CN110383051B

CN110383051B - X-ray inspection apparatus

Info

Publication number: CN110383051B
Application number: CN201880015777.1A
Authority: CN
Inventors: 长野雅実; 鹤祥司
Original assignee: Toshiba IT and Control Systems Corp
Current assignee: Toshiba IT and Control Systems Corp
Priority date: 2017-04-11
Filing date: 2018-03-20
Publication date: 2022-07-05
Anticipated expiration: 2038-03-20
Also published as: CN110383051A; JP6843683B2; JP2018179711A; WO2018190092A1

Abstract

The invention provides an X-ray inspection apparatus which can produce an X-ray perspective image of only a region required for reconstruction of a CT image. An image acquisition unit (71) acquires a reference image for determining a field-of-view-missing region and an image of a workpiece to be trimmed from an X-ray detector (3). An average luminance value calculation unit (72) calculates the average luminance value of an image without a field loss in a reference image. A missing field of view area determination unit (73) determines, for a captured fluoroscopic image, a pixel having a luminance less than a threshold value of the average luminance value calculated by the average luminance value calculation unit (72) as a missing field of view area. A clipped image acquisition unit (75) acquires X-ray fluoroscopic images other than the field-of-view missing region from the image obtained by imaging the workpiece. A reconstruction processing unit (8) reconstructs a CT image from the X-ray fluoroscopic images other than the missing field of view region.

Description

X-ray inspection apparatus

Technical Field

Embodiments of the present invention relate to an X-ray inspection apparatus that does not cause a field of view missing around a captured image.

Background

The X-ray inspection apparatus includes an X-ray radiation source, a table on which an inspection object (hereinafter, referred to as a workpiece) is placed, and an X-ray detector that receives X-rays transmitted through the workpiece. The X-rays emitted from the radiation source expand conically and reach the workpiece, and pass through the workpiece and further expand and reach the X-ray detector. X-rays attenuate in proportion to the square of the Distance from the X-ray source to the Detector (Focus to Detector Distance, FDD). On the other hand, the imaging magnification of a Computed Tomography (CT) image is a value obtained by dividing FDD by the Distance (Focus to Center Distance (FCD)) from the X-ray source to the Center of a sample table on which an imaging target is placed. Therefore, in order to capture a CT image with a desired imaging magnification and a good Signal-to-Noise ratio (Signal/Noise, S/N) at a high linear volume, it is sufficient to reduce FDD and FCD while maintaining the imaging magnification.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016 and 118394

Disclosure of Invention

Problems to be solved by the invention

However, if FDD is reduced, a field of view due to the X-ray irradiation angle is lost, that is, the X-ray is not irradiated to the range of the detector. The larger the detector used, the more likely field of view is missing. In a state where the field of view is missing, the following problem occurs in the CT image capturing.

(1) In reconstruction of a CT image, information on where a straight line connecting the X-ray source and the center of the sample stage is located in the detector is required. When the information is obtained from the symmetry (0 ° to 180 ° and 180 ° to 360 °) of the X-ray fluoroscopic image captured from the 360 ° direction, the missing field of view portion may become an obstacle and cannot be accurately obtained in some cases. The missing part of the field of view has a substantially constant brightness and good symmetry, and therefore has a large influence on the original symmetry determination of the fluoroscopic image.

(2) Even when a CT image can be reconstructed by accurately obtaining a straight line connecting the X-ray source and the center of the sample table, a missing field of view portion appears in the circumferential direction of the reconstructed CT image, and the reconstructed CT image becomes a fluoroscopic image and a CT image including unnecessary portions other than the X-ray irradiation angle. Therefore, the following problem arises in terms of image processing.

Example 1: when it is desired to automatically extract a portion of an object to be captured from a CT image, the average luminance value of the object is often used as a threshold, but both of the missing field of view regions may be regarded as the object.

Example 2: when three-dimensional data is created from a CT image, a field of view missing portion exists in the circumferential direction of the CT image, and thus the three-dimensional data becomes such that the field of view missing portion can be seen as if it were outside.

When the irradiation angle is larger than the light receiving area of the detector as described above, the problem of field missing does not occur because the entire area of the light receiving area is within the irradiation range of the X-rays even if the detector is brought close to the X-ray source, but when the irradiation angle is small, various problems occur with field missing if FDD is reduced. Therefore, in the case of an FDD requiring a small size of an object to be inspected, a large expansion ratio, or the like, a small detector dedicated for a small FDD is used instead of a large detector, and thus a field of view is not lost.

As described in patent document 1, it is known to crop a part of an image captured by X-ray, but these conventional techniques are merely techniques for extracting a desired region from a captured image by a user, and cannot be applied to the removal of field loss in the case of reducing the FDD of a detector.

The present embodiment is proposed to solve the problems of the prior art as described above. An object of the present embodiment is to provide an X-ray inspection apparatus capable of creating an X-ray fluoroscopic image of only a region necessary for reconstruction of a CT image.

Means for solving the problems

The X-ray inspection apparatus according to the first embodiment has the following configuration.

(1) An X-ray irradiation source, a table on which an inspection object is placed, and an X-ray detector receive X-rays transmitted through the inspection object and detect a transmission image thereof.

(2) A shift mechanism that moves the X-ray detector along an optical axis of X-rays.

(3) And a control unit that controls movement of the X-ray detector by the displacement mechanism.

(4) An image acquisition unit acquires a reference image for determining a field-of-view missing region and an image of an inspection object to be trimmed from the X-ray detector.

(5) An average luminance value calculation unit calculates an average luminance value of an image without a field loss in the reference image.

(6) And a missing field of view area determination unit that determines, as a missing field of view area, a pixel having a luminance less than a threshold of the average luminance value calculated by the average luminance value calculation unit, with respect to the captured X-ray fluoroscopic image.

(7) And a cropped image acquisition unit that acquires, from an image obtained by imaging the inspection object, the fluoroscopic image other than the missing-field-of-view region determined by the missing-field-of-view region determination unit as an image of the cropped region.

(8) And a reconstruction processing unit which reconstructs a CT image from the fluoroscopic image of the cropped region acquired by the cropped image acquiring unit.

In the first embodiment, the following configuration is preferably employed.

(1) And a boundary trimming unit for trimming a boundary between the missing-field-of-view region determined by the missing-field-of-view region determining unit and a region other than the missing-field-of-view region, from an image obtained by imaging the inspection target object.

The X-ray inspection apparatus according to the second embodiment has the following configuration.

(2) A shift mechanism that moves the X-ray detector along an optical axis of the X-ray.

(5) The setting value acquisition unit reads the following data input by the user in advance.

(1) X-ray irradiation angle (alpha)

(2) Detector spacing (mm/detector channel)

(3) Base FDD (L1)

(6) The reference irradiation range calculation unit obtains the irradiation range of the reference FDD (L1) as the reference irradiation range (W1) from the X-ray irradiation angle (α) acquired by the set value acquisition unit and the reference FDD (L1).

(7) And an irradiation range calculation unit for the imaging position, which calculates an irradiation range (W2) of an arbitrary FDD (L2) by the following formula 1 based on the values acquired by the set value acquisition unit and the reference irradiation range calculation unit.

Formula 1: the desired irradiation range (W2) ═ reference irradiation range (W1) × (arbitrary FDD (L2)/reference FDD (L1))

(8) The clipping region calculation unit calculates a clipping region by calculating that the irradiation range (W2) obtained by the imaging position irradiation range calculation unit corresponds to several detector channels by the following expression 2.

Formula 2: trimming area (W2)/detector spacing (mm/detector channel) for any FDD illumination area (W2)/detector spacing (mm/detector channel)

(9) And a trimmed image acquiring unit that acquires an X-ray fluoroscopic image of the trimmed area calculated by the trimmed area calculating unit from an image obtained by imaging the inspection target.

(10) And a reconstruction processing unit for reconstructing a CT image from the X-ray fluoroscopic image of the trimmed region acquired by the trimmed image acquisition unit.

In the second embodiment, the following configuration is preferably employed.

(1) And a storage unit that stores the clipping regions of the plurality of FDDs obtained by the clipping region calculation unit in association with each FDD.

(2) The trimmed image acquisition unit reads the corresponding trimmed region from the storage unit in accordance with the FDD of the imaging portion of the inspection target, and acquires an X-ray fluoroscopic image of the trimmed region.

Drawings

Fig. 1 is a block diagram showing the overall configuration of the first embodiment.

Fig. 2 is a diagram showing an example of an X-ray fluoroscopic image including a field-of-view missing region according to the first embodiment.

Fig. 3 is a block diagram showing the overall configuration of the second embodiment.

Fig. 4 is a diagram for explaining a method of determining a missing visual field region in the third embodiment.

Description of the symbols

1: x-ray tube

2: working table

3: x-ray detector

4: shifting mechanism

5: control unit

6: input unit

7: trimming processing part

71: image acquisition unit

72: average brightness value calculation unit

73: visual field missing region determination unit

74: boundary dressing part

75: trimming image acquisition unit

76: set value acquisition unit

77: reference irradiation range calculation unit

78: shooting position irradiation range calculation unit

79: clipping region calculation unit

8: reconfiguration processing unit

9: storage unit

L1: reference FDD

L2, L3, L4: arbitrary FDD

M1, M2, M3, M4: pruning area

W: workpiece

W1: reference irradiation range

W2: irradiation range of arbitrary FDD

α: angle of irradiation of X-rays

Detailed Description

[1. first embodiment ]

[1-1. Structure of embodiment ]

Hereinafter, the first embodiment will be described in detail with reference to the drawings. The first embodiment is for a person to clip using a threshold value set in advance for the brightness of a fluoroscopic image.

As shown in fig. 1, the X-ray inspection apparatus according to the present embodiment is configured such that an X-ray tube 1 as a radiation source, a table 2 on which a workpiece is placed, and an X-ray detector 3 that receives an X-ray beam emitted from the X-ray tube 1 are arranged at predetermined intervals.

The X-ray tube 1 emits a cone-shaped X-ray beam horizontally from a focal point thereof, and the X-ray beam passes through a workpiece mounted on the table 2 and reaches the X-ray detector 3. The table 2 is rotated about a vertical axis by a rotary table or an XY drive mechanism, not shown, or moved in a direction parallel to a direction of approaching and separating from the X-ray tube 1 and a moving direction of the X-ray detector 3.

The X-ray detector 3 detects an X-ray beam with a two-dimensional spatial resolution and outputs data for displaying a transmission image on a display or a film. The X-ray inspection apparatus stops the X-ray detector 3 at a position corresponding to a predetermined FDD determined by the size of the workpiece or a required imaging magnification, and images the workpiece. Therefore, the X-ray detector 3 is connected to a shift mechanism 4 as a drive source for movement and a control unit 5 for controlling the movement direction and the movement amount of the X-ray detector 3 by the shift mechanism 4. The control unit 5 moves the X-ray detector 3 in a direction in which it moves along the optical axis of the X-ray tube 1, that is, in a direction in which FDD changes. The control unit 5 is provided with an input unit 6 for a user to set a movement position or a movement direction of the X-ray detector 3 in advance. The input unit 6 may include an input device such as a keyboard and a mouse, an external device such as a network, and the like.

The X-ray detector 3 includes a trimming processing unit 7 that removes a field-of-view missing region from an image captured at the stop position. The trimming processing unit 7 of the present embodiment includes: an image acquisition unit 71, an average luminance value calculation unit 72, a missing field region determination unit 73, a boundary modification unit 74, and a clipped image acquisition unit 75.

The image acquisition unit 71 acquires a reference image for determining the field-of-view missing region and an image of the workpiece to be trimmed from the X-ray detector 3. The reference image is an X-ray fluoroscopic image in which no object is shown. The average luminance value calculation unit 72 calculates an average luminance value of a central portion of an image without a field of view missing in the reference image, for example, a portion of an oblique hatched area in the upper right of fig. 2. The missing-of-field region determination unit 73 determines, as a missing-of-field region, a pixel having a luminance less than a predetermined% of the average luminance value calculated by the average luminance value calculation unit 72, with respect to the taken fluoroscopic image. The predetermined% of the average luminance value is a threshold value such that it can be determined that the pixel belongs to the missing field of view, and the user sets the value in the trimming processing unit 7 from the input unit 6 in advance.

The boundary adjustment unit 74 adjusts the missing-field region so that the missing-field region becomes a square, because the missing-field region determination unit 73 determines in pixel units that the boundary between the missing-field region and the region without missing field becomes jagged. The adjustment method may be any conventionally known method. For example, the reference image is set as XY two-dimensional coordinates, and a straight line in the XY direction passing through the maximum value or the minimum value of the coordinates of the pixel determined as the missing field of view region is set as the outer edge of the missing field of view region.

The trimmed image acquisition unit 75 acquires a fluoroscopic image other than the field-of-view missing region acquired by the boundary trimming unit 74 from the image obtained by imaging the workpiece. On the output side of the clipped image acquiring unit 75, a reconstruction processing unit 8 is provided, and the reconstruction processing unit 8 reconstructs a CT image from the X-ray fluoroscopic images other than the missing field of view region.

A storage unit 9 is connected to each of the above-mentioned units, and the storage unit 9 is used for storing and appropriately reading data input from the input unit 6, data of an image read by the X-ray detector 3, a calculation result of the cropping unit 7, or data such as a determined field-of-view missing region. The storage unit 9 includes a storage device such as a memory or a hard disk.

[1-2. effects of embodiments ]

(1) Determination of missing field of view

In the present embodiment, the input unit 6 inputs FDD of the imaging position of the workpiece W, and the control unit 5 controls the shift mechanism 4 based on the FDD to stop the X-ray detector 3 at the input FDD position. In this state, a fluoroscopic image in which no object is shown is taken. By doing so, a fluoroscopic image having a central portion of the image without a field of view loss and a field of view loss region formed around the central portion can be obtained as shown in fig. 2. In general, the central portion of the image without field of view missing (the upper right oblique hatched portion in fig. 2) of the X-ray fluoroscopic image on which no object is displayed is a fluoroscopic image of air, and therefore has a higher brightness than the surrounding field of view missing region (the cross-hatched portion in fig. 2), while the field of view missing region receives no X-ray and therefore has a brightness of almost 0.

The fluoroscopic image of fig. 2 is output from the X-ray detector 3 to the image acquiring unit 71. The average luminance value calculation unit 72 calculates an average luminance value of the central portion of the image without a field loss from the fluoroscopic image input to the image acquisition unit 71. The missing-of-field area determination unit 73 determines pixels having the average luminance value calculated by the average luminance value calculation unit 72 and a luminance lower than a threshold value set by the user in advance from the input unit 6 for the captured fluoroscopic image, and regards the part of the pixels as a missing-of-field area.

The boundary adjustment unit 74 adjusts the boundary between the missing-field region determined by the missing-field region determination unit 73 on a pixel basis and the region without missing field so as to be a quadrangle. In the present embodiment, the reference image is set as XY two-dimensional coordinates, and a straight line in the XY direction passing through the maximum value or the minimum value of the coordinates of the pixels determined as the missing field of view region is set as the outer edge of the missing field of view region. The coordinates of the area with missing field of view or the area without missing field of view obtained in this way are stored in the storage unit 9 together with the corresponding FDD.

(2) Imaging of workpiece W

When the workpiece W is imaged, the X-ray detector 3 is stopped at the position of the FDD whose coordinates of the area with or without the missing field of view have been obtained as described above. In this state, the workpiece W is placed on the table 2, and a fluoroscopic X-ray image is taken. The X-ray fluoroscopic image detected by the X-ray detector 3 is output to the trimmed-image acquiring unit 75. The clipped image acquisition unit 75 reads out the coordinates corresponding to the FDD at the stop position of the X-ray detector 3 from the storage unit 9, and acquires an image other than the field-of-view missing region from the X-ray fluoroscopic image of the workpiece W based on the coordinate position.

The fluoroscopic images other than the missing field of view region obtained by the clipped image obtaining unit 75 are output to the reconstruction processing unit 8, and the reconstruction processing unit 8 reconstructs a CT image from the fluoroscopic images of the missing field of view region.

[1-3. effects of the embodiment ]

The present embodiment has the following effects.

(1) Since the image reconstruction can be performed from the fluoroscopic image of the field-of-view-free region, an appropriate CT image can be obtained in accordance with the actual state of the workpiece W.

(2) Regardless of the size of the X-ray detector 3 or the FDD, CT imaging can always be performed with the most suitable X-ray fluoroscopic image.

(3) Even when the X-ray detector 3 is brought close to the X-ray generation device side and the X-ray geometric magnification is enlarged, a fluoroscopic X-ray image and a CT image without a field of view loss can be obtained.

(4) By storing the FDD in the storage unit 9 in association with the image of the missing field of view, if the X-ray detector 3 is stopped at the FDD, the missing field of view can be determined not every time, but the fluoroscopic image of the missing field of view can be obtained from the X-ray fluoroscopic image obtained by imaging the workpiece W.

(5) Since the boundary trimming unit 74 performs adjustment so that the boundary between the missing field region and the missing field region determined in pixel units becomes a quadrangle, it is possible to obtain a fluoroscopic image of the missing field region with its outer edge trimmed to be beautiful.

[2. second embodiment ]

[2-1. Structure of embodiment ]

The trimming processing section 7 of the second embodiment is different from the first embodiment in configuration, and the other configurations are the same as those of the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The trimming processing section 7 of the second embodiment includes: a set value acquisition unit 76, a reference irradiation range calculation unit 77, an imaging position irradiation range calculation unit 78, and a trimming area calculation unit 79.

The set value acquisition unit 76 reads data (see fig. 3) described below that the user has input to the input unit 6 in advance.

(1) X-ray irradiation angle (alpha)

(2) Detector spacing (mm/detector channel)

(3) Reference FDD (L1) (FDD with an irradiation range coincident with the light receiving surface of the detector and without field of view loss)

The reference irradiation range calculation unit 77 calculates the irradiation range in the reference FDD (L1) as the reference irradiation range (W1) from the X-ray irradiation angle (α) acquired by the set value acquisition unit 76 and the reference FDD (L1). The scanning position irradiation range calculation unit 78 obtains an irradiation range (W2) of an arbitrary FDD (L2) by the following equation using the similarity of triangles from the values which are known by the set value acquisition unit 76 and the reference irradiation range calculation unit 77.

Formula 1: the desired irradiation range (W2) × (arbitrary FDD (L2)/reference FDD (L1) × (reference irradiation range (W1))

The clipped region calculation unit 79 calculates that the obtained irradiation range (W2) corresponds to several detector channels by the following equation, and obtains a clipped region.

[2-2. effects of embodiments ]

In the second embodiment, before the workpiece W is imaged, the following values are input from the input unit 6 and stored in the storage unit 9. These values are values inherent to the X-ray imaging apparatus to which the second embodiment is applied, and therefore, they are set once and do not need to be input every time the workpiece W is imaged.

(1) X-ray irradiation angle (alpha)

(2) Detector spacing (mm/detector channel)

(3) Base FDD (L1)

Then, the X-ray detector 3 is moved to the position of the FDD to be imaged in order to image the X-ray fluoroscopic image of the workpiece W. The movement of the X-ray detector 3 is FDD (L2) in which the imaging position of the workpiece W is input from the input unit 6, and the control unit 5 controls the displacement mechanism 4 based on the FDD to stop the X-ray detector 3 at the input FDD position. In the case of FDD in which the imaging position is not known in advance, such as when the X-ray detector 3 is moved manually, the FDD is automatically or manually set as the FDD of the imaging position (L2) and set in the input unit 6 in a state where the X-ray detector 3 is stopped at the imaging position.

In this way, since values necessary for executing the

above equations

1 and 2 can be obtained, the set value acquisition unit 76 of the trimming processing unit 7 reads these values and obtains the reference irradiation range (W1) as the irradiation range in the reference FDD (L1) in the reference irradiation range calculation unit 77. If the reference irradiation range is calculated once, the same value is obtained even when the FDD of the imaging position is different as long as the light receiving area of the X-ray detector 3 or the X-ray irradiation angle is not changed, and therefore, the reference irradiation range is stored in the storage unit 9, and calculation is not necessary next time or later.

Based on the values obtained in the above manner, the imaging position irradiation range calculation unit 78 obtains the irradiation range (W2) of FDD (L2) of the imaging position of the workpiece W according to equation 1. Then, based on these values, the clipping region calculation unit 79 obtains the clipping region according to equation 2.

In this state, an X-ray fluoroscopic image of the workpiece W is taken, and only the trimmed region obtained in the above manner, that is, the image of the portion corresponding to the irradiation range (W2) of FDD (L2), is extracted from the image, whereby an X-ray fluoroscopic image in which the missing field of view region is not included in the periphery can be taken.

In the second embodiment, data for calculating the trimming area and data for capturing the X-ray fluoroscopic image of the workpiece W are stored in the storage unit 9 and appropriately read out, so that either of them can be performed first.

[2-3. effects of the embodiment ]

The second embodiment has the following characteristic effects in addition to the common effects with the first embodiment.

(1) In the second embodiment, the region to be clipped can be easily determined by geometric calculation from the X-ray irradiation angle (α), the size of the detector obtained from the reference irradiation range (W1), and the FDD information (L1, L2) as shown in fig. 3.

(2) The second embodiment also eliminates the need to capture a perspective image of the air at the position where the workpiece is captured in advance and calculate the trimming area using the threshold value of the brightness, as in the first embodiment, and therefore can quickly and easily determine the trimming area. Further, since the boundary line between the missing-of-field region and the missing-of-field region is also formed linearly, the calculation for trimming the boundary portion is not necessary, which is also advantageous in this respect.

[3 ] third embodiment ]

The third embodiment is a modification of the second embodiment. As shown in fig. 4, by the method of the second embodiment, trimming areas (M1, M2, M3, M4) serving as references are obtained by using a plurality of FDDs (L1, L2, L3, L4) which are expected to image the workpiece W, and are registered in the storage unit 9.

When the workpiece W is imaged, the X-ray detector 3 is moved to an area of the FDD registered in the storage unit 9, which is the most suitable for imaging of the workpiece, to image an X-ray fluoroscopic image, and a field-of-view missing area is removed from the imaged X-ray fluoroscopic image by using a trimming area corresponding to the FDD. On the other hand, when there is no FDD that is most suitable for imaging the workpiece W out of the registered FDDs, that is, when imaging is performed at an arbitrary FDD position, the trimming area at the arbitrary FDD position is determined from the similarity of the triangles using the value of the nearest FDD registered in the storage unit 9 and the value of the trimming area corresponding thereto.

In this manner, in the third embodiment, the X-ray fluoroscopic image of the air is taken at a position where the field of view is largely absent, a position where the field of view is not absent, or a position between both positions (which may be a plurality of positions), and the clipped region is obtained and registered. Since the clipping region increases or decreases according to the geometric system, the clipping region at a position where no image is captured is obtained by interpolation.

In the third embodiment, the clipped regions of a plurality of imaging regions are stored in advance in association with the FDD of each imaging region, an appropriate clipped region is called up in accordance with the FDD of the imaging position of the workpiece W, and the missing field of view region in the X-ray fluoroscopic image can be removed. As a result, it is not necessary to calculate the cropped region every time the user moves to a new FDD, and an X-ray fluoroscopic image of the field-free region can be obtained quickly. In addition, even in the FDD in which no clipping region is registered, a correct clipping region can be obtained by simple calculation by performing geometric interpolation with respect to the FDD.

[4 ] other embodiments ]

The present invention is not limited to the above-described embodiments, and constituent elements may be modified and embodied in the implementation stage within a range not departing from the gist thereof. In addition, various inventions can be formed by appropriate combinations of a plurality of constituent elements disclosed in the embodiments. For example, several constituent elements may be removed from all the constituent elements shown in the embodiments. Further, the constituent elements of the different embodiments may be appropriately combined. Specifically, the following other embodiments are also included.

(1) The X-ray tube 1, the table 2, and the X-ray detector 3 may be arranged in parallel with the mounting surface of the X-ray inspection apparatus, or may be arranged in parallel with each other in the vertical direction.

(2) The X-ray detector 3 is not limited to a flat plate orthogonal to the optical axis of the X-ray, and may be a light receiving surface curved with a vertical axis passing through the X-ray focal point as a center.

(3) In the first embodiment, as in the third embodiment, an X-ray fluoroscopic image of the air may be taken at a position where the field of view is largely lost, a position where the field of view is not lost, or a position between both positions (a plurality of positions may be used), and a region to be trimmed may be obtained and registered in the storage unit 9. In this case, since the clipped region increases or decreases according to the geometric system, the clipped region at the position where the X-ray fluoroscopic image of the air is not captured is obtained by interpolating the clipped region registered in the storage unit 9 with respect to the FDD position of the imaging position of the workpiece W.

Claims

1. An X-ray inspection apparatus including an X-ray radiation source, a table on which an inspection object is placed, and an X-ray detector for receiving X-rays transmitted through the inspection object and detecting a transmission image of the X-rays, the X-ray inspection apparatus comprising:

a shift mechanism that moves the X-ray detector along an optical axis of X-rays;

a control unit that controls movement of the X-ray detector by the displacement mechanism;

an image acquisition unit that acquires, from the X-ray detector, a reference image and an image of an inspection object to be trimmed, the reference image being an X-ray fluoroscopic image in which no object is reflected;

an average luminance value calculation unit that calculates an average luminance value in a region where no field of view is missing, with a region near a central portion of an expected image where no field of view is missing in the reference image as the region where no field of view is missing;

a missing field of view area determination unit that determines, as a missing field of view area, a pixel having a luminance less than a threshold value of the average luminance value calculated by the average luminance value calculation unit, with respect to the captured X-ray fluoroscopic image;

a cropped image acquisition unit that acquires, from an image obtained by imaging the inspection target, an X-ray fluoroscopic image other than the missing-field-of-view region determined by the missing-field-of-view region determination unit as an image of a cropped region; and

and a reconstruction processing unit for reconstructing a CT image from the X-ray fluoroscopic image of the trimmed region acquired by the trimmed image acquisition unit.

2. The X-ray inspection apparatus according to claim 1, comprising a boundary trimming unit that trims a boundary between the missing field of view region determined by the missing field of view region determination unit and a region other than the missing field of view region from an image obtained by imaging the inspection object.