WO1994022161A1

WO1994022161A1 - X-ray image intensifier

Info

Publication number: WO1994022161A1
Application number: PCT/JP1994/000430
Authority: WO
Inventors: Shirofumi Yamagishi
Original assignee: Kabushiki Kaisha Toshiba
Priority date: 1993-03-17
Filing date: 1994-03-17
Publication date: 1994-09-29
Also published as: DE69418406D1; EP0644572B1; DE69418406T2; CN1059514C; EP0644572A4; CN1105803A; EP0644572A1

Abstract

This invention discloses an X-ray image intensifier including a vacuum container having a metallic X-ray input window (11a), and an input plane formed on the inner surface of the X-ray input window. In the container, convergence electrodes, an anode and an output plane are sequentially disposed along the path of electrons emitted from the input plane. The X-ray input window has a hardened undulating layer (11d) on the surface thereof on the input side and the input plane has a phosphor layer (12b) formed on the hardened undulating layer, and a photoelectric surface (12d) formed on the phosphor layer.

Description

Description Title of Invention

X-ray imaging technology

The present invention relates to an X-ray image intensifier.

Background art

In recent years, X-ray image intensifiers have been developed using low-energy X-rays with an X-ray tube voltage of 30 KV (tube current 1 mA) or less and high-energy X-rays with an X-ray tube voltage of 30 V or more (tube current 1 mA). The obtained X-ray images are converted into visible light images and are widely used for medical diagnosis and nondestructive inspection.

As shown in FIGS. 1 and 2, such a conventional X-ray image intensifier includes a vacuum envelope (hereinafter referred to as an envelope) 11 in order from the X-ray source A side. It has a basic configuration in which an input surface 12, a focusing electrode 13, an anode 14 and an output surface 15 are arranged. The envelope 11 is a metal input window 11a into which X-rays enter, a glass body 11b supporting the focusing electrode, and an output surface 15 or an optical device supporting the output surface 15. It consists of a glass output section 11c.

An input surface 12 arranged at a predetermined distance from the input window 11a functions as a cathode, and an input substrate formed into a curved shape so as to project toward the X-ray source A side, for example, aluminum. Metal substrate 1 2a A phosphor layer 12b for converting X-rays into visible light, formed on the concave side of the metal substrate 12a, and a transparent conductive film 12 formed on the phosphor layer 12b. A photocathode 1 formed on the transparent conductive film 12 c and converting visible light emitted from the phosphor layer 12 b into electrons.

2d. Here, the transparent conductive film 12 c is usually made of indium oxide, IT 0 (a compound of indium oxide and tin oxide), and the like. It is used for preventing reaction between sodium iodide-activated cesium iodide and the material constituting the photocathode 12d, and for obtaining continuous conductivity on the surface of the phosphor layer.

On the other hand, on the side where the output surface (in this case, the structure in which the optical glass substrate supporting the output phosphor also serves as a part of the envelope) 15 facing the input surface 12 is provided, An anode 14 supported on the enclosure output section 1 1c side is arranged, and between the anode 14 and the input surface 12 serving as a cathode, for example, on the inner wall of the enclosure body 11b. A first focusing electrode 13 a is disposed along the first focusing electrode 13 a, and a cylindrical second focusing electrode 13 b is disposed between the first focusing electrode 13 a and the output surface 15. The first and second focusing electrodes 13a and 13b constitute an electrostatic electron lens system.

In the X-ray image modifier configured as described above, the X-rays B emitted from the X-ray source A pass through the subject C to reach the input window 11a, and the input window 11a The X-ray image projected on is converted into an electronic image on the human surface described later. This electron image is applied, for example, between the input surface 12 serving as a cathode and the anode 14.

The first jelly-bundle electrode 13 a with a partial voltage applied from the It is accelerated and focused by the electrostatic lens system formed by the second focusing electrode 13 b, and is converted again into visible light at the output surface 15. In this case, a visible image that is enhanced by, for example, 1 × 100 or more compared to the intensity of visible light on the input surface 12 is obtained.

As shown in the enlarged view of FIG. 2, the input surface of the conventional X-ray image enhancement wire as described above has a predetermined distance between the input window 11a and the input surface 12 of the envelope. Due to the separation, the scattering of X-rays increases, resulting in a decrease in contrast. Hereinafter, this problem will be described with reference to FIG. 3 using an example of an X-ray image intensifier having an effective diameter of the input surface of 4 inches.

The tube voltage of the X-ray tube used to obtain the data in Fig. 3 was 50 KV, the tube current was 1 mA, and the vertical axis was the contrast (%) of the X-ray image intensifier. In addition, the contrast ratio and Yokoyuki Yoko show the diameter (ram) of the lead disk. Here, the contrast (%) refers to the case where a predetermined amount of lead is placed at the center of the input effective visual field with respect to the luminance of the input effective visual field of the X-ray image intensity. This is the value that displays the luminance of the input effective visual field in percentage. The contrast ratio is a ratio calculated quantitatively from the contrast (%).

Curve c in FIG. 3 shows the characteristics of the conventional X-ray imaging stiffener shown in FIG. 2. According to this, the diameter (mm) of the lead disk at the time of contrast measurement is shown. ) Becomes smaller at the boundary of 40 mm, the contrast decreases significantly. This means that the contrast of a smaller subject is larger than that of a larger subject. This means that it is significantly inferior to that of industrial equipment, and has the drawback that it is difficult to judge defects at small parts in industrial use.

Fig. 4 shows the experimental data of contrast when the same X-ray image intensifier was used and only the tube voltage of the X-ray tube was changed to 3 ° KV. According to the straight line e in FIG. 4, as in the case of the straight line c in FIG. 3, the contrast becomes smaller as the diameter (mm) of the lead disk at the time of contrast measurement becomes smaller at the boundary of 4 ° mm. Although it decreases significantly, the degree of the decrease is steeper than in the case of Fig. 3.

On the other hand, Japanese Patent Publication No. 34-2032 / 32 discloses an X-ray image intensifier which forms an input surface directly on the inner surface of an aluminum input window. I have. Such a structure in which the input surface is formed directly on the inner surface of the input window and which uses aluminum as the input window has not yet been put to practical use. When an X-ray imaging tensioner with an input window made of such a thin material is assembled and evacuated, the input window is deformed due to the pressure difference between the inside and outside of the pipe, and the input surface is naturally deformed. However, the desired photocathode cannot be obtained, and thus the output image may be distorted. Disclosure of the invention

SUMMARY OF THE INVENTION An object of the present invention is to provide an X-ray imaging intensity fire that eliminates the above-mentioned disadvantages, maintains high luminance, and provides a high contrast.

According to the present invention, there is provided a vacuum envelope having a metal X-ray input window, an input surface formed on an inner surface of the X-ray input window, and the vacuum envelope. A focusing electrode, an anode, and an output surface which are sequentially arranged along the direction of travel of electrons emitted from the input surface, and the X-ray input window has an uneven surface on the surface on which the input surface is formed. A hardened layer, the input surface comprising: a phosphor layer formed on the uneven surface hardened layer; and a photocathode formed on the phosphor layer. Is provided.

In the X-ray image of the present invention, the material of the X-ray input window made of metal is aluminum, aluminum alloy, or the like, which has a high X-ray transmittance and is difficult to process. In addition, a material having a strength capable of withstanding a pressure difference between the inside and the outside of the X-ray image intensifier by being surface-hardened by the surface hardening treatment can be used.

The uneven surface hardened layer of the metallic X-ray input window can be formed by, for example, performing an uneven surface hardening treatment on a metal plate constituting the metallic X-ray input window. The method for forming the uneven surface hardened layer can be performed, for example, as follows.

That is, a metal plate is struck using a hard sphere having a particle size of 50 to 200 m, for example, a glass bead, at a pressure of 1 to 4 kg / cm ² and a heating time of 1 to 5 minutes. Thus, a surface hardening treatment is performed. As a result, the surface of the metal plate becomes uneven, and an uneven surface hardened layer is formed.

The X-ray image intensifier of the present invention is particularly effective when using low-energy X-rays having an X-ray tube voltage of 30 KV (tube current of 1 mA) or less. BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a schematic diagram for explaining a conventional X-ray image intensity and X-ray imaging method.

FIG. 2 is a cross-sectional view showing a part of the conventional X-ray image finder shown in FIG.

FIG. 3 shows an embodiment of the X-ray image intensity according to the present invention and a conventional X-ray image—the contrast characteristics of the X-ray intensity is shown by the high energy X-ray. FIG. 4 is a graph showing data obtained using a line.

FIG. 4 shows an embodiment of the X-ray image clarifying fire according to the present invention and a contrast characteristic of the conventional X-ray mag- netic fire fin with the low energy X-ray. FIG. 4 is a graph showing data obtained using a line.

FIG. 5 is an enlarged cross-sectional view showing a main part of one embodiment of the X-ray imaging fire according to the present invention.

FIG. 6 is an enlarged sectional view showing a part of FIG.

FIG. 7 is a graph showing the relationship between the surface roughness of the surface-hardened A1 plate and the hardness of the surface-hardened layer. BEST MODE FOR CARRYING OUT THE INVENTION The X-ray imaging fire of the present invention has an input surface directly formed on the inner surface of the input window, and an uneven surface hardening treatment on the inner surface of the input window. It has the same configuration as the conventional X-ray image intensifier shown in Fig. 1 except that it is applied. γ

That is, as shown in Fig. 1, the basic configuration is such that the input surface 12, the focusing electrode 13, the anode〗 4, and the output surface 15 are arranged in the vacuum envelope 11 in order from the X-ray source Α side. The envelope 11 serves as the metal input window 11 a into which the X-rays are incident, the glass body 11 b supporting the focusing electrode, and the output surface 15 or supports the output surface 15. And a glass output section 1 1 c.

As shown in FIG. 5, an uneven surface hardened layer 11d having an uneven surface is formed on the inner surface of the input window 11a by the uneven surface hardening treatment. The material of the input window 11a used here is an aluminum alloy, and in particular, an ATM-500 series A1-Mg alloy is used. The input window 11a was obtained by forming such an aluminum alloy plate into a dish shape by pressing, and performing the above-described uneven surface hardening treatment.

The input surface 12 is formed directly on the uneven surface of the uneven surface hardened layer 11 d. The input surface 12 is composed of a light-reflective material layer 12 a formed on the uneven surface of the uneven surface hardened layer 11 d and a phosphor layer 12 b that converts X-rays formed thereon into visible light. And a transparent conductive film 12 c formed on the phosphor layer 12 b and visible light emitted from the phosphor layer 12 b formed on the transparent conductive film 12 c into electrons. It is composed of a photoelectric surface 12 d for conversion. Here, the transparent conductive film 12 c is usually made of indium oxide, ITO (a compound of indium oxide and tin oxide), etc., and alkali halide such as sodium iodide forming the phosphor layer 12 b is used. To prevent reaction between the activated cesium iodide and the material constituting the photocathode 12d, and to obtain continuous conductivity on the surface of the phosphor layer Used for

On the other hand, on the side on which the output surface (here, the structure in which the optical glass substrate supporting the optical member also functions as a part of the envelope) 15 is disposed in opposition to the input surface 12, An anode 14 supported on the envelope output section 1 1c side is arranged, and between the anode 14 and the input surface 12 serving as a cathode, for example, the inner wall of the envelope body 1 1b A first focusing electrode 13a is provided along the line, and a cylindrical second focusing electrode 13b is provided between the focusing electrode 13a and the output surface 15. The fact that the first and second focusing electrodes 13a, 13b constitute an electrostatic electron lens system is based on the conventional X-ray imaging enhancement shown in FIG. The structure is the same as that of a.

As described above, in the X-ray imaging intensifier of the present invention, an uneven surface hardened layer 11 d is formed on the inner surface of the input window 11 a, and the input surface 12 is directly formed thereon. Is formed. The Vickers hardness of the uneven surface hardened layer 11d is preferably 120 to 250, as described above. If the Vickers hardness is less than 120, it is insufficient to withstand the pressure difference between the inside and the outside of the X-ray image intensifier, and the X-ray input window 11a may be deformed. . On the other hand, if the Vickers hardness exceeds 250, the formability is reduced, which is not preferable.

The surface roughness of the uneven surface hardened layer 11 d is preferably 2 to 1 ° m. When the roughness is less than 2 / m, the hardness of the uneven surface hardened layer 11d is low, and is not enough to withstand the pressure difference between the inside and outside of the X-ray image. X-ray input window 1 1a may be deformed. On the other hand, when it exceeds 10 πι, ^

The adhesion of the phosphor formed on the substrate is weak, and the film quality of the phosphor is difficult.

The present inventors conducted an experiment to determine the relationship between the surface roughness of A 1 by the surface hardening treatment, the hardness of the treated surface, the adhesion of the phosphor on the treated surface, and the film quality of the phosphor as follows. Done.

That is, after forming the above-mentioned A 1 -Mg alloy plate having a thickness of 0.5 mm into the shape of an input window, an uneven surface hardening treatment was performed using a glass bead with a particle size of 10 ° m. By changing the pressure, the processing time, and the like, we obtained A1 alloy input window samples with various roughnesses.

The Vickers hardness of the treated surface of these A1 input window samples was measured, and the results shown in FIG. 7 were obtained. From the graph in Fig. 7, it is necessary to have a roughness of 2 m or more to obtain a Vickers hardness of 120 or more that can withstand the pressure difference between the inside and outside of the X-ray image intensifier. I understand.

Next, a phosphor layer was formed by vapor deposition on the treated surface of the A1 alloy input window sample, and the adhesion and the film quality of the phosphor layer were examined. The results are shown in Table 1 below.

table 1

Surface roughness 2 <x <5 x = 5 5 <x <10 10 <x

(m)

Hardness X 〇

X △ ◎ ◎

Phosphor 2

Adhesion 〇〇 ◎ 〇 △ Phosphor

◎ ◎ ◎ Δ χ

◎ Tori

〇 good

Δ Somewhat good

X bad

From Table 1 above, the surface roughness should preferably be 5 or more to obtain sufficient hardness of the A1 alloy input window plate, and the surface roughness should be 1 to obtain sufficient adhesion of the phosphor. 0 m or less is preferred It is understood that the surface roughness is preferably 10 m or less in order to obtain sufficient phosphor film quality. Considering these factors comprehensively, it is understood that the surface roughness is preferably 2 to 10 m.

As described above, focusing only on the adhesion and the film quality of the phosphor, the force <5 and the hardness when the surface roughness is 5 m are not the best. However, even if the surface roughness is 5 im, the best hardness can be obtained depending on the method of the uneven surface hardening treatment.

That is, first, to obtain the best hardness, After shaping a metal plate (ASTM500 series) into the shape of the input window, it is subjected to uneven surface treatment with high pressure, and uneven surface hardening treatment to obtain a surface roughness of 10111 or more. Next, the A 1 plate is subjected to a concave / convex surface hardening treatment at a low pressure, and the previously formed irregularities are crushed, and the surface roughness may be reduced to about 5 m. As a result, even if the surface roughness is 5 m, it is possible to obtain a surface having a picker hardness of about 250.

As described above, according to the X-ray image intensifier of the present invention, since the uneven surface hardened layer is formed on the inner surface of the X-ray input window, the X-ray image generated by evacuation is obtained. The deformation of the X-ray input window due to the pressure difference between the inside and outside of the modifier is small, and the light emitted from the input surface is directed toward the photocathode due to the presence of the light reflective material layer formed on the uneven surface hardened layer. Produces high contrast output images.

Also, when A1 or A1 alloy is used as the material of the X-ray input window, an X-ray image intensifier that has good moldability of the X-ray input window and is advantageous in terms of price is also available. can get.

Further, when the low-energy X-ray is used as the X-ray source when using the X-ray image intensifier of the present invention, a higher contrast can be obtained for a small-sized object. It is possible to obtain an output image of the mouse.

Hereinafter, examples of the present invention will be described.

(Example 1)

The X-ray image intensifier of the present embodiment is characterized in that an input surface having a specific structure is formed. That is, The thickness of the X-ray input window 11a is made of aluminum alloy (or aluminum) with a thickness of .5 mm. Processing has been applied. By this concave / convex surface hardening treatment, a rough surface having a height of about several micron is formed and the surface is hardened. That is, the concave surface of the X-ray input window 11a thus processed is formed with a concave-convex surface hardened layer 11d.

On the uneven surface of the uneven surface hardened layer 11d, an aluminum thin film 12a of about 2000 A, which is a light reflective material layer, is formed. This aluminum thin film is vacuum-deposited under a reduced pressure of about 2 xl O- ⁵ Pa. A phosphor layer 12b having a thickness of about 400 m is formed on the light reflecting material layer 12a by vapor deposition. At a substrate temperature of about 180 ° C., the first layer of CsIZNa phosphor has a thickness of about 380 m under a pressure of 4.5 × ^10_1Pa. Then, a second layer of CsIZNa phosphor is formed by vapor deposition under a pressure of 10 Pa or less to a thickness of about 20 μm.

The X-ray input window 11a including the phosphor layer 12b is welded to the envelope body 11c via a metal ring 11e. The envelope body 11 joined to the X-ray input window 11a in this way is also joined to the envelope output section 11c ₍ then, on the phosphor layer 12b, The photocathode 12d is formed via the transparent conductive film 12c or directly.

In the X-ray image intensity configured as described above, the X-ray B from the X-ray source A passes through the subject C and the input window As shown in Fig. 6, when the light enters the light emitting layer 11a, light is emitted at the point a, for example, in the phosphor layer 12b. This light is directed toward the output surface b and toward the input window 11a. c. Of the light, the light c traveling toward the input window side is irregularly reflected there when reaching the surface hardened uneven surface 12f which is the surface of the input window 11a, and the irregularly reflected light d usually causes a decrease in luminance. However, an aluminum thin film 12a as a light-reflective material layer is formed on the uneven surface hardened layer 11d, so that the light c reaches the uneven surface hardened layer 11d. Instead, the light is reflected by the aluminum thin film 12a, and the reflected light d is directed to the output surface 15 side, so that a decrease in luminance is prevented.

In the following, taking the case where the effective diameter of the input surface is 4 inches as an example, using the X-ray image intensifier of this embodiment and the X-ray image intensifier of the conventional structure, the contrast is obtained. The comparison data of the load characteristics will be described with reference to FIG.

In Fig. 3, as mentioned above, the vertical axis shows the contrast (%) and contrast ratio, and the horizontal axis shows the diameter of the lead disk. In the figure, an experiment was performed using an X-ray imager with an effective input diameter of 4 inches, and a tube voltage of 50 KV and a tube current of 1 mA. The straight lines a and b in Fig. 3 show examples using the input window of the structure of the present embodiment. Among them, the straight line a uses an aluminum input window, and the straight line b The cases where an input window made of lithium is used are shown. As described above, the curve c shows an example of the conventional structure of the X-ray image intensifier shown in FIG. According to the results shown in Fig. 3, the contrast of the conventional structure of the X-ray image intensifier is reduced by the diameter of the bell disk (mm) and the diameter is reduced to 4 mm. While the contrast is remarkably reduced, the contrast of the X-ray imaging intensifier of the present embodiment is as shown by the straight lines a and b. It can be seen that it increases in proportion to the diameter of the disk (mm), is linearly proportional to the diameter of the lead disk, and depends on the diameter of the lead disk. This means that it is easy to make a determination in the case where the subject is a finer object, in the case where an attempt is made to make a difference in the shading by coloring.

As described above, the X-ray image intensifier of the present embodiment enables the practical use of an X-ray image intensifier having an input window and input surface structure, which has been considered difficult in the past. It is the one that was decided.

Example 2

This embodiment uses the same X-ray image intensifier (the material of the input window is A1-Mg alloy) as in the first embodiment, and contrasts when low energy X-rays are used. It shows an example of measuring the characteristics. Fig. 4 is a graph showing the contrast (%) and contrast ratio on the vertical axis and the diameter of the lead disk on the horizontal axis, as described above. The experiment was performed with an X-ray tube voltage of 30 KV and a tube current of ltnA.

The straight line d in FIG. 4 is an example using the input window of the structure of the present embodiment, and the curve e is the control when the conventional structure of the X-ray image intensifier shown in FIG. 1 is used. Indicates changes in the trajectory.

According to Fig. 4, the contrast of the conventional X-ray image-given intensifier is high when high energy X-rays are used. PP

1 5

In contrast to (X-ray tube voltage 50 KV, tube current 1 mA), the diameter of the lead disk ( _mm ) becomes significantly smaller as the diameter becomes smaller at the boundary of 40 mm. The X-ray image of the example — the contrast of the digi- intensifier is linearly proportional to the diameter of the lead disk and depends on the diameter of the lead disk, as shown by line d. Similar to the above, it is necessary to be able to make more accurate judgments in judging finer objects.

As described above, according to the present invention, the practical use of an X-ray image intensifier having a structure in which an input surface is formed directly on the inner surface of an input window, which has been considered difficult, has been achieved. X-ray image intensifier with improved efficiency

"* Mel ₀

The same effect can be obtained by using a 1-8-51 series alloy (ASTM 600 series) in addition to the A1 Mg alloy used in the above embodiment as the input window material. Can be

Claims

The scope of the claims

1. A vacuum envelope having a metal X-ray input window, an input surface formed on the inner surface of the X-ray input window, and a traveling direction of electrons emitted from the input surface in the vacuum envelope. The X-ray input window has an uneven surface hardened layer on the surface on which the input surface is formed, and the input surface includes the uneven surface. An X-ray image intensifier comprising a phosphor layer formed on a surface hardened layer and a photocathode formed on the phosphor layer.

2. The X-ray imaging intensifier according to claim 1, wherein the material of the metal X-ray input window is aluminum or aluminum alloy.

3. The X-ray image intensifier according to claim 1, wherein the surface roughness of the uneven surface hardened layer is 2 to 10 m.

4. The X-ray image sifter according to claim 1, wherein the Vickers hardness of the uneven surface hardened layer is from 120 to 250.

5. The X-ray image intensifier according to claim 1, wherein the uneven surface hardened layer is obtained by shaping the input window material into the shape of the input window and then projecting a hard sphere against the surface of the input window material. Fire.

6. The X-ray image intensifier according to claim 1, wherein the input surface further comprises a light reflective material layer formed on the uneven surface hardened layer.

7. The X-ray image intensifier according to claim 6, wherein the light-reflective material layer is a metal thin film.