JP2838522B2 - Digital subtraction angiography device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a digital
Subtraction angiography system (hereinafter "DSA
DSA) that can reduce motion artifacts, especially when the subject moves, and can sufficiently display blood vessel images in subtraction images.
Related to the device.

[Conventional technology]

In order to perform an angiographic examination using a DSA apparatus, as shown in FIG. 4 (a), a mask image M before a contrast medium is injected into the body of a subject and a phase time when the contrast medium enters after the contrast medium is injected. multiple live images L ₁ having different, L _2, shooting ..., each with the mask image M live image L _1, L _2, performs subtraction between ... and as shown in FIG. 4 (b) Subtraction image S ₁ , S
₂ , ... were displayed on the image display device. In this state, for example when the subject's body motion with the imaging of the live image L ₁ shooting live image L ₂ is to occur, the second subtraction image S ₂ and subsequent image called motion artifact A , And the blood vessel images B ₂ , B ₃ ,... Were difficult to see.

Conventionally, the processing in such a case is shown in FIG.
As shown in, the subject new mask image the live image L ₂ immediately after the body motion has occurred, i.e. a re-mask image RM, live image L ₁ shown in re-mask image RM and FIG. 4 (a), L ₂ …
And a remasking process for obtaining subtraction images S ₁ ′, S ₃ ′,... Has been performed.

[Problems to be solved by the invention]

However, in the remasking process in the above-described conventional example, if the new mask image after the body movement of the subject, that is, the remask image RM is already filled with the contrast agent, the blood vessel image is The blood vessel image was not a good diagnostic image. For example, in FIG. 4 (c), third and fourth subtraction image S ₃ ', S _4' be those vessel image B ₁ that has been displayed in the first subtraction image S ₁ 'disappear Was. Therefore, the blood vessel image required in the angiography examination may not be sufficiently displayed. In addition, since the remask 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 reduced.

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

[Means for solving the problem]

In order to achieve the above object, a DSA apparatus according to the present invention is an X-ray tube for irradiating an object with X-rays, and is arranged to face the X-ray tube and converts transmitted X-rays of the object into visible light. A detector, a television camera that captures an optical image output from the detector, an A / D converter that digitizes an output signal from the television camera, and data from the A / D converter that captures the data from within the subject. A storage device that stores a plurality of live images having different time phases after injection of a contrast agent and a contrast image after injection of a contrast agent as a series of images, and a storage device that has a different time phase from the designated mask image in the storage device. In a digital subtraction angiography apparatus comprising a computing unit for performing subtraction between a live image and an image display device for displaying a computation result by the computing unit as a subtraction image, A mask image changing means for reading one image or a plurality of images at the time when the contrast agent has completely flowed out of the examination site in the subject and setting the image as a new mask image, and storing the set new mask image in the storage device And the subtraction is performed between the new mask image and each live image read from the storage device by using the arithmetic unit.

(Operation)

The DSA device configured as described above, for example, the subtraction from the image immediately after the body movement of the subject occurs,
From the storage device, one or more images of the time phase in which the contrast agent has completely flowed out of the examination site in the subject are read and set as a new mask image after the body movement of the subject, and the set new mask image is set. Is stored in the storage device, and a subtraction is performed between the new mask image and each live image read from the storage device using an arithmetic unit, and the subtraction image is displayed on the image display device. In this manner, subtraction is sequentially performed between each live image sequentially read from the storage device and the newly set mask image, and the subtraction images having different phases are displayed. By simply performing (difference calculation), it is possible to reduce a motion artifact when there is a body motion and quickly obtain a subtraction image in which a blood vessel image is sufficiently displayed.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of a DSA device according to the present invention. This DSA device uses the X-ray
An X-ray transmission image of the subject is obtained by irradiating the subject with an X-ray, and a contrast medium is injected into the subject to obtain an angiographic image taken and subjected to an angiographic examination, as shown in FIG. And X
Ray tube 1, detector 2, television camera 3, A / D converter 4, storage device 5, calculator 6, image display device 7
And a control unit 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 the X-ray tube 1 with the subject 9 interposed therebetween.
And are arranged to face each other. The television camera 3 captures an optical image output from the detector 2 and converts the optical image into an electric signal. The A / D converter 4 converts the output signal of the television camera 3 into a digital value. The storage device 5 captures the data converted into a digital amount by the A / D converter 4 and stores a plurality of live images having different phases in a mask image before injection of a contrast agent into the subject and a time phase after injection of the contrast agent. It is stored as a series of images, and has frame memories 5a, 5b,... 5n as separate recording media for each captured image. The arithmetic unit 6 sequentially reads out the specified mask image and each live image having a different time phase from the images stored in the frame memories 5a to 5n of the storage device 5, and performs subtraction (difference calculation) between the two images. Is what you do. The image display device 7
The arithmetic unit 6 displays the calculation result as a subtraction image. The enhancement circuit 10 enhances the contrast of the image, the D / A converter 11 converts a digital signal into a video signal, and displays the video signal as an image. And a monitor 12. The control unit 8 controls each of the above-mentioned components, and controls the X-ray tube 1 from the X-ray tube _{1 according} to a control signal S1.
To control the irradiation of the line, or controls the image capture by scanning the television camera 3 by the control signal S _2, the control signal S ₃
Where to control whether to store, and the control signal S ₄ by image by controlling the arithmetic unit 6 the frame memories 5a~5n frame memory 5a~5n image data captured above by controlling the calculator 6 by Control is performed so that required arithmetic processing is performed on the data.

In FIG. 1, reference numeral 13 denotes a top plate on which the subject 9 rests, and reference numeral 14 denotes a distributor for guiding light from the detector 2 to the television camera 3.

Here, in the present invention, the mask image changing means 15 is connected to the storage device. This mask image changing means 15
Reads one or more images of the time phase in which the contrast agent has completely flowed out of the examination site in the subject from the images stored in the storage device 5 and changes the read image as a new mask image after the body movement of the subject intended to set, is controlled so as to set the new mask image for the image of the appropriate time phase in the storage device 5 by the control signal S ₅ sent from the control unit 8.

Next, a subtraction process and a mask image changing operation when performing an angiographic examination in the DSA apparatus configured as described above will be described with reference to the flowcharts of FIGS. First, the respective frame memories 5a to 5a of the storage device 5 are operated by the photographing operation of the DSA device shown in FIG.
5n, as shown in FIG. 2 (a), a mask image M before the injection of the contrast agent into the body of the subject 9, and a plurality of live images L having different phases when the contrast agent enters after the injection of the contrast agent. ₁ , L ₂ ,... Are respectively stored. Then each frame memory as described above
Mask image M and live image stored in 5a to 5n L _1, L _2, by a key operation by the operator from ... is performed by the image processing after shooting, the second
As shown in FIG. 2B, the mask image M and each live image L ₁ , L ₂ ,
, And subtraction is sequentially performed to display subtraction images S ₁ , S ₂ ,.

The procedure, as shown in FIG. 3, first, as a number i of the live image, specifies the first live image L ₁ (Step A). Then, specify a mask image M, and subtraction between the calculator 6 by live image L ₁ The mask image M in the above-described first, as shown in FIG. 2 (b) first subtraction image S ₁ is obtained and displayed on the monitor 12 of the image display device 7 (step B). Next, when the live image number is to be advanced as it is by the key operation of the operator in the step of “waiting for input”, step D is selected. In this step D, the live image number i is increased by 1 and the second live image
Specify the L _2, return to the previous step B. Then, in step B, and subtraction between the mask image M and the second live image L _2, as shown in FIG. 2 (b) to obtain a second subtraction image S _2, the monitor 12 indicate.
Hereinafter, by repeating steps B and D in the same manner, subtraction is performed between the mask image M and each of the live images L ₁ , L ₂ ,..., As shown in FIG. Subtraction images S ₁ , S ₂ , ... with different approach phases
It is displayed on the monitor 12 sequentially. If the live image number is to be returned to the previous number, the operator may select Step C by operating the key in the “waiting for input” step.

In this state, as shown in FIG. 2, for example, when the body motion of the subject 9 occurs between the first imaging of the live image L ₁ of the imaging and the second live image L _2, the Figure (b), the the second subtraction image S ₂ and subsequent image called motion artifact a is generated, the blood vessel image B _2, B _3,
… Becomes difficult to see. Therefore, in the present invention, the subtraction by changing a mask image M in a new mask image with respect to the second live image L ₂ immediately after body movement of the subject 9 occurs. That is, step E is selected by the key operation of the operator in the step of “waiting for input” shown in FIG. Then, in this step E, the frame memory shown in FIG.
From 5a to 5n, specify the image of the time phase in which the injection of the contrast agent has been completed and the contrast agent has completely flowed out of the examination site in the subject (the subject 9 is in a state in which the postural position has been maintained). The image read out by the mask image changing means 15 is set as a new mask image after the body movement of the subject, and the set new mask image (this is referred to as “changed” shown in FIG. 2C). And the second live image L _2.
Subtraction between and the subtraction image
S ₂ ″ is displayed.
If motion artifact A disappeared to confirm S ₂ ", it is determined that the use of the above changes the mask image M 'as a mask image for subsequent live images. At this time, number of live image L ₁ at the time of change Are stored in the storage device 5.
Next, the process returns to the step of “waiting for input”, and selects step G by key operation of the operator. In this step G,
After the mask image M at the time of photographing shown in FIG. 2A is retracted to the work memory, the changed mask image M 'set as described above is set.
Is stored in the mask memory of the storage device 5 as a new mask image.

Next, the process returns to the step of "waiting for input", and selects step D by key operation of the operator. In this step D, the number i of the live image is increased by 1 and the third live image
Specify the L _3, return to the previous step B. Then, in step B, 'it reads, this change mask image M' new mask changes the mask image stored as image M by subtraction between the said third live image L ₃ of FIG. 2 (c) As shown in the figure, a subtraction image S ₃ ″ is obtained,
Display on the monitor 12. Hereinafter, similarly, steps B and D
Is repeated to obtain the changed mask image M 'and each live image.
Subtraction is performed between L ₁ , L ₂ ,..., And as shown in FIG. 2 (c), the motion artifact disappears and the blood vessel image remains, and the subtraction image S ₂ ″, where the contrast agent enters at a different phase, is displayed. S ₃ ″,... Are obtained and sequentially displayed on the monitor 12.

To end the display after displaying all the subtraction images in this manner, the operator selects a step H by operating the key in the "waiting for input" step. In this step H, as a termination process, the mask image M at the time of photographing that has been saved to the work memory in step G is stored again as a mask image in the mask memory of the storage device 5. Thus, all the processes are completed.

In addition, the numbers of the live image L ₁ at the time of setting the changed mask image M 'and its change as described above, because it is stored in the storage device 5 as image information, in the image observation from the next, automatically The mask image M is changed to a new mask image M ', and a series of subtraction images with less motion artifact can be displayed.

Further, in FIG. 2, the description has been made assuming that the changed mask image M 'is designated from the image of one frame. However, the present invention is not limited to this, and the image of a plurality of frames is designated by the operator using a buffer. Addition and averaging, and change mask image M '
May be set.

In the above description, the case of displaying a subtraction image of a still image has been described. Hereinafter, the method of displaying a subtraction image of a moving image will be described with reference to FIG. In order to display a moving image, a step F is selected by an operator's key operation in the step of "waiting for input" shown in FIG. Then, in this step F, an image for one heartbeat at the time when the contrast medium has completely flowed out of the examination site is read out from the frame memories 5a to 5n shown in FIG. The image obtained by the averaging by the means 15 is set as the changed mask image M 'after the body movement of the subject, and as shown in FIG. ₁ , the live image L1 at the time of the change is used as shown in FIG. The timing at which the subtraction image is displayed (for example, 30 frames per second) may be controlled by the control unit 8 to display the subtraction image on the monitor 12. At this time, as in the case of the above-described still image, the mask image M at the time of photographing is switched to the changed mask image M ', and a series of subtraction images in which the motion artifact disappears and the blood vessel image remains are obtained. It is displayed on 12 as a moving image.

〔The invention's effect〕

Since the present invention is configured as described above, one image or a plurality of images at the time when the contrast agent has completely flowed out of the examination site in the subject 9 is read from the storage device 5 by the mask image changing means 15 and the subject is read. 9, a new mask image (M ') after body movement is set, the new mask image (M') thus set is stored in the storage device 5, and the new mask image (M ') and the new mask image (M') are stored. By performing the subtraction between the live images L ₁ , L ₂ ,... Read from the storage device 5 using the arithmetic unit 6, the subtraction with reduced motion artifacts can be performed simply by performing the subtraction with the arithmetic unit 6. Images S ₁ ″, S ₂ ″,... Can be obtained. At this time, the new mask image (M ') set above is an image in a state in which the body posture of the subject 9 after the body movement is maintained, so that there is almost no deviation from the subsequent live image, and motion artifact is reduced. It is efficiently removed.
Further, in the angiographic examination, as the new mask image after the body movement of the subject 9, the modified mask image M 'including the image of the phase in which the injection of the contrast medium has been completed and the contrast medium has completely flowed out of the examination site is used. A part of the blood vessel image does not disappear from the subtraction image obtained as in the conventional remasking process. Therefore, the blood vessel image required in the angiography examination is sufficiently displayed, and good diagnostic information can be obtained. In addition, the newly set changed mask image M 'and the number of the live image at the time of the change are stored as image information in the storage device 5, so that the changed mask image M' is set each time in the next image observation. It is possible to immediately observe a subtraction image with little motion artifact without performing any operation. Thus, the time required for image observation can be shortened, and diagnostic performance can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a DSA apparatus according to the present invention, FIG. 2 is an explanatory diagram showing a subtraction process and a mask image changing operation when performing an angiographic examination, and FIG. 3 is a subtraction process and a mask image changing operation. FIG. 4 is a flowchart showing the processing procedure of the operation, and FIG. 4 is an explanatory view showing the conventional subtraction processing and remasking processing. 1 X-ray tube 2 Detector 3 TV camera
4 ... A / D converter, 5 ... Storage device, 6 ... Calculator, 7
... Image display device, 8 ... Control unit, 9 ... Subject, 15 ...
... mask image change means, M ...... mask image, M '...... change the mask image, L ₁ ~L ₄ ...... live image, S ₁ "~S _4" ...... subtraction image.

Claims (1)

(57) [Claims] An X-ray tube for irradiating a subject with X-rays, a detector arranged opposite to the X-ray tube for converting transmitted X-rays of the subject into visible light, and output optics of the detector A television camera that captures images, an A / D converter that digitizes the output signal from this television camera, and a mask image before the contrast agent is injected into the subject by taking in data from this A / D converter And a storage device that stores a plurality of live images having different phases after injection of the contrast agent as a series of images, and an operation of performing subtraction between the specified mask image and the live images having different phases in the storage device. In a digital subtraction angiography apparatus including a device and an image display device for displaying a calculation result of the calculator as a subtraction image, a contrast agent flows from an examination site in a subject from the storage device. A mask image changing means for reading one image or a plurality of images at the completed time phase and setting the image as a new mask image after the body movement of the subject; storing the set new mask image in the storage device; A digital subtraction angiography apparatus wherein subtraction is performed between the new mask image and each live image read from the storage device using the arithmetic unit.