JPH105186A - Biomagnetism measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biomagnetism measuring device which can accurately estimate a living body action current source in a short test time by effectively using measuring magnetic field data by removing influence by a noise in synchronism with heartbeats. SOLUTION: A prescribed stimulus is imparted to an examinee B through a stimulus applicator 8, and before and after it, for example, biomagnetism measuring data from a SQUID fluxmeter 3 and electrocardio-measuring data from an electrocardio- measuring device 1 are respectively obtained as single gathering unit for a time of about 100 msec. After the data are obtained, a coincidence degree of obtained both data is compared, and when the coincidence degree of both data is high, the obtained biomagnetism measuring data is rejected as receiving influence of a noise by heartbeats, and when the coincidence degree is low, it is preserved as receiving no noise. These operation is repeatedly performed, and after they finish by the prescribed number of times, the preserved biomagnetism measuring data is additively averaged with every data gathering unit, and a generating position of a living body action current source to the SQUID fluxmeter 3 is calculated by a widely known minimum square method and a minimum norm method or the like on the basis of data obtained by an additive average.

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. .

[0003] In this biomagnetism measuring apparatus, the position, direction, size, etc., of a biological activity current source in a coordinate system based on a magnetometer are determined based on measured magnetic field data by, for example, a least square method or a minimum norm method. Is estimated (Ju
kka Sarvas "Basic mathematical and electromagnetic
concepts of the biomagnetic inverseproblem ", Phy
s. Med. Biol., 1987, vol.32, No.1, 11-22, Printed
by theUK).

[0004]

However, since the biomagnetic field to be measured is extremely weak, the magnetic field noise caused by the body movement of the subject hinders accurate data analysis, and is particularly synchronized with the heartbeat. The effect of the noise is large. In such a case, the position, orientation, size, and the like of the biological activity current source have a great adverse effect on the estimation result, and the measurement must be repeated several times in advance of the occurrence of an error, and one test time is required. There is a problem that the length of time is prolonged and the burden on the patient as the subject becomes excessive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and eliminates the influence of noise synchronized with the heartbeat, thereby effectively utilizing measured magnetic field data and achieving accurate biological activity in a short examination time. An object of the present invention is to provide a biomagnetism measurement device capable of estimating a current source.

[0006]

In order to achieve the above object, the present invention measures a minute magnetic field generated from a biological activity current source in a subject, and based on the measured data, detects a living body in the subject. In a biomagnetism measurement device for determining an active current source, a magnetometer for measuring a minute magnetic field generated from the subject, an electrocardiograph for measuring an electrocardiographic waveform of the subject, and magnetic field data measured by the magnetometer. And a data processing unit for determining the degree of coincidence with the electrocardiographic data measured by the electrocardiograph, and recognizing the magnetic field data as defective data when the degree of coincidence is high.

[0007] The data processing device is characterized in that, of the measured magnetic field data, only data of a portion recognized as defective data is rejected, and a biological activity current source is estimated based on the remaining magnetic field data. I do.

[0008] The data processing device uses measurement data obtained each time a predetermined stimulus is applied to a subject as one collection unit, and rejects a data collection unit including defective data when the data is defective. Features.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of a biomagnetism measuring apparatus according to an embodiment of the present invention. The electrocardiographic signal is output to the computer 7 after being subjected to amplification, noise processing and the like in the electrocardiographic measuring device 1.

The SQUID magnetometer 3 comprises a plurality of magnetic sensors (S1 to Sm) including the SQUID, is cooled to a very low temperature by the liquid helium in the liquid helium dual 4, and is maintained in a superconducting state. The micro magnetic field generated from the head is detected and output to the computer 7 via the SQUID drive circuit 5 and the A / D converter 6.

The computer 7 compares the magnetic field data detected by the SQUID magnetometer 3 with the electrocardiographic data obtained from the electrocardiograph 1, and obtains the degree of coincidence between the two to determine the quality of the detected magnetic field data. Is determined, and arithmetic processing for obtaining the biomagnetic source for the SQUID magnetometer 3 is performed using only good magnetic field data.

In the biomagnetic measurement, there are two types of measurement methods, that is, a spontaneous magnetic field measurement and an induced magnetic field measurement.
Is applied to the subject B via the.

Next, the operation of the present invention will be described with reference to the flow chart showing the operation of the computer 7 shown in FIG.

First, a predetermined stimulus is given to the subject B via the stimulus giving device 8 (S1), and 100 m before and after that.
The biomagnetic measurement data is acquired from the SQUID magnetometer 3 and the electrocardiogram measurement data is acquired from the electrocardiograph 1 as a collection unit for about sec (S2, S3).

After the data is obtained, the degree of coincidence between the obtained data is compared (S4). Here, there are various methods for comparing the degree of coincidence between the two data. For example, a value of γ obtained based on the following equation can be used as an index.

Γ = ΣCi · mi / ((ΣCi 2) 1/2 ·
(Σmi 2) 1/2) Ci: electrocardiographic data at time i mi: biomagnetic measurement data at time i Σ: addition of data obtained in one collection unit where γ is a correlation coefficient and −1 This is an index indicating that the closer the absolute value is to 1, the higher the degree of coincidence between the waveforms of the two measurement data is.

For example, if the obtained data has the relationship shown in FIG. 3A, the correlation between the two data is small, and γ is
Although it is far from 1, if the relationship shown in FIG. 3B is satisfied, the correlation between the two data is high, and γ is close to 1.

In this way, the correlation between the two measurement data is obtained,
If γ is larger than a predetermined threshold value, for example, 0.9, the degree of coincidence between the two measurement data is high, and the obtained biomagnetic measurement data is regarded as being affected by the noise due to the heartbeat, and one of the biomagnetic measurement data The collection unit is rejected (S6), and if γ is smaller than the predetermined threshold, it is determined that noise has not been received, and the obtained biomagnetic measurement data is stored (S6).
7).

The presence / absence of the noise determination based on the index γ is determined for the biomagnetic measurement data obtained by all the magnetic sensor elements (S 1 to Sm) included in the SQUID magnetometer 3. If it is determined that the data is also affected by noise, all data including data obtained by other magnetic sensor elements is rejected.

These operations are repeated (S
1 to S7), after completion of the predetermined number of times, the stored biomagnetic measurement data is added and averaged for each data collection unit, and the SQUID magnetometer 3 is obtained based on the added and averaged data by a well-known least square method or a minimum norm method. The generation position of the biological activity current source with respect to is calculated (S8).

In the above-described embodiment, the index γ indicating the correlation between the two data is used for comparing the degree of coincidence of the two obtained data. However, the present invention is not limited to this. If a value touches in the plus direction and the minus direction near the same time as the electrical data, it may be determined that the biomagnetic measurement data has received noise due to the heartbeat, and the data may be discarded.

[0022]

According to the present invention, at the time of biomagnetism measurement, only biomagnetic measurement data which causes an error affected by noise due to the heartbeat is rejected, and only accurate biomagnetism measurement data without noise is rejected. , The accurate estimation of the biological activity current source can be performed in a short examination time, and the burden on the patient is greatly reduced.

[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 flowchart showing a data processing operation for estimating a life activity current source according to the present invention.

FIG. 3 is a diagram showing an example of measured biomagnetic measurement data and electrocardiogram data.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electrocardiographic measuring device 2 electrocardiographic pat 3 SQUID magnetometer 4 liquid helium dual 5 SQUID drive circuit 6 A / D converter 7 computer 8 stimulating device

Claims (1)

[Claims] 1. A biomagnetism measuring apparatus for measuring a micro magnetic field generated from a biological activity current source in a subject and obtaining a biological activity current source in the subject based on the measurement data. A magnetometer for measuring a minute magnetic field, an electrocardiograph for measuring the electrocardiographic waveform of the subject, and a degree of coincidence between the magnetic field data measured by the magnetometer and the electrocardiographic data measured by the electrocardiograph. And a data processing means for recognizing the magnetic field data as defective data when the degree of coincidence is high.