JP3567564B2 - Current source simulator - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a current source simulator used for collecting test data for estimating a current source in a biomagnetism measuring device that measures a minute magnetic field generated with a biological activity current source in a subject.
[0002]
[Prior art]
When a stimulus is applied to a living body, the polarization formed across the cell membrane is temporarily broken, causing an active current to flow.Such an active current is particularly found in the brain, heart, skeletal muscle, retina, and the like. The magnetic field generated by such an in-vivo active current is recorded as a magnetoencephalogram, a magnetocardiogram, a myocardium, and a retinal magnetogram, respectively, and is widely used for diagnosis of a lesion or the like.
[0003]
As a device for measuring a magnetic field generated by such an active current, a biomagnetic measurement device using a high-sensitivity magnetometer called SQUID (Superconducting Quantum Interference Device) has been developed for medical diagnostic devices with the development of superconducting device technology in recent years. It is being put to practical use as one, and is expected to be useful for elucidation of brain function and diagnosis of cardiovascular disease.
[0004]
In this biomagnetism measuring device, based on the measured biomagnetic field data, for example, the least square method or the least norm method is used to estimate the position, direction, size, etc. of the bioactive current source in a coordinate system based on the magnetometer. (Jukka Sarvas, "Basic mathematical and electromagnetic concepts of the biomagnetic inverse probe,", Phys. Med. Biol., No. 32, Vol.
[0005]
Further, the SQUID needs to be cooled using liquid helium or the like in order to maintain the superconducting state, and is usually immersed in liquid helium filled in a container called a dewar. A detection coil is disposed near the bottom of the dewar, and the detection coil and the SQUID unit are disposed so as to be constantly immersed in liquid helium. In the multi-channel SQUID sensor, a large number of combinations of detection coils and SQUID units are arranged, and the large number of detection coils are arranged near the bottom surface, and the bottom surface is a detection surface.
[0006]
Conventionally, in this biomagnetism measurement apparatus, the collection of test data as a biological activity current source has been performed using a current dipole simulator shown in FIG. That is, in the phantom 32 filled with the physiological saline solution 31, two covered wires 34a and 34b which are electrically insulated are disposed, and the leading ends of the covered wires 34a and 34b are respectively provided with covering layers. Are removed to expose the conductor, and horizontal portions 35a and 35b extending in a horizontal straight line are formed.
[0007]
Then, the current supplied from the current source drive control device 37 installed outside the phantom 32 passes through the covered conductor 34b and the horizontal portion 35b thereof, flows through the saline solution 31 as a feedback current 39, and flows horizontally through the covered conductor 34a. Returning to the current source drive control device 37 via the portion 35a, a desired current source including the current dipole portion 38 and the feedback current 37 is realized in the phantom 32.
[0008]
[Problems to be solved by the invention]
However, in such a conventional current source simulator, the current dipole portion 38 is generated by the current flowing through the horizontal portions 35a and 35b of the coated conductors 34a and 34b, that is, the current flowing through the stripped conductor portion. A possible current source is a linear one having no finite spread. On the other hand, the active current actually generated in the living body has a finite spread, and it is considered that the spread of epilepsy and the like has a spread of about several cm ² . A current source having such a spread cannot be produced, and therefore, there is a problem that a current source similar to an active current source actually generated in a living body cannot be generated. An object of the present invention is to provide a current source simulator that can generate a current source similar to an active current source actually generated in a living body with a simple configuration.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a current source simulator according to the present invention includes a phantom formed of a nonmagnetic material and filled with a conductive liquid, and a pair of electrodes disposed at predetermined positions in the phantom, An insulator covering the entire surface except for one end surface of each of the pair of electrodes, a pair of covered conductors connected to the respective electrodes, and current control means for supplying a predetermined current between the pair of covered conductors are provided. It is characterized by having.
[0010]
As the conductive liquid sealed in the phantom, physiological saline may be used, and as the non-magnetic material forming the phantom, plastic, acrylic resin, or the like may be used.
[0011]
The pair of electrodes may be formed of a material having excellent corrosiveness, for example, platinum or gold.
[0012]
The pair of electrodes may be formed so as to have a straight axis and have a uniform cross section perpendicular to the axis, for example, a rectangular cylinder, a rectangular parallelepiped, or the like.
[0013]
A material that is electrically insulating and does not transmit liquid, for example, a synthetic resin such as vinyl chloride can be used as a covering material for the covered conductor.
[0014]
The insulator can be formed of a material that is electrically insulative and impermeable to liquid, for example, vinyl chloride.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, a phantom 12 filled with a physiological saline solution 11 is entirely formed of a non-magnetic material such as plastic, and at least one surface (upper surface in the figure) is formed on the dewar bottom surface of the SQUID sensor. The shape along the bottom surface, that is, a convex spherical surface in FIG.
[0016]
One or more electrode portions 13 fixed by a non-magnetic screw or the like are provided at some predetermined positions (positions known in advance) inside the phantom 12, and the current control device 14 Control is performed so that a desired current is selectively supplied.
[0017]
FIG. 2 is an enlarged perspective view of the electrode unit 13. The electrode unit 13 basically includes a pair of electrodes 21a and 21b and a pair of covered conductive wires 22a electrically coupled to these electrodes. 22b and an insulator 23 covering the other surfaces of the electrodes 21a and 21b except for the end surfaces 27a and 27b.
[0018]
The electrodes 21a and 21b are made of a highly corrosive metal material, such as platinum, and are formed in a right cylindrical shape so that the cross section orthogonal to the axis is uniform. The coated conductive wires 22a and 22b are coated with a material that is electrically insulative and impermeable to liquid, for example, a synthetic resin such as vinyl chloride, and has one end connected to junctions 24a and 24b with the electrodes 21a and 21b and the other end connected to a current. It is electrically connected to junctions 26a and 26b with the control device 25.
[0019]
The insulator 23 is made of a material that is electrically insulative and does not transmit liquid, for example, a synthetic resin such as vinyl chloride, and is formed so as to cover all surfaces of the electrodes 21a and 21b except the end surfaces 27a and 27b. I have.
[0020]
Next, the operation of the present invention will be described. The current supplied from the current controller 14 and reaching the junction 24a with the electrode 21a via the covered conductor 22a becomes a current 28a uniformly distributed inside the electrode 21a. And reaches the end surface 27a of the electrode 21a which is not covered with the insulator 23. The current having reached the end face 27a becomes a feedback current 29 in the physiological saline 11 and reaches the end face 27b of the electrode 21b which is not covered with the other insulator 23, and is uniformly distributed again inside the electrode 21b. The current 28b flows and returns to the current controller 14 via the covered conductor 22b.
[0021]
As a result, currents 28a and 28b distributed uniformly in the electrodes 21a and 21b flow, and by appropriately setting the diameters of the electrodes 21a and 21b, a spread that actually occurs in a living body can be obtained. A current source having the same.
[0022]
In addition, as in the present embodiment, by using an electrode having a linear axis and having a uniform cross section perpendicular to the axis, the current flows almost uniformly distributed in the electrode. The advantage that the test data of the above can be easily obtained.
[0023]
In the above embodiment, the shape of the electrode is described as a right cylindrical shape.However, any electrode may be used as long as the electrode has a linear axis and a uniform cross section perpendicular to the axis, such as a rectangular parallelepiped or a plate. Good.
[0024]
【The invention's effect】
According to the current source simulator according to the present invention, since a pair of electrodes is used in the current generating portion, it is possible to form a current source having a spread that actually occurs in a living body.
[Brief description of the drawings]
FIG. 1 is an overall schematic diagram of a current source simulator according to an embodiment of the present invention.
FIG. 2 is an enlarged view of an electrode portion of the current source simulator according to the present invention.
FIG. 3 is a diagram showing a conventional current source simulator.
[Explanation of symbols]
11 physiological saline 12 phantom 13 current source simulator 14 current control devices 21a and 21b electrodes 22a 22b ... covered conductor 23 ... insulators 24a, 24b ... junctions 26a, 26b between electrodes and conductors ... junctions 27a, 27b between selection drive control devices and conductors ... electrodes are insulated. No end faces 28a, 28b ... uniformly distributed current 29 in the electrode ... feedback current

Claims (1)

A phantom formed of a non-magnetic material and filled with a conductive liquid, and a pair of electrodes disposed at predetermined positions in the phantom, made of a metal material, having a straight axis and having a uniform cross section orthogonal to the axis. And an insulator covering the entire surface except for one end surface of each of the pair of electrodes, a pair of covered conductors connected to the respective electrodes, and current control means for supplying a predetermined current between the pair of covered conductors, A current source simulator comprising:

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