JP2820195B2 - Digital X-ray equipment - Google Patents

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 by digitizing an image signal obtained by a combination of an X-ray image intensifier and an X-ray television camera and performing a subtraction process. The present invention relates to a digital X-ray imaging apparatus having a function of extracting only an image.

[0002]

2. Description of the Related Art Conventionally, X-rays have been directed from an X-ray tube toward a subject.
The X-ray transmitted through the subject is incident on an X-ray image intensifier, and an X-ray television camera is coupled to the X-ray image intensifier to obtain an image signal of an X-ray transmission image. Is displayed as a fluoroscopic image on a monitor device or the like, which is useful for medical diagnosis.
Then, the image signal is digitized and then subjected to subtraction processing to subtract the image without the contrast agent from the image with the contrast agent to cancel the background image and extract the image of only the contrast agent. Has also been 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, if the imaging range is larger than the field of view of the imaging system, it is necessary to move the imaging system with respect to the subject. Further, in order to obtain subtraction images 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 the state without the contrast agent and the state with the contrast agent,
In each case, image data is obtained for each traveling position or for each rotation position. Then, by the post-process (post-processing) of the collected image data, of the image data obtained in these two runs or rotations, subtraction is performed between the image data obtained in the same running position or the same rotating position, The background image is canceled. If the subtraction images at each position during traveling are obtained in this way, these are sequentially displayed on one screen, so that, for example, the visual field travels in one direction while following the contrast agent flowing in the blood vessel. A video-like display is obtained. In addition, if the subtraction images for each position during rotation are sequentially displayed on one screen in time, a moving image-like display in which a blood vessel filled with a contrast agent is viewed from each direction while rotating is displayed. This makes it possible to easily grasp the three-dimensional positional relationship of the blood vessels.

[0004]

However, in the conventional traveling subtraction or rotary subtraction, the imaging system must be run or rotated twice and X-ray photography must be performed for each of them. Is twice as large as in the case of once. Further, for the same reason, there is a problem that the photographing time is required twice and the restraining time of the patient becomes too long. A longer inspection time also means a lower inspection throughput. Furthermore, since a subtraction image is obtained by post-processing of image data, there is a problem that a subtraction image cannot be obtained in real time.

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 performing a running subtraction or a rotational subtraction, and collects them in the process. It is an object of the present invention to provide a digital X-ray imaging apparatus capable of obtaining a subtraction image by processing image data in real time, reducing an exposure dose and shortening an examination time.

[0006]

In order to achieve the above-mentioned object, a digital X-ray imaging apparatus according to the present invention is commonly used for an X-ray imaging apparatus according to the first to fourth aspects of the present invention. X-ray irradiating means for irradiating X-rays, X-ray imaging means for irradiating X-rays transmitted through a subject to obtain an image signal of an X-ray transmission image, and these X-ray irradiating means and X-ray imaging means Means for moving the imaging system relative to the subject, digitizing image signals for each frame sequentially obtained during the movement, and subtracting a subtraction between adjacent frames of the digital image data in real time. It is characterized in that it is provided with an image calculation means for performing.

According to the first aspect of the present invention, the image calculation means performs a smoothing process on one of the two digital image data to be subtracted and performs an edge enhancement process on the other of the two digital image data. The feature is that subtraction is performed in real time between frames to be processed.

According to the second aspect of the present invention, the image processing means is obtained by synthesizing digital image data of one frame and digital image data of two frames immediately before and after the frame. It is characterized in that subtraction with digital image data of one frame is performed in real time.

According to a third aspect of the present invention, the image calculating means averages the digital image data of one frame subjected to the edge enhancement processing and the digital image data of two frames immediately before and after the frame. It is characterized in that subtraction with digital image data of one frame obtained by performing synthesis and smoothing processing is performed in real time.

[0010] In the invention described in claim 4, the above-mentioned image calculation means performs the processing on each of the digital image data of one frame and the digital image data of three or more frames before and after immediately adjacent to the frame. It is characterized in that subtraction is performed in real time with digital image data of one frame obtained by synthesizing by multiplying by a predetermined constant and adding.

[0011]

The invention can be said as follows in common in the inventions described in claims 1 to 4. Moving an imaging system composed of X-ray irradiating means and X-ray imaging means relative to the subject (in a linear direction or a rotating direction);
When sequentially obtaining image signals for each frame during the movement, for example, when a contrast agent is flowing in the blood vessel of the subject,
Except for the contrast agent, the other portions are stationary, so if subtraction is performed between images of adjacent frames, the background image excluding the portion where the contrast agent has moved can be canceled. In this case, it is common sense to think that it is difficult to completely cancel the background image because there is a displacement between the images of the adjacent frames, but the displacement between the images of the adjacent frames is Since it is only minute, the effect of canceling the background image is practically sufficient. By the way, when the image is moved twice as in the related art, it is unavoidable that the images obtained at the same position are slightly misaligned with each other. For this reason, a subtraction image with image quality that is never inferior to that obtained when moving twice as in the related art can be obtained. Since X-ray imaging may be performed in one movement, the exposure dose to the subject can be reduced, and the examination time can be shortened. In addition, the subtraction image
Instead of being obtained by post-processing, it is obtained in real time while the imaging system is moving, so while observing it,
It is also possible to adjust the movement of the imaging system.

According to the first aspect of the present invention, the subtraction between the digital image data of many frames sequentially obtained in real time while the imaging system is moving is performed by performing smoothing processing on one of the two digital image data to be subtracted. Since the edge enhancement processing is performed on the other side, the effect of canceling the background image is improved, and the S / N ratio of the subtraction image is increased.

According to the second aspect of the present invention, the subtraction between the digital image data of a plurality of frames sequentially obtained in real time while the imaging system is moving is performed by combining the digital image data of a certain frame and the digital image data of the frame in time. This is performed between the digital image data of one frame synthesized from the digital image data of two adjacent frames before and after, and the position of the synthesized image is determined by the above-mentioned 1
The position of the image in one frame,
The effect of canceling the background image is good.

According to the third aspect of the present invention, the subtraction between the digital image data of a large number of frames sequentially obtained in real time while the imaging system is moving is performed by the edge-enhanced digital image data of a certain frame and the frame. And by averaging the digital image data of two adjacent frames before and after in time, and performing the smoothing with the digital image data of one frame obtained. The position of the synthesized image is The position approximates the position of the image of one frame described above,
Further, since the averaging method is adopted as the synthesizing method, the image is more practical. In addition, since the image of one frame is edge-emphasized and the synthesized image is smoothed, the effect of canceling the background image is reduced. It becomes good and the S / N ratio increases.

According to the fourth aspect of the present invention, not only images of two frames temporally adjacent to an image of a certain frame but also three images temporally before and after the image of a certain frame are obtained.
Using digital image data of one or more many frames,
An image of one frame is synthesized by multiplying each of these by a predetermined constant and adding them.
Since the synthesized image can be regarded as having an improved positional approximation to the image of the one frame, by performing subtraction between the synthesized image and the image of the one frame, Thus, it is possible to obtain a subtraction image in which the background image is well canceled.

[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 held by being laid on a top plate of a bed 11 placed on the floor of an examination room, and an X-ray tube 21 and an X-ray image intensity are sandwiched between the subject 10. The combination of the fire 22 and the X-ray television camera 23 is arranged to face each other. The imaging systems such as the X-ray tube 21, X-ray image intensifier 22, and X-ray television camera 23 are held by a holding device not shown in FIG. Can be moved. Alternatively, the top plate of the bed 11 may be moved linearly with respect to the imaging system, and the imaging system may be moved relative to the subject 10. The imaging 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 imaging system controller 27.

Under the control of the imaging system controller 27, X
As shown in FIG. 2A, X-ray irradiation is performed from the tube 21 in a pulsed manner, and at the same time, the imaging system is moved in the direction of arrow A. At this time, the image signal of each frame is sequentially output from the X-ray television camera 23 in synchronization with the pulsed X-ray exposure 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 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.

Then, assuming that image data P (i) of the i-th frame is obtained by the i-th X-ray exposure and this is collected as a live image L (i), in this embodiment, (i-1) ) -Th X-ray irradiation (i-1) -th image data P (i-1) and (i + 1) -th X-ray irradiation (i + 1) -th image data P (i + 1)
Using the mask images M (i-1) and M (i + 1) as the mask images and averaging the mask images, the composite image
The calculation to be subtracted from (i) is performed by the image calculation device 33. That is, S (i) = L (i)-{M (i-1) + M (i + 1)}
/ 2 is performed to obtain a subtraction image S (i).

The digital subtraction image obtained in this way is sent to a D / A converter 34, converted back into an analog image signal, and sent to an image monitor 41. Since the above-described arithmetic processing is performed in real time each time an image signal is sequentially obtained from the X-ray television camera 23 in synchronization with the pulsed X-ray irradiation, a moving image-like image of a 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-
A composite image obtained by averaging 1) and M (i + 1) can be approximated to an image captured at the position of the i-th frame. This combined image and the live image L (i) of the i-th frame are considered to be images captured from the same position, and are not inconvenient. Therefore, assuming that the contrast agent flows 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-described subtraction. Therefore, for example, when imaging is performed by moving the imaging system so as to follow the contrast agent flowing in the blood vessel, the screen is moved in accordance with the movement of the tip of the contrast agent, and the tip of the tip is moved. Movement is displayed like a movie. Since the image can be displayed in real time in this way, the movement of the imaging system can be made faster or slower in accordance with the movement of the contrast agent, and even so, there is no disadvantage in the subtraction image displayed on the screen. Does not occur.

The above-described averaging operation is performed on the mask image after performing the smoothing process, the edge enhancement process is performed on the live image, and the subtraction operation is performed between them. Thus, the effect of canceling the background image 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 previous and subsequent frames
In addition to using (i + 1), more mask images, for example,... M (i-5), M (i-3), M (i-
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. The constant α (i) is, for example, as shown by a dotted line in FIG.
It becomes smaller as the distance from (i) increases. 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
An arithmetic processing of (i-1) + α (i + 1) M (i + 1) + α (i + 3) M (i + 3) +... / n is performed to obtain a subtraction image S (i). . Live image L subject to subtraction
Since the mask image is synthesized by performing weighted averaging according to the degree of approximation to (i), the closeness of this mask image (the live image L (i) should have been obtained at the position where the image was taken) Of the combined mask image and the live image L (i), 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 imaging system is linearly moved in one direction relative to the subject 10 has been described, but the same applies to the case where the imaging system is moved in the rotation direction.
In this case, as shown in FIG. 3, an X-ray tube 21, an X-ray image intensifier 22, and an X-ray television camera 23 are held at both ends of a C-arm 24, respectively. 25 drives the C-arm 24 in the direction of the circular arc indicated by arrow B to rotate. 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 imaging system is rotationally driven by the rotation driving device 25, pulse-like X-ray irradiation is performed from the X-ray tube 21 in the same manner as in the above-described embodiment.
If an image signal synchronized with the signal is obtained from the X-ray television camera 23, the same image processing as described above can be performed.

[0024]

As described above, according to the digital X-ray imaging apparatus of the present invention, the imaging system is moved depending on whether the contrast agent is present in the subject or not in the subject. A subtraction in which a background image is canceled and an image containing only a contrast agent is extracted by one-time X-ray imaging while a contrast agent is injected into a subject without having to perform X-ray imaging during two movements. An image can be obtained. In this way, only one X-ray imaging while moving is sufficient.
The X-ray exposure dose to the subject can be reduced, and the inspection time can be shortened, thereby improving the inspection throughput. Further, a subtraction image can be obtained in real time during X-ray imaging while moving the imaging system.

[Brief description of the 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. 1;

FIG. 3 is a schematic view of another embodiment.

[Explanation of symbols]

 Reference Signs List 10 subject 11 bed 21 X-ray tube 22 X-ray image intensifier 23 X-ray television camera 24 C-arm 25 rotation drive 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 (4)

(57) [Claims] An X-ray irradiating means for irradiating an X-ray toward a subject, an X-ray imaging means for receiving an X-ray transmitted through the subject to obtain an image signal of an X-ray transmission image, Means for relatively moving an imaging system comprising a beam irradiating means and an X-ray imaging means with respect to a subject; digitizing image signals for each frame sequentially obtained during the movement; Digital image processing means for performing a smoothing process on one image data and an edge emphasizing process on the other image data, and performing subtraction in real time between adjacent frames. X-ray equipment. 2. X-ray irradiating means for irradiating an X-ray toward a subject, X-ray imaging means for receiving an X-ray transmitted through the subject to obtain an image signal of an X-ray transmission image, Means for moving an imaging system consisting of the X-ray irradiating means and the X-ray imaging means relative to the subject; digitizing image signals for each frame sequentially obtained during the movement, and Image processing means for performing subtraction in real time between digital image data and digital image data of one frame obtained by synthesizing digital image data of two frames immediately before and after the frame. A digital radiography apparatus characterized by the above-mentioned. 3. X-ray irradiating means for irradiating the subject with X-rays, X-ray imaging means for receiving an X-ray transmitted through the subject to obtain an image signal of an X-ray transmission image, Means for moving an imaging system consisting of the X-ray irradiating means and the X-ray imaging means relative to the subject; digitizing image signals for each frame sequentially obtained during the movement, and Between the edge-enhanced digital image data and the digital image data of one frame obtained by combining and smoothing by averaging the digital image data of the two preceding and succeeding frames that are temporally adjacent to the frame A digital X-ray imaging apparatus, comprising: an image calculating means for performing the subtraction in real time. 4. X-ray irradiating means for irradiating the subject with X-rays, X-ray imaging means for irradiating X-rays transmitted through the subject to obtain an image signal of an X-ray transmission image, Means for moving an imaging system consisting of the X-ray irradiating means and the X-ray imaging means relative to the subject; digitizing image signals for each frame sequentially obtained during the movement, and One frame obtained by synthesizing the digital image data and the digital image data of three or more frames before and after the frame temporally adjacent to the frame by multiplying them by a predetermined constant and adding the results is added. A digital X-ray imaging apparatus, comprising: image calculation means for performing subtraction with digital image data in real time.