JP2535712B2 - X-ray CT system - Google Patents

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention can use an X-ray TV device (a device that displays an X-ray fluoroscopic image) to perform an inspection by a tomographic image (X-ray CT image) as well as an inspection by a fluoroscopic image of an object. X-ray CT apparatus.

[0002]

2. Description of the Related Art Conventionally, real-time inspection is possible for non-destructive inspection inside a subject such as molded electronic parts.
And because the operation is simple, the X-ray T for observing the fluoroscopic image
V devices are commonly used. However, in the case of a subject having a complicated internal structure or a multi-layered structure, in the above-mentioned perspective image (three-dimensional part is projected two-dimensionally), the portion to be noticed overlaps with other portions, which makes the examination difficult. Become. Therefore, an inspection by an X-ray CT apparatus capable of non-destructively observing a tomographic image of a subject is required.

By the way, there is an industrial CT apparatus as the X-ray CT apparatus, but this CT apparatus is mainly intended for large mechanical parts and the like, and its resolution is insufficient for inspecting small parts such as electronic parts. In addition, there is an inconvenience that it is not possible to perform inspection using a fluoroscopic image, which is sufficient, and has the advantage that real-time inspection can be performed because it is a dedicated CT device.

On the other hand, an inspection system using both a fluoroscopic image and a CT image is being developed for an object such as a small component, but the present system is
It is composed of an X-ray source, an X-ray detector, and a rotating device that accurately positions the center axis of the subject with the accuracy required for tomography and does not cause rotational blur of the subject. I don't like it.

[0005]

SUMMARY OF THE INVENTION The present invention has been in widespread use in the past in view of the disadvantages of the inspection system for the X-ray CT apparatus or both the fluoroscopic image and the CT image. It is intended to observe a CT image together with a transmission image by utilizing.

By the way, since the conventional X-ray TV apparatus is dedicated to the fluoroscopic image, the position of the rotation center axis of the subject does not always coincide with the center position of the X-ray detector, and the subject mounting table is positioned. The accuracy is also insufficient for tomography,
Further, it is composed of a rotating device which is apt to cause rotational shake due to the size, shape and gripping mechanism of the subject. Therefore, in order to perform tomography with the conventional X-ray TV apparatus, it is necessary to replace the object mounting table, the gripping mechanism, and the rotating apparatus with those dedicated to CT, which is an inconvenient operation. It was observed (especially in a small part having an outer diameter of several mm, a slight rotation blur greatly affects the image quality of CT images).

The present invention has been made in view of the above circumstances, and provides an X-ray CT apparatus which is a conventional X-ray TV apparatus which can perform only fluoroscopic inspection and which can perform CT inspection without changing its basic structure. With the goal.

[0008]

In order to achieve the above object, the present invention has an X-ray generator and an X-ray detector which are opposed to each other with a subject interposed therebetween, and rotation control means for the subject and X-ray C for capturing a tomographic image by means for processing the X-ray image transmitted through the specimen
In the T-apparatus, means for detecting the contour position of the subject for each tomographic image extraction site in each direction from the density information of the X-ray image obtained by the image processing means, and the rotation operation of the subject and the true movement from the contour position. A means for detecting the rotation center axis and automatically setting only a necessary reconstruction range is provided, and tomography can be performed without performing highly accurate alignment of the subject.
Then, from the two-dimensional fluoroscopic image obtained by the X-ray detector, the rotational blurring and the rotation center axis are detected from the contour position of the subject for each designated line, and a plurality of tomographic images designated by one rotation of the subject are detected. It is possible to shoot.

[0009]

[Function] Although the contour position of the object differs depending on the object setting,
By setting so that the projection image of the subject is always within the fluoroscopic image, it is possible to detect the rotational movement of the subject center position due to rotational blur. If the rotation angle when the X-axis minimum value of the subject is reached is Θn and the rotation angle when the X-axis maximum value is reached is Θm, the minimum and maximum X-coordinate values Xns of the projection data at the respective positions are given. Xne, Xms, Xme
Represents the contour position of the subject farthest from the true rotation center position. At this time, the X coordinate of the true rotation center position 0 including the object and its gripping mechanism is obtained by the outer peripheral center position ((Xns + Xme) / 2) regardless of the shape of the object. After detecting the rotation center axis, the number of samples S is determined, and f (X ₀ , Θ) to f (X ₀ + S−1, Θ) are used as projection data in the reconstruction process.

[0010]

An embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, an X-ray TV apparatus 1 including an X-ray generator 2 and an X-ray detector 3 for detecting a fluoroscopic image of the subject P, and a rotation control for controlling rotation of a gripping mechanism of the subject P. Device 4, Image input / processing device 5 having image display CRT 6 for executing fluoroscopic images and CT reconstructed images, and personal computer 7 for performing device control, image reconstruction processing, etc. Is attached.

Therefore, the personal computer 7
Is a contour detection device 8 of the subject P, a rotation center axis of the subject P, a reconstruction range setting device 9 for CT (hereinafter, rotation center axis
Reconstruction range setting device), tomographic image reconstruction processing device 1
It includes a control unit such as 0. Further, the grasping mechanism of the subject P uses an electronic component grasping grip.

The rotation control device 4 outputs a rotation output signal of the subject P in response to a rotation input signal from the personal computer 7 so that projection data of the subject P can be collected from all 360 ° directions. There is a step angle rotation mode, and the continuous rotation mode is for setting the position of the subject P and setting the X-ray output, and the rotation angle step can be 1 °, 2 °, etc., and is selected by the step angle setting switch. .

Next, the operation of each device when observing a CT image will be described with reference to the flow chart shown in FIG. Since the optimum value of the intensity of the incident X-ray differs depending on the amount of X-ray absorption of the subject P, the X-ray output is set to the optimum value based on the fluoroscopic density information (step (1)).

Input conditions for projection data are set. The input condition is the area setting required for the perspective image of the projected image,
There are rotation angle steps, the number of projection directions, the number of times of fluoroscopic image integration, etc. (step (2)). The subject P is rotated (steps (3) and (4)), and the image quality deterioration of the fluoroscopic image due to the random noise of the X-ray detector 3 is compensated by the image integration of 10 to 100 times (step (5)). , Projection data with improved SN ratio is stored (step (6)). Note that C
The projection data from each direction required for T is converted from a perspective image into an 8-bit digital value, and its input and basic preprocessing are performed by the image input / processing device 5. One perspective image is 51
The data capacity required for one subject with 2 × 480 pixels depends on the target area, but is 88 MB at maximum when data of the entire screen is collected from 360 directions, and a magnetic disk device or an optical disk device is used.

Even in the same subject, the concentration level varies depending on the site and direction in the structure.
The density of the input image is measured for each tomographic image extraction site in each direction, the contour position of the subject is detected, and the rotation center axis / reconstruction range setting device 9 determines the rotation center axis position and the number of samples S (step ( 7), (8)), the reconstruction range is the object P
Is set in a range X _{0 to} X ₀ + S-1 including all projection data (step (9)), f (X ₀ , Θ) to f (X ₀ )
+ S-1, Θ) is transferred to the reconstruction process (step (1
0)). Note that f (X, Θ) represents the line integral value of the X-ray absorption coefficient of the subject, and Θ represents the projection angle.

The steps (7) to (10) will be described with reference to FIG. When there is no accurate positioning means for the subject and the rotation axis with respect to the position of the X-ray detector 3, the contour position of the subject is different for each subject setting, but the projection image of the subject is set so as to always be within the fluoroscopic image. By doing so, it is possible to detect the rotational movement of the subject center position 0Θ due to rotational blur.

When the rotation angle at which the X coordinate minimum value of the subject is reached is Θn and the rotation angle at which the X coordinate maximum value is reached is Θm, the minimum and maximum X coordinates of the projection data at the respective positions are given. Values Xns, Xne, Xms, Xm
e represents the contour position of the subject farthest from the true rotation center position. At this time, the X coordinate of the true rotation center position 0 including the object and its gripping mechanism is obtained by the outer peripheral center position ((Xns + Xme) / 2) regardless of the shape of the object. After detecting the rotation center axis, the number of samples S is determined, and f (X ₀ , Θ) to f (X ₀ + S−1, Θ) are used as projection data in the reconstruction process. When a one-dimensional line for reconstructing a tomographic image from the two-dimensional fluoroscopic image obtained from the X-ray detector 3 is designated as described above, one line of 500 to 600 pixels is sampled by the image processing apparatus as the maximum sample of projection data per direction. The leading value f (X ₀ , Θ) of the sample and the number of samples S that can be used as the number and are used for the tomographic image reconstruction process are the rotational blur at the end of the rotation depending on the position of the subject, the rotation blur, and the size of the subject. This can be done by detecting and detecting the contour position.

In the tomographic image reconstruction processing device 10, the number of reconstruction matrices is set, the tomographic image is reconstructed by the filter-corrected backprojection processing of the projection data (step (10)), and the image is displayed on the CRT 6 for observation. It is stored (step (11)). The reconstruction processing of the object contour detection device 8, the rotation center axis / reconstruction range setting device 9, the tomographic image reconstruction processing device 10, etc. is executed by software on a personal computer.

[0019]

As described above, according to the present invention, the positioning accuracy of the subject is not required and the tomographic image is taken by automatically detecting the rotational shake and the central axis of rotation from the X-ray image. By using, it is possible to perform CT inspection at a low cost without introducing a new CT dedicated device. In addition, the rotation blur and rotation center axis are detected and corrected for each location where tomographic image capturing is performed using a two-dimensional perspective image, so that the tomographic images of a plurality of designated locations are tilted by one rotation. Even if the above occurs, it can be surely reconstructed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a configuration of the present invention.

FIG. 2 is an explanatory diagram of rotation blurring / rotation center axis detection of a subject.

FIG. 3 is a flowchart showing an operation.

[Explanation of symbols]

 1 X-ray TV device 2 X-ray generator 3 X-ray detector 4 Rotation control device 5 Image input / processing device 6 Image display CRT 7 Personal computer 8 Object contour detection device 9 Rotation center axis / reconstruction range setting device 10 Fault Image reconstruction processor

Front page continuation (72) Inventor Koichiro Otomo 1-90 Tomobuchicho, Miyakojima-ku, Osaka-shi, Osaka Within Kanebo Co., Ltd. No. 90 in Kanebo Co., Ltd. (56) Reference JP-A-2-205759 (JP, A)

Claims (2)

(57) [Claims] 1. An X-ray generator and an X-ray detector are arranged so as to face each other across a subject, and a rotation tomography device for the subject and a processing unit for processing the X-ray image transmitted through the subject capture a tomographic image. X-ray C
In the T apparatus, means for detecting the contour position of the subject for each tomographic image extraction site in each direction from the density information of the X-ray image obtained by the image processing means, and the rotation operation of the subject from the contour position. An X-ray CT apparatus having means for detecting a true rotation center axis and automatically setting only a necessary reconstruction range to enable tomography without performing highly accurate alignment of the subject. . 2. From a two-dimensional fluoroscopic image obtained by an X-ray detector, rotational blurring and a rotation center axis are detected from the contour position of the object for each designated line, and a plurality of objects designated by one rotation of the object are detected. The X-ray CT apparatus according to claim 1, which is capable of capturing a tomographic image.