JPH07227386A - Magnetic measurement apparatus - Google Patents

Abstract

PURPOSE:To shorten calculation time for estimation of a signal source, to improve accuracy of estimation of the signal source and to provide more accurate positional information in displaying the signal source. CONSTITUTION:A multi-channel SQUID sensor apparatus 1 wherein a magnetic field generated from a magnetic field generating source in the head of an examinee is measured, a region-initial value specifying part 5 for specifying a region where the position for the magnetic field generating source in the head can possibly exist by utilizing the image data of the head of the same examinee obtd. from a tomogram photographing apparatus 11, a data processing- controlling part 3 wherein a region data is formed based on an command content by the region-initial value specifying part 5 and the magnetic field generating source is explored based on the magnetic field measuring data and the region data by the multi-channel SQUID sensor apparatus 1 and a displaying part 6 for displaying these contents as an image are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic measuring device for measuring a magnetic field generated from a living body or the like to estimate an active site of the living body or the like.

[0002]

2. Description of the Related Art Conventionally, a multi-channel SQUID sensor (SQUID sensor is a superconducting quantum interference magnetometer, which is a magnetic sensor with high sensitivity to a weak magnetic field generated from a living body such as a brain or a heart. Interferen
A biomagnetism measuring device that obtains the position of an active site (signal source) in a living body by measuring with a ce Device) has been applied to cerebral function elucidation and clinical medical treatment of the brain and heart.

The principle of a multi-channel SQUID sensor system as a biomagnetism measuring device will be briefly described with reference to FIG.

That is, in FIG. 7, 101 is a brain activity current, 102 is a brain magnetic field, 103 is a SQUID sensor, and 104.
Is liquid helium.

When a person thinks about something or receives an external stimulus, nerve cells in the cerebrum are excited and a current flows in the brain.
When such a brain activity current 101 flows, a brain magnetic field 102 based on the "right-handed screw law" is generated. It is the above-mentioned SQUID sensor 103 (for example, 64 SQUID sensors 103 are used as an actual device) that measures this brain magnetic field, and the entire system is a multi-channel SQUID sensor.
It is called a sensor system. Since the brain magnetic field is extremely weak and is several hundred millionth of the earth's magnetism, and can be detected only by the super-sensitive magnetic sensor called SQUID that utilizes the superconducting phenomenon at the liquid helium temperature, the liquid helium 104 is filled. The SQUID sensor 103 is arranged in the container. In the above configuration, to estimate the signal source corresponding to the electrophysiological activity site in the brain from the measured brain magnetic field, use a sphere model, a flat plate model, or a triangular element model for the living body. Search for the position of the current dipole that minimizes the difference between the magnetic field derived by theoretical calculation generated from the current dipole that is assumed to exist at a specific position in the approximate model and the actually measured brain magnetic field The calculated position finally obtained is used as the position of the signal source.

Among the methods of approximating a living body, a method of using a tomographic image to create a triangular element model capable of reproducing the living body most accurately (Various models of the head and t
heirinfluence on MEG's, Jan WH et al, Twente Uni
v., The Netherland, Biomagnetism '87).

Further, as a method for making the position of the estimated signal source approximately equal to the anatomical position in the living body as described above, it is combined with a tomographic image obtained from a tomographic imaging device such as an MRI device. Displayed (Magneteic localization
of neuroral activity in thehuman brain, T. Yamamo
to et al., New York Univ., Proc. Natl. Acad. Sci.
USA, November, 1988).

[0008]

However, in the above configuration, in the process of theoretical calculation of the estimation of the signal source, the actual anatomical information is ignored and the set approximate model is freed. Or to search all over,
There were the following issues.

That is, (1) when performing theoretical calculation,
The initial value of the signal source, regardless of the actual anatomical information,
Since it is set at an appropriate place in the approximate model, the search efficiency is low depending on how to set the initial value, and the time required for calculation and the like is long.

(2) An area where no signal source can exist, for example, a defective portion such as a cavity in the brain may be searched for and fall into a local minimum, so that the correct source cannot be searched.

(3) The program cannot be evaluated because the trajectory during the search for the signal source in the theoretical calculation is unknown and the efficiency of the signal source estimation algorithm cannot be grasped.

Further, in the conventional display of the estimated signal source, since only the composite display of the signal source and the tomographic image is displayed, it is possible to grasp a rough positional relationship, but it is not possible to obtain accurate positional information. There was also such a problem.

In consideration of such problems of the conventional biomagnetism measuring apparatus, the present invention can shorten the calculation time in the signal source estimation, improve the accuracy of the signal source estimation, and display the signal source. It is an object of the present invention to provide more accurate position information as compared with the conventional one.

[0014]

The present invention according to claim 1 uses the image data of a living body obtained by a tomographic imaging apparatus to use the whole or part of a region where the position of a magnetic field generation source in the living body can exist. Area designating means for designating an area, area data creating means for creating area data based on the content of the area designating means, and magnetic search for searching at least the position of the magnetic field generation source using the area data. And a magnetic measuring device including means.

According to a second aspect of the present invention, the initial position designating means for designating at least the initial position of the magnetic field generation source, which is used when the magnetic search means searches for at least the position of the magnetic field generation source in the designated area. It is a magnetic measuring device provided with.

The present invention according to claim 3 is the magnetic measuring apparatus, wherein by designating the position of a part in the existing region, all the closed regions to which the part belongs are designated.

[0017]

According to the present invention, the area designating means designates all or part of the area where the position of the magnetic field generation source in the living body can exist by using the image data of the living body obtained by the tomographic imaging apparatus, The area data creating means creates area data based on the contents of the instruction by the area designating means, and the magnetic search means uses the area data to search at least the position of the magnetic field generation source.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram for explaining the configuration of the biomagnetism measuring device according to this embodiment, and the configuration will be described with reference to FIG.

That is, in the figure, 1 is a multi-channel SQUID sensor for measuring the magnetic field from the signal source,
Reference numeral 2 is a data collection unit that collects data measured by the multi-channel SQUID sensor 1, and reference numeral 3 is a multi-channel SQUID sensor.
A data processing / control unit that searches for a signal source based on a measurement result using the D sensor 1 and synthesizes data from a tomographic imaging device 11 of an external device, which will be described later, with data from the multi-channel SQUID sensor 1. 4 is multi-channel SQ
A position measuring unit that aligns the UID sensor 1 and a tomographic imaging apparatus 11 described later, and 5 is an area for designating a search range or the like when the data processing / control unit 3 searches for a signal source or the like. An initial value designation unit, 6 is a tomographic imaging apparatus 11
Is a display unit for displaying the image and the search range of the signal source designated by the area / initial value designation unit 5, and 7 is a recording unit for recording various data by a printer or the like.
Reference numeral 11 is a tomographic imaging device as an external device for taking a tomographic image of the head of the subject. Also, the data processing / control unit 3
Includes the magnetic search means and the area data creating means in the present invention, and the area / initial value specifying section 5 includes the area specifying instruction means and the initial position specifying means in the present invention.

Next, the operation when the brain magnetic field is measured by the biomagnetism measuring apparatus of this embodiment will be described with reference to the flowchart shown in FIG.

[Step 21]: A tomographic image is taken.

That is, a tomographic image of the subject's head is taken using the tomographic imaging device 11. The number of tomographic images must be sufficient to accurately reproduce the inside of the head,
Usually, the number is about 128 and can be changed as appropriate.

[Step 22]: Specify the search range of the signal source.

That is, the tomographic images picked up by the tomographic image pickup device 11 are transferred to the data processing / control unit 3 and sequentially displayed on the display unit 6, and the operator confirms these tomographic images while the signal source in each tomographic image is confirmed. The search range is designated by the area / initial value designation unit 5 such as a mouse. The data processing / control unit 3 according to the designation contents of the area / initial value designation unit 5
Creates binary image data in which the search range is "1" and the non-search range is "0".

The operator uses the area / initial value designation section 5 such as a mouse for the tomographic image on the screen of the display section 6,
The area to be searched may be designated one by one, or the designated area may be corrected while checking the screen of the display unit 6, and the search range may be interactively limited through the area / initial value designation unit 5, or It is also possible to automatically specify the search range to some extent by edge detection or the like.

What is important here is that when it is known in advance that the signal source cannot exist anatomically, the area / initial value designating section 5 is used to designate the location as a non-search range. That is. Also, in the case where the subject's brain is defective and there is a cavity in part of the brain, or when part of the brain is missing due to an accident, etc., the area where the signal source cannot exist Is designated as a non-search range.

FIG. 3A shows an example of an original image of the head tomographic image of the subject displayed on the display unit 6, and FIG. 3B shows binary screen data created by the data processing / control unit 3. Based on this, the search range is displayed in white in the binary image example displayed on the display unit 6. Here, 21 is the brain region of the subject,
22 is a cavity existing in the brain region. Also, 31
Indicates a search range, and 32 indicates a non-search range.

[Step 23]: A tomographic image is created.

That is, a tomographic image in one direction is created from a tomographic image in one direction. The search range of the signal source estimation obtained in step 22 is also reflected in the newly created image.

[Step 24]: The search range is displayed on the three-dimensional tomographic images.

That is, tomographic images in three directions are displayed so that the search range on each tomographic image can be visualized.

Specifically, the data processing / control section 3 creates a mode for displaying only the original image and a combined display mode for combining the original image and the binary image. In the composite display mode, the edge information of the search range is overlay-displayed on the original image. For example, the edge information is displayed on the screen of the display unit 6 as a solid line or a broken line, only the original image corresponding to the search range is displayed, or the original image in the non-search range is displayed with a low luminance. Things can be done.

[Step 25]: The brain magnetic field is measured.

On the other hand, the brain magnetic field of the subject is measured using the multi-channel SQUID sensor 1.

[Step 26]: Multi-channel SQUID
The coordinate system of the sensor 1 and the tomographic imaging apparatus 11 are aligned with each other.

That is, the position measuring unit 4 is used to align the multi-channel SQUID sensor 1 and the tomographic imaging apparatus 11. The alignment method calculates a coordinate conversion matrix between the three by measuring at least three points on the subject's head with the multi-channel SQUID sensor 1 and the tomographic imaging device 11 (a MEG mapping method using multi-channel SQUID and MRI, Masashi Kiyoaki et al., IPSJ 45th Annual Conference 1992).

[Step 27]: The initial value (initial position, initial position) of the signal source is within the search range within the predetermined approximate model (the approximate model created by the conventional method is also synthetically displayed) synthesized and displayed. Direction and size).

That is, the three-direction tomographic images are displayed in appropriate slices on the display unit 6 in the composite display mode created in step 24, and the operator looks at the display screen and compositely displays on each of the three-direction tomographic images. In addition, the initial value of the signal source is set within the search range within the predetermined approximation model.

FIG. 4 shows the initial value of the signal source displayed within the search range on the three-direction tomographic image. Here, 41 is an initial signal source indicating an initial value of the signal source.

First, the initial position of the initial signal source 41 is set by the operator designating a point on the display of the display unit 6 using the area / initial value designating unit 5 such as a mouse. Is transmitted to the data processing / control unit 3, and the signal source is an arrow or a combination of a circle and a bar at the designated position on the display unit 6 (for example, the tip of the arrow or the circle is the initial position, and the direction of the bar is the initial direction). , The length of the stick shows the size) is superimposed. Since the position of the initial signal source 41 is interlocked between the three-direction images, a change in one unidirectional image also changes the position of the initial signal source 41 on another image.

Next, after setting the initial position of the initial signal source 41, the direction and size of the signal source are similarly set as the initial direction.

In this way, the initial values (initial position, initial direction, and size) are accurately set from the anatomical information, so that the search time can be reduced as compared with the conventional case.

Further, unlike the conventional case, the initial value is set in a completely different place, and the possibility of falling into a local minimum and erroneously estimating the signal source is reduced.

[Step 28]: The signal source is searched within the search range in the approximate model.

That is, the data processing / control section 3 uses the initial position of the signal source set in step 27 as a starting point on the basis of the brain magnetic field data and the alignment information in steps 25 to 26 to obtain more error. A small number of signal sources are searched within a search range within a predetermined approximation model. The signal source in the middle of the search is superimposed on the three-direction tomographic image in which the signal source exists.

When selecting candidate points one after another from the initial position during the search, the data processing / control unit 3 checks each time whether the candidate points are within the search range on the tomographic image, that is, pixel Whether the value is "1" or "0" is determined, and if it is "1", it is regarded as a candidate point.

Since the search range of the signal source estimation is limited in this way, the calculation time required for the signal source estimation can be shortened as compared with the conventional case.

[Step 29]: The signal source for which the search is completed is displayed on the tomographic image.

The final result signal source is displayed on the tomographic image on the display unit 6. FIG. 5 shows a state in which the signal source of the final result is displayed on the three-direction image. Here, 51 is a final signal source indicating a signal source of the final result. In FIG. 6, the final signal source 51 is displayed on the composite image of the surface model 61 of the epidermis of the head created from the tomographic image and the tomographic image.

[Step 30]: Visualize the search situation of the signal source.

That is, since information such as the position, size, and direction of candidates of all the signal sources being searched (initial signal source 41 to final signal source 51) is stored in the data processing / control unit 3, all of them are stored. Since the candidate of the signal source can be displayed simultaneously or the trajectory of the search can be visualized as an animation, the efficiency of the search algorithm in the signal source estimation can be evaluated, which is useful for the development of a highly efficient algorithm.

Further, in the case of simultaneously displaying all candidates of the signal source, the progress of the search can be clearly indicated by representing the signal source in a three-dimensional shape and changing the color of each three-dimensional shape. For example, there are a method of lowering the brightness at the beginning of the search and a higher brightness at the end of the search, and a method of using rainbow colors.

[Step 31]: Position information of an arbitrary point in the biometric image space is calculated and displayed.

All the signal source candidates in a certain experiment or the signal sources estimated in different experiments can be displayed at the same time, and the positional information of an arbitrary point and the positional relationship between two arbitrary points can be calculated and displayed. The designated point in the biometric image space is set using the area / initial value designation unit 5 such as a mouse. This allows
It is possible to accurately grasp the positional relationship between the signal sources, the signal sources and the anatomical feature points, or the anatomical feature points.

In this way, it is possible to shorten the time of signal source estimation and improve the accuracy, to evaluate the efficiency of the algorithm of signal source estimation, and to determine the positional relationship between the functional information of the living body and the anatomical information. It becomes possible to grasp.

In the present invention of claim 1, "designating a part" of "designating all or part of the region where the position of the magnetic field generation source in the living body can exist" means the magnetic field generation source. Does not necessarily specify all the areas where the position may exist, for example, based on the judgment of the operator, when specifying only a part of a specific area among the possible areas,
When specifying the above-mentioned possible region in the approximate model, etc.
In short, it means that the designated area is not limited to all the areas where the position of the magnetic field generation source can exist.

The living body to be measured has been described as the head of the subject in the above embodiment, but the present invention is not limited to this, and may be another living body part such as the heart, for example.
Alternatively, the subject may be in a brain-dead state, or may be a living body other than a human being, and may be anything as long as it has a signal source that generates a magnetic field.

Further, the present invention may be realized in terms of hardware using each component, or not limited to this, and may be realized by software.

[0060]

As is apparent from the above description,
The present invention of claim 1 has an advantage that the calculation time in the signal source estimation can be shortened and the accuracy of the signal source estimation can be improved.

In addition to the above effects, the present invention of claim 2 has an advantage that the calculation time in signal source estimation can be further shortened.

In addition to the above effects, the present invention of claim 3 has an advantage that a region where a signal source can exist can be easily designated.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an entire system including a biomagnetism measuring device according to an embodiment of the present invention.

FIG. 2 is a flowchart of the operation of the entire system including the biomagnetism measuring device according to the embodiment of the present invention.

FIG. 3A is an example of an original image of a tomographic image of the head of a subject displayed on the display unit 6 of the same embodiment. FIG. 3B is binary screen data created by the data processing / control unit 3 of the same embodiment. Showing an example of a binary image displayed on the display unit 6 based on

FIG. 4 is an explanatory diagram showing an initial signal source 41 displayed within a search range on a three-direction tomographic image on the display unit 6 of the embodiment.

FIG. 5 shows the final signal source 51 in the display unit 6 of the embodiment.
Explanatory drawing showing the state where is displayed on the three-way image

FIG. 6 shows a final signal source 51 in the display unit 6 of the embodiment.
Is an explanatory view showing a state in which is displayed on the composite image of the surface model 61 of the head epidermis and the tomographic image.

FIG. 7 is an explanatory diagram showing the principle of a conventional biomagnetism measuring device.

[Explanation of symbols]

 1 multi-channel SQUID sensor 2 data acquisition unit 3 data processing / control unit 4 position measurement unit 5 region / initial value designation unit 6 display unit 7 recording unit 11 tomographic imaging device mounting unit 21 brain region 22 cavity 31 search range 32 non-search range 41 initial signal source 51 final signal source 61 surface model 101 brain activity current 102 brain magnetic field 103 SQUID sensor 104 liquid helium

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[Procedure amendment]

[Submission date] March 16, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

FIG. 4 shows an initial signal source 41 displayed in a search range on a three-direction tomographic image on the display unit 6 of the embodiment, which is a halftone image displayed on a display output from a printer. Yes, it is a photograph instead of a drawing.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

FIG. 5 shows the final signal source 51 in the display unit 6 of the embodiment.
Is displayed on the three-way image,
A halftone image displayed on the display is output from a printer and is a photograph instead of a drawing.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

FIG. 6 shows a final signal source 51 in the display unit 6 of the embodiment.
Shows a state in which the image is displayed on the composite image of the surface model 61 of the head epidermis and the tomographic image, and the halftone image displayed on the display is output from the printer and is a photograph instead of a drawing.

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

[Procedure correction 6]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

Front page continuation (72) Inventor Yoshifumi Sadahiro 3-2-95 Chiyosaki, Nishi-ku, Osaka City OGIS Research Institute (72) Inventor Hideyuki Tsutsui 3-95 Chiyosaki, Nishi-ku Osaka City In-house OGIS Research Institute

Claims (3)

[Claims] 1. A region designation instruction means for designating all or a part of a region in which the position of a magnetic field generation source in the living body may exist by using image data of the living body obtained by a tomographic imaging apparatus. It is characterized by further comprising area data creating means for creating area data based on the contents of the area designation instructing means, and magnetic searching means for searching at least the position of the magnetic field generation source using the area data. Magnetic measuring device. 2. An initial position designating means for designating at least an initial position of the magnetic field generation source, which is used when the magnetic search means searches for at least the position of the magnetic field generation source, in the designated area. Claim 1 characterized by the above.
The magnetic measuring device described. 3. The method according to claim 1 or 2, wherein by designating a position of a part in the possible region, all the closed regions to which the part belongs are designated. Magnetic measuring device.