JP2013015426A - Radiation ct system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray CT system which is capable of capturing a sharp and high-magnification tomographic image.SOLUTION: Pre-photographing is performed for photographing a phantom at a placement position on a table 2, thereafter, actual photographing is performed for photographing a sample by moving the table 2 and a detector 3 in the same manner as pre-photographing, and a tomographic image is reconstituted. A reconstitution section 10 is capable of considering the moving manner of the table 2 in capturing an actually photographed X-ray image Q. However, the table 2 is not always moved in the same manner in pre-photographing and actual photographing. Then, a marker on a rear side of the table 2 is photographed and position deviation of the table 2 incurred between pre-photographing and actual photographing is recognized from an actually photographed marker image N and a pre-marker image M. As a result, an X-ray CT system capable of capturing a high-resolution tomographic image can be provided.

Description

  The present invention relates to a radiation CT apparatus that performs tomography by irradiating an examination target with radiation, and more particularly to a radiation CT apparatus in which a table on which a specimen to be examined is placed is movable.

  In factories and the like, radiation CT apparatuses that perform tomography by irradiating a subject with radiation are provided. As shown in FIG. 20, the radiation CT apparatus includes a radiation source 53 that irradiates radiation, a table 52 on which a sample to be inspected is placed, and a detector 54 that detects radiation. A radiation source 53 is provided below the table 52 placed horizontally, and a detector 54 is provided above the table 52 (see, for example, Patent Document 1).

  The detector 54 can move along a virtual circle belonging to a plane parallel to the table 52. The table 52 is moved in the X direction perpendicular to the vertical direction by the XY stage provided in the table 52, and the vertical direction. Move in the Y direction orthogonal to the direction / X direction.

  The tomographic image to be inspected is acquired by first performing radiography of the sample W to be inspected a plurality of times from different directions, and then reconstructing the plurality of images obtained. In order to perform multiple imaging from different directions, it is necessary to perform multiple imaging while changing the positions of the radiation source 53 and the detector 54 with respect to the sample W. Some conventional radiation CT apparatuses are configured to fix the radiation source 53. In such an apparatus, instead of moving the radiation source 53 and the detector 54 with respect to the sample W, the detector 54 and the sample W are moved with respect to the radiation source 53.

  Therefore, when photographing the sample W from different directions, the sample W is moved relative to the radiation source 53 in synchronization with the movement of the detector 54 along the virtual circle. The movement of the sample W is realized by moving the table 52 in the X and Y directions by the XY stage. The movement of the detector 54 and the table 52 relative to the radiation source 53 during tomographic imaging is a strictly defined circular motion.

  If the movement of the table 52 is not accurate, a clear tomographic image cannot be acquired. If the movement of the table 52 during tomographic image shooting deviates from the specified trajectory, the tomographic image acquired is blurred as if the sample W on the table 52 moved during shooting. In the conventional configuration, a linear encoder is provided on the XY stage that drives the table 52 in order to prevent the positional shift of the table 52 that causes such blurring of the tomographic image so that the table 52 can be moved accurately. ing.

JP 2005-106515 A

However, the conventional radiation CT apparatus has the following problems.
That is, in the conventional radiation CT apparatus, a clear image cannot be acquired in a high-magnification tomographic image.

  When the tomography is performed, if the movement of the table 52 is slightly deviated from the predetermined locus, the position of the radiation image of the sample W projected on the detector 54 is largely deviated from the original position. Since the radiation source 53 radiates the radiation radially, the image of the sample W placed on the table 52 is enlarged and projected onto the detector 54. Therefore, the positional deviation of the sample W on the table 52 is also enlarged and appears on the detector 54. This is the reason why the radiation image is largely shifted due to a slight shift of the movement of the table 52.

  Such a shift of the radiation image becomes a problem especially when trying to acquire a high-magnification tomographic image. This is because the influence of the position shift of the table 52 is relatively large in a high-magnification tomographic image.

  In a conventional radiation CT apparatus, a high-magnification tomographic image cannot be obtained clearly. This is because the accuracy of the amount of movement of the XY stage that drives the table 52 is limited.

  The present invention has been made in view of such circumstances, and its purpose is to obtain a clear high-magnification tomographic image even if the sample cannot be accurately moved with respect to the radiation source. An object of the present invention is to provide a radiation CT apparatus capable of performing the above.

The present invention has the following configuration in order to solve the above-described problems.
That is, the radiation CT apparatus according to the present invention includes a sample placement table having a back surface and a front surface having markers, a radiation source that irradiates radiation from one surface to the table, and the table to the radiation source. A table moving means for moving the table, a table moving control means for controlling the table moving means, a radiation detector provided on the other surface side of the table for detecting radiation transmitted through the table, and the radiation detector as a radiation source. Detector moving means for moving the detector, detector movement control means for controlling the detector moving means, and imaging the marker on the back surface of the table with visible light each time a radiographic image is taken, and outputting a detection signal Based on the detection signal output from the optical camera and the radiation detector, the table and radiation to the radiation source with the calibration subject placed at the mounting position of the table By moving the detector, a series of pre-radiation images are generated in pre-photographing in which the subject is photographed one after another while changing the photographing direction, and the table and radiation detector are preliminarily placed with the sample placed on the table mounting position. Pre-imaging based on image generation means that generates a series of actual radiographic images in actual imaging where the sample is captured one after another while moving in the same manner as imaging, and detection signals output by the optical camera A series of pre-marker images in which the markers are reflected in the optical image generation means for generating a series of actual shooting marker images in which the markers are reflected in the actual shooting, and the pre-shooting by the actual shooting marker images and the pre-marker images The table position difference between the actual image and the actual image is recognized and a series of pre-radiation images are used. It recognizes the style of the movement of the photographing table and is characterized in that it comprises a reconstruction means for reconstructing a tomographic image based on a series of actual photographing a radiation image.

  [Operation / Effect] According to the present invention, the subject and the radiation detector are moved one after another while changing the imaging direction by moving the table and the radiation detector with respect to the radiation source in a state where the calibration subject is placed at the table mounting position. After performing the pre-photographing, the table and radiation detector are moved in the same manner as the pre-photographing to perform the actual photographing of photographing the sample one after another while changing the photographing direction, and a series of pre-radiation images and a series of The tomographic image is reconstructed based on the actual radiographic image. The reconstruction means recognizes the movement mode of the table and the radiation detector at the time of imaging based on the pre-radiation image prior to actual imaging. If a tomographic image is reconstructed based on a series of actual radiographic images, it is possible to consider the manner of movement of the table and the radiation detector at the time of capturing the actual radiographic images. Can be obtained.

  However, this method has drawbacks. That is, the table does not always move in exactly the same way in pre-photographing and actual photographing. Therefore, according to the present invention, the marker is provided on the back surface of the table. This marker is photographed by the optical camera between pre-photographing and actual photographing. The reconstruction means is configured to detect a positional deviation of the table generated between the pre-photographing and the actual photographing based on the actual photographing marker image obtained by the real photographing and the premarker image obtained by the pre-photographing when the tomographic image is reconstructed. recognize. Then, the reconstruction unit generates a tomographic image of the sample in consideration of this positional deviation. According to this configuration, the reconstruction unit can accurately know the position of the table in actual photographing even if the table movement pattern differs between pre-photographing and actual photographing. As a result, a radiation CT apparatus capable of acquiring a high-resolution tomographic image can be provided.

  Further, in the above-described radiation CT apparatus, position variable acquisition means for acquiring, for each pre-radiation image, a position variable indicating a position of a table with respect to the radiation source based on a series of pre-radiation images, an actual imaging marker image, and a pre-marker image. Collation and acquisition unit for acquiring a deviation amount indicating the positional deviation of the table in pre-imaging and actual imaging for each actual imaging marker image, and correcting a position variable based on the deviation amount, and a radiation source in actual imaging It is more desirable that the position variable correction means for acquiring a correction position variable indicating the position of the table for each position variable and the reconstruction means reconstruct a tomographic image using a series of actual radiographic images and correction position variables.

  [Operation / Effect] The above-described configuration shows a specific configuration of the radiation CT apparatus of the present invention. That is, a position variable indicating the state of movement of the table is acquired by pre-imaging, the actual shooting marker image and the pre-marker image are collated, the position variable is corrected to obtain a corrected position variable, and the reconstructing means acquires the corrected position variable. Therefore, the reconstruction means can generate a tomographic image taking into account the position of the table in actual imaging even if the table movement pattern differs between pre-imaging and actual imaging. it can.

  In the above-mentioned radiation CT apparatus, it is more desirable that a marker is provided on the entire back surface of the table.

  [Operation / Effect] The above-described configuration shows a specific configuration of the radiation CT apparatus of the present invention. That is, if the marker is provided on the entire back surface of the table, the optical camera can reliably photograph the marker no matter how the table moves.

  In the above-described radiation CT apparatus, the table includes a frame-shaped peripheral member and a central plate that is housed inside the peripheral member and is detachable from the peripheral member. The optical camera is photographed at a time point before the center plate is removed from the peripheral member and a time point after the central plate is removed from the peripheral member and accommodated again. It is more desirable if the mark image is acquired and the reconstruction means reconstructs the tomographic image of the sample by recognizing the positional change between the peripheral member and the center plate before and after the center plate is attached and detached based on the mark image.

  [Operation / Effect] The above-described configuration shows a specific configuration of the radiation CT apparatus of the present invention. In the radiation CT apparatus, the table may be removed from the apparatus for the purpose of maintenance. If the table is detached from the apparatus after the pre-photographing and before the real-photographing, the table position in the real-photographing cannot be accurately calculated even if the real-photographed marker image and the premarker image are collated. Therefore, in the above configuration, it is possible to know how much the position of the table has shifted before and after the table is attached and detached. That is, the table is composed of a removable central plate and a non-detachable peripheral member so that it can be known how much the central plate has moved from the peripheral member before and after the central plate is attached and detached. By doing so, the position of the table in the actual photographing can be accurately calculated even if the central plate is attached and detached after the pre photographing and before the actual photographing.

  Further, in the above-described radiation CT apparatus, a sample mounting plate on which a sample is mounted is provided on the front side of the table, a sample mounting plate moving means for moving the sample mounting plate with respect to the table, and the sample The sample mounting plate can be moved to the position where the calibration object on the table is mounted by controlling the sample mounting plate moving means prior to capturing the tomographic image of the sample. It is more desirable to provide movement control means.

  [Operation / Effect] The above-described configuration shows a specific configuration of the radiation CT apparatus of the present invention. The mode of table movement differs depending on which part of the table the tomographic image is taken. Therefore, according to the above-described configuration, there is a configuration in which the imaging portion of the sample is moved to the position on the table where the calibration subject is placed. By configuring in this way, a radiation CT apparatus capable of acquiring a high-resolution tomographic image can be provided.

  According to the present invention, after pre-photographing a subject at the table mounting position, a tomographic image is obtained by moving the table and the radiation detector in the same manner as the pre-photographing and performing real-photographing of the sample. It is a configuration to reconfigure. The reconstruction means can take into account the manner of movement of the table and the radiation detector when capturing the actual radiographic image. However, this method has drawbacks. That is, the table does not always move in exactly the same way in pre-photographing and actual photographing. Therefore, according to the present invention, the marker on the back surface of the table is photographed, and the positional deviation of the table generated between the pre-photographing and the actual photographing is recognized from the premarker image. As a result, a radiation CT apparatus capable of acquiring a high-resolution tomographic image can be provided.

1 is a functional block diagram illustrating a configuration of an X-ray CT apparatus according to Embodiment 1. FIG. It is a top view explaining the back surface of the table which concerns on Example 1. FIG. It is a perspective view explaining the movement of the table concerning Example 1, and a detector. It is a top view explaining the movement of the table which concerns on Example 1. FIG. 6 is a schematic diagram illustrating a marker image according to Embodiment 1. FIG. 1 is a perspective view illustrating a phantom according to a first embodiment. 6 is a schematic diagram illustrating pre-shooting according to the first embodiment. FIG. FIG. 6 is a schematic diagram illustrating actual photographing according to the first embodiment. 6 is a schematic diagram illustrating a marker image according to Embodiment 1. FIG. FIG. 6 is a schematic diagram illustrating a position variable correction operation according to the first embodiment. 3 is a flowchart illustrating the operation of the X-ray CT apparatus according to the first embodiment. It is a functional block diagram explaining the structure of the X-ray CT apparatus which concerns on Example 2. FIG. 6 is a plan view illustrating a configuration of a sample mounting plate moving mechanism according to Embodiment 2. FIG. It is a schematic diagram explaining the structure of the X-ray CT apparatus which concerns on Example 2. FIG. It is a schematic diagram explaining the structure of the X-ray CT apparatus which concerns on Example 2. FIG. It is a schematic diagram explaining the structure of the X-ray CT apparatus which concerns on Example 2. FIG. It is a perspective view explaining 1 modification of this invention. It is a top view explaining one modification of the present invention. It is a mimetic diagram explaining one modification of the present invention. It is a schematic diagram explaining the conventional structure.

  Hereinafter, each embodiment of the present invention will be described. The X-rays in each example correspond to the radiation of the present invention.

<Overall configuration of X-ray CT apparatus>
FIG. 1 shows the overall configuration of the X-ray CT apparatus according to the first embodiment. As shown in FIG. 1, the X-ray CT apparatus includes a table 2 on which a sample W is placed, an X-ray generator 1 that irradiates X-rays provided below the table 2, and an upper side of the table 2. The detector 3 for detecting the X-rays and the optical camera 7 provided on the lower side of the table 2 are provided.

  The table 2 has a rectangular shape parallel to the floor of the work room. Each side of the table 2 extends in either the vertical direction (Y direction) or the horizontal direction (X direction). The table 2 has a front surface on which the sample W is placed and a back surface that is the opposite surface. The front surface of the table 2 faces the detector 3, and the back surface faces the X-ray generator 1 and the optical camera 7. The specific size of the table 2 is, for example, 50 × 50 cm. The X direction, the Y direction, and the vertical direction are orthogonal to each other.

  FIG. 2 is a plan view showing the back surface of the table 2. Markers m are arranged in a two-dimensional matrix along the Y direction and the X direction on the entire back surface of the table 2. The marker m is photographed by the optical camera 7 that photographs the back surface of the table 2.

  The detector 3 emits X-rays emitted from the X-ray generator 1 and transmitted through the table 2 to detect X-rays. Specifically, an image intensifier is used for the detector 3.

  The XY moving mechanism 6 (XY stage) is provided for the purpose of moving the table 2 in the X direction and the Y direction with respect to the X-ray generator 1. By the movement of the XY movement mechanism 6, the table 2 moves on a plane extending the rectangular table 2. The XY movement control unit 16 b is provided for the purpose of controlling the XY movement mechanism 6. The detector moving mechanism 5 is provided for the purpose of rotating the detector 3 relative to the X-ray generator 1. The detector movement control unit 16 a is provided for the purpose of controlling the detector movement mechanism 5.

  The X-ray CT apparatus performs X-ray imaging a plurality of times while changing the imaging direction of the sample W placed on the table 2, and acquires a tomographic image by reconstructing the obtained image. Therefore, in the X-ray CT apparatus, the X-ray generator 1 and the detector 3 move with respect to the sample W during imaging. Actually, the imaging direction of the sample W is changed by moving the sample W of the detector 3 and the table 2 with respect to the X-ray generator 1.

  FIG. 3 shows how the table 2 and the detector 3 move when the X-ray CT apparatus takes a tomographic image. When taking a tomographic image, as shown in FIG. 3, the detector 3 is rotationally moved about a central axis extending in the vertical direction from the X-ray generator 1. At this time, the orientation of the detector 3 with respect to the central axis is fixed, and one side of the detector 3 facing the central axis is always the same. This rotational movement is realized by the detector moving mechanism 5. In synchronization with the rotational movement of the detector 3, the table 2 is also rotationally moved around the central axis extending from the X-ray generator 1 in the vertical direction. This rotational movement is realized by the XY moving mechanism 6. In FIG. 1 and FIG. 3, the normal line set at the center of the detection surface of the detector 3 is in the vertical direction (the detector surface is horizontal), but the normal line set at the center of the detection surface of the detector 3. May be arranged so as to face the X-ray generation point of the X-ray generator 1.

  FIG. 4 illustrates the rotational movement of the table 2 when taking a tomographic image. As shown in FIG. 4, the XY moving mechanism 6 rotates the table 2 so that each vertex of the table 2 draws an arc while keeping the four sides of the table 2 parallel to the X direction or the Y direction. Move.

  The optical camera 7 captures the back surface of the table 2 with visible light and outputs a detection signal. A sufficient number of markers m are provided on the back surface of the table 2, and the markers m are always reflected in the field of view of the optical camera 7 that photographs the back surface of the table 2. Even if the table 2 is rotationally moved with respect to the X-ray generator 1, any of the markers m provided on the table 2 is always reflected in the field of view of the optical camera 7.

  When the optical camera 7 captures the back surface of the table 2, a detection signal is output to the optical image generation unit 12. The optical image generation unit 12 generates a marker image in which the marker m is reflected based on this detection signal. As shown in FIG. 5, the marker image includes a plurality of markers m.

  The image generation unit 8 generates an X-ray image in which a fluoroscopic image of the subject is reflected based on the detection signal output from the detector 3. The reconstruction unit 10 reconstructs a tomographic image based on a plurality of X-ray images generated by the image generation unit 8.

  The X-ray control unit 11 is provided for the purpose of controlling the X-ray irradiation of the X-ray generator 1. The console 17 is provided for the purpose of inputting an operator's instruction to the X-ray CT apparatus. The display unit 18 displays a captured tomographic image. The storage unit 9 stores all information necessary for tomographic image capturing such as a marker image. The main control unit 27 is provided for the purpose of comprehensively controlling each control unit. The main control unit 27 is constituted by a CPU, and realizes the control units 11, 16a, 16b and the units 8, 10, 12, 21, 22, 24 by executing various programs. Each of the above-described units may be divided and executed by an arithmetic device that takes charge of them. The operations of the position variable acquisition unit 21, the position variable correction unit 22, and the deviation amount acquisition unit 24 will be described later.

<Meaning of position variable>
The X-ray CT apparatus of the present invention uses the concept of position variables for the purpose of acquiring a high-resolution tomographic image. When tomographic imaging starts, a plurality of fluoroscopic images are acquired while the table 2 and the detector 3 are rotated. Each of the fluoroscopic images is taken with the positions of the tables 2 being different from each other. The position variable is a variable that indicates how the position of the table 2 specifically differs among the fluoroscopic images. In the present invention, 100 fluoroscopic images are generated while the table 2 and the detector 3 rotate once, so that the position variable is acquired for each of the 100 fluoroscopic images. However, in the following description, an example in which a tomographic image is reconstructed from 100 fluoroscopic images has been described. However, the number of tomographic images to be used can be arbitrarily determined by the operator, and the present invention. Is not limited to 100 sheets.

  Specifically, the position variable is a data set including about five parameters independent of each other. Comparing the position variables of two different fluoroscopic images among 100 consecutive fluoroscopic images, the position of the table 2 when one fluoroscopic image is taken is the same as when the other fluoroscopic image is taken. It can be seen how much the direction differs from the position of the table 2 in which direction.

  The present invention is configured to reconstruct 100 X-ray images and generate a tomographic image. At this time, the position variable is obtained every time 100 X-ray images are acquired. With the position variable corresponding to the X-ray image, the shooting direction of the subject when this X-ray image is shot can be accurately determined. If a tomographic image is generated in consideration of this accurate imaging direction, a tomographic image with higher resolution can be acquired.

  A generally used method for generating a tomographic image does not acquire a position variable. That is, in this method, the subject is photographed while rotating the table 2 and the detector 3 to obtain 100 perspective images, and a tomographic image is generated based on the perspective images. In this method, since the table 2 and the detector 3 are controlled so as to rotate along a perfect circle, it is assumed that each perspective image is taken from a predetermined direction obtained by geometric calculation. Perform reconfiguration.

  However, in reality, the table 2 and the detector 3 are not completely rotated along a perfect circle because of the accuracy of the moving mechanism. In a general method, this is ignored and the tomographic image is reconstructed. Therefore, in this method, the tomographic image is reconstructed on the assumption that the subject is photographed in the ideal photographing direction even though the actual photographing direction of the subject is deviated from the ideal direction. Then, a high-resolution tomographic image cannot be acquired.

  In the present invention, since the position variable is acquired and the actual photographing direction is determined by each fluoroscopic image for reconstruction, a high-resolution tomographic image can be acquired. The position variables necessary for the determination of the actual photographing direction are 100 sheets obtained by photographing the calibration phantom in the same manner as the photographing of the sample with the calibration phantom placed in place of the sample W on the table 2. Is generated based on the fluoroscopic image. That is, in the present invention, position variables are acquired in advance by photographing with a calibration phantom, and then 100 specimens are photographed by placing the actual sample W on the table 2. The tomographic image of the sample W is generated based on the fluoroscopic image obtained by photographing the sample W (actual photographing) and the position variable obtained by photographing the calibration phantom (pre-photographing).

  In order to know the shooting direction of the sample W in actual shooting, the position information of the table 2 at the time of actual shooting must be used. However, the position variable indicating the position of the table 2 cannot be acquired unless a calibration phantom whose shape is known in advance is photographed. Therefore, the X-ray CT apparatus of the present invention is configured to use the position variable acquired by the pre-imaging for reconstructing the tomographic image instead of the position information of the table 2 at the time of actual imaging.

  The problem here is the reproducibility of the rotational movement of the table 2. Although the movement of the table 2 in actual shooting is considered to be almost the same as that in pre-shooting, it is slightly shifted in practice. The compensation for this deviation is the most characteristic part of the present invention, and will be described later.

<Calculation of position variable>
A method for calculating the position variable will be described. In order to calculate the position variable, a phantom having two spheres as shown in FIG. 6 is used. The size of the sphere and the distance between the spheres are known. Pre-photographing is performed with the phantom of FIG. Then, the image generation unit 8 generates 100 perspective images obtained by photographing the two spheres from various directions. This fluoroscopic image is called a pre-X-ray image P.

  The generated pre-X-ray image P is sent to the position variable acquisition unit 21. The position variable acquisition unit 21 recognizes the position and inclination angle of the table 2 three-dimensionally based on the perspective images of the two spheres reflected in each of the pre-X-ray images P. The position variable acquisition unit 21 calculates the position information of these tables 2 as a position variable. This acquisition of position information is performed for each pre-X-ray image P.

  If the movement pattern of the table 2 is completely the same between the pre-photographing and the actual photographing, a high-resolution tomographic image is obtained from the position information obtained by the pre-photographing and the 100 actual photographing X-ray images Q. it can. However, actually, the trajectory of movement of the table 2 is slightly different between pre-photographing and actual photographing. In the present invention, a marker m and an optical camera 7 for photographing the marker m are provided for the purpose of compensating for the deviation.

<Photographing of marker image in pre-photographing>
In the pre-photographing, the optical camera 7 photographs the back surface of the table 2 every time the pre-X-ray image P is photographed. Then, only 100 pre-marker images M as described with reference to FIG.

  FIG. 7 shows a data table acquired by pre-photographing stored in the storage unit 9 after pre-photographing is completed. The pre X-ray image P is imaged 100 times, and the position variables (α, β, γ...) Acquired based on each pre X-ray image P are stored in the storage unit 9. The storage unit 9 stores the premarker image M captured by the optical camera 7 in association with the position variables (α, β, γ...). In FIG. 7, the position variables acquired in the n-th pre-X-ray image P are represented by αn, βn, γn..., And the pre-marker image obtained when the pre-X-ray image P is photographed is represented by Mn. .

  The pre-marker image M is an index indicating the positional deviation of the table 2 that occurs between pre-photographing and actual photographing. That is, if the marker image is captured in the same manner as the pre-shooting in the actual shooting, and the pre-marker image M and the actual shooting marker image N in the actual shooting are compared, the position of the table 2 between the pre-shooting and the actual shooting You can know the degree of deviation.

<Capturing marker images in actual shooting>
Even in actual imaging performed with the sample W placed on the table 2, the X-ray CT apparatus operates in the same manner as in pre-imaging. The only difference from the pre-photographing is that the object placed on the table 2 is changed from the phantom to the sample W.

  In actual imaging, the sample W is imaged in the same manner as in pre-imaging with the sample W placed on the table 2 instead of the calibration phantom, and 100 actual X-ray images Q are acquired. At this time, the optical camera 7 captures the back surface of the table 2 every time the actual captured X-ray image Q is captured. Then, only 100 actual imaging marker images N as described in FIG. 5 are acquired, which is the same as the number of actual imaging X-ray images Q. That is, the X-ray CT apparatus has a positional relationship between the table 2 and the detector 3 with respect to the X-ray generator 1 in the n-th imaging in a series of pre-imaging, and the X-ray in the n-th imaging in a series of actual imaging. It operates so as to coincide with the positional relationship between the table 2 and the detector 3 with respect to the generator 1. However, due to the problem of mechanical accuracy, the positional relationship slightly shifts between pre-photographing and actual photographing.

  FIG. 8 shows a data table obtained by actual photographing stored in the storage unit 9 after the actual photographing is completed. The actual X-ray image Q is captured 100 times, and each of the actual X-ray images Q is stored in the storage unit 9. The storage unit 9 stores the actual captured marker image N captured by the optical camera 7 in association with the actual captured X-ray image Q. In FIG. 8, the n-th actual captured X-ray image is represented by Qn, and the actual captured marker image obtained when the actual captured X-ray image Qn is captured is represented by Nn.

  FIG. 9 displays the pre-marker image Mn acquired n times in the pre-photographing and the actual photo-marker image Nn acquired n-th in the real shooting in an overlapping manner. The markers reflected in the premarker image Mn are indicated by broken lines in FIG. Similarly, the marker reflected in the actual photographing marker image Nn is indicated by a solid line in FIG. In FIG. 9, the fact that the solid line marker and the broken line marker do not completely overlap means that the position of the table 2 in the n-th shooting of the pre-shooting and the position of the table 2 in the n-th shooting of the real shooting are different from each other. Will be. However, since the table 2 is operated so as to perform the same movement between the pre-photographing and the actual photographing, the marker misalignment on the marker image is caused by the marker on the pre-marker image Mn being on the actual photographing marker image Nn. It is so small that it can be discriminated which marker corresponds to.

  A method for compensating the positional deviation of the table 2 using the marker images M and N will be described. The pre-marker image M and the actual shooting marker image N generated by the optical image generation unit 12 are sent to the deviation amount acquisition unit 24. The deviation amount acquisition unit 24 acquires the deviation amount based on the marker images M and N. The amount of deviation indicates the amount of positional deviation of the table 2 that occurs between pre-photographing and actual photographing.

  The deviation amount acquisition unit 24 acquires the correlation between the pre-marker image M and the actual shooting marker image N. Then, a vector (deviation amount) representing the deviation of the marker position in the marker images M and N can be acquired. The solid-line arrows in FIG. 10 represent a state in which the amount of marker deviation reflected in the marker images M and N is acquired by collating the marker images M and N of the amount-of-shift acquisition unit 24. In FIG. 10, the shift amount acquisition unit 24 acquires the shift amount (x3, y3) related to the third shooting from the marker images Mn and Nn related to the third shooting. As described above, the deviation amount acquisition unit 24 is a marker photographed when the table 2 is in the same position with respect to the X-ray generator 1 by the same movement of the table 2 between the pre-imaging and the actual imaging. The amount of deviation is acquired by comparing the images M and N. The amount of deviation is acquired for every 100 actual captured marker images N.

  The deviation amount acquired by the deviation amount acquisition unit 24 is sent to the position variable correction unit 22. The position variable correction unit 22 corrects the position variable obtained by pre-imaging based on the amount of deviation, and acquires the position of the table 2 with respect to the X-ray generator 1 in actual imaging. An arrow indicated by a broken line in FIG. 10 represents a state in which the position variable is corrected by collating the position variable and the shift amount of the position variable correction unit 22. In FIG. 10, the position variable correction unit 22 corrects the third shooting from the position variable (α3, β3, γ3) related to the third shooting and the shift amount (x3, y3) related to the third shooting. Position variables (a3, b3, c3) are acquired. As described above, the position variable correction unit 22 uses the position variable (αn, βn, γn) related to the n-th shooting and the shift amount (xn, yn) related to the n-th shooting to the correction position related to the n-th shooting. Variables (an, bn, cn) are acquired. This correction is performed for every 100 position variables.

  The correction position variable acquired in this way accurately indicates the position of the table 2 in actual photographing. This is because the correction position variable is obtained by correcting the position variable obtained in the pre-photographing with the positional deviation amount of the table 2 that occurs between the pre-photographing and the actual photographing.

<Operation of X-ray CT system>
Next, the operation of the X-ray CT apparatus will be described with reference to FIG. In this operation, calibration using a phantom is performed every time a tomographic image of the sample W is taken.

  As an operation of the X-ray CT apparatus, as shown in FIG. 11, first, a phantom is placed on the table 2 (phantom placement step S1), and an operator operates the console 17 to start pre-imaging ( Pre-photographing step S2). And the position variable which shows the position of the table 2 is acquired from the X-ray image obtained by pre imaging (position variable acquisition step S3), and the sample W is mounted on the table 2 (sample mounting step S4). Subsequently, the operator operates the console 17 to start actual photographing (actual photographing step S5), and correction of the position variable is performed based on the deviation amount acquired from the marker images M and N (position variable correction). Step S6). Finally, a tomographic image of the sample W is acquired based on the X-ray image obtained by actual imaging and the correction position variable (reconstruction step S7). Hereinafter, these steps will be described in order.

<Phantom placement step S1, pre-shooting step S2>
First, the phantom described with reference to FIG. 6 is placed at the placement position on the front surface of the table 2. When the operator operates the console 17 to give an instruction to start pre-imaging to the X-ray CT apparatus, the rotational movement of the table 2 and the detector 3 is started and the X-ray control unit 11 controls the X-ray. X-rays are intermittently emitted from the generator 1. Thus, pre-photographing for photographing the phantom is performed.

  X-rays irradiated from the X-ray generator 1 pass through the phantom and are detected by the detector 3. Based on the detection signal output from the detector 3, the image generation unit 8 generates 100 series of pre-X-ray images P in which the phantom is captured while changing the imaging direction.

  Each time the pre-X-ray image P is photographed, the optical camera 7 photographs the back surface of the table 2 with visible light. The optical image generation unit 12 generates a series of 100 pre-marker images M in which the marker m on the back surface of the table 2 is copied based on the detection signal output from the optical camera 7.

<Position variable acquisition step S3>
The pre-X-ray image P is sent to the position variable acquisition unit 21. The position variable acquisition unit 21 acquires, for each pre-X-ray image P, a position variable (α, β, γ...) Indicating the position of the table 2 with respect to the X-ray generator 1 based on the series of pre-X-ray images P. . The position variables (α, β, γ...) And the premarker image M are stored in the storage unit 9 in association with the number of shootings in the pre-shooting.

<Sample placement step S4, actual photographing step S5>
After the pre-photographing is completed, the operator removes the phantom from the table 2 and places the sample W at the same position as the placement position on the table 2 where the phantom is placed. This sample W is an actual imaging target for which a tomographic image needs to be acquired. When the operator can operate the console 17 to give an instruction to start actual imaging to the X-ray CT apparatus, the rotational movement of the table 2 and the detector 3 is started, and the X-ray control unit 11 controls X. X-rays are intermittently emitted from the line generator 1. In this way, actual photographing for photographing the sample W is performed. At this time, the table 2 and the detector 3 are moved in the same manner as the pre-photographing.

  X-rays irradiated from the X-ray generator 1 pass through the sample W and are detected by the detector 3. Based on the detection signal output from the detector 3, the image generation unit 8 generates 100 series of actual captured X-ray images Q in which the sample W is captured while changing the imaging direction. The optical camera 7 captures the back surface of the table 2 with visible light every time an actual captured X-ray image Q is captured. Based on the detection signal output from the optical camera 7, the optical image generation unit 12 generates a series of 100 actual captured marker images N in which the marker m on the back surface of the table 2 is copied. The actual captured X-ray image Q and the actual captured marker image N are stored in the storage unit 9 in association with the number of times of actual capturing.

<Position variable correction step S6>
After the actual photographing is completed, the deviation amount acquiring unit 24 collates the pre-marker image M and the actual photographing marker image N stored in the storage unit 9 for each number of photographing, and the positional deviation of the table 2 in the pre-photographing and the actual photographing. A shift amount (x, y) indicating is acquired. The shift amount (x, y) is stored in the storage unit 9 in association with the number of shootings in pre-shooting and actual shooting.

  The position variable correction unit 22 reads out the shift amount (x, y) and the position variable (α, β, γ...) Stored in the storage unit 9, and based on the shift amount (x, y), the position variable. (Α, β, γ...) Is corrected for each imaging number, and a corrected position variable (a, b, c...) Indicating the position of the table 2 with respect to the X-ray generator 1 in actual imaging is acquired.

<Reconfiguration step S7>
The correction position variables (a, b, c...) Are sent to the reconstruction unit 10. The reconstruction unit 10 recognizes the photographing direction of the sample W in actual photographing for each number of times of photographing based on the correction position variables (a, b, c...). Then, the reconstruction unit 10 reads out a series of actual X-ray images Q stored in the storage unit 9 and outputs a series of actual X-ray images Q and correction position variables (a, b, c...). To reconstruct a tomographic image. That is, the reconstruction unit 10 recognizes the positional deviation of the table 2 generated between the pre-photographing and the real photographing by using the premarker image M and the real photographing marker image N, and captures a series of pre-X-ray images P. A tomographic image is reconstructed based on a series of actual X-ray images Q by recognizing the manner of movement of the table 2 at the time. The generated tomographic image is displayed on the display unit 18, and the operation of the X-ray CT apparatus is completed.

  As described above, according to the present invention, the imaging direction is changed by moving the table 2 and the detector 3 relative to the X-ray generator 1 with the calibration phantom placed at the mounting position of the table 2. Then, after performing pre-photographing of the phantom one after another, moving the table 2 and the detector 3 in the same manner as the pre-photographing, performing actual photographing of photographing the sample W one after another while changing the photographing direction. The tomographic image is reconstructed based on the pre-X-ray image P and a series of actual X-ray images Q. Prior to actual imaging, the reconstruction unit 10 recognizes the manner of movement of the table 2 and the detector 3 during imaging using the pre-X-ray image P. If the tomographic image is reconstructed based on the series of actual X-ray images Q, it is possible to consider the manner of movement of the table 2 and the detector 3 when the actual X-ray images Q are acquired. A high-resolution tomographic image can be acquired.

  However, this method has drawbacks. That is, the table 2 does not always move in the same way for pre-photographing and actual photographing. Therefore, according to the present invention, the marker m is provided on the back surface of the table 2. The marker m is photographed by an optical camera between pre-photographing and actual photographing. The reconstruction unit 10 generates a table 2 generated between the pre-photographing and the real photographing by the real photographing marker image N obtained by the real photographing when the tomographic image is reconstructed and the premarker image M obtained by the pre-photographing. Recognize the position shift. Then, the reconstruction unit 10 generates a tomographic image of the sample W in consideration of this positional deviation. With this configuration, the reconstruction unit 10 can accurately know the position of the table 2 in actual photographing even if the movement mode of the table 2 differs between pre-photographing and actual photographing. As a result, an X-ray CT apparatus capable of acquiring a high-resolution tomographic image can be provided.

  The above-described configuration acquires position variables (α, β, γ...) Indicating the movement of the table 2 by pre-photographing, collates the actual photographing marker image N with the premarker image M, and determines the position variables (α, β, γ... are corrected to obtain corrected position variables (a, b, c...), and the reconstruction unit 10 operates based on the corrected position variables (a, b, c...). Then, even if the manner of movement of the table 2 differs between pre-photographing and actual photographing, the reconstruction unit 10 can generate a tomographic image taking into account the position of the table 2 in actual photographing.

  As described above, if the markers m are arranged in a two-dimensional matrix on the back surface of the table 2, the optical camera can reliably photograph the marker m no matter how the table 2 moves. .

  Next, the configuration of the X-ray CT apparatus according to the second embodiment will be described. The X-ray CT apparatus according to the second embodiment is substantially the same as the configuration of the X-ray CT apparatus described in the first embodiment. A different point is that the front surface of the table 2 is provided with a sample mounting plate 2p for sample mounting. In the second embodiment, the phantom and the sample W are placed on the sample mounting plate 2p and are not placed on the front surface of the table 2. The sample mounting plate 2p is rectangular following the rectangular table 2, and is made of, for example, an aluminum sheet.

  FIG. 12 is a functional block diagram of the X-ray CT apparatus according to the second embodiment. 12, the detector moving mechanism 5, the XY moving mechanism 6, the image generating unit 8, the storage unit 9, the reconstruction unit 10, the X-ray control unit 11, the optical image generating unit 12, and the detector moving described in FIG. The control unit 16a, the XY movement control unit 16b, the console 17, the display unit 18, the position variable acquisition unit 21, the position variable correction unit 22, and the deviation amount acquisition unit 24 are omitted.

  A unique configuration in the second embodiment will be described. The sample mounting plate moving mechanism 6p is provided for the purpose of moving the sample mounting plate 2p with respect to the table 2, and the sample mounting plate movement control unit 16c is used for controlling the sample mounting plate moving mechanism 6p. Is provided. The sample placement plate movement control unit 16 c is controlled in an integrated manner by the main control unit 27.

  FIG. 13 shows a specific configuration of the sample mounting plate moving mechanism 6p. The sample mounting plate moving mechanism 6 p has a base 6 p 1 provided at one vertex of the table 2. The base 6 p 1 has an L shape that follows the side of the table 2. Each of the arms constituting the base portion 6p1 includes a motor 6p3 and a push screw 6p4 for moving the sample mounting plate 2p in the X direction, and a motor 6p5 and a push screw 6p6 for moving the sample mounting plate 2p in the Y direction. ing. The push screw 6p4 extends in the X direction, and the push screw 6p6 extends in the Y direction.

  The sample mounting plate moving mechanism 6p includes a spring 6p7 at a position where one vertex closest to the base 6p1 in the sample mounting plate 2p and one vertex on the sample mounting plate 2p side at the joint of the arm of the base 6p1 are bridged. have. This spring is provided for the purpose of moving the sample mounting plate 2p relative to the base 6p1 by applying a tensile force to the sample mounting plate 2p.

<Improvements from the configuration of the first embodiment>
In the configuration of the first embodiment, first, a phantom is placed on the table 2 and pre-photographing is performed. When actual photographing is performed, the sample W is placed at the same position as the placement position on the table 2 where the phantom was placed. Thus, in the configuration of the first embodiment, there is a restriction that the position where the phantom is placed and the position where the sample W is placed must be matched.

  The reason why this restriction occurs will be described. FIG. 14 shows different positions p and q in the table 2. When the pre-photographing is performed with the phantom placed at the position p in FIG. 14, the sample W must be placed at the position p and the actual photographing must be performed. If pre-photographing is performed at the position p and the sample W is placed at the position q and actual photographing is performed, the acquired tomographic image is blurred.

  FIG. 15 shows how the position of the table 2 is shifted between when the phantom is photographed at the position p and when the phantom is photographed at the position q. . The horizontal axis of the graph means the rotation angle of the table 2, and the vertical axis of the graph means the positional deviation of the table 2 with reference to the circular motion. If the table 2 has made a perfect circular motion, the positional deviation is always zero. However, in reality, the movement of the table 2 slightly deviates from the circular movement as shown in FIG. 15 due to the problem of mechanical accuracy.

  The solid line graph in the upper diagram of FIG. 15 is a positional deviation based on the circular motion reference in the table 2 when pre-photographing is performed with the position of p as the mounting position. A broken line graph in the upper diagram of FIG. 15 is a positional deviation based on the circular motion reference in the table 2 when actual photographing is performed with the position of p as the mounting position. As can be seen from the comparison between the solid line and the broken line, the motion of the table 2 in the pre-photographing and the real photographing is approximately approximate even if it does not completely match.

  On the other hand, the solid line graph in the lower diagram of FIG. 15 is a positional shift of the table 2 when pre-photographing is performed with the position of q as the mounting position. Here, the solid line graph in the upper diagram of FIG. 15 and the solid line graph in the lower diagram of FIG. 15 do not approximate each other. That is, the table 2 has a different rotational movement mode depending on which part is used as the mounting position of the sample W.

  This is caused by the structure of the XY moving mechanism 6 that drives the table 2. The XY moving mechanism 6 has an arm extending in the X direction and an arm extending in the Y direction. The movement of the table 2 is realized by this arm sliding. The reason why the movement of the table 2 does not become ideal even when trying to move the table 2 in a circular motion is that the surface of the arm that drives the table 2 is not flat as ideal.

  Here, it is assumed that the table 2 is rotated twice with the position p of the table 2 as the placement position. That is, this is a case where the phantom and the sample W are placed at the same position on the table 2. At this time, the XY moving mechanism 6 rotates the table 2 using the same part of the arm in the first rotation and the second rotation. Then, the reproducibility of the movement of the table 2 is increased. This is because the undulation of the arm that disturbs the circular motion of the table 2 is the same in the first and second rotations.

  However, the situation is different when the table 2 is rotated once with the position p of the table 2 as the placement position and the table 2 is rotated once with the position q as the placement position (see FIG. 14). That is, this is a case where the phantom and the sample W are placed at different positions on the table 2. In this case, the XY moving mechanism 6 rotates the table 2 using different portions of the arm for the first rotation and the second rotation.

  The arms of the XY moving mechanism 6 have different surface undulations depending on their positions. Therefore, when the table 2 is rotated by using different portions of the arm for the first rotation and the second rotation, the undulation of the arm that disturbs the circular motion of the table 2 is different every time the table 2 is rotated. Therefore, the reproducibility of the motion when the table 2 is rotated twice is low.

  By the way, according to the configuration of the first embodiment, by acquiring the marker images M and N, it is possible to compensate for a slight change in the movement mode when the table 2 is rotated twice. However, if the movement pattern of the table 2 is too different between the first rotation and the second rotation, the position variable cannot be corrected using the marker images M and N. That is, if the position of the image of the marker m is too different between the pre-marker image M and the actual shooting marker image N, it becomes impossible to determine how the marker m has moved. This is because the marker m is arranged in a two-dimensional matrix on the back surface of the table 2 and it is not known which marker on the actual captured marker image N corresponds to the marker reflected in the premarker image M.

  That is, according to the configuration of the first embodiment, in order to acquire a tomographic image, it is necessary to perform pre-imaging at a position where the object from which the tomographic image has been acquired is placed. When acquiring a tomographic image of a part of the large sample W, it is complicated to perform pre-imaging every time the part of the sample W where the tomographic image is to be acquired changes.

  In order to solve such problems, in the configuration of the second embodiment, the position where tomography is performed in the table 2 is limited. Specifically, as shown in FIG. 16, when the line segments that divide the table 2 into 5 parts vertically and horizontally are arranged in a grid pattern, 16 intersection points at which the line segments intersect with each other are set as the mounting positions of the sample W. To do. In the configuration of the second embodiment, 16 kinds of pre-photographing are performed by placing a phantom on these 16 intersections. Then, when performing actual imaging, the imaging part of the sample W that needs to acquire a tomographic image is moved to one of the 16 intersections on the table 2. By doing so, the rotational movement of the table 2 is reliably approximated between pre-photographing and actual photographing.

  The XY movement mechanism 6 according to the second embodiment sends the movement of the table 2 to the deviation amount acquisition unit 24 and the position variable correction unit 22. As a result, the deviation amount acquisition unit 24 and the position variable correction unit 22 can recognize whether shooting has been performed by selecting any of the 16 intersections in the table 2 during operation. At the time of actual shooting, the deviation amount acquisition unit 24 and the position variable correction unit 22 obtain data acquired at the same position as the position of the intersection selected in the actual shooting from the data obtained by 16 kinds of pre-shooting. Select to work.

  In the X-ray CT apparatus according to the second embodiment, a substrate is assumed as the sample W. When it is desired to generate a tomographic image in which a part of the substrate is enlarged, the imaging portion on the substrate must be moved to the position of the intersection in the table 2. This movement is executed by the sample mounting plate moving mechanism 6p. The movement of the sample W by the sample mounting plate moving mechanism 6p is performed prior to taking a tomographic image of the sample W.

  With this configuration, unlike the first embodiment, it is not necessary to perform pre-imaging every time tomographic imaging. Therefore, in the configuration of the second embodiment, if 16 kinds of pre-photographing are performed, a high-resolution tomographic image can be obtained even if actual photographing is continuously performed for a while.

  As described above, the configuration of the second embodiment shows a specific configuration of the X-ray CT apparatus of the present invention. The manner of movement of the table 2 differs depending on which part of the table 2 the tomographic image is taken. Therefore, according to the above-described configuration, there is a configuration in which the imaging portion of the sample W is moved to the position on the table 2 where the calibration phantom is placed. By configuring in this way, an X-ray CT apparatus capable of acquiring a high-resolution tomographic image can be provided.

  The present invention is not limited to the above-described configuration and can be modified as follows.

  (1) You may comprise the structure of the table 2 of the above-mentioned Example 1 as shown in FIG. According to this modification, as shown in FIG. 17, the table 2 has a frame-shaped peripheral member 2a and a central plate 2b accommodated inside the peripheral member 2a. The center plate 2b is configured to be fitted into the inner hole of the peripheral member 2a, and can be attached to and detached from the peripheral member 2a. The center plate 2b is made of carbon that does not easily expand and contract due to changes in temperature. In this modification, the sample W is placed on the center plate 2b.

  When the central plate 2b is removed from the peripheral member 2a, the X-ray generator 1 and the optical camera 7 provided on the lower side of the table 2 are exposed. When maintenance of the X-ray generator 1 and the optical camera 7 is performed, it is convenient if the center plate 2b is detached from the peripheral member 2a. Further, the peripheral member 2a is fixed to the XY moving mechanism 6, and the positional relationship between the peripheral member 2a and the XY moving mechanism 6 does not deviate.

  FIG. 18 shows the back surface of the table 2. The center plate 2b is marked with the marker m described in FIG. 2, but is omitted in FIG. The peripheral member 2a and the center plate 2b are marked with marks indicating their positional relationship. In FIG. 14, A, B, and C are marked at the three corners of the rectangular peripheral member 2a, and A, B, and C are marked at the three corners of the rectangular central plate 2b. Has been. And each mark attached | subjected to the peripheral member 2a and the center board 2b is arrange | positioned in the position where the same mark mutually faces. Therefore, if the positional relationship between the A marks attached to the peripheral member 2a and the central plate 2b is known, the change in the positional relationship between the peripheral member 2a and the central plate 2b at the corner where the A mark is provided can be known. it can. The marks B and C are indicators for knowing the change in the positional relationship between the peripheral member 2a and the central plate 2b, like the mark A.

  The optical camera 7 acquires a mark image by photographing the mark at a time before the central plate 2b is removed from the peripheral member 2a and at a time after the central plate 2b is removed from the peripheral member 2a and accommodated again. . This mark image includes two marks A, B and C. The printed image is generated by the optical image generation unit 12 using the detection signal transmitted from the optical camera 7.

  The reconstruction unit 10 reconstructs a tomographic image by recognizing the positional change between the peripheral member 2a and the central plate 2b before and after the attachment and detachment of the central plate 2b based on this mark image. Specifically, the position variable correcting unit 22 corrects not only the amount of deviation obtained from the marker images M and N but also the peripheral member obtained from the mark image when correcting the position variables (α, β, γ...). Correction is performed in consideration of the positional deviation of the central plate 2b with respect to 2a.

  By correcting in this way, even if the central plate 2b is attached or detached after pre-photographing and before actual photographing, the tomographic image is not blurred due to the positional deviation between the peripheral member 2a and the central plate 2b.

  In the X-ray CT apparatus, the table 2 may be removed from the apparatus for maintenance purposes. If the table 2 is detached from the apparatus after the pre-shooting and before the actual shooting, the position of the table 2 in the actual shooting cannot be accurately calculated even if the actual shooting marker image N and the pre-marker image M are collated. Therefore, in the above-described configuration, it is possible to know how much the position of the table 2 is shifted before and after the table 2 is attached and detached. That is, the table 2 is composed of a removable central plate 2b and a non-detachable peripheral member 2a, and it is possible to know how much the central plate 2b has moved from the peripheral member 2a before and after the central plate 2b is attached and detached. I am doing so. By doing so, the position of the table 2 in the actual photographing can be accurately calculated even if the central plate 2b is attached and detached after the pre photographing and before the actual photographing.

  (2) In each of the above-described embodiments, the X-ray generator 1 and the optical camera 7 are provided on the lower side of the table 2 and the detector 3 is provided on the upper side of the table 2. Is not limited to such a configuration. That is, as shown in FIG. 19, the detector 3 and the optical camera 7 may be provided below the table 2, and the X-ray generator 1 may be provided above the table 2. Even in such a configuration, the surface of the table 2 on which the sample is placed is the front surface, and the marker m is provided on the back surface opposite to the front surface.

m Marker M Pre-marker image N Actual imaging marker image 1 X-ray generator (radiation source)
2 Table 2a Peripheral member 2b Center plate 2p Sample mounting plate 3 Detector (radiation detector)
5 Detector moving mechanism (detector moving means)
6 XY movement mechanism (table movement means)
7 Optical camera 8 Image generation unit (image generation means)
12 Optical image generation unit (optical image generation means)
16a Detector movement control unit (detector movement control means)
16b XY movement control unit (table movement control means)
16c Sample placement plate movement control unit (sample placement plate movement control means)
22 Position variable correction unit (position variable correction means)
24 Deviation amount acquisition unit (deviation amount acquisition means)

Claims (5)

A table for placing a sample comprising a back surface and a front surface having a marker;
A radiation source for irradiating the table with radiation from one side;
Table moving means for moving the table relative to the radiation source;
Table movement control means for controlling the table movement means;
A radiation detector provided on the other surface side of the table for detecting radiation transmitted through the table;
Detector moving means for moving the radiation detector relative to the radiation source;
Detector movement control means for controlling the detector movement means;
An optical camera that captures a marker on the back surface of the table with visible light and outputs a detection signal each time a radiographic image is captured;
Based on the detection signal output from the radiation detector, the imaging direction is changed by moving the table and the radiation detector with respect to the radiation source in a state where a calibration subject is placed at the mounting position of the table. A series of pre-radiation images are generated in the pre-imaging in which the subject is photographed one after another while changing, and the table and the radiation detector are placed in the same manner as the pre-imaging in a state where the sample is placed at the mounting position of the table. An image generating means for generating a series of actual radiographic images in actual imaging in which the sample is imaged one after another while changing the imaging direction by moving;
Optical image generating means for generating a series of pre-marker images in which markers are reflected in pre-photographing and generating a series of real-photographing marker images in which markers are captured in actual photographing based on the detection signal output from the optical camera When,
Recognize the positional deviation of the table that occurred between pre-photographing and real-photographing with the actual photographing marker image and the pre-marker image, and recognize the movement pattern of the table during photographing with a series of pre-radiation images A radiation CT apparatus comprising: reconstruction means for reconstructing a tomographic image based on a series of actual radiographic images. The radiation CT apparatus according to claim 1,
Position variable acquisition means for acquiring, for each pre-radiation image, a position variable indicating the position of the table with respect to the radiation source based on a series of pre-radiation images;
A deviation amount acquisition means for collating the actual shooting marker image with the premarker image and acquiring a deviation amount indicating a positional deviation of the table in the pre-shooting and the actual shooting for each actual shooting marker image;
Position variable correction means for correcting the position variable based on the amount of deviation and acquiring a correction position variable indicating the position of the table with respect to the radiation source in actual imaging for each position variable;
A radiation CT apparatus, wherein the reconstruction means reconstructs a tomographic image using a series of actual radiographic images and the correction position variable. The radiation CT apparatus according to claim 1 or 2,
The radiation CT apparatus, wherein the marker is provided on the entire surface of the back surface of the table. The radiation CT apparatus according to any one of claims 1 to 3,
The table includes a frame-shaped peripheral member and a central plate that is housed inside the peripheral member and is detachable from the peripheral member.
The peripheral member and the central plate are marked with a mutual positional relationship,
A mark image is obtained by photographing the mark when the optical camera is before the central plate is removed from the peripheral member and after the central plate is removed from the peripheral member and accommodated again. ,
The radiation CT apparatus, wherein the reconstructing means reconstructs a tomographic image of the sample by recognizing a positional change between the peripheral member and the central plate before and after the central plate is attached / detached based on the mark image. . The radiation CT apparatus according to any one of claims 1 to 3,
A sample mounting plate for mounting the sample is provided on the front side of the table;
Sample mounting plate moving means for moving the sample mounting plate relative to the table;
Prior to taking a tomographic image of the sample, it is possible to move the imaging part of the sample to a position where the subject for calibration is placed on the table by controlling the sample mounting plate moving means. A radiation CT apparatus comprising a sample placement plate movement control means for performing

Images