JPH088092A - X-ray television apparatus - Google Patents

Abstract

PURPOSE:To magnify the range of the thickness of a subject for photography which is displayed at proper picture quality. CONSTITUTION:An X-ray controller 9 automatically controls the voltage of an X-ray tube 1 according to the brightness of an image so that the brightness of the image is held constant. When the tube voltage thus adjusted exceeds a value kVd, an automated iris device 5 automatically increases the aperture of its diaphragm; when the tube voltage decreases below another value kVa, the device 5 automatically decreases the aperture of the diaphragm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray TV apparatus for displaying a fluoroscopic image as an image signal on a TV system on a TV monitor.

[0002]

2. Description of the Related Art In an X-ray TV set, as shown in FIG.
The subject (inspection person) 2 is irradiated with X-rays from the X-ray tube 1, the X-rays transmitted through the subject 2 are made incident on the image intensifier 3, and the X-ray image is converted into an optical image. The output image is guided to the TV camera 7 by an optical system, converted into an image signal, and this image signal is sent to the TV monitor device 8 to be displayed so that the X-ray fluoroscopic image can be observed in real time. The optical system is an objective lens 4 that makes the output light of the image intensifier 3 parallel light.
And an eyepiece 6 for forming an image on the TV camera (image pickup tube) 7. Then, in order to make the amount of light incident on the TV camera 7 appropriate, the diaphragm device 10 is inserted between the objective lens 4 and the eyepiece lens 6.

Normally, automatic control (pervious automatic brightness adjustment) is performed so that the brightness of the image displayed on the TV monitor device 8 becomes constant. That is, a signal representing the brightness (average or typical brightness) of the image displayed on the TV monitor device 8 is sent to the X-ray control device 9, and the X-ray control device 9 responds to the brightness signal by the X-ray. The tube voltage applied to the tube 1 is automatically controlled. Therefore, when the subject 2 is thick and the amount of incident X-rays to the image intensifier 3 is small, the brightness of the image is lowered, so that the tube voltage of the X-ray tube 1 is increased to compensate for this, and conversely. When the subject 2 is thin and the brightness of the image is high, the tube voltage is lowered. Therefore, looking at the relationship between the thickness of the subject 2 and the fluoroscopic tube voltage when such automatic fluoroscopic brightness adjustment is performed, it can be seen that there is a relationship as shown in FIG. This is the TV monitor device 8
It shows how the fluoroscopic tube voltage required to keep the brightness of the image displayed by is changed depending on the subject thickness.

Therefore, conventionally, the diaphragm device 10 is adjusted based on the relationship shown in FIG. That is, first, the fluoroscopic tube voltage (kVo) at the standard subject thickness (To) is determined, and when the subject having this thickness To is placed, the tube voltage becomes the above kVo.
Adjust 0. The tube voltage kVo is a value with which the image quality of the image displayed on the TV monitor device 8 is appropriate with respect to the standard subject thickness, and the maximum subject thickness Ta is assumed. It is necessary to select a value that provides sufficient coverage.

[0005]

However, when the diaphragm device 10 in the optical system is adjusted as in the conventional case, the tube voltage of the X-ray tube 1 is reduced when the thickness of the subject 2 becomes near Ta. It is near the maximum value, and a transparent image without contrast is displayed.
As for the subject 2 having a thickness exceeding a, the transmitted X-ray dose decreases, so that the image itself is not displayed on the TV monitor device 8.

In view of the above, it is an object of the present invention to provide an X-ray TV apparatus improved so that the range of subject thickness on which an image of appropriate quality is displayed can be expanded.

[0007]

In order to achieve the above object, in an X-ray TV apparatus according to the present invention, an X-ray tube for irradiating a subject with X-rays, and an X-ray image input through the subject. Image intensifier for outputting as an optical image, an optical system for transmitting an output image of the image intensifier, a TV camera for converting the image transmitted through the optical system into an image signal, and the image signal Is transmitted to display the image, and the brightness of the image displayed on the TV monitor is predetermined by controlling the tube voltage applied to the X-ray tube according to the brightness of the image. When the tube voltage exceeds a predetermined first value, it is inserted into the optical system to adjust the amount of light incident on the TV camera. Rino increases the opening degree, that the above tube voltage and a automatic iris device to reduce the degree of opening of the throttle when less than a predetermined second value is the distinctive feature.

Here, the above automatic diaphragm device may be capable of continuously changing the opening degree of the diaphragm, or it is sufficient if at least two stages of opening degrees of the diaphragm can be obtained. It is also possible to switch between two different diaphragms.

[0009]

Since the tube voltage is controlled according to the brightness of the image so that the brightness of the displayed image becomes constant,
The thicker the subject, the higher the tube voltage to compensate for the decrease in brightness. The subject's thickness exceeds a certain thickness,
When the tube voltage exceeds the first value, the aperture of the diaphragm is increased and the amount of light incident on the TV camera is increased. Therefore, the brightness of the image is increased, and as a result, the tube voltage is decreased by the above control. In other words, the margin to the maximum value of the tube voltage is increased, and it becomes possible to perform the tube voltage control so that the brightness is appropriate even for a thicker subject. When the subject becomes thin and the brightness of the image rises, and the tube voltage becomes lower due to the tube voltage control according to the brightness and falls below the second value, the aperture of the diaphragm is reduced and the TV camera The amount of incident light is suppressed. Therefore, the brightness of the image is lowered, and the tube voltage is increased by the control according to the above brightness, so that it becomes possible to display a thinner object with proper brightness.

If an automatic diaphragm device that can continuously change the opening of the diaphragm is used, the opening when the opening of the diaphragm is increased and the opening when the opening of the diaphragm is decreased. The opening degree can be arbitrarily adjusted at any time, and the degree of correspondence to the subject is enhanced.

Since the automatic diaphragm device only needs to obtain at least two stages of diaphragm openings, two diaphragms having different openings are used.
If the two diaphragms are switched, the cost can be reduced. In this case, if the apertures of the two diaphragms can be adjusted in advance, the operation is a little cumbersome and the degree of correspondence to the subject is the same.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the drawings. In FIG. 1, X
An X-ray beam is emitted from the radiation tube 1 toward the subject 2.
The X-ray beam that has passed through the subject 2 is incident on the input surface of the image intensifier 3. The image intensifier 3 converts the incident X-ray image into an optical image and outputs it. The output light representing the optical image is converted into parallel light by the objective lens 4, the amount of the light is adjusted by the auto iris device (automatic diaphragm device) 5, and then is imaged on the TV camera 7 through the eyepiece lens 6. The image signal obtained by the TV camera 7 is sent to the TV monitor device 8 and an X-ray fluoroscopic image is displayed in real time.

The X-ray controller 9 includes a TV monitor 8
A signal representing the brightness (average or typical brightness) of the image displayed by is sent, and the tube voltage applied to the X-ray tube 1 is adjusted in accordance with this brightness so that the image brightness is constant. Is automatically controlled. When the subject 2 becomes thicker by this automatic control, the incident X-ray dose decreases, so that the luminance becomes lower and the tube voltage rises. However, the tube voltage exceeds a certain value kVd as shown in FIG. At this time, the auto iris device 5 automatically increases the aperture of the diaphragm. The aperture of the throttle up to that point is small.

In the auto iris device 5, the aperture amount (opening) when the opening is small, as shown in FIG. 2, is the standard subject thickness To as in the conventional case, so that the image quality of the image becomes appropriate. It is adjusted so that a transparent tube voltage kVo can be obtained. At this time, the fluoroscopic tube voltage changes along the curve from the point 21 to the point 22 in the region where the subject is thin.

When the subject 2 becomes thick and reaches the point 22 and the tube voltage reaches the value kVd, the aperture of the diaphragm of the auto iris device 5 is increased as described above, and the brightness of the image is increased. The tube voltage is reduced to kVc by the tube voltage control according to the brightness by the X-ray controller 9. That is, it moves from the point 22 to the point 23. Then this point 2
The fluoroscope voltage changes on the curve where 3 is on (from point 24 to point 25). Therefore, when the subject 2 becomes thicker, it moves to the point 24 and the tube voltage reaches the maximum value. It is possible to display with the optimum image quality (luminance, contrast, etc.) up to the thickness Tb at this time. When the subject 2 becomes thicker than the thickness Tb, the tube voltage does not rise further, so that the incident X-ray dose decreases as the subject 2 becomes thicker, and the brightness of the image gradually decreases. However, if there is no such switching in the auto iris device 5, the range of the subject thickness where the optimum image quality is obtained is expanded as compared with the case where the tube voltage becomes the maximum value at the thickness Ta (see the dotted line). In addition, the thickness of the image until it becomes almost invisible due to a decrease in the brightness becomes significantly large, which means that the thickness range in which the image can be seen through is widened while the image quality is poor.

After that, if the subject becomes thin, the fluoroscope voltage drops to point 25 and becomes kVa. When the tube voltage reaches kVa, the aperture of the diaphragm in the auto iris device 5 is returned to the original small one.
As a result, the amount of light is narrowed down, so that the brightness is lowered, and as a result, the tube voltage rises to kVb and returns to the point 26 on the original curve. Here, kVa <kVd is set so that hysteresis occurs in the characteristic curve of the fluoroscopic tube voltage.
It is designed to stabilize the operation.

Regarding the switching of the diaphragm in the auto iris device 5, the auto iris device 5 may be configured to detect the tube voltage and switch it, and the X-ray tube control device 9 may automatically switch the iris according to the tube voltage. It is also possible to configure the switching by controlling the device 5.

Further, in this embodiment, the auto iris device 5 is assumed to be capable of continuously changing the opening of the diaphragm steplessly. However, as described above, the opening of the diaphragm can be switched in at least two steps. It is only necessary to provide two diaphragms having different apertures, and it is possible to switch between these diaphragms. In that case, regarding the opening of each of the two throttles,
It will be adjusted separately beforehand.

[0019]

As described in the above embodiments, according to the X-ray TV apparatus of the present invention, the diaphragm for adjusting the amount of light incident on the TV camera is automatically switched according to the tube voltage of the X-ray tube. The range of subject thickness displayed with appropriate image quality can be expanded, a perspective image with good contrast can be obtained even for a thick subject, and a thicker subject can be seen through.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between subject thickness and fluoroscope voltage in the example.

FIG. 3 is a schematic diagram of a conventional example.

FIG. 4 is a graph showing the relationship between subject thickness and fluoroscope voltage in a conventional example.

[Explanation of symbols]

 1 X-ray tube 2 Subject 3 Image intensifier 4 Objective lens 5 Auto iris device 6 Eyepiece 7 TV camera 8 TV monitor device 9 X-ray control device 10 Aperture device

Claims (1)

[Claims] 1. An X-ray tube for irradiating a subject with X-rays, an image intensifier for outputting an X-ray image input through the subject as an optical image, and an output image of the image intensifier. Optical system for transmitting the image, a TV camera for converting the image transmitted through the optical system into an image signal, a TV monitor device for transmitting the image signal to display the image, and the above-mentioned image display device according to the brightness of the image. An X-ray control device for controlling the tube voltage applied to the X-ray tube so that the brightness of the image displayed on the TV monitor device becomes a predetermined value, and for adjusting the amount of light incident on the TV camera. When the tube voltage exceeds a predetermined first value, the aperture of the diaphragm is enlarged, and when the tube voltage falls below a predetermined second value, Small opening An X-ray TV device, comprising: an automatic diaphragm device for cutting.