JPH10127592A - Biomagnetism measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biomagnetism measuring device capable of quickly and objectively obtaining the time living body activity current is assumed to be generated. SOLUTION: A micromagnetic field generated together with living body activity current in a subject M is detected by magnetic flux meter S1-Sm with plural magnetism detecting elements and is inputted into a symbol waveform preparing part 3a via a data collecting unit 2. The symbol waveform preparing part 3a calculates differences between the maximum value and the minimum value at each time from each obtained time-magnetic field intensity waveform to make the difference as a symbol waveform, an automatic analysis latency determining part 3b calculates a time to exceed a prescribed value of an obtained symbol waveform as the analysis latency, and a magnetic field analyzing part 3c calculates information on a living body activity current source from magnetic field data at the analyzing latency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biomagnetic measurement for measuring a minute magnetic field generated with a living body current source in a subject and obtaining the living body current source in the subject based on the measurement data. Related to the device.

[0002]

2. Description of the Related Art With the development of superconducting device technology in recent years, SQUIDs (Superconducting Quantum Interferen
A biomagnetic measurement device using a high-sensitivity magnetometer called ce Device) is being put to practical use as one of medical diagnostic devices, and is expected to be useful for elucidating brain functions and diagnosing cardiovascular diseases. .

In this biomagnetism measuring apparatus, magnetic field data generated by light or electrical stimulation applied to a subject is measured by a magnetometer composed of a plurality of magnetic detecting elements, and based on the measured magnetic field data, for example, The position, direction, and size of the bioactive current source in the coordinate system based on the magnetometer are estimated by the least square method or the minimum norm method (Jukka Sarvas "Basic mathematical and election").
romagnetic conceptsf the biomagnetic inverse probl
em ", Phys. Med. Biol., 1987, vol.32, No.1, 11-22,
Printed by the UK).

[0004] In such a case, the magnetic field to be measured includes an induced brain magnetic field based on a biological activity current source generated by light or electrical stimulation, and a spontaneous spontaneous activity based on a biological activity current source generated without applying a stimulus or the like. There are magnetoencephalograms, but to measure them, apply the above least squares method or minimum norm method to the detection data obtained by the magnetometer at the time when the biological activity current is strongly generated in the subject Need to be done.

Conventionally, a method using a so-called goodness-of-fit curve has been used to obtain information on a biological activity current source at the time, and a time-magnetic field waveform has been determined for each magnetic sensing element of a magnetometer to specify the time. A method of displaying on the same time axis is adopted. Here, the goodness-of-fit is an index indicating how reliable the current source position analyzed by the least square method using the magnetic field intensity data of all the magnetic detection elements at a certain time is: Is required.

The goodness-of-fit value = (1-Σ (Bmi-B
ci) 2 / Σ (Bmi) 2) × 100 Bci: magnetic field intensity considered to be detected by the i-th magnetic detecting element when a predetermined biological activity current source is assumed to be located at the analyzed position Bmi: i-th magnetic field The strength of the magnetic field actually measured by the detector and the goodness-of-fit curve show the goodness-of-fit
The value (%) is plotted for each time, and at a time when the value is close to 100%, the dipole property of the actual current value is high.

[0007]

However, when a so-called goodness-of-fit curve is used, it is possible to judge easily and objectively at which time the dipole property is high. Since the least squares method, the minimum norm method, and the like have to be applied, the calculation requires an enormous amount of time, and it is not possible to obtain necessary information on a living activity current source in real time simultaneously with data collection.

On the other hand, the method of displaying the waveforms of all channels on the same time axis simply displays the detection data of each magnetic sensing element, so that real-time display is possible. It is difficult to objectively and automatically specify the time at which the life activity current is strongly generated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a biomagnetism measuring device capable of objectively obtaining a time at which a biological activity current source is considered to have occurred in a short time. And

[0010]

In order to achieve the above-mentioned object, the present invention is directed to detecting a minute magnetic field generated by a bioactive current source in a subject with a magnetometer provided with a plurality of magnetic sensing elements. A biomagnetism measurement apparatus for obtaining a biological activity current source in the subject based on the detection data, wherein each time-magnetic field strength waveform obtained by each of the plurality of magnetic detection elements is used to calculate the entire waveform group. It is characterized by comprising a symbol waveform creating means for creating a symbol waveform indicating waveform characteristics with respect to the time axis.

The symbol waveform creating means calculates a difference between a maximum value and a minimum value at each time from each time-magnetic field intensity waveform, and determines a difference between the maximum value and the minimum value at each time as the symbol waveform. It is characterized by the following.

The symbol waveform creating means obtains a sum of absolute values of the time-magnetic field strength waveforms at each time,
The sum of the absolute values for each time is created as the symbol waveform.

[0013] The biomagnetism measuring apparatus further includes a comparing means for determining a time when the symbol waveform created by the symbol waveform creating means exceeds a predetermined threshold.
Magnetic field analyzing means for obtaining a biological activity current source in the subject at the time obtained by the comparing means.

[0014]

1 to 5 show an embodiment of the present invention.
It will be described based on. FIG. 1 is a schematic configuration diagram of a biomagnetism measuring apparatus according to one embodiment of the present invention. In the figure, a sensor unit 1 includes a pickup coil and an SQUA
The magnetometers S1 to Sm each including a plurality of high-sensitivity magnetic detection elements each including an ID are housed together with a refrigerant in a Duer, and are used to measure a biological activity current source. Deployed in close proximity to Data collection unit 2
Indicates the biomagnetic field measured by the magnetometers S1 to Sm and each oscillation coil
The AC magnetic field data generated from C1 to Cn is A / D converted and output to the symbol waveform creation unit 3a and the automatic analysis latency determination unit 3b of the computer 3.

The oscillating coils C1 to Cn are located at the base of the nose, under both ears, etc.
Attached to a characteristic part in identifying the subject M, for example, a coil formed by printing metal on a substrate formed of an insulator such as a ceramic plate, or a metal wire on a bobbin. The coil formed by winding is used and driven by the current supply unit 8.

The stimulus applying section 9a is driven by the stimulator 9, and applies light or electric stimulus to the subject M when measuring the induced magnetoencephalogram.

The computer 3 mainly analyzes the measured magnetic field data and controls the operation of the current supply unit 8 and the stimulator 9. The computer 3 is mainly composed of a symbol waveform generator 3a and an automatic analysis latency determiner 3b. , A magnetic field source analysis unit 3c, and an acquisition control unit 3d.

The symbol waveform creating section 3a includes the magnetometers S1 to Sm
From the magnetic field intensity data detected by the data collection unit 2 and detected in the above, a symbol waveform indicating the waveform characteristics of the entire waveform group with respect to the time axis is created. The symbol waveform is, for example, the difference between the maximum value and the minimum value at each time of each time-magnetic field strength waveform obtained from the magnetometers S1 to Sm, and the sum of the absolute values at each time of each time-magnetic field strength waveform. It is obtained by plotting at each time, but here, the former will be considered.

Based on the symbol waveform created by the symbol waveform creation unit 3a, the analysis latency automatic determination unit 3b determines the time when the biological activity current source is strongly generated in the subject, that is,
Determine the so-called analysis latency.

The magnetic field source analysis unit 3c uses the magnetic field data at the analysis latency determined by the analysis latency automatic determination unit 3b among the magnetic field data output from the data collection unit 2 to generate a biological signal for the magnetometers S1 to Sm. While calculating the relative position of the active current source, using the magnetic field data from each oscillation coil C1 ~ Cn, each oscillation coil C1 ~ for the magnetometer S1 ~ Sm.
Calculate the relative position of Cn.

The relative positions of the obtained oscillating coils C1 to Cn are associated with specific points of the subject M, such as the root of the nose on the MRI image read from the image storage unit 4 and both ears.
The measured biological activity current source is displayed on the monitor 6 in a superimposed manner on the MRI image based on the positional relationship associated here, and, if necessary, an external memory 5 such as a MOD (magneto-optical disk). Or output to the printer 7.

The acquisition control unit 3d controls the current supply unit 8 and also controls the stimulator 9 to apply light, sound, and electrical stimulation to the subject M when measuring the biological activity current source. Do it.

Next, the operation of the present invention when measuring the induced magnetoencephalogram will be described with reference to the flowchart of FIG.

First, in order to generate an induced brain magnetic field, the collection controller 3d causes the stimulator 9a to apply light, sound, electricity or other stimuli to the subject M via the stimulator 9 ( S1).

On the other hand, the symbol waveform creating section 3a and the automatic analysis latency determining section 3b provide the magnetometer S1 before and after the stimulus application.
The magnetic field data detected at ~ Sm is taken in via the data collection unit 2 (S2). The magnetic field data obtained here is each time-magnetic field intensity waveform obtained by the magnetometers S1 to Sm, as shown in FIG. 4A.

When the acquisition of the magnetic field data is completed, the symbol waveform creating section 3a creates a symbol waveform indicating the waveform characteristics of the entire waveform group with respect to the time axis from a series of magnetic field data acquired from the data collection unit 2 (S3). ).

Here, a specific symbol waveform calculation process in the symbol waveform creation section 3a will be described with reference to the flowchart of FIG.

FIG. 4A shows a time-magnetic field strength waveform obtained for each of the magnetometers S1 to Sm, and FIG. 4B is an enlarged view of one of the obtained time-magnetic field strength waveforms. First, the first time t0 at which a symbol waveform is to be created, for example, the collection start time of the magnetic field data is specified (S11), and the magnetic field strength values are obtained for all the magnetic field data obtained by the magnetometers S1 to Sm at the time t0. (S12), the maximum value and the minimum value are obtained (S13). When the maximum value and the minimum value of the magnetic field strength obtained by the magnetometers S1 to Sm at the time t0 are obtained, the difference Δ between the maximum value and the minimum value is obtained and plotted on a monitor or the like (S14). Then, the next time is specified (S1
5) By repeating these operations until the end of data collection te, the symbol waveform shown in FIG. 4C is obtained.

The symbol waveform created by the symbol waveform creation section 3a is output to the analysis latency automatic determination section 3b to determine the analysis latency (S4). The determination of the analysis latency is, for example,
As shown in FIG. 5, the difference Δ between the maximum value and the minimum value of the magnetic field strength is compared with a predetermined threshold value (ΔThershold), and the obtained symbol waveform is compared, and the time when the symbol waveform exceeds the threshold value is determined. The analysis latency may be used.

Note that the threshold value (ΔThershol
d) may be input by the operator to the analysis latency automatic determination unit 3b as appropriate, or may be determined as a value of 70% to 90% of the maximum value of the symbol waveform.

When the analysis latency is determined by the analysis latency automatic determination unit 3b, the determined analysis latency and magnetic field data obtained at the analysis latency are output to the magnetic field source analysis unit 3c, and the analysis latency is determined. Magnetic field analysis of the magnetic field data at each time is performed, and the relative position of the biological activity current source with respect to the magnetometers S1 to Sm at each time is calculated using the well-known least square method, the minimum norm method, or the like (S5).

Next, the biological activity current source thus obtained is superimposed on an image such as an MRI.

First, the oscillation coils C1 to Cn are attached to appropriate positions on the head surface of the subject M, for example, the nose, the left and right ears, and the like, and the collection control unit 3 is attached to the oscillation coils C1 to Cn.
d supplies an alternating current through the current supply unit 8 (S6).

Then, the analysis latency automatic determination unit 3b collects the alternating magnetic field generated from the oscillation coils C1 to Cn detected by the magnetometers S1 to Sm as magnetic field data via the data collection unit 2 (S7). The magnetic field source analysis unit 3c calculates the relative positions of the oscillation coils C1 to Cn with respect to the magnetometers S1 to Sm using a known least square method or a minimum norm method (S8). The obtained relative positions of the oscillation coils C1 to Cn are stored in the image storage unit 4.
Is associated with a specific point of the subject M, such as the root of the nose or the lower part of the ears, on the MRI image read out from the MRI image, and the obtained information on the biological activity current source is based on the positional relationship associated with this. It is displayed on the monitor 6 so as to overlap the MRI image (S
9). These are appropriately stored in an external memory 5 such as a MOD.
And output to the printer 7.

In the above-described embodiment, the case where the symbol waveform is formed from the difference between the maximum value and the minimum value of the magnetic field data obtained by the magnetometers S1 to Sm at each time has been described. The symbol waveform may be formed by plotting the sum of the absolute values of the magnetic field data obtained through Sm on the time axis. In such a case, the sum of the absolute values of the magnetic field data obtained by the magnetometers S1 to Sm at each time may be the sum of the absolute values of the differences between the predetermined value and the magnetic field data.

In order to determine the analysis latency from the symbol waveform, as described above, a predetermined threshold value (ΔThershold) is compared with the obtained symbol waveform, and the time when the symbol waveform exceeds the threshold value is determined. May be the analysis latency.

In the present embodiment, the analysis latency is automatically calculated in the analysis latency determining unit 3b. However, the present invention is not limited to this, and the analysis latency may be calculated from the symbol waveform displayed on the monitor 6. The operator may appropriately determine the analysis latency.

[0038]

According to the present invention, the time at which the biological activity current source is considered to have been generated can be objectively determined in a short time and objectively from the magnetic field data from the subject. It is possible to ask.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a biomagnetism measuring apparatus according to the present invention.

FIG. 2 is a diagram showing an operation for measuring a life activity current source.

FIG. 3 is a diagram illustrating an operation for determining an analysis latency.

FIG. 4 is a diagram showing measured magnetic field data and symbol waveforms.

FIG. 5 is a diagram illustrating an analysis latency specified from a symbol waveform.

[Explanation of symbols]

 M Subject S1 to Sm Magnetometer C1 to Cn Oscillation coil 1 Sensor unit 2 Data collection unit 3 Computer 3a Symbol waveform formation unit 3b Analysis latency automatic determination unit 3c Magnetic field source analysis unit 3d Collection control unit 4 Image storage unit 5 External memory 6 Monitor 7 Printer 8 Power supply unit 9 Stimulator 9a Stimulation unit

Claims (4)

[Claims] 1. A micro-magnetic field generated by a bio-activity current source in a subject is detected by a magnetometer having a plurality of magnetic detecting elements, and a bio-activity current source in the subject is detected based on the detection data. A biomagnetic measurement apparatus for obtaining the following: a symbol waveform creating means for creating a symbol waveform indicating a waveform characteristic with respect to a time axis of the entire waveform group from each time-magnetic field intensity waveform obtained by each of the plurality of magnetic detection elements. A biomagnetic measurement device characterized by the following. 2. The symbol waveform creation means calculates a difference between a maximum value and a minimum value at each time from the time-magnetic field intensity waveform, and calculates a difference between the maximum value and the minimum value at each time with the symbol waveform. The biomagnetic measurement apparatus according to claim 1, wherein the biomagnetism measurement apparatus is created as: 3. The symbol waveform creating means finds the sum of absolute values of the plurality of time-magnetic field strength waveforms at each time, and creates the sum of the absolute values at each time as the symbol waveform. The biomagnetic measurement device according to claim 1. 4. A comparison means for determining a time when the symbol waveform created by the symbol waveform creation means exceeds a predetermined threshold, and a bioactivity current source in the subject at the time determined by the comparison means. The biomagnetic measurement apparatus according to any one of claims 1 to 3, further comprising: a magnetic field analysis unit that obtains the following.