JPH02246934A - X-ray ct device - Google Patents

Abstract

PURPOSE:To improve the positional resolution of an image pickup body by providing a driving means to individually move a movable X-ray detector and a control means to execute a scanning system driving the driving means in a special system. CONSTITUTION:A gantry to integrate an X-ray generator 15 and a detector system 16A is rotated, data are acquired at each gantry angle beta, an they are used or an image recomposition. At such a time, depending on the angle betaat every gantry angle beta, each X-ray detector 10A is driven by a pulse motor 11, and the data related to an image pickup body 7 are acquired. For example, by using X1-X7 seven X-ray detectors 10A, the data are acquired in an ordinary fixed position in the case of beta=0, pi/6, in a position to make the detector X7 approach the detector X6 by a half pitch in the case of beta=2/6pi, in a position to make the detector X6 approach the detector X5 further by a half pitch, and in the same manner thereafter, in the positions to move the X-ray detectors 10A by a half pitch in the same direction up to beta=7/6pi. Next, the detectors X7 and X6 are returned to the original positions in the case of beta=8/6pi and beta=9/6pi, respectively, and in the same manner thereafter, the X-ray detectors 10A are moved, and the data are acquired up to beta=2pi.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an X-ray C'F device, and in particular to an X-ray C'F device.
The present invention relates to an X-ray CT apparatus in which positional resolution is improved by moving a detector in a predetermined manner.

[Prior Art] FIG. 3 is a block diagram generally showing an X-ray CT apparatus.
In the figure, (7) is an X-ray generation device that generates X-rays by deflecting an electron beam from an accelerator (not shown) and then applying it to an X-ray generation target (not shown). , (16) are arranged opposite to the X-ray generator (15) with the imaging body (7) in between, and are fixed in a metal frame or other protruding structure which will be explained later. ) is a detector system that consists of multiple X-ray detectors that actually detect the generated X-rays, and can obtain a large amount of data with - degree of X-ray irradiation, (17) is this detector system (16) (18) is an A/D converter that converts the analog signal from the detection i+1 system (16) into a digital signal under the control of this detector control device (17); This A/D converter (18
), a central processing unit (20) that performs arithmetic processing such as image reconstruction from digital signals related to the imaging object (7);
is a memory that temporarily stores data being processed by the central processing unit (19), (21) is an image display device that displays the reconstructed image from the central processing unit (19), and (22) is the central processing unit (19). ) X-ray generator (15)
This is an X-ray generator controller that sends control signals to the X-ray generator and controls the generation of X-rays.

Fig. 4 is a schematic cross-sectional view showing a conventional detector system for an X-ray CT device. (5)
An X-ray generation target that generates X-rays when irradiated with
8) is a support for supporting the imaging body (7). , (9) is a detector frame supporting a plurality of X-ray detectors of the detector system (16), and (lO) is an X-ray detector fixed to this detector frame (9).

A general X-ray CT apparatus and a conventional detector system are configured as described above, and their operation is as follows. The X-ray generator controller (
22) sends a control signal to the X-ray generator (15) and
The ray generating device (15) generates X-rays as appropriate. The generated X-rays pass through the imaging body (7) and are sent to the detector system (16).
Detected in The detected signal is sent to the detector control device (17
) is converted into a digital signal by an A/D converter (18) and sent as data to a central processing unit (19). X-ray generator (15) and detector system (1
6) is rotated 360 degrees around the imaging body (7), and the pig is captured at each angle. This data is stored in the memory (20) via the central processing unit (19). After the rotation is completed, the data stored in the memory (20) is appropriately taken out by the central processing unit (19) and subjected to calculations to reconstruct the image of the imaging body (7). The results are sent to the image display device (21) and displayed.

Here, in order to obtain a reconstructed image of the image pickup body (7) in the above operation, the X-rays from the X-ray generator (15) are rotated 360 degrees with respect to the image pickup body (7), and data is collected for each angle. Must try to get it.

Figure 5 shows the X-ray source S in the X-ray generator (15) and the detector system (16) that rotates integrally with it.
to the detector of the imaging body (7) (centered at the origin 0).

) with respect to the rotation angle β (this is called the gantry angle) and the X-ray irradiation focus point P (sixth
This figure shows the relationship between the rotation angle θ from the (x, y) coordinate system fixed in the laboratory and the distance X for (Fig.).

In this case, the data acquired by detector A is g (X, O)
The data acquisition situation is shown in FIG. 6. In addition, in FIG. 6(a), the origin O is the center of the imaging body (7), and the X-ray irradiation point P of the imaging body (7) is plotted with respect to the (x, y) coordinate system fixed in the laboratory. This figure shows the relationship between the angle θ and the distance X connecting OP. Figure 6(b)
is (X) in FIG. 6(a).

y) G (X, O) is plotted against the coordinate system (x, y) obtained by rotating the coordinate system by O.

As shown in FIG. 6(a), when the shaded area of the imaging body (7) is irradiated with X-rays, the imaging body (7) at this location
), the acquired data becomes as shown in FIG. 6(b).

FIG. 7 shows the above angle θ and coordinate system It shows the position of the container, in the conventional case O-X
Data was acquired at the position of a fixed grid point (O mark) on the coordinate system. Image reconstruction requires an angular width π in the O direction.
Data covering a wide range of areas is required.

[Problems to be Solved by the Invention] In the conventional X-ray CT apparatus, each X-ray detector (10) of the detector system (16) is fixed as shown in FIG. There was a problem in that only data at fixed grid points (0 marks) in FIG. 7 could be acquired, and the resolution of the reconstructed image was determined and limited by the number of X-ray detectors. That is, with 360° rotated data, the resolution decreases, and in order to improve the resolution, a rotation of 360° or more is required, resulting in problems such as an increase in irradiation dose and data acquisition time.

This invention was made to solve these problems, and it makes each X-ray detector of the detector system that rotates integrally with the X-ray generator movable individually, and An object of the present invention is to provide an X-ray CT device that can double the positional resolution by rotating 360° by driving the X-ray CT device.

[Means for Solving the Problems] An X-ray CT apparatus according to the present invention includes a plurality of movable X-ray detectors that are integrally opposed to an X-ray generator with an imaging body in between. , a drive means for individually moving the X-ray detectors according to a gantry angle which is a rotation angle of both of them, and a control means for controlling the drive means to move each movable X-ray detector by half a pitch.

[Function] In the present invention, a plurality of movable X-ray detectors are individually moved by the driving means. By scanning each movable X-ray detector by moving it by half a preset pitch according to the gantry angle, it is possible to reconstruct an image with twice the positional resolution compared to the conventional apparatus.

[Embodiment] FIG. 1 is a sectional view showing an embodiment of the X-ray CT apparatus according to the present invention, and in the figure (1) is an X-ray generating electron beam (
5), a vacuum duct (2) provided at the end of this accelerator (1) and into which the electron beam (5) is introduced;
(3) is the electron beam (5) introduced into this vacuum duct (2).
), (4) is the vacuum duct (3)
The electron beam extraction window (5) is provided in the 15
). (16^) is the detector system used in this invention, (10^) is a movable X-ray detector, (1
1) is a pulse motor which is a driving means for driving the X-ray detector (IOA), and (12) is a gear that transmits the rotation of this pulse motor (11) to the X-ray detector (IOA).

Figure 2 shows a detector system including an X-ray detector (IOA).
It is a perspective view showing a part of the X-ray detector (10^) in detail.
), and (I4) is a detector slide rail on which the X-ray detector (1 (IA)) slides.

In the X-ray CT apparatus configured as described above, an electron beam (5) accelerated by an accelerator (1), a vacuum duct (2)
), is deflected by 270° by a deflecting electromagnet (3), and is taken out from vacuum into the atmosphere through an electron beam extraction window (4). The extracted electron beam (5) is applied to an X-ray generation target (6) to generate braking X-rays. The generated X-rays are irradiated onto the imaging body (7), and the transmitted X-rays that have passed through this are sent to each X-ray detector (
10^) through the X-ray detection window (13),
Detected by line detector (IOA). The detected signal is data-processed in a subsequent processing device (not shown) and an image is reconstructed, as in the conventional device. To perform this image reconstruction, the gantry that integrates the X-ray generator (15) and the detector system (16A) is rotated, data is acquired at each gantry angle β, and the data is used for image reconstruction. This is the same as the conventional example.

However, in this invention, for each gantry angle β, the X-ray detection
(IOA) is driven by a pulse motor (11), and the imaging body (IOA) is driven by a pulse motor (11).
We are trying to obtain data regarding 7).

As shown in Figure 7, seven X-ray detectors (IOA) from X1 to X7 are used, six times per π of θ (every I76).
Obtain projection data (transmission X-ray data). This scanning method for data acquisition is performed by a detector control device as a control means and a central processing unit.

Specifically, as shown in Figure 7, ■) β-Q, g/
In step 6, projection data is acquired at a normal fixed position (marked with *).

2> For β-276g, move the X-ray detector X7 closer to the X-ray detector X6 by half a pitch as shown by the arrow in the figure,
・Acquire data at the marked position. 3) In β-376I, move X-ray detector X8 closer to X-ray detector X by half a pitch and acquire data at the * mark position. 4) Similarly, data is acquired by moving the X-ray detector (10^) by half a pitch in the same direction until the gantry angle β=176x. 5) Next, in β-8761, return the X-ray detector X7 to its original position and acquire data. 6) Furthermore, in β-9/6g, return the X-ray detector X8 to its original position and acquire data. 7) Similarly, move the X-ray detector (10^) according to Fig. 7,
Obtain data up to β-21. By driving each X-ray detector (IOA) in this way, 01 to
This means that data was acquired with a half-pitch shift in the X direction between g of θ and the other 2. Therefore, when using 14 X-ray detectors (10^) with 2I rotations, The same resolution can be obtained.

[Effects of the Invention] As explained above, the present invention includes driving means such as a pulse motor for individually moving movable X-ray detectors;
By providing a control means for executing a scanning method to drive this drive means using a special method,
This has the effect of increasing the positional resolution of the imaging body by twice as much as that of a line CT device.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a perspective view showing a part of the detector system in detail, Fig. 3 is a block diagram showing a general X-ray CT device, and Fig. 4 is a cross-sectional view showing a conventional detector system, FIG. 5 is a diagram showing the positional relationship between an X-ray source, an X-ray detector, and an imaging body, and FIG. 6 is a diagram showing the variable O1X used in FIG. 5 and acquired data. A function g (X,
0), and Figure 7 shows the position of each detector in the O-X coordinate system using the gantry angle as a parameter. is a bending magnet, (
5) is an electron beam, (6) is an X-ray generation target, (7) is an imaging body, (IOA) is a movable X-ray detector, (11)
is a pulse motor. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] An X-ray generator that generates X-rays by deflecting an electron beam accelerated by an accelerator and hitting an X-ray generation target, and a gantry that is integrated with and interlocks with this X-ray generator, and an imaging body. A plurality of X-ray detectors are arranged oppositely with a plurality of an X-ray C
In the T device, each X-ray detector is movable, and a drive means for individually moving each movable X-ray detector according to a gantry angle that is a rotation angle of the gantry, and a drive means for controlling the drive means. An X-ray CT apparatus comprising: control means for moving each movable X-ray detector by half a pitch while the gantry rotates 360 degrees.