JPS61155844A - Ct scanner device - Google Patents

Abstract

PURPOSE:To detect a singular part where variation in radiation transmissivity is very small by generating emphasis data by adding the fine variation for an object body having the singular part and then constituting an image. CONSTITUTION:For example, a metallic pipe 55 is irradiated with X rays 23 from the X-ray source 21 of a CT scanner in a fan-beam shape and the X-rays are transmitted. The X rays are detected by an X-ray detector 27 constituted by arranging X-ray detecting elements of plural channels. When the peeling 61 of the metallic pipe 55 is detected, the X-ray transmitted through the internal wall where the peeling 61 occurs are detected by the detecting element of a channel RT and the transmission distance of the X rays in the metallic pipe 55 is long, so its transmission level is low. Fine variation in radiation transmissivity is added to data on the area where the transmissivity is low to generate emphasis data. An image is constituted on the basis of the data to detect peeling correctly. Thus, the radiation transmissivity of the singular part is emphasized, so fine variation is picked up with high resolution.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to an apparatus for obtaining a cross-sectional image of an object to be imaged using radiation such as X-rays, and in particular to a device for obtaining a cross-sectional image of an object to be photographed using radiation such as This invention relates to a CT scanner device that enables detection.

[Technical background of the invention and its problems 1 Computed tomography devices, that is, CT scanner devices, which form tomographic images of objects using radiation such as X-rays, have conventionally been used to obtain tomographic images of human bodies for medical purposes. However, it is useful not only in the medical field but also in other fields for obtaining tomographic images of various objects.

For example, by applying this CT scanner device to industrial use,
When attempting to detect peeling occurring in a fluid transfer pipe made of superalloy or other metal, the measurement system of the apparatus has a configuration as shown in FIG. 3. That is, X
An X-ray detector 27 is arranged to face the X-ray source 21 and the X-ray detector 27 is arranged so as to be able to detect the X-rays 23 outputted from the X-ray source as a fan beam. There is a metal tube 5, which is the object to be imaged, in the X-ray 23 path leading to
5 is placed. At the time of blackout, X-ray source 2
1 to the X-ray detector 27 via the metal tube 55.
7 to collect all around the metal tube 55. Then, the computer system analyzes the X-ray projection data collected by this measurement system over the entire circumference of the metal tube 55, and calculates the X-ray transmittance corresponding to each part of the cross section of the metal tube 55. A gradation level corresponding to the transmittance is given, image information in the cross section of the metal tube 55 is reconstructed, and this is displayed and output as a tomographic image on a CRT display device or the like.

By the way, as shown in FIG.
As for the amount of xm transmission obtained by the detection element of a specific channel RT, the X-ray absorption coefficient of the metal is relatively large, and
Since the distance through which the light passes through the metal tube 55 is the longest, the level of light is extremely low, resulting in a poor S/N ratio. For this reason, there was a problem in that minute changes in X-ray transmittance, especially regarding the peeler 61, could not be detected, and as a result, the peeler 61 could not be detected.

[Object of the Invention] The present invention has been made in view of the above, and its object is to provide a CT scanner device that can obtain a tomographic image at a desired position with high resolution.

[Summary of the Invention] In order to achieve the above object, the present invention provides a CT scanner device that takes a tomographic image of an object to be imaged that has a singular part where the change in radiation transmittance is minute, and applies radiation to the object to be imaged. Detection means 1 detects the radiation transmittance in the cross section of the object by irradiation, and creates data that magnifies and emphasizes minute changes in the radiation transmittance of the singular part based on the detected radiation transmittance data. Emphasis data creation means 3 for
It has an image composition means 5 for creating image composition data constituting the image of the cross section based on radiation transmittance data and emphasis data, and a display means 7 for displaying a singular part based on the created image composition data. The gist is:

[Embodiments of the invention] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 2 shows a CT scanner device according to an embodiment of the present invention, which generally includes a measurement system 51 and a computer system 5.
It is broadly divided into 3.

First, in the measurement system 51, the X-rays 23 emitted or emitted from the X-ray generation source 21 spread in a fan beam shape and pass through the object 25 to be photographed, and a plurality of channels of X-ray detection elements are arranged in parallel. The X-ray detector 27 configured as shown in FIG. The X-rays that spread out like a fan beam and irradiate the subject 25 have a very thin cross-section, so that they are accurately irradiated and transmitted to the cross-section of the subject that is intended to produce an m shadow, and the X-rays are not irradiated. It is now possible to obtain high-resolution tomographic images of cross-sectional areas of objects to be photographed.

The X-ray generator 1121 and the X-ray detector 27 have a rotation and vertical movement control mechanism (not shown), and this mechanism allows the X-ray generator 21 and the X-ray detector 27 to be rotated at a predetermined angle in the same direction on the same plane at the same angular velocity. The X-rays are rotated in increments to accurately irradiate the same cross section of the object 25 from all around the 360° direction. It can be detected by a detector 27. The projection data detected by the X-ray detector 27 is A
The signal is converted into a digital signal by the /D converter 29 and supplied to the computer system 53. In this measurement system 51, a detailed configuration diagram when the object 25 to be photographed and the metal tube 55 are placed one on the other is as shown in FIG.

Next, a computer system 53 that inputs the digital signal and performs signal processing includes a CPU (central processing unit) 35.
, a preprocessing unit 31, a reconstruction unit 33, and an IOP (l10
11 control unit) 37, a main storage device 41, an image data storage device 243, and a console 45 and a CRT display device 47 connected to the further IOP 37.

The preprocessing section 31 performs pre-i2A under the control of the CPU 35.
/ Preprocessing such as offset correction, reference correction, and logarithmic transformation is performed on the projection data converted into a digital signal input from the D converter 29 via the l0P37,
The preprocessed data thus obtained is converted into data representing X-ray transmittance, and is stored at a predetermined address in the image data storage device 143.

The CPLI 35 controls the pass line 39, the preprocessing unit 31, the reconstruction unit 33, and the l0P 37, and directly accesses the image data storage device 43 and main memory bag @41. Also, when creating emphasis data,
Performing arithmetic processing to be described later on the preprocessed data stored in the image data storage device 43 to create emphasis data;
It is stored in another address of the image data storage device 43.

The image composition section 33 receives the preprocessing data and emphasis data from the image data storage @43 under the control of the CPU 35, and performs known convolution processing and pack projection processing on these data. Forming image configuration data for reconstructing image information. This image configuration data is stored in the aIi image data storage device 43 under the control of the CPU 35, and is also supplied to the CR7 display device 45.
A tomographic image is displayed.

Next, the principle of processing for the tree m example will be explained.

First, in the CT scanner device according to this embodiment, a group of projection data obtained by the measurement system 51 for the entire circumference of the object 25, that is, the metal tube 55, is preprocessed by the preprocessing section 31. The preprocessing data is created. This preprocessed data is as shown in FIG. The horizontal axis is the direction of the detection element R of the detector 27 (channel direction: RO to RN), and
Line irradiation angle (projection direction: Oa ~ 360°
) is summarized as a two-dimensional matrix (m+t inogram) with the vertical axis. Therefore, the data on channel R1 in any direction of direction is ! (θ,
R1). That is, this Cynobram is
From the X-ray source 21 that collected data to the XI detector 27
It shows the state of X-ray transmission in the X-ray path leading to.

By the way, one purpose of this embodiment is to detect the peeling 61 generated on the inner wall of the metal IF 55 as shown in FIG. X-ray detector 2 that detects
In the detection element of channel RT No. 7, the distance through which the detected X-rays pass through the metal tube 55 is the longest, so the amount of X-rays transmitted is at a very low level.
Since the rotation is performed by aligning the center of
In the sinobram shown in the figure, regions with particularly low X-ray transmittance are distributed approximately linearly in the projection direction as shown in the figure.

Further, since the tomographic image displayed on the CR7 display device is obtained by converting the difference in X-ray transmittance into grayscale information, the region of low X-ray transmittance in the sinobram is displayed as a dark image. Therefore, even if the peeler 61 exists near the inner wall of the metal tube 55, the difference in X-ray transmittance in this region is relatively very small, so the resolution is poor and it is difficult to detect the peeler 61 from the tomographic image. This makes it difficult.

However, even if the difference in Xa transmittance is small, calculation processing is performed on data in a region with low X-ray transmittance in order to emphasize it, that is, to enlarge the difference in X-ray transmittance. If this is done, the resolution of the tomographic image will be improved and the peeling detection described above will become possible.

Next, regarding the principle of this calculation process in this example,
This will be explained according to FIG.

5) is a concrete representation of the sinobram in FIG. 4 as a two-dimensional matrix. here,
For convenience of explanation, data of each element is expressed by the following formula.

l(θ,RO)−A=(AO,−,An)■(θ,
RT-1) =F= (Fo, ・, Fn) (
(θ, RT )−G= (Go, ・, Gn)■(
θ, RT+l) = H= (llo, −, Hn
) Here, A, . . . , F, G, H, . . . are column vectors, and n is an integer determined by the following equation.

n=360°/(rotation increments) Therefore, on this sinobram, the regions with low X-ray transmittance are column vectors F, G, and H. Therefore, emphasis data is created by performing an arithmetic process of adding five data points in the projection direction to each data of these column vectors FSG1H as shown in the following equation.

fi=Fi-2+r:t-+ +Fi +Fi+l
+Fi+2g1=Gi-2+Qi-1+Qi +Q
i+I +Qi+2hi= Hi-2+ Hi-1+
Hi + Hill + Hi+2 where io
~n Figure 5 (υ) is a matrix representation of the calculation result of the above equation, that is, the emphasized data.
Although points are added, the number of additions can be changed depending on the degree of change in X-ray transmittance. In addition, as a calculation method for creating emphasis data, in addition to the method using addition in the projection direction as shown in the above equation, addition averaging,
A method of emphasizing data changes in the projection direction using differential processing or the like may also be considered.

Next, the created emphasis data is compared with a preset threshold level oth, and data I that exceeds Dth is
It is determined that (θ, R) is data corresponding to the peeler 61 (see FIG. 5(C)). Then, image configuration data for reconstructing the image information of the tomographic image is created from the sinobram of the preprocessed data, and ROI (Regi
on of l ntcr -asting) Create ROI display data that constitutes display information and cut! ! By displaying the ROI on the image, the exact position of the peeler 61 on the tomographic image can be clearly detected.

Here, only data obtained near channel RT of the X-ray detector 27 is processed, but in reality, it is necessary to perform similar processing on channels located symmetrically about the C-axis.

In addition, here we have emphasized data only in the projection direction, but if we create emphasis data in the channel direction or both depending on the shape of the object 25, it will be possible to achieve minute enhancements regardless of the shape. Changes in X-ray transmittance can be detected.

Next, based on the above-mentioned principle, the operation of - in this embodiment will be explained using the flowchart of FIG.

First, the object to be photographed 25, that is, the metal tube 55 is connected to the X-ray source 21.
The X-ray projection data is detected by the X-ray detector 27. X-ray projection data detected by the X-ray detector 27 is converted into a digital signal by an A/D converter 29. The computer system 53 inputs this digitized projection data via the l0P 37 (step 110), preprocesses it in the preprocessing section 31 (step 120), and converts the preprocessed data into image data. Storage device! 43 and create a Cynoblam.

Next, the channel direction R and the projection direction θ with low resolution are input and set in advance on the tomographic image from the console 45, and the corresponding preprocessing data is input on the sinobram stored in the image data storage device 43 according to the above calculation formula. Emphasis data is created by sequential calculations in the CPtJ 35 and stored at another address in the image data storage device 43 (step 130). In the example of the rJa diagram, in the channel direction from the console 45, 8th - 1st, 8th.

Processing will be performed by inputting and setting RTR+. Next, the emphasis data stored in the image data storage device 43 is adjusted to a threshold level D set in advance on the console 45.
th is sequentially compared with the CPU 35, and a data area exceeding oth is detected (step f 140 ). Next, the reconstruction unit 33 reconstructs the @i layer image from the ninogram of the preprocessed data stored in the ship's image data storage device 43 to form image configuration data, and the data on the sinobram exceeding the oth Form ROI display data that configures the ROI display based on the region (step 15
0)9 The formed image configuration data and ROI display data are stored in the image data storage bag @43.

Next, these image configuration data and ROI display data are
It is supplied to the CRT display @47 via 0P37 to display the tomographic image and the ROI on the tomographic image (step 160).

Here, FIG. 7 shows an example of the display on the CRT display device @47 of this embodiment. On the tomographic image 69 of the metal tube, the fi 175 of the peeler is displayed, and the circular ROI 73 or the arrow ROI 71 is displayed. The area around the Hakuri statue 75 is specifically displayed.

Next, FIG. 8 shows a processing flowchart according to another embodiment of the present invention. The configuration of this embodiment is the same as the configuration shown in FIG. 2, so its explanation will be omitted. Next, the operation of this embodiment will be explained.

Data collection process in step 210 and step 2
The preprocessing in step 20 is the same as steps 110 and 120 in the flowchart of FIG. 6, so a description thereof will be omitted.

The emphasis data creation process in step 230 is almost the same as step 130, but here, by inserting the emphasis data into the area where the emphasis data was created on the psynobram of the preprocessed data, another A sinobram is created and stored in the image data storage device M43. Next, the reconstruction unit 33 forms image configuration data for reconstructing a tomographic image from another psynogram including this emphasis data, and stores it in the image data storage device 43 &! I remember.

Next, this image configuration data is transferred to the CRT via l0P37.
The tomographic image is displayed by supplying it to the display device 47 (step 1
60). Here, FIG. 9 shows the CRT display device M4 of this embodiment.
7 shows an example of the display above, a tomographic image 69 of a metal tube
A ring-shaped artifact 77 with a slightly higher density is displayed inside the image, and a portion 79 of the artifact 77 where peeling exists is displayed as an even darker image. This is because the tomographic image is constructed from a sinobram that takes into account the emphasis data, so only the emphasis data area is more X-ray than other parts.
This is because such a ring-shaped artifact occurs because the linear absorption rate increases.

[Effect of the Invention 1] As explained above, according to the present invention, in a CT scanner device that projects a tomographic image of an object to be imaged that has a singular part where the change in radiation transmittance is minute, radiation is not applied to the object to be imaged. The radiation transmittance in the cross section of the subject is detected by irradiation, and based on the detected radiation transmittance data, minute changes in the radiation transmittance of the singular part are magnified by addition to create enhanced data. We created image configuration data that constitutes the image of the cross section based on the transmittance data and emphasis data, and displayed the singular part based on the created image configuration data. It is possible to obtain a tomographic image with high resolution even if the data of the unique part has a poor S/N ratio.

[Brief explanation of drawings]

FIG. 1 is a claim correspondence diagram of the present invention, FIG. 2 is a block diagram of a CT scanner device showing an embodiment of the present invention, and FIG.
The figure shows a detailed configuration diagram of the measurement system in Figure 2, Figure 4 shows the rhinogram of the object to be photographed in Figure 3, and Figure 5 (a) (
υ(C) is a diagram for explaining the process of creating a cynobram and emphasis data, FIG. 6 is an example of a flowchart showing the process of the CT scanner device of FIG. 2, FIG. 7 is an example of the display status of the CR1 display device, FIG. 8 is another example of a flowchart showing the processing of the CT scanner device in FIG.
This is another example of the display status of the display device. 1...Detection means 3...Emphasis data creation means 5...Image composition means 7...Display means Fig. 5(a) Fig. 5(b) Fig. 5(c) Rr4 Rr Ryt+ No. 0m1 47 Figure 18 Figure 91! !

Claims (1)

[Claims] A CT scanner device is used to take a tomographic image of an object to be imaged that has a unique part where the change in radiation transmittance is minute, and the object is irradiated with radiation to detect the radiation transmittance in a cross section of the object. a detection means, an emphasis data creation means for creating data in which minute changes in the radiation transmittance of the singular part are expanded and emphasized by addition based on the detected radiation transmittance data; The above-mentioned CT scanner device, characterized in that it has an image composition means for creating image composition data constituting the image of the cross section, and a display means for displaying a peculiar part based on the created image composition data.