JPS5911838A - X-ray photographic system - 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 The invention is directed to digital subtraction angiography for performing angiography.
tion angiography).

Angiography, which images the running state and blood dynamics of blood vessels in the body, has become an essential method for the diagnosis of diseases. 1. Compared to the method that requires or the method of injecting contrast agent from the artery. This is a simple method that requires less meditation.

Digital subtraction angiography is
This method digitally subtracts the X-ray image when no contrast agent is present from the X-ray image when there is a contrast agent in the target area, and performs angiography as a distribution image of only the contrast agent. For example, When 30 to 40 parts of 76% urografin is injected as a contrast agent through the cubital vein at a rate of 10 to 13 cc per second, the contrast agent arrives at the abdominal aorta after 13 heartbeats.Therefore, before arrival, the X-ray image of the abdomen is masked as an image. Approximately 12 seconds have passed since the contrast medium was injected, and once every second from the time just before the contrast medium arrives,
Approximately 10 X-ray images were taken, and subtraction with the mass sparing images revealed the abdominal aorta.

Nearby angiography can be performed. There are similar people.

The basic idea of this method is that the distribution of the contrast agent can be obtained by subtracting the entire mask image from the X-ray image of the contrast agent, and it is assumed that both images are the same except for the contrast agent. . Therefore, it is important to avoid the effects of patient movement, movement of organs due to breathing and movement of intestinal gas, and pulsation of blood vessels in order to obtain high-quality images. Since the imaging time is about 15 to 25 seconds, patient movement and respiratory organ movement can be avoided by immobilizing the patient and stopping breathing, and movement of loose intestinal gas can be avoided by using antispasmodics or by degassing. Countermeasures are being taken through pre-treatment. However, it is difficult to remove the influence of vascular pulsation, and motion artifacts
CT) is the cause of image quality deterioration.

Therefore, an object of the present invention is to provide an X-ray imaging method in digital subtraction angiography that eliminates motion artifacts caused by movement of blood vessels and changes in shape due to pulsations, and obtains high-quality images.

In order to achieve this objective, in the present invention, the pulsation period of blood vessels is measured by the electrocardiogram period, and a stable phase of blood vessel fluctuation is extracted from the concentration correlation value between fluoroscopic images of the same phase. Image after injection
artifact 'ff: Characterized by removal.

FIG. 1 schematically shows the state of blood vessel pulsation.

When the blood pumped from the heart passes periodically with the heartbeat cycle T, the blood vessel type is stable, the movement is slow, and the influence of blurring of the imaging time due to fluctuations in the blood pumping cycle of the heart is less affected by phase P1. This is a method of searching based on image correlation values.

At phase P1, the correlation 1iN of the perspective image is large, but at phase P1
In case 2, the movement of the blood vessels is fast and the time-related fluctuations are large, so the correlation value is small, and even at the distorted phase P, the blood vessel type is unstable, so the correlation value is small.

Hereinafter, the present invention will be explained in detail based on examples. Second
The figure shows the overall configuration of a digital subtraction angiography apparatus using the inventive method. Electrocardiograph 3
, R detection circuit 4, computer 7, image memory 8, and correlator 9, the components are a general digital subtraction angiography tube. The electrocardiograph 3, computer 7, image memory 8, and correlator 9 are existing products, R
As the detection target circuit 4, a part of an existing electrocardiogram automatic analysis device can be used.

Next, the operation will be explained. Computer 7 controls X-ray irradiation
Since this is mainly carried out, the operation will be explained in detail with reference to FIG. 3, which is a flowchart.

After setting the maximum value f m&X of the correlation coefficient (described later) and the maximum value of the number of repetitions (described later) to O in step 30, first, the electrocardiograph
The terminals are brought into contact with the entire human body and an electrocardiogram is collected. This electrocardiogram is input to the R detection circuit 4, the R wave is automatically detected, and its timing pulse is sent from the R detection circuit 4 to the computer 7. Collect an electrocardiogram for about 1 to 2 minutes, measure the time interval of timing pulses input to the computer 7, and calculate the average value t (step 31).
.

The electrocardiogram is divided into R8 wave and R wave average interval time tin phases, and a fluoroscopic image for each phase is written into the image memory 8 via the computer 7. Generally, n=10
It is about seconds. This processing is executed by sending a signal from the R detection circuit 4 to the computer 7, and the computer 7 receiving a digitized signal of the perspective image (step 32). Repeat step 32 n times to
When the fluoroscopic images are stored in the image memory 8, they are taken into the next R-wave viewer 7 (step 33).

The captured fluoroscopic image is transferred to the correlator 9, and a correlation value r is calculated using the following equation with the fluoroscopic image B acquired at the same two phases, which has already been stored in the image memory 7 (step 3).
4).

Xlj: pixel density y at the position (1°j) of the perspective image in the image memory 7 - pixel density n2 at the position (i, J) of the perspective image sent directly to the correlator 9: number of pixels in the perspective image Based on this calculation result, the values of rmllX and M are updated (step 35). Steps 33 to 35 are repeated n times to calculate n correlation values corresponding to n phases, and the phase waits for the maximum correlation value. This phase is used to perform photographing similar to conventional digital subtraction geography (steps 36 and 37).Subtraction of the photographed image (step 38) is performed.

The binding is observed using the TV monitor 10 or camera 11 as in the conventional case.

As explained above, according to the present invention, by searching for a phase in which the vascular pulsation at the imaging site is stable and has little displacement, and by performing X-ray imaging in synchronization with this phase, the motion artifact of the pulsation is detected. It is possible to obtain digital subtraction angiography images with less noise.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the state of blood vessel pulsation, Figure 2 is an overall configuration diagram of a digital subtraction angiography apparatus using the method of the present invention, and Figure 3 is a diagram showing the system of the present invention under computer control. It is a flowchart which shows the processing procedure when implementing. Agent: Patent Attorney Toshiyuki Usuda, “-2 Part 3 (2) Continued from page 1 ■Applicant: Hitachi Medical Co., Ltd., 1-14 Shimome, Uchikanda, Chiyoda-ku, Tokyo

Claims (1)

[Claims] 1. X-ray image after contrast agent is injected into the blood vessel and X-ray before injection
In a digital subtraction angiography device that measures blood dynamics by image subtraction of line images, the time period of vascular pulsation is measured from the patient's electrocardiogram waveform, and the concentration correlation between fluoroscopic images taken at the same phase of this period is determined. An X-ray imaging method characterized by extracting a stable phase of blood vessel fluctuations from the values and performing X-ray imaging of a predetermined part of the body in synchronization with the phase.