JPH114815A - Living body magnetism measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately seize a condition of a living body action current source by obtaining living body magnetism data with every magnetism sensor every time when magnetism of a living body from an interest part of a subject is measured, and accurately removing a sudden noise by compating this data with a judging value previously found according to sensitivity with every magnetism sensor. SOLUTION: Magnetism of a living body generated from a living body action current source in an interest part is individually measured by plural magnetism sensors (SQUID sensors) 1. By a data processing part 6, additively averaging processing is performed on a large number of living body magnetism data groups obtained by repeating this measurement numerous times, and a condition of the living body action current source is seized on the basis of the living body magnetism data groups after the additively averaging processing. In this case, a judging value to judge whether living body magnetism data individually measured with every magnetism sensor 1 is valid or invalid, is calculated on the basis of sensitivity with every magnetism sensor 1, and when the living body magnetism data groups are judged as effective by comparing its judging value and living body magnetism data with each other, additively averaging processing is performed on its living body magnetism data groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biomagnetism measurement for measuring a biomagnetism generated from a bioactivity current source at a site of interest of a subject and grasping a state of the bioactivity current source based on the biomagnetism data. The present invention relates to an apparatus, and particularly to a technique for measuring the biomagnetism with high accuracy.

[0002]

2. Description of the Related Art A minute magnetism is generated from a living body with a living activity current generated in the living body. For example, biomagnetism generated from the brain is called magnetoencephalography, and induced brain magnets generated by stimulating the living body, spontaneous brain magnets naturally generated from the brain like α waves and spikes of epilepsy, etc. is there.

In recent years, SQUIDs (Superconducing Quantum) have been used as magnetometers for measuring minute biomagnetism from living bodies.
A multi-channel SQUID sensor using an Interference Device (superconducting quantum interferometer) has been developed. In this multi-channel SQUID sensor, a large number of magnetic sensors are immersed in a refrigerant such as liquid nitrogen and stored in a container called a dewar.

[0004] The multi-channel SQUID sensor (hereinafter referred to as a “magnetometer”) is placed at a site of interest of a subject, for example, outside the head, and a minute living body generated from a biological activity current source generated in the head. The magnetism can be measured non-invasively by a plurality of magnetic sensors housed in the magnetometer. By displaying the biomagnetic data of each magnetic sensor on a display device such as a color monitor as a waveform or a magnetic field intensity distribution, it is possible to grasp the state of the biological activity current source in the region of interest of the subject.

Conventionally, as a method of measuring minute biomagnetism generated by a biological activity current source in a head, which is a site of interest of a subject, the same stimulus is repeated several hundred times on the subject to reduce the number of stimuli. The same number of biomagnetic data are obtained for each magnetic sensor. Based on the plurality of biomagnetic data groups,
By performing the averaging process, a biomagnetic data group in which biomagnetism generated from the bioactivity current source is emphasized is obtained.

[0006] The averaging process is a method of compressing only noise included in the measured biomagnetic data by adding and averaging the biomagnetic data obtained for each magnetic sensor obtained every time the biomagnetism is measured. is there. When the biomagnetic data is added and averaged, the biological signal sent from the biological activity current source has the same signal component each time it is measured. However, since noise has a different signal component each time, when added and averaged, noise signal components cancel each other. In this way, by performing the averaging process, by observing the waveform and the magnetic field intensity distribution based on the biomagnetic data group in which the noise is compressed, the size and direction of the biological activity current source in the region of interest of the subject can be obtained. Understand the state of.

[0007]

However, the prior art having such a structure has the following problems. The induced electroencephalogram to be measured is extremely weak, and noise caused by spontaneous electroencephalogram in a region of interest of the subject or sudden noise from an apparatus or the like may be mixed into biomagnetic data. If this noise is extremely large with respect to the induced brain magnetic field, the noise cannot be completely compressed even if the averaging process is performed. There is a problem that the state of the biological activity current source cannot be accurately grasped from the waveform based on the biomagnetic data including the noise, the magnetic field strength distribution, and the like. In addition, since the averaging process is performed based on the biomagnetic data group after the measurement of the biomagnetism, if noise is mixed in the entire biomagnetic data group, do not perform the magnetic field measurement again. In addition, there is a problem that the examination period becomes longer and the burden on the patient as the subject becomes excessive.

The present invention has been made in view of such circumstances, and a biomagnetism measuring apparatus capable of easily determining whether measured biomagnetic data is valid or invalid sequentially during magnetic field measurement. The purpose is to provide. It is another object of the present invention to provide a biomagnetism measuring apparatus capable of accurately grasping the state of a living activity current source in a short examination period by using the effective biomagnetic data.

[0009]

The present invention has the following configuration to achieve the above object. That is, the invention according to claim 1 measures a plurality of biomagnetisms generated from a bioactivity current source in a region of interest of a subject individually by a plurality of magnetic sensors, and repeats the measurement a number of times. Averaging is performed on the biomagnetic data group of
In the biomagnetism measuring device that grasps the state of the bioactivity current source based on the biomagnetic data group after the averaging process, (a) whether the biomagnetic data individually measured for each magnetic sensor is valid An individual judgment value calculating means for calculating a judgment value for judging invalidity based on the sensitivity of each magnetic sensor; and (b) storing a judgment value for each magnetic sensor calculated by the individual judgment value calculating means. (C) comparing the determination value for each magnetic sensor stored in the first storage means with biomagnetic data measured for each magnetic sensor, Comparing and determining means for determining whether the biomagnetic data group is valid or invalid; (d) second storing means for storing the valid biomagnetic data group determined by the comparing and determining means; For valid biomagnetic data group of a predetermined number in the second storage means, it is characterized in that an averaging processing means for performing averaging processing.

According to a second aspect of the present invention, there is provided the biomagnetic measurement apparatus according to the first aspect, wherein (f) the determination value is determined based on a plurality of invalid biomagnetic data groups determined by the comparing and determining means. Magnetic sensor identification means for identifying a magnetic sensor that has measured biomagnetic data deviating from each other for each of the invalid biomagnetic data groups; and (g) a magnetic sensor identification means for each of the invalid biomagnetic data groups identified by the magnetic sensor identification means. When the same magnetic sensor is specified for each invalid biomagnetic data group among the magnetic sensors, the first magnetic sensor corresponding to this magnetic sensor is identified.
And a judgment value rewriting means for rewriting the judgment value in the storage means to a larger judgment value.

[Operation] The operation of the first aspect of the invention is as follows. The plurality of magnetic sensors have a specific sensitivity for each magnetic sensor. Determination values based on the sensitivity of the magnetic sensors are calculated for all the magnetic sensors, and these determination values are stored in the first storage unit. Next, every time the same stimulus is applied to the subject, the biomagnetism generated from the bioactivity current source is measured to obtain biomagnetic data, that is, a biomagnetic data group for each magnetic sensor. By comparing the biomagnetic data for each magnetic sensor with the determination value for all the magnetic sensors, it is determined whether the biomagnetic data group is valid. This effective biomagnetic data is stored in the second storage means. When a predetermined number of valid biomagnetic data groups are collected in the second storage means, an averaging process is performed on the basis of the predetermined number of valid biomagnetic data groups, so that biomagnetic data free from noise is obtained. Obtainable.

The operation of the invention described in claim 2 is as follows. Based on the plurality of invalid biomagnetic data groups determined by the comparing and determining means, a magnetic sensor that measures biomagnetic data out of the determination value is specified for each invalid biomagnetic data group. When the same magnetic sensor is specified for each invalid biomagnetic data, the judgment value corresponding to this magnetic sensor is rewritten to a larger judgment value to eliminate an abnormality caused by the specific magnetic sensor itself. Can be.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

<First Embodiment> An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a schematic configuration of the biomagnetism measuring apparatus according to the embodiment. In the present embodiment, it is assumed that the region of interest of the subject is the head, for example, and the body activity current source in the head is measured.

In FIG. 1, reference numeral 1 denotes a multi-channel SQUID.
4 shows a D sensor. The multi-channel SQUID sensor 1 is arranged close to the outside of the head of the subject M.
The multi-channel SQUID sensor 1 is a Dewar 1a
In this configuration, m magnetic sensors S _{1 to} S _m are immersed in a refrigerant and stored. The multi-channel SQUID sensor 1 (hereinafter, referred to as “magnetic flux meter 1”) and the subject M are arranged in the magnetically shielded room 11. Incidentally, the magnetic sensor S ₁ to S _m is composed of a SQUID sensor unit for converting magnetism detecting a pickup coil unit for detecting the magnetism voltage or the like.

The stimulating device 3 is for giving an electrical stimulus (or a sound or a light stimulus) to the subject M. The stimulating device 3 repeatedly applies the same stimulus to the subject M several hundred times, and generates biomagnetism several hundred times from the biological activity current source at the site of interest in the subject M. The magnetic sensors S _{1 to} S _m sequentially measure biomagnetism generated each time a stimulus is applied. The measured biomagnetic data group is converted into digital data by the data conversion unit 4 and then collected by the data collection unit 5.

The data processing section 6 has functions as an individual judgment value calculating means, a comparison judging means, an averaging processing means and a judgment value rewriting means in the present invention, as will be apparent from the description to be described later. Also, the first memory 7a,
The second memory 7b corresponds to the first storage unit and the second storage unit of the present invention. Various data are stored in the third memory 7c according to the processing in the data processing unit 6. A color monitor 8 and a color printer 9 provided in association with the data processing unit 6 output a waveform, a magnetic field intensity distribution, and the like based on the measured biomagnetic data.

Referring now to the flowchart of FIG.
A processing procedure performed in the embodiment will be described.

[0018] Step S1 (calculated determination value) magnetic sensor S ₁ to S _m has the magnetic flux-voltage conversion coefficient δ ₁ ~δ _m depending on the variations in each performance. The magnetic flux voltage conversion coefficient is a coefficient for keeping the sensitivity of each magnetic sensor to the maximum, and indicates the degree of conversion when the magnetism detected by the pickup coil unit is converted to voltage by the SUQID sensor unit. is there. For example, there is a case where the magnetic sensor S ₁ detects the magnetism B ₁ and converts it to the voltage A. On the other hand, it is assumed that the magnetic sensor S ₂ detects the magnetism B ₂ and converts it to the voltage A. At this time, the magnetic sensors S ₁ and S ₂ obtain the same voltage A. However, since there is variation in performance between the magnetic sensor, not necessarily equal to the magnetic B ₁ and B _2. In such a case, based on the voltage obtained via the magnetic sensor, in order to specify the strength of the magnetism actually detected by the magnetic sensor,
A magnetic flux voltage conversion coefficient is used.

The data processing unit 6 is provided with a magnetic flux
Pressure conversion coefficient δ₁~ Δ_mFrom the judgment value L ₁~ L_mCalculate
You. This calculation formula is shown in the following formula (1).

L _k = A × δ _k × 3.0 × 10 ^-12 (1) L _k : judgment value of k-th magnetic sensor (k = 1 to m) A: A / D conversion Sampling value δ _k : value of the magnetic flux voltage coefficient of the k-th magnetic sensor (k = 1
To m) 3.0 × 10 ^-12 : magnetic field strength of noise (arbitrary value)

[0021] Equation (1), when the 3pt (Pikotesura) or more noise is measured by the biomagnetic incorporated in the magnetic sensor S _k, multiplied by 3pt the magnetic flux-voltage conversion coefficient [delta] _k of the magnetic sensor S _k. Further, since this value is converted into digital data, the value is multiplied by the sampling value A. This sampling value A can be calculated by A = 2 ^16/5 when ± 5 V is sampled at 16 bits.

The determination values L _{1 to} L _m are calculated by giving the magnetic flux voltage conversion coefficients δ _{1 to} δ _m to equation (1), respectively.
Step S1 corresponds to a function performed by the individual determination value calculating means of the present invention. Stores these decision values L ₁ ~L _m in the first memory 7a is a first storage means.

[0023] After calculating the judgment value L ₁ ~L _m in step S2 (biomagnetic measurement) step S1, by giving a stimulus to the subject M by the stimulator 3, bioelectric current sources occurring in the region of interest. The biomagnetism generated from this living activity current source is transmitted to the magnetic sensors S _{1 to} S _m in the magnetometer _1.
, A biomagnetic data group can be obtained. The biomagnetic data group is a collection of biomagnetic data measured by each magnetic sensor. The biomagnetic data group is converted into digital data by the data conversion unit 4 and then collected by the data collection unit 5.

Step S3 (less than judgment value?) Based on the biomagnetic data group obtained in step S2,
Obtaining a peak value of the biomagnetic data measured by the magnetic sensor S ₁ to S _m, respectively. Since each of these peak values may be positive or negative, the absolute value of each peak value is obtained. These and each peak value, and a judgment value L ₁ ~L _m respectively compares. If all the peak values are smaller than the corresponding determination values by this comparison, this biomagnetic data group is regarded as a valid biomagnetic data group. On the other hand, if at least one peak value is equal to or greater than the corresponding determination value,
This is an invalid biomagnetic data group. FIG. 3 is a schematic diagram showing the case where the biomagnetic data measured by the k-th magnetic sensor exceeds the determination value and the case where it does not exceed the determination value. In the figure, the symbol P indicates a peak value. L _k and −L _k indicate determination values.

If a valid biomagnetic data group is obtained by the above-described determination processing, this biomagnetic data is stored in the second memory 7b as the second storage means. In the case of invalid biomagnetic data, this biomagnetic data group is discarded. Step S3 corresponds to the function performed by the comparison and judgment means of the present invention.

Step S4 (is valid data a predetermined number?) It is checked whether a predetermined number of valid biomagnetic data groups stored in the second memory 7b are collected. If the number of valid biomagnetic data groups is less than the predetermined number, the processes performed in steps S1 to S3 are repeated until the number of valid biomagnetic data groups reaches the predetermined number. When the number of valid biomagnetic data groups in the second memory reaches a predetermined number by this repetition, the process proceeds to the next step S5.

Step S5 (Averaging process) An averaging process is performed based on the effective biomagnetic data group in the second memory 7b. For example, let the predetermined number be N,
N biomagnetic data B _kn measured by the magnetic sensor S _k
The following equation (2) is used to obtain the biomagnetic data _Mk after the averaging by adding the averaging.

[0028] _{M k = (ΣB kn) /} N ····· (2) M k: k -th biomagnetic data after averaging of the magnetic sensor B _k B _kn: at k-th magnetic sensor B _k Biomagnetic data measured at the 1st to Nth times ：: Addition of biomagnetic data obtained in one collection unit

According to equation (2), the k-th magnetic sensor S
The average of valid biomagnetic data measured at _k is calculated. By performing this process for each of the magnetic sensors S _{1 to} S _m , the average of the effective biomagnetic data group is obtained. This effective biomagnetic data group is a biomagnetic data group in which noise is compressed and only the biomagnetic signal based on the bioactivity current source is emphasized. Step S5
Corresponds to the function of the averaging processing means of the present invention.

[0030] Step S6 (display output) based on biomagnetic data averaging after the magnetic sensor S ₁ to S _m calculated in step S5, waveform display and a biomagnetic that capture each magnetic sensor, It is displayed on the color monitor 8 as a magnetic field intensity distribution captured by all the magnetic sensors, or printed out on a color printer 9. For example, the screen displayed on the color monitor 8 is as shown in FIG.

In the figure, reference numeral 40 indicates the entire display screen. The display screen 40 includes a divided screen 41 corresponding to the arrangement surface of the magnetic sensors S _{1 to} Sm in the magnetometer 1, and each of the magnetic sensors S ₁ to S _m.
A split screen 42 shows an enlarged waveform based on the magnetic field measured by the S _m, a split screen 43 showing a magnetic field intensity distribution captured by the total magnetic sensor is displayed.

The divided screen 41 includes magnetic sensors S _{1 to} S _m
The magnetic field measured by each magnetic sensor is divided into components in three directions and displayed in a waveform at a position 41a corresponding to. Further, on the divided screen 42, the waveform displayed in the divided screen 41 is enlarged and displayed. Further, on the split screen 43, the magnetic field intensity distribution captured by all the magnetic sensors is displayed for each component of the magnetic field in three directions.

The biomagnetic data group obtained by the above-described procedure is immediately removed when a noise component having a predicted size is measured, and is therefore composed of only biomagnetic data without relatively large noise. . Furthermore, by compressing the minute noise included in the biomagnetic data, only the biomagnetic signal based on the bioactive current source in the region of interest is emphasized. By observing the waveform display and the magnetic field intensity display based on the biomagnetic data group, it is possible to accurately grasp the state of the biological activity current source at the site of interest.

<Second Embodiment> In the second embodiment, the schematic configuration of the apparatus is the same as that of the first embodiment shown in FIG. Further, the processes in steps S1 to S6 of the first embodiment are common, and thus description thereof will be omitted. Hereinafter, when an invalid biomagnetic data group is obtained in step S3 of the first embodiment,
The process of calculating a new determination value based on the invalid biomagnetic data group is defined as step S31, and the process performed in step S31 will be described in detail with reference to the flowcharts of FIGS. This step S31 includes the following steps V1 to V4.

[0035] Each time that is determined to be invalid biomagnetic data group in step V1 (specific magnetic sensor) Step S3, based on the invalid biomagnetic data groups, each living body obtained by the magnetic sensor S ₁ to S _m comparing the magnetic data, and a judgment value L ₁ ~L _m corresponding to each magnetic sensor.
Identifying a magnetic sensor S _x of measuring the biomagnetic data outside determination value L ₁ ~L _m by comparison. The magnetic sensor _Sx and the biomagnetic data are stored in the third memory 7c. In the third memory 7c, the magnetic sensor _Sx is individually stored for each invalid biomagnetic data group. Step V1
Corresponds to the function of the magnetic sensor specifying means of the present invention.

Step V2 (Search for Magnetic Sensor) The data processing section 6 checks whether or not the magnetic sensor _Sx stored in the third memory 7c is specified continuously. At this time, if the same magnetic sensor is specified continuously, the process proceeds to step V3. If the same magnetic sensor has not been identified, the process of step S31 ends.
Here, it was determined whether or not the same magnetic sensor was specified continuously. However, the present invention is not limited to this. For example, if the same magnetic sensor was specified any number of times, the process proceeds to step V3. Is also good.

Step V3 (Calculate New Determination Value) A peak value is determined from the biomagnetic data of the magnetic sensor _Sx . Instead of the magnetic field intensity of the noise of the formula (1) shown in the first embodiment, by substituting this peak value to calculate a new decision value l _x. At step V3, was calculated new decision value l _x based on the peak value, the invention is not limited to this and can also be set, for example the new decision value l _x to infinity.

Step V4 (Rewrite to new determination value) The determination value L of the magnetic sensor _Sx stored in the first memory
The _x, rewrites the new decision value l _x of the magnetic sensor S _x calculated in step V3. Thereafter, the comparison between the biomagnetic data and the determination value in step S3 is performed based on the rewritten determination value in the first memory. Step V2
V4 corresponds to the function of the judgment value rewriting means of the present invention.

By performing the above-described processing, the magnetic sensor specified many times as having deviated from the determination value is recognized as having an abnormality in the magnetic sensor itself. By setting the determination value of the magnetic sensor to a larger value, invalid determination based on biomagnetic data measured by the magnetic sensor can be eliminated. Therefore, when there is no abnormality in the measured biomagnetism itself, the biomagnetism can be treated as an effective biomagnetism data group at any time, and efficient biomagnetism measurement can be performed. Furthermore, the magnetic sensor in which the abnormality has occurred can be found at an early stage.

[0040]

As is clear from the above description, according to the biomagnetism measuring apparatus according to the first aspect of the present invention, every time the biomagnetism is measured from the region of interest of the subject, the biomagnetism is measured for each magnetic sensor. Get the data. Since the determination value calculated in advance according to the sensitivity of each magnetic sensor is compared with the biomagnetic data obtained for each magnetic sensor, sudden noise can be accurately removed. The effective biomagnetic data for each magnetic sensor, that is, the effective biomagnetic data group is sequentially stored in the second storage means. This second
The averaging process is performed on the basis of a predetermined number of valid biomagnetic data groups in the storage means, so that a biomagnetic data group in which only the biomagnetism from the bioactivity current source in the region of interest of the subject is obtained. Can be. From the biomagnetic data group, it is possible to accurately grasp the size, direction, and the like of the biological activity current source in the region of interest of the subject. Further, the burden on the patient is reduced and the throughput can be improved as compared with the case where measurement is performed again due to the influence of noise or the like after the collection of the biomagnetic data group.

According to the second aspect of the present invention, a magnetic sensor that has obtained invalid biomagnetic data from an invalid biomagnetic data group is detected. When the detected magnetic sensor is also detected from other invalid biomagnetic data, the determination value of the magnetic sensor is rewritten to a new determination value. Since the validity is determined based on the new determination value, the determination of “invalid biomagnetic data group” due to the abnormality of the magnetic sensor itself can be avoided. Therefore, the inspection time for measuring the biomagnetism can be shortened, and the abnormality of the device can be found at an early stage.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a biomagnetism measuring device according to first and second embodiments.

FIG. 2 is a flowchart illustrating a processing procedure performed by the biomagnetism measuring apparatus according to the first embodiment.

FIG. 3 is a schematic diagram showing valid biomagnetic data and invalid biomagnetic data.

FIG. 4 is a display example of a biomagnetic data group in the biomagnetic measurement apparatuses according to the first and second embodiments.

FIG. 5 is a flowchart illustrating a processing procedure performed by the biomagnetism measuring apparatus according to the second embodiment.

FIG. 6 is a flowchart showing a processing procedure of step S31 performed by the biomagnetism measuring device of the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Multi-channel SQUID sensor 1a ... Dewar 4 ... Data conversion part 5 ... Data collection part 6 ... Data processing part 7a ... First memory 7b ... Second memory 4 ... Data conversion part

Claims (2)

[Claims] 1. A biomagnetism generated from a bioactivity current source in a region of interest of a subject is individually measured by a plurality of magnetic sensors, and a plurality of biomagnetic data groups obtained by repeating the measurement many times are obtained. A biomagnetism measuring apparatus that performs an averaging process on the biological activity data source and grasps the state of the biological activity current source based on the biomagnetic data group after the averaging process.
Individual determination value calculation means for calculating a determination value for determining whether the biomagnetic data individually measured for each magnetic sensor is valid or invalid based on the sensitivity of each magnetic sensor; First storage means for storing a determination value for each magnetic sensor calculated by the individual determination value calculation means; (c) a determination value for each magnetic sensor stored in the first storage means; Comparing and judging whether the biomagnetic data group is valid or invalid by comparing biomagnetic data measured for each sensor; and (d) valid biomagnetism judged by the comparing and judging means. (E) second storage means for storing a data group;
A biomagnetism measuring apparatus, comprising: averaging processing means for performing averaging processing on a predetermined number of valid biomagnetic data groups in the second storage means. 2. The biomagnetism measuring apparatus according to claim 1, wherein (f) the biomagnetism data deviating from the determination value is determined based on a plurality of invalid biomagnetic data groups determined by the comparison determination means. Magnetic sensor specifying means for specifying the measured magnetic sensor for each of the invalid biomagnetic data groups; and (g) invalid magnetic sensors for each of the invalid biomagnetic data groups specified by the magnetic sensor specifying means. When the same magnetic sensor is specified for each biomagnetic data group, a judgment value rewriting means for rewriting the judgment value in the first storage means corresponding to the magnetic sensor to a larger judgment value is provided. A biomagnetism measuring device, characterized in that: