JP2006189342A - X-ray ct system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray CT system capable of obtaining a magnified tomographic image of higher image quality, as compared with conventionally magnified tomographic images due by means of magnification reconstruction. <P>SOLUTION: In the X-ray CT system, when a region C to be subjected to magnification photographing is designated on the display screen of the preliminarily photographed tomographic image of a subject, a turntable 3 is set to a position, where the minimum gap interposed between the subject W and an X-ray source 1 becomes a predetermined gap, when the turntable 3 is rotated, using the designated content, the shape and dimension of the subject W and the data, related to the position to a rotary axis R and the X-ray detector 2, are positioned so that the designated region in this state becomes a CT photographing region and CT photographing is performed in this state to obtain the magnified tomographic image high in spatial resolving power and density resolving power. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an industrial X-ray for obtaining a tomographic image in order to investigate an internal defect or an internal structure of an industrial product such as an electronic component mounted on a printed wiring board or the like under destruction. The present invention relates to a CT apparatus.

  In an industrial X-ray CT apparatus, generally, a rotary table that rotates around an axis orthogonal to the X-ray optical axis is disposed between an X-ray source and an X-ray detector that are arranged to face each other, and the rotation table is rotated. X-ray transmission data from the X-ray detector is taken in each time the rotary table is rotated by a predetermined minute angle while irradiating X-rays with the subject held on the table. Then, using the acquired X-ray transmission data, a tomographic image of the subject along a plane orthogonal to the rotation axis of the rotary table is reconstructed (see, for example, Patent Document 1). Here, the rotary table is normally movable in the direction of the X-ray optical axis (x-axis direction) and the direction orthogonal to it (y and z-axis directions) by a moving mechanism, and on the rotary table. Also known is an apparatus equipped with an xy stage for moving a subject in two axial directions (x and y axis directions) orthogonal to the rotation axis.

In such an industrial X-ray CT apparatus, in order to obtain a tomographic image obtained by enlarging a partial area of a subject, conventionally, there has been provided a function of enlarging reconstruction and resetting an ROI (region of interest). Is known (see, for example, Patent Document 2). This function is a function for enlarging the region on the screen by digital image processing, for example, by designating the region of interest on a tomographic image that covers the entire area of the subject.
JP 2004-1117024 A JP 10-38819 A

  By the way, the tomographic image enlarged by the above-described conventional enlargement reconstruction function is a tomographic image enlarged by calculation, and the raw data (X-ray transmission data) contributing to the calculation is the same as that before enlargement. . Therefore, the image quality after enlargement reconstruction is inferior. In addition, when an image with a higher resolution of the entire tomographic image having a certain spread is required, simply increasing the imaging magnification narrows the field of view, and the purpose cannot be achieved.

  The main object of the present invention is to provide an X-ray CT apparatus capable of obtaining an enlarged tomographic image with higher image quality than an enlarged tomographic image obtained by conventional enlargement reconstruction.

  Another object of the present invention is to provide an X-ray CT apparatus capable of improving the resolution of the entire tomographic image having an arbitrary spread.

  In order to solve the above-described problems, an X-ray CT apparatus according to the present invention has a subject held between an X-ray source and an X-ray detector arranged opposite to each other, and a rotation axis orthogonal to the X-ray optical axis is centered. And a tomographic image of the subject along a plane orthogonal to the rotation axis using the X-ray transmission data of the subject taken at every predetermined angle while rotating the rotary table. In an X-ray CT apparatus provided with a reconstruction calculation means for reconstructing an image, an enlarged CT imaging area designating means for designating an area to be enlarged on a tomographic image display screen of a subject imaged in advance, and the designated contents And a position where the minimum gap interposed between the subject and the X-ray source becomes a predetermined gap when the rotary table is rotated using information on the shape and size of the subject and the position with respect to the rotation axis. Table / detector positioning for moving the rotary table in the direction of the X-ray optical axis and moving the X-ray detector in the direction of the X-ray optical axis so that the designated area becomes a CT imaging area in that state. It is characterized by comprising means (claim 1).

  Here, in the present invention, an xy stage that mounts a subject and moves on a plane orthogonal to the rotation axis is provided on the rotary table, and the xy stage is designated by the enlarged CT imaging area designation unit. And an xy stage positioning means for moving the center of the formed region so as to be positioned on the rotation axis, and the table / detector positioning means is configured to position the rotary table in a positioning state of the xy stage by the xy stage positioning means. A configuration is adopted in which the rotary table is moved in the X-ray optical axis direction so that a minimum gap interposed between the subject and the X-ray source becomes a predetermined gap when rotated. can do.

  Further, in the present invention, in order to solve the other problems described above, the X-ray CT apparatus according to claim 2 provided with an xy stage, wherein the enlarged CT imaging region designation means displays a tomographic image taken in advance. A plurality of areas to be magnified on the screen can be specified so as to overlap each other and with the same size as each other, and the table / detector positioning means includes the specified contents, the shape of the subject, Using the information regarding the dimensions and the position with respect to the rotation axis, the object and the X-ray source when the rotation table is rotated with the center of each designated region positioned on the rotation axis by the movement of the xy table. The rotary table is moved in the X-ray optical axis direction to a position where the minimum gap interposed therebetween becomes a predetermined gap, and the area of the designated area in that state becomes the CT imaging area. The xy stage positioning means sequentially moves the xy table so that the center of each designated area is positioned on the rotation axis in the positioning state. And an imaging procedure control means for performing CT imaging by rotating the rotary table in each positioning state of the xy table, and X-ray transmission data obtained by each of these CT imaging, respectively. A configuration (Claim 3) including tomographic image synthesizing means for synthesizing the reconstructed tomographic images of the designated areas into one tomographic image can be employed.

  The invention according to claims 1 to 3 further includes image processing means for obtaining information relating to the shape / size of the subject and the position with respect to the rotation axis by image processing using the tomographic image taken in advance. A configuration (Claim 4), or an optical camera that photographs a subject held on the rotary table from a direction substantially parallel to the rotation axis of the rotary table, and using an external appearance image of the subject by the optical camera Any of the configurations (claim 5) provided with image processing means for obtaining information related to the shape / dimension of the subject and the position relative to the rotation axis by image processing can be suitably employed.

  In the inventions according to claims 1 to 5 described above, the positioning of the table / detector is performed when it is geometrically impossible to position the area designated by the enlarged CT imaging area designating means as the CT imaging area. The means is configured to position the rotary table and the X-ray detector at a position where the maximum imaging magnification at which the subject and the X-ray source are closest to each other within a position that can be positioned, and X-rays imaged in that state. It is possible to employ a configuration (enlarged claim 6) provided with an enlargement reconstruction calculation means for enlarging and reconstructing a tomogram reconstructed using transmission data by software.

  In the present invention, by performing the same designation as the conventional ROI (region of interest) designation, the position of the rotary table and the X-ray detector (SOD and SID) with respect to the X-ray source is set so as to make the region a CT imaging region. The X-ray transmission data in the designated area is as high as possible by automatically determining and performing CT imaging at a high imaging magnification with the subject as close to the X-ray source as possible. It is possible to improve the image quality of a tomographic image in a specified region by performing reconstruction calculation using the X-ray transmission data collected with the resolution.

  That is, there are virtually infinite combinations of SOD and SID in which a certain area is a CT imaging area. However, in the present invention, a tomographic image of a subject imaged in advance at an arbitrary imaging magnification is displayed on the display screen. Thus, for example, when a region to be magnified is specified by a circle or the like, the minimum gap interposed between the X-ray source and the subject when the rotary table is rotated based on the information on the shape / size of the subject and the position with respect to the rotation axis. The position of the X-ray detector in the X-ray optical axis direction is determined so that the designated area coincides with the CT imaging area after the rotary table is brought close to the X-ray source until the position becomes a predetermined gap. As a result, CT imaging can be performed under SOD and SID that can obtain X-ray transmission data as large as possible and as bright as possible in the designated area. Therefore, the tomographic image reconstructed using the acquired X-ray transmission data becomes a tomographic image representing the designated area with as high a spatial resolution and density resolution as possible, and is converted into a tomographic image by conventional enlargement reconstruction. Compared with the image quality.

  Further, as in the invention according to claim 2, in the case where the xy stage is provided on the rotary table, a function of automatically moving the xy table so that the center of the designated area is located on the rotary axis. In addition, if the rotary table is positioned at a position where the X-ray source and the subject do not interfere with each other with a predetermined gap in the positioning state of the xy table, the same as the above is achieved without placing a burden on the operator. There is an effect.

  The invention according to claim 3 solves the above-described other problems in addition to the above, and a plurality of designations having the same width and overlapping each other on a display screen of tomographic images taken in advance. A function for moving the xy stage in order so that the center of each designated area is located on the rotation axis (xy stage positioning means) is added, and the rotation table of the rotary table by the table / detector positioning means is added. The positioning is performed at a position where the minimum gap between the X-ray source and the subject is a predetermined gap when the rotary table is rotated while the center of each designated area is positioned on the rotation axis. In other words, even when the designated region closest to the end on the subject is positioned on the rotation axis, the X-ray source and the subject do not interfere with each other and are set to the closest positions. If the tomographic image corresponding to each designated area is reconstructed using the X-ray transmission data obtained by CT imaging with the center of each designated area positioned on the rotation axis, Similar to the above, the tomographic image has as high a space and density resolution as possible. Then, if these tomographic images are combined to construct one tomographic image, the constructed tomographic image becomes a tomographic image having a wide area and high space and grayscale resolution, and solves the other problems described above. can do.

  In the invention according to each of the above claims, the information related to the shape / dimension of the subject and the position with respect to the rotation axis includes the tomographic image on the display screen of the tomographic image taken in advance, which covers the entire area of the subject, for example. The operator may input a circle or the like, or the operator may input an equivalent circle or the like on the appearance image display screen by the optical camera that captures the subject from a direction substantially parallel to the rotation axis of the rotary table. As in the invention according to 4 or 5, the shape / size of the subject and position information with respect to the rotation axis are obtained by image processing using a tomographic image taken in advance or an optical image of the subject taken from a direction substantially parallel to the rotation axis. If it comprises so that it may require, an operator's burden can be eased.

  The invention according to claim 6 has a configuration for dealing with the case where SOD and SID in which the area is a CT imaging area may not be obtained depending on the size of the designated area. Yes. That is, for example, when the operator designates a very small area in relation to the overall size of the subject, the geometric magnification by the apparatus reaches the limit. In this case, in the invention according to claim 6, the designated area However, the rotary table and the X-ray detector are positioned at a position where the maximum imaging magnification is obtained where the subject and the X-ray source are closest to each other within the range that can be positioned, and imaging is performed in that state. By enlarging and reconstructing the tomographic image using the X-ray transmission data by software, it is possible to achieve substantially the same operational effects as the above-described embodiments.

  According to the first and second aspects of the present invention, an enlarged tomographic image of a specified region can be obtained with higher image quality than a tomographic image obtained by conventional enlargement reconstruction.

  According to the invention of claim 3, in addition to the above, a tomographic image of a region having an arbitrary spread can be obtained with high resolution.

  Further, in the invention according to claim 4 or 5, since the apparatus automatically recognizes information on the shape / size of the subject and the position with respect to the rotation axis, in order to obtain a high-resolution tomographic image in each of the inventions described above. The burden placed on the operator can be reduced.

  According to the invention of claim 6, even if an area where the geometric imaging magnification exceeds the limit is specified, the X-ray transmission data obtained by CT imaging under the highest possible magnification is used. Since the tomographic image enlarged by software can be obtained, the operator can set the specified area of any size without considering the limitations on the device when setting the specified area, improving operability To do.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an embodiment of the present invention, and is a diagram illustrating a schematic diagram showing a mechanical configuration and a block diagram showing a system configuration.

  An X-ray detector 2 is disposed opposite to the X-ray source 1, and a rotation table 3 for rotating the subject W is disposed therebetween. The rotary table 3 is rotated about a rotation axis R in the z-axis direction perpendicular to the x-axis direction along the X-ray optical axis L from the X-ray source 1 and is orthogonal to each other by the table moving mechanism 4. It can move in the x, y and z axis directions. The rotary table 3 and the table moving mechanism 4 are driven and controlled by a drive signal supplied from the table controller 11. An xy stage 5 for mounting the subject W and moving it in the x and y axis directions is provided on the rotary table 3. The xy stage 5 is a drive signal supplied from the stage controller 12. Is driven and controlled. Further, the X-ray detector 2 is movable in the x-axis direction, and the position in the x-axis direction can be changed by a drive control signal supplied from the detector position controller 13.

  At the time of CT imaging, the subject W is placed on the xy stage 5 and irradiated with X-rays, is rotated about the rotation axis R, and X-ray transmission data from the X-ray detector 2 is converted into CT for each minute rotation angle. The image reconstruction calculation device 14 takes it in. The CT image reconstruction calculation device 14 uses the 360-degree X-ray transmission data of the subject W acquired in this way, and the subject W sliced along the plane along the xy plane orthogonal to the rotation axis R is used. Build a tomogram. This tomographic image can be displayed on the display 15 via the arithmetic unit 20.

  The computing device 20 is actually composed of a computer and its peripheral devices and operates to realize the functions of the installed program. In FIG. 1, for convenience of explanation, the computing device 20 is installed. It is shown in a block diagram for each function possessed by a program.

  That is, the arithmetic unit 20 was obtained by CT imaging at the initial positions of the rotary table 3 and the X-ray detector 2 as will be described later, in addition to the display control unit 21 that controls the display content of the display unit 15 described above. An image processing unit that obtains information related to the shape and size of the subject W and the position with respect to the rotation axis R by image processing using the tomographic image constructed by the CT image reconstruction calculation device 14 using the X-ray transmission data of the subject W 22 and the rotation table 3 and X based on the information about the shape / dimension of the subject W and the position relative to the rotation axis R obtained by the image processing unit 22 and the enlarged CT imaging region designated by the operator on the tomographic image described above. A table / detector positioning calculation unit 23 for obtaining the position of the line detector 2 in the x-axis direction, and the center of the enlarged CT imaging region designated on the tomographic image by the operator is rotated. An image for synthesizing a plurality of tomographic images reconstructed by the stage positioning computing unit 24 and the CT image reconstruction computing device 13 for obtaining the position of the xy stage 5 so as to be located on the axis R, and synthesizing them into one tomographic image. A synthesis unit 25 and a control unit 16 for controlling the whole are provided.

  In addition, an operation unit 16 including a mouse, a keyboard and the like for connecting the above-described enlarged CT imaging region by the operator and giving other commands to the apparatus is connected to the arithmetic device 20.

Now, the operation of the above-described embodiment of the present invention will be described together with its usage.
First, as shown in a schematic plan view in FIG. 2A, the rotary table 3 and the X-ray detector 2 are positioned at appropriate initial positions, for example, a CT imaging position that can cover the entire area of the subject W. In this state, the subject W is mounted on the xy table 5 and preliminary CT imaging is performed. The CT image reconstruction calculation device 14 reconstructs a preliminary tomographic image Wp using the X-ray transmission data of the subject W obtained by the CT imaging. This tomographic image Wp is displayed on the display 15 via the display control unit 21 of the arithmetic unit 20. An example of the display is shown in FIG. This tomographic image Wp is also captured by the image processing unit 22 and the shape / size of the subject W and the positional relationship with the rotation axis R are obtained.

  The operator designates a region where an enlarged tomographic image is to be obtained on the screen of the display 15 illustrated in FIG. This designation can be performed by a circle C as illustrated in the figure, and its center and size can be set by operating the operation unit 16. The setting status is displayed on the screen of the display 15 together with the tomographic image Wp.

  The table / detector positioning unit 23 of the arithmetic unit 20 uses the setting contents, the shape / dimension of the subject W obtained by the image processing unit 22 and the position information with respect to the rotation axis R to determine the rotation axis R. A position that is as close as possible to the X-ray source 1 without interfering with the X-ray source 1 when rotated about the center, specifically, a minimum gap with the X-ray source 1 when the subject W rotates is set in advance. A position in the x-axis direction of the turntable 3 serving as a gap, and a position in the x-axis direction of the X-ray detector 2 where the designated area C coincides with the CT imaging area at the position of the turntable 3; That is, the position where the X-rays that have passed through the designated region C are incident on the effective width of the X-ray detector 2 without being excessive or insufficient is obtained. In order to realize the position of the rotary table 3 and the X-ray detector 2 obtained in this way in the x-axis direction, the rotary table 3 and the X-ray detector 2 are moved through the table controller 11 and the detector position controller 13 to the x-axis. Move in the direction. The state after the movement is shown in a schematic plan view in FIG.

  After such positioning, the X-ray transmission from the X-ray detector 2 is transmitted to the CT image reconstruction calculation device 14 for each minute rotation angle while rotating the rotary table 3 in accordance with the synchronization signal from the control unit 26. Data is taken and CT imaging is performed. The CT image reconstruction calculation device 14 reconstructs a tomographic image of the subject using the X-ray transmission data. The tomographic image obtained in this way is an X-ray transmission data sampled from the region designated by the operator with the subject W as close to the X-ray source 1 as possible and taken with the maximum magnification and brightness. Therefore, both spatial resolution and pixel density resolution are the highest possible with the apparatus.

  Here, when the center of the enlarged area C designated on the display screen of the tomographic image taken in advance is located away from the rotation axis R as illustrated in FIG. In 24, the xy stage 5 is moved so that the center of the enlarged region C is positioned on the rotation axis R. In the table / detector positioning calculation unit 23, the minimum gap with respect to the X-ray source 1 when the subject W is rotated about the rotation axis R in the state after the movement of the xy stage 5 is a predetermined gap. The rotary table 3 is moved in the x-axis direction so that the X-ray detector 2 is moved in the x-axis direction in the same manner as described above. This state is shown in FIG. When the designated enlarged area C is located at the end of the subject W, the interference with the subject W and the X-ray source 1 causes the X-ray source 1 to be compared with the case where the designated enlarged region C is located at the center. Although the position of the rotary table 3 becomes far, the position of the X-ray detector 2 is moved backward compared to the case where the rotary table 3 is positioned at the center, and the effective width of the X-rays that have passed through the region C is reduced. However, the resolution of the pixel density is lowered as compared with the case where the pixel density is located at the center, but the spatial resolution is not lowered.

  Next, a function for reconstructing a wide area tomographic image such as a tomographic image of the entire subject W with high resolution will be described.

  As illustrated in the display screen of the display 15 in FIG. 4, a plurality of enlarged regions C having the same width are set on the display screen of the tomographic image Wp taken in advance so as to overlap each other. With this setting, the table / detector positioning calculation unit 23 interferes with the X-ray source 1 when the rotary table 3 is rotated in a state where the centers of all the designated areas C are respectively aligned with the rotation axis R. Without moving, the rotary table 3 is moved in the x-axis direction to a position where a preset gap is generated, and the X-rays that have passed through the region are incident on the X-ray detector 2 without excess or deficiency as in the previous example. The X-ray detector 2 is moved in the x-axis direction. Next, the stage positioning calculation unit 24 sequentially moves the xy stage 5 as indicated by an arrow in FIG. 4 so that the center of each designated region C coincides with the rotation axis R, and from the control unit 26. In accordance with the synchronization signal, CT imaging is performed at a position where each designated region C and the rotation axis R coincide with each other, and a tomographic image corresponding to each designated region is reconstructed by the CT image reconstruction calculation device 14.

  Next, the tomographic images corresponding to the designated regions C obtained in this way are synthesized by using the adjacent portions of the images adjacent to each other in the image synthesis unit 25 to obtain one tomographic image. The combined tomographic image is obtained by joining the tomographic images obtained by capturing the designated areas with as high a resolution as possible. Therefore, the resolution was obtained by CT imaging of the entire subject W. Compared with the tomographic image reconstructed using the X-ray transmission data, the resolution of the space and density is significantly higher even if the tomographic image has the same size.

  In the above example, the designated areas C are arranged in a row, but it goes without saying that the designated areas C may be arranged in an arbitrary direction within a plane.

  Here, in each of the embodiments described above, an example is shown in which information relating to the shape / dimension of the subject W and the position with respect to the rotation axis R, and image processing using a tomographic image of the subject taken in advance is shown. The method is not problematic when the cross-sectional shape and dimensions are almost constant at all positions in the z-axis direction, such as a printed wiring board, but the shape and dimensions of the tomographic image change greatly as the slicing position changes. A tomographic image sliced at an arbitrary position cannot be information for the presence or absence of interference with the X-ray source 1. Therefore, in such an apparatus for an object, an optical camera such as a CCD camera that photographs the object from above in a direction substantially parallel to the rotation axis R is arranged, and an appearance image of the object by the optical camera is arranged. The information relating to the shape / dimension of the subject and the position with respect to the rotation axis may be obtained using.

  In addition to obtaining the subject's shape and dimensions and position information with respect to the rotation axis by image processing using the tomographic image or appearance image of the subject as described above, the image is included on the display screen of these images, and The operator may draw a circle whose center coincides with the rotation axis. By moving the rotary table to a position where the rotation axis and the X-ray source are separated by a distance corresponding to the radius of the circle drawn in this way, the subject does not interfere with the X-ray source during rotation, and , The closest position.

  Here, when the enlarged region Wp designated by the operator on the display screen of the tomographic image Wp cannot be matched with the CT imaging region depending on the position of the rotary table and the X-ray detector in the x-axis direction, this situation is For example, this occurs when the region C is extremely narrow. In this case, the rotation table is moved as close to the X-ray source as possible without causing the subject to interfere with the X-ray source, and the X-ray detector CT imaging is performed in a state in which the X-rays that have passed through the region are positioned so as to enter the widest possible range. With such CT imaging, a tomographic image having a size that fills the entire screen for displaying the tomographic image cannot be obtained. In this case, the tomographic image can be enlarged and reconstructed by conventional software. The tomographic image may be enlarged using a technique to fill the entire screen. Although the tomogram obtained in this way has a lower resolution than the magnified tomograms obtained in the previous examples, in the conventional magnified reconstruction technique, for example, a tomogram that covers the entire subject. In contrast to the partial enlargement of the image, in the present invention, since the tomographic image having as high a resolution as possible is enlarged, the resolution is improved as compared with the conventional case.

In the configuration diagram of the embodiment of the present invention, a schematic diagram showing a mechanical configuration and a block diagram showing a system configuration are shown together. It is an operation explanatory view of an embodiment of the invention, (A) is a schematic plan view showing an arrangement state of each member at the time of CT imaging at an initial position, and (B) is a tomographic image taken in that state. It is a figure which shows the example of the condition of designation | designated of the expansion area C on a display screen, Comprising: (C) is a model showing the state which positioned the rotary table 3 and the X-ray detector 2 based on the designated expansion area C. FIG. In the embodiment of the present invention, FIG. 6A is an explanatory diagram when the designated enlarged area C is not located on the rotation axis R. FIG. 5A shows the situation of designation of the enlarged area C on the tomographic image display screen. (B) is a schematic cross-sectional view showing a state in which the rotary table 3 and the X-ray detector 2 are positioned based on a specified enlarged region C. In the embodiment of the present invention, it is an explanatory diagram when obtaining a tomographic image of a wide range of subjects with high resolution, and is a diagram showing an example in which a plurality of regions C are designated on a tomographic image display screen. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray source 2 X-ray detector 3 Rotary table 5 xy stage 11 Table controller 12 Stage controller 13 Detector position controller 14 CT image reconstruction calculation apparatus 20 Calculation apparatus 21 Display control part 22 Image processing part 23 Table and detector positioning Calculation unit 24 Stage positioning calculation unit 25 Image composition unit 26 Control unit W Subject

Claims (6)

Between the X-ray source and the X-ray detector arranged opposite to each other, a rotary table that holds an object and rotates around a rotation axis orthogonal to the X-ray optical axis is arranged, and the rotary table is rotated. An X-ray CT apparatus provided with reconstruction calculation means for reconstructing a tomographic image of a subject along a plane orthogonal to the rotation axis using X-ray transmission data of the subject captured at predetermined angles while
On the display screen of the tomographic image of the subject imaged in advance, the enlarged CT imaging region designating means for designating the region to be magnified, the designated content, the information regarding the shape / dimension of the subject and the position relative to the rotation axis And when the rotary table is rotated, the rotary table is moved in the X-ray optical axis direction to a position where the minimum gap interposed between the subject and the X-ray source becomes a predetermined gap, and the state An X-ray CT apparatus comprising table / detector positioning means for moving the X-ray detector in the X-ray optical axis direction so that the designated area becomes a CT imaging area.   An xy stage that mounts a subject and moves on a plane orthogonal to the rotation axis is provided on the rotary table, and the center of the area designated by the enlarged CT imaging area designating means rotates around the xy stage. An xy stage positioning means for moving the xy stage so as to be positioned on the axis; and the table / detector positioning means is configured such that when the rotary table is rotated with the xy stage positioned by the xy stage positioning means, The X-ray CT apparatus according to claim 1, wherein the rotary table is moved in the X-ray optical axis direction to a position where a minimum gap interposed between the radiation source and the radiation source is a predetermined gap.   The enlarged CT imaging area designating unit is configured to designate a plurality of areas to be enlarged and overlapped with each other on the display screen of a tomographic image of a subject imaged in advance and with the same area. The table / detector positioning means uses the specified contents and information on the shape / dimension of the subject and the position with respect to the rotation axis to move the center of each specified area onto the rotation axis by moving the xy table. The rotary table is moved in the X-ray optical axis direction to a position where the minimum gap interposed between the subject and the X-ray source when the rotary table is positioned and rotated is a predetermined gap, and in this state The X-ray detector is configured to move to a position where the area of the specified area becomes a CT imaging area, and the xy stage positioning means is The xy table is sequentially moved so that the center of each region is positioned on the rotation axis, and CT imaging is performed by rotating the rotary table in each positioning state of the xy table. Procedural control means and tomographic image synthesizing means for synthesizing tomographic images of each designated area reconstructed using X-ray transmission data obtained by each of these CT imagings into one tomographic image. The X-ray CT apparatus according to claim 2, wherein the apparatus is an X-ray CT apparatus.   The image processing means for obtaining information related to the shape / dimension of the subject and the position with respect to the rotation axis by image processing using the tomographic image photographed in advance is provided. The X-ray CT apparatus described.   An optical camera for photographing the subject held on the turntable from a direction substantially parallel to the rotation axis of the turntable, and the shape and shape of the subject by image processing using the appearance image of the subject by the optical camera. 4. The X-ray CT apparatus according to claim 1, further comprising image processing means for obtaining information related to the dimensions and the position with respect to the rotation axis.   When it is geometrically impossible to position the area designated by the enlarged CT imaging area designating means as the CT imaging area, the table / detector positioning means is configured so that the subject and the X-ray source are within the positionable range. The rotary table and the X-ray detector are positioned at a position where the closest imaging magnification can be obtained, and a tomographic image reconstructed using the X-ray transmission data acquired in that state is soft 6. The X-ray CT apparatus according to claim 1, further comprising an enlargement / reconstruction calculation means for enlargement / reconstruction by wear.

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