JPH0458600B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a radiographic imaging apparatus.

[Conventional technology]

FIG. 3 is a cross-sectional view showing the arrangement when radiographically photographing a subject using a conventional radiographic apparatus. The cassette is tightly sealed, 5 is the object, and 6 is the radiation that passes through the object.

When photographing a subject using radiation such as X-rays, the sensitivity of industrial X-ray film to X-rays is extremely low, and most of the X-rays pass through the film without affecting its sensitivity. Intensifying screens 3 and 4 made of metal or phosphor are brought into close contact with the front and back of the film 2, and the film 2 absorbs the secondary electrons or fluorescence generated by the interaction between the X-rays 6 and the front intensifying screen 3. In this way, the photosensitivity of the film 2 is improved.

On the other hand, the front intensifying screen 3 and the rear intensifying screen 4 which are in close contact with the film 2 play a major role in blocking scattered radiation and improving photographic image quality. For this reason, it is necessary to combine intensifying screens 3 and 4 with thicknesses corresponding to the energy of the X-rays before and after the film 2. The energy of X-rays required to pass through the object 5 increases as the thickness of the object 5 increases.
When the plate thickness increases from 10mm to 200mm, the required
The energy of the line increases from 100Kev to 8MeV, and as the energy increases, the thickness of the intensifying screen also needs to increase from 0.03mm to 1.0mm using lead foil. Therefore, the cassette enclosing the film 2 and the intensifying screens 3 and 4 also becomes thicker and heavier. As a result, the workability during transmission imaging of subject 1 deteriorates, and the weight of the cassette per film is too heavy, especially in order to automate the X-ray transmission test of large, thick-walled pressure vessels and perform continuous imaging. , which poses a problem when transporting the film. Furthermore, if the intensifying screens 3 and 4 become thicker, not only will the price of the intensifying screen become higher, but also the intensifying screens 3 and 4 enclosed in the cassette 1 and the film 2 will tend to become misaligned.
There may also be problems such as scratches. In order to solve this problem, if a white film 2 is inserted between the intensifying screens 3 and 4 and the film 2, this may cause the image to become blurred. Furthermore, since intensifying screens with different thicknesses are used depending on the energy of the X-rays, there are problems such as mistakes being easily made when repacking the film.

[Purpose of the invention]

The object of the present invention is to provide a radiographic imaging apparatus that solves the above-mentioned problems.

[Summary of the invention]

The radiographic imaging apparatus of the present invention includes a cassette containing an X-ray film and an intensifying screen that sandwiches the film;
It consists of a shielding plate that removes scattered radiation incident on a film provided outside the cassette, and the shielding plates are provided parallel to each other in front and behind the cassette in the direction of X-ray transmission.

The reason why we have separated the components of the radiographic imaging device by function is that the thickness of the shielding plate required to remove scattered radiation varies depending on the energy of the X-rays transmitted through the subject, but The range of the secondary electrons involved in the sensitizing effect is extremely short, and therefore the intensifying screen that contributes to the sensitizing effect is considered to be an extremely thin layer of constant thickness near the film emulsion surface. Therefore, the thickness of the cassette is made equal by enclosing a film and a thin intensifying screen necessary for the sensitizing action of the film in the cassette, and a shielding plate necessary for removing scattered radiation is placed outside the cassette. It was established.

〔Example〕

This invention will be explained based on examples.

FIG. 1 is a sectional view showing the arrangement when performing radiographic imaging of a subject using a radiographic imaging apparatus according to an embodiment of the present invention. In the figure, 1 is a cassette in which a front intensifying screen 7 and a rear intensifying screen 8 made of lead foil of a predetermined thickness are tightly enclosed in a film 2, and 9 is provided in front of the cassette 1 in parallel with the cassette 1 to carry a subject, etc. A front shielding plate 10 is provided behind the cassette 1 in parallel with the cassette 1, and is a rear shielding plate for shielding scattered rays behind the cassette, that is, scattered rays coming from the walls, floor, etc. of the room. With the front intensifying screen 7 and rear intensifying screen 8 provided inside the cassette 1, and the front shielding plate 9 and rear shielding plate 10 provided outside the cassette, a radiographic imaging apparatus according to an embodiment of the present invention is constructed. Configure. 5 is a subject, and 6 is an X-ray that passes through the subject.

Figure 2 shows the film density D when X-ray radiography of a subject is performed using the radiographic imaging apparatus of this embodiment and the film density D when X-ray radiographic imaging of a subject is performed using a conventional radiographic imaging apparatus. A characteristic diagram of film density D is shown.

The film density D shown in the figure is obtained using an 8 MeV liner that linearly accelerates electrons as an X-ray source, with a distance between the source and the cassette of 2000 mm, a sensitivity of the film used of 100, and an exposure amount of 275. with thickness 150
This is an X-ray transmission photograph of a mm-sized subject. In the figure, No. 1 shows the case where a conventional radiographic imaging apparatus without a shielding plate provided outside the cassette is used. Sensitizing lines are sensitive when the X-ray energy is 8 MeV
A lead foil intensifying screen with a front intensifying screen of 0.5 mm and a rear intensifying screen of 1.0 mm, which are normally used when using a 100 mm film, was used. No. 2 to No. 6 show cases in which the radiographic imaging apparatus of this embodiment is used. The front intensifying screens 7 enclosed in the cassette 1 are No. 2 to No. 6.
Both cases use a lead foil intensifying screen with a thickness of 0.03 mm, and the rear intensifying screen 8 shows a case where a lead foil intensifying screen with a thickness of 0.03 mm to 0.5 mm is used. In addition, the △ mark in the figure indicates that the front shielding plate 9 is 0.5mm.
When the rear shielding plate 10 uses a 1.0mm lead plate,
The mark indicates that the front shielding plate 9 uses a 0.5 mm lead plate and the rear shielding plate is not used. As is clear from the figure, the film density D when using the radiographic apparatus of this embodiment is comparable to that obtained when using the conventional radiographic apparatus.

Also, as is clear from this figure, the film density is higher when the shielding plate is placed both in the front and the rear than when it is placed only in the front.

Also, as is clear from the comparison between the △ mark in No. 2 and the * mark in No. 5 or No. 6, it is better to place shielding plates at the front and rear than when placing shielding plates only at the front. , the total weight of the intensifying screen (the total thickness of the front and rear intensifying screens) for obtaining the required film density can be reduced.

These causes, as mentioned earlier, are due to the presence of the rear shielding plate, which causes the scattering of radiation behind the cassette, i.e. the walls of the room,
It is presumed that this is because by blocking the scattered radiation coming from the floor etc., it is possible to prevent an adverse effect on the film.

Furthermore, the weight of the cassette containing the film and intensifying screen is approximately 1000 gr when the thickness of the front intensifying screen is 0.5 mm and the thickness of the rear intensifying screen is 1.0 mm, whereas the weight of the front intensifying screen and the rear intensifying screen is approximately 1000 gr. If the thickness of the intensifying screen is 0.03 mm, it will be about 200 gr.

Therefore, if a film with a sensitivity of 100 is used, the thickness shown in Figure 2 No. 2 will be the intensifying screen in the cassette.
Using a 0.03 mm front intensifying screen 7 and rear intensifying screen 8 reduces the weight of the cassette by about 1/5 while maintaining the film density D, or image quality, at the same level as when using a conventional radiographic imaging device. It can be done.

〔Effect of the invention〕

As explained above, the separable intensifying screen of the present invention separates the intensifying screens according to their functions, thereby reducing the weight of the cassette, improving workability, and being advantageous for film transport when automating radiographic imaging. becomes. In addition, if the sensitivity of the film is constant, the intensifying screen enclosed in the cassette only needs to be of one thickness, which eliminates mistakes when refilling the film and simplifies the refilling process. This reduces scratches and dirt on the intensifying screen and film, and also contributes to cost reduction.

[Brief explanation of the drawing]

Figure 1 is a layout diagram for performing radiographic imaging using an embodiment of the present invention, Figure 2 is a characteristic diagram of film density, and Figure 3 is a diagram for performing radiographic imaging using a conventional intensifying screen. It is a layout diagram when carrying out. 1...Cassette, 2...Film, 3,7...
Front intensifying screen, 4, 8... Rear intensifying screen, 5... Subject, 6... X-ray, 9... Front shielding plate, 10... Rear shielding plate.

Claims (1)

[Claims] 1 Consists of a cassette containing an X-ray film and an intensifying screen sandwiching the film, and a shielding plate provided outside the cassette for removing scattered rays incident on the film, with the shielding plate facing in the direction of X-ray transmission. A radiographic imaging apparatus characterized in that the cassettes are provided in parallel before and after the cassette is sandwiched between the cassettes.