JP7727455B2 - Computed tomography system - Google Patents

Description

The present invention relates to technology for inspecting objects such as baggage using X-ray transmission images.

There are computed tomography (CT) systems that use X-ray transmission images taken from multiple directions by changing the relative positions of the X-ray device and the object being examined (including a person) to generate computed tomography (CT) images that represent the three-dimensional shape of the object.

Meanwhile, a method of inspecting baggage or other items for inspection using an X-ray imaging device to check whether the item contains any detectable objects such as blades has become widespread.

Even if an object to be detected, such as a blade, is contained within an inspection target such as baggage, the shape of the object may not be recognizable in the X-ray image depending on the shape of the object and its orientation within the inspection target. As a result, the object may be overlooked during inspection.

To solve the above problems, a method has been proposed in which a computed tomography system is used to generate a computed tomography image of the object being inspected, and the generated computed tomography image is used to check whether the object being inspected contains any detectable objects.

For example, Patent Document 1 proposes an X-ray inspection device that, when taking X-ray images of an object to be inspected from multiple directions, identifies the relative positional relationship between the object to be inspected and the X-ray imaging device for each image, and generates a computed tomographic image using the multiple X-ray transmission images taken based on the identified positional relationship.

Japanese Patent Application Laid-Open No. 2017-223468

Generating a computed tomography image requires taking multiple X-ray transmission images and then synthesizing them into a three-dimensional computed tomography image, which takes much more time than taking a single X-ray transmission image.

For example, when inspecting the baggage of passersby, using computed tomography images can significantly reduce inspection throughput compared to inspecting each piece of baggage using a single X-ray image, potentially resulting in long lines of passersby waiting for inspection.

In light of the above circumstances, the present invention provides a means for increasing inspection throughput compared to conventional techniques when using computed tomography images to inspect whether an object being inspected contains a detection target.

The present invention proposes, as a first aspect, a computed tomography system that generates a computed tomography image using multiple X-ray transmission images taken by an X-ray imaging device while changing the relative position of the object to be inspected and the X-ray imaging device around a vertical axis, and that stops processing to generate the computed tomography image if a detection object within the object to be inspected is detected based on any of the X-ray transmission images while the multiple X-ray transmission images are being sequentially taken.

With the computed tomography system according to the first aspect, when a detection object within an object under inspection is detected based on one of multiple X-ray transmission images taken to generate a computed tomography image, the inspection can be completed without generating a computed tomography image for that object, thereby increasing inspection throughput compared to conventional technology that requires the generation of a computed tomography image for each object under inspection.

In the computed tomography system according to the first aspect described above, a second aspect may be adopted in which the captured X-ray transmission image is displayed and the processing for generating the computed tomography image is stopped in response to an operation by a user viewing the X-ray transmission image.

With the computed tomography system according to the second aspect, the user can determine whether the object to be detected is contained within the object being inspected by viewing the displayed X-ray transmission image. If it is determined that the object to be detected is contained within the object being inspected, the user can perform a specified operation to stop the subsequent processing for generating a computed tomography image, thereby shortening the time required for the inspection.

In the computed tomography system according to the second aspect described above, a third aspect may be adopted in which the X-ray transmission images are displayed sequentially so that the angular difference between the relative positions around the vertical axis of adjacent X-ray transmission images captured in the display order gradually decreases.

With the computed tomography system of the third aspect, when an object to be detected is contained within an object to be inspected, the probability of an X-ray image showing a recognizable shape of the object to be detected being displayed at an early stage is increased compared to when X-ray transmission images taken from different directions at equal angular intervals are displayed sequentially, thereby reducing the time required for the inspection.

In the computed tomography system according to the first aspect described above, a fourth aspect may be adopted in which, when an object to be detected is image-recognized from the captured X-ray transmission image, processing for generating a computed tomography image is stopped.

In the computed tomography system according to the fourth aspect, the computed tomography system determines whether or not a detection target is present in the X-ray transmission image, eliminating the need for the user to make that determination.

In the computed tomography system according to the fourth aspect described above, a fifth aspect may be adopted in which image recognition of the object to be detected is attempted sequentially from the X-ray transmission images so that the angular difference in the relative position around the vertical axis between adjacent X-ray transmission images taken in the order in which image recognition is performed gradually decreases.

With the computed tomography system according to the fifth aspect, when a detection object is contained within an inspection object, the probability of the detection object being recognized at an early stage is increased, compared to when X-ray transmission images taken from different directions at equal angular intervals are sequentially recognized, thereby reducing the time required for the inspection.

In the computed tomography system according to the third or fifth aspect above, a sixth aspect may be adopted in which the X-ray imaging device captures X-ray transmission images by scanning using a line sensor, and the X-ray imaging device sequentially captures X-ray transmission images in a sequence such that the angular difference in the relative position around the vertical axis when capturing the X-ray transmission images in the capturing order gradually decreases.

The computed tomography system according to the sixth aspect uses a line sensor, which is less expensive than a panel sensor but takes a long time to capture an X-ray transmission image. However, if an object to be detected is found in the X-ray transmission image, the inspection is terminated without capturing any further X-ray transmission images, which significantly reduces the time required for the inspection.

In the computed tomography system according to any one of the first to sixth aspects described above, a seventh aspect may be adopted in which the angular difference around the vertical axis between the shooting directions of two adjacent X-ray transmission images taken to generate a computed tomography image can be changed.

According to the computed tomography system of the seventh aspect, the angular difference around the vertical axis between the shooting directions of two adjacent X-ray transmission images taken to generate a computed tomography image can be changed depending on the situation in which the computed tomography system is used (such as the waiting status of passersby, the required accuracy of the examination, etc.), so that the examination can be performed with the desired throughput depending on the situation.

1 is a diagram showing the overall configuration of a computed tomography system according to an embodiment; 1A and 1B are diagrams for explaining the behavior of a computed tomography system according to an embodiment; 1A and 1B are diagrams for explaining the behavior of a computed tomography system according to an embodiment; 1A and 1B are diagrams for explaining the behavior of a computed tomography system according to an embodiment; FIG. 2 is a block diagram showing the functional configuration of a terminal device according to an embodiment. FIG. 10 is a diagram illustrating a screen displayed by a terminal device according to an embodiment. 10A and 10B are diagrams illustrating how the relative positions of baggage and an X-ray imaging device in the vertical direction are changed in a computed tomography system according to a modified example.

[Embodiment]
A computer tomography system 1 according to one embodiment of the present invention will be described below. Fig. 1 is a diagram showing the overall configuration of the computer tomography system 1. However, Fig. 1 also shows components that are not actually visible from the outside, such as those located inside the housing 11, inside the wall covering the bottom of the conveyors 17 and 18, and on the other side of the housing 11.

The housing 11 is a box-shaped component that houses the X-ray imaging device, and is lined on the inside with lead, for example, to prevent the X-rays emitted by the X-ray imaging device from leaking out.

The housing 11 has an opening on its side wall on the upstream side (left side in Figure 1) that serves as the entrance for baggage P (an example of an object to be inspected). A lead curtain 12 is attached to the housing 11 so that it hangs down from the upper edge of the opening to block this entrance. The lead curtain 12 is made up of multiple strips of rubber containing lead, and like a noren curtain, it bends to allow baggage P to move from outside the housing 11 toward inside the housing 11, and returns to its original shape to block the entrance after the baggage P has passed through the entrance of the housing 11. The lead curtain 12 reduces the amount of X-rays that leak out from the entrance of the housing 11 when the X-ray imaging device irradiates X-rays inside the housing 11.

In addition, the housing 11 has an opening on the side wall on the downstream side (right side in Figure 1) of the housing 11, which serves as an exit for baggage P. A lead curtain 13 is attached to the housing 11 so that it hangs down from the upper edge of the opening to block this exit. The lead curtain 13 has the same structure as the lead curtain 12; it bends to allow baggage P to move from inside the housing 11 to outside the housing 11, and returns to its original shape to block the exit after the baggage P has passed through the exit of the housing 11. The lead curtain 13 reduces the amount of X-rays that leak out from the exit of the housing 11 when the X-ray imaging device irradiates X-rays inside the housing 11.

The X-ray irradiator 14 and panel sensor 15, which constitute the X-ray imaging device, are located within the housing 11. The X-ray irradiator 14 is located, for example, on the inside surface of the housing 11, below the entrance of the upstream side wall, and irradiates X-rays that spread, for example, in a conical shape, toward the panel sensor 15. The panel sensor 15 is located, for example, on the inside surface of the housing 11, below the exit of the downstream side wall, and has a large number of light-receiving elements arranged in a plane. These light-receiving elements measure the intensity of the X-rays irradiated from the X-ray irradiator 14 and transmitted through the baggage P, thereby generating a signal representing an X-ray transmission image.

The X-ray irradiator 14 and panel sensor 15 may be arranged in any manner as long as the X-rays irradiated by the X-ray irradiator 14 are directed toward the baggage P that has been moved to the imaging position by the elevator/rotation device 16, as described below, and the X-rays that pass through the baggage P are directed toward the panel sensor 15.

The lifting and rotating device 16 is a device that lifts and lowers baggage P that has entered the housing 11 and rotates it about a vertical axis. The lifting and rotating device 16 includes a table 161, which is a disk-shaped member on which the baggage P rests, a plurality of rollers 162 that are provided so that the baggage P can easily move on the upper surface of the table 161 due to gravity, and a stopper 163 that is arranged near the outer edge of the table 161. The lifting and rotating device 16 can perform the following operations.
(1) An operation of raising and lowering the table 161. (2) An operation of rotating the table 161 around a vertical axis. (3) An operation of rotating the table 161 around a horizontal axis and tilting the upper surface of the table 161 relative to the horizontal plane. (4) An operation of inserting and removing the stopper 163 into and from the table 161.

The stopper 163 is located near the outer edge located on the lower side when the table 161 rotates around a horizontal axis and the upper surface is tilted relative to the horizontal plane. The role of the lifting and rotating device 16, which performs the above-mentioned operations, will be described later.

Conveyor 17 is located upstream of housing 11 and is a device that transports baggage P toward housing 11. Conveyor 18 is located downstream of housing 11 and is a device that transports baggage P discharged from housing 11 downstream.

The controller 19 is a data processing device that controls the operation of the X-ray irradiation unit 14, panel sensor 15, elevator/rotation device 16, conveyor 17, and conveyor 18. The behavior of the X-ray irradiation unit 14, panel sensor 15, elevator/rotation device 16, conveyor 17, and conveyor 18, which operate under the control of the controller 19, will be described later.

The controller 19 communicates data with the terminal device 10 via wired or wireless means. The controller 19 generates X-ray transmission image data representing an X-ray transmission image using a signal generated by the panel sensor 15, and transmits the generated X-ray transmission image data to the terminal device 10. Depending on the situation, the controller 19 also receives from the terminal device 10 stop instruction data (described below) that instructs the stopping of processing for capturing an X-ray transmission image, resume instruction data (described below) that instructs the restart of processing for capturing an X-ray transmission image that has been stopped, and end instruction data (described below) that instructs the ending of processing for capturing an X-ray transmission image.

The terminal device 10 is a computer used by an inspector. The terminal device 10 is equipped with a memory for storing various data, a processor for processing various data according to programs stored in the memory, a communications interface for communicating data with the controller 19, a display for displaying screens containing various information to the user, and input devices such as a keyboard for accepting user operations on the terminal device 10. The display and input devices of the terminal device 10 may be built into the main unit, or may be external devices connected to the input/output interface of the main unit.

Figures 2, 3, and 4 are diagrams for explaining the behavior of the X-ray irradiation unit 14, panel sensor 15, elevator/rotation device 16, conveyor 17, and conveyor 18 (hereinafter referred to as the behavior of the computed tomography system 1), which operate under the control of the controller 19.

Figure 2 shows the behavior of the computed tomography system 1 when it moves baggage P, which is placed on the upstream side of the conveyor 17, onto the table 161 of the elevator/rotator 16. Figure 2(A) shows the state in which baggage P is being transported by the conveyor 17 toward the housing 11. In this state, the table 161 is tilted downward toward the downstream side, with the upstream edge of its upper surface at a height slightly lower than the upper surface of the conveyor 17. In addition, a stopper 163 protrudes upward on the downstream side of the table 161. After moving into the housing 11 by the conveyor 17, the baggage P moves on the rollers 162 due to gravity and comes to a stop on the table 161 when it hits the stopper 163. Figure 2(B) shows the state in which baggage P has stopped on the table 161 in this manner.

Then, the table 161 rotates slightly around the horizontal axis, and the top surface becomes horizontal. The stopper 163 then retracts into the table 161. As a result, the baggage P is placed on the horizontal table 161, as shown in Figure 2 (C).

Figure 3 shows the behavior of the computed tomography system 1 when capturing an X-ray transmission image of baggage P. As shown in Figure 3(A), the table 161 descends so that the baggage P is positioned in front of the X-ray irradiation unit 14. Next, as shown in Figure 3(B), the X-ray irradiation unit 14 and panel sensor 15 capture an X-ray transmission image of the baggage P. The captured X-ray transmission image is immediately displayed on the terminal device 10 (described below).

Next, as shown in Figure 3(C), with the X-ray irradiation unit 14 stopping X-ray irradiation, the table 161 rotates a predetermined angle around the vertical axis. After that, the capturing of X-ray transmission images shown in Figure 3(B) and the rotation of the table 161 are repeated, and X-ray transmission images of the baggage P taken from multiple different angles are displayed sequentially on the terminal device 10.

In this embodiment, the table 161 is rotated around its vertical axis so that the rotation angle around the vertical axis (the angular difference between the relative positions of the baggage P and the X-ray imaging device) between adjacent X-ray transmission images taken in the order of imaging by the X-ray irradiation unit 14 and panel sensor 15, i.e., the order of display by the terminal device 10, gradually decreases.

For example, if the position of the table 161 around the vertical axis when the first X-ray transmission image is taken is the reference position (0 degrees), the X-ray transmission images are taken sequentially at positions where the table 161 is rotated around the vertical axis (e.g., clockwise when viewed from above) by the following angles:

(1) First stage: 1st sheet: 0 degrees, 2nd sheet: 30 degrees, 3rd sheet: 60 degrees, 4th sheet: 90 degrees (2) Second stage: 5th sheet: 110 degrees, 6th sheet: 130 degrees, 7th sheet: 150 degrees, 8th sheet: 170 degrees, 9th sheet: 190 degrees (3) Third stage: 10th sheet: 200 degrees, 11th sheet: 210 degrees, 12th sheet: 220 degrees, 13th sheet: 230 degrees, 14th sheet: 240 degrees, 15th sheet: 250 degrees, 16th sheet: 260 degrees, 17th sheet: 270 degrees, 18th sheet: 280 degrees, 19th sheet: 290 degrees, 20th sheet: 300 degrees , 21st sheet: 310 degrees, 22nd sheet: 320 degrees, 23rd sheet: 330 degrees, 24th sheet: 340 degrees, 25th sheet: 350 degrees (4) 4th stage, 26th sheet: 10 degrees, 27th sheet: 20 degrees, 28th sheet: 40 degrees, 29th sheet: 50 degrees, 30th sheet: 70 degrees, 31st sheet: 80 degrees, 32nd sheet: 100 degrees, 33rd sheet: 120 degrees, 34th sheet: 140 degrees, 35th sheet: 160 degrees, 36th sheet: 180 degrees

The first stage (1) above is a stage in which the table 161 is rotated 30 degrees around the vertical axis to capture X-ray transmission images.

The second stage (2) above is a stage in which the table 161 is rotated 20 degrees around the vertical axis to capture X-ray transmission images.

The third stage (3) above is a stage in which the table 161 is rotated 10 degrees around the vertical axis to capture X-ray transmission images.

The fourth step (4) above is a step in which X-ray images are taken at angles that have not yet been taken in steps 1 to 3, rotated 10 degrees from the reference position.

When all 36 X-ray images have been taken, or when an inspector who looks at the X-ray images displayed on the terminal device 10 determines that a detection target such as a blade is visible in the X-ray image and performs an operation such as clicking the "End" button (described below) on the terminal device 10, the table 161 will rotate around the vertical axis to the reference position and then rise so that its top surface is slightly higher than the top surface of the conveyor 18, as shown in Figure 3 (D).

Figure 4 shows the behavior of the computed tomography system 1 when it moves baggage P placed on the table 161 inside the housing 11 toward the downstream side of the conveyor 18. First, as shown in Figure 4(A), the table 161 rotates slightly around the horizontal axis, tilting its upper surface downward toward the downstream side. As a result, the baggage P moves from the table 161 toward the conveyor 18 due to gravity.

Next, as shown in Figure 4 (B), the conveyor 18 transports the baggage P downstream. During this time, the table 161 lowers slightly while maintaining its inclination in preparation for receiving the next baggage. In addition, the stopper 163 protrudes upward from the table 161.

The above explains the behavior of the X-ray irradiation unit 14, panel sensor 15, elevator/rotation device 16, conveyor 17, and conveyor 18, which operate under the control of the controller 19.

Figure 5 is a block diagram showing the functional configuration of the terminal device 10. That is, when the processor of the terminal device 10 performs data processing in accordance with the program according to this embodiment, the terminal device 10 functions as a device having the components shown in Figure 5. The functional configuration of the terminal device 10 is described below.

The X-ray transmission image acquisition unit 121 receives X-ray transmission image data from the controller 19. The computed tomography image generation unit 122 generates a computed tomography image using 36 X-ray transmission images representing the X-ray transmission image data received by the X-ray transmission image acquisition unit 121 from the controller 19.

The image recognition unit 123 recognizes detectable objects such as blades from each of the X-ray transmission images represented by the X-ray transmission image data received by the X-ray transmission image acquisition unit 121 and the computed tomography images generated by the computed tomography image generation unit 122.

Note that various known image recognition methods may be employed by the image recognition unit 123 to recognize the detection target from the image. For example, a machine learning model may be constructed using training data in which an X-ray image of the detection target is used as an explanatory variable and the determination result that "it is a detection target" is used as an objective variable. By inputting the image represented by the X-ray image data received by the X-ray image acquisition unit 121 as an explanatory variable, the model can output the determination result as the probability that the image contains an image of the detection target. Furthermore, a machine learning model may be constructed using training data in which a computed tomography image of the detection target is used as an explanatory variable and the determination result that "it is a detection target" is used as an objective variable. By inputting the computed tomography image generated by the computed tomography image generation unit 122 as an explanatory variable, the model can output the determination result as the probability that the image contains an image of the detection target.

The display unit 124 displays to the inspector a screen (hereinafter referred to as the image display screen) containing information such as the image represented by the X-ray transmission image data received by the X-ray transmission image acquisition unit 121, the image generated by the computed tomography image generation unit 122, and the judgment results by the image recognition unit 123.

Figure 6 is a diagram illustrating an example of an image display screen. Figure 6 (A) illustrates an example of the image display screen displayed by the display unit 124 immediately after the first X-ray transmission image is taken of the baggage currently being inspected. Area A1 of the image display screen displays the last X-ray transmission image and computed tomography image taken of that baggage in a large size. Area A2 of the image display screen displays all X-ray transmission images and computed tomography images already taken of that baggage in a small size. Note that by clicking on any of the images displayed in area A2, the inspector can have the clicked image displayed in a large size in area A1 instead of the last X-ray transmission image or computed tomography image taken.

In area A3 of the image display screen, if an inspector looks at the image displayed in area A1 or A2 and determines that a detection target such as a blade is visible in either image, an "End" button will be displayed to end the series of processes for the baggage currently being inspected without carrying out any further processing to generate a computed tomographic image (including processing to capture an X-ray transmission image).

Figure 6 (B) shows an example of the image display screen displayed by the display unit 124 immediately after the first X-ray transmission image is captured.

Figure 6(C) shows an example of the image display screen displayed by the display unit 124 immediately after all 36 X-ray transmission images have been captured. In area A4 of the image display screen in Figure 6(C), a message such as "Computed tomography image is being generated" is displayed.

Figure 6 (D) shows an example of an image display screen displayed by the display unit 124 after a computed tomographic image has been generated. Area A1 in Figure 6 (D) displays the computed tomographic image generated by the computed tomographic image generation unit 122. The examiner can rotate the computed tomographic image displayed in area A1 by dragging it up, down, left, or right with the cursor, for example, to check the three-dimensional shape of the object shown in the computed tomographic image from the desired direction.

Figure 6 (E) shows an example of an image display screen that is displayed by the display unit 124 when the image recognition unit 123 determines that the X-ray transmission image contains an image of the detection object with a probability equal to or greater than a predetermined threshold (e.g., a probability of 50% or greater). Area A1 of this image display screen displays the X-ray transmission image that has been determined to contain an image of the detection object with a probability equal to or greater than the threshold. Furthermore, in the image displayed in area A1, the area containing the detection object is displayed in a manner that distinguishes it from other areas. In the example of Figure 6 (E), the area containing the detection object is distinguished from other areas by being surrounded by a dashed rectangle. The display manner for distinguishing the area containing the detection object from other areas is not limited to this. For example, an area containing the detection object may be displayed in a different color from other areas, or only the area containing the detection object may be displayed in a flashing color.

In addition, area A4 of the image display screen in FIG. 6(E) displays a message such as "Dangerous object detected." When this image display screen is displayed, that is, when the image recognition unit 123 determines that the X-ray transmission image contains an image of the object to be detected with a probability equal to or greater than a threshold, the transmission unit 126 (described below) of the terminal device 10 transmits stop instruction data to the controller 19 instructing it to stop the process of capturing the X-ray transmission image. In response to this stop instruction data, under the control of the controller 19, the X-ray irradiation unit 14 and the like stop the process of capturing the X-ray transmission image. Therefore, in addition to the "End" button, area A3 of the image display screen in FIG. 6(E) displays a "Resume" button for instructing the restart of the stopped process of capturing the X-ray transmission image.

Figure 6 (F) shows an example of an image display screen that the display unit 124 displays when the image recognition unit 123 determines that the computed tomography image contains an image of the detected object with a probability equal to or greater than a predetermined threshold (e.g., a probability of 50% or greater). The image display screen in Figure 6 (F) is similar to the image display screen in Figure 6 (E), except that the image displayed in area A1 is a computed tomography image rather than an X-ray transmission image. This concludes the description of the image display screen displayed by the display unit 124.

Referring to Figure 5, the functional configuration of the terminal device 10 will be described further. The operation reception unit 125 receives operations by the inspector on the image display screen (for example, operations such as clicking on a button displayed in area A3). The transmission unit 126 transmits stop instruction data, restart instruction data, end instruction data, etc. to the controller 19 in accordance with the inspector's operations received by the operation reception unit 125. This concludes the description of the functional configuration of the terminal device 10.

When an inspector views the X-ray transmission image or computed tomography image displayed on the image display screen (Figure 6) and finds an object that appears to be a detection target, they click the "End" button or other means to cause the computed tomography system 1 to end the series of processes for the baggage currently being inspected. The inspector then opens the baggage being transported downstream on the conveyor 18 and checks whether the baggage contains any detection targets.

On the other hand, if the inspector does not find any object that appears to be the target of detection in any of the 36 X-ray transmission images or computed tomography images displayed on the image display screen, he or she can click the "End" button or similar to cause the computed tomography system 1 to end the series of processes for the baggage currently being inspected. In this case, the inspector will not do anything to the baggage being transported downstream on the conveyor 18.

Furthermore, if the image recognition unit 123 determines that the X-ray transmission image or computed tomography image contains an image of the detection object with a probability equal to or greater than the threshold, the inspector looks at the X-ray transmission image or computed tomography image displayed on the image display screen (Figures 6(E) and 6(F)) and determines whether the image recognition unit 123's determination is correct. If the inspector determines that the image recognition unit 123's determination is incorrect, the inspector clicks the "Resume" button, etc., to cause the computed tomography system 1 to resume the processing of the currently suspended baggage that is the current inspection target. On the other hand, if the inspector determines that the image recognition unit 123's determination is correct, the inspector clicks the "End" button, etc., to cause the computed tomography system 1 to end the series of processes for the currently inspection target baggage. The inspector then opens the baggage being transported downstream on the conveyor 18 and checks whether the detection object is contained in the baggage.

Once the inspector has completed the inspection of the current baggage being inspected, as described above, they will move on to inspect the next baggage.

With the above-described computed tomography system 1, if an inspector determines that a detection target is present in one of the multiple X-ray transmission images taken sequentially at different angles to generate a computed tomography image, the series of processes for generating the computed tomography image is terminated without executing any unexecuted processes (the process of capturing the untaken X-ray transmission image and the process of generating the computed tomography image). Therefore, the time required for inspection is reduced compared to when the inspector determines whether the baggage contains a detection target based on the computed tomography image after the generation of the computed tomography image is complete.

Furthermore, with the above-described computed tomography system 1, if an image of a detection object is included in an X-ray transmission image or a computed tomography image, the detection object is detected by the image recognition unit 123. This reduces the risk that the detection object will be overlooked by the inspector.

Furthermore, with the above-described computed tomography system 1, the rotation angle of the baggage when capturing X-ray transmission images is initially large and then changed to a smaller angle. Therefore, if the baggage contains a detection target, the detection target is likely to appear in a recognizable shape in the first few X-ray transmission images, and the time required for inspection is further reduced compared to when the baggage is rotated at a fixed rotation angle.

[Modification]
The above-described embodiment may be modified in various ways within the scope of the technical concept of the present invention. These modifications are shown below. Note that two or more of the modifications shown below may be combined as appropriate.

(1) In the above-described embodiment, the hand-held P rotates by rotating the table 161 in order to change the angle at which the X-ray imaging device (X-ray irradiation unit 14 and panel sensor 15) images the baggage. However, the method of changing the relative positions of the baggage and the X-ray imaging device to change the angle at which the X-ray imaging device images the baggage is not limited to this. For example, the baggage may not rotate, but the X-ray imaging device may rotate around the baggage.

(2) In the above-described embodiment, the X-ray imaging device is equipped with a panel sensor. However, a line sensor may be used instead of the panel sensor. When a line sensor is used, the relative vertical positions of the baggage and the X-ray imaging device must be continuously changed during X-ray irradiation in order to capture a two-dimensional X-ray transmission image. Figure 7 is a diagram illustrating how the relative vertical positions of the baggage and the X-ray imaging device are changed in a computed tomography system 1 according to this modified example.

In the example of Figure 7 (A), a line sensor 25 is placed in place of the panel sensor 15 at a position opposite the X-ray irradiation unit 14. While X-rays are being emitted from the X-ray irradiation unit 14, a table 161 moves up or down. As the table 161 moves vertically, the line sensor 25 sequentially receives X-rays that have passed through different positions in the vertical direction of the baggage P. As a result, the entire baggage P is scanned with X-rays, and a two-dimensional X-ray transmission image is generated.

In the example of Figure 7 (B), a line sensor 25 is also placed opposite the X-ray irradiation unit 14 instead of the panel sensor 15. However, the computed tomography system 1 according to this modification includes a transport unit 26 that transports the line sensor 25 vertically. While X-rays are being emitted from the X-ray irradiation unit 14, the table 161 remains stationary in front of the X-ray irradiation unit 14, but the transport unit 26 raises or lowers the line sensor 25. As the line sensor 25 moves vertically, it sequentially receives X-rays that have passed through different positions in the vertical direction of the baggage P. As a result, the entire baggage P is scanned with X-rays, and a two-dimensional X-ray transmission image is generated.

(3) The magnitude and order of the rotation angle of the table 161 for capturing multiple X-ray transmission images, as illustrated in the above-described embodiment, are merely examples and may be modified in various ways. For example, baggage P may be rotated around the vertical axis at the following angles in sequence, and images may be captured by the X-ray imaging device.

1st: 0 degrees, 2nd: 90 degrees, 3rd: 180 degrees, 4th: 270 degrees, 5th: 30 degrees, 6th: 60 degrees, 7th: 120 degrees, 8th: 150 degrees, 9th: 210 degrees, 10th: 240 degrees, 11th: 300 degrees, 12th: 330 degrees, 13th: 10 degrees, 14th: 20 degrees, 15th: 40 degrees, 16th: 50 degrees, 17th: 70 degrees, 18th: 80 degrees, 19th: 100 degrees, 20th: 110 degrees, 21st: 130 degrees, 22nd: 140 degrees, 23rd: 160 degrees, 24th image: 170 degrees, 25th image: 190 degrees, 26th image: 200 degrees, 27th image: 220 degrees, 28th image: 230 degrees, 29th image: 250 degrees, 30th image: 260 degrees, 31st image: 280 degrees, 32nd image: 290 degrees, 33rd image: 310 degrees, 34th image: 320 degrees, 35th image: 340 degrees, 36th image: 350 degrees (4) In the above-described embodiment , the angular difference around the vertical axis between the imaging directions of two adjacent X-ray transmission images taken to generate a computed tomographic image is 10 degrees. The angular difference around the vertical axis between the imaging directions of two adjacent X-ray transmission images taken to generate a computed tomographic image is not limited to 10 degrees. Furthermore, depending on the situation in which the computed tomography system 1 is used (such as the required accuracy of the computed tomography image and the required throughput of the inspection), for example, depending on the setting work of an inspector, etc., the angular difference around the vertical axis between the shooting directions of two adjacent X-ray transmission images taken to generate a computed tomography image may be changeable.

(5) Some of the components that are included in the terminal device 10 in the above-described embodiment may be included in the controller 19 instead of the terminal device 10. For example, the controller 19 may include the computed tomography image generation unit 122 and the image recognition unit 123. In this case, the terminal device 10 may receive data indicating the results of the image recognition performed in the controller 19 and image data representing the computed tomography image generated in the controller 19 from the controller 19, and display the image display screen using this data.

(6) In the above-described embodiment, the series of processes for generating a computed tomography image by the computed tomography system 1 is terminated when the inspector performs an operation such as clicking the "End" button. In addition to this, or instead, when the image recognition unit 123 recognizes a detection target from an X-ray transmission image or a computed tomography image, the series of processes for generating a computed tomography image by the computed tomography system 1 may be terminated without the inspector's operation.

(7) In the above-described embodiment, the X-ray transmission image and the computed tomography image are displayed on the terminal device 10. However, the terminal device 10 may be configured to display the recognition results of the detected object by the image recognition unit 123, but not to display the X-ray transmission image and the computed tomography image. If the accuracy of the detection of the detected object by the image recognition unit 123 is sufficiently high, the inspector will only need to determine whether or not it is necessary to open the baggage and check the contents based on the recognition results by the image recognition unit 123, and there will be no need to display the images to the inspector.

(8) In the above-described embodiment, the movement of baggage from conveyor 17 to table 161 and the movement of baggage from table 161 to conveyor 18 are achieved by tilting table 161 relative to the horizontal. The method of moving baggage from conveyor 17 to table 161 and from table 161 to conveyor 18 is not limited to this. For example, instead of rollers 162 being driven rollers, rollers that are driven to rotate by a motor or the like may be used to transport baggage on table 161. Furthermore, a mechanism for pushing baggage from conveyor 17 into housing 11 using an arm or the like may be provided near the entrance of housing 11, or a mechanism for pushing baggage from inside housing 11 onto conveyor 18 using an arm or the like may be provided near the exit of housing 11.

1...Computer tomography system, 10...Terminal device, 11...Housing, 12...Lead curtain, 13...Lead curtain, 14...X-ray irradiation unit, 15...Panel sensor, 16...Lifting and rotating device, 17...Conveyor, 18...Conveyor, 19...Controller, 25...Line sensor, 26...Transport unit, 121...X-ray transmission image acquisition unit, 122...Computer tomography image generation unit, 123...Image recognition unit, 124...Display unit, 125...Operation reception unit, 126...Transmission unit, 161...Table, 162...Roller, 163...Stopper.

Claims (7)

A computed tomography system that generates a computed tomography image using a plurality of X-ray transmission images taken by an X-ray imaging device while changing the relative position of the object to be inspected and the X-ray imaging device around a vertical axis, and that stops processing to generate the computed tomography image if a detection object within the object to be inspected is detected based on any of the X-ray transmission images while the plurality of X-ray transmission images are being sequentially taken . The computed tomography system according to claim 1 , wherein the captured X-ray transmission image is displayed, and processing for generating a computed tomography image is stopped in response to an operation by a user who has viewed the X-ray transmission image. 3. The computed tomography system according to claim 2, wherein the X-ray transmission images are displayed in sequence so that the angular difference between the relative positions around the vertical axis when the X-ray transmission images adjacent to each other in the display order were captured becomes smaller in stages. The computed tomography system according to claim 1 , wherein when an object to be detected is image-recognized from the captured X-ray transmission image, processing for generating a computed tomography image is stopped. 5. The computed tomography system according to claim 4, wherein image recognition of the object to be detected is attempted from the X-ray transmission images in sequence so that the angular difference between the relative positions around the vertical axis when adjacent X-ray transmission images were taken in the order in which image recognition is performed becomes smaller in stages. 6. The computed tomography system according to claim 3, wherein the X-ray imaging device captures X-ray transmission images by scanning using a line sensor, and the X-ray imaging devices sequentially capture X-ray transmission images in a sequence such that the angular difference of the relative position around the vertical axis when capturing the X-ray transmission images in the sequence of capture becomes smaller in stages. 7. The computer tomography system according to claim 1, wherein an angular difference about a vertical axis between the imaging directions of two adjacent X-ray transmission images taken to generate a computer tomography image can be changed.