JPS61255641A - Radiation ct 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 an industrial radiation CT apparatus that performs non-destructive inspection of objects using radiation.

[Technical background of the invention and its problems] Conventional industrial X-ray CT devices emit X-rays from an X-ray tube toward an object to be examined, and transmit the X-rays that have passed through the object to multiple X-rays. XI with ray detector! This is an inspection device that converts electricity into electricity and obtains a tomographic image of the object using a computer. The X-ray detector used in this inspection device has a plurality of X-ray/electrical converters arranged closely together. Normally, X-ray detectors have a
It is equipped with iooo X-ray/electrical converters. These multiple X-ray/electrical converters theoretically have the same characteristics,
It is manufactured so that it can be used. However, in reality, the characteristics of all X-ray/electrical converters are not uniform due to manual work and parts used. Nonuniformity of these characteristics causes errors when a tomographic image of the object to be examined is reconstructed by a computer, resulting in inaccurate inspection.

There is also a CT system that uses a single X-ray/N gas converter and X-ray tube and performs a direct scanning operation, but although this system does not have problems due to non-uniformity of the detector characteristics, There was a problem in that it took more than 200 seconds to obtain one tomographic image, and the examination required a long time.

[Object of the Invention] The present invention has been made based on the above-mentioned circumstances, and is capable of reducing errors even when the characteristics of a plurality of X-ray/N gas converters are uneven, without prolonging the inspection time, and An object of the present invention is to provide a radiation 1cT device that makes it possible to obtain reliable tomographic images.

[Summary of the Invention 1 To achieve the above object, the present invention includes a pedestal fixing part having a cylindrical opening, a pedestal fixing part rotatably supported by the pedestal fixing part, and centered around the central axis of the cylindrical shape. , a gantry rotating part that rotates along the circumference of the cylindrical shape; a radiation source that is provided on the gantry rotating part and emits radiation toward the central axis; and a radiation source that supports the subject near the central axis. a subject mount that rotates the subject in the same direction as the rotation of the gantry rotation unit and at half the rotational speed; and a detection device that is located on the rotational trajectory of the radiation source and detects radiation that has passed through the subject. It is a radiation l1 ICT device equipped with a device.

[Embodiment of the Invention] An embodiment of the present invention will be described with reference to the drawings.

First, regarding the concept of the present invention, FIG. 1(A) and <8)
Refer to and explain.

Fig. 1 (A) shows a subject M with a protrusion on a part of a square,
An X-ray tube S rotates around the subject M with the center 0 of the subject M as an axis, and a circle P of the X-ray tube S.
P For example, 1024 X-ray detectors arranged in a densely fixed manner on a circumferential orbit, ~D1. □ is shown. The center of this subject M is set to 0, the horizontal direction of the figure is the X axis, and the vertical direction is the Y axis. The subject M rotates counterclockwise around 0 at an angular velocity ω. An X-ray tube S is located r away from the center O.
There is a PS. The X-ray tube S rotates counterclockwise along a circumference with a radius r around 0 at an angular velocity 2ω that is twice the angular velocity ω of the subject. At this time, the X-ray emitting direction of the X-ray tube S always faces the center 0, and emits fan-shaped X-rays having a predetermined spread angle with O as the center.

Now, focusing on the detector D, the X-rays emitted from the X-ray tube S and transmitted through the subject M enter the detector D. The locus of the X-rays transmitted through the subject M is assumed to be parallel to the X-axis.

Next, FIG. 1(B) shows the state t seconds after FIG. 1(A). Since the detector is fixed, in Fig. 1(B),
The subject M tct is rotated by an angle ω counterclockwise from the X-axis to the X-axis. Since the X-ray tube S is rotating at twice the angular velocity of the subject, it is at a position that has turned around 2ω, which is twice the angle ωt, from about ms t seconds ago. When XtlA is emitted from this position, it passes through the subject M and enters the detector D2. The trajectory of the X-rays is parallel to the X-ring.

If we focus on the detector in this way, if the X-ray tube emits aluminous radiation while rotating, all of them will pass through the subject M in parallel to the subject M. In other words, one detector can obtain parallel beams in one direction while the X-ray tube goes around the circumference of radius r while emitting radiation. By arranging 1024 detectors on a circumference of radius r, 1024 types of parallel beams are obtained. Since the parallel beam data obtained in this way is obtained by the same X-ray detector, these parallel beam data are not affected by the non-uniformity of the X-ray detector. Furthermore, the number of parallel beams can be determined by the number of irradiations during one rotation of the X-ray tube.

FIG. 2 shows an embodiment based on the above concept. In FIG. 2, there is a substantially cylindrical frame fixing part 1 with a circular hole in the center. A gantry rotating part 2 is provided on the outer circumferential surface of the gantry fixing part 1, and is rotated counterclockwise along the outer circumferential surface by a motor 8 at an angular velocity of 2ω. The gantry rotating section 2 is provided with an X-ray tube 5 that emits xmt toward the subject 4 . The subject 4 is placed on a subject mount 7 and rotated counterclockwise by a motor 6 at an angular velocity ω. Detector 3 has 10
It is a donut-shaped detection group in which 24 X-ray detectors are densely arranged, and detects X-rays that have passed through the subject 4. The operation of this detector 3 is such that four pistons provided on the gantry fixing part 1 always point the detection point facing the X-ray tube at the X-ray tube 5.
Move up and down so that it is parallel to the By performing a so-called Nutite operation, it is possible to detect the X-rays that have passed through the subject so that the radius of rotation of the X-ray tube 5 and the radius of the detector 3 do not overlap.

In this way, since the data of the two sets of parallel beams are obtained by the same X-ray detector, the data of these parallel beams are not affected by the non-uniformity of the X-ray detector.

Further, although the unevenness of the X-ray detector causes an effect on each coarse section of the parallel beam data, since there is no variation in the respective parallel beam data, no artifacts occur.

The parallel beam data in each direction obtained by the 1024 X-ray detectors in the detector 3 is reconstructed by a processing device (not shown) and displayed as a tomographic image of the subject 4.

[Effects of the Invention] According to the present invention, even if the characteristics of a plurality of X-ray/electrical converters are uneven, errors can be reduced and reliable tomographic images can be obtained without requiring a long inspection time.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the concept of a radiation CT apparatus according to the present invention;
FIG. 2 is a cross-sectional perspective view of an embodiment of the radiation CT apparatus according to the present invention. 1... Frame fixing part, 2... Frame rotating part 3... X-ray detection part, 4...
・Subject 5...X-ray tube, 7...
...Patent attorney representing the subject mount Kensuke Norichika (and one other person) Figure 1 (A) Figure 1 Date C) Figure 2

Claims (1)

[Claims] a pedestal fixing part having a cylindrical opening; a pedestal rotating part rotatably supported by the pedestal fixing part and rotating along the circumference of the cylindrical shape around a central axis of the cylindrical shape; , a radiation source that is provided on the gantry rotating section and emits radiation toward the central axis; A radiation CT apparatus comprising: a subject mount that rotates at half the rotational speed; and a detector that is located on a rotational orbit of the radiation source and detects radiation that has passed through the subject.