Bio magnetic measuring apparatus

Abstract

A bio magnetic measuring apparatus adapted to be placed in contact with the surface of a patient's body or head and to conform to the shape thereof, comprising an array of hexagonal sensor holders for holding bio magnetic sensors against the surface of the patient, the edges of adjacent sensor holders being provided with means for linking the adjacent sensor holders together, different linking means allowing differing degrees of freedom of relative movement between adjacent sensor holders.

Description

[0001] Bio Magnetic Measuring Apparatus

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to apparatus which employ a plurality of bio magnetic sensors for use in measuring or mapping bio magnetic activity occurring in a patient by recording the magnetic fields produced by electrical currents which occur naturally in the patient's body, particularly but not exclusively in the brain (i.e. magnetoencephalography (MEG)), the heart (magnetocardiography), the stomach (magnetogastrography), the muscles (magnetomyography) or the spine (magnetospinography), or bio magnetic signals which are produced by an unborn foetus.

[0004] BACKGROUND ART

[0005] There are two general types of apparatus which support bio magnetic sensors, namely those which are rigid and which support the sensors so that they are accurately and consistently located relative to one another and accurately directed towards the patient, such as in the MEG apparatus of GB2607881, and those which are flexible and adapted to conform to the shape of the body or head they are placed against, such as in the concussive monitoring system of US 2022 / 061740. The former type is generally subject-specific and therefore expensive, the time to manufacture each helmet is extensive, the helmets need to be stored between patient visits and the correct helmet retrieved for each patient, and it is a lengthy process to switch sensors from helmet to helmet for different patients. The latter type of sensor holder is usually made of a flexible material, such as leather or fabric, and so are good at adapting to the shape of a patient's head or body and so can be used for different patients, and are less expensive than rigid arrangements; however, flexible arrangements do not always hold the bio magnetic sensor in a fixed orientation relative to the patient's head or body.

[0006] SUMMARY OF THE INVENTION

[0007] The present invention is predicated on the realisation that a combination of rigidity and flexibility in the arrangement holding the bio magnetic sensors relative to each other can provide the benefits of both types of apparatus described above. The present invention therefore provides a bio magnetic measuring apparatus adapted to be placed in contact with the surface of a patient's body or head and to conform to the shape thereof, the apparatus comprising an array formed of a plurality of bio magnetic sensor holders, each sensor holder being adapted to hold a bio magnetic sensor releasably yet rigidly within the sensor holder and linked to at least three adjoining sensor holders along common, predominantly linear edges, in which at least some of the links between at least some of the adjoining sensor holders restrict these adjoining sensor holders to move freely relative to one another with only one degree of rotational freedom about an axis parallel to the common, predominantly linear edges and between limits.

[0008] Such an arrangement allows the formation of a tessellated array of sensors which is sufficiently flexible to conform to the shape of those larger parts of a patient which are subjected to bio magnetic measurement, such as a chest, back or head, but sufficiently unyielding so that control of the orientation and / or positioning of the individual sensors is sacrificed. A single, generic apparatus can be used by different participants with different sized and shaped bodies or heads, whilst at the same time allowing the sensors to be positioned in contact with and relative to the participant's skin with the required positional and orientational accuracy. We have found that such a "conformal mat" of sensors can be used as an MEG apparatus with the advantages of both the rigid and flexible types of prior art arrangements and without the disadvantages of either.

[0009] In the arrangement described above, the wording "move freely", "only one degree of rotational freedom" and "between limits" is used to denote that the intention is to allow the free rotation of the adjacent holders about the axis, but that that freedom is limited to a specific range of rotation. In some examples the specific range of rotation may include a rotational range of less than 125-degrees, preferably less than 90-degrees, more preferably less than 60-degrees and even more preferably less than 30-degrees. It should also be understood that most mechanical linkages will allow a certain amount of tolerance, or "play" in other rotational and translational directions, and that the present invention should therefore be construed as encompassing arrangements where the restriction of the other five degrees of freedom is not total but where the freedom of movement in those other five degrees of freedom is still significantly less than that in the one degree of rotational freedom.

[0010] The links allowing at least one degree of rotational freedom are preferably mechanical in nature, such as curved arms extending outwardly from the common, predominantly linear edges which are shaped so as to interlink with arms extending from the side of the adjacent sensor holder. The curved arms can be provided in pairs on each predominantly linear edge, and may have a small gap between their distal ends so that adjacent pairs of arms can be connected to each other in a snap fit by squeezing the two gaps against each other, temporarily deforming the arms until their resilience allows the two sets of arms to interlink and the adjacent sensor holders to rotate relative to each other. This allows the conformal mat to be easily put together in a particular shape of conformal mat, and easily taken apart so as to be reattached in a differently shaped conformal mat. Such arrangements can be cheaply and easily manufactured by being made of a semi rigid plastics material by injection moulding, for example.

[0011] At least some of the links between at least some of the adjoining sensor holders may allow these adjoining sensor holders to move relative to one another with six degrees of freedom. Such an arrangement allows there to be much more relative movement between adjacent sensor holders, and for these to move apart and create gaps in the tessellation; this is desirable where the apparatus is intended for measuring bio magnetic fields in a part of the patient which has a sufficiently complicated shape (e.g. the cranium) that a conformal mat would not be able to conform closely enough to the shape of the patient if all of the links between adjoining sensor holders were of the type permitting only one degree of freedom of rotational movement. The links allowing six degrees of freedom may be elastic bands which connect to retaining clips on the sensor holders.

[0012] Preferably the bio magnetic sensor holders have predominantly the same geometric shape as seen in the direction they contact the patient. This allows the sensor holders to be linked together in different relative orientations. Preferably the shape is hexagonal, or any other regular polygonal shape which allows adjacent sensor holders to form a tessellation (i.e. a tiling where there are no overlaps or gaps between adjacent sensor holders) when formed on a flat, planar surface, such as triangular or square. When the tessellation is placed against a non-flat patient, the sensor holders will rotate and / or move in other ways relative to adjacent sensor holders so as to conform to the shape of the patient. The plurality of sensor holders may be arranged in an array which has gaps; this allows a conformal mat to be placed around a head or other body part so that the gaps between adjacent sensor holders to close as the shape of the mat changes from planar to conformal, and these gaps can be held closed by interlinking their edges as they are brought together, either by mechanical linkage or an elastic band. It is envisaged that an individual sensor holder may have edges adapted to link to adjacent sensor holders in any combination of one degree of freedom linkage and six degrees of freedom linkage. For example, a hexagonal sensor holder may have one, two, three, four, five or six sides adapted to link with one degree of rotational freedom, and similarly it may have any number between one and five sides adapted to link with six degrees of freedom of movement, and where there are several of each type of linkages, these may be disposed around the circumference of the sensor holder in any sequence. Thus, an array of sensor holders can be put together by joining adjacent sensor holders with the desired degrees of freedom so that when folded against the patient the array conforms as closely as possible to the shape of the patient.

[0013] At least two of the sensor holders may have an eyelet for attaching a strap. This allows the array of sensor holders to be strapped to the patient; if the array is to surround the cranium for example, the two sensor holders with eyelets would be positioned at the sides of the helmet, to attach a helmet strap.

[0014] The sensor holders may have legs extending in use away from the surface of the patient which are adapted to guide a bio magnetic sensor as it is placed into the sensor holder. Once the array of sensors has been manipulated to conform to the shape of the patient and secured in place, sensors can be inserted into some or all of the sensor holders, according to where bio magnetism is to be measured. Additionally or alternatively, the sensor holders may have legs extending in use away from the surface of the patient which are resilient and adapted to receive and to hold a bio magnetic sensor in the sensor holder in a snap fit arrangement. Such resilient legs are suitably formed of a plastics material. The sensor holders may be integrally formed in one piece of a plastics material.

[0015] Apparatus in accordance with the invention may be provided in kit form.

[0016] BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention will now be described by way of example and with reference to the accompanying figures, in which;

[0018] Figure 1 is a perspective view of three different types of sensor holders which are interlinked to form a bio magnetic measuring apparatus in accordance with the invention; Figure 2a, 2b and 2c are perspective views of three different types of sensor holders which may be interlinked to form a bio magnetic measuring apparatus in accordance with the invention, and

[0019] Figures 3a and 3b are plan views of an apparatus in accordance with the invention forming a helmet for use in magnetoencephalography laid on a flat surface.

[0020] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Figure 1 shows three different variants of sensor holders, 2a, 2b, 2c, each having a hexagonal plate 4 defined by six edges. Above the plate 4 (towards the top of the drawing) each of the variants shown in the drawing 2a, 2b, 2c are the same; below the plates 4 there are different arrangements for interlinking adjacent sensor holders, as described below. Extending upwardly from each plate 4 are six legs: four legs 6a are adapted to guide a bio magnetic sensor (not shown in Figure 1, but having the shape of a rectangular prism) into the sensor holder (downwardly as shown in the drawing), and two legs 6b are adapted to releasably retain the bio magnetic sensor in the sensor holder once fully inserted. Legs 6a are disposed at the vertices of a square hole in each plate 4 and are shaped so as to receive the end face of the bio magnetic sensor and to guide the long side of the rectangular prismshaped bio magnetic sensor downwardly into the sensor holder 4 so that the bio magnetic sensor passes through a rectangular hole h in the plate 4 until it abuts a square bottom plate 10. Legs 6b act as a resilient tang, are forced apart as the sensor passes through them, and spring back inwardly so as to latch onto the top surface of the bio magnetic sensor when the sensor contacts the bottom plate 10 in a releasable snap fit arrangement. Thus the bio magnetic sensor is held in the sensor holder (to remove the sensor, the tops of the legs 6b are pulled apart, releasing the bio magnetic sensor top surface so that the bio magnetic sensor can be extracted). The bottom plate 10 has a central aperture so that there is nothing between the bottom end surface of the bio magnetic sensor, which is adapted to sense the bio magnetic field, and the surface of the patient which might occlude the sensor and impair its sensing ability; the apertures also facilitate removal of the sensor. In some applications, a planar element may be provided underneath the sensor, such as a sheet of thermal insulation to protect the patient from sensor heat and reduce conducted thermal energy to the patient, whilst maintaining proximity to the patient and minimising offset for protection. The apertures in the bottom are shown as rectangular but they may be any shape, provided that they are small enough not to allow the bio magnetic sensor to be pushed through in a downward direction, and are preferably shaped and oriented so as to provide the minimum obstruction between the bottom surface of the sensor and the surface of the patient.

[0022] The differences between the three sensor holders shown all relate to how adjacent sensor holders are linked together, and are all below the hexagonal plate 4. Sensor holder 2a is provided along each of its six edges, parallel to the sides of the hexagonal plate 4, with curved arms 8 which form an arc with a segment missing, which forms a gap g between the two arms along one edge; the arms 8 are resilient and the gaps g are sized such that the adjacent edges of two adjacent sensor holders 2a and 2 can be pressed together until the arms 8 snap fit to link together. When so linked, the linkage is designed so that the arms 8 allow adjacent sensor holders to rotate relative to one another about an axis parallel to the common edge of the adjacent hexagonal plates 4, but resist as much as possible any other rotational movement, and also translational movement, between the adjacent hexagonal sensor holders. As shown, sensor holder 2a is provided with pairs of arms 8 along each of the six sides of sensor holder 2a.

[0023] Turning to sensor holders 2b and 2c, these are provided along some or all of the sides of the bottom plate 10 with hooks 12 which are adapted to receive and retain an elastic band 14; this holds the adjacent sensor holders 2b, 2c to restrict them in moving apart beyond a certain amount, but allows a complete 6 degrees of freedom of relative movement otherwise. As shown, sensor holder 2c is provided with clips 12 along each of the six sides of sensor holder 2c. whereas sensor holder 2b has a mixture of sides with either pairs of arms 8 or clips 12.

[0024] Figure 2a shows the sensor holder 2a of Figure 1 in greater detail, and Figure 2b shows sensor holder 2c of Figure 1 in greater detail. Figure 2c shows another form of sensor holder 2d which is similar to sensor holder 2a in that it has pairs of arms 8 along some sides of the base plate 10 for linking with adjacent sensor holders, but along other sides of the base plate it has a flat extension plate 16 having an eyelet or opening therethrough 18 for receiving a strap (not shown) to hold the array of sensor holders to a patient. Sensor holders 2d would usually be employed at the edges of the array to hold it as it is shaped into a conformal mat around the patient's head or body. Figures 3a and 3b show a helmet for MEG in accordance with the invention laid on a flat surface for assembly of the array, and / or for the insertion into / release from the sensor holders 2 of bio magnetic sensors S. Figure 3a shows the sensor holders 2 without any bio magnetic sensors fitted, and Figure 3b shows the sensor holders 2 with bio magnetic sensors fitted - the apertures 20 in bottom plates 10 are visible in Figure 3a and hidden by the sensors S in Figure 3b. In both drawings, there are two sensor holders 2d shown at the sides of the helmet. The anatomy of a human patient may be defined by three orthogonal planes:

[0025] 1. a sagittal (or longitudinal) plane SP which divides the body into right and left parts, and extends forwardly F, rearwardly R and vertically relative to the patient,

[0026] 2. a coronal (or frontal) plane CP that divides the body into front and rear parts, and extends to the left Lt, the right Rt and vertically relative to the patient, and

[0027] 3. a horizontal, axial or transverse plane (not shown) which divides the body into top and bottom parts, and extends forwardly F, rearwardly R and to the left Lt and the right Rt relative to the patient.

[0028] The helmet in Figures 3a and 3b is assembled by connecting the sensor holders 2 in the desired pattern on a flat surface by linking adjacent sensor holders 2 by their pairs of arms 8, or by inserting elastic bands 14 between the clips 12 (for clarity the drawings show only pairs of arms between some of the adjacent sensor holders 2, the interstices between some adjacent sensor holders 2 are shown as empty: some or all of these empty interstices may have linkages formed with elastic bands 14, as shown in Figure 1). Sensors are inserted into the required sensor holders 2 by pushing them into a sensor holder (into the plane of the drawing). The helmet with sensors S inserted (Figure 3b) is placed with its geometric centre on the crown of a patient's head, and folded down along the axes in the sagittal and coronal planes SP, CP; this will bring the sides of the helmet down around the side of the patient's head, so that a strap can be attached to the eyelets in sensor holders 2d to go under the patient's chin. The front part of the helmet (to the right in the drawings) will fold down over the patient's forehead and the two "wings" of the front part of the helmet extend the patient's temples and the two larger "wings" on either side at the rear of the helmet fold down over the sides of the patient's head and extend forwardly; it will be appreciated that, in adopting the three dimensional shape to become a conformal mat, this will bring sensor holders in the two frontal "wings" closer to sensor holders in the larger, rear "wings", and some or all of these can be connected by elastic bands, thus holding the helmet snugly against the patient's skull.

[0029] It will of course be understood that many variations may be made to the abovedescribed embodiment without departing from the scope of the present invention. For example, we have described how the sensor holders may be formed of a single plastics material, which must be rigid enough to hold the sensor securely yet resilient enough for the sensor retaining legs to flex to hold the sensor releasably, but it will be understood that the sensor retaining legs might be made of a resilient material and mounted to the remaining elements of the sensor holder made of a different, more rigid plastics material. In the drawings, bottom plate 10 is shown as either hexagonal or rectangular, but it could be of any other shape provided it performs the functions of allowing the requisite degree of freedom of movement between adjacent sensor holders, and of retaining the bio magnetic sensor within the sensor holder whilst maximising the size of the aperture through which the bio magnetic field can be sensed. The drawings show adjacent sensor holders connected by a single elastic band, but more bands may be used between adjacent sensor holder, and the bands may be of different sizes, so that there may be an interlinking which has different elasticity in some degrees of movement, and / or so that an interlinking may be provided between sensor holders which are spaced apart from one another. It should be understood that the numbers and dispositions of pairs of arms 8 and clips 12 shown is illustrative only; the number and disposition can vary in any possible combination. The helmet shown in Figure 3b is shown with all of the sensor holders having a bio magnetic sensor therein, but sensors may be provided in only some of the sensor holders making up the array in applications where bio magnetic measurements are required in some locations of the patient but not in other ones which are underneath the array of sensor holders. The conformal mat can be made up in any shape by linking sensor holders together in a suitable tessellation before this is curved into shape a s a conformal mat. The assembly and fitting of a conformal mat to a patient has been described above, it should be understood that once fitted to a patient, bio magnetic sensors can be removed and replaced easily as required without necessitating removal of the conformal mat from the patient. The invention has been described in relation to a patient; it should be understood that this encompasses both humans and animals. 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.

Claims

CLAIMS1. A bio magnetic measuring apparatus adapted to be placed in contact with the surface of a patient's body or head and to conform to the shape thereof, the apparatus comprising an array formed of a plurality of bio magnetic sensor holders, each sensor holder being adapted to hold a bio magnetic sensor releasably within the sensor holder and linked to at least three adjoining sensor holders along common, predominantly linear edges, in which at least some of the links between at least some of the adjoining sensor holders restrict these adjoining sensor holders to move freely relative to one another with only one degree of rotational freedom about an axis parallel to the common, predominantly linear edges and between limits.

2. A bio magnetic measuring apparatus according to Claim 1, wherein the rotational freedom about the axis parallel to the common, predominantly linear edges comprises a range of rotation including one of: less than 125-degrees, less than 90-degrees, less than 60-degrees, or3. less than 30-degrees. A bio magnetic measuring apparatus according to Claim 1 or 2, in which the links allowing at least one degree of rotational freedom are curved arms extending outwardly from the common, predominantly linear edges and shaped so as to interlink.

4. A bio magnetic measuring apparatus according to Claim 3, in which the curved arms are provided in pairs on each predominantly linear edge.

5. A bio magnetic measuring apparatus according to Claim 1, 2 , 3 or 4, in which at least some of the links between at least some of the adjoining sensor holders allow these adjoining sensor holders to move relative to one another with six degrees of freedom.

6. A bio magnetic measuring apparatus according to Claim 5, in which the links allowing six degrees of freedom are elastic bands.

7. A bio magnetic measuring apparatus according to any preceding claim, in which the bio magnetic sensor holders have predominantly the same geometric shape as seen in the direction they contact the patient.

8. A bio magnetic measuring apparatus according to Claim 7, in which the shape is hexagonal.

9. A bio magnetic measuring apparatus according to any preceding claim, in which at least two of the sensor holders have an eyelet for attaching a strap.

10. A bio magnetic measuring apparatus according to any preceding claim, in which the sensor holders have legs extending in use away from the surface of the patient which are adapted to guide a bio magnetic sensor as it is placed into the sensor holder.

11. A bio magnetic measuring apparatus according to any preceding claim, in which the sensor holders have legs extending in use away from the surface of the patient which are resilient and adapted to receive and to hold a bio magnetic sensor in the sensor holder in a snap fit arrangement.

12. A bio magnetic measuring apparatus according to any preceding claim, in which the sensor holders are integrally formed in one piece of a plastics material.

13. A kit for a bio magnetic measuring apparatus comprising a plurality of sensor holders according to any preceding claim, and a plurality of bio magnetic sensors.

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