JP7683150B2 - DIAGNOSIS SUPPORT DEVICE, DIAGNOSIS SUPPORT METHOD, AND DIAGNOSIS SUPPORT PROGRAM - Google Patents

Description

The present invention relates to a diagnostic support device, a diagnostic support method, and a diagnostic support program.

For example, one known method for measuring biomagnetic fields is to apply electrical stimulation to a part of the subject, inducing neural activity in the area to be measured, and then measure the magnetic field generated by the neural activity with a sensor. Another known method is to non-invasively evaluate neural activity currents by reconstructing the currents generated within the body using magnetic field data obtained by measuring the biomagnetic field with a sensor.

For example, the conduction velocity of the neural activity current in the cauda equina can be calculated non-invasively by measuring the neural magnetic field at the lumbar region when the peroneal nerve at the knee is stimulated, and reconstructing the neural activity current from the obtained magnetic field data. In addition, by using the above method to statistically analyze the conduction velocity of the neural activity current for multiple healthy subjects, it is possible to obtain a correlation between age and conduction velocity (see, for example, Non-Patent Document 1).

However, no method has been disclosed for generating information that can assist in the diagnosis of diseases such as those of the lumbar spine from neural activity currents calculated using magnetic field data obtained by measuring the magnetic field generated by the subject.

The disclosed technology has been developed in consideration of the above-mentioned problems, and aims to provide a diagnostic support device, a diagnostic support method, and a diagnostic support program that can assist in the diagnosis of neurological disorders.

In order to solve the above technical problems, one embodiment of the diagnostic support device of the present invention is characterized in having a calculation unit that calculates a rate of decrease in current intensity of an inward current flowing into a nerve course based on magnetic field data obtained by measuring a magnetic field generated from a subject, a display control unit that causes a display unit to display a comparison result obtained by comparing the rate of decrease in current intensity with a predetermined reference value, and a reference changing unit that is capable of changing the reference value based on information indicating the measurement site for calculating the current intensity .

It is possible to provide a diagnostic support device, a diagnostic support method, and a diagnostic support program that can assist in the diagnosis of neurological diseases.

1 is a configuration diagram showing an example of a biological information measuring system including a diagnosis support apparatus according to a first embodiment of the present invention. 2 is a perspective view of an example SQUID sensor array disposed within a protruding portion of the cryocontainer of FIG. 1; FIG. FIG. 2 is a diagram illustrating an example of functional blocks of the data processing device of FIG. 1 . FIG. 1 is a diagram illustrating an example of a model of a neural action current. 2 is a diagram showing an example of a change over time in current distribution extracted based on magnetic field data at a measurement target site (central nerves) acquired by the bioinformation measurement system of FIG. 1. 2 is a diagram showing an example of a change over time in current distribution extracted based on magnetic field data at a measurement target site (central nerves) acquired by the bioinformation measurement system of FIG. 1. FIG. 7 is a diagram showing an example of changes in the current waveform when the inward current observed in FIGS. 5 and 6 is conducted from upstream to downstream. 7 is a diagram showing another example of display of abnormality information indicating a decrease rate of current intensity displayed in the decrease rate abnormality display unit of FIG. 3 . FIG. 2 is a diagram showing an example of time change in current distribution extracted based on magnetic field data at a measurement target site (peripheral nerve) acquired by the bioinformation measurement system of FIG. 1. FIG. 10 is a diagram showing an example of a change in the current waveform when the inward current observed in FIG. 9 is conducted from upstream to downstream. FIG. 4 is a block diagram showing an example of a hardware configuration of the data processing device shown in FIG. 3 .

The following describes the embodiments with reference to the drawings. Note that in each drawing, the same components are given the same reference numerals, and duplicate descriptions may be omitted.

First Embodiment
Fig. 1 is a configuration diagram showing an example of a bioinformation measuring system including a diagnosis support device according to a first embodiment of the present invention. For example, the bioinformation measuring system 100 shown in Fig. 1 includes a spinal cord evoked magnetic field measuring system that measures a magnetic field generated from nerves such as the spinal cord based on electrical stimulation.

The bioinformation measurement system 100 has as its main components a magnetic field measurement device 10, a cryogenic container 20, a nerve stimulation device 30, an X-ray imaging device 40, and a data processing device 50. The data processing device 50 is an example of a diagnostic support device. The nerve stimulation device 30 is a device that electrically stimulates nerves from the body surface (skin) of the subject P. In FIG. 1, the X-ray imaging device 40 is placed above the subject P, but it may be placed on the side, or both the top and the side.

The magnetic field measuring device 10 has a SQUID sensor array 11 including multiple superconducting quantum interference devices (SQUIDs) and a signal processing device 12. The magnetic field measuring device 10 can measure the magnetic field induced in the measurement target nerve of the subject P by electrical stimulation by the nerve stimulation device 30.

In this embodiment, the magnetic field measuring device 10 is used as a magnetospinograph (MSG). The magnetic field measuring device 10 can also be used as a magnetoencephalograph (MEG) or a magnetocardiograph (MCG). Hereinafter, the superconducting quantum interference device is also referred to as a SQUID.

The data processing device 50 has a function to control the timing of electrical stimulation to the living body by the nerve stimulation device 30, and a function to execute information processing of biological information such as the biomagnetic field measured by the magnetic field measurement device 10. The data processing device 50 also has a function to control the capture of X-ray images of the subject P by the X-ray imaging device 40. The data processing device 50 has a function to accept input from input/output devices such as a mouse 50a and a keyboard 50b.

The data processing device 50 also has a function of superimposing the direction of the current generated in response to the magnetic field measured by the magnetic field measuring device 10 on the X-ray image and displaying it on the display device 50c. The data processing device 50 has a function of calculating the time change in the current value at each of multiple consecutive positions (virtual electrodes) indicated by the operator operating the mouse 50a for the image displayed on the display device 50c. For example, the operator indicates multiple positions along nerves such as the spinal cord that are recognized by the X-ray image displayed on the display device 50c.

The data processing device 50 also has a function of displaying the current waveform at each virtual electrode on the display device 50c. For example, when the rate of decrease in current intensity, which is the maximum amplitude of the current waveform at adjacent virtual electrodes, is smaller than a preset reference value for the rate of decrease, the data processing device 50 has a function of displaying text or a figure, etc., adjacent to the current waveform indicating that the rate of decrease has decreased.

A part of the bioinformation measurement system 100 is placed in a magnetically shielded room 200 that shields against magnetism. By using the magnetically shielded room 200, it is possible to measure a weak magnetic field (e.g., a spinal cord induced magnetic field) generated from the subject P. The magnetically shielded room 200 can be constructed, for example, by stacking a plate material made of a high magnetic permeability material such as permalloy and a plate material made of a conductor such as copper or aluminum.

The magnetically shielded room 200 has an internal space that is, for example, about 2.5 m deep, 3.0 m wide, and 2.5 m high, and is equipped with a door 210 that allows the transportation of equipment and people to enter and exit. The door 210, like the other parts of the magnetically shielded room 200, can be constructed by laminating plates made of a high-permeability material such as permalloy and plates made of a conductor such as copper or aluminum.

In this specification, a high magnetic permeability material refers to a material with a relative magnetic permeability of more than 1000. In addition to permalloy, other high magnetic permeability materials include iron, nickel, and cobalt as simple substances, their alloys (including amorphous alloys, powders, and nanoparticles), ferrite, etc.

The bio-information measuring system 100 and its surroundings will be described in more detail below. A bed 300 is installed in the magnetically shielded room 200. A cryocontainer 20 is also installed in the magnetically shielded room 200, and a signal line 71 used for measuring the magnetic field and controlling the measurement is connected to a SQUID sensor array 11 installed in the protrusion 21 of the cryocontainer 20. The signal line 71 has a twisted cable structure to reduce magnetic field noise, and is pulled out of the magnetically shielded room 200 through a hole penetrating the wall of the magnetically shielded room 200 and connected to a signal processing device 12.

For example, measurement of the spinal cord induced magnetic field using the bioinformation measurement system 100 is performed while the subject P is lying supine on the bed 300 and in a resting state. Performing the measurement in a resting state not only reduces the burden on the subject P, but also reduces positional deviation from the SQUID sensor array 11 caused by the subject P's movements, and also reduces magnetic field noise from muscles caused by muscle tension.

The cryocontainer 20, also called a Dewar, holds the liquid helium required to operate the SQUID sensor array 11, which detects the magnetic field generated by the subject P, at extremely low temperatures. The protrusion 21 of the cryocontainer 20 has a shape suitable for measuring the spinal cord induced magnetic field. For example, the spinal cord induced magnetic field is measured with the subject P in a supine position, with the lower back in contact with the protrusion 21 and the lower back facing the tip of the SQUID sensor array 11.

When measuring the spinal cord induced magnetic field, it is necessary to intentionally induce neural activity in the subject P by electrical stimulation. Therefore, electrical stimulation is applied using the nerve stimulation device 30. For example, in this embodiment, electrical stimulation is applied alternately to the left tibial nerve and the right tibial nerve on the inside of both ankles, and the current conducted from upstream to downstream in the spinal cord is calculated based on each electrical stimulation. Here, upstream refers to a position relatively close to the stimulation position where the electrical stimulation is applied, and downstream refers to a position relatively far from the stimulation position. For this reason, two electrode pairs connected to the nerve stimulation device 30 via two signal lines 72 with a twisted cable structure are attached to the skin on the inside of both ankles, respectively.

Then, electrical stimulation is applied alternately to the subject P from the electrode pairs, alternately exciting the tibial nerves in both legs of the subject P, and the nerve activity caused by the excitation is propagated to the central nervous system. Then, the SQUID sensor array 11 facing the lumbar region of the subject P detects the magnetic field generated from the spinal cord and spinal nerves in the lumbar region.

The two electrode pairs may be attached to positions on both feet where nerves other than the tibial nerve can be electrically stimulated. The measurement site for the biomagnetic field based on electrical stimulation from both feet may be the chest or neck. Furthermore, when measuring the biomagnetic field of the neck, the two electrode pairs may be attached to positions on both hands where nerves can be electrically stimulated.

By alternately applying electrical stimulation from two electrode pairs and alternately measuring the biomagnetic field, it is possible to detect the difference in the current waveforms that are conducted to the spinal cord via the left and right nerves. Then, based on the difference in the current waveforms, it is possible to provide information to a doctor or other evaluator to identify the site of the disorder.

For example, the data processing device 50 is a computer such as a PC (Personal Computer), and is connected to the signal processing device 12, the nerve stimulation device 30, and the X-ray imaging device 40 via signal lines. The data processing device 50 controls the operation of the magnetic field measurement device 10, the nerve stimulation device 30, and the X-ray imaging device 40.

Figure 2 is a perspective view showing an example of a SQUID sensor array 11 provided in the protruding portion 21 of the cryocontainer 20 in Figure 1. For example, the SQUID sensor array 11 has a rod shape extending in the vertical direction, and has multiple SQUID sensors 11a arranged in a staggered pattern when viewed from above. Each SQUID sensor 11a is arranged so that its upper end faces the measurement target part of the subject P lying on the bed 300. In this embodiment, the multiple SQUID sensors 11a are arranged in the protruding portion 21 so that their upper ends are slightly curved to match the curved shape of the subject P's lower back when measuring the magnetic field.

Each SQUID sensor 11a measures the magnetic field generated by the subject P based on instructions from the signal processing device 12, and outputs the measured magnetic field as a voltage signal (magnetic field signal indicating the magnetic field) to the signal processing device 12. For example, each SQUID sensor 11a is a three-axis sensor having an X-axis, a Y-axis, and a Z-axis, and can measure the magnetic field signal as a three-dimensional vector quantity. Each SQUID sensor 11a may be a two-axis sensor having an X-axis and a Y-axis that can measure the magnetic field signal as a two-dimensional vector quantity, or a one-axis sensor having only the Z-axis.

The signal processing device 12 shown in FIG. 1 estimates the neural activity current at a specified measurement point based on the relationship between the position of the nerve of the subject P on the X-ray image and the position of each SQUID sensor 11a, and magnetic field data obtained by measuring the magnetic field generated from the subject P using the multiple SQUID sensors 11a. For example, an estimation algorithm such as a spatial filter method is used to estimate the neural activity current. This makes it possible to obtain a current waveform that shows the time change of the neural activity current at any position opposite the SQUID sensor array 11. Note that an artifact reduction method such as the DSSP (Dual Signal Sub-space Projection) method may be applied to remove artifacts from the magnetic field data obtained by measuring the magnetic field.

FIG. 3 is a diagram showing an example of functional blocks of the data processing device 50 of FIG. 1. The data processing device 50 has an input control unit 510, a calculation unit 520, a display control unit 530, and a storage unit 540. For example, the input control unit 510, the calculation unit 520, and the display control unit 530 are realized by a data processing program executed by a processor such as a CPU (Central Processing Unit) mounted on the data processing device 50.

The calculation of the rate of decrease in the current strength of the inward current by the input control unit 510, the calculation unit 520, and the display control unit 530, which will be described later, and the display of the comparison result of the rate of decrease in the current strength with a predetermined reference value, are realized by executing a diagnostic assistance program among the data processing programs. Then, the diagnostic assistance method is implemented by a processor such as a CPU executing the diagnostic assistance program.

The input control unit 510, the calculation unit 520, and the display control unit 530 may be realized by hardware such as an FPGA, or may be realized by a combination of software and hardware. The calculation unit 520 is an example of a calculation unit that calculates the rate of decrease in the current intensity of the inward current flowing into the nerve course based on magnetic field data obtained by measuring the magnetic field generated by the subject P.

For example, the storage unit 540 is realized by at least one of a semiconductor storage device such as a dynamic random access memory (DRAM), a static random access memory (SRAM), a read only memory (ROM), and a flash memory. The storage unit 540 may also be realized by a semiconductor storage device and a hard disk drive (HDD) or a solid state drive (SSD).

The input control unit 510 has a position input unit 511 and a waveform region designation unit 512. The calculation unit 520 has a path generation unit 521, a virtual electrode generation unit 522, a reconstruction analysis unit 523, a current component extraction unit 524, a current intensity calculation unit 525, a decline rate determination unit 526, and a standard change unit 527. The display control unit 530 has an image display unit 531, a waveform display unit 532, and a decline rate abnormality display unit 533. The display control unit 530 may be disposed outside the data processing device 50. The memory unit 540 is assigned a memory area for storing biomagnetic field data 541, morphological image data 542, analysis setting value 543, and decline rate standard value 544.

The input control unit 510 accepts operations of the mouse 50a, keyboard 50b, etc., performed by the operator of the magnetic field measuring device 10. The position input unit 511 accepts the position of a control point for expressing a nerve pathway such as the spinal cord on a morphological image such as an X-ray image displayed on the display device 50c. The position information accepted by the position input unit 511 is stored in the memory unit 540 as an analysis setting value 543. The waveform region designation unit 512 accepts the time range for displaying the current waveform calculated by the virtual electrode on the display device 50c. The virtual electrodes set on a nerve pathway such as the spinal cord on the morphological image are an example of second virtual electrodes arranged at predetermined intervals along the nerve course.

The path generation unit 521 calculates the path of the active nerve based on the position information of multiple control points input from the position input unit 511. The set nerve path is called a nerve course (path). Here, the calculated path is represented by multiple coordinate information or an equation showing a curve, and is stored in the storage unit 540 as an analysis setting value 543.

The virtual electrode generating unit 522 generates, for example, multiple virtual electrodes A at equal intervals on the nerve trajectory calculated by the path generating unit 521. Furthermore, a virtual electrode B is generated on the virtual electrode A on the nerve trajectory at a point an arbitrary distance away in the normal direction of the nerve trajectory. The interval, normal direction distance, and number of virtual electrodes generated on the path are specified by the operator via an input device such as the mouse 50a or keyboard 50b, and are stored in the memory unit 540 by the input control unit 510 as analysis setting values 543.

The reconstruction analysis unit 523 uses the magnetic field data of the subject P obtained by measuring the biomagnetic field using the magnetic field measurement device 10 to reconstruct the current components for each voxel arranged in a matrix at a predetermined interval. A voxel is an example of a first virtual electrode that is placed in a predetermined area including the site where the magnetic field data is acquired.

The current component extraction unit 524 extracts the radio wave waveform of each virtual electrode using the current component at the voxel calculated by the reconstruction analysis unit 523 based on the positional relationship between each virtual electrode and the voxel. For example, the current component extraction unit 524 extracts the current component (the direction from upstream to downstream is positive and the direction from downstream to upstream is negative) at virtual electrode A along the nerve tract in the time range accepted by the waveform region designation unit 512 as an intra-axonal current conducting the nerve axon in the nerve tract.

In addition, the current component extraction unit 524 extracts, as an inward current, a current component in the normal direction to the nerve trajectory on the virtual electrode B, in the time range accepted by the waveform region designation unit 512, with the direction toward the nerve trajectory being positive. Then, a current waveform of the inward current is generated based on the time change of the extracted inward current. Of the volume currents flowing outside the nerve axon, the inward current, which is a current component that flows into the depolarized part, is important in evaluating nerve function. The current waveform is generated, for example, by the waveform display unit 532 arranging the values of the inward current in chronological order to generate image data. The current component extraction unit 524 and the waveform display unit 532 are an example of a waveform generation unit that generates a waveform of the inward current at the virtual electrode.

The current intensity calculation unit 525 calculates, as the current intensity, the maximum value of the amplitude of the current waveform of the inward current for each virtual electrode calculated by the current component extraction unit 524. For example, the current intensity calculation unit 525 calculates, as the current intensity, the amplitude of the positive value of the current waveform.

The reduction rate determination unit 526 calculates the reduction rate (%) of the current intensity of the inward current for each pair of adjacent virtual electrodes. For example, the reduction rate determination unit 526 calculates the reduction rate (%) of the current intensity using formula (1). In formula (1), the symbol "*" indicates a product.
Reduction rate (%) of current strength = ((downstream current strength CS2)/(upstream current strength CS1))*100 (1)

The reduction rate determination unit 526 compares the calculated reduction rate of the current strength with a predetermined reference value (%) that has been set in advance. For example, the reduction rate determination unit 526 determines whether the reduction rate of the calculated current strength is smaller than a predetermined reference value. If the reduction rate determination unit 526 determines that the reduction rate of the calculated current strength is smaller than the predetermined reduction rate reference value (%), it outputs the reduction rate of the calculated current strength as a comparison result to the reduction rate abnormality display unit 533 together with, for example, the position information of the downstream virtual electrode for which the current strength was calculated. Note that instead of outputting the comparison result, the reduction rate of the calculated current strength and the predetermined reference value (the predetermined reduction rate reference value (%)) may be output and displayed on the display device 50c.

The standard change unit 527 changes the reference value of the decrease rate based on information indicating the measurement site for calculating the current intensity of the inward current, which is input via an input device such as the mouse 50a or keyboard 50b. For example, the reference value of the decrease rate for each measurement site is stored in the storage unit 540 as the decrease rate reference value 544. By making the decrease rate reference value changeable, it is possible to set an appropriate reference value according to the measurement site, and to appropriately assist in the diagnosis of spinal cord diseases. The standard change unit 527 may store the decrease rate reference value input from the keyboard 50b or the like in the storage unit 540 as the decrease rate reference value 544.

As shown in Fig. 5 and Fig. 6, the image display unit 531 causes the display device 50c to display small white arrows representing the direction and strength of the current in each voxel reconstructed by the reconstruction analysis unit 523, superimposed on the morphological image (X-ray image). Also, as shown in Fig. 7, the image display unit 531 causes the display device 50c to display the nerve pathways calculated by the pathway generation unit 521 and the virtual electrodes generated by the virtual electrode generation unit 522, superimposed on the X-ray image.

The waveform display unit 532 displays the current waveform for each virtual electrode calculated by the current component extraction unit 524 on the display device 50c in association with the virtual electrode superimposed on the X-ray image.

When the drop rate abnormality display unit 533 receives the drop rate of the current strength and the position information of the virtual electrode from the drop rate determination unit 526, it displays abnormality information indicating that the drop rate of the current strength is abnormal on the display device 50c. For example, the abnormality information is displayed on or next to the current waveform of the virtual electrode indicated by the position information received from the drop rate determination unit 526 as a drop rate value, text such as "drop rate abnormal", or a blinking figure.

The biomagnetic field data 541 storage area stores magnetic field data obtained by measuring the magnetic field generated by the subject P using the magnetic field measurement device 10. The morphological image data 542 storage area stores X-ray image data of the part of the subject P that is the subject of magnetic field measurement, imaged using the X-ray imaging device 40.

In the memory area of the analysis setting values 543, various parameters required for measuring the biomagnetic field by the magnetic field measuring device 10 and various setting values such as filters (high-pass filter, low-pass filter) to be used for the magnetic field data obtained by measuring the biomagnetic field are stored in advance. In addition, in the memory area of the analysis setting values 543, position information indicating the position of the voxel that is the current calculation point on the image displayed on the display device 50c and the position of the virtual electrode from which the current waveform is obtained is stored in advance.

The reference value of the current intensity referenced by the reduction rate determination unit 526 is stored in advance in the memory area of the reduction rate reference value 544. For example, the reference value of the reduction rate at the lumbar vertebrae is 70%, although this is not particularly limited. When the distance between the virtual electrodes is n (mm), the value (percentage) of 0.97 to the power of n may be defined as the reference value of the reduction rate, and the reduction rate of the current intensity may be set according to the distance between the virtual electrodes. By setting the reference value of the reduction rate of the current intensity when the distance between the virtual electrodes is several mm, it becomes possible to compare with the reference value with a spatial resolution of several mm.

Figure 4 is a diagram showing an example of a model of nerve activity current. Figure 4 shows how current is generated by the activity of nerves that run linearly from top to bottom in the figure, with the bottom side of Figure 4 being the peripheral side and the top side of Figure 4 being the central side. For example, by providing an electrical stimulus to a peripheral nerve, the stimulus is conducted as a current through the nerve axon from the bottom to the top.

At this time, an intra-axonal current flows toward the top of Figure 4 (forward direction), an intra-axonal current flows toward the bottom of Figure 4 (reverse direction), and a volume current flows outside the nerve axon and is a current component that returns to the depolarization point. The intra-axonal current that flows toward the top of Figure 4 is called the leading component, and the intra-axonal current that flows toward the bottom of the figure is called the trailing component.

To evaluate nerve function in detail, it is preferable to extract the intra-axonal current flowing along the nerve axon, i.e., the current component in the direction along the nerve tract, and the inward current flowing into the depolarization point, i.e., the current component in the direction normal to the nerve tract, and visually display them on the display device 50c.

Figures 5 and 6 are diagrams showing examples of changes over time in current distribution extracted based on magnetic field data at the measurement target site (central nerves) acquired by the bioinformation measurement system 100 of Figure 1. The images shown in Figures 5 and 6 are images in which the image display unit 531 superimposes the current components for each voxel reconstructed by the reconstruction analysis unit 523 on an X-ray image, and are displayed simultaneously on the screen of the display device 50c. Note that either the image of Figure 5 or the image of Figure 6 may be displayed on the screen of the display device 50c, or an image at a specified time may be enlarged and displayed.

The image shown in FIG. 5 shows, for example, the change over time in the current distribution calculated from the magnetic field data obtained by measuring the biomagnetic field generated when electrical stimulation is applied to the tibial nerve on the inside of the right ankle of subject P who may have a herniated disc. The image shown in FIG. 6 shows the change over time in the current distribution calculated from the magnetic field data obtained when electrical stimulation is applied to the tibial nerve on the inside of the left ankle of the same subject P. The images shown in FIG. 5 and FIG. 6 have current components superimposed on X-ray images taken from above of subject P lying in a supine position on bed 300. Therefore, the left side of the image at each time corresponds to the right side of subject P, and the right side of each image corresponds to the left side of subject P.

Times such as "8.500 ms" shown at the top of each image in Figures 5 and 6 indicate the time that has elapsed since the application of electrical stimulation. The thick dotted line that spans the images arranged horizontally indicates the boundary (L4/5) between the fourth lumbar vertebra (L4) and the fifth lumbar vertebra (L5). Note that the arrows placed between the images at each time are added to make the passage of time easier to understand, and do not need to be displayed on the screen of the display device 50c.

In each image, multiple small white arrows indicate the direction of the current for each voxel extracted by reconstruction, and the length of the arrow indicates the current intensity. The end of the arrow opposite the arrowhead is the position of the voxel, which is the unit for extracting the current component. In addition, the contour curves are current intensity distribution lines generated by connecting positions with the same current intensity.

In the images at each time, the dotted arrows indicate intra-axonal currents, and the shaded arrows indicate inward currents. The dotted arrows and shaded arrows are added for explanatory purposes and are not included in the images displayed on the display device 50c.

To obtain the magnetic field data used to calculate the current components shown in Figures 5 and 6, first, subject P is placed in a supine position on bed 300 in Figure 1 so that the subject's lumbar region faces the SQUID sensor array 11. Next, a simple X-ray image of subject P's lumbar region is taken, and the positional relationship between each SQUID sensor 11a and subject P's lumbar vertebrae is obtained by data processing device 50.

Next, electrodes of the nerve stimulation device 30 are attached to the inner ankles of both feet, and electrical stimulation (5 Hz square wave pulses with a duration of 0.3 ms) is applied alternately to the left and right tibial nerves. The nerve-induced magnetic field in the lumbar region that is generated in response to the electrical stimulation is then measured by the magnetic field measurement device 10.

In Figure 5, which shows the change over time in the current distribution when the right tibial nerve is electrically stimulated, it is observed that the leading and trailing components of the intraaxonal current that entered through the L5 intervertebral foramen on the right side of subject P (left side in Figure 5) are conducted downstream, as indicated by the dotted arrow. In addition, it is observed that an inward current is generated toward the nerve axon, as indicated by the shaded arrow.

In Figure 6, which shows the time change in current distribution when the left tibial nerve is electrically stimulated, it is observed that the leading and trailing components of the intraaxonal current that entered through the L5 intervertebral foramen on the left side of subject P (right side in Figure 6) are conducted downstream, as indicated by the dotted arrow. In addition, it is observed that an inward current is generated toward the nerve axon, as indicated by the shaded arrow.

Figure 7 shows an example of the change in the current waveform when the inward current observed in Figures 5 and 6 is conducted from upstream to downstream. The current waveform shown in Figure 7 is calculated on the virtual electrode by the current component extraction unit 524. In the inward current waveform corresponding to Figure 5, a decrease in current intensity is observed at the L4/5 intervertebral disc position. The arrows shown in the inward current waveform corresponding to Figure 5 are added for ease of explanation, and indicate the amplitude (current intensity) of the positive value of the current waveform used to calculate the rate of decrease.

In the two X-ray images shown in FIG. 7, virtual electrodes are superimposed on the nerve trajectory, which is added for reference and placed at a position offset toward the center of the body. In the X-ray images, the arrows pointing from the virtual electrodes to the nerve trajectory indicate inward currents. In this way, the virtual electrodes for extracting inward currents are set at intervals at positions a predetermined distance away from the nerve trajectory. In addition, the virtual electrodes for extracting inward currents are set on the opposite side to the side to which electrical stimulation is applied. For example, in the X-ray image corresponding to FIG. 5, the tibial nerve of the right ankle (left side in FIG. 7) is electrically stimulated, so the virtual electrodes are set on the left side of the subject P with respect to the nerve trajectory (right side in FIG. 7).

The decrease rate determination unit 526 determines that the decrease rate of the current intensity at the position of the L4/5 intervertebral disc is lower than the reference value of the decrease rate, and outputs the decrease rate of the current intensity together with the position information of the virtual electrode corresponding to the position of the L4/5 intervertebral disc to the decrease rate abnormality display unit 533. Note that the decrease rate of the current intensity is calculated as the ratio of the current intensity at the virtual electrode of interest to the current intensity at the next upstream virtual electrode (in this example, the position of the L5/S1 intervertebral disc), as shown in formula (1).

The drop rate abnormality display unit 533 displays the information indicating the drop rate of the current intensity received from the drop rate determination unit 526 as abnormality information adjacent to the corresponding current waveform on the display device 50c. In the example shown in FIG. 7, the drop rate of 63% calculated by the drop rate determination unit 526 is displayed on the display device 50c as the text "Drop rate 63%".

The text indicating the rate of decline may be in a color that is more noticeable than the color of the waveform, or may be made to blink. The display of the rate of decline is not limited to text, but may be in the form of a graphic, pop-up, or the like. The position at which the rate of decline is displayed is not limited to a position adjacent to the waveform, so long as it can be associated with the corresponding waveform. For example, the rate of decline may be displayed next to the virtual electrode superimposed on the X-ray image. Furthermore, the rate of decline may be displayed at the top or bottom of the image, so long as it can be associated with the waveform. In this case, the color of the virtual electrode corresponding to the displayed rate of decline may be made different from the colors of the other virtual electrodes, and further, the graphic of the corresponding virtual electrode may be made to blink.

On the other hand, in the inward current waveform corresponding to FIG. 6, no decrease in current intensity is observed at the L4/5 intervertebral disc position. Therefore, the decrease rate determination unit 526 does not output the decrease rate of current intensity to the decrease rate abnormality display unit 533. Note that the waveform shown at No. 7 is a current waveform that is not subject to diagnosis, so the decrease rate determination unit 526 does not determine a decrease in current intensity.

In the images corresponding to Figures 5 and 6, multiple drop rates corresponding to all virtual electrodes that generated the current waveforms may be displayed adjacent to the corresponding waveforms or the corresponding virtual electrodes. In this case, the color displayed on the screen may be changed, or the font size or type may be changed depending on whether the drop rate of the current intensity is smaller than a reference value. This allows the evaluator to recognize the progress of the drop rate of the current intensity.

The MR (Magnetic Resonance) image shown on the left side of FIG. 7 is for reference and does not need to be displayed on the display device 50c. The display control unit 530 causes the display device 50c to display an X-ray image with virtual electrodes corresponding to FIG. 5 and FIG. 6 superimposed thereon and an inward current waveform side by side. A doctor or other evaluator observing the image shown in FIG. 7 can recognize the decrease in current intensity at the L4/5 intervertebral disc position due to electrical stimulation of the right tibial nerve.

Then, the evaluator, for example, refers to the image shown in FIG. 7 and observes a separately taken MR image, etc., to diagnose the presence or absence of L4/5 disc herniation, etc. For example, an evaluator looking at the image shown in FIG. 7 can recognize the image shown in FIG. 5 as an image of the healthy side with no disorder, and the image shown in FIG. 6 as an image of the affected side with disorder. This allows the evaluator to diagnose, for example, the L4/5 disc that protrudes to the right dominantly in the MR image as a herniated disc. In other words, the image shown in FIG. 7 generated by the data processing device 50 can assist in the diagnosis of spinal cord diseases.

In addition, in the evaluation of peripheral nerves, the reference value of the current intensity referenced by the reduction rate determination unit 526 is stored in advance in the memory area of the reduction rate reference value 544. For example, the reference value of the reduction rate in the carpal tunnel is 70%, although this is not particularly limited. When the distance between the virtual electrodes is n (mm), the value (percentage) of 0.97 to the nth power may be defined as the reference value of the reduction rate, and the reduction rate of the current intensity may be set according to the distance between the virtual electrodes. By setting the reference value of the reduction rate of the current intensity when the distance between the virtual electrodes is several mm, it becomes possible to compare with the reference value with a spatial resolution of several mm.

Figure 8 is a diagram showing another example of display of abnormality information showing the rate of decrease in current intensity displayed by the decrease rate abnormality display unit 533 of Figure 3. For example, the decrease rate determination unit 526 of Figure 3 calculates the decrease rate (%) of the current intensity of the inward current for each pair of adjacent virtual electrodes. The decrease rate abnormality display unit 533 displays the current intensity value of each virtual electrode shown as 0 to 8 calculated by the current intensity calculation unit 525 of Figure 3 on the display device 50c. In addition, the decrease rate abnormality display unit 533 displays the rate of change (decrease rate) of the current intensity determined by the decrease rate determination unit 526 on the display device 50c in association with the value of the current intensity of each virtual electrode. Note that if the rate of change in the current intensity is less than 100, it indicates that the current intensity is decreasing.

At this time, the drop rate abnormality display unit 533 displays on the display device 50c drop rates lower than the reference value pre-stored in the memory area of the drop rate reference value 544 so that they can be distinguished from drop rates equal to or higher than the reference value. For example, the drop rates are distinguished by highlighting them using different colors or different font types. This allows the evaluator to recognize the progress of the drop rate of the current intensity while checking the actual current intensity at each virtual electrode and the rate of change of the current intensity between each virtual electrode pair.

The drop rate abnormality display unit 533 may display the reference value on the display device 50c together with the current intensity and the rate of change, as shown in FIG. 8. The reference value may be displayed on the display device 50c so that it can be changed on the display screen by a user interface. In this case, when the reference value is changed, the drop rate abnormality display unit 533 highlights the drop rate lower than the changed reference value on the display device 50c in real time.

Figure 9 shows an example of the change over time in current distribution extracted based on magnetic field data at the measurement target site (peripheral nerve) acquired by the bioinformation measurement system 100 of Figure 1. Detailed explanations of elements similar to those of Figures 5 and 6 will be omitted. The image shown in Figure 8 shows, for example, the change over time in current distribution calculated from magnetic field data obtained by measuring the biomagnetic field generated when electrical stimulation is applied to the left middle finger of subject P who may have carpal tunnel syndrome.

Figure 10 is a diagram showing an example of the change in the current waveform when the inward current observed in Figure 9 is conducted from upstream to downstream. The current waveform shown in Figure 10 shows the current waveform at a virtual electrode arranged along the median nerve from the third metacarpal bone, and was extracted by the current component extraction unit 524 in Figure 3. In Figure 10, it is possible to recognize on the screen of the display device 50c that the amplitude attenuates to 36.9% between waveform 8 and waveform 7 (near the center of the third metacarpal bone), which indicate the inward current. In Figure 10, the virtual electrode superimposed on the X-ray image, the arrow indicating the inward current, and the line indicating the nerve course are added for ease of explanation, and are the same as the superimposed image in Figure 7.

Figure 11 is a block diagram showing an example of the hardware configuration of the data processing device 50 of Figure 3. The data processing device 50 has a CPU 51, a ROM 52, a RAM 53, and an external storage device 54. The data processing device 50 also has an input interface unit 55, an output interface unit 56, an input/output interface unit 57, and a communication interface unit 58. For example, the CPU 51, ROM 52, RAM 53, the external storage device 54, the input interface unit 55, the output interface unit 56, the input/output interface unit 57, and the communication interface unit 58 are interconnected via a bus BUS.

The CPU 51 executes various programs such as the OS (Operating System) and applications, and controls the overall operation of the data processing device 50. The CPU 51 also executes the diagnostic assistance program described above to implement the diagnostic assistance method. The ROM 52 holds various programs including the diagnostic assistance program executed by the CPU 51, various parameters, etc. The RAM 53 stores the various programs executed by the CPU 51, data used by the programs, etc. The external storage device 54 is a HDD, SSD, etc., and stores the various programs deployed in the RAM 53.

An input device 60 that accepts input from an operator or the like who operates the data processing device 50 is connected to the input interface unit 55. For example, the input device 60 is a mouse 50a, keyboard 50b, or tablet in FIG. 3. An output device 70 that outputs various images, text, figures, and the like generated by the data processing device 50 is connected to the output interface unit 56. For example, the output device 70 is a display device 50c (FIG. 3) or a printer that displays display screens, etc. generated by various programs executed by the CPU 51.

A recording medium 80 such as a USB (Universal Serial Bus) memory is connected to the input/output interface unit 57. For example, various programs such as a diagnostic assistance program may be stored in the recording medium 80. In this case, the various programs are transferred from the recording medium 80 to the RAM 53 via the input/output interface unit 57. The recording medium 80 may be a CD-ROM or a DVD (Digital Versatile Disc: registered trademark), and in this case, the input/output interface unit 57 has an interface corresponding to the recording medium 80 to be connected. The communication interface unit 58 connects the data processing device 50 to a network or the like.

As described above, in this embodiment, for example, by calculating the rate of decrease in the current strength of the inward current based on magnetic field data obtained by measuring the magnetic field generated from the lumbar region or the cervical region, it is possible to assist in the diagnosis of spinal cord diseases such as herniated discs.

By displaying the rate of decrease of current intensity smaller than the reference value on the display device 50c in association with the waveform of the inward current, the change in the current waveform and the value of the rate of decrease can be provided to the evaluator as diagnostic support material. For example, by displaying information indicating the rate of decrease in association with the current waveform on the display device 50c only when the rate of decrease is smaller than the reference value, it is possible to make it easier to recognize abnormal areas compared to when information indicating all calculated rates of decrease is displayed.

In addition, the standard reduction rate can be changed appropriately according to the measurement site based on information indicating the measurement site where the current intensity of the inward current is calculated, thereby providing appropriate support for the diagnosis of spinal cord diseases.

The present invention has been described above based on each embodiment, but the present invention is not limited to the requirements shown in the above embodiments. These points can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form.

REFERENCE SIGNS LIST 10 magnetic field measuring device 11 SQUID sensor array 11a SQUID sensor 12 signal processing device 20 cryostat 21 protrusion 30 nerve stimulating device 40 X-ray imaging device 50 data processing device 50a mouse 50b keyboard 50c display device 54 external storage device 55 input interface unit 56 output interface unit 57 input/output interface unit 58 communication interface unit 60 input device 70 output device 71, 72 signal line 80 recording medium 100 bioinformation measuring system 200 magnetically shielded room 210 door 300 bed 510 input control unit 511 position input unit 512 waveform area designation unit 520 calculation unit 521 path generation unit 522 virtual electrode generation unit 523 reconstruction analysis unit 524 current component extraction unit 525 current intensity calculation unit 526 Decrease rate determination section 527 Criterion change section 530 Display control section 531 Image display section 532 Waveform display section 533 Decrease rate abnormality display section 540 Storage section 541 Biomagnetic field data 542 Morphological image data 543 Analysis setting value 544 Decrease rate reference value BUS Bus CS1, CS2 Current intensity P Subject

Shuta Ushio et al, "Visualization of the electrical activity of the cauda equina using a magnetospinography system in healthy subjects", Clinical Neurophysiology, Volume 130, Issue 1, January 2019, Pages 1-11

Claims (12)

A calculation unit that calculates a rate of decrease in the current intensity of an inward current flowing into a nerve tract based on magnetic field data obtained by measuring a magnetic field generated from a subject ;
a display control unit that displays a comparison result obtained by comparing the reduction rate of the current intensity with a predetermined reference value on a display unit;
a reference changing unit capable of changing the reference value based on information indicating a measurement site for calculating the current intensity . A calculation unit that calculates a rate of decrease in the current intensity of an inward current flowing into a nerve tract based on magnetic field data obtained by measuring a magnetic field generated from a subject ;
a display control unit that displays a comparison result obtained by comparing the reduction rate of the current intensity with a predetermined reference value on a display unit;
a reduction rate determination unit that determines whether or not the reduction rate of the current intensity calculated by the calculation unit is smaller than the reference value,
The display control unit causes information indicating the decrease rate of the current intensity determined by the decrease rate determination unit to be smaller than the reference value to be displayed on the display unit as the comparison result.
A diagnostic support device comprising: 3. The diagnosis support device according to claim 1 , wherein the display control unit causes a display unit to display information for evaluating a rate of decrease in the current intensity. a reconstruction analysis unit that reconstructs current components at a plurality of first virtual electrodes that are placed in a predetermined region including a site from which the magnetic field data is acquired, based on the magnetic field data;
a current component extraction unit that extracts current components at a plurality of second virtual electrodes that are arranged at predetermined intervals along a nerve trajectory on the anatomical image of the subject based on the current components reconstructed by the reconstruction analysis unit;
a waveform generating unit that generates a waveform of the inward current at the second virtual electrodes based on the current components extracted by the current component extracting unit;
having
The display control unit causes the display unit to display the comparison result in association with the current waveform generated by the waveform generating unit.
The diagnosis support device according to claim 2 . The display control unit outputs, to the display unit, information indicating a decrease rate of the current intensity determined by the decrease rate determination unit to be smaller than the reference value, together with a corresponding current waveform.
The diagnosis support device according to claim 4 . 6. The diagnostic support device according to claim 1 , wherein the rate of decrease in the current intensity is represented by a ratio CS2/CS1 of a current intensity CS2 downstream of the neural activity to a current intensity CS1 upstream of the neural activity. 7. The diagnostic support device according to claim 1, wherein the calculation unit calculates a rate of decrease in the current intensity based on magnetic field data obtained by measuring a magnetic field generated from a lumbar region or a cervical region of the subject. 7. The diagnostic support device according to claim 1 , wherein the calculation unit calculates a rate of decrease in the current intensity based on magnetic field data obtained by measuring a magnetic field generated in a peripheral nerve of the subject. Calculating a rate of decrease in the current intensity of the inward current flowing into the nerve tract based on magnetic field data obtained by measuring the magnetic field generated from the subject ;
A comparison result of the reduction rate of the current intensity with a predetermined reference value is displayed on a display unit,
A diagnostic support method, comprising : changing the reference value based on information indicating a measurement site for calculating the current intensity . Calculating a rate of decrease in the current intensity of the inward current flowing into the nerve tract based on magnetic field data obtained by measuring the magnetic field generated from the subject ;
A comparison result of the reduction rate of the current intensity with a predetermined reference value is displayed on a display unit,
determining whether the calculated reduction rate of the current intensity is smaller than the reference value;
A diagnostic support method, comprising : displaying, as the comparison result, information indicating a rate of decrease in the current intensity determined to be smaller than the reference value on a display unit . A process of calculating a rate of decrease in the current intensity of an inward current flowing into a nerve tract based on magnetic field data obtained by measuring a magnetic field generated from the subject;
A process of comparing the reduction rate of the current intensity with a predetermined reference value and displaying a comparison result on a display unit;
and changing the reference value based on information indicating a measurement site for calculating the current intensity . A process of calculating a rate of decrease in the current intensity of an inward current flowing into a nerve tract based on magnetic field data obtained by measuring a magnetic field generated from the subject;
A process of comparing the reduction rate of the current intensity with a predetermined reference value and displaying a comparison result on a display unit;
A process of determining whether the calculated reduction rate of the current intensity is smaller than the reference value;
and displaying, on a display unit, information indicating a rate of decrease in the current intensity that is determined to be smaller than the reference value as the comparison result .

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