JP3174621B2 - Industrial CT apparatus and scanogram imaging method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CT (Computed Tomography) apparatus using high-energy X-rays for industrial use, and in particular, to two-dimensional fluoroscopy required in advance to determine a CT imaging region of a subject. The present invention relates to an industrial CT apparatus suitable for capturing an image (scanogram image).

[0002]

2. Description of the Related Art In an X-ray CT apparatus, a subject is placed between an X-ray source and a detector, and the X-ray source and the detector are relatively moved with respect to the subject with respect to the subject. It is designed to rotate and translate. In order to determine the imaging region of the subject, it is necessary to first capture a fluoroscopic image of the entire subject. This fluoroscopic image is obtained by moving the detector around the X-ray source and scanning the object so that the line connecting the X-ray source and the detector crosses the subject. However, as described above, the X-ray CT apparatus includes only a mechanism that scans around the subject, and does not include a mechanism that scans around the X-ray source. Therefore, conventionally, when the subject is slightly rotated, the X-ray source and the detector are moved in parallel with respect to the subject so that a fluoroscopic image centered on the X-ray source is equivalently obtained. I have. For example, Japanese Patent Application Laid-Open No. 2-64442
In the prior art described in Japanese Patent Application Publication No.
Detector having one detection element, the object is placed between the X-ray generator, the distance between the centers of the detection elements x, when the spread angle of X-rays incident on one detection element is φ, The subject is rotated by φ / 2 at a time, and is translated by x / 2 in synchronization with the rotation.

[0003]

The prior art described above is
A detector including a plurality of detection elements arranged adjacent to each other is used. This is based on the premise that X-rays in the range detected by one detection element do not affect the detection values of adjacent detection elements, and that a weak X-ray source is used. That is, the technique is limited to a medical CT apparatus.
Further, the subject is rotated by φ / 2 at a time, and in synchronization with the rotation, x / 2
When the translation scanning is performed, X
Since the line transmission cannot be detected, there is a problem that a transmitted image of that portion is dropped. However, when a small detecting element is used for medical use, the omission of the image is not a problem. However, in an industrial CT apparatus, since the intensity of X-rays to be used is high, an interval between detectors is provided so that the influence of an adjacent detector does not appear on an image. That is, since the interval between the detectors is wide, if an image in this portion is dropped, it cannot be used as a fluoroscopic image. Further, in the case of an industrial CT apparatus, it is necessary to create a fluoroscopic image while eliminating the influence of the distance between the X-ray source and the subject, and the above-described conventional technology cannot be applied as it is.

An object of the present invention is to provide an industrial CT apparatus capable of obtaining a high-precision fluoroscopic image of an object by relative rotation and translational scanning between an X-ray source and a detector and the object. Is to do.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radiation source for emitting radiation by a fan beam, a plurality of radiation detectors arranged in a fan-shape, a radiation source, a detector and an object. In an industrial CT apparatus including a scanning unit that performs relative scanning between the detector and a computer that generates an image of a subject from radiation transmission data collected from the detector, a radiation beam input to each detector with a fan beam is used. When the divergence angle is φ and the distance between the radiation source and the subject is m, the scanning unit controls the translation unit to perform translational scanning of the subject at a pitch of φ × m and rotationally scan by an angle φ in synchronization with the translation. It is achieved by providing.

[0006]

[Effect] Even when a plurality of detectors are separated from each other, an image of a subject is obtained by synchronizing the translational scan of φ × m and the rotational scan of φ to obtain an image equivalent to the radiation source. A high quality transparent image without omission is obtained.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. First, the principle of the present invention will be described. In the present invention, the radiation source and the detector or only the subject are scanned in translation and rotationally scanned while irradiating the subject with fan beam radiation. At this time, each scan is
Scanning is performed synchronously so as to fill the spread pitch between the detectors spaced in a fan shape. In other words, the detectors arranged in a fan shape have a wider interval between the detectors than the widths of the respective detectors, so that only one transmission data can be collected in a single data collection. Scan to fill in the part that you set. However, it is not possible to collect data equivalent to densely illuminating the radiation source with the fan beam by using only the rotation scanning.
Collect data equivalent to irradiating densely with a system.

By the above scanning, a scanogram image of the subject having a size within the range of the fan beam angle of the radiation can be collected. However, when a larger scanogram image of the subject is taken, the scanogram is taken first. So that an image similar to the first scanogram image taken adjacent to the scanned scanogram image is obtained, that is, the detector is rotated by the fan beam angle of the radiation around the radiation source. Source and detector or analyte only
The translation scanning and the rotation scanning are performed. As in the case of the above operation, data equivalent to densely illuminating the radiation source with a fan beam around the radiation source is collected by translational scanning and rotational scanning. The above scanning is repeated until a scanogram image of the entire subject can be taken, and finally, data equivalent to irradiating the whole subject densely with a fan beam centering on the radiation source is collected, and Obtain the entire scanogram image.

Further, according to the present invention, when the thickness of the object is small, only the radiation source and the detector or only the object are translated while performing only translational scanning in the longitudinal direction of the object at a pitch equal to the width of the detector itself. The transmission data in the thickness direction is collected. Then, data transmitted through a point of interest of the subject, for example, a center point in the thickness direction is collected and added. At this time, the number of data to be added per one point is the same as the number of detectors spaced apart in a fan shape. As a result, a high-quality image with less noise can be obtained.

Hereinafter, specific embodiments of the present invention will be described.
FIG. 1 is an explanatory diagram of an industrial CT apparatus according to a first embodiment of the present invention. The industrial CT apparatus includes a radiation generator 1 for generating, by a fan beam, powerful radiation penetrating a subject 2 such as an industrial structure, for example, a nuclear reactor structure, and a turntable for rotating and scanning the subject 2. Table 3, a translation scanning mechanism 4 for translating the subject 2 and the turntable 3 in translation, and scanning means
Is perpendicular to the plane where the object is translated and rotated.
Table 3 and translation scanning mechanism in the vertical direction
4, a plurality of radiation detectors 6 of the same configuration (three radiation detectors 6a, 6b, 6c in the present embodiment), which are installed in a fan shape and are separated from each other, and are rotated. A controller 7 for controlling scanning, translational scanning and Z-axis movement;
A signal processing circuit 8 for processing signals from the radiation detectors 6a to 6c, a computer 9 for creating a scanogram image based on data from the signal processing circuit 8, and a CRT 10 for displaying the created scanogram image. Have.

The opening angle between the radiation detectors 6a, 6b, 6c is θ, the spread angle of the fan beam-shaped X-rays incident on the radiation detectors 6a, 6b, 6c is φ, and the radiation generator 1 and the turntable. Let m be the distance between the centers of rotation of the bulls 3. Here, θ is a multiple of φ. At this time, the range of the X-rays irradiated by the radiation generator 1 needs to be 2θ + φ or more.

FIG. 2 is an explanatory diagram of translational scanning and rotational scanning. FIG. 2A shows a state at the start of measurement. First, the radiation beam enters the radiation detectors 6a, 6b and 6c through the paths 101, 102 and 103. Next, the radiation beams 101 and 10 are focused on the radiation generator 1.
Paths 201, 202, 20 obtained by rotating 2,103 by φ
It is necessary to collect the data passing through 3. Therefore, FIG.
As shown in (c), the turntable 3 on which the subject 2 is placed is rotated by an angle φ, and the rotation center at this time is the center of the turntable 3 and the turntable is rotated. With only the rotary scanning by the table 3, even if the inclination of the radiation beam is equal to the paths 201, 202, and 203 shown in the figure, data in which the position of the radiation generator 1 is shifted by φ × m is obtained. . Therefore, in order to correct this shift, the turntable 3 is moved by the translation scanning mechanism 4 to φ ××, as shown in FIG.
m, and the radiation beam 2 shown in FIG.
Data of 01, 202 and 203 are collected.

The scanning direction when the subject 2 is viewed from above is
When the rotation scanning direction is clockwise, the translation scanning direction is left, and when the rotation scanning direction is counterclockwise, the translation scanning direction is right. By executing the above scanning θ / φ times, it is possible to collect data equivalent to the case where the radiation detectors are continuously and densely arranged as shown in FIG. In the example shown in FIG. 3, rotation scanning and translation scanning are performed four times.

After the data obtained by the above scanning is collected, the turntable 3 and the translation scanning mechanism 4 are scanned upward or downward by the Z-axis moving mechanism 5 and are equivalent to those shown in FIG. Alternatively, scanning is performed in the reverse direction, and the data shown in FIG. 3 is collected again. By repeating the above scanning, two-dimensional radiation transmission data at each Z-axis position is collected, a grayscale display image based on the transmission intensity is obtained by the computer 9, and is displayed on the CRT 10. According to this embodiment, since one scanogram image can be obtained by increasing the use efficiency of the radiation beam, there is an effect that a scanogram image can be obtained in a short time.

In the above-described embodiment, the number of detectors is three. If the number of detectors other than three is plural, the opening angle of each radiation detector is θ, and the X-rays incident on each radiation detector are θ. A scanogram image can be collected in the same manner as in the embodiment, where the spread angle of φ is φ. In this embodiment, the subject 2 is scanned in translation and rotation, but the radiation generator 1 and the radiation detector 6 are scanned.
Can be translated and rotated, or the object 2 can be translated and the radiation generator 1 and the radiation detector 6 can be rotationally scanned. Alternatively, the object 2 can be rotationally scanned and the radiation generator 1 and the radiation detector 6 can be scanned. May be translated. Further, the radiation generator 1 and the radiation detector 6 and the subject 2 only need to relatively move up and down. Even if the subject 2 moves up and down, the radiation generator 1 and the radiation detector 6 move up and down. You may move.

FIG. 4 is an explanatory view of an industrial CT apparatus according to a second embodiment of the present invention. As shown in FIG. 4, when the object 2 is larger than the range that can be seen by the three fan-shaped detectors 6a, 6b, and 6c, the method shown in the first embodiment uses the entire object 2. Cannot be taken to capture a scanogram image. Therefore, as shown in FIG.
After collecting a scanogram image in the range of 3θ in the clockwise rotation direction by the method shown in the embodiment, as shown in FIG. The subject 2 is rotated by the turntable 3 in the clockwise direction by an angle 2θ by the turntable 3, and further the translation scanning mechanism 4 scans the subject 2 leftward by a distance 2θ × m, and then again in the first embodiment. 3θ in the clockwise rotation direction by the method shown in
Collect a scanogram image of the range. The above scanning is performed until a scanogram image of the entire subject 2 is acquired.
After the repetition as shown in (c), the subject 2 is moved up and down to capture a two-dimensional scanogram image of the subject 2.

According to the second embodiment, even when the subject 2 is large, one scanogram image can be obtained by increasing the use efficiency of the radiation beam, and the scanogram image can be obtained in a short time. . Although the clockwise translation scanning direction of the subject 2 is set to the left in the clockwise translation direction, the rotation scanning direction of the subject 2 may be set to the right in the counterclockwise translational scanning direction. In addition, the number of radiation detectors was set to three. However, if the number of radiation detectors other than three is plural, the opening angle of each radiation detector is θ and the spread angle of X-rays incident on each radiation detector is φ. Needless to say, a scanogram image can be collected similarly. Furthermore, although the subject 2 is translated and rotated, the radiation generator 1 and the radiation detector 6 can be translated and rotated, or the subject 2 can be translated and the radiation generator 1 and the radiation detector can be scanned. Alternatively, the subject 2 may be rotationally scanned and the radiation generator 1 and the radiation detector 6 may be translationally scanned. Further, the radiation generator 1 and the radiation detector 6 and the subject 2 only need to relatively move up and down. Even if the subject 2 moves up and down, the radiation generator 1 and the radiation detector 6 move up and down. You may move to

FIG. 6 is an explanatory diagram of a third embodiment of the present invention. As shown in FIG. 6, when the thickness of the subject 2 is small, the subject 2 is moved by the translation scanning mechanism 4 to each of the detectors 6a, 6b,
6c is translated at a pitch equal to the width of each of the detectors 6a to 6c.
6c collects radiation transmission data over the entire length of the subject 2.
Then, each point of the subject 2, for example, 3
The radiation transmission data of the two detectors 6a to 6c are added.
Such addition is performed for each point on the X axis, the subject 2 is moved up and down to collect two-dimensional data, and one scanogram image is obtained from the added data. According to this embodiment, since a large number of transmission data can be used for capturing one scanogram image, there is an effect that a high quality image can be obtained. In the third embodiment, the X-axis can be set at an arbitrary position on the subject 2, and the object to be translated or moved up and down may be the subject 2, the radiation generator 1, and the radiation detector 6.

[0019]

According to the present invention, in an industrial CT apparatus, the interval angle between the detectors is θ, the spread angle of the fan beam-like X-rays incident on each detector is φ, and the radiation generator and the subject are connected to each other. When the distance of m is m, the translation scan of φ × m and the rotation scan of the angle φ are synchronized and executed θ / φ times to collect radiation transmission data of the subject and generate a scanogram image. A highly accurate scanogram image can be obtained in time. Further, since a scanogram image is generated based on the data obtained by adding the data of the same point of the subject of each detector, a high quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an industrial CT apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an operation of the CT apparatus according to the first embodiment.

FIG. 3 is a diagram showing a collection result of transmission data.

FIG. 4 is an explanatory view of an industrial CT apparatus according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of an operation of the CT apparatus according to the second embodiment.

FIG. 6 is an explanatory diagram of an industrial CT apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Radiation generator, 2 ... Subject, 3 ... Turntable, 4 ... Translation scanning mechanism, 5 ... Z-axis drive mechanism, 6 ... Radiation detector, 7 ... Controller, 8 ... Signal processing circuit, 9: Computer, 10: CRT, 101 to 404: Detector incident radiation beam path.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Miyai 1168 Moriyama-cho, Hitachi City, Ibaraki Prefecture Energy Research Laboratory, Hitachi, Ltd. Hitachi, Ltd. Hitachi Plant (56) References JP-A-2-64442 (JP, A) JP-A-3-209120 (JP, A) JP-A-62-2224332 (JP, A) JP-A-2-201253 (JP JP, A) JP-A-2-201254 (JP, A) JP-A-59-181133 (JP, A) JP-A-59-97650 (JP, A) JP-A-59-97649 (JP, A) International publication 92/6367 (WO, A1) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 23/00-23/18 JICST file (JOIS)

Claims (8)

(57) [Claims] 1. A radiation source for emitting radiation by a fan beam, a plurality of radiation detectors arranged in a fan-shape, and a relative scan between the radiation source, the detector and the subject. In an industrial CT apparatus including a scanning unit and a computer that generates an image of a subject from radiation transmission data collected from the detector, the spread angle of radiation input to each detector by a fan beam is φ, When the distance to the subject is m, the scanning unit includes a control unit that performs translational scanning of the subject at a pitch of φ × m and rotationally scans the object by an angle φ in synchronization with the scanning. C
T device. 2. A radiation source for emitting radiation by a fan beam, a plurality of radiation detectors arranged in a fan-shape, and a relative scanning between the radiation source, the detector and the subject. In an industrial CT apparatus including a scanning unit and a computer that generates an image of a subject from radiation transmission data collected from the detector, an opening angle between the detectors is θ, and radiation input to each detector by a fan beam is provided. The spread angle of φ,
When the distance between the radiation source and the subject is m, the scanning unit includes a control unit that performs translational scanning of the subject at a pitch of φ × m and rotationally scans the subject by an angle φ in synchronization with the scanning. An industrial CT apparatus comprising means for generating an image from data obtained by performing the translational scan and the rotational scan θ / φ times. 3. An apparatus according to claim 1 or claim 2, scanning means, between the radiation source and the detector and the object, scanning hand
The step is perpendicular to the plane where the object is translated and rotated.
The computer is provided with means for relatively scanning in the direction.
An industrial CT apparatus, comprising: means for accumulating for each vertical scan and generating a fluoroscopic image of a subject as a gray-scale image. 4. A radiation source which emits radiation by a fan beam, a radiation detector arranged in a fan shape and spaced apart from each other by n (n is plural), and a relative relation between the radiation source and the detector and the subject. In an industrial CT apparatus including a scanning unit that performs a general scan and a computer that generates an image of a subject from radiation transmission data collected from the detector, the spread angle of radiation input to each detector with a fan beam is determined. φ, when the distance between the radiation source and the subject is m, when the subject does not fit in the sector, first, approximately half of the subject is φ for the range of nθ.
× m pitch translation scan and in synchronization with this angle φ
Means for rotationally scanning each time, then means for translational scanning by (n-1) × m, and then translational scanning again at a pitch of φ × m within the range of nθ, and rotationally scanning by an angle φ in synchronization with this. Means for detecting fluoroscopic data of the entire subject is provided in the scanning means, and the computer is provided with means for generating a fluoroscopic image of the subject from transmitted image data detected by each detector for each scan. Industrial CT apparatus. 5. A radiation source for emitting radiation by a fan beam, a plurality of radiation detectors arranged in a fan-shape, and relative scanning between the radiation source, the detector and the subject. In a scanogram imaging method for an industrial CT apparatus including a scanning unit and a computer that generates an image of a subject from radiation transmission data collected from the detector, a spread angle of radiation input to each detector with a fan beam is set to φ. Assuming that the distance between the radiation source and the subject is m, the subject is translated and scanned at a pitch of φ × m, and rotated and scanned by an angle φ in synchronization with the translation, and the transmission detected by each detector for each scan. A scanogram imaging method, wherein a fluoroscopic image of a subject is generated from image data. 6. A radiation source which emits radiation by a fan beam, a radiation detector arranged in a fan shape and spaced apart from each other by n (n is a plurality), and a relative relationship between the radiation source and the detector and the subject. In a scanogram imaging method of an industrial CT apparatus including a scanning unit for performing a general scanning, and a computer for generating an image of a subject from radiation transmission data collected from the detector , each detection is performed using a fan beam. When the spread angle of the radiation input to the vessel is φ, and the distance between the radiation source and the subject is m,
When the subject does not fit in the sector, first, approximately half of the subject is translated in the range of nθ at a pitch of φ × m and rotationally scanned by an angle φ in synchronization with the translation, and then,
(N-1) × m, and then scan again at φ × m pitch in the range of nθ, and rotate and scan by angle φ in synchronization with the scan to detect fluoroscopic data of the entire subject. A scanogram imaging method, wherein a fluoroscopic image of a subject is generated from transmitted image data detected by each detector for each scan. 7. A means for adding transmission data of the same point of an object detected by each detector according to any one of claims 1 to 4, and a fluoroscopic image of the object based on the added transmission data. Means for generating a CT. 8. The method of Claim 5 or claim 6, in that each detector adds the transmission data of the same point of the subject to respectively detect, to generate a fluoroscopic image of the subject in addition to the transmitted data Characteristic scanogram imaging method.