Alternatively, the clamping device may include air cushions, which are deflated and then inflated when the sensor holding system 4 is in the acquisition position.

[0095] Such devices mechanically allow the sensors to position themselves to conform to the shape of the patient's body 10.

[0096] Preferably, the biomagnetic measuring device 1 can be used at room temperature. It does not require a heating or cooling system. Preferably, in order to improve patient comfort 10, the device 1 may include an air conditioning or ventilation system, configured to cool or ventilate the interior confined within the magnetically shielded enclosure 3 when patient 10 is installed in device 1. Alternatively or in addition, device 1 may include a heating system configured to heat or cool support 2 to improve the comfort of patient 10 when in position on support 2.

[0097] In the embodiment where the biomagnetic measuring device 1 is used for magnetoencephalography, the magnetic sensor holding system 4 is an optically pumped magnetometer holding system, as described previously.

[0098] Such a device 1 can be used to measure biomagnetic signals representative of the brain activity of patient 10. In this context, the organ of patient 10 at which the sensors are held in the acquisition position is the head of patient 10.

[0099] Preferably, the device 1 includes a projection system configured to project an image inside the magnetically shielded enclosure 3. The projection system may include a projector located outside the enclosure 3, a screen located inside the magnetically shielded enclosure 3 opposite the patient, and a mirror for directing the projected image onto the screen. The projected image is intended to be viewed by the patient 10 when the patient 10 is positioned on the support 2 and the magnetically shielded enclosure is in a magnetic isolation position. The projected image may be controlled by the controller 5. This embodiment is particularly advantageous when the magnetically shielded enclosure 3 covers the upper part of the patient 10's body, especially their head, as is the case during magnetoencephalography.This allows for the transmission of information to patient 10 during the acquisition of biomagnetic signals, such as the remaining time. It also allows for the entertainment of patient 10, thus improving their comfort and reducing their anxiety. Furthermore, it can stimulate patient 10's brain if the projected images correspond to specific stimuli.

[0100] Example of a sensor retention system 4

[0101] The sensor retention system 4 may include a helmet, intended to be placed on the patient's head 100. With reference to [Fig. 4], the sensor retention system 4 comprises a helmet 42 and an elastic clamping device 41, for example as described in patent FR3100125. The sensor retention system 4 here includes two joints 44 allowing a sliding pivot connection with the support 2 forming a frame.

[0102] The headset 42 comprises a plurality of ports 43, each intended to receive a sensor 7, typically a magnetometer. The headset 42 is designed to maintain a plurality of sensors 7, for example 64 sensors, in the acquisition position, 6 of which are schematically represented. The sensors 7 are arranged on the periphery of the Headset 42, so as to acquire biomagnetic signals from the brain. Each sensor 7 can be connected to the controller 5 by a cable 6. The cables 6 are attached to the support 2 by a retaining system 61.

[0103] The sensors 7 can preferably automatically identify their relative position with respect to each other. This is possible by local measurement of the magnetic fields, from which the controller 5 can calculate the relative distances and orientations of the sensors on the flexible helmet.

[0104] The immovability of the support 2 ensures that the sensor holding system 4 is ideally positioned on the patient's head 100 and cannot move to a suboptimal position when the patient 10 is covered by the magnetically shielded enclosure 3 for the examination. This ensures the reproducibility of the measurement, as the position is identical from one patient to another and from one examination to another.

[0105] Method for acquiring biomagnetic signals

[0106] With reference to [Fig.5], a method for acquiring biomagnetic signals is then described, according to another aspect of the invention.

[0107] The method includes a step SI of positioning the patient's body 10 on the support 2, the magnetically shielded enclosure being in the installation position PI in which it does not surround the sensor holding system 4 ([Fig.1]).

[0108] For example, initially patient 10 is completely outside the shielding. The patient then positions himself, for example, on a bed, the axis of which lies in line with the normal axis at the open end of the magnetically shielded enclosure 3. The absence of shielding around the body of patient 10 in step SI allows patient 10 to get comfortable.

[0109] Once the patient is positioned, a step S2 is performed to position the sensor holding system 4 in the biomagnetic signal acquisition position opposite the patient's body organ 10. The absence of shielding around the patient's body 10 in step S2 allows medical personnel to precisely position the sensors (placed, for example, on the helmet 5) on the patient's body 10, with complete freedom of movement to make this adjustment. Alternatively, the positioning of the sensor holding system 4 can be automatically controlled via the controller 5.

[0110] The magnetically shielded enclosure 3 can then move from the installation position PI to the magnetic isolation position P2 by translating along the longitudinal direction X. In other words, in a second step, the patient and the sensors with which they are equipped remain stationary, while, under the supervision of medical personnel, the magnetically shielded enclosure 3 slides along the axis orthogonal to its open end so as to cover a part of the patient's body so that the recording of their biomagnetic activity can be carried out with a high attenuation of the surrounding magnetic field. The translation of the magnetically shielded enclosure 3 can be carried out manually or controlled by the control device, possibly integrated into the controller 5.

[0111] Finally, an acquisition of biomagnetic signals by the magnetic sensors can be carried out during a step S4.

[0112] In a third phase, once the recording of biomagnetic signals is finalized, the magnetically shielded enclosure 3 can slide in the opposite direction to the direction of translation carried out during step S3, so as to return to the installation position PI where medical personnel can remove the sensors from the body of patient 10. Patient 10 can simply exit the device 1.

[0113] Method of using the device in an embodiment

[0114] The use of device 1 is described in detail here, in the embodiment illustrated in [Fig.3].

[0115] A horizontal support 2, for example a bed, allows the patient 10 to comfortably lie down. The sensor support system 4 consists of a headset and / or various accessories (e.g., a headrest) containing OPM-type magnetic sensors. The sensor support system 4 is positioned in line with the patient 10's position when lying down. The cables 6 of the OPM sensors pass through several openings in the support bed 2 and run under the patient 10's body to their connection with the controller 5. The few tens of centimeters of cabling between the OPM sensor and the openings provide the necessary clearance for adjusting the headset 4.The helmet can be equipped with a joint allowing it to slide along the axis of the support bed 2 to rest on the patient's head 10, as well as joints allowing it to slide in other directions, for example perpendicular to the bed, to ensure close contact between the sensors and the patient's head. These joints are operated by a healthcare professional who ensures that the upper part of the helmet is positioned precisely in contact with the patient's scalp 10. Other adjustment mechanisms, including for example drawstrings and sliders, allow movement of the sensors radially to the patient's head 10, in order to precisely adjust the acquisition position to the patient's morphology.These other degrees of freedom are also adjusted by the healthcare professional so that all the sensors are in contact with the patient's head 10, thus allowing the capture of cerebral biomagnetic signals with optimal amplitude.

[0116] The cylindrical magnetically shielded enclosure 3 is formed by a plurality of concentric layers, for example between two and five layers, typically three layers, of mu-metal. The magnetically shielded enclosure 3 is open at the end facing patient 10, and closed at the opposite end. Once With patient 10 installed and the headset positioned and adjusted optimally, the magnetically shielded enclosure 3 gradually slides along the longitudinal direction X, which is parallel to the axis of patient 10's body, from the installation position PI until it comes into the magnetic isolation position P2, covering patient 10's body, or the part of the body, here the head, that is the subject of the medical examination. The translation is made possible by a rail mechanism attached to the magnetically shielded enclosure 3, sliding on ball bearings (or simply wheels) mounted on the support 2. The support bed 2 is fixed to the device 1 at one end, the other end of which can rest on the inner surface of the magnetically shielded enclosure 3. In this case, a second rail and ball bearing mechanism ensures the sliding of the support bed 2 inside the magnetically shielded enclosure 3, the movement being driven by a flywheel meshed with a toothed wheel on a rack. The movement can also be driven by a chain drive or a pneumatic actuator. A force pressure sensor system ensures safe operation.

[0117] Once the magnetically shielded enclosure 3 has been moved to cover the patient's body 10, for example, up to the patient's belt 10, the healthcare professional checks on the controller's acquisition console 5 whether the signal quality indicator, reflecting, for example, the noise level, is satisfactory. If the quality indicator is below a threshold, the quality is sufficient and the healthcare professional starts the acquisition directly. Otherwise, they continue to slide the magnetically shielded enclosure 3 to cover the patient's body 10 until the quality indicator value is below the threshold. For example, the healthcare professional commands the magnetically shielded enclosure to move down to the height of the patient's knees 10 before starting the acquisition of the biomagnetic signals.

[0118] Once the acquisition of biomagnetic signals is finalized, the healthcare professional slides the magnetically shielded enclosure 3 back in the opposite direction, for example to the installation position PI, so that once the translational movement is finalized, the healthcare professional can loosen the cord systems and slide the headset 4 so as to remove it from the head of the patient 10. Once this has been done, the patient 10 can get up from the support bed 2.

[0119] It will be understood that the embodiment described above considers a simplified configuration of the device 1, in which the magnetically shielded enclosure 3 is open on the patient-side end.

[0120] Without departing from the scope of the invention, it is possible to use specific doors, fixed or not to the magnetically shielded enclosure 3 at both ends. In this case, the first door, located at the end on the patient side, has an opening to allow Passing the patient's body through the second door (10) reduces noise during biomagnetic signal acquisition. The second door, at the opposite end, remains closed during the examination. However, it can be opened during the patient positioning step (S1) or the sensor support system positioning step (S2) to allow the healthcare professional to adjust the joints, particularly on the patient's head (100). The second door may also have openings used if additional equipment is used during the examination and / or to add attachments to the support (2).

[0121] The above description mainly considers biomagnetic signal measurements for which magnetometers are placed on the patient's head 100. However, the proposed device 1 also allows examination of other parts of the patient's body 10. In this case, the patient 10 can be positioned on the support 2 in the opposite direction, for example, with their feet facing the open end of the magnetically shielded enclosure 3.

[0122] Furthermore, the two ends of the magnetically shielded enclosure 3 can be opened to magnetically isolate only the part of the body on which biomagnetic signals are to be measured. For example, the device 1 can be used to acquire biomagnetic signals from the brain (in the process called magnetoencephalography), the heart (magnetocardiography), or the nerves (magnetomyography).

[0123] In the illustrated embodiments, the support 2 is intended to receive the body of a patient 10 lying down. However, in other embodiments, the patient may be intended to be positioned on the support 2 in a seated or standing position. The support 2 may then comprise a chair or an armchair, and the X-axis of translation is substantially vertical.

Claims

Demands

1. A biomagnetic measuring device (1), comprising: - a support (2) extending along a longitudinal direction (X) and intended to receive a patient's body (10), - a magnetically shielded enclosure (3) extending along the longitudinal direction (X) and comprising an open end (31) opposite the support (2), - magnetic sensors (7), - a sensor holding system (4), integral with the support (2) and configured to hold the magnetic sensors (7) opposite an organ of the patient's body (10) in a position for acquiring biomagnetic signals, - a controller (5) connected to the sensor holding system (4) by a cable (6), the cable (6) being configured to transmit an electrical signal and / or an optical signal to the magnetic sensors (7),the biomagnetic measuring device (1) being characterized in that the support (2) is fixed and the magnetically shielded enclosure (3) is mounted movable in translation relative to the support (2) along the longitudinal direction (X), so as to be able to surround a part of the support (2) from the open end (31), and in that a portion of the cable (6) extending along the longitudinal direction (X) is fixed to the support (2).

2. Biomagnetic measuring device according to claim 1, wherein the controller (5) is further configured to: - calculate a quality indicator of biomagnetic signals delivered by the magnetic sensors (7); - compare the quality indicator to a threshold; and - if the quality indicator is greater than the threshold, command an additional translation of the magnetically shielded enclosure (3) relative to the support (2) in the longitudinal direction (X).

3. Biomagnetic measuring device according to any one of claims 1 and 2, wherein the sensor holding system (4) includes a positioning mechanism in the biomagnetic signal acquisition position.

4. A biomagnetic measuring device according to claim 3, wherein the positioning mechanism comprises a articulation allowing translational movement of the sensor holding system (4) relative to the support (2) along the longitudinal direction (X), with a travel between 0.5 cm and 50 cm, preferably less than 25 cm.

5. Biomagnetic measuring device according to any one of claims 3 and 4, wherein the positioning mechanism includes a joint allowing rotational movement of the sensor holding system (4) around the longitudinal direction (X), with a deflection between 1° and 45°, preferably less than 20°.

6. Biomagnetic measuring device according to any one of claims 3 to 5, wherein the positioning mechanism includes a clamping device configured to exert pressure in the direction of the patient's body organ (10), so as to keep the magnetic sensors (7) pressed against the patient's body organ (10).

7. Biomagnetic measuring device according to any one of claims 1 to 6, wherein the sensor holding system (4) is an optically pumped magnetometer holding system.

8. Biomagnetic measuring device according to claim 7, wherein the patient's organ (10) is the patient's brain (10).

9. A biomagnetic measuring device according to any one of claims 1 to 8, further comprising a control device configured to control a translation of the magnetically shielded enclosure (3) relative to the support (2) in the longitudinal direction (X), such that the magnetically shielded enclosure (3) moves from an installation position (PI) in which the magnetically shielded enclosure (3) does not surround the sensor holding system (4) to a magnetic isolation position (P2) in which the magnetically shielded enclosure (3) surrounds the sensor holding system (4).

10. Biomagnetic measuring device according to any one of claims 1 to 9, wherein the magnetically shielded enclosure (3) is a telescopic enclosure comprising a plurality of concentric enclosures mounted movable in translation relative to the support (2) along the longitudinal direction (X).

11. A biomagnetic measuring device according to any one of claims 1 to 10, wherein the support (2) comprises an external enclosure extending along the longitudinal direction (X) of concentrically to the magnetically shielded enclosure (3), configured to receive the magnetically shielded enclosure (3) when the sensor holding system (4) is not in the biomagnetic signal acquisition position.

12. Biomagnetic measuring device according to any one of claims 1 to 11, further comprising a projection system configured to project an image inside the magnetically shielded enclosure (3).

13. A method for acquiring biomagnetic signals, using the biomagnetic measuring device (1) according to any one of claims 1 to 12, comprising the steps of: - positioning the patient's body (10) on the support (2), the magnetically shielded enclosure (3) being in an installation position (PI) in which it does not surround the sensor holding system (4); - positioning the sensor holding system (4) in the biomagnetic signal acquisition position opposite the patient's body organ (10); - translating the magnetically shielded enclosure (3) along the longitudinal direction (X) from the installation position (PI) to a magnetic isolation position (P2), in which the magnetically shielded enclosure (3) surrounds the sensor holding system (4); - acquiring biomagnetic signals by the magnetic sensors (7).

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