JPS60190843A - Radiation-tomography scanner - Google Patents

Abstract

PURPOSE:To make it possible to perform highly accurate direct examination, by obtaining the cross-section image based on the difference data between the memorized value of the projection data (PD) of a standard body under examination and the PD of a body under examination, and clearly displaying the difference between the standard sample and the body under examination. CONSTITUTION:A reference sample (body under examination) 31 is mounted on a supporting table 30. X-ray pulses are projected from an X-ray source 22 at every rotation of a specified angle through an X-ray controller 26. The transmitted value of the radiation is detected by each detecting element of a radiation detector 23. The detected signal is processed by a data collector 32 and a preprocessor 33 and stored in a memory 34. Then a body under examination 31 is measured by the same way. The data in the memory 34 is subtracted from the projection data from the preprocessor 33 by a subtractor 36. Operation is performed by a convelver 37 and a back projector 38. The result is imparted to a memory 39, reconstructed and displayed on a CRT display 40. Thus the difference between the standard sample and the body under examination is clearly displayed, and highly accurate examination can be performed.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention performs tomography of a subject using radiation,
Based on this tomographic image, check the shape and dimensions of the object to be inspected,
The present invention relates to a radiation tomography inspection device that can quickly inspect internal defects.

[Technical background of the invention] It is possible to non-destructively inspect the internal defects, composition, structure, etc. of objects.
Moreover, as a device that can measure with high precision, computers
i~Mography scanner (hereinafter referred to as CT device)
There is a radiation tomography inspection device called .

For example, this device is arranged to face the radiation source via a radiation source that emits fan beam X-rays that spread in a flat fan shape and an object to be inspected as a radiation source. Using a detector equipped with a radiation detection element, the radiation source and detector are sequentially rotated in the same direction, for example, over 1800 = 360' in 1 degree increments, centering on the tomographic plane of the object. After collecting X-ray absorption data from multiple directions, a computer etc. perform image reconstruction processing to reconstruct a tomographic image.
Since images can be reconstructed in as many as 00 tones, the condition of the tomographic plane of the object to be inspected can be known in detail.

By the way, in the industrial field, when inspecting products, it is often necessary to check for defects within the product shape and dimensions.

Therefore, in recent years, the use of CT apparatuses has been attracting attention for such inspection purposes. FIG. 1 shows a block diagram of a conventional zero-choice device.

In the figure, 1 is a scanner body, and 2 is an X-ray source that emits fan beam X-rays having a predetermined spread width.

3 is a radiation detector provided facing this X-ray source 2. This radiation detector 3 has a large number of minute radiation detection elements arranged in parallel in the direction of spread of fan beam X-rays, and has a high spatial resolution. It is possible to detect the X-ray intensity from the X-ray source. Here, the X-ray path connecting the X-ray source 2 and each radiation detection element is called an X-ray path, and each radiation detection element
A signal corresponding to the intensity of the t11 ray on the line path is output.

Further, the scanner main body 1 has the above-mentioned X
It has a rotating pedestal that holds a radiation source 2 and a radiation detector 3 facing each other and sequentially rotates and scans them in one direction at predetermined angle increments.

Reference numeral 4 designates an object to be inspected placed in the photographing area of the rotary frame, and reference numeral 5 designates an X-ray controller that controls the tube current, tube voltage, and X-ray exposure of the X-ray source 2. Reference numeral 6 denotes a scanner controller, which controls the rotation of the rotating pedestal of the scanner main body 1. 7 is system controller 1-
It is a roller and controls the entire system. Reference numeral 8 denotes a console, which is used by the operator to give various commands and the like to the system, and is capable of inputting various operation commands and data to the system.

Reference numeral 9 denotes a data acquisition device which receives each radiation detection element signal Ig of the radiation detector 3, performs A/D conversion, and outputs it as X-ray absorption data.

A pretreatment device 10 receives the absorption data for each projection collected by the data collection device 9 and performs preprocessing such as logarithmic transformation, gain correction, and offset data correction on the absorption data. A convolver 11 convolves the preprocessed data output from the preprocessing device 10.

Reference numeral 12 denotes a pack projector which reconstructs a tomographic image by back projecting the convolved data in the direction of its prongs. Reference numeral 13 denotes a memory for storing data of this back-projected reconstructed image, and reference numeral 14 stores CT values in a desired range (data corresponding to the level of radiation absorption) from among the data stored in the memory 13. black and white'fA
This is an image converter that outputs a pale image. A CRT display 15 receives the output of the image converter 14 and displays it as an image.

In such a configuration, the operator first operates the console 8 to start up the system and start scanning (
When photographing is started), the system controller 7 controls the scanner controller 6, controls the rotation of the rotating mount in the scanner body 1 in predetermined angle increments, and also controls the
By controlling the ta controllers 1 to 5, a predetermined tube current and tube voltage are applied to the X-ray source 2 for a predetermined time width every time the rotation is performed in steps of the predetermined angle. From this, the fan beam X-rays FB are sequentially emitted from the xm source 2 in a pulsed manner. An object to be inspected 4 is placed at the center of rotation of the rotating mount (imaging area), and an X-ray source 2 and a detector 3 are mounted on the rotating mount facing each other across the center of rotation. C, the X-ray source 2 emits fan beam X-rays FB while sequentially changing the direction on a predetermined cross section of the object 4 to be inspected, and each X-ray path in this fan beam X-ray FB is The radiation transmission value is detected by each radiation detection element of the radiation detector 3 and converted into an electrical signal.

This converted signal is collected by a data acquisition device 9, and is subjected to logarithmic conversion, gain correction, correction to the offset signal 1, etc. in a preprocessing device 10 for each projection (one motion direction). This processed data (X-ray absorption data in each X-ray pass for each projection) is transferred to the convolver 1
1 and back-projected by the next back projector 12.
The CT value is determined, and the tomogram 19 is reconstructed based on the CT value. The re-imaged image is stored in the memory 13, and by giving commands from the console 8, the image converter 14 converts CT values in a desired range to the CRT display 15 at a gradation level corresponding to the CT values as necessary. to be displayed. This results in
The reconstructed image is displayed as a black and white grayscale image.

Incidentally, an X-ray CT apparatus generally performs comparative measurements between a reference object and a sample. For example, in the case of a medical X-ray machine,
Projection data (X-ray absorption data for each projection direction) from each direction is measured for a water phantom that is approximately the same size as the imaging area (or reconstruction area) (this is called calibration), and then In place of the water fan 1 hem, place the object to be inspected (→non-pull) in the above-mentioned imaging area, record the projection data, and calculate the difference between this projection data and the above-mentioned projection data measured at the time of calibration. and perform reconstruction processing (e.g. convolution and rose projection) from this difference data.
and sieve the tomographic images. Although the tomographic image obtained in this way does accurately show the cross section of the sample,
It was difficult to directly read from the image how it compares to the standard (+l non-pull), that is, what is large, what is small, or whether it is normal.

Therefore, there is a strong desire to develop an apparatus that can perform such inspections at high speed and with high precision.

[Purpose of the Invention] The present invention has been made in view of the above circumstances, and is capable of displaying differences in an object to be inspected with respect to a reference sample more clearly in a CT apparatus using radiation. It is an object of the present invention to provide a radiation tomography inspection apparatus that can inspect images with high precision and intuitively.

[Summary of the Invention] In order to achieve the above object, the present invention includes a radiation source that emits radiation in stages at a predetermined spread angle from each direction to a specific cross section of an object to be inspected, and a radiation source that transmits radiation through the specific cross section of the object to be inspected. A detector that detects the radiation dose in each direction as radiation projection data, and performs image reconstruction processing on the radiation projection data in each direction obtained by this detector to obtain a reconstructed image of a specific cross section of the object to be inspected. (In an apparatus equipped with an image reconstruction unit, a standard data collection mode and a standard data collection mode in which a standard object is used to collect radiation projection data necessary for reconstructing an image of the specific cross section of this standard object; means for setting a measurement mode for collecting radiation projection data on the cross section of the object to be inspected; storage means for storing projection data in each radiation projection direction collected during the standard data collection mode; a reduction means for obtaining difference data between the radiation projection data in the projection direction and the radiation projection data in the radiation projection direction corresponding to the storage means (6); and means for reconstructing based on the difference data. A standard sample with no defects, irregularities in shape, and dimensions is used as a standard test object in the standard data collection mode, projection data of this standard test object is collected and stored in a storage means, and in the measurement mode Collect projection data of a test object of the same standard as the standard test object to be inspected, and from the projection data of this test object, save the above-mentioned standard test object projection data in the same projection direction as the projection data. By subtracting the difference data to obtain difference data and reconstructing the difference data to obtain a tomographic image, images of parts of the object to be inspected that are different from the standard object can be obtained and inspected from this. be done intuitively.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing the configuration of this device. In the figure, 21 is a scanner body, and 22 is an X-ray source that emits fan beam X-rays having a predetermined spread width.

23 is a radiation detector provided facing the X-ray source 2, and this radiation detector 23 has a large number of minute radiation detection elements arranged in parallel in the direction in which the fan beam X-rays spread. The X-ray intensity from the X-ray source can be detected with high resolution. The scanner body 21 also has a rotating mount 24 that holds the X-ray source 22 and the radiation detector 23 facing each other around the shadow area 21a, and rotates and scans them sequentially in one direction at predetermined angle increments. have. ,
Reference numeral 25 designates an object to be inspected placed in the imaging area 21a of this rotary mount 24, and reference numeral 26 designates an X-ray controller that controls the tube current, tube voltage, and X-ray exposure of the X-ray B 22. Reference numeral 6 denotes a scanner controller 1-row, which transmits the rotational force of a drive source M provided in the scanner main body 21 to control the rotation of the rotating pedestal 21a. 28
is the system controller and is in charge of controlling the entire system. A console 29 is used by the operator to give various commands to the system, and is capable of inputting various operation commands and data to the system.

Reference numeral 30 denotes a support base for holding the object to be inspected 31 in the photographing area 21a of the scanner body 21.

Further, 32 is a data collection device, which receives each radiation detection element output signal of the radiation detector 23, and
/D conversion and output as X-ray absorption data. 33 is a pretreatment device that receives the X-ray absorption data for each projection collected by the data collection device 32 and performs preprocessing such as logarithmic transformation, gain correction, and offset correction on the data. . 34 is a memory for storing the X-ray absorption data for each projection collected during the standard data collection mode, and 35 is a switch for switching the data transmission path provided between this memory 34 and the preprocessing device 33. be. By setting the mode on the console 29, this switch 35 is switched to the A@ terminal side in the standard data collection mode and to the B terminal side in the measurement mode under the control of the system controller 1-0-28. The memory 34 is connected to the AI child side and receives and stores the output data from the preprocessing device 33. 36 is a subtracter;
It outputs the difference data between the output data of the preprocessing device 33 given via the B terminal of the switch 35 and the data read out from the memory 34 in the measurement mode, and both input data are of the same projection. It is assumed that the system controller i-roller 28 is controlled to perform subtraction between those at the same X-ray path position so as to obtain the same X-ray path position. A convolver 37 convolves the preprocessed data output from the subtracter 3G. 38 is a pack projector that back-projects the convolved data in the projection direction to reconstruct the GI layer image, and 39 is a memory that stores the data of the back-projected reconstructed image.

Reference numeral 40 denotes a CRT display for displaying the data stored in the memory 39 as an image.Although not shown, between the CRT display 4o and the memory 39, CT values in a desired range of the data stored in the memory 39 are displayed. An image converter is provided for converting the data (data as a value corresponding to the level of radiation absorption) into a video signal of desired gradation or color.

Therefore, the CRT display 4o receives the video signal output from this image converter and displays it as an image.

In such a configuration, an operator first operates the console 8 to start up the system.

This device has a standard data acquisition mode and a measurement mode. First, set the standard data acquisition mode on the console 29, and use this standard data acquisition mode to collect the data of the standard reconstructed image (that is, the data of the standard sample). However, at this time, a standard product with no internal defects or deviations in shape, size, etc. is used as the standard sample as the object to be inspected 31, and a normal measurement operation is performed.

That is, first, a reference sample (subject to be inspected 31) is placed on the support stand 3o, fixed at a fixed position within the imaging area 2Ia, and a standard data collection mode setting command is given from the two consoles. Then system controller 1 - roller 2
8 switches the switch 35 to the A terminal side. Then, when scanning is started (imaging starts) in response to a scan start command from the console 29, the system controller 28 controls the scanner controller 1 and the roller 27, and the scanner body 2
1, the rotary mount 24 is controlled to rotate in predetermined angle increments, and the X-ray controller 26 is controlled to control the tube current and tube voltage for a predetermined time width each time the rotation is performed in the predetermined angle increments. , to the X-ray source 22. From this, the X-ray source 22 sequentially pulses the fan beam X! 'il
FB is exposed. An object to be inspected 31 is disposed at the rotation center position (imaging area) of the rotation mount, and an X-ray source 22 and a detector 23 are mounted on the rotation mount 24 facing each other across the rotation center. Therefore, the X-ray source 22 emits fan beam X-rays FB while sequentially changing the direction on a predetermined cross section of the object 31 to be inspected, and each x1-! in this fan beam X-ray FB! The radiation transmission value of the bus is detected by each radiation detection element of the radiation detector 23 and converted into an electrical signal.

This converted signal is collected by a data acquisition device 32, A/D converted, and subjected to logarithmic conversion, gain correction, offset correction, etc. in a preprocessing device 33 for each projection (in the direction of the fan). .

This preprocessed data (each
XwA absorption data in the line path) is sent to the memory 34 via the switch 35, and is stored in the memory 34 in units of projection. This is standard data collection mode operation.

Next, the console 29 is operated to set the measurement mode.

Further, the object to be inspected 31 is fixed at the fixed position on the support stand 30. That is, if the positions of the object to be inspected and the standard sample are misaligned, accurate measurement cannot be performed, so it is necessary to ensure accurate positioning. For example, a reference surface is prepared for the object to be inspected 31, and measures are taken such as processing it in advance. After preparing in this way, when a measurement mode setting command is given from the console 29, the system controller 1 [''-ra 28 switches the tjJ model 35 to the B terminal side. Then, when a scan start command is given, the same operation as described above is performed, projection data is collected, and after preprocessing is performed, this projection data is applied to the subtracter 36 through the B terminal side of the switch 35. On the other hand, data of the same projection as that projection is read from the memory 34 and input to the subtracter 3G.

Then, the subtracter 3G subtracts the projection data measured in the standard data setting mode from this measured projection data, gives this data to the convolver 37 to perform convolution, and back-projects it by the pack projector 38 and stores it in the memory 39. to reconstruct the image. An example of a reconstructed image is shown in FIG. Solid line A shows the outline of the reference sample,
A broken line B indicates the outline of the object to be inspected. And the shaded part C
The CT value is in the negative area, and the dotted area is C.
The T value is a positive region, and the other region E shows that the CT value is approximately zero.

In other words, at a pixel position that shows the same CT value as the standard sample, the value becomes zero by subtracting the CT value of the test object from the CT value of the standard sample, and if there is a part of the test object at a position that does not exist in the standard sample, the value becomes zero. plus if exists,
If it is the other way around, it will show a negative value, so for example, CR7 is displayed by making the part where the CT value is negative "red", the positive part "yellow", and the zero part "paved blue". By displaying the difference image of the reconstructed image in color on the container 40, you can intuitively understand the missing parts and surplus parts.Of course, you can also distinguish it by displaying it in gradation.This makes it possible to distinguish between standard products and Since the differences between the shapes can be clearly seen, it becomes possible to accurately and easily check for defects in the product and errors in one dimension of the shape.In particular, this CT system is useful for inspecting the cross-sectional shape at a certain position of a sample made of a uniform material. suitable for

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications within the scope of the gist thereof. As explained above, even if the sample is made of non-uniform material, the difference between the reference sample and the reference sample can be displayed by the density.

Further, the difference may be displayed in an emphasized manner as shown in FIG. 4.

In other words, this is an enlarged (exaggerated) display of the difference between the reference sample and the object to be inspected, and the measured image is divided by the error in the direction perpendicular to the outline of the reference sample as shown in Figure 3. This is an enlarged image. By doing this, both cases differ from the actual shape of the object to be inspected, but the features are emphasized and can be grasped intuitively, which is useful for visual monitoring.

In addition, although an X-ray source was used as the radiation source in the above embodiment,
It is not limited to radiation, and other radiation such as gamma rays and neutron radiation can also be used.

Furthermore, the present invention (!) has been explained by taking as an example a so-called third-generation CT device that obtains a tomographic image by rotating and scanning a fan beam, but the first-generation CT device obtains a U1 layer image by traversing and rotating a pencil beam. , 1 ~ Lovers and Roti 1 ~ using a narrow fan beam
It can be applied to all types of CT equipment, including the 2nd generation, which scans to obtain tomographic images, and the 4th generation, in which detection elements are installed all around the object to be examined and only the radiation source that emits a fan beam rotates and scans. be. Further, although the subtraction is performed after preprocessing, it may be performed after convolution or rose projection.

〔Effect of the invention〕

As described in detail above, the present invention includes a radiation source that projects radiation at a predetermined spread angle from each direction onto a specific cross section of an object to be inspected, and a radiation dose in each direction that passes through the specific cross section of the object to be inspected. a detector that detects radiation projection data; and an image reconstruction unit that performs image reconstruction processing on the radiation projection data in each direction obtained by the detector to obtain a reconstructed image of a specific cross section of the object to be inspected. A standard data acquisition mode in which a standard inspection object is used to collect radiation projection data necessary for reconstructing an image of the specific cross section of the standard inspection object, and a radiation projection on the cross section of the inspection object to be inspected. means for setting a measurement mode for data collection; storage means for storing projection data in each radiation projection direction collected in the standard data collection mode; and storage means for storing projection data in each radiation projection direction collected in the measurement mode. A subtraction means for obtaining difference data between one watt and the radiation projection data in the corresponding radiation projection direction from the storage means, and a means for reconstructing based on this difference data are provided, and the standard data collection mode is established. Sometimes a standard sample with no defects or deviations in shape or dimensions is used as the standard object to be inspected.
Projection data of this standard test object (or
(reconstructed data) is collected and stored in a storage means, and in the measurement mode, projection data of a test object of the same standard as the standard test object to be inspected is collected, and projection data of this test object is collected. Is it standard to save the above data in the same projection direction as the projection data? ! ! ! By subtracting the inspection object projection data (or reconstructed data) to obtain difference data, we performed reconstruction based on this difference data to obtain a tomographic image. Since an image showing the difference in CT values of different parts of the object to be inspected can be obtained, the inspection can be performed intuitively, and it is extremely easy to determine whether the object to be inspected is good or bad. In addition, when the material is uniform and its external dimensions are checked, the parts with insufficient dimensions and the parts with excessive dimensions can be measured in the very simple form of CT value 1/+, making it easy to display and judge. In addition, it is possible to provide a radiation tomography inspection apparatus having a feature that visual inspection is made easier by exaggerating the difference between the standard sample and the object to be inspected.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of a conventional CT device;
FIG. 3 is a block diagram showing an embodiment of the present invention, FIG. 3 is a diagram showing a difference image obtained by the present apparatus, and FIG. 4 is an example of an exaggerated display of this image. 1.21...Scanner body, 2,22...X-ray source,
3.23... Radiation detector, 4.24... Subject to be inspected, 5.26... X-ray controller 1-○-ra, 6.27...
Scanner controller, 7, 28... System controller, 8, 29... Console, 9, 32... Data collection device, 10, 33... Preprocessing device, 11.3
7...Convolver, 12.38...Pack projector, 13.34.39...Memory, 15.40...
・CRT display, 24... Rotating frame, 35... Switching device, 36... Subtractor. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 - ``-Mun°L: Nyama - November 1986, 4°rj 6[-1 1, Uma'1 Office] Government shi t″1 Gaku-dono 1, $Ime 1’s entry L’J Tori I It! ! b 9 27 II 36'
;32, Name of the invention: J-layer I blueprint inspection device in Bokuyo Line 3, N]1j11? 1 sun; I-Wl clerk with Ino 1 1, 'I revised filing 2 applicant (307) All stocks Toshiba 4, agent inquiry office Higashiri J no Miyako 1-A Toranomon 1-26 Kaori 5 > Shi No. 17 Mori Hill 6, Supplementary Subject Akira 41 + 1, l Near, Nshi iI■ Contents (1) [Prescribed tube current,
... 111 interval width -1 is corrected as [predetermined tube current 2 tube current is predetermined time opening width -1]. (2) Detailed demand No. 6 to No. 10? "From this" written in the jth column
1 This is corrected and overturned as J, Su, 1. (3) 1 to 1 described in Specification 8th Chapter 2 fjll [this] Supplement 11
- Is there a way to calibrate the data so that the data values are as they should be? After that, then 1dom J iF 3゜(
4) Specification younger brother 8 Tei No. 5 < jth to same page No. 7 f = ith or 1: 11.'l L2 measurement of JC described... The construction process J and U are the supplementary J1-(
Detective, fix it. Therefore, the second part of this supplement will be corrected to ``Image composition processing''. (5) Specification page 6, No. 9 or 1) ``Correct the 1 mark tel rinzo described in C- to 1 [the 1 mark telinple written in J.

Claims (1)

[Claims] a radiation source that projects radiation with a predetermined spread angle from each direction onto a specific cross section of the object to be inspected; and a detector that detects radiation doses in each direction that have passed through the specific cross section of the object to be inspected as radiation projection data; , J3 is installed in an apparatus equipped with an image reconstruction unit that performs an image reconstruction process on the radiation projection data in each direction obtained by this detector to obtain a reconstructed image of a specific cross section of the object to be inspected. A standard data collection mode in which radiation projection data necessary for reconstructing an image of the specific cross section of the standard object is collected using the inspection object, and a measurement mode in which radiation projection data is collected in the cross section of the object to be inspected. a storage means for storing the projection data of each radiation projection direction collected in the standard data collection mode; and a storage means for storing the radiation projection data of each radiation projection direction collected in the measurement mode and the What is claimed is: 1. A radiation tomography examination apparatus comprising: subtraction means for obtaining difference data from radiation projection data in a radiation projection direction corresponding to the radiation projection direction; and means for performing reconstruction based on this difference data.