JPH0963519A - X-ray image tube device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray image tube device giving a good output picture image without being affected by ambient magnetic fields such as geomagnetism. SOLUTION: An image device is constituted by an input window 14 to which X-rays are inputted, an input screen 16 for transforming X-rays inputted through this input window 14 into electrons, an X-ray image tube 15 equipped with electrodes 17, 18 for accelerating/focusing the electrons and with an output screen 19 for converting the accelerated/focused electrons into an output signal, and a magnetic flux generating coil 13 spirally formed of an electrically conductive material of high X-ray transmittance and positioned in the path of the X-rays inputted to the input window 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray image tube device in which the influence of a magnetic field input from the outside is reduced.

[0002]

2. Description of the Related Art A conventional X-ray image tube device is shown in FIG.
This will be described with reference to 0.

Reference numeral 101 denotes an X-ray source. X-rays emitted from the X-ray source 101 pass through an object (not shown), and an arrow 102
Go in the direction. Then, it enters the X-ray image tube 104 through the input window 103. The X-rays incident on the X-ray image tube 104 enter the input screen 105. The input screen has a two-layer structure of an input phosphor screen 105a and a photocathode 105b, and X-rays are converted into light at the input phosphor screen 105a. Then, it is converted into photoelectrons on the photocathode 105b and emitted into the vacuum inside the X-ray image tube 104. The photoelectrons are accelerated and focused by the grid electrode 106 and the anode 107 provided in the X-ray image tube 104 and focused on the output surface of the output screen 108. Then, on the output screen 108, for example, it is converted into an electric signal and outputted. The X-ray image tube 104 is the outer container 10
It is stored in 9. A magnetic shield layer 110 is formed inside the outer container 109.

Reference numeral 111 denotes a magnetic shield plate, which is made of a material such as permalloy having a high magnetic permeability and is used in the outer container 109.
It is located in the opening at the front end. Further, 112 is a magnetism generating coil, which is arranged around the input window 103. The functions of the magnetic shield plate 111 and the magnetic field generating coil 112 will be described later.

[0005]

The X-ray image tube device having the above-described structure is used in medical X-ray diagnostic devices, industrial nondestructive inspection devices and the like. These devices are often used in the presence of terrestrial magnetism and other external magnetic fields. In such a case, when an external magnetic field (the line of magnetic force is indicated by an arrow F) enters the inside of the X-ray image tube 104,
The orbit of the photoelectrons traveling in the X-ray image tube 104 is disturbed, and so-called S-shaped distortion of the image is generated.

Here, the S-shaped distortion will be described. The input screen 105 of the X-ray image tube 104 has a curved surface. Therefore, the photocathode 105 of the input screen 105
Near the photocathode 105b, the photoelectrons emitted from b into the vacuum travel in a direction intersecting the magnetic field lines F of the external magnetic field entering from the input window 103. Therefore, the Lorentz force due to the external magnetic field acts on the photoelectrons, and their orbits are affected. In this case, the influence on the orbit of the photoelectrons is not uniform in the entire area of the photocathode 105b.

For example, in the peripheral portion of the input window 103, the external magnetism is absorbed by the magnetic shield 110 built in the outer container 109. Therefore, the external magnetism in the peripheral portion becomes coarse and the influence of the external magnetic field is small. External magnetism penetrates densely in the central part. However, when the line of magnetic force of the external magnetic field is parallel to the central axis of the image tube 104, the angle at which the line of magnetic force intersects the traveling direction of the photoelectrons is small. Therefore, the Lorentz force acting on the photoelectrons is small, and the change in the orbit is small.

External magnetism invades densely in the intermediate portion located between the central portion and the peripheral portion. In addition, the distance that intersects the magnetic field lines of the external magnetic field becomes long, and the change in the orbit becomes large. For this reason, the output image is twisted in the rotational direction, and the straight line image as shown by the dotted line D in FIG. 11 becomes like the solid line J, so as to prevent the above-mentioned S-shaped distortion in which so-called S-shaped distortion occurs. For example, there is a method in which the magnetic shield plate 111 (FIG. 10) is arranged in front of the input window 103 to block the external magnetic field entering through the input window 103. However, since the magnetic shield plate 111 attenuates X-rays,
The image noise of the line image tube increases, and the brightness decreases.

Further, there is a method of arranging a magnetic field generating coil 112 (FIG. 10) for correcting the external magnetic field around the input window 103 instead of the magnetic shield plate 111 (US Pat. No. 38, 38).
09889). This is the magnetic generation coil 1
In this method, a current is passed through 12 to generate a magnetic field to cancel the external magnetic field. However, in the case of this method, for example, if the current flowing through the magnetic field generating coil 112 is adjusted so as to correct the S-shaped distortion in the peripheral portion, the correction in the intermediate portion becomes insufficient. On the contrary, if the S-shaped distortion in the middle part is corrected, the peripheral part is excessively corrected. Therefore, the S-shaped distortion cannot be made zero.

There is also a method for adjusting the reading mode of the target of the television camera connected to the X-ray image tube according to the measured value of magnetostriction (Japanese Patent Laid-Open No. 2-2).
(See Japanese Patent No. 10744). In this method, the distortion is corrected by the television camera, and the output image itself of the X-ray image tube is not corrected. Therefore, it cannot be used, for example, in X-ray cinematography.

The present invention solves the above-mentioned drawbacks, and an object of the present invention is to provide an X-ray image tube apparatus which can obtain a good output image without being affected by the surrounding magnetic field such as the earth's magnetism.

[0012]

An X-ray image tube device according to the present invention includes an input window for inputting X-rays, an input screen for converting X-rays input through the input window into electrons, and an electrode for accelerating and focusing the electrons. And an X-ray image tube provided with an output screen for converting the electrons accelerated and focused by the electrodes into an output signal, and an electric conductor and an X-ray transparent body, which is located in the passage of the X-ray input to the input window. And a magnetic field generating coil formed by spirally forming a material having a high ratio.

Further, the magnetic field generating coil is fixed to the front surface of the input window of the X-ray image tube, and the magnetic field generating coil and the input window are electrically insulated.

Further, an input window for inputting X-rays, an input screen for converting X-rays input through the input window into electrons, an electrode for accelerating and focusing the electrons, and electrons accelerating and focusing by the electrodes as output signals. An X-ray image tube provided with an output screen for conversion, an outer container for accommodating the X-ray image tube therein, and a plurality of split coils arranged in an annular shape, and a magnetic field generator disposed inside the outer container. And a coil. Further, the currents flowing through the plurality of split coils can be controlled independently.

Further, the split coil is composed of a line that reciprocates at a position close to each other, and the magnetic field generated from a part of the line is shielded.

[0016]

According to the above construction, the magnetic field generating coil, which is made of a material having a high X-ray transmissivity in the form of an electric conductor, is arranged in the passage of the X-ray input to the input window. Then, a magnetic field that cancels the external magnetic field can be generated by passing a current through the magnetic field generating coil. The magnetism generating coil is arranged in the X-ray passage. Therefore, for example, by making the interval of the spirals forming the magnetic field generating coil denser in the part corresponding to the middle part of the input window than in the peripheral part and the central part, it is possible to make a large correction for a region requiring strong correction. Correction can be performed and S-shaped distortion can be effectively eliminated. Further, the magnetic field generating coil formed in a spiral shape can be formed in a plurality of layers. In this case, the magnetic field distribution for correction can also be adjusted by shifting the spiral formation position between the magnetic field generating coils located in the upper and lower layers.

Further, when the magnetism generating coil is fixed to the front surface of the input window of the X-ray image tube, the location where the photoelectrons are emitted and the magnetism generating coil are close to each other, and the trajectory of the photoelectrons can be surely corrected.

Further, the magnetic field generating coil is formed by a plurality of split coils arranged in an annular shape. In this case, the correction magnetic field according to the external magnetic field can be generated by controlling the current flowing through each split coil by making the currents flowing through the multiple split coils equal or different. Therefore, not only the S-shaped distortion that is symmetrical about the axis but also the S that is not symmetrical about the axis
Character distortion can also be corrected.

Further, the split coil is composed of a line that reciprocates at a position close to each other, and has a structure for shielding a magnetic field generated from a part of the line. In this case, the magnetic fields generated in the reciprocating lines do not cancel each other, and the magnetic field for correction with respect to the external magnetic field can be reliably generated.

[0020]

An embodiment of the present invention will be described with reference to FIG.

Reference numeral 11 denotes an X-ray source, and the X-rays emitted from the X-ray source 11 pass through a subject (not shown) and proceed as shown by an arrow 12. Then, the magnetic field generating coil 13 enters the X-ray image tube 15 through the input window 14 formed on the surface.
X-rays incident on the X-ray image tube 15 are input screen 1
Enter 6. The input screen 16 includes an input phosphor screen 16a and a photocathode 16b, and X-rays are converted into light at the input phosphor screen 16a. The light converted by the input fluorescent screen 16a is converted into photoelectrons by the photocathode 16b and emitted. Photoelectrons are generated by the grid electrode 1 provided in the X-ray image tube 15.
Output screen 1 accelerated and focused by 7 and anode 18
9 is imaged on the output surface. Then, on the output screen 19, for example, it is converted into an electric signal and outputted. Note that X
The entire line image tube is housed in the outer container 20.
A magnetic shield layer 21 is formed inside the outer container 20. The arrow F indicates the line of magnetic force due to the external magnetic field.

The magnetic field generating coil formed on the surface of the input window will be described with reference to FIG. FIG. 2 is a diagram showing a portion near the input window, and portions corresponding to those in FIG. 1 are designated by the same reference numerals. Reference numeral 15 is an X-ray image tube, and the X-ray image tube 15 is housed in an outer container 20. A magnetic shield layer 21 is provided inside the outer container 20. Further, behind the input window 14 inside the X-ray image tube 15,
An input screen 16 is located which converts X-rays into photoelectrons. Further, an arrow F indicates a magnetic force line of an external magnetic field incident in the tube axis direction of the X-ray image tube, and an arrow Fa indicates a state where the magnetic force line is pulled toward the magnetic shield layer 21 side.

The magnetic field generating coil 13 is connected to the input window 1
4 is coated with a thin film insulating material to form a thin film insulating layer 251, and then, for example, a metal material having a high X-ray transmittance is spirally deposited on the thin film insulating layer 251 to form a coil pattern 2
61 is formed. In this case, resin, ceramics, glass or the like is used as the thin film insulating material. Further, the thin film insulating layer 251 is formed not only by vapor deposition but also by a method such as adhesion, coating, or thermal spraying. As the metal material, a metal having a high X-ray transmittance such as aluminum or magnesium is used. These metals are vapor-deposited on the thin film insulating layer 251, or a conductive solvent is spirally formed on the thin film insulating layer 251. A coil pattern is formed by coating.

For example, aluminum is spirally vapor-deposited on the thin-film insulating layer 251 to have a thickness of 10 μm and a width of 1 mm from the peripheral portion to the central portion of the input window 14 to form the first coil pattern 261. Then, the thin film insulating layer 252 is formed on the first coil pattern 261, and the second coil pattern 26 is formed by shifting the position on the thin film insulating layer 252 so as not to overlap the first coil pattern 261.
2 is made of aluminum. By repeating such steps, for example, about 10 coil patterns are formed. Then, the first coil pattern and the last coil pattern are connected to the power supply 27. The coil patterns located in the middle are connected to each other so that current flows through all the coil patterns in order.

Here, a structure in which a part of the magnetism generating coil is enlarged is shown in FIG. In FIG. 3, 31 is an input window, and 251-2.
Reference numeral 54 is a thin film insulating layer, and 261 to 264 are coil patterns. Incidentally, the magnetic field generating coil composed of a plurality of thin film insulating layers and a plurality of layers of coil patterns, between the vertically adjacent coil patterns, except for the portions that are connected to each other,
Usually, it is insulated by a thin film insulating layer. In addition, the direction of the current flowing through each coil is unified in one direction,
The correction magnetic field for correcting the external magnetic field is efficiently generated. In this case, for example, if the external magnetic field is about 0.5 Gauss, it can be corrected with a current of 10 mA or less.

Further, in one coil pattern, if the distance between the lines is narrower in the middle part than in the center part and the peripheral part of the input window, a large correction magnetic field can be generated in the middle part which requires strong correction. , S-shaped distortion can be effectively corrected.

In the above embodiment, the magnetic field generating coil 13 is formed on the surface of the input window 14 of the X-ray image tube 15. However, as shown in FIGS. 4A and 4B, the magnetic field generating coil 13 is formed on the surface or inside of the convex substrate 41 having a high X-ray transmittance in the same structure as in FIG. The formed convex substrate 41 may be arranged in front of the input window 5 of the X-ray image tube. At this time, the external magnetic field (arrow 42) incident on the X-ray image tube
Can be canceled by the correction magnetic field (arrow 43) generated by the magnetism generating coil 13. The material of the convex substrate 41 may be carbon fiber or various resins such as epoxy resin or vinyl chloride resin, or a magnetic shield material having a thickness of 100 μm or less. In addition, 44 is an X-ray image tube and 45 is an outer container.

Further, as shown in FIG. 5, a magnetic shield device can be constructed using a grid plate for removing scattered X-rays formed in a convex shape. Grid plate 5 for removing scattered X-rays
In No. 1, materials such as lead that absorb X-rays are arranged in a mesh shape or a honeycomb shape as indicated by a dotted line 52 in the figure. Therefore, by using lead, tungsten, molybdenum, etc. arranged in a mesh shape or a honeycomb shape, for example, the lead members located on the spiral are electrically connected in order, and the magnetic generation coil 13 is formed by the lead connected in the spiral shape. To form. Then, the lead located at both ends thereof is connected to the power source 53. In this case as well, a magnetic field for correction can be generated by passing an electric current through the lead that is spirally connected. It is desirable that the spirally connected lead and the other lead are electrically insulated. Further, the inner spacer should not be made of a conductor such as aluminum but should be made of resin or wood so that the leads forming the adjacent spirals are electrically insulated from each other. Next, another example of the magnetic field generating coil will be described with reference to FIG.

In this embodiment, the magnetic field generating coil is composed of six split coils 61a to 61f. For example, the six split coils 61a to 61f are arranged in a ring shape so as to form one ring, and are arranged so as to surround the input window 62 as a whole. 63 is an outer container, 64
Is a magnetic shield layer formed inside the outer container 63. The magnetic field generating coil having such a structure is used in the outer container 73.
7 inside the X-ray image tube 72, for example, at a position surrounding the main part of the input window 73 of the X-ray image tube 72, or at an intermediate portion of the X-ray image tube 72 as shown by reference numeral 71b. Deploy. In this case, the magnetic generation coil 7
The currents flowing through the plurality of split coils forming 1a and 71b are configured to be independently controllable.
Then, for example, the magnetic field distribution inside the outer container 74 is detected by the magnetic field sensor codes 75a and 75b, and the current flowing through each split coil is controlled according to the magnetic field distribution.

Here, the structure of one split coil constituting the magnetism generating coil will be described with reference to FIG. For example, 1
The structure is such that the line 81 of a book is reciprocated at a position close to each other so as to draw an arc, and one of the two is covered with a cylinder 82 formed of a material having a high magnetic permeability. In addition, both ends of the line are current sources 8
3 is connected. A magnetic field generating coil is formed by annularly arranging six divided coils having such a structure. It should be noted that one of the lines is partially covered with the material 82 having a high magnetic permeability so that the magnetic fields generated in the reciprocating lines do not cancel each other. In this example, the line is composed of one line, but it is also possible to form a split coil by reciprocating a plurality of lines while drawing an arc.

According to the above structure, the split coils forming the magnetism generating coil can be independently connected to the current source. Therefore, different currents can be supplied to the divided coils, and various magnetic field distributions that cannot be formed by one annular coil, for example, magnetic field distributions that are not axially symmetric can be formed inside the outer container. Therefore, as shown in FIG. 7, magnetic field sensors 75 a, 7 a for detecting the magnetic field distribution inside the outer container 74.
5b can be arranged at a position close to, for example, an electron lens of the X-ray image tube 72, and the current flowing through each split coil can be controlled according to the distribution of the magnetic field detected by the magnetic field sensors 75a and 75b. In this case, the magnetic field sensors 75a, 7
The output of 5b may be fed back to a current source or a control circuit for the current source, and a desired magnetic field may be formed by automatically controlling the current flowing through the split coils.

With this structure, the influence of the external magnetic field can be automatically corrected. Therefore, even if a medical X-ray diagnostic apparatus incorporating an X-ray image tube device is used in a state in which its direction changes and the influence of external magnetism changes depending on the use state, the influence of external magnetism Can be corrected automatically.

When the magnetism generating coil is composed of a plurality of split coils, various magnetic field distributions can be formed by controlling the currents flowing through the split coils. Therefore, not only the axially symmetric S-shaped distortion as shown in FIG. 11 but also the S-shaped distortion which is not axially symmetric as shown in FIG. 9 can be corrected. A magnetic resistance element, a magnetic modulator, a superconducting quantum interference element (SQUID), or the like can be used as the magnetic field sensor for detecting the magnetic field.

[0034]

According to the present invention, a good output image can be obtained without being affected by the surrounding magnetic field such as the earth magnetism.
A line image tube device can be realized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a magnetic field generating coil used in the present invention.

FIG. 3 is an enlarged view of a part of a magnetism generating coil.

FIG. 4 is a schematic configuration diagram showing another embodiment of the present invention.

FIG. 5 is a diagram showing another example of the magnetic field generating coil used in the present invention.

FIG. 6 is a diagram illustrating another example of the magnetic field generating coil used in the present invention.

FIG. 7 is a diagram illustrating the arrangement of magnetic field generating coils.

FIG. 8 is a diagram showing a split coil that constitutes a magnetic field generating coil.

FIG. 9 is a diagram illustrating the present invention.

FIG. 10 is a schematic configuration diagram showing a conventional example.

FIG. 11 is a diagram illustrating a conventional example.

[Explanation of symbols]

 11 ... X-ray source 13 ... Magnetic generation coil 14 ... Input window 15 ... X-ray image tube 16 ... Input screen 17 ... Grid electrode 18 ... Anode 19 ... Output screen 20 ... Outer container 21 ... Magnetic shield layer F ... Magnetic field lines

Claims (5)

[Claims] 1. An input window for inputting X-rays, an input screen for converting X-rays input through the input window into electrons, an electrode for accelerating and focusing the electrons, and an electron for accelerating and focusing by the electrodes as an output signal. An X-ray image tube having an output screen for conversion, and a magnetic field generating coil which is positioned in a path of the X-rays input to the input window and which is made of a material that is an electric conductor and has a high X-ray transmittance in a spiral shape. An X-ray image tube device comprising: 2. The magnetic field generating coil is fixed to the front surface of the input window of the X-ray image tube, and the magnetic field generating coil and the input window are electrically insulated from each other. X-ray image tube device. 3. An input window for inputting X-rays, an input screen for converting X-rays input through the input window into electrons, an electrode for accelerating and focusing the electrons, and an electron for accelerating and focusing by the electrodes as an output signal. An X-ray image tube provided with an output screen for conversion, an outer container for accommodating the X-ray image tube therein, and a plurality of split coils arranged in an annular shape, and a magnetic field generator disposed inside the outer container. An X-ray image tube device comprising a coil. 4. The X-ray image tube apparatus according to claim 3, wherein the currents flowing through the plurality of split coils can be independently controlled. 5. The split coil is composed of a line that reciprocates at a position close to each other, and has a structure in which a magnetic field generated from a part of the line is shielded.
Alternatively, the X-ray image tube device according to claim 4.