JPS59226342A - X-ray photographing device - Google Patents

Abstract

PURPOSE:To prevent the loss of a photographic range of a camera to improve its accuracy by keeping a detection level constant when a maximum voltage of the video signal has a certain level or higher in case that the position of an X-ray diaphragm is determined in accordance with the video signal. CONSTITUTION:A system P which detects a peak voltage of the video signal limits the peak voltage to a certain value VC or smaller by a peak level clamping circuit. This clamp level can be set freely by a variable resistance VR1. Then, a threshold level is set to muVp if the peak voltage passing through a buffer 1' and a variable resistance CR is VC or lower, and it is set to muVC if the peak voltage exceeds VC. The aperture width of the X-ray diaphragm in the video signal is detected by a comparator. Since the threshold is set to a cartain voltage in this manner, the aperture diaphragm does not break the photographic range to make it accurate even if a part of a picture is very bright.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an Xls imaging apparatus, and more particularly to an apparatus that performs indirect X-ray imaging while changing the X-ray irradiation field.

The application and practical use of X@television equipment to medical diagnosis has brought revolutionary progress and development to conventional X-ray diagnostic methods, freeing X-ray diagnosticians from darkroom work and reducing X-ray exposure. Because of the great advantage of reducing radiation exposure, a large number of devices are now used in daily X-ray diagnostic work not only in Western countries but also in Japan, and the number of devices is expected to increase in the future.

On the other hand, during this fluoroscopic diagnosis or when taking images on X-ray film depending on the diagnostic condition, depending on the part, the image tone may be selected to make it easier to observe, or the lead may be moved to avoid X-ray exposure to areas other than the necessary parts of the subject. Tetsumitsu uses an aperture to adjust the X-ray irradiation field as appropriate.

That is, in FIG. 1, 1 is an X-ray generator, 2 is a lead aperture, and 6 is an aperture adjuster. When the diaphragm 2 is opened or closed by the adjuster 3, the irradiation angle of the X-rays changes, and the irradiation field (the area on the image conversion surface where X&l is incident) can be changed. 4 is amplified by a subject, for example, a human body, and outputted. 6a is a projection lens which has a function of converting output image light into parallel light;
b and 60 are respectively imaging lenses for imaging parallel light. Reference numeral 7 denotes an optical path switching mirror, which guides the light beam from the photographing lens 6a to the imaging lens 6b or 6C by installing or removing the switching mirror 7 obliquely.

8 is a video camera, 9 is a video receiver, 10 is a camera, 11 is a roll film, 12 is a controller, 1
6 is an aperture stop.

Here, when X-rays are irradiated through the subject 4, an X-ray image of the subject enters the input surface of the image intensifier 5, and is formed as a developable image on the output surface.

When the switching bell 7 is set at the position indicated by the broken line, a transmitted image of the subject is re-formed on the imaging surface of the video camera 8 and displayed on the video receiver 2. When the examiner (doctor) secures the image and releases it, the switching mirror 7 is switched to the position shown by the solid line, and an image transmitted by the imaging lens 6C is formed on the roll film 11, which is exposed. . At that time, the examiner takes pictures while changing the aperture wind of the aperture 2 using the adjuster 6, but when the irradiation field is changed by changing the amount of aperture, the shadow of the aperture appears on the left and right edges of the screen of the video receiver 9. appears, and a transmitted image is projected in the irradiation field between them.

Therefore, if the roll film feed fik is constant even though the range in which the image cover actually appears changes, when the image area eE is narrow, the corresponding amount of film will be wasted.

To deal with this, a controller 12 is provided to inspect the video signal, detect the width of the shadow of the right aperture and the shadow of the left aperture, that is, the length of the irradiation field, and calculate the detected amount to the camera film. Input to the winding mechanism. At this time, the opening width of the aperture stop 16 is changed according to the stop 2 to prevent fogging of the image. FIG. 2 shows how the distance between the shadows of the X-ray diaphragm is detected from the video signal. FIG. 2(C) is a signal related to the Nff1st scanning line of the perspective image, and FIG.
3) shows the X DA m view displayed on the monitor.

As shown in the figure, the area directly irradiated with X-rays is
It shows the maximum voltage Vp, and the part where X-rays are not irradiated by the X-ray aperture, that is, the part where no image is formed, is ■φ (
pedestal voltage). Note that S is a synchronization signal. Conventionally, in order to distinguish the shadow of the X-ray diaphragm, μVp, which is the maximum voltage Vp of the X-ray irradiation unit multiplied by a constant P (0, 2≦μ≦0.6), is used as a threshold. The area lower than the voltage was identified as the shadow of the X KBA aperture, and the camera's aperture curtain was closed to the aperture area of the camera that corresponded to that shadow.

With this method, when the maximum voltage Vp is low as shown in FIG. 6, the threshold μVp as the detection level faithfully detects the range of the X-ray aperture. However, as shown in Fig. 4, if the subject has a region with very good XM transmittance that increases the brightness on the display and the maximum voltage Vp is very high, the threshold value μVp also becomes high, as is clear from the figure. A range smaller than the actual X-ray aperture is detected. For this reason, the aperture diaphragm on the camera side is narrowed down to the inside based on this detection information, resulting in the disadvantage that a necessary image is lost.

An object of the present invention is to provide an X-ray imaging apparatus that eliminates the drawbacks of the conventional example.

In order to achieve this object, the present invention is characterized in that the threshold level is set to a constant value when the maximum voltage Vp exceeds the voltage.

FIG. 5 shows a principle diagram of the present invention.

In FIG. 5, when the maximum voltage Vp exceeds a constant voltage VC, the threshold value becomes μVp (pVc).

That is, when the maximum voltage Vp is smaller than Vc, the threshold value is μV.
p, and when it exceeds VC, it becomes a constant value μ regardless of the value of vp.
It becomes Vc.

Thereby, even when the maximum voltage Vp is high, the normal opening range of the X-ray diaphragm can be detected.

FIG. 6 is an example of a block diagram of an electrical detection system implementing the present invention.

P in the figure is a system that detects the peak voltage of the video signal, and the peak voltage is set to a certain value V by a peak level clamp circuit.
Limit to less than c.

This clamp level can be freely set by variable resistor vR1. As a result, the threshold level is set to μV if the peak voltage is within Vc via the buffer 1' and the variable resistor VR.
p, and when the peak voltage exceeds Vc, it is set to μVc. Then, a comparator determines x in the video signal.
The aperture width of 6 stops is detected.

In the peak level clamp circuit, a circuit may be provided in which the clamp voltage is set in advance by the variable resistor va-1 and is automatically varied in accordance with the pedestal level φ.

Further, a circuit may be provided to selectively set this clamp voltage to several levels depending on the maximum voltage Vp of the video signal.

Thereby, the aperture width of the Xi aperture can be normally detected regardless of the various values of the peak voltage Vp.

In the above explanation, the peak voltage Vp was detected based on the blanking level, but it is also possible to set the measurement reference level to a hetal level instead of the blanking level.

That is, the maximum voltage ■p' of the video signal is measured with the pedestal level as a reference, and if the maximum voltage ■p' is within the partial value Vc' with the pedestal level as a reference, the threshold value is μVp / with the pedestal level as a reference. , and if it exceeds a certain value Vc', the threshold value can be set to μVc'' with the pedestal level as a reference.

As described above, according to the present invention, when determining the X-ray diaphragm position from the video signal, by setting the threshold to be less than or equal to the 11L pressure level for a portion of the image, even if a portion of the image is a very bright X-ray fluoroscopic image, the film can be The imaging range of the upper X-ray beam can be set to the normal Cζ7 without causing a large loss in the aperture diaphragm of the camera.

[Brief explanation of the drawing]

FIG. 1 is a diagram of an embodiment of the X-ray (Jν) imaging device according to the present invention. FIG. The figure is an explanatory diagram for measuring the aperture width of a conventional X-ray diaphragm. Figure 5 is a principle diagram of the present invention. Figure 6 is a block diagram of an electrical detection system implementing the present invention. 1 is the X-ray generator, 2 is the aperture, 6 is the aperture W11\J1
4 is a subject, 8 is a video camera, 9 is a video receiver, 10 is a camera, 11 is a roll film, 12 is a controller, and 13 is an aperture stop. Applicant: Gyanon Co., Ltd.

Claims (1)

[Claims] 1. In a device that detects the opening amount of an X-ray diaphragm using a video signal and makes film advance and aperture diaphragm of a camera variable. An X-ray imaging apparatus characterized in that a detection level is kept constant above a level at which a maximum voltage of a video signal occurs. 2. The X-ray imaging apparatus according to claim 1, wherein the detection level is set in multiple stages depending on the maximum voltage of the video signal. 3. The X-ray imaging apparatus according to claim 1, wherein the detection level is automatically varied according to fluctuations in the petal level corresponding to the X-ray aperture region.