JPH0654256A - Digital subtraction angiography device - Google Patents

Abstract

PURPOSE:To improve the operability of a digital subtraction angiography device by catching accurately the arriving timing of a contrast medium at a photographing place and carrying out the photographing with no waste. CONSTITUTION:A contrast medium is injected into a body 9 to be examined when the body 9 is examined by fluoroscopy and then converted into the video signals by a TV camera 3. These video signals are inputted to a differentiating circuit 15 to undergo the second differentiation. The video signals of the contrast medium part have the sudden changes and the rising part of the video signal is detected when the second differentiation is applied to the contrast medium part. Then the rising part of the video signal is compared with the value by a threshold value discriminating circuit 16 and when the rising part exceeds the set value, it is decided that contrast medium reaches the photographing place. Then a control signal S6 is sent to a control circuit 8. Thus it is possible to confirm whether the contrast medium has reached the photographing place or not by differentiating the video signal sent from the camera 3 by the circuit 15 and then comparing the differentiation value with the set value of the circuit 16. Therefore there is no image existed before the arrival of the contrast medium or when the contrast medium passed through. Then the operability is improved for a digital subtraction ungeography device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital subtraction angiography apparatus (hereinafter referred to as a DSA apparatus) for obtaining a blood vessel image by subtracting X-ray images before and after arrival of a contrast agent, and particularly to a target site of the contrast agent. A technique for measuring arrival timing.

[0002]

2. Description of the Related Art A DSA apparatus injects a contrast agent from an arm or leg of a subject and subtracts an image in which the contrast agent is injected and an image in which the contrast agent is not injected to display only a blood vessel image. is there.

In a conventional DSA apparatus, as shown in FIG. I. 2 detects and converts into an optical image, this optical image is converted into a video signal through the distributor 14 and the television camera 3, and the digital video signal converted by the A / D converter 4 is stored in the storage device 5 as an image. Remember. The storage device 5 stores an image containing a contrast agent and an image not containing a contrast agent.
And the subtraction is performed, and the difference is displayed on the image display device 7 and stored in the storage device 5.

[0004]

In the above-mentioned conventional apparatus, in order to capture an image in which the contrast agent has flowed into the imaged site, the operator can capture the image at an appropriate time after injecting the contrast agent, or take a fluoroscopic image. I was taking an image when the contrast agent appeared while looking. However, in such a method, there is an individual difference in the arrival time of the contrast agent of about 3 to 8 seconds, and therefore there is a possibility that an image is taken before the contrast agent reaches the imaging site or after the contrast agent has passed. However, there were cases where a large number of unnecessary images were taken to obtain the desired image.

Therefore, an object of the present invention is to improve the operability by accurately capturing the arrival timing of the contrast agent at the imaging site and performing imaging without waste.

[0006]

In order to achieve the above object, an X-ray tube for irradiating a subject with X-rays, and an X-ray image of the subject, which is arranged so as to face the X-ray tube, are converted into an optical image. A detector,
A television camera that captures the optical image, an A / D converter that converts an output signal of the television camera into a digital signal, a storage device that stores digitalized data as a series of images, and a storage device in the storage device. In a DSA device having an arithmetic circuit for performing subtraction between two images specified by, an image display device for displaying the subtracted image, and a control circuit for controlling each of the above components,
It is provided with a differentiating circuit for differentiating the output video signal of the television camera and a threshold discriminating circuit for comparing the output signal of the differentiating circuit with a set value.

[0007]

The X-ray fluoroscopic image signal is second-order differentiated by the differentiating circuit. When the contrast agent reaches this fluoroscopic region, the video signal shows a sudden change. When this portion is differentiated, a differential signal having a peak near the rising edge of the video signal is output. Then, this output differential signal is compared with the set value set by the threshold value discrimination circuit, and when it exceeds the set value, the arrival signal is output to the control circuit and the arrival timing of the contrast agent can be recognized. As a result, unnecessary images are not taken and operability is improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing a configuration of the present invention, and FIG. 2 is a diagram showing an output signal of a video signal and a differentiating circuit, and an output signal of a threshold discriminating circuit. 1 is an X-ray tube, 2 is an I.D. for converting an X-ray transmitted through the subject 9 into an optical image. I. 3 is I.
I. A TV camera that converts the optical image of 2 into a video signal, 4
Is an A / D that digitizes the video signal of the TV camera 3.
A converter, 5 is a storage device for storing a digitized video signal, 6 is a calculation circuit for subtracting an image with and without a contrast agent stored in the storage device, 7 is an enhancement circuit 10, D / An image display device including an A converter and a monitor 12, 8 is a control circuit for controlling the operation of each unit of the DSA device, and 9 is a subject.

Reference numeral 10 is an enhance circuit for enhancing the contrast of the image subtracted (differential operation) by the arithmetic circuit 6, 11 is a D / A converter for analogizing the output image of the enhance circuit 10, and 12 is an analog image. , 13 is a top plate, 14 is an I.D. I. Distributor 15 for guiding the optical image of 2 to TV camera 3 is A
A differentiating circuit for differentiating the video signal digitized by the / D converter 4, 16 is a threshold discriminating circuit for comparing the output signal of the differentiating circuit 15 with a set value, and 17 is an X for applying a high voltage to the X-ray tube 1. A ray generator, 18 is an X-ray controller that controls a high voltage applied to the X-ray tube 1.

S1 is an X-ray controller 18 for performing X-ray irradiation.
, A control signal for controlling the input of the optical image to the television camera 3, a control signal for designating the storage location of the video signal, and a designation of two images to be computed by the computing circuit 6. Control signal for controlling, S5 is a control signal for determining the set value of the threshold discriminating circuit 16 and controlling the operation of the threshold discriminating circuit 16, S6 is a control signal generated when the differential signal exceeds the set value in the threshold discriminating circuit 16, S7 is a control signal for controlling the enhancement circuit 10.

Next, the operation of this embodiment will be described. First, an image (mask image) in which a contrast agent is not injected is first taken.
The X-ray controller 18 is controlled by the control signal S1 from the control circuit 8.
Is operated to determine the tube voltage and the tube current applied to the X-ray tube 1, and the object 9 is transmitted therethrough. I. It is detected in 2 and converted into an optical image. This optical image is guided to the television camera 3 by the distributor 14, and a video signal is output by the control signal S2 of the control circuit 8. Video signal is A
It is inputted to the / D converter 4 and digitized, and one of the frame memories 5a to 5n is selected and stored by the control signal S3 of the control circuit 8.

Then, an image (live image) in which the contrast agent is injected is photographed. In the imaging operation, the X-ray tube is generated by the control signal S1 of the control circuit 8 as in the above, and the I.I. I. 2 The optical image is converted into a video signal by the TV camera 3 and a digital video signal by the A / D converter 4. Then, a contrast agent is injected into the subject 9 during this fluoroscopic operation, and when this contrast agent is injected from the arm or leg of the subject 9, it reaches the imaging site in a few seconds. This fluoroscopic image signal is input to the differentiating circuit 15 and secondarily differentiated. The video signal of the contrast agent portion changes abruptly, and when this portion is second-order differentiated, the rising portion of the video signal is detected and compared with the set value set by the threshold value discrimination circuit 16. If this value is exceeded, the contrast is increased. The control signal S6 is transmitted to the control circuit 8 when it is determined that the agent has reached the imaging region. The control circuit 8 receives the control signal S6 and stores it in one of the frame memories 5a to 5n according to the control signal S3.

When the mask image and the live image are stored in the memory device 5, the mask image and the live image are designated by the control signal S4, and the subtraction is performed by the arithmetic circuit 6. Then, an image of only the contrast agent portion, that is, a blood vessel image is obtained, and the blood vessel image is stored in the storage device 5. When displaying this blood vessel image as an image, the blood vessel image is input to the enhancement circuit 10 to perform image processing for enhancing the contrast, and the image-processed signal is converted into a video signal by the D / A converter 11. Display on the monitor 12.

The differentiating circuit 15 and the threshold discriminating circuit 16 are also provided.
The operation will be described with reference to FIG. 2A is a video signal from the A / D converter 4, FIG. 2B is a secondary differential value of the video signal of FIG. 2A, and FIG. 2C is generated when the secondary differential value exceeds a set value. This is the arrival signal. A few seconds after the contrast agent is injected into the subject, the contrast agent reaches the imaging site. The video signal when the contrast agent arrives changes abruptly as shown in (a). Then, this video signal is second-order differentiated by the differentiating circuit 15, and if there is a sudden change in the video signal, the second-order differential value also changes. This second derivative shows a waveform having a peak at the rising portion of the image signal of the contrast agent portion. This second derivative value is compared with the set value, and when the value becomes larger than the set value, the arrival signal is transmitted to the control circuit 8.

As a result, the differentiating circuit 15 and the threshold discriminating circuit 16 detect the image at which the contrast agent has arrived, so that the timing of arrival can be recognized and unnecessary images can be eliminated.

[0016]

According to the present invention, the presence or absence of the contrast agent is confirmed by differentiating the video signal from the television camera by the differentiating circuit and comparing the differential value with the set value of the threshold discriminating circuit. Therefore, an image before the contrast agent arrives or when the contrast agent has passed has disappeared, and the operability is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention.

FIG. 2 is a diagram showing output signals of a differentiating circuit and a threshold discriminating circuit for a video signal.

FIG. 3 is a block diagram showing a conventional DSA device.

[Explanation of symbols]

 1 X-ray tube 2 I. I. 3 TV camera 4 A / D converter 5 Storage device 6 Arithmetic circuit 7 Image display device 8 Control circuit 9 Specimen 10 Enhance circuit 11 D / A converter 12 Monitor 13 Top plate 14 Distributor 15 Differentiation circuit 16 Threshold discriminating circuit 17 X Line generator 18 X-ray controller

Claims (1)

[Claims] 1. An X-ray tube for irradiating a subject with X-rays, and this X-ray tube.
A detector which is arranged to face the X-ray tube and which converts an X-ray image of the subject into an optical image, a television camera which captures the optical image, and an A / which converts an output signal of the television camera into a digital signal
A D converter, a storage device for storing digital signal data as a series of images, an arithmetic circuit for performing subtraction between two designated images in the storage device, and an image display device for displaying the subtracted image , A digital circuit having a control circuit for controlling each of the above components
In the subtraction angiography device, a differentiation circuit that differentiates the output video signal of the television camera,
A digital subtraction angiography apparatus comprising a threshold value discrimination circuit for comparing an output signal of the differentiating circuit with a set value.