Magnetoencephalography Apparatus

Abstract

A magnetoencephalography (MEG) apparatus comprising a helmet shaped and configured to fit a range of human head sizes and/or shapes, the helmet comprising a plurality of openings disposed in predetermined locations around the helmet, each opening being adapted to receive a magnetoencephalography field sensor in an arrangement such that the magnetoencephalography field sensor is moveable in a direction towards or away from a human head inside the helmet

Claims

1. Magnetoencephalography (MEG) apparatus comprising a helmet shaped and configured to fit a range of human head sizes and/or shapes, the helmet comprising, a plurality of openings disposed in predetermined locations around the helmet, each opening being adapted to receive a magnetoencephalography field sensor in an arrangement such that the magnetoencephalography field sensor is moveable in a direction towards or away from a human head inside the helmet.

2. MEG apparatus according to claim 1, wherein the helmet further comprises a fixture for fixing the helmet securely in position on a human head,

3. MEG apparatus according to claim 1 or claim 2, wherein the magnetoencephalography field sensor is an Optically Pumped Magnetometer (OPM).

4. MEG apparatus according to any one of claims 1 to 3 comprising at least two magnetoencephalography field sensors, each received in an opening in the helmet, in which at least one of the magnetoencephalography field sensors and/or the opening in which it is received is/are provided with indicia showing the position of the magnetoencephalography field sensor relative to the opening in the direction towards or away from a human head inside the helmet.

5. MEG apparatus according to any preceding claim in which the or each magnetoencephalography field sensor is adapted to move in a spiral path relative to helmet to move in the direction towards or away from a human head inside the helmet.

6. MEG Apparatus according to any preceding claim in which the or each magnetoencephalography field sensor is mounted in a housing which is releasably mountable within the openings in the helmet, the sensor being movable with relation to the housing so as to provide the capability of movement of the magnetoencephalography field sensor in a direction towards or away from a human head inside the helmet when the housing is mounted to an opening.

7. MEG apparatus according to claim 5 in which at least one of the magnetoencephalography field sensors and/or the housing(s) in which it is/they are mounted is/are provided with indicia showing the position of the magnetoencephalography field sensor relative to the housing in the direction towards or away from a human head inside the helmet

8. MEG apparatus according to any preceding claim in which the helmet is provided with apertures between the openings.

9. MEG apparatus according to claim 7 in which the helmet has an open lattice structure surrounding the openings.

10. A kit of parts comprising a helmet according to any one of claims 1 to 9, at least one magnetoencephalography field sensor, and a mount comprising a housing which is releasably mountable within the openings in the helmet for retaining the at least one magnetoencephalography field sensor therein according to any one of claims 6 to 7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The invention will now be described by way of example and with reference to the accompanying figures, in which;

[0021] FIG. 1 is a schematic exploded view of a mechanism for mounting a sensor to a helmet such that the sensor is movable towards or away from the interior of the helmet in accordance with the invention;

[0022] FIG. 2 is a side elevation view of the mechanism of FIG. 1;

[0023] FIGS. 3 (a) to 3(c) are plan views of each of the elements of the mechanism of FIGS. 1 and 2, and

[0024] FIG. 4 is a photograph of a helmet for mounting the mechanism of FIGS. 1 to 3.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] FIG. 1 shows in exploded view a mechanism 1 for mounting a sensor to a helmet such that the sensor is movable towards or away from the interior of the helmet, to provide an MEG apparatus in accordance with the invention. FIGS. 2 and 3 are side elevation and plan views of the same mechanism 1. The mechanism 1 comprises three main elements, an inner collar 2, an outer collar 4 and an inner slider 6; all are generally cylindrical in shape, and are illustrated exploded along the common longitudinal or cylindrical axis XX about which they are assembled in use. In use, the three elements are nested with the outer collar 4 outermost and the slider 6 innermost, with the inner collar 2 sandwiched between them. The inner collar 2 is provided with a number of spiral cutouts which form pathways for lugs 10 on the exterior of the slider 6 to slidingly engage. Outer collar 4 is provided with longitudinal slots 12 which also slidingly engage with lugs 10 (which lugs are sufficiently long in the radial direction to simultaneously engage with both the cutouts and the slots, so that the lugs are free to slide relative to both, there being sufficient tolerance between the lugs and the cutouts and slots to permit this but to prevent and significant loose “play”).

[0026] When the three elements 2, 4, 6 are assembled in their nested positions and the outer collar 4 is rotated relative to the inner collar 2 (or vice versa), the slots 12 will urge the lugs 10 on the slider 6 to move in a circular direction about the longitudinal axis. Because the lugs 10 are held within the spiral cutouts 8, the lugs 10 will also follow their spiral path, and the inner slider 6 will both rotate and translate longitudinally along the axis of the mechanism 1, causing an MEG sensor (shown schematically at 14) held within the slider 6 to be moved along the common axis. The amount of axial movement will be a function of the angle of the spiral cutouts 8 to the axis and the amount of relative rotary movement between the inner and outer collars 2, 4. There are a number of radial markers 16 disposed around the edge of the outer collar 4, and when the mechanism 1 is assembled a marker 18 provided on the outer edge of the inner collar 2 is aligned with the radial markers 16 to give a visual indication of how far the slider 18 has moved along the axis; the spacing between the radial markers 16 is preferably chosen so as to correspond to a predetermined amount of longitudinal movement of the slider 6 (for example, the radial markers 16 may be disposed and the spiral angle of the cutouts 8 chosen so that the circumferential distance between adjacent radial markers equates to a longitudinal movement of the slider 6 of 0.1 mm, or 0.5 mm, or 1 mm).

[0027] The inner collar 2 may be fixed in use and the outer collar 4 rotated by gripping the exterior of the outer collar 4, or the outer collar 4 could be fixed and the inner collar 2 rotated using the knurling 20 at the top of the inner collar 2. FIG. 4 shows a helmet 40 which is provided with multiple openings 42, each of which is shaped and configured to receive and releasably hold a mechanism 1 as described above (in FIG. 4, the openings 42 are adapted to receive the inner collar 2 of the mechanism, but they could equally be adapted to receive the outer collar 4 instead). Each mechanism 1 may have an outer collar 4 and a slider 6, so as to retain an MEG field sensor (not shown in FIG. 4) which can be accurately moved inwardly or outwardly in relation to the helmet 40; the shape and configuration of the helmet 40 and its openings 42 are precisely manufactured so that the position and axial orientation of the openings 42 is known with a high degree of accuracy, so that the position and orientation of the MEG field sensor relative to the head of the subject inside the helmet 40 can be easily and accurately determined. The use of rotational movement to drive axial movement of the sensor is inherently resistant to reversal, which is advantageous because it means that the sensor will resist being pushed axially out of its desired position. The helmet 40 is formed in a lattice structure, which means the helmet is light to wear and also allows heat generated by the sensors to dissipate. In some embodiments, there is a chinstrap 44 which holds the helmet in a fixed position relative to the subject's head.

[0028] In a preferred embodiment, the helmet is a 3D-printed helmet 40 based on average adult head sizes. The helmet geometry may be defined based on standard size and shape data of certain human characteristics, including age, sex, and/or medical condition affecting the size and shape of the skull. The helmet is formed of a rigid material. Any suitable known material may be selected. The rigidity of the structure holds the sensors in a fixed position with respect to the wearer, and in a fixed orientation with respect to each other.

[0029] In a further embodiment, the helmet may be fabricated by casting, by a plastic injection moulding process, or similar such methods.

[0030] In order to accurately define the location of the sensor mounting mechanism 1 with respect to the underlying anatomy of the wearer, and correlate this information to specific locations on the helmet, data captured by imaging can be used to register the known shape of the helmet, and to determine the features of the wearer's anatomy. The location of specific aspects of anatomy, including location of bone and soft tissue, of the wearer can be mapped to an appropriate granularity. The location of action potentials and individual neurons may be determined according to the scanning technique used to record the relevant anatomical data.

[0031] Any suitable technique may be used to determine the shape and dimension of the helmet, including 3D scanning using cameras or other equipment, or simply design data taken from manufacturing logs and CAD models. Anatomical data may be captures using any available medical imaging process.

[0032] Once the data relating to the geometry of the helmet and the wearers anatomical features is determined, the position and orientation of the sensor array with respect to the head can be determined and recorded. The location of each sensor relative the underlying anatomical structure is recorded and used to determine the nature and cause of the magnetic activity in the brain.

[0033] As the OPMs can reach temperatures of around 40 degrees, in a preferred embodiment, the helmet is designed with an open ‘lattice’ structure to allow for air flow which carries the heat away from the head. The inventors have noted a high rate of success with the scanning of adults.

[0034] In an alternative embodiment, particularly where non-standard head size and shape is present in the user, the helmet may be formed of a more flexible material. The helmet may be adjusted to fit the user by means of known retention and adjustment mechanisms, some of which may include the means to record the adjustments required to fit the helmet to a specific wearer. The dimensions of the helmet may then be recorded while the helmet is fitted to the searer, and the underlying anatomy of the wearer mapped to the helmet accordingly.

[0035] The use of flexible material is possible because the mount for each magnetic field sensor is of a fixed orientation and variable axial position. Consequently, the proximity of each magnetic field sensor is unaffected by pressure of the head on the inside surface of the helmet, or by resilience in the helmet material or construction.

[0036] It will of course be understood that many variations may be made to the above-described embodiment without departing from the scope of the present invention. For example, there could be fewer or more cutouts, lugs and slots than are shown in the drawings (although we find that four provides sufficient accuracy of movement and positioning while not introducing too much friction to inhibit easy movement of the elements), and the spiral angle of the cutouts can be chosen to increase or decrease the amount of axial movement relative to the relative rotational movement of the elements.

[0037] Where different variations or alternative arrangements are described above, it should be understood that embodiments of the invention may incorporate such variations and/or alternatives in any suitable combination.