JPH04226630A - Biomagnetism measuring instrument - Google Patents

Abstract

PURPOSE:To make magnetism measurement while easily and exactly recognizing the positional relation of the position and measurement direction of a magnetism measurement point with a living body by pointing a certain point by using a visible light beam. and using a three-dimensional coordinate input device inputting this point. CONSTITUTION:A receiver 42 is mounted to a frame 44 and two lens holding bases 45 are provided on this frame 44. Lens barrels 46 are respectively mounted to these bases. Optical fibers 47 are respectively connected to these lens barrels 46. The other ends of two pieces of optical fibers 47 are connected to light sources which generate visible light of respectively different wavelengths. The positions and directions of the two lens barrels 46 are so set that the two light beams projected from the two lens barrels 46 are focused to intersect at a specific one point. The specific point is directed at the intersected point of the visualized light beams, by which the three-dimensional coordinates of this point are inputted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biomagnetic measuring device for estimating active areas of a human brain or heart by measuring magnetic fields generated in the human brain or heart.

0002

[Prior Art] Conventionally, SQUID (Superconducting) has been used as a sensor for measuring minute magnetism.
Quantum InterferenceDevi
ce (superconducting quantum interference device) sensors are known. 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.

[0003] By using this SQUID sensor, minute magnetism generated from the human body can be measured at a large number of measurement points. On the other hand, the internal structure of the human body can be seen using MRI
This can be determined by using a tomography device such as an X-ray CT device or an X-ray CT device. Therefore, if the positional relationship between the magnetic field measurement point and the living body is known, it becomes possible to estimate from this information where in the human body the current is generated. Specifically, we created an appropriate model that approximates the living body from data representing the internal structure, and then determined the position, size, and size of multiple current dipoles for that model.
Assuming the direction, a current dipole group is found 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 above measurement data. By displaying the positions, sizes, and directions of the current dipole groups thus determined on an MR image or the like, it is possible to know the distribution of active currents inside the human body.

[0004] In such biomagnetic measurement, the SQU is
It is very important to accurately understand in which position and direction magnetic field was measured by applying the ID sensor. Living body and S
In order to understand the positional relationship with the QUID sensor, it has conventionally been considered to provide a position/direction detection mechanism for both the biological body holding device and the SQUID sensor holding device (Japanese Patent Laid-Open No. 2-116767). .

It has also been considered to obtain the relationship between a living body and a measurement position/direction using a three-dimensional coordinate input device using a three-dimensional magnetic field (see Japanese Patent Application No. 2-50703). This three-dimensional coordinate input device is known as the McDonnell Douglas "3SPACE" (trademark) three-dimensional digitizer, which has been commercialized, and includes a transmitter that generates a magnetic field and a receiver that receives the magnetic field. and use. Both the transmitter and receiver have three orthogonal coils. mutually distinguishable from the transmitter (e.g. different frequencies)
By generating a three-dimensional magnetic field, placing the receiver in the three-dimensional magnetic field, and detecting the magnetic field in each direction using each coil, the three-dimensional position of the receiver in the three-dimensional magnetic field can be determined. and to measure the angular direction.

[0006] When using such a three-dimensional coordinate input device, the three-dimensional coordinates of a feature point on the living body are input by pointing at a feature point on the surface skin of the living body with the tip of a stylus of a slylus type receiver that can specify points. In addition, the stylus tip is applied to several locations on the surface of the dewar to input the three-dimensional position of the SQUID sensor coil inside the stylus.

[0007]

However, in all conventional methods, there is a problem in that it is difficult to accurately grasp the positional relationship between the living body and the SQUID sensor.

In other words, when both the biological support device and the SQUID sensor holding device are provided with a position/direction detection mechanism, the biological body is not held in the biological support device in an accurate positional relationship, but the position of the biological support device - This is because even if the direction is detected, the position and direction of the living body itself cannot always be accurately determined. In addition, in this case, the biological support device and S
Since both of the QUID sensor holding devices are provided with a position/direction detection mechanism, a large-scale mechanism is required, which poses the problem of not being simple and expensive.

[0009] When inputting a point by applying the tip of a stylus type receiver to the skin of a living body, it is ambiguous whether the skin is a soft tissue and dents when the tip of the stylus is applied, so it is unclear whether it is necessarily pointing to a feature point. It is difficult to match designated points with biological feature points, which causes measurement errors.

In view of the above, the present invention has been improved so that magnetic measurement can be performed by easily and accurately grasping the positional relationship of the position and measurement direction of the magnetic measurement point with respect to the living body.
The purpose is to provide a biomagnetic measurement device.

[0011]

[Means for Solving the Problems] In order to achieve the above object, the biomagnetic measuring device according to the present invention does not point to a feature point with the tip of a stylus, but points to a certain point using a visible light beam. Enter that point by 3
It is characterized by the use of a dimensional coordinate input device. Since the three-dimensional coordinates of a biological feature point are input by pointing at the biological feature point using visible light, the soft skin surface will not be indented, and accurate three-dimensional coordinates of the biological feature point can be input easily. As a result, the accuracy of biomagnetic measurement itself improves.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. In this embodiment, as shown in FIG. 1, biomagnetic measurement is performed using the SQUID sensor in the Dewar 11 while detecting the positional relationship between the subject's head and the Dewar 11. Transmitter 41, receiver 42, 4
3 constitutes a three-dimensional coordinate input device. Each of these has three coils orthogonal to each other and is connected to a control and signal processing device (not shown). From the transmitter 41, mutually distinguishable (for example, changing frequency, time sharing) 3
By generating a dimensional magnetic field and detecting the magnetic field in each direction by the coils of the receivers 42 and 43 placed in the 3-dimensional magnetic field, the transmitter 41 The three-dimensional positions and angular directions of the receivers 42 and 43 in three-dimensional coordinates are measured.

The receiver 42 is attached to a frame 44, and the frame 44 has two lens holders 45.
are provided, and a lens barrel 46 is attached to each of them. The optical fiber 4 is connected to these lens barrels 46.
7 are connected to each other. The other ends of the two optical fibers 47 are each connected to a light source that generates visible light of different wavelengths (colors), and the two light beams emitted from the two lens barrels 46 are focused at one specific point. The positions and directions of the two lens barrels 46 are set so that they intersect at. By pointing to a specific point at the intersection of the visualized light beams, the three-dimensional coordinates of that point are input.

That is, with the transmitter 41 fixed at an appropriate position on the surface of the dewar 11, the frame 44 is moved so that the intersection of the light beams points to a characteristic point on the head. As a result, the three-dimensional coordinates of feature points on the head, such as the base of the nose and the roots of the left and right ears, in the three-dimensional coordinate system of the transmitter 41 are input. Furthermore, the transmitter 4 is moved by moving the frame 44 so that the intersection points of the light beams point to a plurality of surface positions related to the position and direction of the SQUID sensor coil built in the Dewar 11.
Input the three-dimensional coordinates and direction of the SQUID sensor coil in the three-dimensional coordinate system of 1. In this way, the magnetic measurement points and measurement direction for the head can be input using the feature points of the head as a reference.

Next, we will explain in detail how the coordinates of the point indicated by the intersection of the light beams in the three-dimensional coordinate system of the transmitter 41 are determined. The transmitter 41, receivers 42, and 43 each have three orthogonal coils as described above, and when one coil of the transmitter 41 is excited, the receiver 42 (or four
3) A voltage is induced in each of the three coils. These voltages will depend on the distance from the transmitter 41 and the angular orientation of the receiver 42 (or 43). Therefore, the receiver 42 (or 4
3) coordinates and direction angle (Azimuth, Elevat
ion, Roll) are calculated.

[0016] Here, the transmitter 41 is fixed on a desk or the like, and the frame 44 is also placed on the desk. Then, the intersection of the light beams is made to point to a certain point Q in space. At this time, the coordinates of the receiver 42 in the transmitter coordinate system (O;
b, c), the direction angle of the receiver 42 is A, E, R, respectively.
Also, the coordinates of point Q in the receiver coordinate system (P; U, V, W) whose origin is the center P of the three-axis coil of the receiver 42 are (
α, β, γ), then the coordinates of point Q in the transmitter coordinate system (
X, Y, Z) is (X, Y, Z) = (a, b, c) + (
α, β, γ)・T1・T2・T3. however,

[Math 1] It is.

Therefore, by moving the frame 44 so that the intersection points of the light beams point to the same point Q and performing the measurement twice, six equations for the unknowns X, Y, Z, α, β, and γ can be obtained. By solving this, α, β, and γ can be found. In this way, we know where the intersection of the light beams is located in the coordinate system of the receiver 42, so if we point to this point, we can use the coordinates and direction angle of the receiver 42 in the coordinate system of the transmitter 41 at that time. , the transmitter 4 of the pointed point
1 coordinate system can be input.

Then, since the head or the Dewar 11 is moved and magnetic measurements are performed at a large number of measurement points, a receiver 43 is attached to the surface of the head in order to capture changes in the positional relationship between the head and the Dewar 11. . Due to the variation in the position and direction of the receiver 43 within the three-dimensional coordinate system of the transmitter 41,
The positional relationship of magnetic measurement points and directions with respect to the head by the SQUID sensor built into the dewar 11 can be captured.

FIG. 2 shows the entire system of the biomagnetic measuring device. In this figure, magnetic measurement is performed using the SQUID sensor 1 while inputting measurement points and directions for the head using the three-dimensional coordinate input device 4 as described above. The measurement data is collected by the data collection device 2 and then imported into the computer 3. As a result, magnetic flux density distribution data that is positionally related to the living body is imported into the computer 3.

On the other hand, a tomographic image of the subject's head is taken by the MRI device 5 (or an X-ray CT device, not shown). This photographing may be performed before or after the magnetic measurement described above, and the obtained image data is sent to the computer 3 online or offline. At the time of this imaging, an index that can be seen in an MR image (or an X-ray CT image, etc.) is attached to the head feature points. The image data in which the index image thus obtained appears and the data of the head feature points inputted by the three-dimensional coordinate input device are compared in the computer 3. Thereby, it is possible to accurately know from which position and direction on the tomographic image the magnetic field was measured, and it is possible to accurately correlate the magnetic flux density distribution data with the tomographic image data in terms of position.

The computer 3 creates an appropriate approximate model of the head from this 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 size, position, and direction of this current dipole are calculated by finding the size, position, and direction of the current dipole that minimizes it. As described above, since the measured magnetic flux density distribution is accurately positioned with respect to the approximate model, the accuracy of calculating the current dipole can be improved. The current dipole thus calculated is displayed, for example, as an arrow, and this arrow is displayed on the display device 31 connected to the computer 3 while being superimposed on a tomographic image such as a CT image or an MR image. Further, the magnitude, position, and direction of the current dipole thus determined are recorded by the recording device 32 together with the tomographic image data.

[0022] In the above description, the case where the magnetic field of the subject's head is measured has been described as an example, but the present invention is not limited to such magnetic brain magnetic field measurement, but can also be applied to magnetocardial magnetic field measurement.

[0023]

[Effects of the Invention] As described above with respect to the embodiments, according to the biomagnetic measuring device of the present invention, the three-dimensional coordinates of a feature point of a living body can be input by pointing to the coordinates of the feature point with the intersection point of the light beam. The magnetic measurement can be performed by easily and accurately grasping the position of the magnetic measurement point and the positional relationship of the measurement direction with respect to the living body, and the accuracy of current dipole estimation is also improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention.

FIG. 2 is an overall block diagram of the same embodiment.

[Explanation of symbols]

1 SQUID sensor 11 Dewar 2
Data collection device 3
computer 31
Display device 32
Recording device 4 3
Dimensional coordinate input device 41 Transmitter 42, 43 Receiver

Claims (1)

[Claims] [Claim 1] SQUID sensor and this SQUID
A dewar that houses a sensor, a transmitter and a receiver that generate and receive a three-dimensional magnetic field attached to the dewar and the surface of a living body, respectively, and a receiver that can input a point irradiated with a light beam and that can specify a point. A biomagnetic measurement device comprising: a three-dimensional coordinate input device.