JPH07153397A - X-ray image tube - Google Patents

Abstract

PURPOSE:To provide an X-ray image tube in which deformation of an input window is prevented, and in which a correct image can be obtained even where an input phosphor layer and a photoelectric surface are provided to be tightly applied on the input window for improving contrast. CONSTITUTION:In an X-ray image tube 1, a metal holding ring 3a is pressure-welded around an input window 3 of a glass tube 2, and the metal holding ring 3a is welded with a KOV ring 4 to compose a vacuum enclosure 5. On the outermost circumference of the input window 3, a vertically and sharply standing shock absorbing part 3b is formed, and the metal holding ring 3a is pressure-welded and jointed. On the other end side of the glass tube 2, an output window 6 is formed, and an output screen 7 is formed inside the output window 6. An input phosphor layer 8b of cesium iodide including activator, and a photoelectric surface 8c are formed at a part of an effective view field of the shock absorbing part 3b of the input window 3. A focusing electrode 9 and a positive electrode 10 are disposed between the photoelectric surface 8c and the output screen 7. A lot of effects are not given to the effective view field on the inner side of the shock absorbing part 3b even when the shock absorbing part 3b is deformed at the time of jointing, thereby a correct image can be provided.

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 for converting a radiation image into a visible light image.

[0002]

2. Description of the Related Art Conventionally, in an X-ray image tube 1, as shown in FIG. 3, an input window 3 made of aluminum and a metal holding ring 3a around the input window 3 are pressed at one end of a glass tube 2, and the metal holding ring 3a is pressed. Is welded to the KOV ring 4 to be closed to form a vacuum envelope 5, an output window 6 is formed on the other end side of the glass tube 2, and an output screen 7 is provided in the output window 6. Further, an input screen 8 is provided on the inner surface side of the input window 3 with a gap from the input window 3, and the input screen 8 has a spherical shape with a thickness of about 0.5 mm as shown in FIG. On the output side, which is the concave side of the input board 8a of an aluminum plate, for example, sodium activated cesium iodide (CsI:
An input phosphor layer 8b of Na) is formed, and at least a photocathode 8c is formed on the input phosphor layer 8b. And this input screen 8 and output screen 7
Between the coaxial cylindrical focusing electrode 9 and the annular anode.
10 are arranged.

In use, as shown in FIG. 4, a radiation source 11 is arranged so as to face the input window 3, and an object such as a human body or an object is placed between the radiation source 11 and the input window 3. Sample 12
Position.

When irradiated with radiation from the radiation source 11, the input phosphor layer 8b absorbs X-rays or gamma-rays and the photocathode.
The incident X-ray image is converted into a photoelectron image by 8c, the photoelectron image is accelerated and focused by the focusing electrode 9 and the anode 10, and the output screen 7
Image as a bright light image.

The above-mentioned X-ray image tube 1 is useful for examining the internal structure of a subject 12 such as a human body or an object, and is a radiographic apparatus or radiograph for examining the transmission density distribution of irradiated X-rays. It is used as an element that converts the radiation image of the device into a light image.

Therefore, what is required of the X-ray image tube is that the contrast and resolution of the radiation image are faithfully and efficiently converted into a light image.

However, in the process in which the radiation emitted from the radiation source 11 is incident on the input window 3 through the subject 12, as shown in FIG. The decrease is remarkable, and as a result, the quantum detection efficiency is reduced, and the contrast of the output image is deteriorated.

Therefore, in order to suppress the decrease in photon number due to absorption and scattering of radiation in the input window 3, the thickness of the input window 3 or the input substrate 8a of the input screen 8 which causes absorption or scattering is made as thin as possible. It is to be.

To solve this problem, for example, FIG.
As shown in, the input phosphor layer 8b and the photocathode 8c are provided in close contact with the output side, which is the inner surface of the input window 3, and the absorption of the radiation and the scattering are eliminated by eliminating the input substrate, and an image with good contrast is obtained. It is possible to improve the quantum detection efficiency.

Further, in order to achieve both an image with good contrast and an improvement in quantum detection efficiency, an X-ray image tube in which the input surface consisting of the input phosphor layer 8b and the photocathode 8c is in close contact with the inner surface of the input window 3 1, the input window 3 is a conventional input board
It must have the same function as the photocathode that 8a played. Further, in order for the photoelectrons emitted from the photocathode to be accurately focused on the output screen 7, the shape of the input window 3 must be accurately processed and assembled.

However, the input window 3 is a metal retaining ring.
In the case where the input window 3 and the input window 3 are joined by pressure contact, the portion of the input window 3 to be joined may be pushed toward the center and deformed in the shape of the adjacent portion due to the pressure applied during the pressure contact.

Then, the deformation of the input window 3 may make it impossible to accurately emit photoelectrons in the peripheral portion, so that an accurate image may not be obtained.

[0013]

As described above, the input phosphor layer 8b and the photocathode are provided on the output side, which is the inner surface of the input window 3.
If the input substrate 8a is eliminated and absorption and scattering of radiation is eliminated to improve the contrast by providing the 8c closely, the input window 3 is pressed by the metal holding ring 3a, so that
When the input window 3 is pushed out toward the center and the shape of the adjacent portion is deformed, the deformation of the input window 3 may not allow the photoelectrons to be accurately emitted, and an accurate image may not be obtained.

The present invention has been made in view of the above problems, and an input phosphor layer and a photocathode are provided in close contact with the input window to improve the contrast and prevent the input window from being deformed to form an accurate image. It is an object to provide an obtainable X-ray image tube.

[0015]

An X-ray image tube according to claim 1, wherein an input window made of a radiation transparent material is joined to a metal retaining ring to form a part of a vacuum envelope, and the input window of the input window is formed. In an X-ray image tube in which at least an input phosphor layer and an input surface composed of a photocathode are closely attached to the inner surface, the input window is abruptly adjacent to a portion joined to the metal retaining ring. It is provided with a standing-up buffer section.

In the X-ray image tube according to the present invention, an input window made of a radiation transmissive material is joined to a metal holding ring to form a part of a vacuum envelope, and at least an input fluorescent light is provided on an inner surface of the input window. In an X-ray image tube in which an input surface including a body layer and a photocathode is closely attached, the input window has a shape in which a portion adjacent to a portion joined to the metal retaining ring sharply falls. It has a section.

[0017]

In the X-ray image tube according to the present invention, since the portion of the input window that is connected to the base body has the shock-absorbing portion having a shape that rises sharply, the input window is connected by the pressure of the metal holding ring. Even if the part is pushed out toward the center of the input window, only the raised cushioning portion is deformed, and the deformation of the input window within the effective visual field inside the cushioning portion can be suppressed,
An accurate image can be obtained.

Since the X-ray image tube according to the second aspect has the buffer portion having a shape that is sharply lowered at the portion of the input window connected to the base body, the input window is connected by the pressure of the pressure contact of the metal holding ring. Even if the portion to be pushed out is pushed toward the center of the input window, only the lowered cushioning portion is deformed, and the deformation of the input window within the effective visual field inside the cushioning portion can be suppressed, and an accurate image can be obtained. .

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the X-ray image tube of the present invention will be described below with reference to the drawings. The parts corresponding to the conventional example shown in FIGS. 3 to 6 will be described with corresponding reference numerals.

As shown in FIG. 1, the X-ray image tube 1 is
A metal retaining ring at one end of the glass tube 2 as a substrate
3a and the input window 3 are pressure-welded and airtightly joined to each other, and the KOV ring 4
Is airtightly joined to the metal holding ring 3a by welding or the like to form a vacuum envelope 5. Further, a buffer portion 3b that rises substantially vertically is formed in the peripheral portion of the input window 3 that is pressed against the metal holding ring 3a, and the metal holding ring 3a is pressed against the outside of the buffer portion 3b.

An output window 6 is formed on the other end side of the glass tube 2, and an output screen 7 having a phosphor 7b adhered on the optical glass 7a is provided in the output window 6. However, in the output screen 7, a part of the output window 6 is made of the optical glass 7a, so that the phosphor 7b is formed on the optical glass 7a.
It may be a structure in which is attached.

In addition, for example, a sodium-activated cesium iodide (CsI: Na) that emits photoelectrons by photoelectric conversion is input to a portion of the input window 3 on the inner surface on the center side of the buffer portion 3b that serves as an effective visual field. A phosphor layer 8b is provided so as to be in close contact, and a photocathode 8c is further formed on the input phosphor layer 8b to form the input screen 8 as an input surface. The input phosphor layer 8b is not limited to CsI: Na, but other alkali halide phosphors can be applied. A coaxial cylindrical focusing electrode 9 and an annular anode 10 are disposed between the photocathode 8c and the output screen 7. The input screen 8 has a photocathode between the input phosphor layer 8b and the photocathode 8c.
In order to assist the uniform formation of 8c, a transparent conductive film such as I
TO and In ₂ O ₃ may be formed.

When the metal retaining ring 3a is pressed and joined to the input window 3, a large pressure is applied to the joined portion and the inner portion and the outer portion of the input window 6 are extruded, and particularly the portion extruded inward is the portion of the input window 3. The shape of the adjacent part is pushed up and deformed, but by deforming the buffer part 3b,
The effective field of view inside 3b can be less affected.

In use, the input window 3 is used as in the conventional case.
A radiation source is disposed so as to face the object, a subject is positioned between the input window 3 and the radiation source, radiation is irradiated from the radiation source, and the radiation is incident on the input window 3 through the subject.

The buffer portion 3b is also effective for a joining method involving deformation of the input window 3 other than the case where the metal holding ring 3a is pressure-welded.

Although aluminum is used as the material of the input window 3 because it is inexpensive and easy to process, it is not limited to aluminum, but is formed of a material having a high transparency to X-rays or gamma rays, such as beryllium or titanium. May be.

According to the above embodiment, the photocathode 8c is provided in close contact with the inner surface of the input window 3 forming a part of the vacuum envelope 5 to eliminate the conventional absorption and scattering of radiation by the input substrate. And improve the contrast,
By providing the cushioning portion 3b that rises inside the joint portion of the input window 3, only the cushioning portion 3b is deformed even when the joint portion of the input window 3 is pushed out toward the center by the pressure of the pressure contact, and within the effective visual field. The deformation of the shape can be suppressed. Therefore, by suppressing the deformation within the effective visual field, the photoelectrons emitted from the photocathode 8c that is in close contact with the inside of the input window 3 can be accurately formed on the output screen 7.

Next, another embodiment of the present invention will be described with reference to FIG.

In the X-ray image tube 1 shown in FIG. 2, when the input window 3 and the metal holding ring 3a are joined by pressure contact, the buffer portion 3b is lowered toward the output side. In this case, the same effect can be obtained. However, the metal retaining ring 3a must have the same shape as the input window 3 and be fitted exactly.

In addition to the above-mentioned embodiment, the buffer portion 3b may have one or several serpentine stepped portions so as to have a buffering action, and the material is selected so that it can be subjected to thermal deformation. You may.

[0031]

According to the X-ray image tube of the first aspect of the invention, the input window has the shock-absorbing portion of the shape that rises sharply at the portion connected to the base body. Even if the connected part is pushed toward the center of the input window, only the raised cushioning part will be deformed, and the deformation of the input window within the effective visual field inside the cushioning part can be suppressed, and an accurate image can be obtained. Can be obtained.

According to the X-ray image tube of claim 2,
Since the input window has a buffer portion having a shape that is sharply lowered at the portion connected to the base body, even if the connected portion of the input window is pushed out toward the center of the input window by the pressure of the pressure contact of the metal retaining ring, Only the lowered buffer part is deformed,
It is possible to suppress deformation of the input window within the effective visual field inside the buffer portion, and it is possible to obtain an accurate image.

[Brief description of drawings]

FIG. 1 is a sectional view showing an X-ray image tube according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an X-ray image tube of another embodiment of the same as above.

FIG. 3 is a sectional view showing an X-ray image tube of a conventional example.

FIG. 4 is an explanatory view showing a usage state of the X-ray image tube of the above.

FIG. 5 is an enlarged sectional view showing the periphery of the photocathode of the X-ray image tube.

FIG. 6 is a sectional view showing an X-ray image tube of another embodiment of the same as above.

[Explanation of symbols]

 1 X-ray image tube 3 Input window 3a Metal retaining ring 3b Buffer part 5 Vacuum envelope 8 Input screen as input surface 8b Input phosphor layer 8c Photoelectric surface to be the input surface

Claims (2)

[Claims] 1. An input window made of a radiation transmissive material bonded to a metal retaining ring to form a part of a vacuum envelope, and an input surface made of at least an input phosphor layer and a photocathode on an inner surface of the input window. In the X-ray image tube, the input window is provided with a buffer portion having a shape in which a portion adjacent to a portion joined to the metal retaining ring is sharply raised. Line image tube. 2. An input window made of a radiation transparent material is joined to a metal retaining ring to form a part of a vacuum envelope, and an input surface made of at least an input phosphor layer and a photocathode is formed on an inner surface of the input window. In the X-ray image tube, the input window is provided with a buffer portion having a shape in which a portion adjacent to a portion joined to the metal retaining ring is sharply lowered. X-ray image tube.