JP2680334B2 - X-ray equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an X-ray imaging apparatus capable of performing automatic brightness adjustment, and more particularly, to a cine of proper brightness by reducing the dependence of tube voltage. The present invention relates to an X-ray imaging apparatus capable of performing imaging.

(Prior Art) Conventionally, automatic brightness adjustment provided in an X-ray imaging apparatus is
The exposure time (mS) is fixed, and the tube voltage (kV) and the tube current (mA) are adjusted as appropriate to obtain the optimum brightness.

(Problems to be Solved by the Invention) In the conventional X-ray imaging apparatus having such automatic brightness adjustment, the optimum brightness adjustment in cine imaging is performed by changing kV under a predetermined exposure time, mA. However, there is a problem that kV changes greatly depending on the thickness of the subject, and kV is low when the body thickness is thin and too high when the body thickness is thick.

Therefore, an object of the present invention is to provide an X-ray imaging apparatus capable of setting the optimum brightness by reducing the dependency of kV during cine imaging. Another object of the present invention is to provide an X-ray imaging apparatus that can obtain an image with the same contrast even if the subject changes.

[Structure of the Invention] (Means for Solving the Problems) The present invention has a structure in which the following means are taken in order to solve the above problems and achieve the object. That is, the present invention relates to an X-ray imaging apparatus capable of automatic brightness adjustment, in which X-rays are taken at a predetermined tube voltage which is predetermined prior to cine imaging.
X-ray exposure time to obtain the optimum brightness at the above-mentioned predetermined tube voltage is obtained by performing a test exposure of the rays, and in cine photography, the X-ray exposure time is fixed to the exposure time obtained in the test exposure. Further, it is characterized in that the tube voltage and the tube current are made variable to perform automatic brightness adjustment.

(Operation) According to such a configuration, since the cine imaging can be started under the X-ray condition that provides the optimum brightness with the tube voltage fixed in advance, at the time of cine imaging, the value of the tube voltage fixed in advance or in the vicinity thereof. Optimal brightness can be obtained simply by adjusting the tube voltage to a value. Also, since the exposure time is determined so that X-rays of the same tube voltage are exposed regardless of the thickness of the subject, it is possible to take an image with the tube voltage as set, and as a result, the subject Even if it changes, it is possible to obtain an image with the same contrast.

(Embodiment) An embodiment of the X-ray imaging apparatus according to the present invention will be described below with reference to FIG.

In FIG. 1, reference numeral 1 is an X-ray tube for irradiating X-rays, which is connected to a high voltage generator 2. The X-ray tube 1 irradiates an X-ray under an X-ray condition (kV, mA, mS) determined by a signal from the X-ray control system received by the high voltage generator 2, and the X-ray is the subject 3
To the image and intensifier 4 and is photoelectrically converted to generate a transmission image of the subject. This image is optically distributed to a cine camera 6 and a television camera 7 by an optical distributor (optical system) 5, and is imaged on a cine film in the cine camera 6 and on a TV monitor 9 via the television camera control unit 8 in the television camera 7, respectively. Is projected as.

Here, an automatic brightness adjusting mechanism is provided so that these images can always be observed at a constant brightness, and the operating principle thereof is as follows. In the optical system 5, a photo sensor for detecting the brightness of an image is built in, and the amount of light, that is, the brightness of the image is converted into an electric signal. This signal is amplified by the amplifier 10. The amplifier 11 is an operational amplifier for integrating the signal amplified by the amplifier 10 with the capacitor 11. The switch 13 is designed to open when X-ray irradiation starts and close when X-ray irradiation ends. The circuit composed of the amplifier 11, the capacitor 12, and the switch 13 is a sample hold circuit, and the sample hold circuit can detect the brightness of the image. The detected brightness passes through the multiplexer 15 controlled by the CPU 14 and is analog / analogized by the A / D converter 16.
It is digitally converted and taken into CPU 14 as data.

On the other hand, the set value for optimizing the brightness is input from the input terminal 17 thereof, and is taken into the CPU 14 through the multiplexer 15 similarly to the brightness signal of the image. Here, in CPU14,
Both the integrated value of the brightness signal from the sample hold circuit and the brightness setting value from the input terminal 17 are compared, and when the integrated value of the brightness signal is higher than the brightness setting value, the X-ray condition is lowered. If it is low, the X-ray condition is increased. As a result, it is possible to always observe an image with a constant brightness regardless of the change in subject thickness, that is, the magnitude of X-ray absorption.

In this case, the X-ray condition is controlled by CPU14, and kV, mA
The signals are digital-to-analog converted by the D / A converters 18, 18 and sent to the high voltage generator 2 as signals.

Also, the X-ray exposure time is controlled by the CPU 14,
The X-ray exposure signal is sent to the high voltage generator 2 for the time set in the programmable timer 19. High voltage generator 2
X in accordance with these kV signal, mA signal, and X-ray exposure signal.
X-rays are generated from the ray tube 1.

In the X-ray control system as described above, in order to obtain the optimum X-ray condition before the start of cine imaging, test X-ray irradiation is performed with a preset tube voltage, and the integrated value of the luminance signal is set to a set value. As shown in FIGS. 2 (a) and 2 (b), first, the signals are compared in the shortest X-ray exposure time, and if the signal output is smaller than the set value, the next 2
The second test X-ray exposure is performed at the maximum allowable X-ray exposure time.

When the signal output is larger than the set value in the signal comparison in the second X-ray exposure, the third X-ray X-ray exposure is performed in accordance with the ratio of the set value of the signal output. The time is shortened, and the test X-ray exposure is stopped when the integrated value of the photomultiplier output signal reaches the optimum output value which is the brightness setting value. The X-ray exposure time at this time is set in the programmable timer 19 and is set as the X-ray exposure time for imaging.

When the radiography is started, this X-ray exposure time is fixed, and automatic brightness adjustment is performed while controlling kV and mA as before.

In the signal comparison by the second test X-ray exposure, if the signal output is still smaller than the set value, the third test X-ray exposure raises the tube voltage by a predetermined value (several kV), The signal comparison is performed at the shortest X-ray exposure time. This case is shown in FIGS. 3 (a) and 3 (b). After that, the method until the optimum X-ray condition is obtained is the same as that described above. kV
If the optimum signal output is not obtained even during the longest X-ray exposure time, the test exposure is stopped and the imaging sequence is stopped, assuming that the imaging cannot be performed.

In the signal comparison by the first test X-ray irradiation, if the signal output is larger than the set value, the second test X-ray irradiation lowers the tube voltage by a predetermined value (several kV), The signal comparison is performed at the shortest X-ray exposure time. This case is shown in FIGS. 4 (a) and 4 (b). After that, the method until the optimum X-ray condition is obtained is the same as that described above. 2
If the signal output is still larger than the set value in the signal comparison during the second shortest X-ray exposure time, the test X-ray exposure is stopped and the imaging sequence is also stopped because the imaging cannot be performed.

When comparing the signals by the shortest X-ray exposure time, when the formal output signal waveform is close to the optimum output,
It goes without saying that the optimum X-ray condition is obtained by setting the X-ray exposure time by the ratio of the signal output and the optimum output without setting the next X-ray irradiation as the longest X-ray exposure time.

As described above, in this embodiment, the preset kV
When performing test X-ray exposure while changing the imaging time, the test X-ray exposure is performed with the maximum exposure time and the minimum exposure time that can be set, and within the range of the two X-ray exposure times. When the optimum X-ray exposure conditions are required, the third test X-ray exposure stops the X-ray exposure in the middle when the optimum conditions are reached, stores the exposure time, and stores the optimum X-ray exposure. Since the shooting is started according to the shooting time, the shooting can be started with an arbitrary kV according to the shooting site and the like, and the automatic brightness adjustment after the start can also be taken in the vicinity of the starting kV.

Therefore, since automatic brightness adjustment is performed with kV and mA, it is possible to follow a large change in subject thickness, and it is possible to always obtain a photograph with stable density according to the purpose of photography.

The present invention is not limited to the above embodiments, but can be implemented with various modifications without departing from the spirit of the present invention.

[Effects of the Invention] As described above, according to the present invention, X that can perform automatic brightness adjustment is used.
In a radiographic apparatus, the exposure time at the time of cine imaging is obtained from the X-ray exposure conditions prior to cine imaging, and in cine imaging, the exposure condition is fixed to a predetermined voltage and the tube voltage is fixed. By changing the tube current and performing automatic brightness adjustment, it is possible to start cine photography under X-ray conditions that provide optimum brightness with a tube voltage that is fixed in advance. Optimum brightness can be obtained simply by adjusting the tube voltage to a value near that value. Also,
Irradiation time is determined so that X-rays with the same tube voltage are exposed regardless of the thickness of the subject, so it is possible to shoot with the tube voltage as set, and as a result, the subject changes. Can obtain images with the same contrast.

Therefore, according to the present invention, it is possible to provide an X-ray imaging apparatus capable of setting the cine imaging to the optimum brightness while reducing the dependency of kV.

[Brief description of the drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the X-ray imaging apparatus according to the present invention, and FIGS. 2 to 4 are operation waveform diagrams of the simultaneous embodiment, respectively. 1 ... X-ray source, 2 ... High voltage generator, 3 ... Subject, 4 ... Image intensifier, 5 ... Optical distributor, 6 ... Cinema camera, 7 ... TV camera, 8 ... TV camera control unit, 9 ... TV Monitor, 10, 11 ... Amplifier, 12 ... Capacitor, 13 ... Switch, 14 ... CPU, 15 ... Multiplexer, 16
… A / D converter, 17… Input terminal, 18… A / D converter, 19… Programmable timer.

Claims (1)

(57) [Claims] 1. An X-ray imaging apparatus capable of automatic brightness adjustment, wherein a test exposure of X-rays is performed at a predetermined tube voltage that is determined in advance before cine imaging, and optimum brightness is obtained at the predetermined tube voltage. The X-ray exposure time is obtained, and in cine photography, the X-ray exposure time is fixed to the exposure time obtained in the test exposure, and the tube voltage and the tube current are made variable to perform automatic brightness adjustment. X-ray imaging device.