JPS59120139A - Radiation tomographic 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 a computerized tomography apparatus (hereinafter abbreviated as CT apparatus) C1 that obtains a tomographic image of a subject by irradiating radiation IfM (for example, X-rays). It is.

[Technical background of the invention and its problems]

As shown in FIG. 1, for example, an X-ray CT apparatus includes an X-ray source 1 that emits fan beam X-rays (hereinafter referred to as single X-rays) having a flat fan-shaped spread angle θ, and The X-ray detector 2 includes a plurality of X-ray detection cells arranged in parallel to detect the X-rays transmitted through the specimen P, and the X-ray source 1 and the X-ray detector 2 are relative to each other. is rotated around the subject P to collect X-ray transmission data in all directions on the tomographic plane of the subject P. After collecting sufficient data, this data is analyzed by a computer and the tomographic plane of the subject P is The X-ray absorption rate corresponding to each position is calculated, and the image information on the cross section f2 of the subject is reconstructed using a gradation level corresponding to the absorption rate, and the image information is reconstructed from soft tissue to hard tissue. A clear tomographic image can be obtained up to the tissue C1.

Most of the X-ray detectors used in conventional CT equipment include ionization chamber detectors and scintillation detectors, which convert the detected analog signals into digital signals and send them to a computer computer.
: I am trying to send it.

Therefore, the number of detectors to be used in advance is limited, and a circuit after the amplification stage is required depending on the number of detectors, so if high resolution is required, for example, there is a problem of high cost. In addition, since this device performs reconstruction based on all the image data C2, processing time can be shortened by reconstructing only the data of the region of interest of the subject and displaying the image. It was difficult to say what was going on.

For these reasons, it could not be applied to industrial fields where high spatial resolution and low cost are required.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances (1), and aims to provide a radiation CT apparatus that can ensure high resolution, reduce costs, and is suitable for application to the industrial field (2). be.

[Summary of the Invention] In order to achieve the above object, the present invention uses a memory type two-dimensional radiation detector (hereinafter referred to as a memory plate) as a two-number ray detector, and also allows data stored in this memory plate to be arbitrarily stored. The device is characterized in that it is constructed by a reading means that reads the image while scanning it.

[Embodiments of the invention]

The present invention will be specifically explained below with reference to Examples.

FIG. 2 is a schematic diagram of a main part showing an embodiment of the data collection section of the apparatus of the present invention, and FIG. 6 is a schematic diagram of the main part showing an embodiment of the data processing section of the apparatus of the present invention.

The data collection unit includes an X-ray tube 6f which is a radiation line that generates a fan-shaped beam, and a flat plate 1 arranged opposite to each other.
The memory plate 4 is composed of a plate 4 and a subject 5 and f2, which are attached to the middle part i2, and the memory plate 4 is driven by a drive mechanism C (not shown). The subject 5 is movable in the Y direction) and is rotated about a rotation axis 6 by a drive mechanism (not shown). Furthermore, the movement of the memory plate 4 and the rotation of the subject 5 are synchronized.
). Therefore, the data of each rotation angle in one tomographic plane (slice plane, hatched part in the figure) 5A+2 of the subject is sequentially converted to Il1-order C2-2 for each row direction of the storage plate 4 (2). As such a storage plate 4, it is preferable to use a screen film or an imaging plate that stores known X-ray images.

The data processing section includes an optical readout means that connects a light source 7 and a photodetector 8 which are arranged opposite to each other with the storage plate 4 in between, and an A/D that converts an analog signal from the detector 8 into a digital signal. It is composed of a converter 9, an image reconstruction device 10 mainly composed of an arithmetic processing unit, and a display device 11 that displays an image based on reconstructed data.Ai
A laser beam generator capable of irradiating any position is used as the light source, and a storage plate 4 is used as the photodetector.
It is preferable to use a photodensitometer that outputs an electrical signal according to the intensity of the laser beam that has passed through the photodensitometer. Here, when scanning the laser beam, it is preferable that the detector 8 also moves in synchronization with the scanning C2 of the laser beam. Alternatively, a method of scanning the laser beam in a fan shape using a vibrating mirror can also be adopted. In this case, it is preferable to use a linear detector corresponding to the fan width of the laser beam. In either case, A control section (not shown) allows the beam to be scanned at any position and by any width.

Next (2) The operation of the above component device will be explained. Data collection unit (
Second, the fan-shaped beam FB is emitted from the X-ray tube 6 while synchronizing the rotation of the subject 5 and the movement of the storage plate 4 as described above. As a result, the transmission data for each rotation angle in one tomographic plane of the subject 5 is sequentially stored row by row (two consecutively) along the movement direction number two of the storage plate 4. In this case, the data is compared as the storage plate 4. By using a long target, multiple tomographic planes along the body axis (2) of the subject 5 can be obtained.
It is also possible to divide the data in two areas and store them sequentially.

Next, in the data processing section, the light source 7 and the detector 8 are linked to scan the light beam (laser beam), and at this time (2) the obtained analog signal from the detector 8 is A/D converted. The converter 9 sequentially converts the digital signal into two, and the reconstructor 10
The tomographic image is then subjected to image reconstruction processing and sent to the display device 1/11, where the tomographic image is displayed.

Here, since the scanning of the light beam can be performed arbitrarily, the following data processing becomes possible.

That is, for example, if a region of interest 5B exists within one slice 5A of the subject 5 as shown in FIG.
Projection data 5B at angle θl of line fan beam XL
' is stored as data having a width of the storage plate 4 (2A), and the entire storage plate 4 (2) is the area of interest for each angle as shown in Figure 5 (2). Therefore, by specifying the position data and width A regarding the sine curve when scanning with the light beam described above, it is possible to extract only the data 5B of the region of interest. When using such a method, it is important to specify multiple regions of interest and multiple boundaries from the beginning, so first scan the memory plate 4 at a coarse pitch and create an image based on a small number of defects. Perform reconstruction and display the image, observe the image, select and specify the region of interest, and perform image reconstruction by extracting data only for the region of interest based on the selected and specified information in the next scan. That's fine.

Incidentally, if the region of interest in the subject 5 is located at a position offset from the center of rotation of the wandering sample, it will be stored in a substantially sine curve-shaped region on the memory plate-L (although the region of interest is located at the center of rotation). In this case, it is stored as a straight line area on the storage plate (2), so scanning of the light beam is easier (2).

The present invention is not limited to the above embodiment g. For example, in the above embodiment, the subject was rotated to change its relative position with the fan beam; The same function may be provided by

〔Effect of the invention〕

As described in detail, the present invention stores radiographic projection data in a storage plate and provides optical reading I that can be arbitrarily scanned.
Since it is possible to extract data from only the region of interest using JX', t, and process it as data for reconstruction, precise processing is possible, ensuring high spatial resolution, and reducing the need for amplifier circuits, etc. Therefore, it is possible to reduce the price and provide a radiation tomography apparatus that is most suitable for industrial use.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a schematic explanatory diagram of a conventional device, FIG. 2 is a schematic diagram of an embodiment of the data collection section of the device of the present invention, and FIG. 6 is a schematic diagram of the main part of the device of the present invention. 4 and 5 are projection state diagrams and storage state diagrams for explaining the operation of the device of the present invention. 3...Radiation source, 4 ...Memory plate 5...
・Subject, 7...Light source, 8...Photodetector, 9.
...A/D converter, 10...image reconstruction device.
11...Display device.

Claims (1)

[Claims] a radiation source that irradiates fan-shaped radiation to a subject≦2;
The position for detecting the radiation transmitted through the subject (2) has a flat storage plate installed, moves the subject or the fan-shaped radiation relatively, and in synchronization with this relative movement, the storage plate is placed on the storage plate. A data collection unit that moves parallel to the body axis of the specimen; an optical readout unit that scans the data at a desired position on the storage plate that stores the data; 1. A radiation tomography apparatus comprising: a data acquisition section comprising a means for reconstructing data.