JPH02202183A - Digital subtraction angiography device - Google Patents

Abstract

PURPOSE:To obtain the digital subtraction angiography image with high space resolution by enlarging a mask image read from an image storing means, which stores a mask image before the injection of an angiographic agent for one motion cycle at least, and subtracting the enlarged mask image from a live picture, which is obtained after the angiographic agent is injected. CONSTITUTION:Before the angiographic agent is injected, the mask image is taken into a frame memory 22 and next, the angiographic agent is injected. Then, the live image is obtained. The mask image coincident with the phase of the obtained live image is searched from the frame memory 22 and read and this read mask image is enlarged by an image enlarger 23. In an image subtracter 24, the mask image, whose matrix size is arranged with that of the live image is subtracted from the live image. Then, a signal after this subtraction is passed through a D/A converter 25, returned to an analog signal and after that, the signal is sent to an image monitor device 26. Thus, the digital subtraction angiography image with high space resolution can be obtained with maintaining the accuracy of phase matching between the live image and mask image.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a digital subtraction angiography device, which is particularly suitable for performing digital subtraction angiography on organs that undergo periodic motion such as the heart, or areas of organs that are affected by periodic motion such as respiratory motion. Regarding equipment.

[Conventional technology]

When digital subtraction angiography is performed on an organ region that undergoes periodic motion, such as the heart, the X-ray transmission images will differ for each phase due to the movement. Some effort is needed. Conventionally, 1
A large number of mask images are obtained for a period longer than the period, and the mask images in phase are subtracted from the live image obtained after contrast agent injection.

[Problem to be solved by the invention]

However, in order to accurately match the phases of these images when calculating the mask image before contrast medium injection from the live image after contrast medium injection, it is necessary to perform X-ray imaging in a mode with a high sampling rate. In order to do so, the image matrix size had to be reduced, which resulted in a problem of poor spatial resolution. SUMMARY OF THE INVENTION An object of the present invention is to provide a digital subtraction angiography apparatus that can obtain a subtraction image with high precision in phase alignment between a mask image and a live image, and with high spatial resolution.

[Means to solve the problem]

In order to achieve the above object, the digital subtraction angiography apparatus according to the present invention includes an X&iTV imaging means that can be switched between a high resolution mode and a high sampling rate mode, and a mask image in the high sampling rate mode before injection of a contrast agent. image storage means for storing one motion cycle; image enlargement means for enlarging the mask image read from the image storage means to match the matrix size of the image in high resolution mode; and high resolution obtained after contrast agent injection. Means is provided for subtracting, from the live image of the mode, a mask image read out from the image storage means and enlarged by the image enlarging means as having a phase corresponding to the live image in periodic motion.

[For use]

Since the mask image before contrast medium injection is taken at a high sampling rate, the matrix size of the image must be small, and the mask image with poor spatial resolution is stored. On the other hand, a live image after contrast agent injection is taken at a low sampling rate, resulting in an image with high spatial resolution, that is, a large matrix size. Here, the mask image whose phase matches the live image is read out, the image is enlarged, and this is subtracted from the live image. However, the image is enlarged simply to match the size of the image; Since the spatial resolution of the subtraction is not improved, the mask image used for subtraction still has poor spatial resolution. However, since the mask image does not include blood vessel images, there is no problem even if the spatial resolution is somewhat inferior. This is because the blood vessel image remains even after the subtraction and is displayed. On the other hand, since the mask image has such a low spatial resolution, its temporal resolution can be increased, and an image with a phase closer to that of the live image can be obtained. As a result, the accuracy of phase alignment between the live image and the mask image can be improved. As a result, it is possible to obtain a digital subtraction angiography image with high spatial resolution while maintaining the precision of phase alignment between the live image and the mask image. Therefore, it is particularly effective for coronary angiography, which requires high spatial resolution but not so much temporal resolution.

【Example】

Next, an embodiment of the present invention will be described with reference to the drawings. In this example, it is assumed that digital subtraction angiography is performed near the heart. The electrocardiogram of the subject (not shown) is measured by the electrocardiogram monitor device 4, and the measurement signal is sent to the controller 27 of the image processing device 2.
sent to. The controller 27 controls the X-ray irradiation device 3 according to the cardiac phase and also controls the X-ray TV camera 1 to obtain a video signal of an X-ray transmission image of the subject according to the cardiac phase. . This video signal is converted into a digital signal by an A/D converter 21 and then stored in a frame memory 22 which is controlled by a controller 27 according to the cardiac phase. Here, the X, l1 TV camera 1 has 1051 scanning lines,
It is assumed that it is possible to switch between a high resolution mode with a frame rate of 7.5/sec and a high sampling rate mode with 525 scanning lines and a frame rate of 30/sec, and the switching control is performed by the controller 27. shall be. First, before injection of a contrast medium, a large number of mask images are captured into the frame memory 22 as follows. At this time, Con1~
The X-ray TV camera 1 is set in a high sampling rate mode by the roller 27, and pulsed X-rays are emitted from the X-ray irradiation device 3 to obtain a video signal of an X-ray transmission image from the X-ray TV right camera. This video signal is sent to the A/D converter 2]
512 by sending it to the frame memory 22 through
Images having a matrix size of ×512 are stored in the frame memory 22 at a rate of 30 images per second. In this way, mask images for one heartbeat (30 mask images if the heartbeat rate is 60 beats/min) are captured into the frame memory 22. Next, a contrast agent is injected to obtain a live image. At this time, the controller 27 sets the X-ray TV camera 1 to high-resolution mode, and the X-ray exposure device is activated! X! A video signal of an X-ray transmission image is obtained from the ITV camera 1. Furthermore, since the A/D converter 21 is set to correspond to the high resolution mode at this time, from this video signal, the A/D converter 21 generates 7.5 high resolution live images with a matrix size of 1024 x 1024. /second. This live image video signal is sequentially sent to an image subtracter 24. When one live image is obtained in this way, a mask image that matches the phase of the obtained live image is searched from the frame memory 22 and read out. This read mask image has a matrix size of 512 x 512, but it is enlarged by the image enlarger 23 to 1024 x 10.
24 matrix size image. Specifically 1
This image enlargement is accomplished by converting one pixel into four pixels. In the image subtractor 24, the mask image whose 71-rix size is aligned with that of the live image is subtracted from the live image. The signal after this subtraction is D
The signal is returned to an analog signal via the /A converter 25 and then sent to the image monitor device 26. In this way, the mask images whose cardiac phases match those of the live images sequentially obtained after the contrast agent injection are subtracted, and as a result, an image in which only blood vessel images represented by the contrast agent are extracted is displayed on the image monitor 26. will be displayed by. In addition, although the case where digital subtraction angiography is performed in the vicinity of the heart has been described above, it is also applicable to the case where digital subtraction angiography is performed in a region affected by periodic motion such as respiratory motion. In areas affected by respiratory motion, a respiratory monitor device is used instead of the electrocardiogram monitor device 4, and the operation is controlled according to the respiratory detection signal to perform digital subtraction angiography in accordance with the phase of the respiratory motion. Can be done.

【Effect of the invention】

According to the digital subtraction 3 angiography apparatus of the present invention, high spatial resolution digital subtraction 3 Angiographic images can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention. 1... X-ray TV camera, 2... Image processing device, 3.
...X-ray irradiation device, 4...electrocardiogram monitor device, 21.
・・A/D converter, 22 ・・Frame memory, 23・
...Image enlarger, 24...Image subtractor, 25...D
/A converter, 26... image monitor device.

Claims (1)

[Claims] (1) X-ray TV imaging means capable of switching between a high resolution mode and a high sampling rate mode, an image storage means for storing a mask image in the high sampling rate mode before contrast agent injection for at least one movement cycle, and this image storage Image enlarging means enlarges the mask image read out from the means to match the matrix size of the image in high resolution mode, and from the live image in high resolution mode obtained after contrast agent injection, this live image and the phase in periodic motion are calculated. and means for subtracting a mask image read out from the image storage means and enlarged by the image enlargement means as a corresponding image.