JP2020141911A - Magnetocardiograph - Google Patents

Abstract

To perform positioning on a magnetic sensor in a short period of time and accurately.SOLUTION: A magnetocardiograph (10) comprises a bed 35, a magnetic sensor 31, and a computer 20. The bed 35 and the magnetic sensor 31 are installed in a magnetic shield room (100) for blocking a magnetic field from the outside. The magnetic sensor 31 detects cardiac magnetism, a magnetic field generated by electric activity of a cardiac muscle of a subject lying on the bed 35. The computer 20 is installed outside the magnetic shield room and controls the magnetic sensor 31. The computer 20 includes a subject position evaluation/control module 42 for calculating and outputting a deviation amount of the bed 35 from a difference between a position of an excitation part identified from a cardiac magnetism signal of one heart beat detected by the magnetic sensor 31 and a position of an interest part on which cardiac magnetism measurement is performed.SELECTED DRAWING: Figure 2

Description

The present invention relates to a magnetocardiograph.

A magnetocardiograph is known as a device for non-invasively measuring the myocardial activity of the heart. The magnetocardiograph measures the distribution of a weak magnetic field generated from the human heart using a superconducting QUantum Interference Device (SQUID) sensor, which is a magnetic sensor. Then, the position of the action current inside the heart is estimated from the measurement result, and the distribution is imaged.

In the measurement by the magnetocardiography, the subject is laid on the bed in the magnetic shield room where the magnetocardiography is installed. Then, the subject is moved under the dewar where the magnetic sensor is installed so that the positional relationship between the subject's heart and the magnetic sensor becomes appropriate, that is, the magnetocardiographic signal to be measured is in the measurement range. Adjust so that it is not outside. At that time, the operator confirms the xiphoid process on the chest of the subject with a fingertip or the like, and adjusts the position so as to overlap the position of the predetermined magnetic sensor.

As a technique for measuring a magnetic field of this type, there is known a technique for accurately detecting the distribution of the magnetic vector of a subject without being affected by the body shape of the subject (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2017-000354

In the above-mentioned adjustment technique, since there are individual differences in the physique and the position of the heart, there is a risk that the magnetocardiographic signal deviates from the measurement range or the most activated part deviates from the measurement range.

In this case, the determination as to whether or not the measurement is appropriate cannot be confirmed in advance until the operator confirms the magnetocardiographic waveform on the screen of the operating personal computer installed outside the shield room. If the measurement is found to be inappropriate, the operator must temporarily cancel the measurement preparation state, return to the magnetic shield room, and realign the subject, which reduces work efficiency. However, there is a problem that it takes time.

An object of the present invention is to provide a technique capable of aligning a magnetic sensor with high accuracy in a short time.

The above and other purposes and novel features of the present invention will become apparent from the description and accompanying drawings herein.

A brief outline of the typical inventions disclosed in the present application is as follows.

That is, a typical magnetocardiogram includes a bed, a detector, and a calculator. The bed and the detector are installed in a magnetic shield room that blocks the magnetic field from the outside. The detection unit detects the magnetocardiography, which is a magnetic field generated by the electrical activity of the myocardium of the subject lying on the bed.

The computer is installed outside the magnetic shield room and controls the detector. The computer has a control unit that calculates the amount of deviation of the bed from the difference between the position of the excitement portion specified from the magnetocardiographic signal for one heartbeat detected by the detection unit and the position of the interest portion for magnetocardiographic measurement.

Among the inventions disclosed in the present application, the effects obtained by typical ones will be briefly described as follows.

The measurement site of the subject and the magnetic sensor can be adjusted accurately in a short time.

Explanatory drawing which shows an example of the structure in the magnetocardiography. The block diagram which shows an example of the structure in the magnetocardiography of FIG. The explanatory view which shows an example of the structure in the bed which is raised and lowered by the pump unit of FIG. An explanatory view showing an example of a configuration in a magnetic sensor array included in the magnetocardiogram of FIG. The explanatory view which shows an example of the structure in the magnetic sensor of FIG. Explanatory drawing which shows another example in the magnetic sensor of FIG. An explanatory view showing an example of the positional relationship between the magnetic sensor array of FIG. 4 and the subject. A flowchart showing an example of a comparative technique in magnetocardiographic measurement using a magnetocardiogram. The flowchart which shows an example of the magnetocardiography measurement by the magnetocardiography of FIG. Explanatory drawing which shows an example of a human heartbeat waveform. An explanatory view showing an example of a setting screen displayed on the display of the magnetocardiogram of FIG. 1. An explanatory view showing an example of a grid map waveform displayed on a display of the magnetocardimeter of FIG. 1. Explanatory drawing which shows the display example of the isomagnetic field diagram in the magnetocardiography of FIG. Explanatory drawing which shows an example of information display by the magnetocardiography of FIG.

In all the drawings for explaining the embodiment, the same members are designated by the same reference numerals in principle, and the repeated description thereof will be omitted.

Hereinafter, embodiments will be described in detail.

<Example of appearance of magnetocardiograph>
FIG. 1 is an explanatory diagram showing an example of a configuration in a magnetocardiogram according to the present embodiment.

As shown in FIG. 1, the magnetocardiograph 10 includes a measurement control unit 11, an automatic replenishment device 12, a dewar 13, a bed unit 14, a projector 15, and the like. The measurement control unit 11, the automatic replenishment device 12, and the projector 15 are installed outside the magnetic shield room 100 that shields magnetic lines from the outside. The dewar 13 and the bed portion 14 are installed in the magnetic shield room 100 in order to eliminate the influence of environmental magnetic noise.

The measurement control unit 11 is composed of a computer 20, a keyboard 21, a display 22, a printer 23, a mouse 24, a FLL (Flux Locked Loop) circuit 25, an AFA circuit (amplifier filter amplifier) 26, and a measurement control circuit 27. .. The computer 20 is composed of, for example, a personal computer or the like, and executes measurement of a biomagnetic signal, data display analysis, and the like.

The keyboard 21, the display 22, the printer 23, the mouse 24, the FLL circuit 25, the AFA circuit 26, and the measurement control circuit 27 are each connected to the computer 20. The keyboard 21 and the mouse 24 input information and the like.

The display 22 displays the result of data display analysis by the computer 20 and various information input from the keyboard 21, mouse 24, and the like. The printer 23 outputs the contents displayed on the display 22 and the like. The printer 23 is capable of color printing, black-and-white printing, or color printing and black-and-white printing.

The display 22 may be provided with a touch panel. Further, the mouse 24 may be a pointing device such as a trackball or a jostic.

The bed unit 14 includes a bed 35 and a bed control unit 36 shown in FIG. At the time of measurement, the subject 2 is measured while lying on his / her back or lying down on the bed 35. The bed control unit 36 controls the position of the bed 35 and the like.

The subject 2, that is, the human chest measurement surface, is curved and tilted, but is made substantially parallel for the sake of simplicity. Therefore, the chest measurement surface is assumed to be substantially parallel to the upper surface of the bed 35, the body axis direction is the y-axis, and the subject 2 is parallel to the xy plane with the left-right direction as the x-axis. To do. Further, the direction from the floor surface to the ceiling of the magnetic shield room 100 is defined as the z-axis.

The dewar 13 is, for example, a highly insulated container having a vacuum layer structure, and is arranged so as to be located above the chest of the subject 2. Inside the dewar 13, liquid helium that cools the magnetic sensor array 30 and the magnetic sensor array 30 shown in FIG. 2, which will be described later, to a superconducting state is contained. The automatic replenishment device 12 replenishes the dewar 13 with liquid helium.

<Example of magnetocardiographic block diagram>
FIG. 2 is a block diagram showing an example of the configuration in the magnetocardiogram 10 of FIG.

The computer 20 includes a control module 40, a data acquisition module 41, a subject position evaluation / control module 42, and the like. Further, the bed control unit 36 is composed of a bed position measurement unit 45 which is a position adjustment control unit, a bed position control unit 46 which is also a position adjustment control unit, a pump unit 47, and a simple operation unit 48. Further, the bed position measurement unit 45, the bed position control unit 46, and the pump unit 47 constitute a position adjustment control unit.

The magnetic sensor 31, which is a detection unit, is connected to the FLL circuit 25. The FLL circuit 25 drives the magnetic sensor 31 shown in FIG. 5 provided in the dewar 13 described later (magnetic field lock / unlock operation for the magnetic sensor).

The AFA circuit 26 comprises an input amplifier, a filter, and an output amplifier, and amplifies and filters the output of the magnetic sensor 31. The measurement control circuit 27 controls the state switching of the FLL circuit 25, the amplification factor of the AFA circuit 26, the setting of the filter frequency, and the like based on the control of the control module 40.

The data collection module 41 files the measurement data output from the AFA circuit 26. The subject position evaluation / control module 42 evaluates the measurement data filed by the data collection module 41. Specifically, the subject position evaluation / control module 42 evaluates in real time how far the subject is from the optimum position for measurement based on the measurement data.

The subject position evaluation / control module 42 outputs the evaluation result to the display 22. The display 22 displays the input evaluation result together with the measurement data. The simple operation unit 48 is provided in the magnetic shield room 100. The simple operation unit 48 is connected to the computer 20 and instructs the computer 20 to prepare for measurement (magnetic field lock), release the measurement preparation (magnetic field unlock), and start measurement.

The bed position control unit 46 controls the drive of the pump unit 47. The pump unit 47 is composed of, for example, a hydraulic pump, and moves the bed 35 so that the subject position is the optimum position.

The bed position measuring unit 45 measures the position of the bed 35 and outputs it as position information. Based on the evaluation result, the subject position evaluation / control module 42 outputs a command (position adjustment signal) so that the position of the top plate of the bed 35, that is, the position of the subject is optimized. The bed position control unit 46 moves the bed 35 so that the subject position becomes the optimum position based on the command and the position information output from the bed position measurement unit 45.

<Example of pump unit and bed configuration>
FIG. 3 is an explanatory view showing an example of the configuration of the bed 35 that is raised and lowered by the pump unit 47 of FIG.

As shown in the figure, a cylinder 49 that is raised and lowered by the pump unit 47 is installed under the top plate of the bed 35. A cylinder 51 operated by a manual lever 50 is provided in the flow path connecting the pump unit 47 and the cylinder 49.

When the pump unit 47 is not used, the bed 35 can be raised and lowered by operating the manual lever 50. The bed 35 may be configured to move not only in the ascending / descending direction but also in the body axis direction and the horizontal direction perpendicular to the body axis by the hydraulic assist of the pump unit 47.

As described above, the bed position measuring unit 45 measures the position of the bed 35, that is, the x, y, and z coordinates. Then, the subject position evaluation / control module 42 of the computer 20 outputs a command to the bed position control unit 46 so that the position of the bed 35 is optimized based on the measured value and the evaluation result. As a result, the subject is automatically set to the optimum position.

Further, the x, y, and z coordinates measured by the bed position measuring unit 45 are displayed inside the magnetic shield room 100 by the projector 15. The operator in the magnetic shield room 100 moves the subject to the optimum position by operating the manual lever 50 based on the display contents of the projector 15. By moving the bed 35 by hydraulic assist, it is possible to reduce the physical burden on the operator when raising and lowering the bed.

<Configuration example of magnetic sensor array>
FIG. 4 is an explanatory diagram showing an example of the configuration of the magnetic sensor array 30 included in the magnetocardiogram 10 of FIG. As shown in FIG. 4, the magnetic sensor array 30 is configured by arranging a plurality of magnetic sensors 31 on a matrix on a biological surface, that is, a plane substantially parallel to the xy plane.

Here, the number of magnetic sensors 31 may be arbitrary, but in the example shown in FIG. 4, since the matrix of the magnetic sensors 31 has a configuration of 8 rows × 8 columns, the number of magnetic sensors 31 is determined. 8 × 8 = 64 pieces.

The magnetic sensor 31 is composed of, for example, a superconducting quantum interference element and a detection coil connected to SQUID. The detection coil includes a coil that detects a tangential component of the biomagnetic field, that is, a component that is substantially parallel to the xy plane, and a coil that detects a normal component of the biomagnetic field, that is, a component that is orthogonal to the xy plane. ..

As the coil for detecting the tangential component of the biomagnetic field, for example, two coils whose coil surfaces are oriented in the x direction and the y direction are used. Further, as the coil for detecting the normal component of the biomagnetic field, a coil whose coil surface faces the z direction is used.

Further, the magnetic sensor 31 has a configuration of 8 rows × 8 columns as described above, and is arranged at intervals of, for example, about 25 mm. In the case of this configuration, the entire heart is measured simultaneously at 64 measurement points.

The magnetic sensor 31 is arranged so that its longitudinal direction coincides with the biological surface, that is, the z direction, which is the direction perpendicular to the xy plane. In the example of FIG. 2, the bed surface and the XY surface of the magnetic sensor 31 are parallel to each other, but in order to further improve the measurement accuracy, it is better to bring them closer to the body and tilt them. ..

However, since the human body as the subject is constantly moving, if it is brought into close contact with the human body, the magnetic sensor 31 will move according to the movement of the human body, and there is a risk that high-precision detection will be difficult.

<Configuration example of magnetic sensor>
FIG. 5 is an explanatory diagram showing an example of the configuration of the magnetic sensor 31 of FIG. The magnetic sensor 31 in FIG. 5 shows an example of detecting the normal component Bz of the magnetocardiographic signal. The magnetic sensor 31 is composed of SQUID 60 and a coil portion 61. In FIG. 5, the coil portion 61 made of a superconducting wire (Ni—Ti wire) is arranged so that the coil surface faces the z direction.

The coil portion 61 is composed of a combination of a detection coil 62 and a reference coil 63, which are coils in opposite directions. The detection coil 62 located on the side closer to the subject 2 detects the magnetic field signal from the subject 2. The reference coil 63 located on the side far from the subject 2 detects the external magnetic field noise.

The external magnetic field noise is generated from a signal source farther than the subject 2. Therefore, the noise signal is detected by both the detection coil 62 and the reference coil 63. On the other hand, the magnetic field signal from the subject 2 is weak.

Therefore, the magnetocardiographic signal is detected by the detection coil 62, but the reference coil 63 is almost insensitive to the magnetocardiographic signal. Therefore, the detection coil 62 detects the magnetic field signal and the external magnetic field noise signal, and the reference coil 63 detects the external magnetic field noise signal.

Thereby, the biomagnetic field having a high S / N (Signal / Noise) ratio can be measured by taking the difference between the signals detected by the detection coil 62 and the reference coil 63, respectively.

The detection coil 62 and the reference coil 63 are connected to an input coil (not shown) of the SQUAD 60 via a superconducting wire of a mounting board (not shown) on which the SQUID 60 is mounted. As a result, the component Bz in the normal direction of the detected magnetocardiographic signal is transmitted to the SQUID 60. By partially differentiating the normal component Bz in the x and y directions, the magnetic field components in the x and y directions can be approximated.

<Other configuration examples of magnetic sensor>
FIG. 6 is an explanatory diagram showing another example of the magnetic sensor 31 of FIG. FIG. 6 shows a configuration example of a sensor that detects tangential components Bx and By of the biomagnetic field. The magnetic sensor 31 of FIG. 6 is composed of SQUIDs 60a and 60b and coil portions 61a and 61b, similarly to the magnetic sensor of FIG. The coil portion 61a is composed of a detection coil 62a and a reference coil 63a, and the coil portion 61b is composed of a detection coil 62b and a reference coil 63b.

The detection coils 62a and 62b and the reference coils 63a and 63b are made of, for example, flat coils, and the detection coils 62a and 62b and the reference coils 63a and 63b are arranged side by side at intervals in the z direction.

The detection coil 62a and the reference coil 63a are connected to an input coil (not shown) of the SQUAD 60a via a superconducting wire of a mounting board (not shown) on which the SQUAD 60a is mounted. The detection coil 62b and the reference coil 63b are connected to an input coil (not shown) of the SQUAD 60b via a superconducting wire of a mounting board (not shown) on which the SQUAD 60b is mounted.

SQUID60a detects the Bx component. SQUID60b detects the By component. Thereby, the Bx component and the By component can be detected.

The tangential components Bx and By may be obtained by partially differentiating the normal components Bz obtained by the magnetic sensor 31 of FIG. 5 with respect to x and y, in addition to the magnetic sensor 31 of FIG. In this case, one magnetic sensor can detect and measure both the tangential components Bx and By and the normal component Bz.

Hereinafter, in the magnetocardimeter 10 shown in FIG. 1, the magnetic sensor 31 of the first-order differential type SQUID that measures the magnetic flux density in the normal direction shown in FIG. 5 is applied.

The magnetic sensor used in the magnetometer 10 is not limited to the SQUID 60 shown in FIGS. 5 and 6, and is not limited to the SQUAD 60 shown in FIGS. A magnetic resistance element such as Tunnel Magneto Resistance Effect) may be used.

The magnetic sensor 31 outputs a voltage having a specific relationship with the strength of the biomagnetic field (which can be considered as the magnetic flux density) generated from the subject 2 and detected by the detection coil 62, and the output is the FLL circuit 25. Is entered in.

The FLL circuit 25 cancels the change in the biomagnetic field (biomagnetism) input to the SQUID 60 via a feedback coil (not shown) so as to keep the output of the magnetic sensor 31 constant (this is called a magnetic field lock).

Then, the FLL circuit 25 obtains a voltage output having a specific relationship with the change of the magnetocardiographic signal by converting the current flowing through the feedback coil into a voltage. By detecting through the feedback coil in this way, a weak magnetic field can be detected with high sensitivity.

The voltage output from the FLL circuit 25 is input to the AFA circuit 26. The AFA circuit 26 samples the voltage output from the FLL circuit 25, performs A / D conversion, and then outputs the voltage to the computer 20.

The input gain and output gain of the AFA circuit 26 are adjustable. Further, the AFA circuit 26 includes a low-pass filter that passes a frequency signal below the first reference frequency, a high-pass filter that passes a frequency signal below the second reference frequency lower than the first reference frequency, and a commercial power frequency. Includes a notch filter to cut.

As the SQUID 60, for example, a DC SQUID is used. When an external magnetic field is applied to the SQUAD 60, a DC bias current (Ibias) is passed through the SQUID 60 so that a corresponding voltage (V) is generated.

When the external magnetic field is represented by the magnetic flux Φ, the characteristic curve of the voltage V with respect to the magnetic flux Φ, that is, the Φ−V characteristic curve is given by a periodic function. Prior to the measurement, an operation of adjusting the offset voltage (VOFF) of the FLL circuit 25 to set the DC voltage of the Φ−V characteristic curve to the zero level is performed.

FIG. 7 is an explanatory diagram showing an example of the positional relationship between the magnetic sensor array 30 of FIG. 4 and the subject 2. In FIG. 7, the body axis direction connecting the head and legs of the subject 2 is the y direction, and the lateral direction of the subject 2 is the x direction.

The points in the figure are the intersections of the rows and columns on the matrix of the magnetic sensor array 30, and indicate the measurement points of the subject 2, in other words, the measurement positions. Each of these measurement positions is called a channel. In this way, the entire heart of the subject 2 is measured simultaneously on 64 channels.

Subsequently, in order to make the features of the present embodiment easy to understand, comparative techniques for the present embodiment will be compared and described. First, a comparative technique for the present embodiment will be described.

FIG. 8 is a flowchart showing an example of a comparative technique in magnetocardiographic measurement by a magnetocardiogram with respect to the present embodiment. In the case of FIG. 8, the bed does not have hydraulic assist and has a structure for raising and lowering using, for example, a manual handle made of a non-magnetic material.

First, the operator enters the magnetic shield room with the subject (step S100). The operator pulls out the bed unit from under the dewar (step S110). Then, the operator puts the subject on the bed and takes a measurement posture (step S120). The operator assists the subject so that he / she is in a supine position for frontal measurement, prone for back measurement, and an appropriately measurable posture for measurement from other directions.

The operator then raises and lowers the bed before the subject moves under the dewar. The bed is raised by a manual handle and dehydrated when lowered. Subsequently, the operator specifies a reference position for alignment of the subject (step S130). In the case of frontal measurement, the xiphoid process is used as a reference. In the case of back measurement, it is difficult to determine the reference point on the skeleton, so for example, the position where the position of the xiphoid process is projected on the back is used as the reference point.

The operator then slides the bed in the x and y directions to move the subject under the dewar (step S140). When the position of the subject is determined by the xy plane, the operator raises the bed. At that time, it is necessary to bring the subject's chest close to the bottom of the dewar without touching it.

When the setting of the subject is completed, the operator once exits the magnetic shield room and performs the following measurement operation using a computer (step S150). First, the magnetic field of the magnetic sensor is locked by pressing the measurement preparation button using a keyboard or the like (step S160). This is an operation of fixing the operating point by feeding back the magnetocardiographic signal converted into a voltage by SQUID to SQUID.

When the operator presses the measurement preparation button and the baseline of the magnetocardiographic signal is set, the operator confirms the waveform of the magnetic sensor and confirms whether or not the signal strength is significantly biased depending on the position (step S170).

Since the waveform of this confirmation operation differs for each subject depending on the position of the subject's heart and the inclination of the axis, there is a risk that an operator with low proficiency may misunderstand the appropriate position.

When the deviation of the magnetic field strength is confirmed in the process of step S170, the operator determines that the position of the subject needs to be readjusted (step S180), and presses the measurement release button using a keyboard or the like. The magnetic field lock is released (step S220).

Subsequently, the operator enters the magnetic shield room (step S230) and performs the process of step S130, that is, the alignment operation of the subject. However, in this case, the operator adjusts the bed position so that the part to be measured is near the center of the measurement range, instead of aligning the xiphoid process, which is the reference point, with the predetermined magnetic sensor position.

If it is determined in the process of step S180 that the position of the subject does not need to be adjusted, the operator executes magnetocardiographic data collection by the magnetocardiogram (step S190). After the collection of the magnetocardiographic data is completed, if there is measurement in another measurement direction (step S200), the process returns to step S100 and the same process is repeated. On the other hand, when the data measurement from all directions is completed, the measurement is completed.

The operator enters the magnetic shield room, lowers the bed, pulls out the bed in the −x direction (step S210), raises the subject from the bed, and leaves the magnetic shield room. This completes the magnetocardiographic measurement.

In the processing example of the magnetocardiographic meter shown in FIG. 8, it was necessary for the operator to enter and leave the magnetic shield room many times when performing the magnetocardiographic measurement by one person. On the other hand, in the magnetocardiogram 10 of FIG. 1, the operator can perform the setting, position adjustment, and measurement of the subject in the magnetic shield room 100.

FIG. 9 is a flowchart showing an example of magnetocardiographic measurement by the magnetocardiographic meter 10 of FIG. In the flowchart of FIG. 9, the process of step S300 is a process executed after performing the same process as steps S100 to S150 shown in FIG.

When the process of step S150 of FIG. 8 is completed, the operator presses the measurement preparation button included in the simple operation unit 48 provided in the magnetic shield room 100. When the measurement preparation button is pressed, the control module 40 of the computer 20 controls the FLL circuit 25 to lock the magnetic field of the magnetic sensor 31 (step S300).

When the magnetic field is locked in the process of step S300, the processes of steps S320 to S350 are repeated until the operator presses the measurement start button or the measurement release button.

Hereinafter, with respect to the processes of steps S320 to S350, the subject position evaluation / control module 42 mainly executes the processes. When the magnetic field is locked, data for one heartbeat is collected (step S320).

Here, FIG. 10 shows a heartbeat waveform seen in a human electrocardiogram or the like. The electrophysiological activity of one heartbeat is signaled from the sinus node in the right atrium and transmitted to the ventricles via the right and left bundle branches in the core membrane.

Atrial depolarization and repolarization that occur during this period appear as P waves, ventricular depolarization appears as QRS waves (combined Q waves, RR waves, and S waves), and repolarization appears as T waves. As can be seen from FIG. 10, in order to acquire the data of one heartbeat, it is sufficient to take a signal of several hundred milliseconds before and after the R wave having a large signal value as a reference.

Subsequently, in FIG. 9, in order to determine whether or not the position of the subject is appropriate, the position of the excitement site in the R wave is specified (step S330). Here, the position that gives the maximum value of the magnetic field strength in the xy plane is set as the excitement site.

When the magnetic sensor 31 for measuring the magnetocardiographic signal of the z-axis component shown in FIG. 5 is used, the measured value is variable-differentiated at the x-coordinate and the y-coordinate (-dBz / dx, -dBz / dy). The square root of the sum of powers is the magnetic field strength, and the position where the maximum value is given is the excitement site.

When the magnetic sensor 31 that simultaneously measures the x-axis and y-axis components shown in FIG. 6 is used, the position where the maximum value is given as the magnetic field strength is the square root of the sum of squares of the measured values (Bx, By). And.

In the diagnosis of heart disease, for example, P wave for diagnosing atrial abnormalities and conduction disorders, T wave for ischemic disease, and the time of focus differs depending on the disease. In order to specify the range of the signal of one heartbeat, it is preferable to refer to the time when the R wave becomes the maximum value.

Since the excitement part of P wave and T wave does not match the excitement part of R wave, if the magnetic field strength of R wave is the maximum at the time when R wave is maximum, it is of interest for diagnosis. The area is off center.

Therefore, in order to display the excited part at the time of interest in the center of the magnetocardiography, it is necessary to set the position of the maximum value of the R wave in advance in consideration of the distance and positional relationship between the R wave and the center of the region of interest. is there.

For example, as shown in FIG. 11, a setting screen 70 for setting alignment parameters is displayed on the display 22. By using this setting screen 70, it is possible to set the maximum excitement portion of the R wave to appear at any of the 8 × 8 = 64 channel grid points of the magnetic sensor 31.

For example, in order to display the excited part of the T wave in the center of the magnetocardiogram, the position of the subject may be adjusted so that the excited part of the R wave appears at the grid points (X = 3, Y = 6). Of course, the alignment parameter does not necessarily have to be specified as the grid point of the magnetic sensor 31, and the excitement portion of the R wave can be designated in millimeters in the x and y directions from the center of the sensor grid point.

Subsequently, in FIG. 9, when the position coordinate at which the magnetic field strength of the R wave is maximized is specified in the process of step S330, the coordinate value of the R wave set so that the position coordinate and the portion of interest are centered. The difference between the above is calculated (step S340). Since it is determined how much the bed on which the subject is placed is moved in the vertical direction and the horizontal direction based on this difference value, the difference value is calculated separately for the x component and the y component.

Subsequently, the subject position evaluation / control module 42 displays on the display 22 the amount of deviation of the R wave excitement portion from the difference value obtained in the process of step S340 (step S350). The operator can easily readjust the subject's position and perform the adjustment operation based on the grid map for confirming the movement of the subject's heart before measurement and the amount of deviation of the R wave excitement site by the processing of step S350. It can be carried out.

Further, the alignment of the subject can be further facilitated by aligning the target coordinates of the R wave excitement portion with the actual coordinates with the isobaric diagram, or by illustrating the coordinates.

Further, in order to see the waveform distribution of the entire 64 channels, the grid map time waveform may be displayed on the display 22 as shown in FIG. By repeating this data measurement and the display of the grid map time waveform, it is easy for the subject to check whether the condition has not changed before the measurement or whether the positional relationship between the heart and the magnetic sensor 31 is appropriate. You can check.

In magnetocardiographic measurement, we want to set the R-wave excitement site near the center of the measurement site of the 64-channel magnetic sensor 31. The location to be set can be specified by the position of the magnetic sensor array or the coordinate system on the xy plane.

When the distance between this designated position and the active site calculated in the process of step S330 is larger than the predetermined distance, the subject position evaluation / control module 42 displays, for example, an isomagnetic field diagram on the display 22 and the operator. Notify to.

FIG. 13 is an explanatory diagram showing a display example of the isomagnetic field diagram in the magnetocardiogram 10 of FIG. In FIG. 13, the isomagnetic field diagram displayed on the display 22 shows the difference between the designated position and the active site at the upper part of the isomagnetic field diagram.

In the example of FIG. 13, a right arrow and a numerical value are shown on the upper left side of the isomagnetic field diagram, and an up arrow and a numerical value are shown on the left side thereof. The display in this case indicates that the designated position is located at a position where the active site or the bed 35 on which the subject is placed is moved 3.2 cm to the right and 3.5 cm in the counteraxial direction. By illustrating the active site and the designated position on the isomagnetic field diagram in this way, the positional relationship can be accurately grasped.

Here, the isomagnetic diagram will be described. Physical quantities obtained by arithmetic processing of signals at the magnetic sensor position, which is the measurement position of the magnetic field from the living body, include the magnetic flux density at a certain time, the time integral value obtained by integrating the magnetic flux density within the time interval with time, and the propagation time. The propagation time is the time from the reference time to the peak position of the QRS complex in the case of cardiac magnetic measurement.

A map created by connecting points with equal magnetic flux densities is called a magnetocardiographic diagram.

Since each channel is roughly set, by setting the spacing between the isobaric lines, that is, the difference in magnetic field strength in advance, and linearly interpolating between the channels to draw the isometric lines, a more suitable isometric line diagram for diagnosis can be obtained. Can be made.

The magnetocardiographic waveform data may be integrated over a predetermined time range. A map created by connecting points (channels) with the same time integration value is called a time integration diagram. In the time characteristics of the signal data detected by each magnetic sensor, the time from the time point t1 to the peak position point of the QRS complex is called the propagation time, and the map created by connecting the points with the same propagation time is the propagation time. Called a figure. The t1 time point may be further determined by detecting the peak position time point of the QRS complex and using this time point as a reference.

The isomagnetic diagram, the time integration diagram, and the propagation time diagram are reconstructed corresponding to the plane on which the magnetic sensor is arranged, but the characteristic quantity by each arithmetic processing is taken in the direction perpendicular to the plane. It can also be reconstructed as a dimensional mapping.

The processes of steps S320 to S340 of FIG. 9 are repeated at intervals of, for example, about 1 second. Subsequently, in FIG. 9, the subject position evaluation / control module 42 determines whether or not the amount of deviation of the R wave excitement portion is within the reference value (step S370).

The reference value is stored in, for example, a memory (not shown) provided by the subject position evaluation / control module 42. Alternatively, the computer 20 may be stored in a memory such as a hard disk drive or SSD (Solid State Drive) (not shown).

If it is within the reference value, the subject position evaluation / control module 42 notifies the operator by displaying on the display 22 that the amount of deviation of the excitement portion of the R wave is within the reference value. When the operator is notified that the deviation amount of the R wave excitement portion is within the reference value, that is, the position of the subject is appropriate, the measurement start button of the simple operation unit 48 is pressed (step S400). As a result, the data collection module 41 starts collecting data (step S410) and writes out the measurement data file (step S420).

Further, when it is determined that the deviation amount of the active site is outside the reference value (step S370), the subject position evaluation / control module 42 indicates to the display 22 that the deviation amount of the R wave excitement site is outside the reference value. Notify the operator by displaying or the like. The operator presses the measurement release button of the simple operation unit 48 to unlock the magnetic field (step S380), fine-tunes the position of the bed 35 (step S390), and then performs the process of step S300 again. ..

Here, the operator fine-tunes the position of the bed 35, but in the process of step S390, the subject position evaluation / control module 42 commands the bed position control unit 46 to position the bed 35. May be adjusted. In this case, the subject position evaluation / control module 42 generates a position adjustment signal indicating the amount of movement of the bed 35 from the difference value and outputs the position adjustment signal to the bed position control unit 46. The bed position control unit 46 moves the bed 35 based on the received position adjustment signal.

FIG. 14 is an explanatory diagram showing an example of information display by the magnetocardiogram of FIG. The display 22 cannot be installed in the magnetic shield room 100 because accurate magnetocardiographic measurement cannot be performed due to the influence of unnecessary radiation emitted. Therefore, as shown in FIG. 14, a projector 15 installed outside the magnetic shield room 100 is used to display a notification of whether or not the amount of deviation of the R wave excitement portion in the process of step S350 is within the reference value. To do.

The image of the projector 15 is projected onto the inner wall of the magnetic shield room 100 through the hole 100a provided in the magnetic shield room 100. Since the operator can confirm the amount of deviation of the excited portion of the R wave in the magnetic shield room 100, the magnetocardiographic measurement can be started, or the position of the subject can be finely adjusted. Thereby, the operator can easily determine whether or not the position of the subject is appropriate in the magnetic shield room 100.

As described above, the position of the subject can be adjusted so as to be the optimum measurement position regardless of the skill of the operator. This makes it possible to perform magnetocardiographic measurement with high reproducibility.

Further, since the operator can readjust the position of the subject without going in and out of the magnetic shield room, the time for magnetocardiographic measurement can be shortened.

Although the invention made by the present inventor has been specifically described above based on the embodiment, the present invention is not limited to the embodiment and can be variously modified without departing from the gist thereof. Needless to say.

The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations.

It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. .. Further, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

10 Magnetometer 11 Measurement control unit 12 Automatic replenishment device 13 Dewar 14 Bed unit 15 Projector 20 Computer 21 Keyboard 22 Display 23 Printer 24 Mouse 25 FLL circuit 26 AFA circuit 27 Measurement control circuit 30 Magnetic sensor array 31 Magnetic sensor 35 Bed 36 Bed control Unit 40 Control module 41 Data collection module 42 Subject position evaluation / control module 45 Bed position measurement unit 46 Bed position control unit 47 Pump unit 48 Simple operation unit 50 Manual lever 51 Cylinder 61 Coil unit 61a Coil unit 61b Coil unit 62 Detection Coil 62a Detection coil 62b Detection coil 63 Reference coil 63a Reference coil 63b Reference coil 100 Magnetic shield room

Claims (7)

A bed installed in a magnetic shield room that blocks the magnetic field from the outside,
A detector that is installed in the magnetic shield room and detects magnetocardiography, which is a magnetic field generated by the electrical activity of the myocardium of the subject lying on the bed.
A computer installed outside the magnetic shield room and controlling the detection unit,
With
The computer has a control unit that calculates the amount of deviation of the bed from the difference between the position of the excitement portion specified from the magnetocardiographic signal for one heartbeat detected by the detection unit and the position of the interest portion for magnetocardiographic measurement. Magnetocardiography. In the magnetocardiogram according to claim 1,
A position adjustment control unit installed in the magnetic shield room and adjusting the position of the bed so that the portion of interest is within the measurement range based on the position adjustment signal generated by the control unit is provided.
The control unit is a magnetocardiograph that generates the position adjustment signal from the calculated amount of deviation. In the magnetocardiogram according to claim 2.
The position adjustment control unit
A hydraulic pump unit that moves the bed and
Based on the position adjustment signal calculated by the control unit, the bed position control unit that drives the hydraulic pump unit and
Has a magnetocardiograph. In the magnetocardiogram according to claim 2.
The control unit determines whether or not the calculated deviation amount is within the preset reference value, and outputs an alert when it is determined that the difference is not within the reference value. Magnetocardiography. In the magnetocardiogram according to claim 2.
A projector installed outside the magnetic shield room and projecting an image on the inner wall of the magnetic shield room is provided.
The control unit is a magnetocardiograph that displays the calculated amount of deviation on the projector. In the magnetocardiogram according to claim 5.
It is installed in the magnetic shield room, and includes an operation unit that generates an operation signal instructing measurement preparation or measurement preparation cancellation of the detection unit and outputs the operation signal to the control unit.
The control unit is a magnetocardiograph that puts the detection unit in a measurement ready state or a measurement ready release state based on the operation signal output from the operation unit. In the magnetocardiogram according to claim 1,
The detection unit is a magnetocardiograph including a superconducting quantum interference element.