JPH10295659A - Organism activity current source displaying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge accurately and easily the region of possibility that a current source exists. SOLUTION: A current source displaying device stores by previous simulation the amount of dislocation of the position of a current source based upon the measuring magnetic field data corresponding to the degree of identicalness from the position of current source based upon the theoretical magnetic field data-S1. On the basis of the determined amount of dislocation, a circle is set whose center lies at the presumed current source and whose radius is the obtained amount of dislocation (S2 and S3), and is displayed overlapping on a tomographic image of the body part to be inspected (S4 and S5), and thereby it is possible to judge accurately and easily the region of possibility that current source exists.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biological activity current source display device for displaying the position of a biological activity current source, and more particularly to an area in which a biological activity current source may exist. The present invention relates to a biological activity current source display device.

[0002]

2. Description of the Related Art When a living body is stimulated, the polarization formed across a cell membrane is broken and a living activity current flows. This biological activity current appears in the brain and heart, and is recorded as an electroencephalogram and an electrocardiogram. The magnetic field generated by the biological activity current is recorded as a magnetoencephalogram and a magnetocardiogram.

Recently, as a device for measuring a minute magnetic field in a living body, SQUID (Superconducting Quantum Inter
Multi-channel SQUID sensor using ference device (superconducting quantum interferometer) (hereinafter referred to as "sensor")
Is being developed. In this sensor, a large number of SQUID sensors are immersed in a refrigerant such as liquid nitrogen and stored in a container called a dewar. This sensor is placed at the site of interest of the subject, for example, outside the head, and a current dipole (hereinafter, referred to as a “current source”), which is a bioactive current source generated in the brain
Can be measured non-invasively by the sensor. Based on the measured magnetic field data, the position, direction, and size of the current source generated at the site of interest of the subject are estimated. As a method of estimating the current source, there are various methods using a least square method, a minimum norm method, and the like.

The position of the current source estimated by such a method is specified by superimposing and displaying the position of the current source on a tomographic image obtained by an MRI apparatus or an X-ray CT apparatus. Can be. However, the position of the current source is estimated based on measured magnetic field data including factors such as disturbance of a surrounding magnetic field when a minute magnetic field is measured. The estimated position of the measured current source has an error with respect to the position of the theoretical current source estimated based on the theoretical magnetic field data that does not include factors such as disturbance of the magnetic field. Here, the theoretical magnetic field data refers to Bio-Savart based on the data of the position and orientation of the current source estimated based on the measured magnetic field data obtained by measuring the minute magnetic field of the current source at the site of interest of the subject. It is magnetic field data theoretically obtained by using the method.

Conventionally, this error is calculated by comparing the measured magnetic field data with
The degree of coincidence with the theoretical magnetic field data is represented by a degree of coincidence or a correlation value.

Here, the relationship between the error and the degree of coincidence will be described.
First, a current source is virtually set at a site of interest of the subject.
The distribution of the magnetic field data measured by the sensor for the magnetic field generated from the set current source is theoretically obtained. Thereby, a distribution of virtual magnetic field data from a virtually set current source is obtained. On the other hand, arbitrary noise is superimposed on the virtual magnetic field data to obtain a distribution of noise virtual magnetic field data including noise. The distribution of the noise virtual magnetic field data is shifted due to the magnitude of the noise because noise is superimposed on the virtual magnetic field data. The degree of deviation between the virtual magnetic field data and the noise virtual magnetic field data is represented by a numerical value (degree of coincidence). For example, when the level of the degree of coincidence is low, the deviation of the distribution of the noise virtual magnetic field data from the distribution of the virtual magnetic field data is large. In other words, the error between the position of the current source estimated based on the virtual magnetic field data and the position estimated based on the noise virtual magnetic field data is large.

Next, depending on the level of the degree of coincidence, the degree of deviation of the estimated current source position from the true current source position can be empirically known by simulation. . Specifically, as described above, noise is intentionally superimposed on the virtual magnetic field data. The position of the current source based on the distribution of the magnetic field data when the noise is superimposed and the position of the current source based on the distribution of the virtual magnetic field data are estimated. The position of the current source estimated at this time has an error due to the influence of noise. This error can be known quantitatively. That is, the difference between the position of the current source virtually set previously and the position estimated based on the magnetic field data on which noise is superimposed is an error. On the other hand, the matching degree at this time can also be calculated. There is a correspondence between the degree of coincidence and the error in the position of the current source. If the above simulation is executed with various noise levels, a relationship between the degree of coincidence and the current source error can be obtained.

For example, when the degree of coincidence = 90 is calculated,
The position estimated from the measured magnetic field data is
Expressed as 90% coincident with the true current source position. It is simulated in advance how much the position of the current source estimated with the degree of coincidence or correlation value is shifted from the position of the theoretical current source, as described above. As an example of the simulation, for example, S / N
When the position of the current source is estimated based on magnetic field data including noise of = 10, the coincidence at this time is 90%. In the case of this coincidence of 90%, it can be confirmed that the position of the current source is shifted by 10 mm. In this way, the amount of deviation between the position of the current source and the position of the true current source estimated based on magnetic field data including arbitrary noise is checked in advance.

FIG. 5 shows a case where the position of a current source in the brain, for example, which is a region of interest of the subject, is determined by the above-described method, and the position of the current source with respect to the tomographic image of the brain displayed on the monitor screen is specified. This will be described with reference to FIG. Monitor screen 3
0, the upper tomographic image 31 of the brain including the estimated current source
a, the rear cross-sectional image 31b, the lateral tomographic image 31c, and the degree of coincidence 33 are displayed. In addition, the estimated current source position 32 corresponds to the tomographic images 31a, 31b, 31c of the brain.
Are superimposed on each other. This tomographic image 31
By taking into account a, 31b, 31c, the current source position 32, and the degree of coincidence 33, if the current source position on the tomographic image of the brain matches the position, for example, by 90%, It can be seen that there is a possibility that a true current source position exists within a range of ± 10 mm with respect to the current source position 32.

[0010]

However, the prior art having such a structure has the following problems. For example, when the position of the measurement current source estimated based on the measurement data is displayed above the Sylvian groove of the tomographic image of the brain, if the determination is made based only on the display position of the current source on this tomographic image, the current source is It is interpreted as occurring at the top of the Sylvian groove. In this case, since it is anatomically considered to be present below the Sylvian groove, it can be seen that the position of this measurement current source is not an accurate display position. here,
Considering the degree of coincidence, for example, when the degree of coincidence is 90%, there is a possibility that the current source is located within a region of ± 10 mm from the estimated position of the current source. Guess this area on the monitor screen,
If the lower part of the Sylvian groove is included in this region, it is considered that the magnetic field measurement was performed normally because it matches the knowledge of the anatomy. As described above, it is difficult to accurately determine the region where the current source exists by considering the position of the current source, the degree of coincidence, and the correlation value displayed on the tomographic image of the region of interest of the subject.

The present invention has been made in view of such circumstances, and a living activity current source display device capable of accurately and easily determining an area where a living activity current source may exist. It is intended to provide.

[0012]

The present invention has the following configuration to achieve the above object. That is, the present invention estimates the current source at the site of interest of the subject based on the measured magnetic field data obtained by measuring the minute magnetic field generated from the biological activity current source at the site of interest of the subject, and The position of the current source is superimposed and displayed on the tomographic image of the region of interest of the specimen, and the degree of coincidence between the theoretical magnetic field data estimated based on the estimated position and orientation data of the current source and the measured magnetic field data A biological activity current source display device for grasping the position of a true current source by also displaying a value indicative of: (a) a virtual magnetic field generated from a current source virtually set at a site of interest of the subject The difference between the position of the current source estimated when any noise is superimposed on the data and the position of the virtually set current source is represented by virtual magnetic field data and the virtual magnetic field data with the noise superimposed. (B) calculating the degree of coincidence between the measured magnetic field data and theoretical magnetic field data estimated based on the estimated position and direction data of the current source. Then, an amount of deviation corresponding to the degree of coincidence is read out from the storage means, and an area setting means for setting an area where a true current source is likely to exist; and (c) estimation on a tomographic image of the site of interest. Image processing means for superimposing an area set by the area setting means on the set position of the current source; and (d) display means for displaying an image processed by the image processing means. It is assumed that.

[Operation] The operation of the present invention is as follows. In the present invention, first, the relationship between the deviation amount of the current source and the degree of coincidence is stored in the storage means as follows. That is, a current source is virtually set at a site of interest of the subject, and magnetic field data from the current source is used as virtual magnetic field data, and any noise is superimposed on the virtual magnetic field data to estimate the position of the current source. The amount of deviation between the estimated position of the current source and the position of the current source virtually set at that time is determined. Further, the degree of coincidence between the virtual magnetic field data and the virtual magnetic field data on which arbitrary noise is superimposed is determined. The amount of deviation from the virtually set current source and the degree of coincidence at that time are obtained by variously changing the noise level,
The relationship between the amount of deviation from the virtually set current source and the degree of coincidence is stored in the storage means.

Next, theoretical magnetic field data is estimated based on the position and direction data of the current source estimated based on the measured magnetic field data obtained by measuring the minute magnetic field from the current source at the site of interest of the subject. I do. The degree of coincidence between the theoretical magnetic field data and the measured magnetic field data is calculated, the amount of deviation corresponding to the degree of coincidence is read from the storage means, and an area where a true current source may exist is set. The image processing means includes:
The position of the current source estimated by the current source estimating means is specified on the tomographic image of the region of interest, and the area set by the area setting means is superimposed on the position. This region is a region surrounded by a circle having a radius corresponding to the amount of deviation of the position of the current source around the estimated position of the current source. An image in which this region is superimposed on the tomographic image of the region of interest is output to the display means.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a living activity current source display device according to the present invention.

In the figure, reference numeral 2 denotes a magnetically shielded room, in which a bed 3 on which the subject M lies supine, and a living body which is placed close to, for example, the brain of the subject M and is generated in the brain. A multi-channel SQUID sensor 1 for non-invasively measuring a small magnetic field by an active current source is provided. As described above, the multi-channel S
The QUID sensor 1 has a large number of SQUID sensors housed in a dewar in a state of being immersed in a refrigerant. In the present embodiment, when the brain of the subject M is a sphere, each SQUID sensor is composed of a pair of coils for detecting a magnetic field component in the radial direction.

The magnetic field data detected by the multi-channel SQUID sensor 1 is provided to a data converter 4 and converted into digital data. The current source estimating unit 8 estimates the position, the direction, and the size of the current source at the site of interest of the subject M based on the magnetic field data collected by the data collecting unit 5. The estimated current source data and the measured magnetic field data are transmitted to the data processing unit 9 via the communication line 14. The stimulating device 6 is for giving an electrical stimulus (or a sound, a light stimulus, or the like) to the subject M. The positioning unit 7 is a device for grasping the positional relationship of the subject M with respect to a three-dimensional coordinate system based on the multi-channel SQUID sensor 1. For example, small coils are attached to a plurality of locations on the subject M, and power is supplied to these small coils from the positioning unit 7. Then, the magnetic field generated from each coil is detected by the multi-channel SQUID sensor 1 to grasp the positional relationship of the subject M with respect to the multi-channel SQUID sensor 1. In addition, as a technique for grasping the positional relationship of the subject M with respect to the SQUID sensor 1, a light beam is attached to the dewar to attach the light beam to the subject M.
To grasp the positional relationship between the two, or Japanese Patent Application Laid-Open Nos. 5-2370065 and 6-78892.
Various techniques disclosed in No. 5, etc. are used.

The data processing unit 9 superimposes a region where a current source may exist on a tomographic image of a region of interest of the subject M based on the position data of the current source sent from the current source estimating unit 8. Image. The data processing unit 9
As will be apparent from the description to be described later, it corresponds to an area setting unit and an image processing unit in the present invention. The memory 10 as storage means of the present invention provided in association with the data processing unit 9 previously stores data on the amount of displacement of the current source corresponding to the degree of coincidence or correlation obtained by simulation. ing.

On the magneto-optical disk 13, a tomographic image obtained by an X-ray CT apparatus or an MRI apparatus is recorded.
The display means 11 of the present invention, for example, a color monitor 11
a and the color printer 11b are adapted to display and print the image output from the data processing unit. The tomographic image obtained by the X-ray CT apparatus or MRI apparatus may be configured to be directly transmitted to the data processing unit 9 via the communication line 14 shown in FIG.

As described above, the multi-channel SQUA
The position relationship of the subject M with respect to the three-dimensional coordinate system based on the ID sensor 1 is measured and stored, and the multi-channel SQUID sensor 1 detects a position of interest from the subject M, for example, from a biological activity current source in the brain. Measure a small magnetic field. The current source estimation unit 8 estimates the current source based on the magnetic field data based on the data collected by the data collection unit 5. Specifically, a method such as a minimum norm method or a least square method is used as a method for estimating the current source. After the estimation of the current source, the data processing unit 9 outputs an image in which a region where the current source may exist to the tomographic image is superimposed on a color monitor or the like. Hereinafter, the processing performed by the data processing unit will be described with reference to the flowchart shown in FIG.

First, a current source is virtually set in a region of interest of a subject, and magnetic field data obtained from this current source is used as virtual magnetic field data. An arbitrary noise is superimposed on the virtual magnetic field data to estimate the position of the current source. The amount of deviation between the estimated position of the current source and the position of the previously virtually set current source is determined. Further, the degree of coincidence between the virtual magnetic field data and the virtual magnetic field data on which any noise is superimposed is determined.
A deviation amount from the position of the virtually set current source,
The degree of coincidence at that time is obtained by variously changing the noise level, and the relationship between the amount of deviation and the degree of coincidence is stored in the memory 10 (step S1). FIG. 3 is a schematic diagram showing the relationship between the degree of coincidence and the amount of deviation in the memory 10. Here, the data of the deviation amount obtained by the simulation is stored in the memory 1 through the magneto-optical disk 13 or the communication line 14.
Sent to 0.

The Bio-Savart method is used on the basis of the measured magnetic field data obtained by measuring the current source at the site of interest of the subject and the data on the position and orientation of the current source estimated based on the measured magnetic field data. And the theoretical magnetic field data estimated
The degree of coincidence is calculated by giving it to equation (1) described below (step S2). Here, the degree of coincidence is used as a value indicating the degree of coincidence, but the same applies when a correlation value is used. Here, the function for calculating the degree of coincidence can be expressed by the following equation (1), and the function for calculating the correlation value can be expressed by the following equation (2).

[0023]

(Equation 1)

In the equations (1) and (2), the units of the calculated values A and C are represented by percentages (%).
For example, when A = 90 is calculated, it is expressed that the measured magnetic field data and the theoretical magnetic field data match by 90%.

The area setting means stores the amount of displacement of the position of the current source corresponding to the degree of coincidence calculated in step S2 in the memory 10
Call from. This deviation amount is defined as a radius r, and a circle having a radius r centered on the estimated position data of the current source is set (step S3).

A tomographic image including the estimated current source is called from the magneto-optical disk 13. Step S is performed on this tomographic image.
Overlap the circle set in 3. (Step S4). Here, the position of the tomographic image is represented by a two-dimensional coordinate system, and the estimated current source is included on the tomographic image. The center of the circle set in step S3 may be superimposed on the coordinates of the estimated current source on the cross-sectional image. This tomographic image is displayed on the display means 11, for example, the color monitor 11a or the color printer 11b (step S5).

An image displayed on the monitor screen according to this embodiment will be described with reference to FIG. Monitor screen 2
In step S4, the upper tomographic image 21a, the posterior sectional image 21b, and the lateral tomographic image 21 of the brain including the current source are set to 0.
c and the degree of coincidence 23 are displayed. Also,
The region 22 where the current source is likely to be set, which is set in step S3, is displayed so as to be superimposed on the tomographic images 21a, 21b, and 21c of the brain.

[0028]

As is apparent from the above description, according to the present invention, since the deviation amount corresponding to the value indicating the degree of coincidence is stored in the storage means in advance, the measured magnetic field data and the theoretical magnetic field data are stored. A deviation amount corresponding to a value indicating the degree of coincidence is called, and based on this deviation amount, a region where the position of the current source is likely to be present is set, and the above-described region is displayed on a tomographic image of a site of interest of the subject. Since the tomographic image in which the regions are superimposed is displayed on the display means, there is no need to consider the value indicating the degree of coincidence, and only by looking at the tomographic image displayed on the display means, there is a possibility that the current source exists. The area can be checked accurately and easily.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a biological activity current source display device according to the present invention.

FIG. 2 is a flowchart illustrating a processing procedure performed by a data processing unit according to the embodiment;

FIG. 3 is a schematic diagram illustrating a relationship between data stored in a memory of the biological activity current source display device according to the embodiment.

FIG. 4 is a schematic diagram of a screen displayed on the biological activity current source display device of the embodiment.

FIG. 5 is a schematic view of a screen displayed on a conventional life activity current source display device.

[Explanation of symbols]

 9 Data processing unit 10 Memory 11a Color monitor 11b Color printer 20 Monitor screen 21a Upper cross-sectional image 21b Rear cross-sectional image 21c Side cross-sectional image 22 Area where a current source may be present

Claims (1)

[Claims] The present invention estimates a current source at a site of interest of a subject based on measured magnetic field data obtained by measuring a minute magnetic field generated from a biological activity current source at a site of interest of the subject. The position of the current source is superimposed and displayed on the tomographic image of the site of interest, and the degree of coincidence between the theoretical magnetic field data estimated based on the estimated position of the current source and the direction data and the measured magnetic field data is determined. A biological activity current source display device for grasping the position of a true current source by displaying the indicated values together, wherein (a) virtual magnetic field data generated from a current source virtually set at a site of interest of a subject The position of the current source estimated when any noise is superimposed on, and the amount of deviation between the position of this virtually set current source, the virtual magnetic field data with the noise superimposed and the virtual magnetic field data The match of (B) calculating a degree of coincidence between the measured magnetic field data and theoretical magnetic field data estimated based on the estimated position and orientation data of the current source; An area setting means for reading a shift amount corresponding to the degree of coincidence from the storage means and setting an area where a true current source may exist; and (c) a current estimated on a tomographic image of the site of interest. A living body, comprising: image processing means for superimposing an area set by the area setting means at the position of a source; and (d) display means for displaying an image processed by the image processing means. Active current source display.