ELECTRODE HELMET FOR ELECTRICAL RECORDING AND/OR STIMULATION

Abstract

For simplifying the application of electrical stimulation and/or recording of the human brain for therapeutical or diagnostic purposes, an electrode helmet (1) and associated fabrication techniques are provided. The helmet (1) is stable in shape, can be designed to carry a varying number of m electrodes (3) and has a patient-specific geometry that defines the relative position of each electrode with respect to the brain of the patient wearing the helmet (1). This approach improves the accuracy in stimulation and recording as well as the wearing comfort for the patient and allows tailor-made therapy and diagnostic with a component that can be customized at low costs based on a standard design.

Claims

1. A patient-specific electrode helmet (1) to be worn on a patient's head, the helmet (1) comprising: a shell (2) that is adapted to carry a number of m electrodes (3) configured for electrically contacting a scalp of a patient wearing the helmet (1); the shell (2) is stable in shape and has a patient-specific design according to data which specifies an anatomy of a skull of an individual patient for whom the helmet (1) is intended, such that a position of each of the electrodes (3) is defined with respect to a sagittal and a frontal plane extending through the patient's head of the patient wearing the helmet (1).

2. The helmet (1) according to claim 1, wherein the shell (2) at least one of a) includes a number of N electrode holders (4) each configured to hold a respective electrode (3) in place or b) comprises the m electrodes (3); at least one of each said holder (4) or each said electrode (3) is arranged on the shell (2) based on 3D design data derived from patient-specific anatomical 3D data measured from a patient's brain; and the helmet (1) enables at least one of patient-specific electrical stimulation or recording of a particular region of interest identified within the anatomical 3D data of the patient's brain.

3. The helmet (1) according to claim 1, wherein the shell (2) is fabricated via an additive manufacturing technique based on 3D design data derived from patient-specific anatomical 3D data measured from at least one of a patient's skull or brain.

4. The helmet (1) according to claim 1, wherein the shell (2) comprises at least two shell parts (11) that have each been fabricated using an additive manufacturing technique, the at least two shell parts (11) are interconnected to form the shell (2) such that a relative position to each other is fixed, and a left-hand shell part and a right-hand shell part of the at least two separate shell parts (11) are separated from each other by an S-shaped separation line that runs in between electrodes (3) carried by the left-hand shell part (11) and corresponding electrodes (3) carried by the right-hand shell part (11).

5. The helmet (1) according to claim 1, further comprising a number of N electrode holders (4), each configured to hold a respective electrode (3) in place, and the holders (4) are formed as integral parts of the shell (2).

6. The helmet (1) according to claim 5, wherein each said holder (4) includes a mechanical spring (5) for providing a contact force (23) for pressing an electrode (3) held by the holder (4), and the springs (5) are formed as integral parts of at least one of the respective holder (4) or of the shell (2).

7. The helmet (1) according to claim 4, wherein each said holder (4) includes an exchangeable electrode connector (6) with a socket (38) that is adapted to receive a contact pin (19) of a respective electrode (3), the exchangeable electrode connector (6) is insertable into the holder (4) in an insertion direction (36) and secured in place by inserting a contact pin (19) of an electrode (3) into the socket (38) of the connector (6) in a push-in direction (37) that extends diagonally to the insertion direction (36).

8. The helmet (1) according to claim 1, further comprising a built-in vibrational actuator (43) adapted to actively vibrate one of the electrodes (3).

9. The helmet (1) according to claim 1, wherein the shell (2) includes integrated electrical wiring (24) adapted to electrically contact electrodes (3) to be carried or carried by the shell (2), and the wiring (24) is at least one of a) embedded into the shell (2) or deposited on a surface of the shell (2), or b) fabricated using an additive manufacturing technique.

10. The helmet (1) according to claim 1, further comprising: a built-in signal processor (41) configured to control each of the electrodes (3), the processor (41) is configured to at least one of send out measured data to or receive control data from an external receiver unit (40) via a wireless communication interface (39).

11. The helmet (1) according to claim 5, wherein the shell (2) includes an inner hull and an outer hull fabricated separately, and one of the inner hull or the outer hull forms or carries at least one of said holders (4) or springs (5) included in said holders for providing a contact force (23) for pressing an electrode (3) held by the holder (4), and the other of the inner hull or the outer hull carries wiring (24) adapted to electrically contact electrodes (3) to be carried or carried by the shell (2).

12. The helmet (1) according to claim 1, further comprising a number of N electrode holders (4) each configured to hold a respective electrode (3), and a number of m non-invasive electrodes (3) configured for at least one of electrical stimulation or recording, and m N of the holders (4) are equipped with a respective one of the, non-invasive electrodes (3) which are individually addressable.

13. The helmet (1) according to claim 12, wherein the electrodes (3) of the helmet (1) comprise at least one of a) brush electrodes (9) featuring flexible and conductive brush filaments (10) for contacting the scalp of a patient, b) microneedles (44) designed to penetrate the scalp of the patient wearing the helmet (1), or c) injection molded flexible and conductive material.

14. The helmet (1) according to claim 12, wherein the electrodes (3) include an outer conductive coating (15) for reducing an electrical contact resistance to the skull, and the coating (15) is deposited on a micro-corrugation (16).

15. The helmet (1) according to claim 1, further comprising retaining structures (32, 39) that are adapted to form an undercut below a transversal plane (40) which extend through a center of a patient's ears, when the patient is wearing the helmet (1).

16. A series of patient-specific electrode helmets (1), each of the helmets (1) of the series is according to claim 5, and includes: a common design with at least one of a) an identical number of the electrode holders (4), a same type of exchangeable or integrated electrodes (3), c) fabrication using at least one of same materials or aa same additive manufacturing technique; and differs from other ones of the helmets (1) of the series in at least one of a) a patient-specific geometry of the shell (2), b) a patient-specific geometry of springs (5) of the holders (4), c) a patient-specific contact force (23) provided by individual ones of the springs (5), d) patient-specific electrode (3) arrangements, or e) patient-specific electrical wiring (24) implemented in the helmet (1).

17. An electrical stimulation and/or recording device (7), comprising: the helmet (1) according claim 1; a number of m electrodes (3) carried by the helmet (1); an electronic unit (8) connected to each of the m electrodes (3) and configured to at least one of a) provide or control electrical drive voltages to each of the electrodes (3), or b) detect or read-out electrical voltages recorded by the electrodes (3).

18. The device (7) according to claim 17, wherein the electronic unit (8) is configured to at least one of a) perform electrical impedance measurements using the electrodes (3) in reaction to a user input and to output a result of the impedance measurement to the user, or b) control and activate at least one vibrational actuator (43) comprised in the helmet (1) and configured to actively vibrate one of the electrodes (3) in reaction to a measured electrical impedance of that one of the electrodes (3).

19. A method for fabricating a shell (2) of a helmet (1), the shell (2) being adapted to carry a number of m electrodes (3) intended for electrical stimulation and or recording of the brain, the method comprising: fabricating the shell (2) in a patient-specific geometry, based on 3D design data that have been derived/computed from patient-specific anatomical 3D data measured from at least one of a patient's skull or a patient's brain, using an additive manufacturing technique.

20. The method according to claim 19, further comprising defining relative positions of at least one of the electrodes (3) or electrode holders (4) of the helmet (1) by the 3D design data, taking into account the at least one of a shape or location of the patient's brain within the skull of the patient, such that the fabricated helmet (1) enables at least one of patient-specific electrical stimulation or recording of a particular region of interest identified within the anatomical 3D data of the patient's brain.

21. A method for preparing an electrode helmet (1) for at least one of patient-specific electrical stimulation of or recording of nerve signals emanating from a particular region of interest inside a brain of a patient, using said electrode helmet (1), wherein the helmet (1) is the helmet according to claim 1, the method comprising: at least one of or mounting the m electrodes (3) on the shell (2) in a patient-specific arrangement that is defined by 3D design data that have been derived from patient-specific anatomical 3D data measured from at least one of a skull or brain of the patient, such that at least one of patient-specific electrical stimulation or recording of a region of interest is performable with the helmet (1).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Preferred examples of the present invention will now be described in more detail, although the present invention is not limited to these examples. With reference to the accompanying drawings, where features with corresponding technical function are referenced with same numerals even when these features differ in shape or design:

[0094] FIG. 1 shows an electrode helmet according to the invention in a perspective view,

[0095] FIG. 2 shows a shell part of another helmet according to the invention in a partial cross-sectional view,

[0096] FIG. 3 illustrates a side view on a brush electrode according to the invention,

[0097] FIG. 4 presents a top view on the electrode of FIG. 3,

[0098] FIG. 5 presents a perspective view on the electrode of FIG. 3,

[0099] FIG. 6 is a partial cross-sectional view of the electrode of FIG. 3,

[0100] FIG. 7 is the same view as that of FIG. 6, but now an conductive gel is introduced into a feed channel of the electrode,

[0101] FIG. 8 illustrates details of an electrode holder used in the helmets presented in FIGS. 1 and 2,

[0102] FIG. 9 shows a side view on another helmet according to the invention, which, together with a separate electronic unit, forms an electrical stimulation and recording device,

[0103] FIG. 10 is a bottom view on another helmet according to the invention, and finally

[0104] FIG. 11 presents a frontal view of the helmet of FIG. 10.

DETAILED DESCRIPTION

[0105] FIG. 1 shows a first example of an electrode helmet 1 according to the invention, which has been fabricated according to a patient-specific design. The helmet 1 comprises a shell 2 which carries a number of electrodes 3. Each electrode 3 is designed for electrically contacting the scalp of a patient wearing the helmet 1 with a respective contact area 14 (cf. FIG. 3). This helmet 1 can be used both for electrical stimulation of the brain and for recording of nerve signals from the brain, in particular w.r.t. to a specific region of interest (ROI) inside the brain, which has been identified in measured anatomical 3D data of the patient's brain, each time using the electrodes 3.

[0106] The shell 2 has been fabricated from a polyamide powder using a laser sintering machine, which makes it very easy to integrate ventilation openings 29 at desired locations (cf. FIG. 11). The shape of the shell 2, in particular its inner contour surface 34, is based on a set of 3D design data. The 3D design data are based on a common design of the helmet 1, which includes details of the outer shape of the helmet and mechanical parts of the shell 2 such as the electrode holders 4. The holders 4 are formed and fabricated as part of the shell 2 and each designed for holding a respective one of the exchangeable electrodes 2.

[0107] Using a 3D-scanner, the head of the patient for whom the helmet 1 is intended was previously scanned to obtain patient-specific anatomical 3D data which characterize the shape of the skull of the patient, in particular its outer dimensions. Taking these anatomical 3D data into account, a 3D design data file was calculated and delivered to the laser sintering machines as an input file. Accordingly, the helmet 1 shows an inner contour surface 34 to be brought into contact with the scalp of the patient wearing the helmet 1 that is tailor-made to the patient's skull. The helmet 1 thus shows a patient-specific geometry that matches the geometry of the skull that was 3D-scanned. Thereby a high comfort of wearing is achieved.

[0108] Moreover, the arrangement of the individual electrode holders 4 (cf. FIGS. 1, 2, 8-11) and thereby the individual electrode 3 can be adjusted during manufacturing of the helmet 1, based on anatomical 3D data measured from the patient's brain using MRI-scan images. Thereby, a specific electrode arrangement can be obtained on the helmet 1, which is ideally suited to stimulate a desired region of interest (ROI) inside the brain of the patient. The same approach can also be used for accurately recording nerve signals from a particular ROI identified inside of the brain, based on the measured anatomical 3D data. Of course, it is also possible to use m movable electrodes 3 on the helmet 1 and to simply arrange them according to a computed arrangement that is defined by 3D design data that have been computed from patient-specific anatomical 3D data measured from the patient's skull and/or brain. By such approaches, the helmet 1 can be tailored for a specific recording and/or stimulation task, taking into consideration the relative position of the ROI inside the helmet 1, when the patient is wearing the helmet 1. This allows higher accuracy when performing the electrical recording and/or stimulation.

[0109] The shell 2 is flexible but stable in shape, due to the solidity and flexibility of the polyamide. As a result, the position of each electrode 3 is well-defined with respect to a sagittal xy-plane and a frontal yz-plane running through the head of the patient wearing the helmet. In other words, the relative position of each electrode 3 w.r.t. the skull and thereby also to the brain of the patient can be guaranteed.

[0110] To avoid a dislocation of the helmet 1 relative to the skull (and thereby also to the brain) during use, the helmet 1 features several retaining structures, namely two cheek flaps 32 and a neck support 39. These structures each form an undercut below a transversal xy-plane 40 (that is illustrated by the thick horizontal dashed line in FIG. 2) which runs (horizontally) through the center of the patient's ears, when the patient is wearing the helmet 1. In the examples of FIGS. 1 and 2, the cheek flaps 32 and a neck support 39 even reach below the ears of the patient, which are positioned in the recesses 25 (cf. FIG. 2) when the patient is wearing the helmet 1. Thanks to the undercut, any rotation or lateral movement of the helmet 1 relative to the skull is prevented. Moreover, due to the patient-specific design that follows the anatomy of the patient's skull, the helmet 1 can only be worn in one well-defined position and orientation. As a result, the positions of the electrodes 3 relative to the skull and brain are fixed, as soon as the patient puts on the helmet 1. This is mainly achieved by the lower rim 30 of the helmet which follows the forehead, cheeks and neck of the patient (see quadrants Bi, Cj, Dj and Dk in FIG. 2). Accordingly, the patient-specific arrangement of electrodes 3 on the helmet 2 can be used for accurately stimulating and/or recording a particular ROI inside the patient's brain.

[0111] FIG. 2 presents an example of a helmet 1 according to the invention in which the shell 2 is assembled from two shell parts 11, namely two shell halfs. Shown is only one of the two halfs 11. This approach can speed-up fabrication by additive manufacturing techniques such as laser sintering, because only one half of the shell 2 has to be produced at once. As several shell halfs 11 can be easily stacked, they can be fabricated in a batch process from the same polymer powder using one laser sintering run within a few hours.

[0112] As explained previously, the electrodes holders 4 of the helmet 1 are formed as integral parts of the shell 2 (cf. FIGS. 1 and 2). In addition, each holder 4 of the shell 2 features a mechanical spring 5 in the form of a flexible flap that can provide a contact force that will press the respective electrode 2 mounted in the holder 4 into the scalp on the skull of the patient wearing the helmet 1 (cf. FIGS. 1 and 2). As indicated by the dashed lines in FIG. 1, in a rest position (i.e., without external forces applied) each of the holders 4 is slightly bend radially inwards. In other words, each holder 4 shows a negative deflection Δr (in radial direction) from a contact position defined by a contour surface of the patient's skull for whom the helmet 1 has been specifically designed. This deflection can also be described by the illustrated deflection angle α (cf. FIGS. 1, 8 and 11). Accordingly, the apices of the mounted electrodes 3 (in the rest position) would penetrate In imagined contour representing the outer surface of the skull of the patient—see FIG. 1 or for example FIG. 11.

[0113] When the patient puts on the helmet 1, each holder 4 is therefore deflected radially outward (as the skull pushes against the respective electrode 3) from the respective rest positions (i.e., the deflection angle α is lower—d)—see for example FIGS. 1, 2, 8, 10 and—11—against a force that is progressively produced by the respective spring 5, as the respective flap forming the spring 5 is bent outwards. As a result, an electrode 3 mounted to one of the holders 4 will be pressed onto the skull with a defined contact force 23 as soon as the patient puts on the helmet 1.

[0114] The amount of force that is produced can be fine-tuned by changing the amount of deflection (in particular said deflection angle α present in the rest position) and/or by changing the stiffness of the spring 5. Accordingly, the contact force 23 may vary from helmet 1 to helmet 1 but also with the position of the holder 4, as illustrated by the black arrows in FIG. 11. For example, some of the springs 5 used may be weakened by thinning the shell 2 at their location or, as shown in FIG. 11, by introducing recesses 5 that effectively reduce the cross-section and thereby the stiffness of the respective spring 5. The patient- and/or location specific contact force 23 that is provided by each spring 5 can be defined in the 3D design data employed in the additive manufacturing of the shell 2.

[0115] FIGS. 3 to 7 present further details of the electrodes 3 used together with the helmet 1. The electrodes 3 are designed as exchangeable brush electrodes 9 and have been fabricated by injection molding using a conductive polymer rubber mix. The molded body 18 of the electrodes 3 forms a number of flexible brush filaments 10. As the whole body 18 is electrically conductive, the electrodes 3 can be electrically contacted in the area of the illustrated contact pin 19.

[0116] The contact pin 19 of the electrode body 18 features a cross-sectional thickening 31 (cf. FIGS. 3-7). As illustrated in FIG. 8, this thickening 31 can interact with a corresponding groove 33 that is formed on an inner side of a socket 38 of a separate electrode connector 6.

[0117] The assembly of the electrodes 3 into the helmet 1 is performed as follows: First, the connectors 6 are slid into the respective holder 4 along the insertion direction 36 illustrated in FIG. 8. Note that the holder 4 will transfer the contact force 23 provided by the spring 5 to the connector 6. Next, the brush electrode 3 is inserted from inside the helmet 1 into the connector 6 by pushing the electrode 3 radially outwards along the illustrated push direction 37 into the socket 38 of the connector 6—see FIG. 8.

[0118] Thanks to the thickening 31 formed at the contact pin 19 of the electrode 3, the latter will snap into the socket 38 and be fixed in position. A similar mechanical snap-in mechanism secures the connector 6 to the holder 4. Also note that the connector 6 is additionally secured in place by the inserted electrode 3, since the push direction 36 runs diagonally to the insertion direction 36. Finally, a respective electrical cable (not shown in the Figures) may be fitted to the outer end of the connector 6, which also forms a contact pin 19 (cf. FIGS. 8 and 9).

[0119] FIG. 6 illustrates that the electrodes 3 may feature an outer conductive coating 15 for reducing the electrical contact resistance to the skull. This coating 15 has been deposited on a micro-corrugation 16 that is formed in a surface 17 of the body 18 of the electrode 2, in the region of the brush filaments 10.

[0120] FIG. 7 illustrates the use of a conductive gel 12 that can be inserted into a feed channel 13 formed by the body 18 of the electrode 3. This way, the contact resistance of the electrode 3 in the contact area 14 can be lowered significantly. The symmetric positioning of the brush filaments 10 with respect to the feed channel 13 results in a uniform distribution of the gel 12 on the electrode 2 after injection of the gel 12 through the feed channel 13.

[0121] FIG. 9 illustrates an alternative to connecting the connectors 6 (and thereby each electrode 3 contacted by the respective connector 6) to individual cables (resulting thus in a number of cables equal to the number m of electrodes 3 used in the helmet 1): The shell 2 of the helmet 1 can be equipped with an integrated wiring 4, as indicated by the dashed lines. This wiring 4, which may be embedded in the shell 2 and which may be formed by additive manufacturing techniques, can be designed to the needs of the patient such that all electrodes 3 present in the patient's helmet 1 are electrically contacted by the wiring 4. We note at this point, that depending on the region of the brain to be stimulated or recorded with the helmet 1, not all of the holders 4 necessarily need to be equipped with a corresponding electrode 3 (Hence some of the electrodes 3 shown in the Figures may be omitted, while it is easier for design and fabrication to maintain the holders 4).

[0122] In a more advanced version of the helmet 1, the cable 26 shown in FIG. 7 may be replaced by a wireless (preferably bidirectional) wireless data connection 42. For this purpose, the electronic unit 8 may comprise a receiver unit 40 for communication with a wireless communication interface 39 built-into the helmet 1. A processor 41 (with additional electrical power source and driving circuitry) built-into the helmet 1 may then be used to read-out the electrodes 2 and/or to provide driving voltages to the electrodes 2, in particular according to commands received from the electronic unit via the wireless data connection 42.

[0123] In addition, the helmet 1 can feature a cable connector 27, as shown in FIG. 9, to establish an electrical link between the integrated wiring 24 and an external electronic unit 8 via a (multi-core) cable 26. The electronic unit 8, which may be designed as a wearable neck-band, can be worn by the patient while the helmet 1 is mounted on his skull. The components shown in FIG. 9 thus form an electrical device 7, which may be used as electrical stimulation and/or recording device 7 outside of hospitals by the patient himself.

[0124] As described in the claims and above, the electronic unit 8 may also be configured to perform impedance measurements using the electrodes 3 of the helmet to obtain a measure of the contact resistance of each of the electrodes 3. If the measured impedance is too high, more conductive gel 12 can be applied to the respective electrode 3 via the feed channel 13 from outside (i.e. the helmet 1 can remain in place on the skull).

[0125] In summary, an electrode helmet 1 and associated fabrication techniques have been proposed for simplifying the application of electrical stimulation and/or recording of the human brain for therapeutical or diagnostic purposes. The helmet 1 is stable in shape, can be designed to carry a varying number of m electrodes 3 and is characterized in that it features a patient-specific geometry that defines the relative position of each electrode with respect to the brain of the patient wearing the helmet 1. This approach improves the accuracy in stimulation and recording as well as the wearing comfort for the patient and allows tailor-made therapy and diagnostic with a helmet that can be customized at low costs based on a standard design and benefitting from accurate anatomical data obtained from a 3D scan or medical imaging of the patient's skull.

LIST OF REFERENCE NUMERALS

[0126] 1 helmet [0127] 2 shell [0128] 3 electrode [0129] 4 holder (for holding 3 in place) [0130] 4 spring/bending beam [0131] 6 electrode connector (for electrically contacting 3) [0132] 7 electrical stimulation and/or recording device [0133] 8 electronic unit [0134] 9 brush electrode [0135] 10 brush filament [0136] 11 part (forming 2) [0137] 12 conductive gel [0138] 13 feed channel [0139] 14 contact area (of 3) [0140] 15 conductive coating [0141] 16 micro-corrugation (formed in 17) [0142] 17 surface (of 18) [0143] 18 body (of 3, preferably injection-moulded) [0144] 19 contact pin (of 3 or 6) [0145] 20 mounting surface (formed on interior side of 4/2/32) [0146] 21 counter surface (of 3) [0147] 22 insertion opening (in 4 for introducing 3) [0148] 23 contact force [0149] 24 electrical wiring (for contacting 3) [0150] 25 recess (for the patient's ear) [0151] 26 cable (of 8 for electrical connection to 1/27/24) [0152] 27 cable connector (of 1, for connection to 26) [0153] 28 slit (in 2 for defining 5) [0154] 29 ventilation opening [0155] 30 (lower) rim (of 1) [0156] 31 cross-sectional thickening (of 18/19 of 3) [0157] 32 cheek flap (of 1/2) [0158] 33 groove (in 6 for interaction with 31) [0159] 34 inner contour surface (of 1/2) [0160] 35 recess/opening (for weakening 5) [0161] 36 insertion direction (when inserting 6 into 4) [0162] 37 push direction (when 3/19 is pushed into 6) [0163] 38 socket (of 6 for insertion of 3) [0164] 39 wireless communication interface (e.g., bluetooth) [0165] 40 receiver unit [0166] 41 processor [0167] 42 wireless data connection [0168] 43 vibrational actuator [0169] 44 microneedles