JPH0846869A - Digital x-ray photographing device - Google Patents

Abstract

PURPOSE:To manage relative movement for the examinee of a photographing system performing X-ray photographing to be performed only once when run subtraction or rotary subtraction is performed. CONSTITUTION:An X-ray tube 21 irradiates X-rays, and the X-ray transmitting the examinee 10 is made incident on an X-ray image intensifier 22, and an image signal is obtained from an X-ray television camera 23 at every frame, simultaneously, those photographing systems are moved in the direction of arrowhead A for the examinee 10, and image data are digitized by an A/D converter 31, and subtraction can be performed between the adjacent frames of the digital image data in real time by an image arithmetic unit 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital X-ray imaging apparatus, and more particularly, to a contrast agent obtained by digitizing an image signal obtained by combining an X-ray image intensifier and an X-ray television camera and subjecting it to subtraction processing. The present invention relates to a digital X-ray imaging apparatus having a function of extracting only images.

[0002]

2. Description of the Related Art Conventionally, X-rays have been used to direct X-rays toward an object.
The X-ray transmitted through the object is irradiated to the X-ray image intensifier, the X-ray image intensifier is connected to an X-ray television camera, and an X-ray transmission image signal is obtained. Is used as a fluoroscopic image on a monitor device or the like to be useful for medical diagnosis.
Then, by digitizing this image signal and performing subtraction processing, the background image is canceled by subtracting the image without contrast agent from the image with contrast agent, and the image with only contrast agent is extracted. Is also being done. In this case, for example, by injecting a contrast agent into a blood vessel, an image that clearly shows only the blood vessel can be obtained.

When obtaining such a subtraction image, it is necessary to move the image pickup system with respect to the subject if the image pickup range is larger than the visual field of the image pickup system. Further, in order to obtain a subtraction image of the subject viewed from various directions, it is necessary to rotate the imaging system with respect to the subject. In these, the imaging system is run or rotated with respect to the subject in both a state without a contrast agent and a certain state,
At each of them, image data is obtained for each traveling position or each rotational position. Then, by post processing (post-processing) of the collected image data, subtraction is performed between the image data obtained at the same running position or the same rotating position among the image data obtained at these two running or rotating times, I am trying to cancel the background image. In this way, if subtraction images for each position during running are obtained, these can be displayed one after another on one screen, so that the field of view runs in one direction while chasing the contrast agent flowing in the blood vessel, for example. A movie-like display is obtained. In addition, if the subtraction images at each position during rotation are sequentially displayed on one screen in time, a moving image-like display can be obtained in which the blood vessel filled with the contrast agent is viewed from each direction while rotating. This makes it possible to easily grasp the three-dimensional positional relationship of blood vessels.

[0004]

However, in the conventional traveling subtraction or rotating subtraction, the imaging system must be moved or rotated twice and X-ray imaging must be performed for each of them. However, there is a problem in that it is twice as large as the case of once. Further, for the same reason, the imaging time is required to be doubled, which causes a problem that the patient's restraint time becomes too long. Long inspection time also means poor inspection throughput. Another problem is that the subtraction image cannot be obtained in real time, because the subtraction image is obtained by post-processing the image data.

In view of the above, the present invention requires only one relative movement (linear or rotational movement) of the imaging system with respect to the subject when carrying out traveling subtraction or rotational subtraction, and data is collected in the process. An object of the present invention is to provide a digital X-ray imaging apparatus capable of processing image data in real time to obtain a subtraction image, reducing exposure dose, and shortening examination time.

[0006]

In order to achieve the above object, in the digital X-ray imaging apparatus according to the present invention,
X-ray irradiating means for irradiating the subject with X-rays, X-ray imaging means for receiving the X-rays transmitted through the subject to obtain an image signal of an X-ray transmission image, and these X-ray irradiating means and X A means for moving an image pickup system including a line image pickup means relative to a subject, and an image signal for each frame sequentially obtained during the movement is digitized, and the image signals of the adjacent frames of the digital image data are digitized. It is characterized in that it is provided with an image calculation means for performing subtraction in real time.

The above-mentioned image calculation means may perform smoothing processing on one of the two subtracted digital image data and edge enhancement processing on the other.

The above-mentioned image calculation means synthesizes digital image data of one frame from digital image data of two frames which are adjacent to the digital image data of a certain frame and are temporally preceding and succeeding the digital image data. The subtraction between the digital image data and the digital image data of one frame may be performed.

Further, the above-mentioned image calculation means averages digital image data of one frame by averaging digital image data of two frames which are adjacent to the digital image data of one frame and which are preceding and succeeding in time. , And the combined digital image data and the above 1
The subtraction may be performed between the digital image data of one frame.

Further, the image calculation means multiplies a predetermined constant by each of the digital image data of three or more frames which are adjacent to the digital image data of one frame and which are adjacent in time. Combine the digital image data of one frame by adding above,
Subtraction between the combined digital image data and the digital image data of one frame may be performed.

[0011]

The image pickup system including the X-ray irradiating means and the X-ray image pickup means is moved relative to the subject (in a linear direction or in a rotating direction), and an image signal for each frame is moved during the movement. For example, if a contrast agent is flowing in the blood vessel of the subject, the other parts are stationary except for the contrast agent, so subtraction between images of adjacent frames can be performed. For example, it is possible to cancel the background image excluding the moving portion of the contrast agent. in this case,
It is common sense that it is difficult to completely cancel the background image because there is a positional shift between the images of adjacent frames, but the positional shift between the images of adjacent frames is very small. However, the effect of canceling the background image is practically sufficient. By the way, when the image is moved twice as in the conventional case, some displacement is inevitable even between images obtained at the same position, and it can be said that the displacement is rather small compared to this. As a result, a subtraction image with an image quality that is never inferior to that obtained when moving twice as in the conventional case can be obtained. Since it is sufficient to perform X-ray imaging with one movement, it is possible to reduce the exposure dose to the subject and also shorten the examination time. Further, since the subtraction image is not obtained by post-processing but is obtained in real time during movement of the image pickup system, it is possible to adjust the movement of the image pickup system while observing it.

If the smoothing process is performed on one of the two subtracted digital image data and the edge enhancement process is performed on the other, the canceling effect of the background image is improved and the S / N ratio of the subtraction image is increased.

The subtraction between the digital image data of a large number of frames sequentially obtained in real time during the movement of the image pickup system is performed by the digital image data of a certain frame and the two adjacent to the frame temporally before and after.
When the digital image data of one frame is combined with the digital image data of one frame, the position of the combined image is close to the position of the image of the above-mentioned one frame. The canceling effect becomes good.

Further, the subtraction between the digital image data of a certain number of frames, which is sequentially obtained in real time while the image pickup system is moving, is performed with the digital image data of a certain frame and the two adjacent to the frame in time before and after. What is performed between the digital image data of one frame and the digital image data of one frame synthesized by averaging the digital image data of one frame is that an image at a position similar to the position of the image of one frame is time-slotted in that frame. Since it is obtained by averaging the images of two adjacent frames in the front and rear, it is more practical and the background image canceling effect is good.

Further, not only the images of two frames adjacent in time before and after the image of one frame in this way, but also the digital image data of a large number of three or more frames before and after in time are used. , If each of these is multiplied by a predetermined constant and then added to synthesize an image of one frame, the synthesized image should be regarded as an approximation of the position of the image of one frame. Therefore, if subtraction is performed between this composite image and the image of the above-mentioned one frame, a subtraction image in which the background image is canceled well can be obtained.

[0016]

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 laid and held on a top plate of a bed 11 installed on the floor of the examination room, and the X-ray tube 21 and the X-ray image intensity are sandwiched so as to sandwich the subject 10. The combination of the fire 22 and the X-ray television camera 23 is arranged to face each other. An imaging system such as the X-ray tube 21, the X-ray image intensifier 22, the X-ray television camera 23, etc. is held by a holding device (not shown in the figure), and is linear with respect to the subject 10 in the arrow A direction. Can be moved. Alternatively, the top plate of the bed 11 may be moved linearly with respect to the imaging system so that the imaging system moves relative to the subject 10. The image pickup system such as the X-ray tube 21, the X-ray image intensifier 22, the X-ray television camera 23 and the bed 11 are controlled by the image pickup system controller 27.

Under the control of the image pickup system control unit 27, X
As shown in FIG. 2A, X-ray irradiation is performed in a pulsed manner from the radiation tube 21, and at the same time, the imaging system is moved in the direction of arrow A. At this time, the X-ray television camera 23 sequentially outputs the image signals of the respective frames in synchronization with the pulsed X-ray irradiation, as shown in FIG. This image signal is sent to the image processing device 30, converted into digital image data by the A / D converter 31, and then stored in the image memory 32. At this time, (c) of FIG.
As shown in (d), images of each frame are alternately collected as a mask image and a live image.

If the image data P (i) of the i-th frame is obtained by the i-th X-ray exposure and is collected as the live image L (i), in this embodiment, (i-1 ) Th image data P (i-1) by (i-1) th X-ray irradiation and (i + 1) th image data P (i + 1) by (i + 1) th X-ray irradiation,
The mask images M (i-1) and M (i + 1) are used, and a synthetic image obtained by averaging the mask images is used as the live image L.
The image calculation device 33 performs the calculation subtracted from (i). That is, S (i) = L (i)-{M (i-1) + M (i + 1)}
The subtraction image S (i) is obtained by performing the arithmetic processing of / 2.

The digital subtraction image thus obtained is sent to the D / A converter 34 and converted back into an analog image signal, which is sent to the image monitor device 41. Since the above-described arithmetic processing is performed in real time every time an image signal is sequentially obtained from the X-ray television camera 23 in synchronization with the pulsed X-ray exposure, the moving image of the subtraction image is displayed on the screen of the image monitor device 41. Will be displayed in real time.

Here, as described above, the mask image M (i-
The composite image obtained by averaging 1) and M (i + 1) can be approximated to the one captured at the position of the i-th frame. This composite image and the live image L (i) of the i-th frame are considered to be images taken from the same position, which is not a problem. Therefore, if the contrast agent is flowing in the blood vessel of the subject 10, only the movement of the contrast agent in the blood vessel can be extracted by the above subtraction. Therefore, for example, when the imaging system is moved so as to follow the contrast agent flowing in the blood vessel for imaging, the screen moves in accordance with the movement of the tip of the contrast agent so that the tip of the tip moves. The motion is displayed like a movie. Since it can be displayed in real time in this way, the movement of the imaging system can be made faster or slower according to the movement of the contrast agent, and even if this is done, there is no inconvenience to the subtraction image displayed on the screen. Does not occur.

If the mask image is subjected to smoothing processing and then the above-mentioned averaging operation is performed, the live image is subjected to edge enhancement processing, and subtraction operation is performed between them. The background image canceling effect is further improved, and the S / N ratio is increased.

Further, for one live image L (i),
Two mask images M (i-1) and M of the frames before and after that
Not only is (i + 1) used, but more mask images, for example ... M (i-5), M (i-3), M (i-
It is also possible to use 1), M (i + 1), M (i + 3), .... In this case, these are multiplied by an appropriate constant α (i) and then added to synthesize one mask image. This constant α (i) is, for example, as shown by the dotted line in FIG.
It becomes smaller as it goes away from (i). That is, assuming that n live images are used, S (i) = L (i)-{... + α (i-5) M (i-5) + α (i-3) M (i-3) + α (i-1) M
(i-1) + α (i + 1) M (i + 1) + α (i + 3) M (i + 3) + ...} / n is calculated to obtain the subtraction image S (i). . Live image L subject to subtraction
Since the mask image is synthesized by performing weighted addition averaging according to the degree of approximation to (i), the closeness of this mask image (the live image L (i) should be obtained at the position where the image was taken). Of the mask image and the live image L (i) are subtracted, the background image canceling effect and the S / N ratio in the subtraction image are further improved.

In the above embodiment, the case where the image pickup system is linearly moved in one direction relative to the subject 10 has been described, but the same is true when the image pickup system is moved in the rotational direction.
In this case, as shown in FIG. 3, the X-ray tube 21, the X-ray image intensifier 22, and the X-ray TV camera 23 are held at both ends of the C-shaped arm 24, and the C-shaped arm 24 is rotated and driven. 25, the C-arm 24 is rotationally driven in the arc direction shown by the arrow B. The rotation driving device 25 is rotatably held by a stand 26 in a direction in which the C-shaped arm 24 is inclined. When the image pickup system is rotationally driven by the rotary driving device 25, pulsed X-ray irradiation is performed from the X-ray tube 21 as in the above-described embodiment.
If an image signal synchronized with it is obtained from the X-ray television camera 23, the same image processing as above can be performed.

[0024]

As described in the above embodiments, according to the digital X-ray imaging apparatus of the present invention, the imaging system is moved by moving the imaging system depending on whether the contrast agent is present in the subject or not. A subtraction method in which the background image is canceled and the image of only the contrast agent is extracted by one moving X-ray photograph with the contrast agent injected into the subject without the need to perform two moving X-ray photographs. You can get a statue. In this way, one X-ray scan during movement is sufficient,
The X-ray exposure dose to the subject can be reduced, and the inspection time can be shortened to improve the inspection throughput. Further, it is possible to obtain a subtraction image in real time while moving the imaging system and performing X-ray imaging.

[Brief description of drawings]

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

FIG. 2 is a time chart for explaining the operation of the embodiment of FIG.

FIG. 3 is a schematic view of another embodiment.

[Explanation of symbols]

 10 subject 11 bed 21 X-ray tube 22 X-ray image intensifier 23 X-ray TV camera 24 C-type arm 25 rotation drive device 26 stand 27 imaging system control device 30 digital image processing device 31 A / D converter 32 image memory 33 Image operation device 34 D / A converter 41 Image monitor device

Claims (1)

[Claims] 1. An X-ray irradiating unit that irradiates an X-ray toward a subject, an X-ray imaging unit that receives an X-ray transmitted through the subject to obtain an image signal of an X-ray transmission image, and these X-ray irradiators. Means for moving an image pickup system composed of a ray irradiating means and an X-ray image pickup means relative to a subject, and an image signal for each frame sequentially obtained during the movement is digitized to obtain the digital image data. And an image calculation means for performing subtraction between adjacent frames in real time.