JPS62284250A - Industrial ct scanner - Google Patents

Abstract

PURPOSE:To correct errors of a reconstituted image due to a shift in the position of an X-ray focus by placing a member for correction at a constant position and detecting the position shift of radiation projection data on this correcting member. CONSTITUTION:A cylindrical phantom 10 rotates together with a body 1 to be inspected and a synogram shown in a figure is obtained from X-ray projection data D on it. The center C between both edges A and B of the cylindrical phantom 10 is detected in the center channel of a radiation detector from the 1st projection data D1. When the edges A and B shift in position, the projection data D which causes the shifts is so shifted that the edge center C is positioned in the center channel. The quantity of position shifting of the focus S is calculated from the quantity of shifting. The calculated shift quantity in a direction thetaand the shift quantity in the X-ray irradiation direction are used as data for correction at the time of reconstitution processing.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Object of the Invention 1 (Field of Industrial Application) The present invention relates to an industrial CT scanner used as a non-destructive testing device for industrial products, for example.

(Prior art) A CT scanner obtains projection data by irradiating a specific cross section of an object to be inspected with radiation and measuring the transmitted dose of the radiation, and from this projection data, calculates the cross section of the specific cross section of the object to be inspected. The above-mentioned 1!
I! Information regarding the measurement of the object to be inspected, such as the dimensions, cross-sectional shape, and presence or absence of defects of the object to be inspected, can be obtained.

Therefore, it is popular for industrial or medical purposes.

By the way, CT scanners are classified into different generations depending on the imaging method, and the third generation CT scanner is widely used as an industrial CT scanner for non-destructive inspection of the inside of a product due to its high resolution.

FIG. 7 is a schematic diagram showing the configuration of a scanner mechanism in a conventional third generation CT scanner. The mt* inspection object 1 is placed on a rotary table 3 that can be rotated by a rotation tlltf12, and the X-ray generator 4
and the X-ray detector 5 are arranged to face each other, and the object to be inspected 1 is arranged so as to be included in the spread angle of Xll. The X-ray detector 4 includes X-rays that can pass through the object 1 to be inspected.
X-rays are emitted along a specific cross section of the object to be inspected 1 in a fan shape having a predetermined spread angle, and the emitted X-rays are converted into a fan-shaped xm beam 7 by a collimator 6. Further, the xm detector 5 detects the intensity of arriving X-rays, and is composed of multiple channels of X-ray detection elements each capable of detecting the XII beam 7. Then, the object to be inspected 1 is rotated once, and projection data at this time is collected.

(Problem to be Solved by the Invention) However, in the above-mentioned conventional CT scanner, if the Xra focus of the X-ray generator 4 fluctuates during one rotation of the object 1, this error may be caused again. This resulted in errors in the constituent images, and only images with low resolution were obtained. In particular, the micro-C is suitable for industrial CT scanners because it allows magnified imaging.
Since the T-scanner disposes the rotary table 3 near the xi non-focal point and uses microfocus XJI, the above-mentioned image error due to focus shift has become a big problem. In addition, since the installation of the X1m generator 4 requires high precision, the construction of the scanning system is very complicated (Y work).

Therefore, the present invention can correct the error in the reconstructed image due to the positional shift of the X-ray focal point, and W? Not only can reconstructed images with high resolution be obtained, but the position of the X-ray focal point can also be improved! It is an object of the present invention to provide an industrial CT scanner in which accuracy can be reduced and a scanning mechanism can be easily formed.

[Structure of the invention] (Means for solving the problems) In order to solve the above problems and achieve the purpose, the present invention has the following features:
A radiation source that emits radiation that can pass through the object to be inspected along a specific cross section of the object to be inspected in a fan shape having a predetermined spread angle, and a radiation source that opposes this radiation source and detects the intensity of the radiation that reaches it. and a detector are arranged so that the object to be inspected is sandwiched therebetween and the object to be inspected is included in the spread angle of the radiation, and a correction member that is preset in the vicinity of the object to be inspected is arranged. Then, the data collecting means collects radiation m projection data from multiple directions of the object to be inspected and the correction member using the radiation IF1 radiation detector, and determines the position of the converged radiation projection data of the correction member. Calculating the amount of focal position deviation of the radiation source from the deviation, correcting the radiation projection data of the inspected object collected by the data collection means based on the calculated amount of focal position deviation of the radiation source, and correcting this correction. Image reconstruction processing is applied to the radiographic projection data of the object to be inspected, thereby obtaining a cross section 11 m based on the radiation transmittance distribution of the specific cross section.

(Function) By taking such measures, even if a positional deviation occurs in the focus of the radiation source, this positional deviation is corrected during image reconstruction, and a highly accurate reconstruction process is performed.

(Embodiment) FIG. 1 is a system diagram showing a system configuration of an embodiment of the present invention. The same parts as in Fig. 7 are given the same reference numerals.
Detailed explanation will be omitted. In FIG. 1, 10 is a cylindrical correction member (hereinafter referred to as cylinder),
It is placed on a rotary table 3 so as to enclose the object 1 to be inspected, and rotates together with the object 1 to be inspected.

Note that the radius r and center position (x, y) of this cylindrical phantom 1o have been accurately measured in advance, and the CP
This is input as correction information to U12.

The data collection unit 11 has a function of collecting projection data based on the X-ray intensity detected by each detection element of the X-ray detector 5 in multiple directions of the object to be inspected 1. The data is sent to CPU12. This CPU1
2 is a preprocessing function that converts projection data into input data of a reconstruction algorithm, and an XF
It has a correction function for correcting errors caused by J focus position deviation, and the corrected data is sent to the reconstruction processing unit 13, where the X11 intensity of the specific cross section of the object to be inspected 1 is calculated according to the reconstruction algorithm. A tomographic image is reconstructed based on the distribution. Then, the reconstructed fault is the CP
It is displayed on the CRT display 14 under the control of U and 12.

On the other hand, the console section 15 has a function of outputting operation commands to the X-ray control section 16 and mechanism control section 17 in accordance with commands from the CPIJI2h', etc. The control unit 16 is xI! The one-structure control section 17 controls the X-ray radiation in the generator 4, while the one-structure control section 17 controls the rotation mechanism 2.
It also controls the driving of sectors l1lIll (not shown).

FIG. 2 is a flowchart showing the X-ray focus position deviation correcting means in the CPtJ12. Note that the projection data is collected in exactly the same manner as conventionally, and in this case, X-ray projection data of the object to be inspected 1 and the cylindrical phantom 10 are collected. Now, as step 1, the CPU 12 first inputs the first projection data collected by the data collection unit 11, and as step 2, detects the edge position on the inner circumference of the cylindrical phantom 10 based on the projection data, and This edge position information is stored in memory within the CPU 12. Next, in step 3, the next projection data is input, and in step 4, the inner peripheral edge position of the cylindrical phantom 10 is similarly detected. Then, in step 5, the edge position information detected in step 4 is compared with the edge position information in the first projection data stored in the memory in step 2 (hereinafter referred to as edge position reference information). Then, if both edge position information match, it is determined in step 6 whether all the converged projection data has been input in the data collection unit 11, and if the next projection data exists, the process proceeds to step 3. return.

On the other hand, if the edge position information does not match in step 5, step 7 calculates the deviation amount of the edge position with respect to the edge position reference information, and step 8 shifts the projection data in which the edge deviation has occurred according to the deviation amount. . Next, in step 9, the XS*focal position deviation is calculated and stored according to the amount of deviation of the projection data. That is,
The radius r and the center of the cylinder (x, y) of the cylindrical phantom 10 are accurately measured in advance and used for correction ff! Since the information is input as information, the intersection between the detected edge positions and the inner circumference of the cylinder, that is, the XwA focal position, is determined, and the X-ray focal position in the first projection data and the X-ray focal position of the position shift processing section are determined. The focal position shift position is calculated by When the process of step 9 is completed, the process moves to step 6,
Determine whether data collection is complete.

In step 6, once all the projection data collected by the data collection unit 11 has been input, each projection data is corrected based on the focal position shift position, and the corrected data is sent to the reconstruction processing unit 13. do. In this way, reconstruction processing is performed based on the correction data, and a reconstructed image is obtained. In addition, the data correction mentioned above specifically determines the coefficients of the reconstruction algorithm according to the calculated X-ray focal position, and performs the reconstruction process according to this reconstruction algorithm, thereby obtaining XI! A reconstructed image with the focal position corrected is obtained.

Next, the correction of the positional deviation of the X-ray focal point mentioned above will be specifically explained.

Now, as shown in FIG. 3, it is assumed that X-ray projection data D of the inspected object 1 and the cylindrical phantom 10 rotating in the rotational direction θ are sequentially collected, and a sinobram as shown in FIG. 4 is obtained. . In addition, Fig. 3.

In FIG. 4, A and B are the edge positions of the cylindrical phantom 10, and C is the center of both edges A and B. In the first projection data D1, this edge center C is t!
It is detected by the center channel of the single ray detector 5, and the focal position Is at this time is used as a reference to thereafter correct the focal point S' which has caused a positional shift.

That is, when the edge positions 1fA and 8 are shifted, the projection data D that has caused this shift is shifted so that the edge center C is located in the center channel. The position shift @G at this time becomes G-1 (Δ21 +Δnz/2) in FIG. Note that there is no problem if air data or water phantom data is entered into the undata area that occurs when the projection data D is shifted.

When the projection data D is shifted by the shift amount G, the focus position shift amount is calculated accordingly. That is, as is clear from FIG. 5, the maximum deviation in the θ direction is Δθ.

And the amount of deviation ΔR1 in the XwA irradiation direction is Δθ−−(ΔQ
s+Δβ2/2R2) ΔR1#Rt(ΔQ1−ΔQ2)/2R25in(ψc/2). Thus, the focus position shift amount Δθ.

ΔR1 is used as correction data during reconstruction processing.

In this way, in this embodiment, even if a positional shift occurs in the X1il focus, this positional shift is corrected.

That is, when the xm focal point shifts horizontally, the projection data is shifted laterally, and when it shifts back and forth, it is enlarged or reduced. Then, reconstruction processing is performed using the projection data in which the xsa+focal position has been corrected. Therefore, according to this embodiment, reconstruction processing is performed using projection data obtained with the X-ray focal position always stable, so a reconstructed image with high resolution can be obtained.

This means that the inspection object 1 is placed near the X-ray generator 4,
A great effect can be achieved in a micro-CT scanner that performs tomographic imaging using microfocus X-rays. Further, since the cylindrical phantom 10 rotates together with the object to be inspected 1, rotational deviation of the rotary table 3 is also corrected.

Furthermore, since the initial projection data serves as a reference and the positional deviation of the X-ray focus is corrected sequentially, highly accurate positioning is not required when arranging the X-ray generator 4. Conventionally, it was necessary to set the focal point with an accuracy of a fraction of the focal point size (50μ to 20μ in the case of microfocus X-rays), but in this practical example, a reconstructed image with sufficient resolution can be obtained with an accuracy of about 500μ. It will be done. Furthermore, even if the center of the circle of the cylindrical phantom 10 is not located at the center of rotation of the rotary table 3, this center deviation is automatically corrected as a positional deviation of the focal point, so the positioning accuracy of the cylindrical phantom 10 is high. Not required.

Therefore, the scanning mechanism can be easily formed, and there are fewer restrictions on the installation location, etc.

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

For example, in the embodiment described above, the cylindrical phantom 1o was arranged as a correction member so as to enclose the object 1 on the rotary table 3, but as shown in FIG. A number of (two in this case) rod-shaped correction members, so-called pin phantoms 20.20, are placed in the area, and from the projection data of these pin phantoms 20.20
I! The focal position shift may also be measured. Also,
In this case, the projection data of pin phantom 20.20 is
It may also be detected by an I camera.

Note that at this time, the reconstruction process is performed around the center of rotation of the rotary table 30. Furthermore, in the above embodiment, X'
Although the case where the present invention is applied to an industrial CT scanner that obtains projection data using m is shown, it goes without saying that the present invention can also be applied to an industrial CT scanner that uses radiation other than 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 described in detail above, according to the present invention, it is possible to correct errors in reconstructed images due to positional deviations of the X-ray focus, obtain high-resolution images, and improve XI! It is possible to provide an industrial CT scanner that can easily form a single scan structure while reducing the positional accuracy of the focal position.

[Brief explanation of the drawing]

1 to 5 are diagrams showing one embodiment of the present invention, in which FIG. 1 is a system diagram showing the system configuration, and FIG. 2 is a system diagram showing the system configuration.
a flowchart showing a means for correcting the positional deviation of the X-ray focal point in U;
3 to 5 are diagrams for specifically explaining the correction of positional deviation of the X-ray focus, FIG. 6 is a schematic diagram showing the main part configuration of another embodiment of the present invention, and FIG. 7 is a conventional diagram. FIG. 2 is a schematic diagram showing columns by scan in the industrial CT scanner. DESCRIPTION OF SYMBOLS 1...Object to be inspected, 2...Rotating mechanism, 3...Rotary table, 4...X-ray generator, 5...X-ray detector, 1
0...Cylindrical phantom, 11...Data collection unit, 1
2... CPU, 13... Reconfiguration processing section, 14... CRT display, 15... Console section, 16... Xw
A control section, 17... Mechanism control section, 20... Pin phantom. Applicant's representative Patent attorney Takehiko Suzue No. 1! ! l Figure 4 Figure 5 Figure 7

Claims (3)

[Claims] (1) A radiation source that emits radiation capable of penetrating the object to be inspected along a specific cross section of the object to be inspected in a fan shape with a predetermined spread angle, and the intensity of the radiation that opposes and reaches this radiation source. A radiation detector to be detected, a correction member that is preset in the vicinity of the object to be inspected, the correction member and the object to be inspected being sandwiched therebetween, and the object to be inspected is included in the spread angle of the radiation. a data collecting means for arranging the radiation source and the radiation detector so as to collect radiation projection data from multiple directions of the object to be inspected and the correction member using the radiation detector; a focal position deviation detecting means for calculating a focal position deviation amount of the radiation source from a positional deviation of radiation projection data of the correction member collected by the means; and a focal position of the radiation source calculated by the focal position deviation detecting means. a correction means for correcting the radiation projection data of the object to be inspected collected by the data collection means based on the amount of deviation; and performing image reconstruction processing on the radiation projection data of the object to be inspected corrected by the correction means. An industrial CT scanner comprising: image reconstruction processing means for obtaining a tomographic image based on the radiation transmittance distribution of the specific cross section. (2) Claim (1) characterized in that the correction member on which radiation projection data is collected by the data collection means is a cylindrical body disposed at a position containing the object to be inspected. The industrial CT scanner described. (3) Claim (1) characterized in that the correction member whose radiation projection data is collected by the data collection means is a plurality of rods arranged outside the object to be inspected. The industrial CT scanner described in Section 1.