JPH0693888B2 - X-ray CT system - Google Patents

Description

TECHNICAL FIELD The present invention relates to an X-ray CT apparatus, and more particularly to an X-ray CT apparatus suitable for positioning using a fluoroscopic image.

[Conventional technology]

The X-ray CT apparatus has a function of obtaining a tomographic image of the subject. X-ray
Some CT devices have a function of obtaining a fluoroscopic image as well as a tomographic image. Although the fluoroscopic image itself is used as diagnostic information, it is often used to identify the site from which a CT tomographic image is obtained.

That is, first, the subject is moved to obtain a fluoroscopic image. next,
This perspective image is displayed as a screen. An arbitrary position of the perspective image on this screen is designated and a cutting position for obtaining a CT tomographic image is designated. Then, the designated position is displayed as one straight line on the screen.

[Problems to be solved by the invention]

In this conventional example, the cutting position is indicated by one straight line in the perspective image. Here, the slice width (cutting width) of the X-ray CT apparatus is 1 mm to 10 mm, and the size of one pixel of the display device for displaying a fluoroscopic image is 0.5 mm to 1 mm. Therefore,
One straight line in the perspective image is displayed with a width of 0.5 mm to 1 mm, and a slice width of 1 mm to 10 mm cannot be displayed.

The purpose of the present invention is to make it possible to accurately display the slice width CT
The present invention provides a fault device.

[Means for solving problems]

The present invention specifies the center position of cutting, determines the slice width with respect to this center position, converts the center position and the slice width into an address on the display screen of the perspective image, and superimposes the center position on the perspective image according to this address. It was decided to display the position and the position of the slice width around it.

[Action]

By inputting the slice center position (or slice center position and slice width) from the outside, it is possible to automatically display the slice width position where the slice image is obtained by superimposing the slice image on the perspective image.

〔Example〕

FIG. 1 shows an embodiment of the CT apparatus of the present invention. The X-ray source 1 and the X-ray detector 2 are located at opposite positions across the measurement space of the rotating frame 1A.
To provide. The X-ray source 1 is a fan-shaped X-ray source, and the X-ray detector 2 is a multi-channel type detector.

The bed 3 is movable in the direction of the arrow, and the subject is mounted on it. The control circuit 9 controls the movement of the bed 3.

The computer 4 takes in the fluoroscopic X-ray detection values of the multi-channel X-ray detector 2 and obtains a fluoroscopic image and an X-ray CT image. First, a fluoroscopic image is obtained, this fluoroscopic image is displayed on the display device 6, then the slice width is displayed, and then a CT tomographic image is obtained.

The memory 5 stores a fluoroscopic image and an X-ray CT image. The display device 6 displays the contents of the memory 5.

The input device 7 specifies the cutting center position and the slice width.

The position calculation device 8 takes in the cutting center position and the slice width, which are inputs from the input device 7, converts them into addresses on the display screen, and executes control command generation processing to the control circuit 9.

The input device 7 also inputs the perspective position.

The process of obtaining a perspective image is as follows.

(I) Place the subject on the bed.

(Ii) The perspective position is input from the input device 7.

(Iii) The position calculation circuit 8 obtains the moving distance (moving width) of the bed from the perspective position, and controls the bed 3 to move (forward or backward) by the width of this moving distance. In this movement control, the bed 3 is positioned at the start position in advance.

(Iv) The bed 3 is moved in units of a predetermined pitch. X-rays are emitted from the X-ray source 1 at each pitch position, and the transmitted X-rays of the subject are received by the X-ray detector 2.

(V) The computer 4 takes in the detected value of the X-ray detector 2 and performs the fluoroscopic image data processing to obtain the fluoroscopic image data. The perspective image data is stored in the memory 5.

(Vi) The display device 6 reads out and displays the fluoroscopic image data in the memory 5 by the raster scan method.

The process of obtaining a CT tomographic image is as follows.

(I) Place the subject on the bed.

(Ii) The CT tomographic region is designated by an instruction from the control device 9, and the bed 3 moves to the designated position with the subject placed on it.

(Iii) When the designated position is reached, the bed 3 is fixed. Next, while rotating the frame 1A, X-rays are emitted from the X-ray source 1 at a predetermined pitch.

(Iv) The X-ray detector 2 detects the transmitted X-ray for each pitch position.

(V) The computer 4 takes in the detection value of the X-ray detector 2 and performs a re-image reconstruction process to obtain CT tomographic image data. This CT tomographic image data is stored in the memory 5, and the display device 6 reads it and displays the CT tomographic image on the screen.

In the above description, the X-ray source 1 and the X-ray detector 2 are fixed when obtaining the fluoroscopic image, but the fluoroscopic image can be obtained over a wide range by moving the X-ray source 1 and the X-ray detector 2 within a certain range.

A display example of a perspective image is shown in FIG. This perspective image is the human chest. Consider the XY coordinate axes as shown for the perspective image. The number of pixels in the horizontal direction (X direction) is m, and the number of pixels in the vertical direction (Y direction)
Let n be the number of pixels. The m × n pixels form one screen.

This perspective image is stored in the memory 5, and is read from the memory 5 and displayed on the display device 6. An example of storing a perspective image in the memory 5 is shown in FIG. 1 in memory 5
The perspective data is stored in the order of the second line, the second line, ..., The nth line.
Each row consists of m addresses. For example, for the first row, address 0, 1, 2, ..., allocates m-1, in each address corresponding fluoroscopic data D _0, D _1, D _2, ..., stores Dm _-1.
The other rows are the same.

Here, the perspective data Di (where i = 0, 1, 2, ..., Mm−
1) may be binary data (“1” or “0”) or multi-valued data (gradation data).

In the present embodiment, the fluoroscopic image displayed on the display device 6 is used for positioning when obtaining the CT tomographic image described above. For this use, a predetermined instruction is given from the input device 7, a predetermined process is performed according to the instruction, and a predetermined display is displayed on the display device 6.

Furthermore, it demonstrates concretely.

The slice center bed position P and the slice width s are given by the input device 7. The slice center bed position P is
Since the tomographic image has a constant slice width, it was intended to identify one point, and the center point of the slice width was identified. For example, the coordinate value ys in the Y direction in FIG. 2 is designated as the Y coordinate corresponding to the slice center bed position.

The slice width s is the tomographic width of the tomographic image. The width s sandwiching the center bed position P is referred to. The slice width s is disclosed in FIG. The slice width s is designated by the width in the Y direction on the display screen.

By inputting the center bed position P and the slice width s designated by the input device 7, the display position calculation device 8 performs processing so as to display the tomographic region on the display screen of the display device 6 in a superimposed manner on the perspective image. This process consists of the following processes.

(I) Creating a tomographic region on the display screen from the center bed position P and the slice width s. That is, in FIG. 2, a line segment A passing through the center position P and parallel to the X direction is created, and line segments B and C parallel to the X direction are created at the slice width s positions sandwiching the center bed position P. . Here, the line segment A is a solid line display, and the line segments B and C are a dotted line display.

(Ii) The data on the created line segments A, B, C are sent to the memory 5 and temporarily stored. Then, in the display device 6,
This data is read and displayed as shown in FIG.

(Iii) The center bed position P and the slice width s are used for positioning the bed 3. For that purpose, it is processed into control data, and the bed 3 is positioned via the control device 9.

A specific example of the above display position calculation device 8 is shown in FIG. The display position calculation device 8 includes a center display position calculation unit 81, a slice range display calculation unit 82, a slice range data generation unit 83, a memory control unit 84, and a bed position calculation unit 85.

(I) Center display position calculation unit 81 ... When the center target position ys on the Y coordinate corresponding to the slice center bed position is specified, the start address a of the line segment A including the position ys on the memory 5 is
Calculate with the following formula.

a = (ys−1) · m (1) However, (1ysn) (ii) Slice range display calculation unit 82: When the slice width s is specified, the vertical line corresponding to the slice range on the memory 5 The head addresses b and c of the minutes B and C are calculated according to the following formula.

First, the y-direction position of the line segment B is calculated by the following equation.

However, j is the length of one pixel, and the unit is (mm). Next, from the equation (2), similarly to the equation (1), the head address b of the line segment B is obtained by the following equation.

b = (yb-1) m = (ys-1) * ms * (m / 2j) = as * (m / 2j) (3) where a = (ys-1) * m. However, when b0, b = 0.

Furthermore, c is similarly obtained by the following equation.

c = a + s · (m / 2j) (4) However, when c (n−1) · m, it is c (n−) m.

(Iii) Slice range data generation unit 83 ... Fault area A,
Specify the color, shade, and type (distinction of solid line, dotted line, etc.) of the line segment that should display B and C. An example thereof is shown in FIG. Fifth
FIG. 9A shows display data of the center position line segment A, and is an example in which all m addresses are white display data W. Figure 5 (b) is the display data for line segments B and C, and
The white display data W and the black display data B are repeated for each address unit. The start address in Fig. 5 (a) is actually a in equation (1), and the start address in Fig. 5 (b) is actually b, c in equations (3) and (4). To do. This a,
The control unit 84 performs the replacement with b and c.

In addition to white and black, there may be an example of grayscale display.

(Iv) Memory control unit 84 ... Writing the data of the generating unit 83 in the memory 5 sequentially using the addresses obtained by the calculating units 81 and 82. The procedure is as follows.

First, the contents of address 0 of the slice range display data are written in the address b of the memory 5 obtained by the calculation unit 82. Next, the address of the memory 5 is set to (b + 1) and the contents of the address 1 of the slice range display data are written. Below, address 2 in sequence, ..., (m-1)
Write the street address in the same way. The same applies to the address c.

Next, the contents of address 0 of the center position display data are written in the address a of the memory 5 obtained by the calculation unit 81. Similarly, the contents of address 1 of the center position display data are written in the address (a + 1) of the memory 5. Thereafter, the center position display data is written in the memory 5 in the same manner.

Thus, the data of the line segments a, b, and c of the slice portion are stored in the memory 5 so as to be superimposed on the perspective image. At the time of display, the contents are read one after another while raster-scanning the memory 5, sent to the display device 6, and displayed. The displayed contents are as shown in FIG.

(V) Bed position calculation unit 85: The slice center bed position of the bed 3 is calculated by the following formula from the coordinate position ys.

P = P ₀ − (y ₀ −ys) · j (5) Here, y ₀ is the Y coordinate direction end reference position of the perspective image, and P ₀ is its bed position, as shown in FIG. Show. The distance P ₀ −P from the reference position to the slice center position is calculated by the equation (5) by P ₀ −P = (y ₀ −ys) · j (6), and the distance from the reference position (y _0- ys) · j is given to the control device 9, and 9 indicates this movement amount and the current bed 3
Based on the amount of deviation from the reference position of, the actual movement amount is calculated and the bed 3 is positioned. After this positioning is completed,
Perform the operation to obtain the CT tomographic image. This operation procedure (including the processing procedure) has been described above. According to the present embodiment, when performing positioning, not only the center position but also the shooting range is displayed at the same time, so that effective positioning can be performed while considering the shooting range.

In addition to the solid line and the dotted line, various display modes (changes in color and shade) are possible, and the slice width can be confirmed accurately. Further, the display range is not limited to the entire screen, but the start coordinate position and the end coordinate position are given to the control unit 84 in advance, so that the display range can be freely selected.

In this embodiment, the center position and slice width are designated. The slice width s may be a fixed value when the slice width is the same for any tomographic region, but when changing the slice width depending on the tomographic region, it is necessary to change the slice width s depending on the center position. The slice width is determined from the viewpoint of eliminating the amount of transmission and unnecessary exposure.

[Advantages of the Invention] According to the present invention, the imaging range for obtaining a CT image can be accurately known in advance from the fluoroscopic image. Furthermore, the automatic position can be accurately determined, and a highly accurate CT tomographic image can be obtained.

[Brief description of drawings]

FIG. 1 is an embodiment of the present invention, FIG. 2 is an illustration of a perspective image display, FIG. 3 is an illustration of data storage in a memory 5, FIG. 4 is an embodiment of a position calculation device, and FIG. (A) and (b) are examples of slice area display data. 1A ... Rotating frame, 1 ... X-ray source, 2 ... X-ray detector, 3 ... Bed, 4 ... Computer, 6 ... Display device, 7
...... Input device.

Claims (1)

[Claims] 1. A rotating frame having an X-ray source and an X-ray detector, which are provided to face each other across a measurement space, a bed for mounting a subject, which is movable in the measurement space of the rotation frame, and a CT. A first means for obtaining a fluoroscopic image from a detection value of an X-ray detector that penetrates the subject prior to obtaining a tomographic image, a memory for storing the fluoroscopic image, and a display device for displaying the content of the memory. Along with the means for displaying the CT slice center position and the slice width on the display screen of the display device according to external designation, the CT tomographic position is specified according to the slice center position and the slice width, and the CT tomographic image is obtained by the X-ray detector. X-ray CT system consisting of means for obtaining the detected values of