JP3407509B2 - Biological activity current source display - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a biological activity current source display device for estimating and displaying a physical quantity (position, size, etc.) of a biological activity current source. 2. Description of the Related Art When a living body is stimulated, the polarization formed across the cell membrane is broken and a living activity current flows. This biological activity current appears in the brain and heart, and is stored as an electroencephalogram and an electrocardiogram. The magnetic field generated by the biological activity current is stored as a magnetoencephalogram and a magnetocardiogram. Recently, as a device for measuring a minute magnetic field in a living body, SQUID (Superconducting Quantum Inter
face Device: A sensor using a superconducting quantum interferometer) has been developed. This sensor is placed outside the head, and the sensor can non-invasively measure a small magnetic field generated by a current dipole (hereinafter simply referred to as a current source), which is a biological activity current source, generated in the brain. From the measured magnetic field data, the physical quantity (position, size, etc.)
Estimation using the minimum norm method or the like, as shown in FIG.
The estimated current source is converted into a vector (arrow) in proportion to the size (dipole moment) of the current source on each grid point (position of the current source), and a tomographic image obtained by an X-ray CT apparatus or an MRI apparatus It is displayed above and used for specifying a physical position of an affected part or the like. [0004] However, in the case of the conventional example having such a configuration, there are the following problems. According to the conventional device that performs the display as shown in FIG. 7, since each current source on the grid point is displayed by a vector, it is difficult to recognize the three-dimensional spread of the current source. Since the extent of the current source is related to the size of the site of interest (affected area) of the subject and is a clinically important factor, the three-dimensional spread of the current source should be easily recognized. Is desired. Also, as a result of measurement of a living activity current source,
There is a case where a discrete current source exists around an aggregate of current sources (a portion where the current sources are densely packed). In such a case, a portion where the current sources are dense is estimated to have a high probability that a true current source exists. However, if the moment of the current source discrete around the current source is relatively large, and the current source is indicated by a vector (arrow), this current source is emphasized on the display and the true current source is estimated. When recognizing, it may be confusing for a person who makes a diagnosis, for example, whether or not this discrete current source is also included as a part of an aggregate specifying a true current source. SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and solves the above-mentioned drawbacks, and requires a current necessary for specific recognition of a true current source position from an estimated physical quantity of the current source. It is an object of the present invention to provide a biological activity current source display device capable of clearly displaying the spread of a source. [0007] In order to achieve the above object, the present invention has the following configuration. That is, the present invention is an apparatus that displays or prints out a distribution state of a biological activity current source whose position and size are estimated at least (hereinafter, simply referred to as “current source”),
(A) For each of the estimated current sources, a predetermined number of current sources (neighboring current sources) are extracted in ascending order of distance from the current source (current source of interest), and the current source of interest and each of the extracted current sources are extracted. A three-dimensional conversion means for determining an average distance to a nearby current source and determining a solid according to the average distance; and (b) dividing the size of each current source (current source of interest) by the size of the corresponding solid. (C) image processing means for allocating display densities in ascending order from the smaller of the three-dimensional densities, and (d) the three-dimensional conversion means at the position of each current source. Image output means for displaying or printing out the determined solid at the density assigned by the image processing means. The operation of the present invention is as follows. First, for each of the biological activity current sources (current sources) whose positions and sizes are estimated at least, a predetermined number of current sources (neighboring current sources) are ordered by the three-dimensional conversion means in ascending order of distance from the current source (current source of interest). ) Is extracted, the average distance between the current source of interest and each of the extracted nearby current sources is determined, and a solid corresponding to the average distance is determined. Next, a value obtained by dividing the size of each of the current sources (current source of interest) by the size of the corresponding solid is calculated by the solid density calculating means (determining the solid density). Subsequently, the image processing means assigns display densities in ascending order from the smaller solid density. Then, the image output unit displays or prints out the three-dimensional object determined by the three-dimensional conversion unit at the position of each current source at the density assigned by the image processing unit. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an embodiment of the biological activity current source display device according to the present invention. In the figure, reference numeral 2 denotes a magnetically shielded room, and a bed 3 on which the subject M is supine, and a living activity current source which is disposed in the brain of the subject M and is placed in the magnetically shielded room 2. And a multi-channel SQUID sensor 1 for non-invasively measuring a minute magnetic field due to. This multi-channel SQUID sensor 1
A large number of magnetic sensors are immersed in a coolant in a dewar. [0010] The magnetic field data detected by the multi-channel SQUID sensor 1 is applied to a data conversion unit 4 and converted into digital data, and then collected in a data collection unit 5. The stimulating device 6 is for giving an electrical stimulus (or a sound, a light stimulus, or the like) to the subject M. The positioning unit 7 is a multi-channel S
This is a device for grasping the positional relationship of the subject M with respect to a three-dimensional coordinate system based on the QUID sensor 1. The current source estimating unit 8 includes a data collection unit 5
This is for estimating the physical quantity (position, size, etc.) of the current source in the region to be diagnosed of the subject M based on the magnetic field data collected in the step (a). The current source estimating section 8 is connected to a current source display section 9 which is a main part of the present invention. The current source display unit 9 converts the current sources estimated by the current source estimating unit 8 into a three-dimensional solid.
0, a three-dimensional density calculating unit 11 for obtaining a value (three-dimensional density) relating to the size of the current source and the three-dimensional size, and an image processing unit 12 for assigning a display density to each three-dimensional object based on the three-dimensional density. A color monitor 13 as image output means for displaying the three-dimensional image obtained by the three-dimensional image conversion unit 10 at the position of each current source at the density assigned by the image processing unit 12, and a color printer 14 for printing and outputting as necessary. , And a magneto-optical disk 15. The three-dimensional conversion unit 10, three-dimensional density calculation unit 11, and image processing unit 12 of the current source estimating unit 8 and the current source display unit 9 are configured by computer software. The magneto-optical disk 15 connected to the image processing unit 12 stores, for example, tomographic images obtained by an X-ray CT apparatus or an MRI apparatus, and the current source estimated by the current source estimating unit 8 is The image is superimposed on these tomographic images and displayed on the color monitor 13 or printed out on the color printer 14. As described above, the multi-channel SQUA
The positional relationship of the subject M with respect to the three-dimensional coordinate system based on the ID sensor 1 is measured and stored, and the multi-channel SQUID sensor 1 is used as a diagnosis target area of the subject M, for example, a minute current from a current source in the brain. After measuring the magnetic field and collecting the magnetic field data in the data collection unit 5, the current source estimating unit 8 executes a current source estimation process. In the present invention, the method of estimating the current source is not particularly limited. For example, the current source is estimated using the minimum norm method (for example, WHKullmann, KDJandt, K. Rehm, HASchlitt,
WJDallas and WESmith, Advances in Biomagnetis
m, pp. 571-574, Plenum Pless, New York, 1989). Hereinafter, a current source estimating method using the minimum norm method will be briefly described with reference to FIG. A large number of grid points (1) to (n) are set in, for example, the brain which is a diagnosis target area of the subject M, and an unknown current source (current dipole) is assumed at each grid point. It is represented by a dimension vector VPi (i = 1 to n). Then, each magnetic sensor S of the SQUID sensor 1
_The magnetic fields B _{1 to} B _m detected at _{1 to} S _m are represented by the following equation (1). ## EQU1 ## [0017] formula _{(1), VP i = (} P ix, P iy, P iz) α ij = (α ijx, α ijy, α ijz) represented by. Note that α _ij is the magnetic sensors S ₁ to S ₁ when a current source having a unit size in the X, Y, and Z directions is placed on a grid point.
Is a known coefficient which represents the strength of the magnetic field detected by each position of the S _m. [B] = (B ₁ , B ₂ ,..., B _m ) [P] = (P _1x , P _1y , P _1z , P _2x , P _2y , P _{2z ,.}
(P _nx , P _ny , P _nz ), the expression (1) can be rewritten into a linear relational expression like the expression (2). [B] = A [P] (2) In the equation (2), A is a matrix having 3n × m elements represented by the following equation (3). [Equation 2] Here, when the inverse matrix of A is represented by A ⁻ ,
[P] is represented by the following equation (4). (P) = A ^- (B) ......... (4) [0021] Current source (P) norms | [P] | By the addition of conditions that minimize, the above equation (4) is the following formula (Five)
It is represented as [P] = A ⁺ [B] (5) where A ⁺ is a generalized inverse matrix expressed by the following equation (6). ^{A + = A t (AA t} ) -1 ......... (6) However, A ^t is the transpose matrix of A. By solving the above equation (5), the current sources VPi on each grid point
Estimate the size of This is the principle of the current source estimation method using the minimum norm method. Each current source estimated in this way is
The process of displaying the three-dimensional density according to the distribution state on the current source display unit 9 will be described below with reference to the flowchart shown in FIG. Now, it is assumed that the current source estimating section 8 has estimated the current sources P _i (i = 1 to n) as shown in FIG. Here, the position, size, and direction are estimated as physical quantities of each current source. Further, the position of each current source is associated with a predetermined grid point. [0025] In step S1, Yuki by focusing the current source P ₁ to P _n sequentially, each current source that focuses (hereinafter, referred to as "focusing current source") for, in order distance is short from the focused current source A predetermined number of current sources (hereinafter, referred to as
“Nearby current source”). For example, the eight predetermined number of neighboring current source, to describe the neighborhood current sources corresponding to the target current source P _1, eight neighborhood current source in a position close to the focusing current source P ₁ P _2, P _{5 ,} P _3, P _4, P _6,
P _7, a P _8, P _9, think of this as one of the group.
If the current source of interest is P ₂₇ , the nearby current source is P _27
20, the _{P 19, P 21, P 6} , P 18, P 23, P 22, P 5.
This is similarly extracted up to all current sources Pn, and grouping is performed. In FIG. 4, for convenience of explanation, each current source is focused from the current source (P ₁ ) at the center toward the periphery, but the order of attention is arbitrary. Next, in step S2, the average distance di (i = 1) between the current source of interest and the nearby current source group in each group.
To n). This is performed based on grid point coordinates (coordinates of the center of gravity of the current source) that are set in advance. For example, in the case of a group of interest current source P _1, apart from the interest current source P ₁ and near current source group _{P 2, P 5, P 3} , P 4, P 6, P 7, P 8, P 9 , respectively The average value of the distance (the straight line distance between the grid point coordinates) is [d
₁ ]. In the case of a group of interest current source P _27, focusing current source P ₂₇ and near current source group P _20, P _19, P
_21, the average distance between _{P 6, P 18, P 23} , P 22, P 5 each is [d _27]. Then, average distances d _{1 to} dn to all the current sources Pn are obtained. In this example, (dense) close to the current source P ₁ and its vicinity current source group in a position,
The obtained average distance d ₁ is a small value. The current source P
₂₇ and a group of current sources in the vicinity thereof are located far (not dense), and the calculated average distance d ₂₇ is a large value. That is, the smaller the average distance di value is, the higher the distribution density of the nearby current sources around the current source of interest is, and conversely, the larger the average distance di value is, the higher the distribution density of the nearby current sources around the current current source of interest is Means low density. Then, in step S3, in order to indicate the extent of the spread of the neighboring current sources existing around the current sources on each grid point, as shown in FIG.
For example, a cube having a length of one side is created (however, it is shown two-dimensionally in FIG. 5). That is, each current source P
For i (P ₁ ~Pn), the size of the cube in accordance with the distribution of each of the neighboring current source is obtained. In the above example, the current source P ₁ is a small cube, and the current source P _1
27 becomes a larger cube. Step S3 above
The processing up to is performed by the three-dimensional conversion unit 10 of the current source display unit 9. Hereinafter, the processing in the three-dimensional density calculation unit 11 will be described. The solid density calculator 11 calculates, for each cube, a value (solid density) related to the size (dipole moment) of each current source of interest and the distribution (size of the cube) of nearby current sources. As a procedure, in step S4, the moment (the magnitude of the physical quantity) of each current source at the lattice point is set to Mi (i = 1 to n), and this moment Mi
Is the volume d of each cube with the above-mentioned average distance di value as one side.
A value obtained by dividing by i ³ is obtained, and this value is used as the solid density Ci (i =
1 to n). For example, the focusing current source P _1, the moment M ₁ of the current source P _1, 3 cube of the average distance d ₁ values between neighboring current source group obtained in step S2 (the size of the cube of the current source P ₁₎ Is the solid density C ₁ of the current source P ₁ . In the current source P ₂₇ , the solid density C ₂₇ is obtained in the same manner. This is calculated for all the current source P ₁ to PN. As the solid density Ci is larger, the moment of the current source at that position is larger and the nearby current sources are denser. Conversely, when the solid density Ci is smaller, the moment of the current source is smaller or the nearby current source is smaller. It will not be dense. In other words, it can be said that the higher the solid density of the cube corresponding to each current source of interest, the higher the probability that a true current source exists in the cube. Therefore,
Even in the case of a current source having a relatively large moment (for example, the current source P ₂₇ ), if the group of nearby current sources is discrete, the average of the current source of interest and the nearby current source obtained above is obtained. Since the distance (d ₂₇ ) increases and the solid density (C ₂₇ ) of the current source decreases, the current source (P
₂₇ ) is highly likely not a true current source. Next, in step S5, the image processing unit 12 is a three-dimensional density Ci of the current sources P ₁ to PN, Yuku allocates the concentration for display in accordance with the value. Specifically, when an image output unit such as the color monitor 13 or the color printer 14 displays or prints out each cube at the position of each current source, a cube having a large solid density is conspicuous.
In other words, shades are assigned to each cube so that a cube having a high possibility of a true current source is prominent. For example, when the background (background) of the output image is light (eg, white), a dark color (eg, black) is conspicuous. Therefore, as the value of the three-dimensional density increases, the image is represented by a darker color. Hereinafter, an example of the procedure will be described. First, the three-dimensional density C calculated in step S4
Sort i in ascending order according to its size. Then, the coefficient i of the rearranged solid density Ci is, for example, a coefficient k (1 to
Ck instead of n). Next, the solid density Ck
Is assigned a constant color based on. This is because, for example, a color monitor has 0-255 gradations (gradations), and a value (256 / Cmax) obtained by dividing the number of gradations “256” by the maximum value Cmax of the solid density Ck is defined as a constant. By multiplying a constant by each solid density Ck, a display density corresponding to the size of the solid density Ck is allocated to each cube. As a result, a cube having a higher solid density value is assigned a higher density (a color that is more noticeable on the display screen), and a cube having a smaller solid density value is assigned a lower density (a color that is less noticeable on the lower surface of the display). Next, in step S6, the cube obtained by the three-dimensional conversion unit 10 is placed at the position Pi of each current source at the density assigned by the image processing unit 12 to the color monitor 13 at the density.
Displayed above or printed out by the color printer 14. At this time, the distribution of each current source is three-dimensional (three-dimensional), but the output image is two-dimensional, so that a cube having a high possibility that a true current source exists can be confirmed on the two-dimensional output image. As described above, the cubes of the respective current sources are superimposed and displayed with the assigned density in order from the solid with the lowest density (inconspicuous color), that is, in ascending order of the solid density Ck. FIG. 6 shows an example of an output image showing the distribution state of each current source obtained as a result of the above processing. In this figure, the area where the black points are dense is a cubic area having a large solid density Ck, and the area where the black points are discrete is a cubic area having a small solid density Ck. Reference numeral 20 in FIG. 6 indicates a cylindrical phantom used for test measurement of a living activity current source. As can be understood from the example of the output image shown in FIG. 6, the region where the true current source is likely to exist is highlighted in a widened form, and the discrete current sources are Even if the moment is large, it is displayed so as to be almost inconspicuous on the output image, so that the person making the diagnosis is not distracted by such a discrete current source, and the possibility that a true current source exists may be present. It is possible to correctly and quickly recognize the extent of the high area. The present invention can be modified as follows. Since the solid with density in the above-described embodiment is displayed so as to be superposed in order from a light color to a dark colored cube, the density changes rapidly at the boundary of each cube, but the density changes smoothly at this boundary. May be performed. In the above-described embodiment, an example has been described in which the apparatus for estimating a life activity current source and the current source display unit 9 which is a main part of the present invention are integrated. The data of the physical quantity of the current source obtained in the above may be temporarily stored in a floppy disk or the like, and the above-described processing may be performed by the current source display unit 9 which is separately configured.
Further, in the above-described embodiment, each current source is converted into a cube, but this may be converted into a sphere having a radius corresponding to the average distance between the current source of interest and a nearby current source. As is apparent from the above description, according to the present invention, for a group of current sources estimated on a large number of grid points, the spread of nearby current sources around each current source ( (Distribution state) is represented by a solid, and the density of the current sources existing in the solid is represented by the display density of the solid, so that the aggregate (spread) of true current sources can be easily three-dimensionally displayed. Can be recognized. Further, even if the current sources present discretely have a large moment, they are displayed with inconspicuous density, so that the current source at this position is not emphasized on the output image, and the When estimating and recognizing the current source, the diagnosing person is not confused.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a biological activity current source display device according to the present invention. FIG. 2 is an explanatory diagram of a current source estimation process according to the embodiment. FIG. 3 is a flowchart illustrating a process of a current source display unit according to the embodiment. FIG. 4 is a diagram schematically showing a current source at each grid point. FIG. 5 is a diagram showing a state in which a current source at each grid point is converted into a solid. FIG. 6 is a diagram illustrating an example of an output image obtained by the processing of the embodiment. FIG. 7 is a diagram showing a result obtained from a biological activity current source display device according to a conventional example. [Description of Signs] 9: current source display unit 10: three-dimensional conversion unit 11: three-dimensional density calculation unit 12: image processing unit 13: color monitor 14: color printer

Claims (1)

(57) [Claim 1] An apparatus for displaying or printing out the distribution state of a biological activity current source (hereinafter, simply referred to as “current source”) at least whose position and size have been estimated. , (A)
For each of the estimated current sources, a predetermined number of current sources (neighboring current sources) are extracted in ascending order of the distance from the current source (current source of interest), and the current source of interest and each of the extracted nearby current sources are extracted. And (b) a value obtained by dividing the size of each current source (current source of interest) by the size of the corresponding solid (solid). Density) calculating means for calculating the density);
(C) image processing means for assigning display densities in ascending order from the smaller solid density, and (d) assigning a solid determined by the solid conversion means to the position of each current source by the image processing means. A biological activity current source display device, comprising: image output means for displaying or printing out at a different density.