JPS5917330A - X-ray diagnostic apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an X-ray diagnostic device that performs blood vessel imaging using X-rays, and particularly relates to an X-ray diagnostic device that includes a function to detect the timing of imaging the entire blood vessel before and after contrast agent injection. Related to diagnostic equipment.

[Technical background of the invention and its problems]

For example, when performing cardiac catheterization, cerebral angiography, accessory aorta imaging, angiography of limbs, etc., it is necessary to perform t-xfs imaging of the blood vessels, but when performing angiography, t-xfs images cannot be taken as they are; This is done by injecting a contrast medium into a blood vessel and subtracting the image before the contrast medium injection into the blood vessel from the image after the contrast medium is injected into the blood vessel. It is possible to extract only blood vessel images. However, when attempting to diagnose all of the coronary arteries by injecting a contrast agent through the veins of the upper extremities, the injected contrast agent may be injected into the brachial vein, subclavian vein, superior vena cava, right atrium, right heart, pulmonary artery, pulmonary vein, Since the contrast agent circulates through the left atrium, left heart, ascending aorta, and coronary artery, the concentration of contrast agent flowing into the coronary artery is significantly reduced.

Since it is necessary to perform X-ray imaging while this contrast agent remains in the blood vessel, it is necessary to time the X-ray imaging after injection of the contrast agent at a predetermined time. Furthermore, when the contrast medium flows into the coronary artery, the contrast medium is already present in the arteries and veins of the pulmonary field, and these contrast agents overlap with the coronary artery image, making extraction of the coronary artery difficult. Therefore, in order to remove the entire arteriovenous image of the lung field and extract only the coronary artery image, it is necessary to obtain an image at the timing immediately before the contrast agent flows into the coronary artery, and then to obtain an image at the timing immediately before the contrast agent flows into the coronary artery. I needed to subtract it from the existing image. Not only in the extraction of images of coronary arteries, but also in the extraction of images of blood vessels of interest that are targets for other diagnoses, it is necessary to know the timing at which a contrast medium flows into the blood vessels of interest.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to automatically detect the timing of image capture before and after the contrast medium is injected into the blood vessel to be diagnosed, and to All pre-injection images subtracted from the images, only blood vessel images? We provide all X-ray imaging devices that allow extraction.

[Summary of the invention]

In order to achieve the above object, the present invention pays attention to the fact that the value of image data decreases when a contrast medium is injected into a subject, and analyzes changes in image data within a designated area in a time-sharing manner. It is characterized in that when the collected 5 image data exceeds a certain set value, all X-ray exposure is performed to obtain the entire image before contrast agent injection. [Example] Hereinafter, implementation of the present invention Examples will be explained with reference to the drawings. FIG. 1 shows xIw! according to the present invention. It is a block diagram of a diagnostic device. In Figure 1, 11 is an X with a planar spread.
An X-ray source 12 emits a ray beam, and an image sensor 12 detects the X-rays that have passed through the inspection object 13 and converts the X-rays into light.
It is an intensifier and is provided opposite to 11. A television camera 14 is installed below the image intensifier 12 to convert the light from the image intensifier 12 into an electrical signal. The output from the television camera 14 is converted into a digital output by an analog-to-digital converter (hereinafter referred to as an AD converter) 15 and then stored in a memory 16. A monitor 17 displays all the contents of the memory 16 as appropriate. A light pen 18 is used to set a region of interest 7 on the image displayed on the monitor 17. On the other hand, 19 is a high voltage generator that controls the voltage and current of the X-ray source 11. 20 is an X-ray controller, and 21 is a central processing unit. The high-pressure generator 19, the X-ray controller 20, and the central processing unit 21 constitute an X-ray control device 22 that controls the exposure of the X-ray source 11. 26 is an electrocardiograph that counts the heart rate of the subject 13. Electrocardiograph 2
The heart rate of 3 is input to the central processing unit 21. 24
is an image processor that performs data calculation between pixels in a region of interest and subtraction between images. The internal circuit configuration of the image processor 24 will be described later.

Next, in the above configuration, for the purpose of extracting a coronary artery image, a region of interest is set within the left ventricle by utilizing the fact that the contrast agent flows into the coronary artery a short time after it flows into the left ventricle of the heart. An example will be described below. First, before a contrast agent is injected into the subject, an X-ray beam is emitted from the X-ray source 11 toward the subject 13. The image at that time is displayed on the monitor 17. Lightben 18tl - using
A region of interest 25 (FIG. 2) is set within the left ventricle. Second
The figure shows an example in which a horizontal line of limited width in the left ventricle displayed on the monitor 17 is designated as the region of interest. Next, a contrast agent is injected through all upper limb veins, X-rays are exposed at regular intervals, and the images are stored in the memory 16.

Profile of the data (pixel values) of the region of interest specified in Figure 3? Indicated. The vertical axis shows pixel data, and the horizontal axis shows pixel numbers. The graph shown in A1 shows a state in which the contrast medium has not yet been injected into the subject K. The graphs after A2 show the situation in which the contrast medium appears in the blood vessels inside the subject after the contrast medium is injected into the subject. The graphs after A2 show that the contrast medium gradually begins to appear in the blood vessels inside the subject's body, and as a result, the value of each pixel data decreases. Detect changes in the value of pixel data of Jin,
The timing of the inflow of the contrast medium into the region of interest is omniscient, and images before and after the contrast medium injection are collected at that timing.

Next, a method for detecting changes in pixel data will be explained.

In Fig. 4, there is a model in which there is a blood vessel with a diameter of B and an X-ray absorption coefficient of μB in a test object 26 with a thickness of A and an X-ray absorption coefficient of μA, and a contrast agent appears in the blood. If we consider the case where the X-ray absorption coefficient of blood changes from meat to μB', Figure 4A is before the injection of the contrast agent, and the number of 7t X-ray photons NO that is irradiated from the X-ray source 11 is the same as that transmitted by the model Af. Then, the number Nl of X-ray photons after transmission is expressed by the following equation.

N1=Not-μA(A-B)-μBB Similarly, FIG. 4B
Is the number of X-ray photons irradiated from the X-ray source 11 after injection of the contrast medium model B? The number N2 of X-ray photons after transmission is expressed by the following equation.

N1=Not-μA (A-B')-tiB'lJ
In addition, dashi C is the base of natural logarithm and is 1=2.71828.

Therefore, when calculating the difference ΔN between the number of X-ray photons after passing through the subject before and after contrast agent injection, N, , N, we get ΔA' = #,
-N.

=Noc-μA CA-B)-μBB (1-, (-
/7. B'+μB)B) If ΔμB=μB'-μB, then IN = A'o s-μA(A-B)-μ"B(11
−ΔμB B>This equation can be expressed approximately as follows.

ΔH':; N*・ΔμB-B Difference in the number of X-ray photons ΔNf Number of X-ray photons after the contrast medium injection wave passes through the test body N! Dividing by gives the following formula.

That is, dividing by the difference ftNx in the number of X-ray photons gives the amount of change in the X-ray absorption coefficient, regardless of the thickness A of the object to be inspected.

Here, the pixel data (pixel value) D stored in the memory 16 is the total loss of the number A' of X-ray photons by a certain coefficient G. That is, D=GN.

Here, regarding the pixel data D, the data (pixel value) of the t-th pixel of the image before contrast medium injection is kD+'p
After injection of the contrast agent, X-rays are exposed at regular intervals, and Cn-
1) When performed on the i-th pixel in the heart region of the ninth image counted from the image before contrast agent injection,
Since there is a proportional relationship between the data D of each pixel and the number N of X-ray photons, (D--DFLt)/D- corresponds to the amount of change in the X-ray absorption coefficient within the inspected body corresponding to the first pixel. The amount O Here, FIG. 5 shows a graph of the amount of change in the X-ray absorption coefficient within the subject's body based on the above-mentioned calculation formula.

That is, for data of a certain image, ΔD1s/Ds is the difference between the X-ray absorption coefficient in the subject's body before contrast medium injection and the X-ray absorption coefficient in the subject body after a certain period of time has passed after contrast medium injection. Similarly, ΔD*s/D1ii is the difference between the X-ray absorption coefficient in the subject's body before contrast medium injection and the X-ray absorption coefficient in the subject body after a certain period of time has elapsed before contrast medium injection. As can be seen from this figure, as the image number increases, the amount of change in the X-ray absorption coefficient within the examined body increases, which means that the contrast agent gradually flows into the region of interest (left ventricle). This can be seen. In FIG. 6, the horizontal axis represents the image number, and the vertical axis represents the integral value F'f: of the amount of change in the X-ray absorption coefficient within the subject. The integral value of the amount of change in the X-ray absorption coefficient inside the subject shown in Figure 5 is a certain constant threshold M - the value expected when the contrast agent flows into the region of interest - the time corresponding to the image number that exceeds all It is determined that the contrast agent has flowed into the region of interest.

Another method for determining whether the contrast agent has begun to flow into the relevant area is to detect the entire amount of change in the X1fs absorption coefficient within the subject, and to It is also possible to determine that the contrast medium has flowed into the left ventricle. As a result, X
M@ radiation is performed to obtain an image in which no contrast agent is present in the coronary artery, and immediately thereafter, X-ray exposure is performed to obtain all images in which the contrast agent is present.

In addition, by collecting images in synchronization with the electrocardiogram waveform using the electrocardiograph 26, images can be collected after a certain heartbeat from the time when the contrast medium starts to flow into the region of interest using the method described above. Next, a block diagram of the internal circuit configuration of the image processor 24 that performs the above-described operations will be described. In Figure 7,
The image data Dt of the image number 12 pixel number stored in the memory 16 is input to the arithmetic processing units 0 and 31.

On the other hand, the image specifying device 32 determines that the image number is 1 pixel number i.
The image data Dn' is output from the memory 6 and input to the arithmetic processing unit 30. The output of the arithmetic processing unit 60 is input to the arithmetic processing unit #61. Next, the output of the arithmetic processing unit 31 is input to an integrator 33, and the output of the integrator 33 is input to a comparison circuit 34. The threshold value M is input to this comparison circuit 64, and its output is connected to the central processing unit 21 and the image designation device 62 after being changed to image number 1 (rL+1). The operation of the image processor 24 having the above configuration is as follows.

The output Dn' from the memory 6 is subjected to arithmetic processing by the arithmetic processing unit 60, and (DrLi-M) is input to the arithmetic processing unit 31. By the arithmetic processing unit 31, (DnLZ) 7
) /J)j is outputted and divided by the integrator 63 as Σ(DtL'-Dlt) /Dj (D value is outputted) Σ is the sum over all the pixels in the region of interest.

This value and the threshold value M are compared in the comparison circuit 64, and if this value is smaller than the threshold value W, it is input to the image specifying device 32, and the image data number (n, +1) is called again and the same calculation process is performed. Otherwise, if this value is larger than the threshold value M, it is input to the central processing unit 21. Six X-ray exposure signals are issued by the central processing unit 21.

Next, what is the circuit configuration that makes it possible to start collecting all images after a certain heartbeat from the time when the contrast medium starts to flow into the region of interest? This will be explained with reference to FIG. The circuit shown in FIG.
A delay circuit 35 is added to the circuit shown in the figure.

That is, the output from the comparison circuit 34 is input to the central processing unit 21 via the delay circuit 35t. The output from the electrocardiograph 23 is input to the delay circuit 65, and after a delayed heart rate N, the central processing unit 21 issues an X-ray exposure signal. As shown in Figure 6, the X of the test object? This method determines that the contrast agent has flowed into the region of interest when the integrated value of the amount of change in the X-ray absorption coefficient exceeds a certain threshold rc, but if the amount of change in the The method of determining that the contrast agent has flowed into the region of interest when the contrast agent has exceeded the contrast medium can be removed from the integrating circuit 33' in FIGS. Bye.

〔Effect of the invention〕

As described above, according to the present invention, when taking an X-ray image of a blood vessel, the timing at which a contrast medium flows into the blood vessel to be diagnosed is determined by the interest set in advance in the blood flow path of the blood vessel to be diagnosed. It is determined from changes in image data within the region, and images obtained by performing X-ray exposure at this timing are obtained immediately before the contrast agent flows into the region of interest, and images taken thereafter (immediately or after a predetermined heartbeat). When subtracting the contrast-enhanced image, since the timing of both images is close, there will be no large discrepancy between the images, and since images of blood vessels other than the blood vessel can be removed, only the image of the blood vessel in question will be clearly displayed. It is possible to extract.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the Xm diagnosis device according to the present invention, and FIG.
The figure shows the left ventricle of the heart displayed on a monitor, Figure 3 is a graph showing temporal changes in pixel data before and after contrast agent injection, and Figures 4 (B) and (C) are graphs showing the temporal changes in pixel data for calculating cumulative image data. A model diagram of the inspection object. Figure 5 is a graph showing temporal changes in pixel data after arithmetic processing before and after contrast medium injection. Figure 6 is also a graph showing the integral value of image data after arithmetic processing before and after contrast medium injection. 7 is a block diagram inside the image processor shown in FIG. 81, and FIG. 8 is a block diagram inside the image processor showing another embodiment. DESCRIPTION OF SYMBOLS 11... X-ray source, 12... Image intensifier, 16... Inspection object, 14... Television camera, 15... A-D converter, 16.
...Memory, 17...Monitor, 1B...Light Ben, 22...X-ray control device, 26...
Electrocardiograph, 24...Image processor〇Representative patent attorney Kensuke Chika (-1 or 1 person) 22 / ■ Figure 4 (0,

Claims (2)

[Claims] (1) The X-ray image obtained based on Xff1J exposure to the subject and changing over time during the course of contrast agent injection is converted into seven optical images, and after converting the optical image into image data, the contrast agent is In an apparatus that performs full subtraction processing of images before and after injection and displays a series of processed images on a monitor, a region of interest setting means for setting a specific region in the image displayed on the monitor, and a region of interest setting means for setting a specific region of interest in the image displayed on the monitor, and a region of interest setting means for setting a specific region of interest in the image displayed on the monitor, and an image processor that detects a change, processes the detection result, and generates an xIw exposure signal for obtaining an image immediately before contrast agent injection when the calculation result reaches a predetermined value. Line diagnostic equipment. (2) The image processor sequentially calculates the difference between the first image data and the image data obtained afterward using the first image data as a reference among the plurality of image data during the course of contrast agent injection, and divides the entire difference value by the first image data. and sequentially integrates the division results, and when the integrated value reaches a predetermined value, generates an X-ray exposure signal for obtaining an image immediately before contrast agent injection. X-ray diagnostic device 0 described in item 1