JPH04109929A - Method for measuring living body magnetism - Google Patents

Abstract

PURPOSE:To grasp positional relation and measuring direction of a magnetism measuring point to a testee easily and correctly in measuring a magnetism by arranging a Dewar containing a SQUID senser and a subject testee taking a light beam for reference, and measuring the magnetism at the subject testee by the SQUID senser. CONSTITUTION:Cross beams 11, 21, 31 are projected to a subject testee 4 and a Dewar 51 using three beam generation sources 1, 2, 3. Cross beam lines 12, 22 appear in the surface of the subject testee and the Dewar 51 by projection of the light beams, and a three-dimensional coordinates system (X, Y, Z) for a head part is visualized. In the meanwhile, where a 1-channel SQUID senser is contained in the Dewar 51, marks are put at positions projected in the surface of the Dewar 51 in the directions of X-, Y-, Z-axes. The Dewar 51 is moved to let the beam lines coincide with the marks. When the Z-axis of the head part coincides with the senser axis, a distance L from the orgin of the head coordinates system to the senser is measured.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a biomagnetic measurement method for estimating active areas of the brain by measuring magnetic fields generated in the human brain.

[Conventional technology]

Traditionally, SQU has been used as a sensor to measure minute magnetism.
ID (Superconducting Quant
um InterferenceDevice (superconducting quantum interference device) sensors are known. Therefore, this SQU ID sensor is used to measure minute magnetism generated from the human body. This SQUID needs to be cooled with liquid helium to maintain its superconducting state, and is usually immersed in liquid helium filled in a container called a dewar. By using this SQUID sensor, the magnetic field of the living body is measured at a large number of measurement points, and the positional relationship between the magnetic field measurement points and the living body is determined. On the other hand, M
Data representing the internal structure of a living body is obtained using a tomography device such as an RI device or an X-ray CT device, and then an appropriate model that approximates the living body is created. Then, assume the positions, sizes, and directions of multiple current dipoles for that model, and select a current dipole that minimizes the difference between the magnetic field distribution created by the current dipole group at the measurement point of the magnetic field and the measurement data above. Find the group. The positions, sizes, and directions of the current dipole groups thus determined are displayed on both MR images. Therefore, in such biomagnetic measurement, the SQUI is
It is very important to accurately grasp the position and direction in which magnetism was measured by applying the D sensor. Therefore, conventionally, for example, a three-dimensional coordinate measuring device using a three-dimensional magnetic field has been used to determine the relationship between the living body and the measurement position and direction (see Japanese Patent Application No. 2-50703). This three-dimensional coordinate measuring device uses three
A 3D magnetic field is generated, and a receiver is placed in the 3D magnetic field to detect the magnetic field in each direction, thereby measuring the 3D position of the receiver in the 3D magnetic field. It is. When using this, the receiver is placed on the surface skin of the living body and the feature points of the living body are input, and the receiver is placed on several places on the surface of the dewar to measure the internal SQU.
The position of the ID sensor coil is input.

[Problem to be solved by the invention]

However, a three-dimensional coordinate measuring device places a receiver in a three-dimensional magnetic field generated by a magnetic field generator, and inputs the three-dimensional position of the receiver in the three-dimensional magnetic field. Therefore, when using this method, it is necessary to specify the specific positions of the living body and dewar using the receiver, and there is a problem in that it is not easy to input the predetermined positions accurately. In other words, the position is input by placing the receiver on the skin at a position corresponding to a characteristic point of a living body that is clearly seen in a CT image or MR image. It is not easy to place the values, and errors are likely to occur. An object of the present invention is to provide a biomagnetic measurement method that is improved so that magnetic measurement can be performed while easily and accurately grasping the position of a magnetic measurement point and its positional relationship with the living body in the measurement direction. .

[Means to solve the problem]

In order to achieve the above object, in the biomagnetic measurement method according to the present invention, a dewar in which a 5QUID sensor is housed and a subject are aligned with a light beam as a reference, and the SQUID sensor is used to detect the subject. Its feature is that it measures magnetism.

[For production]

The dewar containing the SQUID sensor and the subject are
Align with the light beam as a reference. By aligning these, the subject and the SQUID sensor in the dewar have a standard positional relationship. Therefore, the position and direction of the magnetic measurement point by the SQUID sensor with respect to the subject can be accurately determined from the reference positional relationship.

【Example】

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, a light beam (laser beam) is projected and the dewar 51 is aligned with respect to the subject 4 using the beam line (projection line) as a reference. That is, three beam generation sources 1.2.3 are used, and cross beams (cross-shaped light beams) 11.21.
31 is projected onto the subject 4 and the dewar 51. Subject 4
Marks are placed on the head skin at three points A, B, and C to determine the three-dimensional coordinates of the head, and a cross beam 11 is projected along the X axis passing through point A. , a cross beam 21 is projected along the Y axis passing through point B, and a cross beam 31 is projected along the Y axis passing through point 0. By projecting such a light beam, the subject 4 and the dewar 51
There is a cross-shaped beam line (projection line) 12.2 on the surface of
2 will appear, and the three-dimensional coordinate system (X, Y, Z) of the head will be visualized. On the other hand, assuming that the dewar 51 has a built-in one-channel SQUID sensor, mark the position of the sensor (coil) projected on the surface of the dewar 51 in the x, y, and z axis directions. (Dots and lines) are attached. Then, the dewar 51 is moved so that the beam line matches the mark. As a result, the Z-axis of the head and the axis of the sensor coincide. At this time, the distance from the origin of the head coordinate system to the sensor is measured. In this way, the position (0, 0, L) of the sensor in the head coordinate system (X, Y, Z') is determined. The magnetic field measurement direction of the SQUID sensor is the Z-axis origin direction. The dewar 51 is held by, for example, a hanging system. After such positioning is completed, magnetic measurement is performed using the SQUID sensor. At this time, the positional relationship of the measurement point with respect to the subject 4 is such that the subject 4 and the dewar 51 are aligned. Therefore, it is known exactly. Therefore, in cases where magnetic measurement at one measurement point using a one-channel SQUID sensor is sufficient, or when many channels of SQUID sensors are housed in the dewar 51, the SQUID sensor of many channels can be measured without moving the dewar 51.
This is effective when only magnetic measurements at fixed points on multiple sides using QUID sensors are required. When moving the dewar 51 to perform magnetic measurements at a larger number of measurement points, a transmitter 81 as shown in FIGS. 2 and 3 is used.
A three-dimensional coordinate measuring device 8 including a receiver 82 and a receiver 82 is used. When a three-dimensional magnetic field is generated from the transmitter 81 and the receiver 82 is placed in the magnetic field, the receiver 82 receives the magnetic field, and the received signal is sent to the three-dimensional coordinate measuring device 8. The position of the receiver 82 in the three-dimensional coordinate system based on the three-dimensional magnetic field from the transmitter 81 can be determined. As this type of three-dimensional coordinate measuring device, "3-dimensional digitizer" (trade name) manufactured by Nissho Electronics Co., Ltd., etc. can be used. Before performing the positioning as described above (or without shifting the position after the positioning), the subject 4 is made to wear glasses 41 with non-magnetic rubber bands. The receiver 82 described above is attached to the glasses 41. On the other hand, a support rod 52 is provided in advance on the dewar 51, and a transmitter 81 is attached to the tip of the support rod 52. When the dewar 51 is arranged so that the SQUID sensor is aligned in the coordinate system of the subject 4, the receiver 82 in the coordinate system of the transmitter 81 is
If the position is determined, the positional relationship between the transmitter 81 and the receiver 82 will be determined as the reference positional relationship. Then, as shown in FIG. 2, while moving the dewar 51 relative to the subject 4, the dewar 51 is placed at each measurement point.
1 and measure the magnetism of the subject 4. At this time, at each measurement point, the receiver 82 with respect to the coordinate system of the transmitter 81
If you find the position of and know the displacement from the reference position above,
It can be seen where the measurement point by the SQUID sensor is located in the coordinate system of the subject 4. That is, in the system configuration shown in FIG. 3, the SQUID sensor 5 is connected to the data collection device 6, and when the collected magnetic measurement data is taken into the computer 7, the transmitter 81 and the receiver 82 are connected. A three-dimensional coordinate measuring device 8 having
Therefore, the position of the magnetic measurement point in the coordinate system of subject 4 is 1.
The direction will be input. Apart from the magnetic measurement by the SQUID sensor 5 and the measurement of the position and direction of the measurement point, the MHI device 9 (
Alternatively, a tomographic image of the head of the subject 4 is taken using an XIICT device (not shown). This photograph may be taken before or after the magnetic measurement described above, and this M
Image data obtained by the HI device 9 is sent to the computer 7 online or offline. At the time of this photographing, markers are attached to three points A, B, and C for determining the coordinates of the head of the subject 4, which are visualized by the MR device 9. In this way, an MR tomographic image in which an index image 42 as shown in FIG. 4A appears can be obtained. This allows the positional relationship of the head coordinate system in the tomographic image obtained by the MHI device 9 to be known. The computer 7 creates an appropriate approximate model of the head from this MR tomographic image data and calculates the current dipole. In other words, the size, position, and direction of the current dipole are assumed on the head approximation model, and the square error between the magnetic flux density distribution created by the assumed current dipole on the approximation model and the measured magnetic flux density distribution is The magnitude, position, and direction of this current dipole are calculated by finding the magnitude, position, and direction of the current dipole that minimizes it. The current dipoles obtained in this way are, for example, in Fig. 4A, B,
It is displayed as an appropriate mark such as an arrow on the MR tomographic image as shown in C. This image is displayed on a display device 71 connected to the computer 7 and recorded on a recording device 72. This figure 4 A, B. C illustrates the current dipole generated by midline nerve stimulation of the wrist. In addition, although the case where the magnetism measurement of the head of the subject 4 is performed is explained above as an example, the present invention is not limited to such magnetoencephalography measurement, but can also be applied to 6 magnetism measurement as shown in FIG. . In the case of this 6-magnetic measurement, 3
As points A, B, and C, two points on the body rs and one point on the body surface are determined, and they are positioned so that the cross beam of light from the beam source 1.2.3 is irradiated, and then
The dewar 51 is aligned at a reference position using the light beam as a reference. When moving the dewar 51, the transmitter 81 and receiver 82 of the three-dimensional coordinate measuring device 8 are attached to the dewar 51 and the subject 4 to determine the reference positional relationship, and at the same time While measuring the positional relationship, the SQUID sensor 5 in the dewar 51 at each measurement point
The procedure for performing magnetometry is the same as in the case of magnetoencephalography measurement. In this case, since the body moves due to breathing exercise, it is desirable to attach the transmitter 81 or the receiver 82 to the non-magnetic bed.

【Effect of the invention】

According to the biomagnetic measurement method of the present invention, the three-dimensional coordinate system of the subject can be visualized by projecting a light beam onto the subject, and by aligning the SQUID sensor accordingly, The subject and the SQUID sensor can be placed in a standard positional relationship. Therefore, if magnetic measurement is performed using the SQU ID sensor in this state, the magnetic measurement can be performed at a measurement position and direction that can be accurately determined from the reference positional relationship. That is, when performing magnetic measurement of a subject using the 5QUID sensor, it is possible to easily detect where the measurement point is located in the subject's coordinate system with high accuracy. Further, dewar setting for the subject is easier than using a dewar holding mechanism that moves in a special manner or providing a dewar holding mechanism with a coordinate system. Since the positional relationship of the magnetic measurement data with respect to the subject is accurate, the estimation accuracy of the current dipole can be improved. Further, it can be applied to both magnetoencephalography measurement that measures the magnetic field of the head and hexamagnetic measurement that measures the magnetic field of the chest.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, and is a schematic perspective view showing how the head of a subject and a dewar are aligned with respect to a light beam when performing magnetoencephalography measurement; Fig. 2 is a schematic diagram showing how magnetic measurement is performed while moving the dewar with respect to the subject's head, Fig. 3 is a block diagram showing an example of the system configuration used in this example, and Fig. 4 is FIG. 5 is a diagram showing an example of an MR tomographic image, and is related to another embodiment in the case of 6-magnetic measurement, and is a schematic diagram showing how to align the chest of the subject and the dewar with reference to the light beam. FIG. l, 2.3... Beam source, 11.21.31...
・Cross beam, 12.22...beam line, 4・
...Subject, 41...Glasses with non-magnetic rubber band,
42... Index image, 5... SQUID sensor, 51...
...Dewar-152...Support rod, 6...Data collection device, 7...Computer, 71...Display device, 7
2... Recording device, 8... Three-dimensional coordinate measuring device, 81
... transmitter, 82 ... receiver, 9 ... MHI device.

Claims (1)

[Claims] (1) A biomagnetic measurement method characterized in that a dewar containing a SQUID sensor and a subject are aligned with a light beam as a reference, and the magnetism of the subject is measured by the SQUID sensor.