JPS63242082A - Tomograph - Google Patents

Abstract

PURPOSE:To obtain a tomogram with excellent picture quality by collecting radiant ray projection data of photographing region formed to a specific cross section of a body to be checked and correcting the radiant ray projection data of the body to be checked based thereupon. CONSTITUTION:An X-ray beam 1 is radiated to a specific cross section of a correction check body from an X-ray generator 2 by a command of a control console part 18, the projected data is detected by each detection element of an X-ray detector 3 and the projected data from each detection element is collected by a data collection section 14. Then the correction data is read, logarithmic transformation is applied and the result is stored in a prescribed area of the memory 16. Then an X-ray beam 1 is radiated to the specific cross section of the body to be checked 6 from the X-ray generator 2 to collect the X-ray projection data outputted from the X-ray detector 3 by the section 14. Then the correction data stored in the memory 16 is used to reconstitute the tomogram by the X-ray transmission distribution in the photographing region 5 in the specific cross section of the object 6. Thus, the tomogram with high picture quality is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a tomographic imaging apparatus used for non-destructive inspection and the like.

(Prior art) As a tomographic imaging device, an X* generator serving as a radiation source irradiates X-rays from all around a specific cross section of an object to be inspected, and an X-ray detector measures the amount of transmitted X-rays a. A so-called XImCT scanner that obtains projection data through measurement and obtains a tomographic image of a specific cross section of the object to be inspected from this projection data is common.

From the tomographic images at each slice position obtained by this CT scanner, information regarding the measurement of the object to be inspected,
For example, it is widely used for industrial purposes because it can obtain information such as the dimensions, cross-sectional shape, and presence or absence of defects of the object to be inspected.

By the way, as shown in FIG. 5, some conventional tomographic F14m imaging devices of this type include an X-ray generator 2 that emits a fan-shaped X-ray beam 1 having a predetermined spread angle, and an X-ray generator 2 that receives all the X-ray beams 1. An X-ray detector 3 consisting of possible multiple channels of X-ray detection elements is arranged facing each other on a rotating frame 4,
The object to be inspected 6 is placed within the shadow area 5 of the X-ray beam 1, and the rotating frame 4 is rotated once, that is, the X-ray generator 2 and the X-ray detector 3 are rotated once. There is a system in which a tomographic image is obtained by collecting radiation projection data from each direction for a specific cross section of 6.

In such a tomographic image device, the resolution R of the tomographic image is expressed as R″F (diameter of the shadow area)/(number of detector channels).
The resolution of the tomographic image can be improved by reducing the diameter of the imaging area 5 by irradiating it with the A beam 1 and collecting radiation projection data only for this area. However, in this case, the portion of the object 6 to be inspected that protrudes from the shadow area 11i5 will be affected, resulting in an image error in the tomographic image and a deterioration in image quality.

Therefore, when used as an industrial CT scanner, it is necessary to arrange the X-ray generator 2 and X-ray detector 3 so that the specific cross section of the object to be inspected 6 is completely included within the imaging area 11!5. Ta.

(Problems to be Solved by the Invention) As described above, if the imaging area 5 is made smaller than the specific cross section of the object to be inspected 6, an image error will occur and the image quality will deteriorate. Even if the desired part is a part of the object 6 to be inspected, the imaging area 5 must be enlarged to include the object 6, making it difficult to improve the resolution of the tomographic image. Further, although it is possible to improve the resolution by increasing the number of channels of the radiation detector, there is a limit to the miniaturization of the detection element and an increase in cost is unavoidable.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a tomography sIiIms apparatus that can easily compensate for image errors caused by influences outside the imaging region and can obtain tomographic images with high resolution and good image quality at low cost.

[Structure of the Invention] (Means for Solving the Problems) The present invention irradiates a specific cross section of an object to be inspected with radiation in a fan shape from multiple directions with a predetermined spread angle, and In a tomographic imaging apparatus that collects radiation projection data from the object, performs image reconstruction processing on the collected radiation projection data, and outputs a tomographic image based on the radiation transmittance distribution of a particular cross section, Radiation irradiation means for irradiating a partial region with radiation from multiple directions, and said radiation irradiation means for a correction inspection object in which the outside of the region is the same component for the imaging region formed in a specific cross section of the object to be inspected by this means. a correction data collection means for collecting radiation projection data by irradiating radiation with the means; and a data correction means for correcting the radiation projection data of the subject to be inspected which is connected by the radiation irradiation means based on the correction data collected by the means. It is equipped with the following.

(Function) By taking such measures, the influence of areas outside the imaging area on the radiation projection data of the object to be inspected is corrected, and a high-quality tomographic image is obtained. It is possible to make it smaller than.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment in which the present invention is applied to an XICT scanner. Note that the same parts as in FIG. 5 are given the same reference numerals, and detailed explanations will be omitted.

On the rotary table 4, arrows A1. A cross-section C-shaped frame 12 that is horizontally movable in the A2 direction is attached, and an X-ray generator 2 and an X-ray detector 3 are disposed facing each other on this C-shaped frame 12.

Also, on the rotating frame 4, a phantom stand 1 on which a correction test object (not shown) is placed for collecting correction data.
3 is fixed, and the C-shaped frame 12 moves horizontally above the phantom stand 13.

The object to be inspected 6 is axially symmetrical and arranged so that the rotation axis of the rotary frame 4 and the central axis of the object to be inspected 6 coincide. In this embodiment, the object to be inspected 6 uses a container 6C in which a medium 6b such as water is filled and a measurement object 6a is placed inside the medium 6b. Furthermore, the X-ray generator 2 and the X-ray detector 3 are arranged so that the imaging area 5 is the measurement target 6a.
Place it so that it is small enough to contain only the

The data collection unit 14 collects projection data based on the X-ray intensity detected by each detection element of the X-ray detector 3 in multiple directions of the object to be inspected 6, and the collected data is transmitted to the CPLI 15. will be sent to.

The CPU 15 has a built-in arithmetic circuit, etc., and has a preprocessing function for converting projection data into input data for the reconstruction algorithm, a correction function for correcting the preprocessed data, and an X-ray transparency correction function for corrected data according to the reconstruction algorithm. It has a reconstruction processing function that reconstructs tomographic images based on distribution. Also connected to the CPU 15 are a memory 16 for storing reconstruction algorithms or correction data, a CRT display 17 for displaying tomographic images, and a control console unit 18. The control console section 18 has a function of outputting operation commands to the mechanism control section 19 or the X-ray control section 20 according to control commands from the CPU 15 or input information from the outside, and according to these operation commands. The mechanism control section 19 controls the rotation mechanism (not shown) of the rotary table 4 or the movement mechanism (not shown) of the C-shaped frame 12, and the X-ray control section 20 controls the X-ray radiation from the X-ray generator 2. Control.

In the apparatus of this embodiment configured as described above, correction data is collected before collecting X-ray projection data of the object 6 to be inspected. When collecting correction data, the C-shaped frame 12 is moved in the direction of arrow A1 and fixed in the state shown in FIG. 2, and the correction test object 3o is placed on the phantom stand 13. At this time, the container 6C of the test object 6 is used as the correction test object 30.
in the same container 30G as the one in which the medium 6b of the object to be inspected 6 is placed.
A medium 30b filled with a medium 30b having the same quality as the above is used, and the object is positioned at a position relatively equal to the position of the object to be inspected 6 with respect to the X-ray beam 1 at the time of collecting projection data of the object to be inspected.

Therefore, outside the imaging area 5, the object to be inspected 6
and the correction inspection object 30 are the same component, and regarding the inside of the imaging area, the inspection object' is composed of the medium 6b and the measurement object 6a.
is filled with the same medium 30b, and the correction test body 30 is filled with only the same medium 30b.

In this state, the CPU 15 operates as shown in FIG.

That is, the control console section 18 is operated to instruct the X-ray control section 20 to emit X-rays, whereby the X-ray beam 1 is irradiated from the X-ray generator 2 to a specific cross section of the correction inspection object 30. Since the projection data of is detected by each detection element of the X-ray detector 3, the data collection unit 14 is operated to collect the projection data from each detection element. Here, since the correction inspection object 30 is axially symmetrical, there is no need to perform a rotational scan when collecting data. When the data collection unit 14 finishes collecting the X-ray projection data from a specific cross section of the correction inspection object 30 (ST1), the collected X-ray projection data of each detection element, that is, the correction data Read Io+ (i-detection element number) (ST2
), logarithmic transformation is performed on each data according to the following equation (1) (ST3).

Xo + -1 oalo I
-(1) After that, the above data value
o+ in a predetermined area of the memory 16 (ST4),
Finish collecting correction data.

Next, the process moves to tomographic imaging processing of the subject 6.

That is, in 1IilJill of mechanism I control section 19,
The C-shaped frame 12 is moved in the direction of the arrow A2 in the figure by hand or by hand, and is positioned in the state shown in FIG. In this state, the CPL 115 operates as shown in FIG. First, the control console section 18 is operated to instruct the X-ray control section 20 to emit X-rays, and as a result, the X-ray generator 2 starts irradiating the X-ray beam 1 onto a specific cross section of the object 30 to be inspected. At the same time, the control console section 18 is operated and the mechanism control section 19 continuously rotates the rotating frame 4 while data collection a! X-ray projection data output from the X-ray detector 3 is collected by $14. In this way, when the rotating frame 4 is rotated once, that is, the X-ray generator 2 and the X-ray detector 3 are scanned once, and each X-ray projection data for a specific cross section of the inspected object 6 has been collected. (ST1
1), these X-ray projection data, that is, scan data 11 (θ) (1-detection element channel number,
θ=rotation angle) (ST12), each data I-+
(θ) is subjected to logarithmic transformation according to the following equation (2) (S T 13).

Xr (θ)=10! llI+ (θ)
(2) Next, using the correction data value Xo+ stored in the memory 16, the following correction calculation is performed for each scan data value X+<θ according to equation 3 (ST14).

X′1 (θ) −Xo t −Xr (θ)
(3) Then, reconstruction processing is performed according to the reconstruction algorithm using these corrected scan data values X'1 (θ), and the X-ray transmittance distribution in the imaging area 5 in a specific cross section of the inspected object 6 is calculated. 5T15), and display this tomographic image on a CRT and display 1.
7 and ends the process (ST16).

In this way, according to this embodiment, even if the imaging area 5 by the X-ray beam 1 is smaller than the area of the specific cross section of the object to be inspected 6, the correction data collected using the correction object 30 can The influence of the portion of the X-ray projection data protruding outside the imaging area on the specific cross section of the object 6 to be inspected is compensated for, and a high-quality tomographic image can be obtained. Therefore, even if the number of detection channels of the X-ray detector 3 is the same as before, the imaging area 5
Since it is possible to make the diameter smaller, resolution can be easily increased at low cost. As a result, the inspected object 6
When it is desired to inspect a measurement object 6a placed in a container 6C via a medium 6b, a tomographic image of the measurement object 6a can be obtained with high resolution by forming the imaging region 5 so as to include only the measurement object 6a. It is more reliable because
5 tests can be carried out. Examples of this type of inspection include, for example, tomographic inspection of substances that require fluid pressurization.

In this case, the test object 6 is a container filled with fluid and the relevant substance, and the correction test object 30 is the same container filled only with fluid.

Furthermore, if the imaging region 5 is formed to include a specific cross section of the object 6 as in the past, Xts absorption is large at the inscribed line of the container 6C, which causes errors in the tomographic image. In this embodiment, since it is possible to scan an imaging area smaller than the inner diameter of the container 6C, it is not affected by the high absorption of the inscribed line, and this type of error can be easily removed.

Note that the present invention is not limited to the above embodiments.

For example, in the above embodiment, the case where an axially symmetrical object is used as the inspected object 6 is shown, but if a rotational scan is performed when collecting correction data, it can be used even if the inspected object 6 is not axially symmetrical. It is possible. Furthermore, if the object to be measured 6a can be removed from the container 6-c as the object to be inspected 6, correction data can be collected while it is removed.
There is no need to prepare the correction test object 30 separately from the test object 6. Furthermore, in the embodiment described above, the X-ray generator 2 and the X-ray detector 3 are disposed facing each other on the rotating frame 4, and by rotating these together, X-ray projection data of a specific cross section of the object to be inspected is obtained. Although the case where the application is applied to an Xl1l CT scanner is shown, the present invention is not limited to this, but is applicable to, for example, a CT scanner in which the object to be inspected 6 is placed on a rotary table and the projection data is obtained by rotating the object to be inspected 6 itself. It's okay.

stomach. Furthermore, radiation is not limited to X-rays. It goes without saying that various other modifications can be made without departing from the spirit of the invention.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to easily compensate for image errors caused by influences outside the imaging area, and to obtain tomographic images with high resolution and good image quality at low cost. We can provide a fault *** device that can do this.

[Brief explanation of the drawing]

1 to 4 are diagrams showing one embodiment of the present invention, in which FIG. 1 is an overall configuration diagram, FIG. 2 is a mechanism layout diagram at the time of collecting correction data, and FIG. 3 is a diagram showing correction data. A flowchart showing the operation of the CPU when collecting scan data, Figure 4 shows the CPU operation when collecting scan data.
FIG. 5 is a flowchart showing the operation of PtJ, and is a diagram showing the configuration of a conventional example. 1...X-ray beam, 2...X-ray generator, 3...X
line detector, 4...rotating frame, 5...imaging area,
6...Object to be inspected, 12...C-type frame, 13...
・Phantom stand, 14...Data collection unit, 15...
CPU, 16...Memory, 17...CRT display, 18...Control console unit, 30...Correction test object. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 4

Claims (1)

[Claims] Radiation is irradiated from multiple directions in a fan shape with a predetermined spread angle to a specific cross section of the object to be inspected, radiation projection data from each direction of this specific cross section is collected, and an image is reconstructed based on the collected radiation projection data. A tomographic image capturing apparatus that performs processing to output a tomographic image based on the radiation transmittance distribution of the specific cross section, comprising a radiation irradiation means that irradiates the radiation from multiple directions to a partial area of the specific cross section of the object to be inspected; Correction data collection means for collecting radiation projection data by irradiating radiation with the radiation irradiation means to a correction inspection object in which the outside of the area is the same component with respect to the imaging region formed in a specific cross section of the object to be inspected by the means. and a data correction means for correcting the radiation projection data of the object to be inspected obtained by the radiation irradiation means based on the correction data collected by this means.