JP3916385B2 - Computed tomography equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a computer tomography apparatus among non-destructive inspection apparatuses, and particularly to a computer tomography apparatus that requires no skill in operation and is easy for an operator to handle.
[0002]
[Prior art]
In recent years, high-resolution industrial computer tomography apparatuses (hereinafter referred to as CT scanners) have been manufactured for the purpose of inspecting small electronic components and the like with high resolution.
[0003]
FIG. 4 is a schematic diagram showing a system configuration example of this type of conventional high-resolution CT scanner.
[0004]
In FIG. 4, an X-ray tube 101 and a detector 103 that detects a cone-shaped X-ray beam 102 emitted from the X-ray tube 101 with two-dimensional spatial resolution are arranged to face each other. A transmission image of the subject 104 inside is obtained.
[0005]
When a cross-sectional image is taken, a large number of transmission images are obtained while the subject 104 on the rotary table 105 is rotated by the rotation / lifting mechanism 106 (referred to as scanning).
[0006]
The multiple transmitted images are processed by the data processing unit 109 to obtain one or a plurality of cross-sectional images of the subject 104.
[0007]
The rotary table 105 and the detector 103 are moved closer to or away from the X-ray tube 101 by the shift mechanism 107, the imaging distance FCD and the detection distance FDD can be changed, and the imaging magnification (= FDD / FCD) is changed according to the purpose. be able to.
[0008]
The imaging position of the subject 104 is changed by moving the subject 104 up and down in the direction of the rotation axis 118, but by performing a helical scan that simultaneously rotates and lifts the rotary table 105, a wide-area cross-sectional image (three-dimensional image). There is also a method of obtaining the image by one shooting.
[0009]
On the other hand, in such a conventional high-resolution CT scanner, it is necessary to redo calibration such as distortion calibration, slice plane calibration, and rotation center calibration each time the imaging distance FCD and the detection distance FDD are changed.
[0010]
First, the distortion calibration is a calibration of the distortion of the detector 103.
[0011]
The detector 103 includes an X-ray II 112 and a television camera 113.
[0012]
The distortion is mainly caused by the detection surface of the X-ray II being a curved surface, and varies depending on the detection distance FDD.
[0013]
Whenever the detection distance FDD changes, the operator attaches the grid plate 120, which is a calibration jig shown in FIG. 5A, to the front surface of the detector 103 to perform distortion calibration.
[0014]
The grid plate 120 is obtained by embedding a metal wire grid 122 in the acrylic plate 121, and obtains parameters used for distortion correction in this distortion calibration.
[0015]
The slice plane calibration is a calibration for setting the position of the imaging plane 119 on the transmission image.
[0016]
The imaging plane 119 is a plane defined as a plane that passes through the X-ray focal point F and is orthogonal to the rotation axis 118, and changes on the transmission image due to a mechanism error when the detection distance FDD or the imaging distance FCD is changed.
[0017]
The operator performs calibration every time the detection distance FDD and the photographing distance FCD change.
[0018]
In the calibration, first, the rotary table 105 is moved up and down and stopped at a position where the table surface becomes a straight line on the transmission image.
[0019]
Next, a wire plate 123, which is a calibration jig shown in FIG. 5B, is attached to the front surface of the detector 103, and the position is adjusted so that the image of the wire 125 matches the image of the table surface.
[0020]
Next, the table is removed from the field of view, and the image of the wire 125 is captured to set the position of the imaging surface 119.
[0021]
Further, the rotation center calibration is a calibration for setting the position of the rotation axis 118 on the transmission image.
[0022]
The rotating shaft 118 changes on the transmission image due to a mechanism error when the detection distance FDD or the photographing distance FCD is changed.
[0023]
The operator performs calibration every time the detection distance FDD and the photographing distance FCD change.
[0024]
In the calibration, first, a center calibration phantom 126 which is a calibration jig shown in FIG. 5C is placed on the rotary table 105, and an image of the wire 128 is captured over a rotation angle of 360 degrees. Set the position of.
[0025]
The entire mechanical part of the apparatus is housed in a shielding box 114.
[0026]
In addition, the shielding box 114 that prevents X-rays from leaking to the outside has an opening 115, and the specimen door 116 is opened and closed to replace the subject 104.
[0027]
FIG. 6 is a schematic diagram showing a detailed configuration example of the conventional shielding box 114.
[0028]
In FIG. 6, the sample door 116 is supported by a rail 131 and is opened and closed by sliding.
[0029]
The sample door 116 has a window of lead glass 130 so that the inside can be observed.
[0030]
A maintenance door 132 is separately provided on the side surface so that an inspector can go in and out for internal inspection and parts replacement.
[0031]
The problem with the shielding box 114 is that when an operator drops a sample or the like into the interior, the operator must turn to the side and enter from the maintenance door 132, and the maintenance door 132 is on the side, so that objects cannot be placed. It is a point where space is created and installation on a wall becomes impossible.
[0032]
FIG. 7 is a schematic diagram showing another detailed configuration example of the conventional shielding box 114.
[0033]
As shown in FIG. 7, the opening 115 and the sample door 116 are enlarged to serve as a maintenance door.
[0034]
The problem with the shielding box 114 is that the sample door 116 is X-ray shielded with a lead or the like attached thereto, so that it becomes heavy and the operability becomes very poor.
[0035]
In particular, sample exchange is a problem because it is frequently performed.
[0036]
[Problems to be solved by the invention]
Recently, there has been a strong demand for examinations using CT scanners, and the types of examination objects and examination contents have been expanded and are becoming widespread in various fields.
[0037]
Under such circumstances, there is an increasing demand for eliminating the difficulty of handling conventional high-resolution CT scanners.
[0038]
However, in the conventional high resolution CT scanner described above, the calibration operation is troublesome, and when the inspection conditions such as the detection distance FDD and the imaging distance FCD of the apparatus are changed, the type of calibration corresponding to the change is performed each time. It has to be chosen and implemented, which is very annoying.
[0039]
For this reason, skill is required for the operation of the operator, and the image quality often decreases due to an erroneous operation.
[0040]
In addition, the arrangement structure of the sample door and the maintenance door of the shielding box has become difficult to handle in apparatus installation, sample replacement, maintenance, and the like.
[0041]
An object of the present invention is to provide a computer tomography apparatus that does not require skill in operation and is easy for an operator to handle.
[0042]
[Means for Solving the Problems]
In order to achieve the above object, a computed tomography apparatus according to a first aspect of the present invention includes a radiation source that emits a radiation beam, a radiation detector that detects the radiation beam from the radiation source with spatial resolution, and radiation. Rotating means for relatively rotating the subject within the beam, and reconstructing means for creating a cross-sectional image of the subject from transmission data from multiple directions of the subject obtained by the radiation detector during relative rotation by the rotating means, , A display means, and a necessary calibration judgment means for judging and selecting the type of calibration required from the change in the state of the apparatus main body and displaying the selected calibration type on the display means .
[0043]
Therefore, in the computed tomography apparatus of the invention corresponding to claim 1, the type of calibration required is automatically determined when the state of the apparatus changes due to changes in geometric conditions, temperature fluctuations, changes in radiation conditions, or the like. This eliminates the need for the operator to worry about when and what calibration is required.
[0044]
The computer tomography apparatus of the invention corresponding to claim 2, in a computer tomography apparatus of the present invention corresponding to the claim 1, as a calibration of the type determined by the required calibration determining means, on said display means Based on the calibration type selected and displayed, automatic calibration means for automatically performing at least one of air calibration, distortion calibration, slice plane calibration, rotation center calibration, and FCD calibration is added.
[0045]
Therefore, in the computed tomography apparatus according to the second aspect of the present invention, calibration is automatically performed, so that operability can be improved.
[0046]
Furthermore, a computer tomography apparatus according to a third aspect of the present invention is the computer tomography apparatus according to the first or second aspect of the present invention, in which at least a radiation source, a radiation detector, and a subject are accommodated. A radiation shielding box having an opening for exchanging the specimen and a radiation shielding door that is divided into two parts covering the opening of the radiation shielding box and can be opened and closed respectively are added.
[0047]
Therefore, in the computed tomography apparatus of the invention corresponding to claim 3, since one door can be used for exchanging the sample and two doors can be used for maintenance, the computer has good operability and is easy for the operator to handle. A tomographic apparatus can be obtained.
[0050]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0051]
1A and 1B are a plan view and a front view showing a system configuration example of a CT scanner according to the present embodiment.
[0052]
In FIG. 1, as an X-ray tube 1 as a radiation source, a microfocus X-ray tube having a focal point F of a radiating X-ray beam 2 of several to several tens of μm is used, and an X-ray II (image) is used as a radiation detector 3. Intensifier tube) and a TV camera.
[0053]
The X-ray tube 1 and the radiation detector 3 are arranged to face each other and are supported by a shift mechanism 8.
[0054]
The subject 4 is placed on the rotary table 5, and is rotated along the imaging surface 14 in the X-ray beam 2 by the rotation / elevating mechanism 6 and is moved up and down at right angles to the imaging surface 14.
[0055]
The subject 4 is moved in the COF direction across the X-ray beam 2 by the rotation center offset mechanism 7 together with the rotary table 5, and between the X-ray tube 1 and the radiation detector 3 by the shift mechanism 8. Is moved to change the shooting distance FCD.
[0056]
The radiation detector 3 detects the X-ray beam 2 with two-dimensional spatial resolution, and the shift mechanism 8 moves between the X-ray tube 1 and the radiation detector 3 to change the detection distance FDD. Is done.
[0057]
The grid plate 11 has the same structure as the conventional one, and is put in and out of the front surface of the radiation detector 3 by the grid driving unit 12.
[0058]
The rotary table 5 is provided with a narrow gap 15 with little X-ray absorption perpendicular to the rotary shaft 13 and is used for slice plane calibration.
[0059]
On the other hand, as other components, a data processing unit 19 that processes a transmission image from the radiation detector 3, a display unit 20 that displays processing results and the like, and a mechanism unit are controlled by commands from the data processing unit 19. The mechanism control unit 18, the X-ray control unit 17 that controls the tube voltage and tube current of the X-ray tube 1, and the high voltage generator 16, and the portion including the X-ray tube 1, the subject 4, and the radiation detector 3 are housed. X-ray shielding box 25 and the like are provided.
[0060]
The data processing unit 19 and the display unit 20 are ordinary computers, and include a CPU, a memory, a disk, a keyboard, an interface, and the like, and store software and the like for reconstructing a cross-sectional image from tomographic sequences and data.
[0061]
The operator uses the data processing unit 19 and the display unit 20 to perform menu selection, condition setting, manual operation of the mechanism unit, start of tomography, apparatus status reading, cross-sectional image display, cross-sectional image analysis, and the like.
[0062]
The data processing unit 19 includes a tomographic scan control unit 21, a necessary calibration determination unit 22, an automatic calibration unit 23, and a reconstruction unit 24.
[0063]
The scan control unit 21 performs tomographic scan control.
[0064]
The necessary calibration determination unit 22 determines and selects the type of calibration required from the change in the state of the apparatus main body.
[0065]
The automatic calibration unit 23 includes, for example, air calibration (gain calibration), distortion calibration, slice plane calibration, rotation center calibration, and FCD calibration (shooting distance calibration) as the type of calibration selected and selected by the necessary calibration determination unit 20. Automatically perform at least one calibration.
[0066]
The reconstruction unit 24 uses the tomographic scan control by the scan control unit 21 to obtain the object from multi-directional transmission data of the subject 4 obtained by the radiation detector 3 during the rotation of the subject 4 by the rotary table 5. A cross-sectional image of the specimen 4 is created (reconstructed).
[0067]
2A and 2B are a plan view and a front view showing a configuration example of the shielding box in the CT scanner of the present embodiment.
[0068]
In FIG. 2, the shielding box 25 is made by sticking a lead plate to an iron plate and has an opening 30.
[0069]
The opening 30 is covered with a sample door 31 at the top and a maintenance door 32 at the bottom.
[0070]
The sample door 31 and the maintenance door 32 are each made of an iron plate and a lead plate, but the sample door 31 is provided with a window of lead glass 34 for internal observation.
[0071]
The sample door 31 is supported by a rail 33 attached to the shielding box 25 and is opened and closed in a sliding door manner. The maintenance door 32 is attached to the shielding box 25 by a hinge 35 and is opened and closed in a door manner.
[0072]
Here, the two doors 31 and 32 overlap each other when they are closed so that X-rays do not leak.
[0073]
Each of the two doors 31 and 32 is provided with an X-ray interlock so that X-ray radiation can be performed when both doors are closed.
[0074]
Further, when the two doors 31 and 32 are opened, the opening 30 is opened without any obstacle so that internal maintenance can be performed.
[0075]
Next, the operation of the CT scanner configured as described above according to the present embodiment will be described.
[0076]
In FIG. 1, when only a transmission image is obtained, the operator places the subject 4 on the rotary table 5, turns on X-rays, and displays the transmission image on the display unit 20.
[0077]
In the case of a cross-sectional image, the subject 4 is moved up and down by the rotation / lifting mechanism 6 so that the center of the examination position is aligned with the imaging surface 14.
[0078]
This can also be done while looking at the transmission image.
[0079]
When the scan is started by setting the tube voltage, the tube current, and the integration time, the rotary table 5 rotates, and during this time, a transmission image is collected by the data processing unit 19, and from a large number of transmission data obtained in the 360 ° direction, One or a plurality of cross-sectional images parallel to the imaging surface 14 are reconstructed and displayed on the display unit 20.
[0080]
Here, the integration time is the collection time of one transmission image.
[0081]
The above operation is performed by the scan control unit 21 and the reconstruction unit 24.
[0082]
The operator adjusts the detection distance FDD and the imaging distance FCD according to the overall size of the subject 4 and the position and size of the examination part.
[0083]
Further, when the detection distance FDD and the photographing distance FCD are changed, the rotation center offset is changed so that the rotation center is not greatly deviated from the visual field center.
[0084]
This rotation center offset is also moved when performing an offset scan (a scan in which the rotation center is set at the end of the field of view and the imaging area is enlarged).
[0085]
The necessary calibration determination unit 22 determines and selects the type of calibration required from the state change of the apparatus before scanning, and displays it on the display unit 20.
[0086]
When the operator commands an automatic calibration start, the automatic calibration unit 23 automatically performs the type of calibration selected and selected by the necessary calibration determination unit 22.
[0087]
FIG. 3 is a diagram showing an example of the state change of the apparatus and the type of calibration required at that time.
[0088]
In FIG. 3, the necessary calibration determination unit 22 selects all calibrations when the power is turned on (entirely or partly).
[0089]
When the detection distance FDD, shooting distance FCD, rotation center offset, tube voltage, tube current, and integration time have been changed since the previous scan, the calibration type indicated by the circle in the figure (or logical sum for multiple changes) ) Is selected.
[0090]
Then, when the temperature change becomes equal to or higher than the specified value as compared with the previous calibration, the air calibration and the rotation center calibration are selected.
[0091]
Also, the air calibration and the rotation center calibration are selected when the time elapsed from the previous calibration becomes a specified value or more.
[0092]
Here, each calibration is demonstrated in order.
[0093]
(Air calibration)
First, air calibration is calibration of the gain of the radiation detector 3.
[0094]
In the automatic calibration unit 23, the rotary table 5 is lowered, the X-ray is turned on, and an air image is collected in a state where nothing enters the X-ray beam 2.
[0095]
At this time, the gain of the radiation detector 3 is automatically set so that saturation does not occur.
[0096]
After this setting, a large number of air images are collected and averaged, and air data is created and stored.
[0097]
At the time of scanning, this air data is used for gain correction for each channel.
[0098]
(Strain calibration)
Further, the distortion calibration is a calibration of the distortion of the radiation detector 3.
[0099]
The distortion is mainly caused by the detection surface of the X-ray II being a curved surface, and varies depending on the detection distance FDD.
[0100]
In the automatic calibration unit 23, the grid table 11 is inserted into the front surface of the radiation detector 3 so that the rotating table 5 is lowered so that the subject 4 does not enter the X-ray beam 2.
[0101]
Next, the X-ray is turned on to capture a grid image, and a correction coefficient is obtained from the distortion and stored.
[0102]
At the time of scanning, this coefficient is used for distortion correction.
[0103]
(Slice surface calibration)
Furthermore, the slice plane calibration is a calibration for setting the position of the imaging plane 14 on the transmission image.
[0104]
The imaging plane 14 is a plane defined as a plane orthogonal to the rotation axis 13 through the X-ray focal point F, and changes on the transmission image due to a mechanism error when the detection distance FDD or the imaging distance FCD is changed.
[0105]
The automatic calibration unit 23 collects transmission images of the rotary table 5 while turning on the X-ray and moving the rotary table 5 up and down.
[0106]
Further, an image in which the gap 15 is most clearly visible is selected from a large number of transmission images, and a line passing through the center of the gap 15 is set and stored as a slice plane.
[0107]
This slice plane is used as reference coordinates for creating a cross-sectional image.
[0108]
(Rotation center calibration)
The rotation center calibration is a calibration for setting the position of the rotation axis 13 on the transmission image.
[0109]
The rotating shaft 13 changes on the transmission image due to a mechanism error when the detection distance FDD or the photographing distance FCD is changed.
[0110]
Also, when the tube voltage is changed, the X-ray focal point shifts and changes.
[0111]
The automatic calibration unit 23 collects transmission images of the subject 4 or the rotary table 5 over 360 degrees while turning on the X-ray and rotating the rotary table 5.
[0112]
Then, this transmission image is averaged by 360 degrees to create an average transmission image, from which the rotation center is obtained.
[0113]
In this case, in principle, since the average image is symmetrical with respect to the center of rotation, the center of rotation is automatically obtained by, for example, calculating the center of gravity using this.
[0114]
This rotation center line is used as a reference coordinate for creating a cross-sectional image.
[0115]
This rotation center calibration can also be performed using the transmission image itself of the subject 4 obtained by scanning.
[0116]
In this case, the cross-sectional image is reconstructed after performing the rotation center calibration after scanning.
[0117]
(FCD calibration)
Further, the FCD calibration is a calibration of an FCD value reading encoder (not shown) of the shift mechanism 8.
[0118]
If the shooting distance FCD value is different from the true value, the dimensions on the image change at the same ratio.
[0119]
The automatic calibration unit 23 scans and creates a cross-sectional image of the rotary table 5 itself.
[0120]
Then, the corrected shooting distance FCD value is obtained by multiplying the current shooting distance FCD value by the ratio dt / dg between the diameter dg of the rotary table 5 obtained from the cross-sectional image and the known actual measurement value dt, and the encoder is calibrated. Is done.
[0121]
In addition to the above-described calibrations, there is an offset calibration for obtaining the output of the radiation detector 3 when the X-ray is turned off. However, since this is normally always performed before scanning, the description thereof is omitted. (It can also be done selectively by the system).
[0122]
Next, when exchanging the sample, the sample door 31 is slid and opened (see FIG. 2).
[0123]
In addition, when performing maintenance such as adjustment and replacement of the X-ray tube 1 and the radiation detector 3, the maintenance door 32 is opened in addition to the sample door 31.
[0124]
As described above, in the CT scanner according to the present embodiment, the calibration is automatically performed only by inputting from the keyboard, so that the operation becomes extremely easy.
[0125]
Also, when there is a change in the status of the device, the appropriate type of calibration is automatically selected and displayed, so there is no need to worry about when and what calibration is necessary for the operator. It can be handled very easily, and erroneous operations can be reduced.
[0126]
Further, the sample can be exchanged by opening and closing the light and small sample door 31. When the sample is dropped into the inside, the maintenance door 32 can be opened and taken out from the front immediately. When the sample is heavy, the maintenance door 32 can be removed. The opening 30 can be opened and the opening 30 can be widened, and the operability is improved.
[0127]
Further, since the maintenance door 32 is on the front surface, an object can be placed on the side surface and the rear surface or attached to the wall, and the space factor is improved.
[0128]
Furthermore, since the sample door 31 is provided on the maintenance door 32, the opening at the time of maintenance can be made larger than the maintenance door 32 (the maintenance door 32 can be made small).
[0129]
(Other embodiments)
(A) In the above-described embodiment, the case where the automatic calibration is started by the operator's command has been described. However, the calibration required before the start of scanning can be automatically performed without this command. Good.
[0130]
(B) In the above embodiment, the case where the sample door 31 is the sliding door type and the maintenance door 32 is the door type has been described, but both types of doors may be used.
[0131]
(C) In the above-described embodiment, at least two of the doors of the sample door 31 and the maintenance door 32 are closed, or both of the sample door 31 and the maintenance door 32 are opened, or only the sample door 31 is opened. Other than that, as long as a state is taken, it is arbitrary.
[0132]
For example, the maintenance door 32 may have a structure that can be opened only when the sample door 31 is fully opened, or a structure that can be opened and closed independently, and the sample door 31 does not close when the maintenance door 32 is open. However, it may be a closed structure.
[0133]
(D) In the above-described embodiment, the shape of the two doors of the sample door 31 and the maintenance door 32 may be anything, and the arrangement relationship between them may not be up and down.
[0134]
(E) In the above embodiment, a radiation beam such as a γ-ray beam may be used as the radiation beam instead of the X-ray beam.
[0135]
(F) In the above embodiment, the radiation detector 3 may be a flat panel type two-dimensional detector, and may be similarly applied to a radiation detector that detects a radiation beam with one-dimensional spatial resolution. Is possible.
[0136]
(G) In the above embodiment, it is possible to add a function of switching the field size of the X-ray II of the radiation detector 3.
[0137]
In this case, when the visual field size is switched, air calibration, distortion calibration, slice plane calibration, and rotation center calibration are selected.
[0138]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a computed tomography apparatus that does not require skill in operation and is easy for an operator to handle.
[Brief description of the drawings]
FIG. 1 is a plan view and a front view showing an embodiment of a CT scanner according to the present invention.
2A and 2B are a plan view and a front view showing a configuration example of a shielding box in the CT scanner of the embodiment.
FIG. 3 is a diagram showing an example of a change in the state of the apparatus and the type of calibration required at that time.
FIG. 4 is a schematic diagram showing a system configuration example of a conventional high-resolution CT scanner.
FIG. 5 is a schematic diagram showing an example of a conventional calibration jig.
FIG. 6 is a schematic diagram showing a detailed configuration example of a conventional shielding box.
FIG. 7 is a schematic diagram showing another detailed configuration example of a conventional shielding box.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... X-ray tube 2 ... X-ray beam 3 ... Radiation detector 4 ... Subject 5 ... Rotary table 6 ... Rotation / lifting mechanism 7 ... Rotation center offset mechanism 8 ... Shift mechanism 9 ... Detector support frame 10 ... X-ray tube Support frame 11 ... grid plate 12 ... grid drive unit 13 ... rotating shaft 14 ... imaging surface 15 ... gap 16 ... high voltage generator 17 ... X-ray control unit 18 ... mechanism control unit 19 ... data processing unit 20 ... display unit 21 ... Scan control unit 22 ... Necessary calibration determination unit 23 ... Automatic calibration unit 24 ... Reconstruction unit 25 ... Shielding box 30 ... Opening 31 ... Sample door 32 ... Maintenance door 33 ... Rail 34 ... Lead glass 35 ... Hinge 101 ... X-ray tube DESCRIPTION OF SYMBOLS 102 ... X-ray beam 103 ... Detector 104 ... Subject 105 ... Rotary table 106 ... Rotation / lifting mechanism 107 ... Shift mechanism 108 ... Supporting part 109 ... Data processing part 110 ... Mechanism control part 1 1 ... X-ray control unit 112 ... X-ray II
113 ... Television camera 114 ... Shielding box 115 ... Opening 116 ... Sample door 118 ... Rotating shaft 119 ... Imaging surface 120 ... Grid plate 121 ... Acrylic plate 122 ... Grid (grid)
123 ... wire plate 124 ... acrylic plate 125 ... wire 126 ... center calibration phantom 127 ... acrylic pipe 128 ... wire 130 ... lead glass 131 ... rail 132 ... maintenance door.

Claims (3)

A radiation source emitting a radiation beam;
A radiation detector for detecting a radiation beam from the radiation source with a spatial resolution;
Rotating means for relatively rotating the subject within the radiation beam;
Reconstructing means for creating a cross-sectional image of the subject from transmission data from multiple directions of the subject obtained by the radiation detector during relative rotation by the rotating means;
Display means;
Determines the type of calibration that is needed from the state change of the device body selected, computed tomography, characterized in that the type of the selected calibration made and a required calibration determining means for displaying on said display means apparatus. The computed tomography apparatus according to claim 1,
The type of calibration determined by the necessary calibration determination means is at least one of air calibration, distortion calibration, slice plane calibration, rotation center calibration, and FCD calibration based on the type of calibration selected and displayed on the display means. A computer tomography apparatus comprising an automatic calibration means for automatically performing one calibration. The computed tomography apparatus according to claim 1 or 2,
A radiation shielding box having an opening for subject replacement, which contains at least the radiation source, the radiation detector, and the subject;
A computed tomography apparatus comprising a radiation shielding door which is divided into two parts covering the opening of the radiation shielding box and which can be opened and closed respectively.

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