JP2000133491A - X-ray photo-timer detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray photo-timer detector having reduced thickness of ionization chamber, capable of providing stable X-ray photograph density without being affected by external atmospheric pressure or humidity. SOLUTION: Parallel electrodes 7 formed of an Al or carbon plate are formed on the upper and lower surfaces inside a frame 4 made of an insulation material such as an epoxy resin, and Xe gas is filled and enclosed under normal pressure. Al plates 5 are stuck to the upper and lower surfaces outside the frame 4, and are fixed for reinforcing it. Lead wires 6 are provided for applying a D.C. voltage to the electrodes 7 inside the frame 4 and extracting an ionization current to the outside by the use of X-ray energy, and the signal thereof is sent to an outside X-ray automatic exposure control device to provide stable X-ray photograph density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray phototimer detector, that is, a detector combined with an X-ray automatic exposure control device for automatically and optimally controlling the film density during X-ray photography.

[0002]

2. Description of the Related Art An automatic exposure control device in X-ray photography is used for most indirect photography, and is also widely used for direct photography of the chest, abdomen and the like. This automatic exposure control device operates so as to keep the film density constant by automatically controlling the photographing time. The automatic exposure control device converts the amount of X-ray transmitted through the subject into an electric signal, and this electric amount reaches a certain value. Then, X-rays are cut off to obtain a desired film density. FIG. 3 shows an X-ray imaging system using an X-ray automatic exposure control device.
After the tube voltage, tube current, and time, which are imaging conditions, are set, X-rays are radiated from the X-ray tube 8, narrowed to an effective field of view by the diaphragm 9, transmitted through the subject 11, and detected by the X-ray photo timer detector. The X-ray film in the cassette 12 is exposed while passing through the X-ray phototimer detector 10. X
The X-ray photo timer detector 10 converts the X-ray dose into a signal current 13 and inputs it to the X-ray automatic exposure controller 14. Signal current 1
Since 3 is proportional to the intensity of the X-rays incident on the X-ray phototimer detector 10, the exposure amount of the X-ray film is proportional to the value obtained by integrating the signal current 13. The signal current 13 is integrated by the integration circuit 15, and the integrated value is compared with the set value of the concentration setting circuit 16 by the comparator 17.
, An X-ray cutoff signal is generated and sent to the X-ray high voltage device 19 to stop the X-ray exposure. In FIG. 3, an X-ray photo timer detector 10 is provided on the front of a cassette 12 on which an X-ray film is mounted.
, But may be provided on the rear side. In this case, the X-ray phototimer detector 10 is placed in front of the cassette 12 in the automatic exposure control (phototimer control) for general photographing because the intensifying screen, absorption of the rear surface material of the cassette, and the like greatly affect the characteristics. As the X-ray phototimer detector 10 as a mechanism for detecting the X-rays transmitted through the subject, there are conventionally a fluorescent lighting type, an ionization chamber type, and a semiconductor type, but here, an ionization chamber type X-ray phototimer detector 10S Will be described with reference to FIG. This ionization chamber detection method uses X-ray ionization to detect X-rays.
An insulating plate 20 is provided inside the chamber including the AL plate 5 on the X-ray input side and the AL plate 5 on the X-ray input side.
An insulating plate 20 is provided inside the AL plate 5 on the line output side, electrodes 7 are provided on the surface thereof, and both electrodes 7 are opposed to each other in parallel. The inside is filled with air at 1 atm, and a DC voltage is applied between the electrodes 7. When X-rays enter this chamber, the gas atoms that have sufficiently absorbed the energy of the X-rays have their outermost electrons jumped out of the attractive sphere of the nuclei, and the atoms are positively charged. Then, the electrons and the positively charged atoms are respectively captured by the electrodes and taken out to the outside as a signal current 13. Conventionally, as means for detecting X-rays, air (atmosphere) has been detected by measuring electric charges ionized by the X-rays.

[0003]

The conventional X-ray phototimer detector 10S is constructed as described above. However, since air is used for detecting X-rays, the amount of charge ionized by X-rays is small. In order to increase the sensitivity, the air layer had to be thickened. If the thickness of the X-ray phototimer detector 10S becomes thicker, the distance between the subject 11 and the film becomes longer, and since the X-ray tube has a certain size, the geometric blur becomes larger, and the image quality deteriorates. At the same time, there is a problem that the photographed image is enlarged more than it actually is. In addition, since unsealed air is used, there is a problem in that it is easily affected by atmospheric pressure and humidity, and stable X-ray photographic density cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has a thin X-ray phototimer detector to obtain a stable X-ray photographic density which is not affected by external atmospheric pressure and humidity. It is an object to provide an X-ray phototimer detector.

[0005]

In order to achieve the above object, an X-ray phototimer detector according to the present invention makes an X-ray transmitted through a subject incident on an ionization chamber having an electrode to which a DC voltage is applied. In an X-ray phototimer detector for measuring electric charge ionized by a ray, a gas in which the amount of electric charge ionized by the X-ray is larger than air is sealed in the ionization chamber.

[0006] The X-ray phototimer detector of the present invention is configured as described above. Since the detector is filled with gas in which the amount of charge ionized by X-rays is larger than air, the thickness of the detector is reduced. Even if is thinner, it has the same detection sensitivity as air and is hermetically sealed, so that a stable X-ray photographic density can be obtained without being affected by external atmospheric pressure and humidity.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS X-ray Phototimer Detector 1 of the Present Invention
One embodiment of 0N will be described with reference to FIGS.
Fig. 1 shows the appearance. FIG. 2 shows a cross section thereof. The X-ray phototimer detector 10N according to the present invention includes a plate-shaped frame 4 made of an insulator having a size four times as large as the size of the field of view, and a conductive film having a very small X-ray absorption inside the X-ray incident direction. Electrodes 7 arranged vertically opposite each other, two conductive wires 6 capable of supplying a DC voltage to the electrodes 7 and extracting an ionization current, and are fixed to both surfaces of a frame 4 on the outer plate in the X-ray incident direction. An AL plate 5 serving both as a reinforcement and an X-ray filter, Xe gas sealed and sealed in the frame 4, a cable 2 for supplying a DC voltage to the electrode 7 and extracting an ionization current to the outside, And a connector 3 for connection to the automatic exposure control device 14.

The frame 4 is made of an insulating material, such as epoxy resin, and has a structure (not shown) which is divided into an upper part and a lower part in order to form electrodes 7 on the upper and lower surfaces. After the electrodes 7 are formed and the conducting wires 6 are connected, the upper and lower portions are provided with holes (not shown) through which Xe gas can be sealed from the outside, and are bonded. Then, the Xe gas is sealed at a normal pressure of about atmospheric pressure, and a cover (not shown) is placed on the sealing port. In this state, the frame 4 has an airtight structure, and there is no leakage of the Xe gas to the outside and no mixing of air. The electrode 7 is made of X such as thin aluminum or carbon.
It is made of a conductive material with good light transmission. As shown in FIG. 1, the shape of the electrode 7 is a lighting field 1 (an area for detecting X-rays).
Has the same shape as that of the above, and the charges ionized by the X-ray irradiation are collected. In the X-ray imaging system shown in FIG. 3, the structure of the subject 11 is complicated and varied, and the position and shape of the lighting field 1 (detection unit) according to the purpose of imaging determines the density of the X-ray photograph. To match the complexity of the structure of the subject 11, the X-ray photo timer 10N of the present invention is effective. That is, a multi-segment daylighting type X-ray phototimer detector 10 having a plurality of daylighting fields 1 in one frame 4.
And the X-ray automatic exposure controller 14 can be combined. Instead of air having low sensitivity, a gas having a larger amount of charge ionized by X-rays than air, such as Xe gas, Kr gas, or A gas, is used as the ionizing gas. Xe gas is more than 100 times more sensitive to X-rays than air, and the thickness of the conventional detector using air is about 10 mm, but the thickness of 3 mm or less is possible with the detector of the present invention. . The AL plate 5 on the surface of the frame 4 plays a role of a filter for removing soft X-rays and a role of reinforcing the frame 4. In the X-ray automatic exposure control using the X-ray photo timer detector 10N according to the present invention, the same control as described in the conventional apparatus of FIG. 3 is performed. As described above, since it is only necessary to seal the Xe gas in the frame 4 at a pressure of about the atmospheric pressure, it is not necessary to make the X-ray phototimer detector 10 a so-called pressure vessel structure, so that the structure can be simplified and the Xe gas can be reduced. X to use
The thickness of the line phototimer detector 10 can be reduced.

[0009]

The X-ray phototimer detector of the present invention is constructed as described above, and a gas in which the amount of charge ionized by X-rays is larger than air, for example, Xe gas is sealed in the detector. Therefore, even if the thickness of the detector is reduced, it has the same detection sensitivity as air and is further sealed,
A stable radiographic density can be obtained without affecting the external pressure and humidity.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an X-ray phototimer detector of the present invention.

FIG. 2 is a diagram showing a cross section of the X-ray phototimer detector of the present invention.

FIG. 3 is a diagram for explaining an X-ray imaging system that performs X-ray automatic exposure control using an X-ray phototimer detector.

FIG. 4 is a diagram showing a cross section of a conventional X-ray phototimer detector.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Daylighting field 2 ... Cable 3 ... Connector 4 ... Frame 5 ... AL plate 6 ... Conductor wire 7 ... Electrode 8 ... X-ray tube 9 ... Aperture 10, 10S, 1
0N X-ray photo timer detector 11 Subject 12 Cassette 13 Signal current 14 X-ray automatic exposure control device 15 Integrating circuit 16 Density setting circuit 17 Comparator 18 X-ray cutoff signal generator 19 X-ray High voltage device 20 ... Insulating plate

Continued on the front page F term (reference) 4C092 AA01 AB03 CC02 CD06 CE14 CF22 CJ11 DD04 4C093 AA03 CA10 CA35 CA41 EA12 EB04 EB15 FA18 FA19 FA45 FC04

Claims (1)

[Claims] 1. An X-ray phototimer detector for transmitting an X-ray transmitted through a subject to an ionization chamber having an electrode to which a DC voltage is applied, and measuring an electric charge ionized by the X-ray. An X-ray phototimer detector characterized in that a gas having a larger amount of charge than the air is charged.