JPH0260284A - Digital subtraction angiography device - Google Patents

Abstract

PURPOSE:To reduce a motion artifact at the time of the presence of body movement by reading out designated one picture or designated plural pictures from a storage device, and setting said picture as a new mask image, and performing subtraction between this new mask image and one picture read out from the above-mentioned storage device. CONSTITUTION:The picture at the time when the injection of a contrast medium is finished and the contrast medium flowed out from a part to be inspected is designated and read out, and the above-mentioned read out picture is set as a new mask image by a mask image changing means 15, and the subtraction is performed between this and a second live image L2, and this subtraction image S2'' is displayed. An operator confirms this subtraction image S2'', and when the motion artifact A disappears, he decides that he should use the above- mentioned changed mask image M' as the future mask image for the live image. The changed mask image M' set in such a way is stored in the memory for masking of the storage device 5 as the new mask image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is directed to a digital subtraction angiography apparatus (hereinafter referred to as rDSA) used, for example, in angiography examinations.
DS that can reduce morsicon artifacts especially when there is body movement of the subject and can sufficiently display blood vessel images in subtraction images.
Regarding A device.

[Conventional technology]

To perform an angiographic examination using a DSA device, please refer to Figure 4 (a).
), a mask image M before the contrast medium is injected into the subject's body, multiple live imagers with different entrance phases of the contrast medium after the contrast medium injection, and L2°... are taken. Then, the mask image M and each live image L1°L2. . . . subtraction was performed between the two, and a subtraction image S8°S 2 t . . . as shown in FIG. 4(b) was displayed on the image display device. In such a state, if the subject's body movement occurs between, for example, the live imager's shooting and the live imager's shooting, a so-called motion artifact A will appear in the images after the second subtraction image S2. This caused the blood vessel image BztBa+ to become difficult to see.

Conventionally, as shown in FIG. 4(c), the processing in such a case is to use the live image L2 immediately after the body movement of the subject as a new mask image, that is, the remasked image RM, and
This remasked image RM and the live image L□ shown in FIG. 4(a)
, L2. . . . and remasking processing was performed to obtain subtraction images S els3'T . . . , respectively.

[Problem to be solved by the invention]

However, in the remasking process in the conventional example above,
If the new mask image after the subject's body movement, that is, the remask image RM, is already filled with contrast agent, there will not be much remaining as a blood vessel image in subsequent subtraction images, and the blood vessel image will be The images were not good for diagnosis. For example, in FIG. 4(c), the blood vessel image B□ displayed in the first subtraction image S' disappears in the third and fourth subtraction images S3'ls4'. Therefore, the blood vessel image required in the angiographic examination may not be sufficiently displayed. Moreover, since this remasking process needs to be performed every time an image is observed, the time required for observing the image is long and the diagnostic performance is degraded.

Therefore, an object of the present invention is to provide a DSA device that can solve these problems.

[Means to solve the problem]

In order to achieve the above object, a DSA apparatus according to the present invention includes an X-ray tube that irradiates a subject with Xs.

A detector is arranged opposite to this X-ray tube and converts the transmitted X-rays of the subject into visible light, a television camera takes an output optical image of this detector, and the output signal from this television camera is digitized. An A/D converter, a storage device that stores data from the A/D converter as a series of images, an arithmetic unit that performs subtraction between two specified images in this storage device, and an operation performed by this arithmetic unit. In a digital subtraction angiography apparatus comprising an image display device that displays the result as a subtraction image and a control section that controls each of the above components, one or more specified images are read out from the storage device and this image is read out. A mask image changing means is provided for setting a new mask image, and the set new mask image is stored in the storage device.

The arithmetic unit is used to perform subtraction between this new mask image and one image read from the storage device.

(Function) The DSA device configured in this manner is capable of subtraction after the image immediately after the subject's body movement occurs.
Read out one or more arbitrarily specified images in the storage device (for example, an image taken at the time when the injection of the contrast medium has finished and the contrast medium has completely flowed out from the examination site), and transfer this image to the storage device as a new mask image. At the same time, subtraction is performed using an arithmetic unit with one image after one body moves, and the subtraction image is displayed on an image display device.

Then, by sequentially performing subtraction between each image sequentially read out from the storage device and the newly set mask image and displaying subtraction images with different temporal phases, subtraction (difference calculation) is simply performed using a computing unit. ), motion artifacts caused by body movement can be reduced, and a subtraction image in which blood vessel images are sufficiently displayed can be quickly obtained.

[Embodiment] Hereinafter, an embodiment of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of a DSA device according to the present invention. This DSA device irradiates a subject with X-rays from an X-ray tube to take an XAI transmission image of the subject, and also injects a contrast medium into the subject to obtain an angiographic image. It performs contrast examinations, and as shown in Fig. 1, it consists of an X-ray tube 1, a detector 2, a television camera 3, and an A/
It includes a D converter 4, a storage device 5, an arithmetic unit 6, an image display device 7, and a control section 8.

The X-ray tube 1 irradiates the subject 9 with X-rays. The detector 2 converts the transmitted X-rays of the subject 9 into visible light, and is composed of, for example, an image intensifier, and is arranged opposite to the X-ray tube 1 with the subject 9 in between. There is.

The television camera 3 photographs the output optical image of the detector 2 and converts it into an electrical signal. The A/D converter 4 converts the output signal of the television camera 3 into a digital quantity. The storage device 5 stores the signal converted into a digital quantity by the A/D converter 4 as an image, and a frame memory 5a serves as a separate recording medium for each photographed image.

5b,...5n. The arithmetic unit 6 reads two specified images from the images stored in each frame memory 58 to 5n of the storage device 5, and performs subtraction (difference calculation) between these two images. , which displays the calculation result of the calculation unit 6 as a subtraction image, and includes an enhancement circuit 10 that emphasizes the contrast of the image, a D/A converter 11 that converts a digital signal into a video signal, and a D/A converter 11 that converts this video signal into an image. It consists of a monitor 12 for displaying images. The control unit 8 controls each of the above-mentioned components, and uses a control signal S to
Controlling the irradiation of X-rays from the ray tube 1, controlling the control signal S2
controls the capture of images by scanning the television camera 3, controls the arithmetic unit 6 using the control signal S1 to control where in the frame memories 58 to 5n the captured image data is stored, and controls The arithmetic unit 6 is controlled by the signal S4 to perform necessary arithmetic processing on the image data of each frame memory 58 to 5n.

In FIG. 1, reference numeral 13 is a top plate on which the subject 9 is placed, and reference numeral 14 is a distributor that guides light from the detector 2 to the television camera 3.

Here, in the present invention, a mask image changing means 15 is connected to the storage device 5. This mask image changing means 15 reads out one or more specified images from the images stored in the storage device 5 and changes and sets this image as a new mask image, and controls the control unit 8 sent from the control unit 8. A new mask image is set for any image in the storage device 5 by the signal S.

Next, subtraction processing and mask image changing operations when performing an angiographic examination in the DSA apparatus configured as described above will be described with reference to the flowcharts of FIGS. 2 and 3. First, by the photographing operation of the DSA device shown in FIG.
As shown in FIG. 2(a), a to 5n show a mask image M before the contrast medium is injected into the body of the subject 9, and a plurality of live images in which the contrast medium enters at different phases after the contrast medium is injected. Image L1゜L□
, ... are memorized respectively. Thereafter, the mask image M and the live image L1 . As shown in FIG. 2(b), the mask image M and each live image L11L2? are generated by key operations performed by the operator during image processing after photographing from L, . . . ... Subtraction is performed sequentially between which parts to create a subtraction image S,
, S, . . . are displayed.

The procedure is as shown in FIG. 6 performs subtraction between this mask image M and the first live image L1 to obtain a first subtraction image S1 as shown in FIG. 2(b).
2 (Step B) 1. Next, if the number of the live image is to be advanced by the operator's key operation in the "input" step, select step D.

In this step D, the live image number i is incremented by 1 to designate the second live image L2, and the process returns to before step B. In this step B, subtraction is performed between the mask image M and the second live image, and the second rM
As shown in (b), a second subtraction image S2 is obtained and displayed on the monitor 12. Thereafter, by repeating steps B and D in the same manner, the mask image M and each live image L□, L3. . . , and as shown in FIG. 2(b), subtraction images S□, s2. . . . are obtained and sequentially displayed on the monitor 12. In addition, if the number of the live image is to be returned to the previous one, step C may be selected by the operator's key operation in the "input" step.

In this state, as shown in FIG. 2, if the body movement of the subject 9 occurs between, for example, the shooting of the first live image L1 and the shooting of the second live image L2, As shown in b), a so-called motion artifact A occurs in the images after the second subtraction image S2, and the blood vessel image B
,,B,,... become difficult to see. Therefore, in the present invention, the mask image M is changed to a new mask image and subtraction is performed on the second live image L2 immediately after the body movement of the subject 9 occurs. That is, step E is activated by the operator's key operation in the step "with input" shown in FIG.
Select. Then, in step E, an image (for example) at a time when the injection of the contrast medium has finished and the contrast medium has completely flowed out from the examination site is stored from the frame memories 58 to 5n shown in FIG.
Subject 9 is in a state of maintaining the body position after the body movement)
is specified and read out, the read image is set as a new mask image by the mask image changing means 15, and the set new mask image (this is changed to "changed mask image M'" shown in FIG. 2(c)). J) and the above-mentioned second live image L□, and the subtraction image SI is displayed.The operator confirms this subtraction image S1, and if the motion artifact A disappears, the following It is determined that the above-mentioned changed mask image M' is to be used as a mask image for the live image.At this time, the number of the live image L1 at the time of change is 0 stored in the storage device 5, and then the "input holding" step , and step G is selected by the operator's key operation.

In this step G, after saving the mask image M at the time of photographing shown in FIG. I remember it.

Next, the process returns to the step "Waiting for r input" and the operator selects step D by key operation. In this step D,
Increase the number i of the live image by 1 and create the third live image,
Specify and return to before step B. In step B, the modified mask image M' stored as a new mask image is read out, and subtraction is performed between this modified mask image M' and the third live image, as shown in FIG.
), a subtraction image 83' was obtained.

Displayed on the monitor 12. Hereafter, in the same manner, step B
, D, subtraction is performed between the modified mask image M' and each live image, , L, . . . , and as shown in FIG. 2 (Q), the motion artifact disappears and the blood vessel image remain, and subtraction images S, , S, .

To end the process after displaying all the subtraction images in this manner, the operator selects step H by operating a key in the "wait for input" step. This step H
Now, as a termination process, the mask image M at the time of photographing, which was saved in the work memory in step G, is again stored in the mask memory of the storage device 5 as a mask image. This results in
Finish all processing.

Note that the changed mask image M' set as described above and the number of the live image L1 at the time of the change are stored as image information in the storage device 5, so the mask will be automatically changed from the next image observation. The image M is changed to a new mask image M', and a series of subtraction images with fewer motion artifacts can be displayed.

In addition, in FIG. 2, the modified mask image M' is specified from one frame of image, but the present invention is not limited to this. The modified mask image M' may be set by averaging the images.

In the above description, the case of displaying a subtraction image of a still image has been described, but below, the display of a subtraction image of a moving image will be explained with reference to FIG. 3. To display a moving image, go to the "Waiting for input" step shown in Figure 3.

Step F is selected by the operator's key operation.

Then, in this step F, images for one heartbeat in the time phase when the contrast medium has completely flowed out from the examination site are read out from the frame memories 58 to 5n shown in FIG. The averaged image is set as the modified mask image M' by the means 15, and the subtraction image is displayed by the control unit 8 shown in FIG. 1 using the number of the live image L1 at the time of modification as shown in FIG. Control the timing (for example, 30 frames per second).

What is necessary is to display the subtraction image on the monitor 12, in the same way as in the case of the above-mentioned still image.

The mask image M at the time of imaging is switched to the modified mask image M', and a series of subtraction images are obtained in which the motion artifact disappears and the blood vessel image remains.
2 is displayed as a moving image.

〔Effect of the invention〕

Since the present invention is configured as described above, for example, the subject 9
A new mask image (M') is stored in the memory W5 by the mask image changing means 15 for the image (L2) immediately after the body movement has occurred.
This stored modified mask image (M') and one image read from the storage device 5 (L4.L, . . . )
Subtraction is performed using the calculator 6 between the subtraction images (S, , S, ,...)
can be displayed on the image display device 7. Therefore, by simply performing subtraction using the arithmetic unit 6, the mask image changing means 15 creates a subtraction image (Sl, S) with reduced motion artifacts.

) can be obtained. Therefore, it is possible to display a plurality of subtraction images in which the contrast medium enters at different time phases on the image display device 7. Also.

In an angiographic examination, the new mask image after the body movement of the subject 9 is 1, for example, a modified mask image M' consisting of an image at a time when the injection of the contrast medium has finished and the contrast medium has completely flowed out from the examination site. A part of the blood vessel image does not disappear from the subtransition image obtained as in conventional paste mask processing, so the blood vessel image required in the angiography examination is sufficiently displayed, and good diagnostic information can be obtained. Also.

By storing the newly set changed mask image M' and the number of the live image at the time of the change in the storage device 5 as image information, the changed mask image M' can be set each time the image is observed from the next time. Subtraction images with few motion artifacts can be observed immediately without the need for This reduces the time required for image observation.
Diagnostic ability can be improved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the DSA device according to the present invention, Fig. 2 is an explanatory diagram showing subtraction processing and mask image changing operations when performing an angiographic examination, and Fig. 3 is a subtraction processing and mask image changing operation. FIG. 4 is an explanatory diagram showing conventional subtraction processing and remasking processing. DESCRIPTION OF SYMBOLS 1... X-ray tube, 2... Detector, 3... Television camera, 4... A/D converter, 5... Storage device. 6... Arithmetic unit, 7... Image display device, 8...
Control unit, 9... Subject, 15... Mask image changing means, M... Mask image, M'... Changed mask image,
L1~L4...Live image, 811~S,...
・Subtraction image.

Claims (1)

[Claims] An X-ray tube that irradiates the subject with X-rays, a detector placed opposite the X-ray tube that converts the transmitted X-rays of the subject into visible light, and a television that captures the output optical image of this detector. A camera, an A/D converter that digitizes the output signal from the television camera, a storage device that stores the data from the A/D converter as a series of images, and two specified images in the storage device. A digital subtraction angiography apparatus comprising: an arithmetic unit that performs subtraction between the two; an image display device that displays the calculation results of the arithmetic unit as a subtraction image; and a control unit that controls each of the above-mentioned components. Mask image changing means is provided for reading one or more specified images from the storage device and setting this image as a new mask image, and storing the set new mask image in the storage device and changing the new mask image. A digital subtraction angiography apparatus, characterized in that subtraction is performed between the image read from the storage device and the image read from the storage device using the arithmetic unit.