APPARATUS FOR MEASURING A BIOMAGNETIC FIELD

Abstract

A biomagnetic field measuring apparatus enabling reliable biomagnetic field measurements in clinical practice, having a plurality of magnetic field sensors being arranged in an array in a sensor plane, including a plurality of first magnetic field sensors being designed and configured to measure a first component of the magnetic field, a plurality of second magnetic field sensors being designed and configured to measure a second component of the magnetic field, and a plurality of third magnetic field sensors being designed and configured to measure a third component of the magnetic field, the first, second and third components of the magnetic field being orthogonal to each other. Viewed perpendicular to the sensor plane, the first magnetic field sensors and the second magnetic field sensors are arranged essentially centrally and the third magnetic field sensors are arranged essentially around the first and second magnetic field sensors.

Claims

1. Apparatus for measuring a biomagnetic field comprising a plurality of magnetic field sensors (3, 4, 5) being arranged in an array (1) in a sensor plane, the plurality of magnetic field sensors (3, 4, 5) consisting of a plurality of first magnetic field sensors (4) being designed and configured to measure a first component of the magnetic field, a plurality of second magnetic field sensors (5) being designed and configured to measure a second component of the magnetic field, and a plurality of third magnetic field sensors (3) being designed and configured to measure a third component of the magnetic field, the first, second and third components of the magnetic field being orthogonal to each other, and wherein, viewed from a direction perpendicular to the sensor plane, the first magnetic field sensors (4) and the second magnetic field sensors (5) are arranged essentially centrally and the third magnetic field sensors (3) are arranged essentially around the first and second magnetic field sensors (4, 5).

2. The biomagnetic field measuring apparatus according to claim 1, wherein the number of first magnetic field sensors (4) equals the number of second magnetic field sensors (5).

3. The biomagnetic field measuring apparatus according to claim 2, wherein each of the first magnetic field sensors (4) is spatially associated with a second magnetic field sensor (5), such that both measure the magnetic field components at essentially the same location of a source.

4. The biomagnetic field measuring apparatus according to one of the preceding claims claim 1, wherein the array (1) of magnetic field sensors (3, 4, 5) has, viewed from a direction perpendicular to the sensor plane, an essentially circular, elliptical, rectangular or polygonal shape.

5. The biomagnetic field measuring apparatus according to claim 4, wherein (a) the array (1) of magnetic field sensors (3, 4, 5) is, viewed from a direction perpendicular to the sensor plane, essentially circular, (b) the first magnetic field sensors (4) and the second magnetic field sensors (5) are arranged centrally in an essentially circular region (6) of the array, and (c) the third magnetic field sensors (3) are arranged essentially in a circular region (7) around the first and second magnetic field sensors (4, 5).

6. The biomagnetic field measuring apparatus according to claim 5, comprising 64 magnetic field sensors (3, 4, 5), wherein 24 first magnetic field sensors (4) and 24 second magnetic field sensors (5) are arranged centrally in an essentially circular portion of the array, and 16 third magnetic field sensors (3) are arranged essentially in a circular region (7) around the circular region (6) containing the first magnetic field sensors (4) and the second magnetic field sensors (5).

7. The biomagnetic field measuring apparatus according to one of the preceding claims claim 1, wherein the biomagnetic field measuring apparatus is a magnetocardiograph.

8. Apparatus for measuring a biomagnetic field comprising a plurality of magnetic field sensors (3, 4, 5) being arranged in an array (1) in a sensor plane, the plurality of magnetic field sensors (3, 4, 5) comprising a plurality of first magnetic field sensors (4) being designed and configured to measure a first component of the magnetic field, a plurality of second magnetic field sensors (5) being designed and configured to measure a second component of the magnetic field, and a plurality of third magnetic field sensors (3) being designed and configured to measure a third component of the magnetic field, the first, second and third components of the magnetic field being orthogonal to each other, and wherein, viewed from a direction perpendicular to the sensor plane, the first magnetic field sensors (4) and the second magnetic field sensors (5) are arranged essentially centrally and the third magnetic field sensors (3) are arranged essentially around the first and second magnetic field sensors (4, 5).

Description

[0023] In the following, the invention is described in more detail by way of an example and the attached figures for illustration purposes only.

[0024] FIG. 1. Schematic illustration of a sensor arrangement according to the prior art.

[0025] FIG. 2. Schematic illustration of a sensor arrangement according to an embodiment of the invention.

[0026] FIGS. 3 and 4. Schematic illustration of examples of comparative sensor arrangements (not according to the invention).

[0027] FIG. 1 shows a sensor arrangement according to a prior art 64-channel biomagnetic field measuring apparatus. Circles with dotted outlines denoted with the reference numeral 2 represent measuring points on a magnetic source, here the heart. Magnetic field sensors 3 measuring the z-component of the biomagnetic field generated by the heart at the measuring points are arranged in an essentially circular array 1. All of the 64 magnetic field sensors 3 of the prior art apparatus are of one type, i.e. a type measuring only the z-component of the biomagnetic field.

[0028] FIG. 2 shows a sensor arrangement according to an embodiment of the invention for a 64-channel biomagnetic field measuring apparatus, in this case an MCG. For comparison, the 64 measuring points 2 of the prior art apparatus of FIG. 1 are also depicted here. 24 first magnetic field sensors 4 and 24 second magnetic field sensors 5 are arranged in an essentially circular region 6 of the array 1. Each of the 24 first magnetic field sensors 4 is associated with a corresponding second magnetic field sensor 5, such that sensor pairs thus formed measure the x- and y-components of the biomagnetic field at the same measuring point. 16 third magnetic field sensors 3 measuring the z-component of the biomagnetic field are arranged in an essentially circular or annular region 7 around or in the periphery of the first and second magnetic field sensors 4, 5.

[0029] FIGS. 3 and 4 show two other sensor configurations (not according to the invention) used for the purpose of comparison. In FIG. 3 a sensor configuration is shown in which all sensors are distributed over the cross-section of the central circular region 6. The arrangement is composed of 4 sensors measuring only the z-component of the magnetic field at the corners of a quadrangular area within the central circular region 6, and 320 sensors measuring the x-, y- and z-components at corresponding 20 measuring points, respectively. FIG. 4 depicts an arrangement, in which each of the 64 measuring points 2 is associated with one of 64 magnetic field sensos, 18 of the 64 sensors measuring the x-component of the magnetic field, 17 sensors measuring the y-component of the magnetic field and 29 sensors measuring the z-component of the magnetic field.

[0030] An MCG having a sensor configuration according to the embodiment of the invention shown in FIG. 2 was compared with MCGs set-up with a prior art sensor configuration according to the one depicted in FIG. 1 and with MCGs set-up with the sensor configurations of FIGS. 3 and 4, respectively. Small changes of the current dipole pattern on the frontal area of the heart were simulated. The prior art 64-channel MCG calculated 298 dipoles on the heart.

[0031] The results showed that the sensor configuration of the invention (FIG. 2) and the configuration according to FIG. 3 are superior to the configurations according to the prior art (FIG. 1) and according to FIG. 4 in order to explain the small changes.

[0032] Further, the inverse solution performance of the different sensor arrangements was evaluated. A forward model was calculated from a given source and the inverse solution was calculated from the measured magnetic field data. It could be shown that, by comparing the original source and the inverse solution, that the sensor configuration according to the invention (FIG. 2) and the sensor configuration according to FIG. 3 have a better inverse solution performance than the prior art sensor configuration and the sensor configuration according to FIG. 4.

[0033] The robustness of the compared sensor configurations in view of an offset from the heart center was evaluated. For this purpose a position offset in x-direction (right hand to left hand) was simulated. It could be shown that the prior art sensor configuration has a bigger anle error than the sensor configuration according to the invention and the sensor configuration according to FIG. 4.

[0034] In summary, it was shown that an MCG having a sensor configuration of the invention according to FIG. 2 is superior in view of sensitivity and robustness compared to the prior art.