JPH07327965A - X-ray radiographic device - Google Patents

Abstract

PURPOSE:To provide an X-ray radiographing device capable of obtaining an accurate image without applying complicated dark current correction. CONSTITUTION:This X-ray radiographing device 1 provided with an X-ray tube 5 which exposes X-rays, an X-ray/optical signal conversion part 7 which converts an X-ray transmission image transmitting an examinee to an optical image, and an image pickup device 13 which picks up the optical image converted by the X-ray/optical signal conversion part 7 by plural picture elements and converts it into a video signal is provided with a memory unit 15 which accumulates the video signals of plural frames converted by the image pickup device 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray image device using a solid-state image pickup device for a TV camera, and more particularly to an X-ray image device capable of obtaining an accurate X-ray image with a small dark current component.

[0002]

2. Description of the Related Art Conventionally, an image pickup tube camera or a CCD camera has been used as an X-ray image input device. In this image pickup tube camera, a video signal (electric charge) is accumulated on the image pickup surface by applying beam blanking while irradiating X-rays. Further, in the CCD camera, the video signal is accumulated by stopping the field shift pulse.

FIG. 3 is a timing chart showing the operation timing of a conventional X-ray image device using a CCD.
As shown in FIG. 3, an image of one frame is divided into an odd field and an even field, and a conventional X-ray imaging apparatus using a frame storage CCD that alternately reads out the odd field and the even field is exposed to X-rays. The field shift pulse is stopped from time t ₁ when the X-ray exposure is started to time t ₃ when the vertical drive pulse next to the time t _{2 when} the X-ray exposure is stopped is generated. Then, from the time t ₃ , the field shift pulse is operated to output the video signal (a) of the odd field and the video signal (b) of the even field accumulated in the CCD.

[0004]

However, in the image pickup tube camera and the CCD camera, as shown in FIG. 4, the dark current component proportional to the photographing time is also accumulated at the same time. There is a problem that the current must be corrected. Furthermore, since the imaging time varies depending on the thickness of the subject, the dark current component that accumulates also varies depending on the thickness of the subject, and complicated dark current correction processing is required to obtain an accurate image. There is also. There is also a problem that it is necessary to perform a complicated CCD driving method in which the field shift pulse of the CCD is stopped during the X-ray exposure period.

The present invention has been made in view of the above circumstances, and an object thereof is to perform a complicated CCD driving method for stopping the field shift pulse of the CCD during the X-ray exposure period, and to provide a complicated CCD driving method. An object of the present invention is to provide an X-ray imaging apparatus capable of obtaining an accurate image without dark current correction.

[0006]

In order to achieve the above object, the present invention provides an X-ray source for irradiating X-rays, and an X-ray for converting an X-ray transmission image transmitted through a subject into an optical image. In an X-ray imaging apparatus including an optical signal converting unit and an image capturing unit that captures the optical image with a plurality of pixels and converts the image into a video signal, a storage unit that stores the video signals of a plurality of frames converted by the image capturing unit. It is characterized by having.

Further, an X-ray source for irradiating X-rays, X-ray-optical signal conversion means for converting an X-ray transmission image transmitted through a subject into an optical image, and the optical image is picked up by a plurality of pixels. In an X-ray image device for detecting an X-ray transmission image, which is provided with an image pickup means composed of, for example, a CCD, and extracts a part of the optical image converted by the X-ray-optical signal conversion means. When the amount of light of the optical image is detected, and when the detected value is equal to or greater than a predetermined value, the X-ray exposure by the X-ray source is stopped and a signal indicating that the X-ray exposure is stopped is output. X-ray control means for outputting, storage means for storing a video signal for a predetermined number of frames after outputting a signal indicating that the exposure of the X-rays has been stopped, and then outputting the stored signal. It is characterized by having.

As the optical-electrical signal converting means,
A frame accumulation CCD is used, and the accumulation means is the X
It is characterized in that after a signal indicating that the radiation of the line has been stopped is output, a predetermined amount of electric signal is accumulated in each of the odd field and even field of the frame accumulation type CCD, and then read out in each of the odd field and even field. I am trying.

[0009]

According to the above structure, an X-ray source for irradiating X-rays,
X-rays that convert an X-ray transmission image that has passed through the subject into an optical image-
In an X-ray imaging apparatus including an optical signal conversion unit and an image pickup unit that captures the optical image by a plurality of pixels and converts the image signal into a video signal, the storage unit includes a plurality of storage units converted by the image pickup unit. The video signal of the frame is stored.

Further, the X-ray control means extracts a part of the optical image converted by the X-ray-optical signal converting means, detects the light quantity of the optical image, and the detected value is a predetermined value or more. Then, the X-ray irradiation by the X-ray source is stopped and a signal indicating that the X-ray irradiation is stopped is output. Then, the accumulating means outputs a signal indicating that the X-ray exposure has been stopped, accumulates a predetermined number of frames of video signals, and then outputs the accumulated signal.

Further, a frame storage type CCD is used as the image pickup means, and the storage means outputs a predetermined amount of video signal from the frame storage type CCD after a signal indicating that the X-ray exposure is started is output. After accumulating each of the odd field and the even field, the odd field and the even field are read out. Therefore, an accurate image can be obtained without performing a complicated CCD driving method in which the field shift pulse of the CCD is stopped during the X-ray exposure period and without performing a complicated dark current correction.

[0012]

1 is a block diagram showing an embodiment of an X-ray imaging apparatus according to the present invention. As shown in FIG. 1, the X-ray imaging apparatus 1 of the present embodiment has an input unit (not shown), and a high voltage that generates a high voltage based on an exposure start command input by the operator from the input unit. The generator 3, the X-ray tube 5 that irradiates the subject with X-rays based on the high voltage generated by the high-voltage generator 3, and the X-rays that have passed through the subject are collected and their X-ray dose is collected. X-ray-optical signal converter 7, such as an image intensifier, a photodetector containing amorphous silicon, or a photodetector containing polycrystalline silicon, and an X-ray-optical signal converter 7 The lens 9 which collects the optical image converted by the above, the light amount attenuation filter 11 which attenuates the light amount, and the optical image which is condensed by the lens 9 and has passed through the light amount attenuation filter 11 are converted into electric charges corresponding to the light amount. Stored at a predetermined time interval Image data output for example CCD (hereinafter, referred to as a frame image.) As a video signal, the image pickup element such as a camera tube, preferably the imaging device 13 comprising a frame accumulation type CCD or progressive operable CCD imaging device 13
Provided between the lens unit 9 and the image pickup device 13, and a memory unit 15 for accumulating the video signal output by
While controlling the memory unit 15 and a photodetector 17 composed of, for example, a photomultifire, which detects a light amount of the optical image by separating a part of the optical image converted by the X-ray-optical signal conversion unit 7 with a spectroscope. , When the integrated value of the detection result of the photodetector 17 becomes equal to or more than a predetermined value, the exposure of the X-ray tube 5 is stopped by stopping the generation of the high voltage by the high voltage generator X. An X-ray controller 19 that includes a radiation exposure control circuit (AEC circuit 19a) and that outputs a signal indicating that the radiation of X-rays has been stopped (X-ray radiation stop signal) to the memory unit 15. ing.

The memory unit 15 includes an A / D converter 21 for analog / digital converting the video signal output from the image pickup device 13, and an X-ray controller 19 for outputting the video signal from the time of outputting the X-ray exposure start signal. After adding up to the frame image at the time of outputting the X-ray exposure stop signal output from the addition memory unit 23 that outputs the added video signal, and in order to display the extracted video signal on the screen and the film, A signal processing unit 25 that performs signal processing such as gamma processing, gain adjustment, image enhancement, and window processing on the video signal, and a D / A conversion unit that performs digital / analog conversion on the video signal processed by the signal processing unit 25. 27, a TV monitor 29 for displaying the video signal converted by the D / A converter 27,
An imager 31 for displaying the video signal converted by the A conversion unit 27 on a film.

Next, the operation of the X-ray imaging apparatus 1 of this embodiment will be described with reference to the timing chart of FIG. Note that, here, the image pickup device 13 is assumed to use a frame accumulation type CCD that alternately reads out odd fields and even fields.

First, the operator inputs an exposure start command to the high voltage generator 3 from an input section (not shown) provided in the high voltage generator 3. As a result, the high voltage generator 3
Then, a high voltage is generated to the X-ray tube 3, and X-ray exposure is started (time t ₁ ).

When the X-ray exposure is started, the X-ray-optical signal conversion unit 7 collects the X-rays that have passed through the subject and collects the X-rays.
Convert to an optical image according to the dose. Then, the optical image collected by the lens 9 and passed through the light amount attenuation filter 11 is accumulated by the image pickup device 13 as electric charges corresponding to the light amount.

Then, the accumulated charges are divided into an odd field and an even field according to a drive pulse generated from a CCD drive pulse generating section (not shown) provided in the image pickup device 13, and are alternately output as an output video signal. Is output to.

In the example of FIG. 2, the video signal of the odd field accumulated from time t ₀ to time t ₂ is output from time t ₂ to time t ₃ (a), and at time t ₀ (actually time The video signal of the even field accumulated from t ₁ ) to time t ₃ is output from time t ₃ to t ₄ (b). Thereafter, similarly, the video signal of the odd field accumulated between time t ₂ and time t ₄ is output between time t ₄ and time t ₅ (c), and the even number accumulated between time t ₃ and time t ₅ The field video signal is output from time t ₅ to time t ₆ (d).

When the video signal is output, in the memory unit 15, it is A / D converted by the A / D converter 21 and stored in the addition memory 23 for each odd field and even field.

On the other hand, in the X-ray controller 19, the photodetector 17 detects the amount of light (X-ray dose), and when the amount of light exceeds a predetermined value, a high voltage generated by the high voltage generator 3 is detected. The generation is stopped, and an X-ray exposure stop signal is output to the addition memory unit 23 of the memory unit 15.

When the X-ray exposure stop signal is output, the addition memory unit 23 outputs a video signal from when the X-ray exposure start command is output to when the output of the frame image to which the X-ray exposure stop signal is output ends. Is added. That is, the video signal output up to time t ₆ is accumulated in the addition memory unit 23 for each odd field and even field. Then, the accumulated odd-field video signal is output from time t ₆ to time t ₇ , and the even-field video signal is output to the signal processing unit 25 from time t ₇ to time t ₈ . Here, since the CCD used as the image pickup device 13 is a frame accumulation type, after adding up to two video signals counted from the vertical drive pulse output next to the X-ray exposure stop signal, the addition is performed. It is set in advance in the addition memory unit 23 that the output video signal is output.

In the frame accumulation type CCD used as the image pickup device 13 in this embodiment, dark current correction is performed for each frame. When the video signal is output to the signal processing unit 25, the signal processing unit 25 causes the addition memory unit 23 to operate.
In order to display the video signal output from the device on the screen and on the film, the video signal is subjected to signal processing such as gamma processing, gain adjustment, image enhancement, and window processing.

Considering the afterimage of the X-ray-optical signal conversion unit 7, etc.,
After the X-ray exposure stop signal is output, the video signals may be added until the output of a predetermined number of frame images is completed.

Then, the signal-processed video signal is D
Digital / analog conversion is performed by the / A converter 27,
The image is displayed on the screen by the TV monitor 29 and displayed on the film by the imager 31. The video signal is displayed on the screen by the TV monitor 29 and on the film by the imager 31, but either may be selectable by the operator.

As described above, in this embodiment, since the dark current-corrected video signal output from the image pickup device 13 is added and stored in the memory unit 15 at every constant storage time, an accurate image can be obtained.

In the X-ray controller 19, the photodetector 17 detects the amount of light (X-ray dose), and when the amount of light exceeds a predetermined value, a high voltage generated by the high voltage generator 3 is detected. The generation is stopped, and an X-ray exposure stop signal is output to the addition memory unit 23 of the memory unit 15. This allows the memory unit 1
In the addition memory unit 23 of 5, the X-ray controller 19
The X-ray exposure stop signal output from the above is added up to a predetermined amount counted from the time when the X-ray exposure stop signal is output, and the added video signal is output, and is incident on the imaging device 13 during X-ray exposure. Since the amount of light to be applied has a predetermined value, a correct image can be obtained by performing a constant dark current correction on the imaging device 13.

Further, since the CCD field shift pulse is constant, the CCD field shift pulse is X.
There is no need to perform a complicated CCD driving method for stopping the radiation exposure period.

Further, the image pickup apparatus 13 of this embodiment uses a frame accumulation type CCD, and the addition memory section 23 of the memory unit 15 outputs the X-ray exposure stop signal output from the X-ray controller 19. Since a predetermined amount of video signal is added to each of the odd field and the even field, and the added video signal is output, only the dark current correction normally performed for each frame by the CCD is used to complicate other complicated dark signals. An accurate image can be obtained without current correction.

[0029]

As described above, according to the present invention, since the dark current-corrected video signal output from the image pickup means is added and stored in the storage means at every constant storage time, an accurate image can be obtained. You can

Further, since the CCD field shift pulse is constant, an accurate image can be obtained without performing a complicated CCD driving method for stopping the CCD field shift pulse during the X-ray exposure period.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an X-ray imaging apparatus according to the present invention.

FIG. 2 is a timing chart showing the operation timing of the X-ray imaging apparatus of this embodiment.

FIG. 3 is a timing chart showing the operation timing of a conventional X-ray imaging apparatus.

FIG. 4 is an explanatory diagram showing a dark current level included in a video signal with respect to a shooting time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 X-ray imaging apparatus 3 High voltage generator 5 X-ray tube 7 X-ray-optical signal conversion unit (X-ray-optical signal conversion means) 9 Lens 11 Light intensity attenuation filter 13 Imaging device (imaging means) 15 Memory unit (storage means ) 17 photodetector (X-ray-optical signal conversion means) 19 X-ray controller 21 A / D conversion unit 23 addition memory unit 25 signal processing unit 27 D / A conversion unit 29 TV monitor 31 imager

Claims (4)

[Claims] 1. An X-ray source that emits X-rays, an X-ray-optical signal conversion unit that converts an X-ray transmission image that has passed through a subject into an optical image, and the optical image is captured by a plurality of pixels. An X-ray image apparatus comprising: an image pickup unit for converting the image signal into a video signal by a storage unit for storing a plurality of frames of video signals converted by the image pickup unit. 2. An X-ray source for irradiating X-rays, an X-ray-optical signal conversion means for converting an X-ray transmission image transmitted through a subject into an optical image, and the optical image is picked up by a plurality of pixels. In the X-ray image device for detecting an X-ray transmission image, the imaging device converts the optical image into a video signal, and extracts a part of the optical image converted by the X-ray-optical signal conversion device to obtain a light amount of the optical image. Is detected, and when the detected value exceeds a predetermined value, X by the X-ray source is detected.
X-ray control means for stopping the exposure of X-rays and outputting a signal indicating that the exposure of X-rays is stopped, and a predetermined number of frames after the signal indicating that the exposure of X-rays is stopped is output. An X-ray imaging apparatus comprising: a storage unit that stores a minute video signal and then outputs the stored signal. 3. The X-ray imaging apparatus according to claim 1, wherein a CCD is used as the image pickup means. 4. A frame storage type C as the imaging means
By using a CD, the accumulating means accumulates a predetermined number of video signals for every odd field and even field of the frame accumulating CCD after the signal indicating the start of X-ray exposure is output, and then the odd number. The X-ray imaging apparatus according to claim 2, wherein the field and even field are read out.