JP2770192B2 - X-ray digital subtraction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial application field The present invention is used in the field of X-ray imaging.

The present invention relates to an X-ray digital subtraction apparatus, and more particularly to an X-ray digital subtraction angiography (DSA or angiography technique), which is used particularly when a wide area such as a lower limb or a whole body is imaged in a single unit of imaging. Is done.

(B) Conventional technology When photographing a wide area such as a lower limb in one photographing,
The operator looks at the image displayed on the TV monitor, observes the flow of the contrast agent, and moves the table on which the subject is placed manually or by a switch operation while following the flow of the contrast agent.

(C) Problems to be Solved by the Invention Since such a table is moved while watching the TV monitor, the operation is troublesome for the operator. Further, in the case of completely manual movement, exposure of the operator to X-rays becomes a problem.

An object of the present invention is to provide an X-ray angiography in a relatively large area to be inspected, which is executed by automatic control movement of a table.
It is to provide a line digital subtraction device.

(D) Means for Solving the Problems The object described above is to set the imaging range to be a portion extending over the unit length of the table and the edge length adjacent thereto, and to set the diameter of the image intensifier (II), the X-ray tube , The distance between the II, the X-ray tube, and the distance between the subjects are set by calculation on the TV monitor to set the region of interest corresponding to the respective length portion and the outside of the region of interest on the TV monitor. Means for displaying such a portion to be inspected, a frame memory for taking a mask image for each unit length and storing them,
A time difference calculating means between the live images captured by injecting the contrast agent, a contrast agent tip image tracking and monitoring means for detecting the highest density of the time difference image outside the region of interest on the TV monitor screen, A table movement control means for automatically moving a table on which a subject is placed in the longitudinal direction by a unit length each time a detection is performed, and a mask image is read from the frame memory, updated and read live every time such a table moves. This is achieved by providing arithmetic means for obtaining a subtraction image between images.

(E) Function The CPU recognizes the position of the front end image of the contrast agent from the obtained digital X-ray image, and the CPU moves the table movement controller to the table movement controller so that the front end image position of the contrast agent always falls within the specified range on the screen. A timing command is issued, and the table moves automatically.

As described above, since the table automatically moves, the photographing is performed without any trouble of the operator. Therefore, the operator is not exposed to X-rays for moving the table.

(F) Embodiment Preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration block diagram showing one embodiment.

This embodiment will be described for the case of performing DSA of the lower limb.

The operator can use the input device 17 such as a keyboard in advance.
II (Image Intensifier) 3 Diameter (II
Size), the distance (FI.D.) between the X-ray tubes 2 and II3, and the distance (FOD) between the X-ray tube 2 and the subject 1 are input. Further, the operator designates in advance a region (for example, a hatched portion on the CRT screen in FIG. 2) for observing the front end image of the contrast agent on the screen from the input device 17, and inputs the II size, FID, and FO previously input.
From the parameters of D., the CPU 16 calculates the unit length TYa of the table 19 on which the subject is placed and the edge length TYb adjacent thereto with respect to the lengths CYa and CYb on the Y axis in FIG. .

The body axis of the subject 1 is set to be parallel to the Y axis on the screen (exemplified in FIG. 2), and the table 19 can be moved in parallel to the Y axis. In addition,
The lower part of the screen shown in FIG. 2 corresponds to the lower extremity direction of the subject 1.

First, the DSA system according to the present invention captures a mask image. Initially, the table 19 is set so that the imaging range is the upper thigh. In this state, the first mask image is photographed, and then the table 19 is moved to the left in FIG. 1 by the distance TYa via the table controller 18 by a command from the CPU 16 to photograph the second mask image. I do.

In this way, a plurality of mask images (M1 to Mn in FIG. 3) are successively photographed until the photographing range reaches the lower extremity.

Regarding the mask image shooting, the X-ray transmitted through the subject 1 is visualized by II3, passes through the TV camera 4 and CCU (camera control unit) 5, is A / D converted by the A / D converter 6, and It is stored in the frame memories 7.

Next, the table 19 is moved by the table controller 18 to an initial position where the first mask image is taken. Therefore,
The contrast agent is injected, and the shooting of a live image starts. The live image is A / D converted by the A / D converter 6 in the same way as when the mask image was taken.
After the conversion, it is input to the frame memory 8a,
Is subtracted from the mask image stored in the frame memory 7 by
This difference image is input to the frame memory 11, and thereafter,
The data is output to the TV monitor through the D / A converter 13 or stored on the magnetic disk 14.

When the live image L1 in FIG. 3 is taken, the mask image read from the frame memory 7 is M1, and the arithmetic unit 9 performs the processing of S1 = L1−M1. Further, the live image L1 is also stored in the frame memory 8b.

In the next X-ray exposure, a live image L2 is photographed, and the arithmetic unit 9 performs processing of S2 = L2−M1, and the live image L2 is combined with the live image L1 stored in the frame memory 8b and the arithmetic unit.
The value is subtracted by 10 and stored in the live image time difference image frame memory 12.

This difference image is input to the image processing memory 15, and the point indicating the highest density in this image is detected. The point indicating the highest density is regarded as the tip image of the contrast agent moving in the body, and if the point indicating the highest density is within the hatched portion in FIG.
If the CPU 19 does not move and goes out of the shaded area, the CPU 16 issues a table movement command for the distance TYa via the table controller 18, and the table 19 moves by that distance. When the table 19 moves and the next X-ray exposure is performed, the mask image extracted from the frame memory 7 is updated.

For example, in FIG. 3, the mask image to be subtracted is M1 at the time of live images L1 to L3, but the mask image is M2 at the time of live images L4 to L7. This operation is repeated until the imaging range reaches the lower extremity.

(G) Effect According to the present invention, a single injection of a contrast agent can automatically obtain a DSA image of a wide area, and does not cause the operator to be exposed to X-rays.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a view showing an example of a CRT screen, and FIG. Reference numeral 7 denotes a mask image frame memory, 8 denotes a live image frame memory, 11 denotes a DSA image frame memory, 12 denotes a live image time difference image frame memory, 16 denotes a CPU, and 19 denotes a table.

Claims (1)

(57) [Claims] 1. A photographing range is defined as a portion corresponding to a unit length (TYa) of a table and an edge length (TYb) adjacent thereto.
Image intensifier (II) diameter, X-ray tube,
A region of interest (CYa) and a region outside the region of interest (CYb) corresponding to the respective lengths are set on a TV monitor by calculation based on the parameters of the distance between II, the X-ray tube, and the distance between subjects. Means for displaying the portion to be inspected corresponding to the photographing range, a frame memory for photographing and storing mask images for each unit length, and calculating a time difference between live images photographed by injecting a contrast agent. Means, a contrast agent tip image tracking and monitoring means for detecting the maximum density of the time difference image outside the region of interest (CYb) on the TV monitor screen, and a longitudinal direction by a unit length (TYa) for each detection. Table movement control means for automatically moving a table on which a subject is placed, and arithmetic means for reading and updating a mask image from the frame memory every time the table is moved to obtain a subtraction image between live images Characterized in that it comprises the, X-rays digital subtraction device.