JP2000100359A - X-ray image tube device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray image tube device capable of eliminating magnetic field which exists in the surrounding and correcting image distortion. SOLUTION: This device is formed out of an X-ray image tube 12, having a vacuum envelope for storing an input part for receiving an X-ray image and an output part for sending out an output image corresponding to the X-ray image respectively, a tube vessel 13 for housing the X-ray image tube 12, and a plurality of magnetic field generation coils C1 and C2 arranged so as to surround the outside of the X-ray image tube 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an X-ray image tube apparatus for correcting image distortion caused by a peripheral magnetic field such as geomagnetism.

[0002]

2. Description of the Related Art An X-ray image tube is an X-ray tube that transmits an X-ray.
An electron tube for converting a line image into a visible image, which is widely used in X-ray diagnostic apparatuses and the like. The X-ray image tube is entirely composed of a vacuum envelope, and an input section for converting X-rays into a flow of electrons is provided at one end in the vacuum envelope. A focusing electrode and an anode forming an electrostatic electron lens system for accelerating and focusing the flow of electrons are arranged behind the input unit. Also,
The other end in the vacuum envelope is provided with an output unit for converting the flow of electrons into visible light. The internal space of the vacuum envelope constituting the X-ray image tube is maintained in a high vacuum state, and electrons travel between the input unit and the output unit.

For this reason, when a magnetic field enters the inside of the X-ray image tube, the traveling electron receives Lorentz force and changes its trajectory. In order to prevent such a change in the electron trajectory, for example, there is a method of arranging a thin magnetic shielding plate at an input window portion of an X-ray image tube. The magnetic shielding plate is usually formed of a magnetic material having a high magnetic permeability and a small coercive force.
And a thickness of about 100 μm is used.

[0004]

In the conventional X-ray image tube apparatus, a magnetic shielding plate is disposed at an input window of the X-ray image tube in order to prevent a magnetic field from entering from the outside. The thicker the magnetic shielding plate, the greater the effect of shielding external magnetism.
However, a material having a large atomic number is usually used for the magnetic shielding plate. Therefore, when the thickness of the magnetic shielding plate is increased, the amount of X-rays entering the X-ray image tube decreases. as a result,
The quantum noise of the image increases, and the brightness of the X-ray image tube decreases. Accordingly, there is a problem that the X-ray dose to the subject increases.

Therefore, a coil is arranged around the input window of the X-ray image tube instead of the magnetic shielding plate made of a ferromagnetic material,
There is a method of generating a correction magnetic field inside the X-ray image tube by using a coil to cancel the magnetic field entering the X-ray image tube (see Japanese Patent Application Laid-Open No. 63-121239 and US Pat. No. 3,809,889).

A coil for generating a correction magnetic field has, for example, a structure as shown in FIG. Reference numeral 91 denotes a coil which is formed by winding an enameled wire around 70 turns to 1500 turns. Further, the entire periphery of the coil 91 is bundled with an insulating tape 92 so that the coil 91 is not separated. Then, as shown in FIG. 2B, terminals 91 a and 91 b provided at both ends of the coil 91 are connected to a DC power supply 93, and a current flows through the coil 91.

The method using a coil can only partially correct distortion of an X-ray image due to a magnetic field. For this reason, image distortion cannot be reliably corrected. Therefore, there is a method in which a thin magnetic shielding plate made of a ferromagnetic material and a coil are used in combination (see Japanese Patent Application Laid-Open No. 8-315575).

However, the magnitude of the magnetic field entering the X-ray image tube varies depending on the environment in which the X-ray image tube is placed, for example, the orientation in which the tube is placed. Therefore, when the image distortion due to the magnetic field is corrected by the coil, it is necessary to adjust the value of the current according to the direction of the X-ray image tube. However, adjustment of the current flowing through the coil is not easy, and image distortion cannot be sufficiently eliminated.

For this reason, there is a method in which the intensity of a magnetic field penetrating into an X-ray image tube is detected by a sensor, and a current flowing through a coil is determined based on information on the intensity of the magnetic field (Japanese Patent Laid-Open No. 7-99).
033 and JP-A-7-210744).

In this method, for example, a Hall element is used as a sensor for detecting the intensity of a magnetic field. The Hall element has a characteristic that a zero magnetic field easily drifts. Therefore, a small magnetic field of about 0.3 to 0.5 Gauss around the X-ray image tube cannot be accurately measured, and the image distortion cannot be eliminated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and to provide an X-ray image tube apparatus for canceling a magnetic field existing in the surroundings and correcting image distortion.

[0012]

SUMMARY OF THE INVENTION The present invention provides an X-ray image tube having a vacuum envelope containing an input section for inputting an X-ray image and an output section for outputting an output image corresponding to the X-ray image. And an X-ray image tube apparatus comprising: a tube container for accommodating the X-ray image tube; and a magnetic field generating coil arranged so as to surround the outside of the X-ray image tube. It is characterized by.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. Reference numeral 11 denotes X-ray image tube devices. These X-ray image tube devices 11 are arranged in different directions with respect to an external magnetic field indicated by an arrow Y. The X-ray image tube device 11 includes an X-ray image tube 12, and
It is composed of a tube container 13 for storing an X-ray image tube. The X-ray image tube 12 is entirely composed of a vacuum envelope, and although not shown in the drawing, an input portion for converting X-rays into a flow of electrons is provided at one end in the vacuum envelope. A focusing electrode and an anode forming an electrostatic electron lens system for accelerating and focusing the flow of electrons are arranged behind the input unit. An output unit for converting the flow of electrons into visible light is provided at the other end in the vacuum envelope.

Each X-ray image tube apparatus 11
Are provided with first and second, for example, two magnetic field generating coils C1, C2. Magnetic field generating coils C1, C
2 is provided in the vicinity of the input window 14 of the X-ray image tube 12, for example, slightly in front of the input window 14 and inside the tube container 13, and is provided along the axial direction of the X-ray image tube 12. ing. The tube container 13 is made of a ferromagnetic material and protects the magnetic field from the lateral direction from entering the X-ray image tube 12. In addition, the line segment mm indicates the tube axis.

In the case of the above configuration, almost no image distortion due to the external magnetic field Y is observed in the X-ray image tube apparatus 11 (position A) arranged in a direction orthogonal to the external magnetic field Y. However, the X-ray image tube apparatus 11 at the position B where the tube axis is at 45 ° to the external magnetic field Y or at the position C where the tube axis is parallel to the external magnetic field Y has the X-ray image tube 12.
The external magnetic field Y enters through the input window 14 of, and image distortion appears. At this time, the external magnetic field Y entering the X-ray image tube 12
Is larger at position C than at position B.

The magnitude of the external magnetic field Y entering the X-ray image tube apparatus 11 varies depending on its direction and the like. Therefore, the X-ray image tube apparatus 11 at the position A sets the current to 0 without flowing the current to any of the two magnetic field generating coils C1 and C2, and at the position B, the predetermined value is applied to one of the two magnetic field generating coils C1 and C2. Electric current is flowing. At position C, 2
A current of a predetermined value is supplied to each of the two magnetic field generating coils C1 and C2. As described above, each X-ray image tube device 11 has two magnetic field generating coils C corresponding to the magnitude of the external magnetic field Y entering the X-ray image tube 12.
1. The current flowing through C2 is controlled. At this time, a correction magnetic field corresponding to the magnitude of the external magnetic field Y is formed in each of the X-ray image tube devices 11 by the two magnetic field generating coils C1 and C2, thereby preventing image distortion due to the external magnetic field.

In the above embodiment, two magnetic field generating coils are arranged around the input window of the X-ray image tube. However, the magnitude of the magnetic field penetrating from the outside changes to various values depending on the direction of the X-ray image tube device. In such a case, if three or more magnetic field generating coils are arranged so as to surround the outer peripheral portion of the input window of the X-ray image tube, for example, and the number of magnetic field generating coils through which current flows is appropriately set, the magnetic field generating coil can be formed. An X-ray image tube device that can precisely control the correction magnetic field generated by the coil and can cope with external magnetic fields of various magnitudes is realized.

In the above embodiment, the magnetic field generating coil is arranged around the input window of the X-ray image tube. However, the magnetic field generating coil can be arranged at any position as long as it is inside the tube vessel surrounding the X-ray image tube.

Further, in the above embodiment, the same predetermined value current is applied to one magnetic field generating coil. However, the resistance values of the plurality of magnetic field generating coils provided in one X-ray image tube device may be made different from each other so that a different current flows for each magnetic field generating coil.
For example, when the resistance values of a plurality of magnetic field generating coils are different, even if the same voltage is applied to each of the magnetic field generating coils, a different current flows through each of the magnetic field generating coils, and correction of a different magnitude for each magnetic field generating coil is performed. A magnetic field is generated. Therefore, by appropriately selecting a magnetic field generating coil through which a current flows according to the magnitude of the external magnetic field, it is possible to generate a correction magnetic field corresponding to an uneven external magnetic field having various magnitudes.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In FIG. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and duplicate description will be partially omitted.

In this embodiment, a reinforcing layer 21 is provided inside the tube container 13 with a metal material such as aluminum for mechanically reinforcing the tube container 13 or a reinforced resin. Then, for example, four magnetic field generating coils C1 to C4 are arranged between the tube container 13 and the reinforcing layer 21 in the tube axis direction.

When a shielding layer made of lead or the like for shielding leakage of X-rays is provided in place of the reinforcing layer 21 inside the tube container 13, a space between the tube container and the shielding layer is provided. And the magnetic field generating coils C1 to C4 may be arranged.

In the case of the above configuration, the magnetic field generating coil is arranged between the tube container and the reinforcing layer or between the tube container and the shielding layer. For this reason, the space between the tube container and the X-ray image tube can be effectively used, and the provision of the magnetic field generating coil does not increase the size of the entire apparatus.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In FIG. 3, portions corresponding to FIG. 1 and FIG. 2 are denoted by the same reference numerals, and overlapping description is partially omitted.

In this embodiment, two magnetic field generating coils C1 and C2 surround the outside of the input window 14 of the X-ray image tube 12.
2, and another magnetic field generating coil C3 is arranged at a position surrounding the outside of the X-ray image tube a little ahead of the output unit formed in the X-ray image tube.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. FIG. 4 shows one of the magnetic field generating coils,
For example, the magnetic field generating coil C1 is shown extracted. One end a of the magnetic field generating coil C1 is connected to one output terminal 41a of the constant current power supply 41. The other end b of the magnetic field generating coil C1 is connected to a first terminal 42b of the switch 42, and an intermediate point c of the magnetic field generating coil C1 is connected to a second terminal 42c of the switch 42. And the switch 42
Switching, the first terminal 42b or the second terminal 42c
One of the output terminals 41 of the constant current power supply 41
b.

In the above-described configuration, when a large correction magnetic field is desired to be obtained, the first switch is switched by switching the switch 42.
The terminal 42b is connected to the other output terminal 41b of the constant current power supply 41. To obtain a small correction magnetic field, the second terminal 42c is connected to the other output terminal 41b of the constant current power supply 41 by switching the switch 42.

At this time, the correction magnetic field B generated by the magnetic field generating coil C1 has a relationship of B = nI (n is the number of turns of the coil, and I is a current flowing through the coil). Therefore, the first terminal 4
When 2b is connected to the constant current power supply 41, the number of turns of the magnetic field generating coil increases, and the correction magnetic field increases. Conversely, when the second terminal 42c is connected to the constant current power supply 41, the number of turns of the magnetic field generating coil decreases, and the correction magnetic field decreases.

According to such a configuration, by switching terminals for supplying current to the magnetic field generating coil C1,
The magnitude of the generated correction magnetic field can be adjusted, and image distortion due to an irregular and non-uniform external magnetic field can be reliably prevented.

In the above embodiment, the magnetic field generating coil is provided with one intermediate point. However, if a plurality of intermediate points are provided in the magnetic field generating coil and the connection state between the plurality of intermediate points and the constant current power supply can be switched, a correction magnetic field having various values according to the number of intermediate points can be obtained. Can occur.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. FIG. 5 shows one of the magnetic field generating coils,
For example, the magnetic field generating coil C1 is shown extracted. In FIG. 5, parts corresponding to those in FIGS. 3 and 4 are denoted by the same reference numerals, and duplicate description is partially omitted. One end a of the magnetic field generating coil C1 is connected to one output terminal 41a of the constant current power supply 41.
It is connected to the. The other end b of the magnetic field generating coil C1 is connected to the other output terminal 41b of the constant current power supply 41 via a variable resistor 51 whose resistance value can be changed.

In this case, assuming that the output voltage of the constant current power supply 41 is V, the resistance of the magnetic field generating coil is R1, and the resistance of the variable resistor 51 is R2, the current I flowing through the magnetic field generating coil C1 is I = V / (R1 + R2).

Therefore, if the resistance value R2 of the variable resistor 51 is changed, the current I flowing through the magnetic field generating coil C1 changes, and various correction magnetic fields can be obtained from one magnetic field generating coil C1. Note that the variable resistor 51 is provided as shown in FIG.
As shown in (1), it may be provided near the magnetic field generating coils C1 and C2, or may be provided in a power supply unit (not shown) for operating the X-ray image tube. Alternatively, it can be provided near the constant voltage power supply 41 for the magnetic field generating coil.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. FIG. 6 is a diagram illustrating a portion of the magnetic field generating coil extracted. FIG. 6B is a sectional view taken in a direction orthogonal to the tube axis of the X-ray image tube, and shows a tube container portion and a magnetic field generating coil portion. Code 65
Is a cylindrical tube container constituting the X-ray image tube device,
For example, it is formed of aluminum. The inner middle portion 66 is made of permalloy, and the innermost portion 67 is made of permalloy.
Is formed of a lead cylinder. And the innermost part 67
Magnetic field generating coil C using an adhesive or the like on the inner surface of the lead cylinder
0 is fixed. In addition, coated electric wires 63a and 63b for power supply are connected to both ends of the magnetic field generating coil C0.
These insulated wires 63a and 63b are connected to a constant current power supply 64.

In the above configuration, the magnetic field generating coil C
By utilizing the characteristic that 0 is a thin plate, if it is sandwiched between the permalloy of the intermediate portion 66 and the lead cylinder of the innermost portion 67,
In particular, the magnetic field generating coil C0 can be fixed without providing a fixing mechanism.

Here, the structure of the above-described magnetic field generating coil C0 will be described with reference to FIG. The magnetic field generating coil C0 is a flexible substrate 6
The structure is such that a conductive pattern p for forming a magnetic field generating coil is provided on 1a to 61h and 62a to 62h. The conductive patterns p of the flexible substrates 61a to 61h and the conductive patterns p of the flexible substrates 62a to 62h are connected to each other by connection terminals t. The conductive patterns p of the flexible boards 61a to 61h located on the left side of the figure and the conductive patterns p of the flexible boards 62a to 62h located on the right side of the figure.
Although not shown in the figure, the same numbers 1 to 8 are used as one conductive pattern at an extension of the figure, for example, at a position opposite to the side where the covered electric wires 63a and 63b are provided in FIG. It is connected as.

It is to be noted that the flexible substrates 61a to 61h located on the left side of FIG.
For example, reference numeral 61h is connected to a covered electric wire 63a for power supply, and the covered electric wire 63a is connected to a constant current power supply 41. Also, the flexible substrate 62 located on the right side of the drawing
a to 62h of the endmost flexible substrate, for example, 6
A covered electric wire 63b for power supply is connected to 2a, and the covered electric wire 63b is connected to a constant current power supply 64.

Therefore, when the magnetic field generating coil C0 having the above-described configuration is arranged on the inner surface of the inner portion 67 in FIG. 6A, a plate-shaped magnetic field generating coil C0 having a conductive pattern p portion formed in an annular shape is formed. You.

The allowable value of the current flowing through the conductive pattern p is defined. Therefore, the necessary current value is grasped in advance, and the width of the conductive pattern p is determined.

Further, if the flexible substrate provided with the conductive pattern is formed in multiple layers, the number of turns can be easily increased. In addition, when the correction magnetic field is formed to be wide in the tube axis direction of the X-ray image tube, a wide flexible substrate is used, and by increasing the interval between the conductive patterns, the correction can be performed in a wide range in the tube axis direction of the X-ray image tube. A magnetic field can be formed. Further, if the resistance value of the material of the conductive pattern is changed, the flowing current changes, and a correction magnetic field of various values can be formed.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In this embodiment, a magnetic field generating coil C0 having a certain width and having the structure described with reference to FIG. 6 is disposed in close contact with the inside of the annular wall portion of the tube container 71. , A thin cylindrical support member 72 is disposed. In this case, the support member 72 is configured to generate a force that tends to spread outward, and the force of the support member 72 is used to fix the magnetic field generating coil C0. Reference numeral 73 denotes a fixing member for fixing the X-ray image tube 74 to the tube container 13. Also, the line segment m
-M indicates a tube axis.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. 8, parts corresponding to those in FIG. 7 are denoted by the same reference numerals, and duplicate description will be partially omitted.

In this embodiment, a lead shield layer 81 is formed inside a tube container 71. Shield layer 81
Is formed with a concave portion 81a dented inward in a partial area in the axial direction. In the region of the concave portion 81a of the shield layer 81, a narrow space is formed between the shield layer 81 and the tube container 71, and a thin plate-shaped magnetic field generating coil C0 is arranged in the space.

In the embodiments shown in FIGS. 7 and 8, a thin plate-shaped magnetic field generating coil C0 formed by providing a conductive pattern on a flexible substrate is fixed using a wall portion of a tube container or the like. However, it is also possible to form a magnetic field generating coil by applying an insulating sheet to the inner surface of a shield layer made of lead or the like provided inside the tube container, and applying a conductive resin to the inner surface of the insulating sheet in a coil shape. .

According to the configuration of the present invention described above, correction magnetic fields having various magnitudes can be easily generated. Therefore, it is possible to realize an X-ray image tube apparatus that cancels out irregular and uneven magnetic fields existing in the surroundings and prevents image distortion. In addition, when the magnetic field generating coil is configured using a flexible substrate, it is possible to prevent the entire device from being enlarged,
Further, an X-ray image tube device in which the magnetic field generating coil can be easily mounted can be obtained.

[0046]

According to the present invention, it is possible to realize an X-ray image tube apparatus for canceling a magnetic field existing in the surroundings and correcting image distortion.

[Brief description of the drawings]

FIG. 1 is a schematic structural diagram for explaining an embodiment of the present invention.

FIG. 2 is a schematic structural diagram for explaining another embodiment of the present invention.

FIG. 3 is a schematic structural diagram for explaining another embodiment of the present invention.

FIG. 4 is a schematic structural diagram for explaining another embodiment of the present invention.

FIG. 5 is a schematic structural diagram for explaining another embodiment of the present invention.

FIG. 6 is a schematic structural diagram for explaining another embodiment of the present invention.

FIG. 7 is a schematic structural diagram for explaining another embodiment of the present invention.

FIG. 8 is a schematic structural diagram for explaining another embodiment of the present invention.

FIG. 9 is a schematic structural diagram for explaining a conventional example.

[Description of Signs] 11 X-ray image tube device 12 X-ray image tube 13 Tube container 14 Input window C1, C2 Magnetic field generating coil

Claims (7)

[Claims] 1. An input unit for inputting an X-ray image and the X-ray image
An X-ray image tube having a vacuum envelope accommodating an output section for outputting an output image corresponding to the X-ray image;
An X-ray image tube apparatus comprising a tube container for accommodating a line image tube and a magnetic field generating coil arranged to surround the outside of the X-ray image tube, wherein a plurality of the magnetic field generating coils are provided. X-ray image tube device. 2. The X-ray image tube apparatus according to claim 1, wherein the plurality of magnetic field generating coils have different resistance values. 3. An input unit to which an X-ray image is inputted, and said X-ray image
An X-ray image tube having a vacuum envelope accommodating an output section for outputting an output image corresponding to the X-ray image;
In an X-ray image tube device comprising a tube container for accommodating a X-ray image tube and a magnetic field generating coil arranged so as to surround the outside of the X-ray image tube, a variable resistor capable of adjusting a resistance value of the magnetic field generating coil is provided. An X-ray image tube device which is connected. 4. An input unit for inputting an X-ray image and said X-ray image
An X-ray image tube having a vacuum envelope accommodating an output section for outputting an output image corresponding to the X-ray image;
In an X-ray image tube device comprising a tube container for accommodating a X-ray image tube and a magnetic field generating coil arranged so as to surround the outside of the X-ray image tube, terminals are provided at three or more positions of the magnetic field generating coil. An X-ray image tube apparatus characterized in that a current supply power source is connected between any two of the three or more terminals by switching. 5. An input unit for inputting an X-ray image and the X-ray image
An X-ray image tube having a vacuum envelope accommodating an output section for outputting an output image corresponding to the X-ray image;
In an X-ray image tube apparatus comprising a tube container for accommodating a X-ray image tube and a magnetic field generating coil arranged so as to surround the outside of the X-ray image tube, the magnetic field generating coil forms a conductive pattern on a flexible substrate An X-ray image tube apparatus characterized by having a structure as described above. 6. A reinforcing layer for reinforcing the tube container or a shielding layer for shielding leakage of X-rays is provided inside the tube container, and between the tube container and the reinforcing layer or between the tube container and the shielding layer. The X-ray image tube device according to any one of claims 1 to 5, further comprising a magnetic field generating coil provided between the X-ray tube and the magnetic field generating coil. 7. A shielding layer for shielding leakage of X-rays is provided inside the tube container, and a concave portion is formed in which a part of the shielding layer is inwardly recessed so as to have a gap between the tube container and the tube container. 6. The X-ray image tube device according to claim 5, wherein a magnetic field generating coil is disposed in the recess.