JPH08213189A - X-ray photographing device - Google Patents

Abstract

PURPOSE: To always photograph the image of an object to optimum density, regardless of the status thereof. CONSTITUTION: An output signal from PMT (photo-multiplier) 22 is transmitted to a PMT control device 24 via an A/D converter 23. Then, feed voltage for PMT 22 is controlled, depending on the output ratio thereof under an X-ray condition after automatic brightness adjustment at the time of examining a uniform object and an actual objects by fluoroscopy, thereby determining the sensitivity of PMT 22 for photographing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray imaging apparatus using an X-ray image intensifier and an X-ray TV camera for medical diagnosis and the like.

[0002]

2. Description of the Related Art Conventionally, X-ray has been used to direct X
The X-rays are irradiated, the X-rays transmitted through the subject are made incident on the X-ray image intensifier, and an X-ray TV camera is coupled to the X-ray image intensifier to obtain a video signal of an X-ray transmission image. It has been performed to display it as a fluoroscopic image on a TV monitor device or the like to be useful for medical diagnosis. During such X-ray fluoroscopy, the IBS signal (automatic brightness adjustment signal) obtained from the X-ray TV system is sent to the X-ray controller, and the X-ray conditions such as the X-ray tube voltage are adjusted based on the IBS signal. The brightness of the fluoroscopic image displayed on the TV monitor is controlled so that it is always kept constant.
This IBS signal is usually a signal obtained by comparing the average value and the peak value of the luminance of the video signal in a certain area of the image and using the larger signal, and this IBS signal is set to a predetermined constant value. The X-ray condition is controlled by the X-ray controller so that the value becomes a value.

In this X-ray photographing apparatus, film (direct and indirect) photographing or digital photographing (video signal A
In the case of performing (D / D conversion and imaging in a method of storing in the image memory), mAs (the product of the tube current mA and the exposure time s) is set in advance, and the value obtained by time integration of the X-ray intensity detection signal is X-rays are blocked when the set mAs value is reached. This controls the density of the captured image. Specifically, a photodetector such as a PMT (photomultiplier) inserted in an optical system between the X-ray image intensifier and the X-ray TV camera is used, whereby the output of the X-ray image intensifier is used. Converts light into electric current. Since this current value corresponds to the X-ray intensity, this current is integrated by the X-ray controller, and the integrated value is set in advance.
X-rays are blocked when the As value is reached.

X during film or digital photography
The line intensity detection sensitivity is adjusted so that mAs has a constant value when a uniform subject serving as a reference is photographed. This serves as a reference value for the X-ray intensity detection sensitivity. For example, when a contrast examination is performed on the stomach, when the stomach is filled with the contrast agent, the contrast agent is applied to the daylighting field for light detection by the PMT. Since it will be covered, the X-ray intensity detection signal becomes small. Therefore, in such a case, when an image is taken with the X-ray intensity detection sensitivity as a reference value as described above, the contrast agent portion has an appropriate concentration, but the other portions have a large X-ray intensity time integration value. As a result, it is impossible to take a good quality image.

Therefore, conventionally, the operator manually sets the set value of the time integrated value of the X-ray intensity detection signal (that is, the set mAs value) based on the experience according to the state of the part to be actually imaged. I have to. That is, for example, when capturing a contrast agent-filled image of the stomach as described above, the optimum one obtained from experience is
Increase the set value of mAs.

[0006]

However, if the parameters for photographing are manually set based on the experience of the operator in this way, only a person with a certain amount of experience can do it, and a person with abundant experience is required. There is a problem that the operation is very complicated and the operation error is likely to occur.

In view of the above, the present invention automatically selects the optimum X
The line intensity detection sensitivity is set so that no matter how the condition of the subject (region, contrast agent filling level, etc.) changes,
An object of the present invention is to provide an X-ray imaging apparatus improved so that an image having an optimum density can always be taken.

[0008]

In order to achieve the above object, in the X-ray photographing apparatus according to the present invention, X-ray generating means for irradiating the subject with X-rays and X-rays transmitted through the subject are incident. X to obtain an X-ray transmission image signal
The X-ray condition is input so that the X-ray intensity detecting unit that detects the intensity of the X-ray transmitted through the subject and the signal corresponding to the brightness of the video signal are input and the brightness becomes a predetermined value. And an X-ray intensity detection unit output when the fluoroscopic brightness of an actual subject becomes a predetermined value by the automatic brightness adjustment unit,
Sensitivity control for automatically adjusting the sensitivity of the X-ray intensity detecting means to a sensitivity according to the ratio with the output of the X-ray intensity detecting means when the luminance of the uniform subject in the fluoroscopic state becomes a predetermined value by the automatic brightness adjusting means. And means for shutting off the X-ray for photographing when the integrated value of the X-ray intensity detection signal detected with the above-mentioned automatically adjusted sensitivity at the time of photographing reaches a preset value. Has become.

The X-ray imaging means is composed of an X-ray image intensifier and an X-ray TV camera, and the X-ray intensity detection means is an optical device between the X-ray image intensifier and the X-ray TV camera. It is also possible to adopt a configuration in which the photomultiplier is inserted in the system, and the sensitivity control means is configured to adjust the voltage supplied to the photomultiplier.

[0010]

In X-ray fluoroscopy performed prior to photographing, an automatic brightness adjustment function that changes the X-ray condition so that the brightness of the video signal automatically becomes constant is working.
Therefore, the output of the X-ray intensity detection means at this time reflects the state of the subject (such as the site and the filling degree of the contrast agent), and the output of the X-ray intensity detection means can be used as information indicating the state of the subject. Become. Therefore, the output of the X-ray intensity detection means when the brightness of the uniform subject when the fluoroscopy is set to a predetermined value is obtained in advance, and this and when the brightness of the actual subject when the fluoroscopy is set to the predetermined brightness is determined. Based on the ratio with the output of the X-ray intensity detection means, X
If the sensitivity of the line intensity detecting means is automatically adjusted, it is possible to always capture an image having an optimum density by controlling the X-ray exposure time by the integrated value of the X-ray intensity detection signal detected at that sensitivity.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, a subject 10 is irradiated with X-rays from an X-ray tube 11 so that the X-rays passing through the subject 10 are incident on an X-ray image intensifier 12. An optical image corresponding to the X-ray transmission image is output from the X-ray image intensifier 12, the optical image is sent to the X-ray TV camera 14 via the optical system 13, and the camera control unit 15 outputs the X-ray image. A video signal representing the transmission image is obtained.

This video signal is sent to the TV monitor device 16 and an X-ray transmission image is displayed on its screen. Further, this video signal is sent to the image memory 32 via the A / D converter 31. These A / D converter 31 and image memory 32 are for digital photography.

The X-ray tube 11 generates X-rays by electric power (X-ray high voltage, filament current) given from the X-ray controller 21. X-ray conditions such as the X-ray high voltage and filament current (tube voltage, tube current) are controlled by the X-ray controller 21. From the camera control unit 15,
The larger one of the average value and the peak value of the luminance of the video signal in the region having the X-ray transmission image is output as the IBS signal,
This is sent to the X-ray controller 21.

Then, during fluoroscopy, feedback control to the X-ray condition is performed so that the IBS signal has a constant value. That is, if the IBS signal is large, the X-ray tube voltage is lowered to reduce the IBS signal, and conversely, if the IBS signal is small, the X-ray tube voltage is increased to increase the IBS signal, and feedback control is performed. The brightness of the signal is automatically made constant.

Further, the X-ray controller 21 has a PMT.
22 outputs have been sent. The PMT 22 is inserted in the optical system 13 between the X-ray image intensifier 12 and the X-ray TV camera 14. The optical system 13 is provided with an optical diaphragm (not shown), and the light passing through the optical diaphragm is detected by the PMT 22. This X-ray image intensifier 12 outputs X,
The intensity of light input to the line TV camera 14 corresponds to the intensity of X-rays that pass through the subject 10 and enter the X-ray image intensifier 12.

During digital photography, X-rays are generated under the X-ray condition for photography, and the video signal of the X-ray transmission image at that time is stored in the image memory 32 via the A / D converter 31. . Then, the output of the PMT 22 is integrated by the X-ray control device 21, and when the integrated value reaches a preset mAs value, the X-ray for imaging is blocked. In this way, the image signal of the X-ray transmission image by the X-ray for photographing until it is cut off is accumulated in the image memory 32, and digital photographing is performed.

The output of this PMT 22 is further A / D
It is sent to the PMT controller 24 via the converter 23.
The PMT control device 24 controls the sensitivity of the PMT 22 by adjusting the voltage supplied to the PMT 22.

When digitally photographing the actual subject 10, first, X-ray fluoroscopy is performed, and the photographing is performed by capturing the time when the desired portion enters the visual field and the desired timing. During fluoroscopy, the automatic brightness adjustment function works as described above to control the X-ray tube voltage. As a result, the IBS signal from the camera control unit 15 is focused to a constant value, and the X-ray fluoroscopic image displayed on the screen of the TV monitor device 16 is kept at an appropriate brightness. At this time, the optical diaphragm of the optical system 13 uses the sensitivity (supply voltage) of the PMT 22 so that the time-integrated value of the output of the PMT 22 when a reference uniform subject is imaged under the X-ray condition for digital imaging becomes a constant value. Is set, and the intensity of the input light of the X-ray TV camera 14 when the uniform subject is photographed is set to be optimum. Then, in this setting, the output P2 of the PMT 22 in a stable state by the automatic brightness adjustment function when a uniform subject is seen through is A / D converted and stored by the PMT control device 24.

Next, the output P1 of the PMT 22 when the actual subject 10 is fluoroscopically observed and the brightness of the X-ray fluoroscopic image is kept constant by the automatic brightness adjustment function is A / D converted. When it is sent to the PMT control device 24, the ratio P2 / P1 with the output P2 of the previous PMT 22 is obtained, and the supply voltage to the PMT 22 is changed according to this ratio. That is, if the above-mentioned normal supply voltage is Vo, the supply voltage obtained by V = Vo × k × (P2 / P1)
The sensitivity of the PMT 22 is set by being sent to the MT 22. In the above equation, k is a coefficient.

Thus, for example, even when a contrast agent-filled image of the stomach is to be photographed, an X-ray image having an appropriate density can be photographed. That is, at this time, PMT
The daylighting field of 22 is covered with a contrast agent, and its output becomes smaller than that when a uniform subject is photographed, and unless the set mAs value is changed, the time integrated value of the output of the PMT 22 reaches the set mAs value. Although the time is extended and parts other than the contrast agent are overexposed, the supply voltage of the PMT 22 is increased to increase the sensitivity and the output of the PMT 22 is increased, so that the time integrated value of the output of the PMT 22 is the same mAs value. Therefore, it is possible to eliminate the overexposure of the portion other than the contrast agent and take an image with an appropriate density of this portion.

As described above, the PMT 2 is adjusted in accordance with the state of the subject to be actually photographed (such as the site and the filling degree of the contrast agent).
The digital X-ray image can be stored in the image memory 32 while the sensitivity of 2 automatically changes to optimize the exposure time (X-ray exposure time) even with the same set mAs value.

In the above embodiment, the supply voltage is adjusted to control the sensitivity of the PMT 22.
The amplification degree of the output system of 22 may be changed.
The PMT control device 24 may have various configurations such as one using a CPU and one constructed by hardware logic.
In addition, in order to detect the X-ray intensity transmitted through the subject 10, P
Although the MT22 is used, another semiconductor photocell or the like can be used. Furthermore, although digital X-ray photography is performed in the above, the same applies to film photography. That is, during film shooting, the film is placed in front of the X-ray image intensifier 12 (after the subject 10) (direct film shooting), or the film is placed after the X-ray image intensifier 12 (indirect film shooting). ), An X-ray transmission image is exposed on this film, and the X-ray blocking time control at this time is performed while automatically adjusting the sensitivity of the PMT 22 as described above, thereby optimizing the density of the film photographed image. be able to.

[0023]

As described in the above embodiments, according to the X-ray radiographing apparatus of the present invention, no matter how the condition of the subject (region, filling degree of contrast agent, etc.) changes, the radiography is performed prior to radiography. Because the sensitivity of the X-ray intensity detection signal for controlling the X-ray exposure time is adjusted by using the information obtained during fluoroscopy, no matter how the subject's condition changes, the doctor will always observe the optimum concentration. It is possible to capture an image that is easy to see.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

[Explanation of symbols]

 10 subject 11 X-ray tube 12 X-ray image intensifier 13 optical system 14 X-ray TV camera 15 camera control unit 16 TV monitor device 21 X-ray control device 22 PMT (photomultiplier) 23, 31 A / D converter 24 PMT controller 32 Image memory

Claims (1)

[Claims] 1. An X-ray generation means for irradiating an X-ray toward a subject, an X-ray imaging means for receiving an X-ray transmitted through the subject to obtain a video signal of an X-ray transmission image, and transmitting the subject. X-ray intensity detecting means for detecting the intensity of the X-rays, automatic brightness adjusting means for inputting a signal corresponding to the brightness of the video signal, and controlling the X-ray condition so that the brightness becomes a predetermined value. The X when the brightness of the actual subject in the fluoroscopic state becomes a predetermined value by the automatic brightness adjusting means.
The sensitivity of the X-ray intensity detecting means is adjusted to the sensitivity according to the ratio between the output of the line intensity detecting means and the output of the X-ray intensity detecting means when the luminance of the uniform subject in the transparent state becomes a predetermined value by the automatic brightness adjusting means. Sensitivity control means for automatically adjusting the sensitivity, and X detected with the above-mentioned automatically adjusted sensitivity during photographing.
An X-ray imaging apparatus having means for cutting off the X-ray for imaging when the integrated value of the line intensity detection signal reaches a preset value.