X-ray imaging device and x-ray tube

Abstract

The invention provides an X-ray imaging device and an X-ray tube. This X-ray imaging device is provided with an X-ray tube and a control unit, and the control unit performs control such that electrons are simultaneously irradiated from a first electron irradiation unit and a second electron irradiation unit for each of a plurality of imaging angles; and setting a first relative focal position of the first electron irradiation unit at the first imaging angle, a second relative focal position of the second electron irradiation unit at the first imaging angle, and a third relative focal position of the first electron irradiation unit at the second imaging angle, and the fourth relative focal positions of the second electron irradiation unit at the second imaging angle differ so as not to overlap each other.

Description

Technical Field

[0001] This invention relates to an X-ray imaging device and an X-ray tube. Background Technology

[0002] Previously, X-ray imaging devices were known. Such devices are disclosed, for example, in U.S. Patent No. 9,153,408.

[0003] U.S. Patent No. 9,153,408 discloses an X-ray CT imaging apparatus (X-ray imaging device) for performing computed tomography (CT) of a subject. The X-ray CT imaging apparatus includes an X-ray tube, a detector, a subject mount for mounting the subject, and a computer (control unit). The X-ray tube irradiates X-rays toward the subject, which rotates together with the subject mount. The detector detects the X-rays irradiated from the X-ray tube. The computer generates a CT image based on multiple projection image data acquired by the detector. The X-ray tube includes a single cathode element (electron irradiation unit) and a target. By irradiating electrons toward a focal point on the target using the cathode element, X-rays are emitted from the focal point on the target toward the detector.

[0004] Although not disclosed in the specification of U.S. Patent No. 9,153,408, in an X-ray CT imaging apparatus (X-ray imaging device), when generating CT images, multiple projection image data are acquired by capturing images of the subject from various shooting angles. To generate high-resolution CT images, a sufficient number of shooting angles (fields of view) of projection image data is required, but acquiring a sufficient number of shooting angles of projection image data increases the shooting time. If the number of shooting angles remains low without increasing the shooting time for acquiring projection image data, artifacts caused by the low number of shooting angles (low field of view) are generated in the reconstructed image (CT image). Therefore, it is desirable to suppress the increase in the shooting time for acquiring projection image data and reduce artifacts caused by the low number of shooting angles. Summary of the Invention

[0005] The present invention was made to solve the aforementioned problems. One object of the present invention is to provide an X-ray imaging apparatus and an X-ray tube, wherein the increase in the imaging time spent acquiring projected image data can be suppressed, and artifacts caused by a small number of imaging angles can be reduced.

[0006] An X-ray imaging apparatus includes: an X-ray tube comprising at least a first electron irradiation section and a second electron irradiation section for irradiating electrons at different focal positions of a target; a detector for detecting X-rays emitted from the X-ray tube; a subject mount disposed between the X-ray tube and the detector, and for mounting a subject; a rotation mechanism for rotating one of the imaging section comprising the X-ray tube and the detector and the subject mount section to change the imaging angle of the subject; and a control unit for acquiring multiple projection image data at each of multiple imaging angles from the detector, generating a CT image based on the acquired multiple projection image data, wherein the control unit performs the following control: simultaneously irradiating electrons from the first electron irradiation section and the second electron irradiation section at each of the multiple imaging angles; and differentiating the first relative focal position of the first electron irradiation section relative to the subject at the first imaging angle, the second relative focal position of the second electron irradiation section relative to the subject at the first imaging angle, the third relative focal position of the first electron irradiation section relative to the subject at the second imaging angle, and the fourth relative focal position of the second electron irradiation section relative to the subject at the second imaging angle in a manner that does not overlap with each other.

[0007] Additionally, an X-ray tube is used in an X-ray imaging device that acquires multiple projected image data at multiple shooting angles and generates CT images based on the acquired multiple projected image data. The X-ray tube includes at least a first electron irradiation unit and a second electron irradiation unit that simultaneously irradiate electrons at different focal positions of a target. The focal distance between the first focal point of the first electron irradiation unit and the second focal point of the second electron irradiation unit, and the number of focal points in the target are preset in a manner in which the first relative focal point of the first electron irradiation unit relative to the subject at the first shooting angle, the second relative focal point of the second electron irradiation unit relative to the subject at the first shooting angle, the third relative focal point of the first electron irradiation unit relative to the subject at the second shooting angle, and the fourth relative focal point of the second electron irradiation unit relative to the subject at the second shooting angle are different from each other.

[0008] In the X-ray imaging apparatus, electrons are simultaneously irradiated onto different focal positions of the target from multiple electron irradiation units, including a first electron irradiation unit and a second electron irradiation unit, according to each of the multiple imaging angles. This allows for the acquisition of multiple projected image data corresponding to the number of electron irradiation units for each imaging angle. Therefore, the number of acquired projected image data can be increased without increasing the imaging time. Furthermore, by making the first to fourth relative focal positions different in a non-overlapping manner, the imaging angles of the subject in the projected image data acquired according to each imaging angle, corresponding to the number of electron irradiation units, are different from each other. Therefore, projected image data at different imaging angles can be acquired from each of the acquired multiple projected image data. Thus, a sufficient number of imaging angles (fields of view) of projected image data can be acquired from the increased number of projected image data. For these reasons, the increase in imaging time spent acquiring projected image data can be suppressed, and artifacts caused by a small number of imaging angles can be reduced. Here, in this specification, the term "relative focal position" refers to the relative position of the focal spot formed on the target of an X-ray tube that rotates relative to the subject. By rotating the subject-mounting part or the X-ray tube through a rotating mechanism, the relative focal positions of the first electron irradiation part and the second electron irradiation part relative to the subject change.

[0009] Furthermore, in the X-ray tube, electrons are simultaneously irradiated onto different focal positions of the target from multiple electron irradiation units, including a first electron irradiation unit and a second electron irradiation unit, at each of the multiple shooting angles. This allows for the acquisition of multiple projection image data corresponding to the number of electron irradiation units at each shooting angle. Therefore, the number of acquired projection image data can be increased without increasing the shooting time. Additionally, since the focal distance between the first focal point of the first electron irradiation unit and the second focal point of the second electron irradiation unit, and the number of focal points in the target are preset in a manner where the first to fourth relative focal points do not overlap, projection image data at different shooting angles can be acquired from each of the acquired multiple projection image data. Therefore, a sufficient number of shooting angles (fields of view) of projection image data can be acquired from the increased projection image data. For these reasons, the increase in shooting time spent acquiring projection image data can be suppressed, and artifacts caused by a small number of shooting angles can be reduced. Attached Figure Description

[0010] Figure 1 This is a schematic diagram showing the overall structure of an X-ray imaging apparatus according to one embodiment.

[0011] Figure 2This diagram is used to illustrate a structure in which electrons are simultaneously irradiated from multiple electron irradiation units.

[0012] Figure 3 It is a schematic diagram used to illustrate the structure of multiple electron emission sections.

[0013] Figure 4 This is a diagram used to illustrate the positional relationship of the relative focal positions in one embodiment.

[0014] Figure 5 This is a diagram used to illustrate the positional relationship of the relative focal positions of the first comparative example.

[0015] Figure 6 This is a diagram used to illustrate the number of relative focal positions and the positional relationship between the relative focal positions in one embodiment.

[0016] Figure 7 This is a diagram used to illustrate the number of relative focal positions and the positional relationship between the relative focal positions in the second comparative example.

[0017] Figure 8 This is a flowchart used to illustrate the acquisition, processing, and reconstruction of X-ray images.

[0018] Figure 9 This is a diagram used to illustrate the comparison results between tomographic images obtained by the X-ray imaging apparatus of the third and fourth comparative examples and tomographic images obtained by the X-ray imaging apparatus of one embodiment.

[0019] Figure 10 These are enlarged views and charts used to illustrate the comparison results between tomographic images obtained by the X-ray imaging apparatus of the third and fourth comparative examples and tomographic images obtained by the X-ray imaging apparatus of one embodiment. Detailed Implementation

[0020] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0021] First, refer to Figures 1-3 The overall structure of the X-ray imaging apparatus 100 according to one embodiment will be described.

[0022] like Figure 1As shown, the X-ray imaging apparatus 100 is a device that captures X-ray images of a subject 90 and generates a CT image 82. The X-ray imaging apparatus 100 of this embodiment is used, for example, for non-destructive examination purposes. The subject 90 is not particularly limited as long as it is an object other than a living organism. The X-ray imaging apparatus 100 acquires projection image data 81 (X-ray image data) of the subject 90 around its circumference from the subject mounting section 3 on which the subject 90 is mounted, and constructs a tomographic image based on the acquired projection image data 81.

[0023] The X-ray imaging apparatus 100 includes: an X-ray tube 1, a detector 2, a subject mounting section 3, a rotation mechanism 4, and a control device 20. The X-ray tube 1 and the detector 2 constitute an imaging section 5 for capturing X-ray images.

[0024] X-ray tube 1 is configured to irradiate a subject 90 disposed on a subject mount 3 with X-rays 70. X-ray tube 1 is configured to generate X-rays 70 by applying a high voltage. X-ray tube 1 is positioned opposite detector 2, separated from subject mount 3. X-ray tube 1, subject mount 3, and detector 2 are arranged horizontally. In this embodiment, X-ray tube 1 is configured as a micro-focal X-ray tube with a focal spot size of micrometers. Alternatively, X-ray tube 1 may be configured as an X-ray tube with a focal spot size of millimeters.

[0025] like Figure 2 As shown, the X-ray tube 1 includes multiple electron irradiation sections 10. Each of the multiple electron irradiation sections 10 simultaneously irradiates electrons 71 onto different focal positions 13 on the target 11. In this embodiment, the X-ray tube 1 includes a first electron irradiation section 10a, a second electron irradiation section 10b, and a third electron irradiation section 10c. Each of the first electron irradiation section 10a, the second electron irradiation section 10b, and the third electron irradiation section 10c simultaneously irradiates electrons 71 onto different focal positions 13 on the target 11. Furthermore, detailed information regarding the structure of the X-ray tube 1 will be described later.

[0026] Detector 2 is configured to detect X-rays 70 emitted from X-ray tube 1. The X-rays 70 emitted from X-ray tube 1 pass through the subject 90 and incident on the detection surface of detector 2. Detector 2 is configured to convert the detected X-rays 70 into electrical signals. Thus, an X-ray image reflecting the transmission of X-rays 70 through the subject 90 is obtained. Detector 2 is, for example, a flat panel detector (FPD). Detector 2 includes multiple conversion elements (not shown) and pixel electrodes (not shown) disposed on the multiple conversion elements. The multiple conversion elements and pixel electrodes are arranged in a matrix within the detection surface at a predetermined period (pixel spacing).

[0027] The detector 2 is configured to simultaneously detect X-rays 70 based on electrons 71 irradiated by the first electron irradiation unit 10a, X-rays 70 based on electrons 71 irradiated by the second electron irradiation unit 10b, and X-rays 70 based on electrons 71 irradiated by the third electron irradiation unit 10c. The detector 2 converts the X-rays 70 based on the first electron irradiation unit 10a, the second electron irradiation unit 10b, and the third electron irradiation unit 10c into electrical signals. The detection signal (image signal) including the first detection signal (first image signal) of the X-rays 70 based on the first electron irradiation unit 10a, the second detection signal (second image signal) of the X-rays 70 based on the second electron irradiation unit 10b, and the third detection signal (third image signal) of the X-rays 70 based on the third electron irradiation unit 10c is sent to the image processing unit 23, which will be described later.

[0028] The subject placement unit 3 is configured to be disposed between the X-ray tube 1 and the detector 2, and to place the subject 90. The subject placement unit 3 includes a subject stage for placing the subject 90.

[0029] The rotating mechanism 4 rotates one of the imaging section 5, which includes the X-ray tube 1 and the detector 2, and the subject mounting section 3. Thus, the rotating mechanism 4 is configured to adjust the imaging angle 6 (refer to...) of the subject 90. Figure 2 The rotation mechanism 4 causes one of the imaging unit 5 and the subject mounting unit 3 to rotate about the rotation axis 4a. The rotation axis 4a is orthogonal to the straight line (representative line of the X-ray beam) that runs from the X-ray tube 1 through the subject 90 on the subject mounting unit 3 toward the detector 2. In this embodiment, the rotation axis 4a passes through the subject mounting unit 3 and is vertical.

[0030] In this embodiment, the rotating mechanism 4 rotates the subject-carrying part 3 about the rotation axis 4a in the horizontal plane. The rotating mechanism 4 does not rotate the shooting part 5. The rotating mechanism 4 includes a motor (not shown) and a reducer (not shown) for rotating the subject-carrying part 3.

[0031] As the subject mounting section 3 rotates, the subject 90 mounted on the subject mounting section 3 rotates about the rotation axis 4a in the horizontal plane. Through this rotation, the shooting angle 6 of the subject 90 (refer to...) changes. Figure 2 The shooting angle 6 is the relative angle between the subject 90 and the shooting unit 5. In this embodiment, the shooting angle 6 is the angle of the subject mounting unit 3 around the rotation axis 4a, with the origin angle (initial angle) of the rotation mechanism 4 set to 0 degrees. Figure 2 The image shows an example of the subject mount 3 after rotating from the origin at a certain shooting angle 6. The rotation mechanism 4 can rotate the subject mount 3 at any angle so that the subject 90 is positioned at any shooting angle 6.

[0032] like Figure 1 As shown, the control device 20 includes a control unit 21, a storage unit 25, and an input / output unit 26. The control device 20 may include, for example, a personal computer (PC). The control device 20 is connected to a display device 27 and an input device 28.

[0033] The control unit 21 is a computer including a central processing unit (CPU), a graphics processing unit (GPU), read-only memory (ROM), and random access memory (RAM). The control unit 21 performs prescribed control by causing the CPU to execute a predetermined program 80. The control unit 21 includes a main control unit 22, an image processing unit 23, and a shooting control unit 24 as a functional structure. That is, the control unit 21 functions as the main control unit 22, the image processing unit 23, and the shooting control unit 24 by causing the CPU to execute the predetermined program 80. Furthermore, the image processing unit 23 and the shooting control unit 24 are examples of the "control unit" claimed in the claims.

[0034] The main control unit 22 sets the imaging conditions of the X-ray imaging device 100 or controls the start and stop of imaging by executing the program 80 stored in the storage unit 25.

[0035] The image processing unit 23 acquires multiple projected image data 81 at each of the multiple shooting angles 6 from the detector 2. In this embodiment, the image processing unit 23 acquires from the detector 2 a first detection signal (converting X-rays 70 based on the first electron irradiation unit 10a into electrical signals), a second detection signal (converting X-rays 70 based on the second electron irradiation unit 10b into electrical signals), and a third detection signal (converting X-rays 70 based on the third electron irradiation unit 10c into electrical signals) at each of the shooting angles 6. The image processing unit 23 generates projected image data 81 based on the acquired first detection signal, the acquired second detection signal, and the acquired third detection signal. That is, the image processing unit 23 generates projected image data 81 according to each of the first to third detection signals from the detector 2 at each of the shooting angles 6. As described above, by utilizing the rotation mechanism 4 to change the shooting angle 6 of the subject 90, X-ray images of the subject 90 are captured by the imaging unit 5, which includes the first electron irradiation unit 10a to the third electron irradiation unit 10c, at each of the preset multiple shooting angles 6. The projected image data 81 is data based on the X-ray image of each of the first detection signal to the third detection signal acquired according to each shooting angle 6.

[0036] The acquisition of projected image data 81 based on the first to third detection signals for each angle of the shooting angle 6 is performed within a pre-set entire predetermined angle range. The pre-set predetermined angle range is 360 degrees (1 revolution). However, the pre-set predetermined angle range is not limited to 360 degrees (1 revolution), and is not particularly limited as long as it is 180 degrees (half a revolution) or more. In addition, the multiple shooting angles 6 are each angle set according to equal angular intervals obtained by dividing the predetermined angle range (360 degrees (1 revolution)) by the number of shooting angles.

[0037] Here, as Figure 4 As shown in (c), the first relative focus position 7a of the first electronic irradiation unit 10a relative to the subject 90 at the first shooting angle 6a, the second relative focus position 7b of the second electronic irradiation unit 10b relative to the subject 90 at the first shooting angle 6a, the third relative focus position 7c of the third electronic irradiation unit 10c relative to the subject 90 at the first shooting angle 6a, the fourth relative focus position 7d of the first electronic irradiation unit 10a relative to the subject 90 at the second shooting angle 6b, the fifth relative focus position 7e of the second electronic irradiation unit 10b relative to the subject 90 at the second shooting angle 6b, and the sixth relative focus position 7f of the third electronic irradiation unit 10c relative to the subject 90 at the second shooting angle 6b are different from each other in a non-overlapping manner.

[0038] That is, the shooting angles 6 of the subject 90 in the projected image data 81 based on the first detection signal to the third detection signal based on the first shooting angle 6a are different from each other, the shooting angles 6 of the subject 90 in the projected image data 81 based on the first detection signal to the third detection signal based on the second shooting angle 6b are different from each other, and the shooting angles 6 of the subject 90 in the projected image data 81 based on the first detection signal to the third detection signal based on the first shooting angle 6a and the shooting angles 6 of the subject 90 in the projected image data 81 based on the first detection signal to the third detection signal based on the second shooting angle 6b are all different from each other.

[0039] Furthermore, for ease of explanation, the numbers marked at the relative focal positions 7 are sequentially assigned according to the number of electron irradiation units 10. Therefore, the fourth relative focal position 7d in this embodiment is an example of the "third relative focal position of the first electron irradiation unit relative to the subject at the second shooting angle" in the claim, and the fifth relative focal position 7e in this embodiment is an example of the "fourth relative focal position of the second electron irradiation unit relative to the subject at the second shooting angle" in the claim.

[0040] like Figure 1 As shown, the image processing unit 23 is configured to generate a CT image 82 based on multiple acquired projection image data 81. The image processing unit 23 performs reconstruction processing on a set of projection image data 81 (called a projection dataset) based on each of the first to third detection signals for each angle of the shooting angle 6 (360 degrees), thereby generating the CT image 82. The CT image 82 is an image reflecting the three-dimensional structure of the subject 90, reconstructed from X-ray images (projection image data 81) based on each of the first to third detection signals for each angle of the multiple shooting angles 6 through computational processing. The CT image 82 can be a tomographic image of the subject 90, a three-dimensional image, or other forms.

[0041] The imaging control unit 24 controls the operation of the X-ray tube 1 and the rotation mechanism 4. Specifically, the imaging control unit 24 controls the simultaneous irradiation of electrons 71 from the first electron irradiation unit 10a, the second electron irradiation unit 10b, and the third electron irradiation unit 10c at each of the multiple imaging angles 6.

[0042] In addition, the shooting control unit 24 performs the following control: the first relative focus position 7a of the first electronic irradiation unit 10a relative to the subject 90 at the first shooting angle 6a, the second relative focus position 7b of the second electronic irradiation unit 10b relative to the subject 90 at the first shooting angle 6a, the third relative focus position 7c of the third electronic irradiation unit 10c relative to the subject 90 at the first shooting angle 6a, the fourth relative focus position 7d of the first electronic irradiation unit 10a relative to the subject 90 at the second shooting angle 6b, the fifth relative focus position 7e of the second electronic irradiation unit 10b relative to the subject 90 at the second shooting angle 6b, and the sixth relative focus position 7f of the third electronic irradiation unit 10c relative to the subject 90 at the second shooting angle 6b are different from each other in a non-overlapping manner.

[0043] The storage unit 25 is configured to include both volatile and non-volatile storage devices. The storage unit 25 stores the program 80, various setting information (not shown) related to X-ray image acquisition by the X-ray imaging device 100, etc. The storage unit 25 stores multiple acquired projection image data 81, and CT images 82 generated based on these projection image data 81.

[0044] The input / output unit 26 includes various interfaces for inputting and outputting signals to the control device 20. The input / output unit 26 is connected to the display device 27 and the input device 28. The display device 27 is, for example, a liquid crystal display. The input device 28 includes a keyboard and a mouse. The image processing unit 23 acquires detection signals (image signals) from the detector 2 via the input / output unit 26. The main control unit 22 sends instructions such as start or stop of shooting to the shooting control unit 24 via the input / output unit 26.

[0045] (Structure of an X-ray tube)

[0046] like Figure 2 As shown, the X-ray tube 1 includes a target 11 and multiple electron irradiation units 10. The target 11 and the multiple electron irradiation units 10 are housed in a vacuum container 12.

[0047] X-ray tube 1 is configured such that electrons 71 are irradiated from electron irradiation unit 10, which serves as cathode, and target 11, which serves as anode, by applying a voltage between them, and X-rays 70 are generated from target 11 by colliding the irradiated electrons 71 with target 11.

[0048] Multiple electron irradiation units 10 are configured to irradiate electrons 71 onto different focal positions 13 on the target 11. In this embodiment, the electron irradiation units 10 include three: a first electron irradiation unit 10a, a second electron irradiation unit 10b, and a third electron irradiation unit 10c. Furthermore, the number of electron irradiation units 10 is not particularly limited. The X-ray tube 1 may have two or more electron irradiation units 10. The first electron irradiation unit 10a, the second electron irradiation unit 10b, and the third electron irradiation unit 10c are arranged in a plane of rotation orthogonal to the rotation axis 4a of the rotation mechanism 4.

[0049] The first electron irradiation unit 10a, the second electron irradiation unit 10b, and the third electron irradiation unit 10c simultaneously irradiate electrons 71 toward different focal positions 13 of the target 11. Each of the first electron irradiation unit 10a, the second electron irradiation unit 10b, and the third electron irradiation unit 10c irradiates electrons 71 simultaneously according to each of the multiple shooting angles 6, based on the control of the shooting control unit 24. The first electron irradiation unit 10a irradiates electrons 71 toward the first focal position 13a (first focal point) of the target 11. As a result, X-rays 70 are emitted from the first focal position 13a corresponding to the first electron irradiation unit 10a toward the detector 2. The second electron irradiation unit 10b irradiates electrons 71 toward the second focal position 13b (second focal point) of the target 11. As a result, X-rays 70 are emitted from the second focal position 13b corresponding to the second electron irradiation unit 10b toward the detector 2. The third electron irradiation unit 10c irradiates electrons 71 toward the third focal position 13c (third focal point) of the target 11. As a result, X-rays 70 are emitted from the third focal point position 13c corresponding to the third electron irradiation unit 10c toward the detector 2.

[0050] The first electron irradiation unit 10a, the second electron irradiation unit 10b, and the third electron irradiation unit 10c are each positioned such that the distance from the first focal point position 13a (first focal point) to the rotation axis 4a passing through the subject mounting unit 3, the distance from the second focal point position 13b (second focal point) to the rotation axis 4a passing through the subject mounting unit 3, and the distance from the third focal point position 13c (third focal point) to the rotation axis 4a passing through the subject mounting unit 3 are approximately equal. Therefore, the distances from the first relative focal point position to the ninth relative focal point position (7a to 7i) to the rotation axis 4a passing through the subject mounting unit 3 are each approximately equal.

[0051] That is, such as Figure 4 As shown in (b), the shooting control unit 24 is configured such that, as the shooting angle 6 changes, the first relative focus position to the ninth relative focus position (7a to 7i) are arranged on different positions on an arc that do not overlap with each other, centered on the rotation axis 4a of the rotation mechanism 4.

[0052] like Figure 3 As shown, the X-ray tube 1 includes an electron irradiation unit moving mechanism 14. The electron irradiation unit moving mechanism 14 is configured to change the distance between the first electron irradiation unit 10a and the second electron irradiation unit 10b, and the distance between the second electron irradiation unit 10b and the third electron irradiation unit 10c. The electron irradiation unit moving mechanism 14 is configured to move at least two of the first electron irradiation unit 10a, the second electron irradiation unit 10b, and the third electron irradiation unit 10c in a direction substantially orthogonal to the optical axis of the X-ray 70 and along the rotation axis 4a of the rotation mechanism 4. The electron irradiation unit moving mechanism 14 includes a motor, etc., for moving the first electron irradiation unit 10a, the second electron irradiation unit 10b, and the third electron irradiation unit 10c.

[0053] The structure of the target 11 is not particularly limited. The target 11 can be either a reflective target or a transmissive target. A reflective target is a type of target that has a surface that is obliquely inclined relative to the electron 71, and emits X-rays 70 in a direction different from the direction in which the electron 71 flies by reflecting X-rays 70 through the oblique surface. A transmissive target is a type of target that has a pair of (front and back) surfaces orthogonal to the electron 71, and emits X-rays 70 from the other surface by passing through the target 11 through the collision of the electron 71 with one of the surfaces. In addition, the target 11 can be fixed in the vacuum container 12, or it can be rotated by a drive source such as a motor. That is, the X-ray tube 1 can also have a so-called rotating anode type structure.

[0054] A target 11 is provided relative to one of the plurality of electron irradiation units 10. The target 11 is provided relative to the first electron irradiation unit 10a, the second electron irradiation unit 10b, and the third electron irradiation unit 10c. The focal positions 13 of the first electron irradiation unit 10a, the second electron irradiation unit 10b, and the third electron irradiation unit 10c are distributed on the surface of the target 11.

[0055] Figure 3 A more detailed structural example of the electron irradiation section 10 and the target 11 is shown. Figure 3 This represents an example of a permeable target. In Figure 3 In this embodiment, the X-ray tube 1 includes an electron source unit 16, which has a plurality of cold cathode electron sources 15 arranged in a plane. The plurality of electron irradiation sections 10 each contain different groups of the plurality of cold cathode electron sources 15.

[0056] The electron source unit 16 is formed by arraying a plurality of cold cathode electron sources 15 on a substrate 17 using semiconductor manufacturing technology. The substrate 17 is a flat plate such as silicon or glass. A group consisting of a portion of the plurality of cold cathode electron sources 15 arranged in an array constitutes an electron irradiation section 10.

[0057] A group comprising one of a plurality of electron irradiation units 10 is composed of one or more cold cathode electron sources 15 that irradiate electrons 71 to the same focal position 13 of a target 11. An electron irradiation unit 10 includes one or more cold cathode electron sources 15. For example, an electron irradiation unit 10 includes 100 or more, or 1000 or more, cold cathode electron sources 15. In the case where an electron irradiation unit 10 includes a plurality of cold cathode electron sources 15, the collection of electrons 71 irradiated from each of the plurality of cold cathode electron sources 15 constituting the electron irradiation unit 10 forms the electrons 71 irradiated from the electron irradiation unit 10. The electrons 71 irradiate a focal position 13 on the target 11. Through the collision of the electrons 71, X-rays 70 are generated from the focal position 13 on the target 11. The point (spot) where the electrons 71 collide at the focal position 13 becomes the focal point of the X-rays 70. Imaging control unit 24 (see reference) Figure 1 The power supply 18 is controlled by applying a specified voltage between the cathode electrode (not shown) and the target 11.

[0058] (Control of the configuration of the first to ninth relative focus positions by the shooting control unit)

[0059] The imaging control unit 24 is configured to simultaneously irradiate electrons 71 onto different focal positions 13 of the target 11 by the first electron irradiation unit 10a, the second electron irradiation unit 10b, and the third electron irradiation unit 10c. As a result, the first detection signal to the third detection signal is detected in the detector 2, and the image processing unit 23 generates projection image data 81 based on each of the first detection signal to the third detection signal.

[0060] Reference Figure 4 and Figure 5 The positional relationship between the first relative focus position and the ninth relative focus position (7a to 7i) is explained. Figure 4 (a) is a schematic diagram showing, from a vertical perspective, the first focal point position 13a (first focal point), the second focal point position 13b (second focal point), and the third focal point position 13c (third focal point), the subject 90, and the detector 2 in an example of this embodiment. Figure 4 (b) is a schematic diagram showing the positional relationship between the first relative focal position to the ninth relative focal position (7a to 7i) in an example of this embodiment. Figure 4 (c) is Figure 4 An enlarged view of part A in (b). Additionally, Figure 5(a) is a schematic diagram showing the first focal point position 13a (first focal point), the second focal point position 13b (second focal point), and the third focal point position 13c (third focal point) of the first comparative example when viewed from the vertical direction, the subject 90, and the detector 2. Figure 5 (b) is a schematic diagram showing the positional relationship between the first relative focal position to the ninth relative focal position (79a-79i) of the first comparative example. Figure 5 (c) is Figure 5 Enlarged view of part B in (b).

[0061] As in the first comparative example Figure 5 As shown in (c), the second relative focus position 79b under the first shooting angle 6a overlaps with the fourth relative focus position 79d under the second shooting angle 6b. Furthermore, the third relative focus position 79c under the first shooting angle 6a, the fifth relative focus position 79e under the second shooting angle 6b, and the seventh relative focus position 79g under the third shooting angle 6c overlap. Additionally, the sixth relative focus position 79f under the second shooting angle 6b overlaps with the eighth relative focus position 79h under the third shooting angle 6c.

[0062] That is, in the first comparative example, the shooting angle 6a of the projected image data 81 based on the first detection signal from the first electronic irradiation unit 10a, the shooting angle 6b of the projected image data 81 based on the second detection signal from the second electronic irradiation unit 10b, and the shooting angle 6b of the projected image data 81 based on the third detection signal from the third electronic irradiation unit 10c, and the shooting angle 6b of the projected image data 81 based on the first detection signal from the first electronic irradiation unit 10a, and the shooting angle 6b of the projected image data 81 based on the third detection signal from the third electronic irradiation unit 10c, are as follows: The projection image data 81 of the signal, including the shooting angle 6, the shooting angle 6 of the projection image data 81 based on the third detection signal from the third electron irradiation unit 10c, the shooting angle 6 of the projection image data 81 based on the first detection signal from the first electron irradiation unit 10a under the third shooting angle 6c, the shooting angle 6 of the projection image data 81 based on the second detection signal from the second electron irradiation unit 10b, and the shooting angle 6 of the projection image data 81 based on the third detection signal from the third electron irradiation unit 10c, all contain projection image data 81 with the same shooting angle 6. In this case, it can be said that these projection image data 81 with the same shooting angle 6 are substantially the same, so it is impossible to increase the number of shooting angles 6 in the projection image data 81.

[0063] In contrast, in the X-ray imaging apparatus 100 of this embodiment, such as Figure 4As shown in example (c), the first to ninth relative focus positions (7a to 7i) are all arranged in different positions without overlapping. Therefore, the number of shooting angles 6 in the projected image data 81 can be increased. The shooting control unit 24 controls the relative focus positions 7 at the first shooting angle 6a, the second relative focus position 7b and the third relative focus position 7c, the fourth relative focus position 7d, the fifth relative focus position 7e and the sixth relative focus position 7f at the second shooting angle 6b, and the seventh relative focus position 7g, the eighth relative focus position 7h and the ninth relative focus position 7i at the third shooting angle 6c in a manner that does not overlap with each other.

[0064] Specifically, the shooting control unit 24 is configured to control the interfocal distance p (refer to the reference) between the first focal point (first focal point position 13a) of the first electron irradiation unit 10a and the second focal point (second focal point position 13b) of the second electron irradiation unit 10b. Figure 3 The distance d between the focal point (first focal point position 13a) and the subject 90 (refer to the distance between the focal point and the subject). Figure 2 The number of shooting angles 6 (number of fields of view) V, the rotation angle range θ of the rotating mechanism 4, the number of focal points N in the target 11, and the number m of relative focal points 7 including the second relative focal point 7b that exist from the first relative focal point position 7a to the second relative focal point position 7b are adjusted so that the first relative focal point position to the ninth relative focal point position (7a to 7i) are different in a way that they do not overlap with each other.

[0065] Here, the focal distance p between the first focal point (first focal point position 13a) of the first electron irradiation unit 10a and the second focal point (second focal point position 13b) of the second electron irradiation unit 10b, and the focal distance p between the second focal point (second focal point position 13b) of the second electron irradiation unit 10b and the third focal point (third focal point position 13c) of the third electron irradiation unit 10c are arranged in a substantially equal manner. Therefore, the focal distance p can also be the focal distance p between the second focal point (second focal point position 13b) of the second electron irradiation unit 10b and the third focal point (third focal point position 13c) of the third electron irradiation unit 10c.

[0066] Furthermore, the focal-to-subject distance d between the first focal point (first focal point position 13a) and the subject 90, the focal-to-subject distance d between the second focal point (second focal point position 13b) and the subject 90, and the focal-to-subject distance d between the third focal point (third focal point position 13c) and the subject 90 are all configured to be approximately equal. Therefore, the focal-to-subject distance d can be the focal-to-subject distance d between the second focal point (second focal point position 13b) or the third focal point (third focal point position 13c) and the subject 90. Additionally, the number m of relative focal points 7 can also be the number m of relative focal points 7 existing from the second relative focal point 7b to the third relative focal point 7c, including the third relative focal point 7c.

[0067] More specifically, the shooting control unit 24 is configured such that the first relative focus position to the ninth relative focus position (7a to 7i) are different in a way that they do not overlap, based on the following formula (1).

[0068]

[0069] Here, p is the distance between focal points, d is the distance between subjects at focal points, V is the number of shooting angles 6, θ is the rotation angle range of the rotating mechanism 4, N is the number of focal points in the target 11, and m is the number of relative focal positions 7, including the second relative focal position 7b, that exist between the first relative focal position 7a and the second relative focal position 7b. m and N are numbers such that the remainder when m is divided by N is not zero.

[0070] Furthermore, in this embodiment, the number N of focal points in the target 11 is 3, and this number is stored as a fixed value in the storage unit 25. Additionally, before starting to photograph the subject 90 using the imaging unit 5, the user can use the input device 28 to set the magnification, rotation angle range θ, and number of shooting angles 6 (field of view) V of the subject 90 in the projected image data 81. The imaging control unit 24 acquires the information stored in the storage unit 25 regarding the fixed value of the number N of focal points in the target 11, and the information input by the user via the input device 28 regarding the magnification, rotation angle range θ, and number of shooting angles 6 V of the subject 90 in the projected image data 81.

[0071] Here, the interfocal distance p corresponds to the distance between adjacent electron irradiation units 10 among the plurality of electron irradiation units 10. The imaging control unit 24 obtains the information of the interfocal distance p based on the distance between the first electron irradiation unit 10a and the second electron irradiation unit 10b.

[0072] Furthermore, the focal distance d between subjects corresponds to the magnification of the subject 90 in the projected image data 81, which can be set by the user. The shooting control unit 24 receives information about the magnification of the subject 90 in the projected image data 81 through input from the user via the input device 28, and thereby obtains information about the focal distance d between subjects based on the magnification information of the subject 90 in the projected image data 81. There is no particular limitation on the method for obtaining information about the focal distance d between subjects based on the magnification information of the subject 90 in the projected image data 81, and various methods can be used to obtain it appropriately.

[0073] The shooting control unit 24 acquires parameters other than those obtained from the information based on a fixed value of the number of focus points N, information acquired according to user input, and the aforementioned equation (1). For example, the shooting control unit 24 acquires the value of the inter-focus distance p that satisfies the aforementioned equation (1), and the value of the number m of relative focus positions 7, including the second relative focus position 7b, existing from the first relative focus position 7a to the second relative focus position 7b.

[0074] The shooting control unit 24 adjusts the inter-focus distance p and the number of relative focus positions 7 m, which are obtained by calculation through the above formula (1) and the number of relative focus positions 7 including the second relative focus position 7b, from the first relative focus position 7a to the second relative focus position 7b.

[0075] Specifically, the shooting control unit 24 moves the first electronic irradiation unit 10a, the second electronic irradiation unit 10b, and the third electronic irradiation unit 10c via the electronic irradiation unit moving mechanism 14, so that the inter-focal distance p between the first focal point (first focal point position 13a) of the first electronic irradiation unit 10a and the second focal point (second focal point position 13b) of the second electronic irradiation unit 10b, and the inter-focal distance p between the second focal point (second focal point position 13b) of the second electronic irradiation unit 10b and the third focal point (third focal point position 13c) of the third electronic irradiation unit 10c become the acquired inter-focal distance p value, and the number m of relative focal points 7, including the second relative focal point position 7b, existing from the first relative focal point position 7a to the second relative focal point position 7b, becomes the acquired number m of relative focal points 7.

[0076] After the first electronic irradiation unit 10a, the second electronic irradiation unit 10b, and the third electronic irradiation unit 10c are moved by the shooting control unit 24 via the electronic irradiation unit moving mechanism 14, the main control unit 22 starts shooting by the shooting unit 5 based on the input operation of the user to start shooting via the input device 28.

[0077] (Number of relative focal points)

[0078] Reference Figure 6 (a)~ Figure 6 (d) describes the number m of relative focal positions 7, including the second relative focal position 7b, existing from the first relative focal position 7a to the second relative focal position 7b. Furthermore, regarding the number m of relative focal positions 7, the number m of relative focal positions 7, including the second relative focal position 7b, existing from the first relative focal position 7a to the second relative focal position 7b is the same as the number m of relative focal positions 7, including the third relative focal position 7c, existing from the second relative focal position 7b to the third relative focal position 7c.

[0079] In one example of the control of the configuration of the first relative focus position to the ninth relative focus position (7a to 7i) by the shooting control unit 24, the shooting control unit 24 obtains the value of the inter-focus distance p and the value of the number m of the relative focus positions 7, including the second relative focus position 7b, that exist from the first relative focus position 7a to the second relative focus position 7b. Figure 6 (a)~ Figure 6 Figure (d) is a diagram showing an example of the positional relationships among the values ​​of the number m of relative focal positions 7 and the value of the distance p between focal points obtained by equation (1), namely, the first relative focal positions to the sixth relative focal positions (7a to 7f), the seventh relative focal position 7g of the first electron irradiation unit 10a relative to the subject 90 at the third shooting angle 6c, the eighth relative focal position 7h of the second electron irradiation unit 10b relative to the subject 90 at the third shooting angle 6c, and the ninth relative focal position 7i of the third electron irradiation unit 10c relative to the subject 90 at the third shooting angle 6c. Furthermore, in this example of the positional relationship of the relative focal positions 7, the distance d between the focal points and the subject is 75 mm, the number V of the shooting angles 6 is 100, the rotation angle range θ is 180 degrees, and the number N of focal points in the target 11 is 3.

[0080] Figure 6 (a) represents an example of the positional relationship between the first relative focal position to the ninth relative focal position (7a to 7i) when the number of relative focal positions 7 m is 1 and the distance between focal points p is 0.78 mm, obtained by formula (1). Figure 6As shown in (a), the number m of relative focus positions 7, including the fifth relative focus position 7e, existing from the fourth relative focus position 7d to the fifth relative focus position 7e under the second shooting angle 6b is 1. In this case, the first relative focus positions to the third relative focus positions (7a to 7c) under the first shooting angle 6a, the fourth relative focus positions to the sixth relative focus positions (7d to 7f) under the second shooting angle 6b, and the seventh relative focus positions to the ninth relative focus positions (7g to 7i) under the third shooting angle 6c are all different and do not overlap with each other.

[0081] Figure 6 (b) represents an example of the positional relationship between the first relative focal position to the ninth relative focal position (7a to 7i) when the number of relative focal positions 7 m is 2 and the distance between focal points p is 1.57 mm, obtained by formula (1). Figure 6 As shown in (b), the number m of relative focus positions 7, including the fifth relative focus position 7e, existing from the fourth relative focus position 7d to the fifth relative focus position 7e under the second shooting angle 6b is 2. In this case, the first relative focus positions to the third relative focus positions (7a to 7c) under the first shooting angle 6a, the fourth relative focus positions to the sixth relative focus positions (7d to 7f) under the second shooting angle 6b, and the seventh relative focus positions to the ninth relative focus positions (7g to 7i) under the third shooting angle 6c are all different and do not overlap with each other.

[0082] Figure 6 (c) represents an example of the positional relationship between the first relative focal position to the ninth relative focal position (7a to 7i) when the number of relative focal positions 7 m is 4 and the distance between focal points p is 3.14 mm, obtained by formula (1). Figure 6 As shown in (c), the number m of relative focus positions 7, including the fifth relative focus position 7e, existing from the fourth relative focus position 7d to the fifth relative focus position 7e under the second shooting angle 6b is 4. In this case, the first relative focus positions to the third relative focus positions (7a to 7c) under the first shooting angle 6a, the fourth relative focus positions to the sixth relative focus positions (7d to 7f) under the second shooting angle 6b, and the seventh relative focus positions to the ninth relative focus positions (7g to 7i) under the third shooting angle 6c are all different and do not overlap with each other.

[0083] Figure 6 (d) represents an example of the positional relationship between the first relative focal position to the ninth relative focal position (7a to 7i) when the number of relative focal positions 7 m is 5 and the distance between focal points p is 3.92 mm, obtained by formula (1). Figure 6As shown in (d), the number m of relative focus positions 7, including the fifth relative focus position 7e, existing from the fourth relative focus position 7d to the fifth relative focus position 7e under the second shooting angle 6b is 5. In this case, the first relative focus positions to the third relative focus positions (7a to 7c) under the first shooting angle 6a, the fourth relative focus positions to the sixth relative focus positions (7d to 7f) under the second shooting angle 6b, and the seventh relative focus positions to the ninth relative focus positions (7g to 7i) under the third shooting angle 6c are all different and do not overlap with each other.

[0084] exist Figure 6 (a)~ Figure 6 In the example shown in (d), which obtains the value of the interfocal distance p based on the above formula (1) and the value of the number m of relative focal positions 7, including the second relative focal position 7b, existing from the first relative focal position 7a to the second relative focal position 7b, the projected image data 81 based on the first detection signal from the first electron irradiation unit 10a, the projected image data 81 based on the second detection signal from the second electron irradiation unit 10b, and the projected image data 81 based on the third detection signal from the third electron irradiation unit 10c at the first shooting angle 6a to the third shooting angle 6c do not include the projected image data 81 with the same shooting angle 6.

[0085] Furthermore, in equation (1), the remainder of the number of relative focal positions 7 m divided by the number of focal points N in the target 11 (3 in this example) is not 0. In contrast, as... Figure 7 As shown in the second comparative example, when the number of relative focal positions 79, m, is 3, the remainder obtained by dividing the number of relative focal positions 79, m(3), by the number of focal points N(3) in the target 11 is 0. In this case, the second relative focal position 79b under the first shooting angle 6a overlaps with the fourth relative focal position 79d under the second shooting angle 6b. In addition, the third relative focal position 79c under the first shooting angle 6a, the fifth relative focal position 79e under the second shooting angle 6b, and the seventh relative focal position 79g under the third shooting angle 6c overlap. In addition, the sixth relative focal position 79f under the second shooting angle 6b overlaps with the eighth relative focal position 79h under the third shooting angle 6c. That is, the projected image data 81 based on the third detection signal from the third electronic irradiation unit 10c at the first shooting angle 6a, the projected image data 81 based on the second detection signal from the second electronic irradiation unit 10b at the second shooting angle 6b, and the projected image data 81 based on the first detection signal from the first electronic irradiation unit 10a at the third shooting angle 6c are all projected image data 81 based on the same shooting angle 6.

[0086] (Refactoring process)

[0087] For the image processing unit 23 (see Figure 1 The reconstruction process using multiple projected image data 81 is briefly explained.

[0088] The data used in the reconstruction process is explained. In control device 20 (refer to...) Figure 1 The storage unit 25 stores the program 80 executed by the image processing unit 23 and multiple projection image data 81. For each of the multiple projection image data 81, information about the shooting angle 6 at the time of acquiring the projection image data 81, information about the electron irradiation unit 10 (identifying which of the first, second, and third electron irradiation units 10a, 10b, and 10c it is), and information about the relative focal position 7 are stored in association. Additionally, the storage unit 25 stores the generated CT image 82.

[0089] Here, detector 2 simultaneously detects X-rays 70 emitted from the first focal point corresponding to the first electron irradiation unit 10a and passing through the subject 90, X-rays 70 emitted from the second focal point corresponding to the second electron irradiation unit 10b and passing through the subject 90, and X-rays 70 emitted from the third focal point corresponding to the third electron irradiation unit 10c and passing through the subject 90 at each of the multiple shooting angles 6. That is, the detection signal (image signal) acquired by detector 2 is the detection signal (image signal) of the X-rays 70 emitted from each of the first focal point, the second focal point, and the third focal point after overlap, so conventional analytical CT reconstruction methods such as filtered back projection cannot be applied.

[0090] Therefore, in this embodiment, a reconstruction process using a successive approximation method is performed. The image processing unit 23 uses the successive approximation method to repeatedly calculate the contribution rate from each of the first focal point, the second focal point, and the third focal point. As a result, the image processing unit 23 can acquire the detection signals (image signals) of the X-rays 70 emitted from the first focal point, the X-rays 70 emitted from the second focal point, and the X-rays 70 emitted from the third focal point, based on the overlapping detection signals (image signals) of the X-rays 70 emitted from each of the first focal point, the second focal point, and the third focal point. Therefore, a high-quality reconstructed image can be generated. Furthermore, the method of obtaining the detection signal (image signal) of each focal point based on the overlapping detection signals (image signals) of X-rays 70 emitted from each of the multiple focal points using a successive approximation method is, for example, a known method disclosed in “Daniel F. Yu, Jeffrey A. Fessler, Edward P. Figaro, Maximum-Likelihood Transmission Image Reconstruction for Overlapping Transmission Beams”, IEEE Transactions on Medical Imaging 19.11 (2000): p.1094-1105, therefore, detailed descriptions are omitted here.

[0091] The result of the reconstruction process using the successive approximation method is that the image processing unit 23 generates a CT image 82 of the subject 90.

[0092] (X-ray image acquisition, processing, and reconstruction)

[0093] Reference Figure 8 The X-ray image acquisition and reconstruction processes performed by the control unit 21 are explained. Furthermore, the order of the processing steps can be reversed or performed simultaneously, provided they do not contradict each other.

[0094] In step S1, the shooting control unit 24 acquires at least one of the following information from the storage unit 25 or by receiving input from the user via the input device 28: information on the distance p between focal points, information on the distance d between focal points, information on the number V of shooting angles 6, information on the rotation angle range θ, information on the number N of focal points in the target 11, and information on the number m of relative focal positions 7. Then, the process proceeds to step S2.

[0095] In step S2, the shooting control unit 24 acquires parameters other than those satisfying equation (1) based on the acquired information and equation (1). Then, the process proceeds to step S3.

[0096] In step S3, the imaging control unit 24 adjusts parameters other than those obtained through the calculation of equation (1). Then, the process proceeds to step S4.

[0097] In step S4, the main control unit 22 receives an operation input from the user via the input device 28 and sends a signal to the imaging control unit 24 instructing it to begin the imaging operation. The imaging control unit 24, upon receiving the signal from the main control unit 22, controls the X-ray tube 1 and the rotation mechanism 4 to begin imaging the subject 90. Then, the imaging control unit 24 captures projected image data 81 within a predetermined angle range. Afterward, the process proceeds to step S5.

[0098] In step S5, the image processing unit 23 performs reconstruction processing based on each projected image data 81 contained in the projection dataset. Then, the processing proceeds to step S7.

[0099] In step S6, the image processing unit 23 stores the generated CT image 82 in the storage unit 25. Afterward, the processing ends.

[0100] (Comparison with the third and fourth comparative examples)

[0101] Reference Figure 9 (a)~ Figure 9 (c) will explain the comparison results between the tomographic images obtained by the X-ray imaging apparatus of the third and fourth comparative examples and the tomographic images obtained by the X-ray imaging apparatus 100 of this embodiment.

[0102] also, Figure 9 (a)~ Figure 9 The subject 90 shown in (c) is the same subject 90. Subject 90 is a cylindrical resin sample containing material or gaps with low X-ray absorption coefficient 70 within it. Additionally, Figure 9 (a)~ Figure 9 The upper image of (c) is a tomographic image along the horizontal direction of the cylindrical subject 90. Additionally, Figure 9 (a)~ Figure 9 The lower image of (c) is a difference image between the tomographic image of the upper image and the image of the cross-section obtained by cutting the cylindrical subject 90° at the location corresponding to the tomographic image. That is, Figure 9 (a)~ Figure 9The image below (c) is an image in which artifact 93 was extracted from the tomographic image above.

[0103] Figure 9 (a) is a tomographic image acquired by the X-ray imaging apparatus of the third comparative example. The X-ray imaging apparatus of the third comparative example includes a monofocal X-ray tube consisting of a target and a single electron irradiation unit. Figure 9 In the upper and lower images of (a), it can be confirmed that the radially extending striped artifacts 93 are caused by the small number of shooting angles (small number of fields of view).

[0104] in addition, Figure 9 (b) is a tomographic image acquired by the X-ray imaging apparatus of the fourth comparative example. The X-ray imaging apparatus of the fourth comparative example includes a trifocal X-ray tube consisting of a target and three electron irradiation units. However, the X-ray imaging apparatus of the fourth comparative example differs from the X-ray imaging apparatus 100 of this embodiment in that it does not perform the control that makes the first relative focal positions (7a-7c) at the first imaging angle 6a, the fourth relative focal positions (7d-7f) at the second imaging angle 6b, and the seventh relative focal positions (7g-7i) at the third imaging angle 6c mutually non-overlapping. That is, in the X-ray imaging apparatus of the fourth comparative example, the first relative focal positions (7a-7c) at the first imaging angle 6a, the fourth relative focal positions (7d-7f) at the second imaging angle 6b, and the seventh relative focal positions (7g-7i) at the third imaging angle 6c include overlapping relative focal positions. Therefore, in Figure 9 In the upper and lower images of (b), many radially extending striped artifacts 93 can be identified, caused by the small number of shooting angles (small number of fields of view).

[0105] In contrast, Figure 9 (c) is a tomographic image acquired by the X-ray imaging apparatus 100 of this embodiment. The imaging control unit 24 controls the images so that the first to third relative focal points (7a to 7c) at the first imaging angle 6a, the fourth to sixth relative focal points (7d to 7f) at the second imaging angle 6b, and the seventh to ninth relative focal points (7g to 7i) at the third imaging angle 6c are different from each other in a non-overlapping manner. Therefore, in Figure 9 In the upper and lower figures of (c), compared with the third comparative example Figure 9 (a) and the fourth comparative example Figure 9Compared to (b), it can be confirmed that there are generally no radially extending stripe-like artifacts 93 caused by the small number of shooting angles 6 (small number of fields of view). Therefore, in the X-ray imaging apparatus 100 of this embodiment, artifacts caused by the small number of shooting angles can be reduced.

[0106] in addition, Figure 10 (a) is the third comparative example. Figure 9 A magnified view of part C in the upper part of (a). Figure 10 (b) is the fourth comparative example. Figure 9 (b) is an enlarged view of part D in the upper part of the diagram. Figure 10 (c) is the embodiment of this method. Figure 9 A magnified view of part E in the upper part of (c). Additionally, Figure 10 (d) means Figure 10 (a)~ Figure 10 A graph showing the pixel values ​​of lines 91a to 91c in (c). If for Figure 10 (a)~ Figure 10 By comparing (c), it can be confirmed that: in this embodiment... Figure 10 In (c), the artifact 93 is greater than that of the third comparative example. Figure 10 (a) and the fourth comparative example Figure 10 (b) is less. Additionally, according to Figure 10 (a)~ Figure 10 (d) It can be confirmed that the contrast of the longitudinally photographed structure 92 is improved in the tomographic image acquired by the X-ray imaging apparatus 100 of this embodiment.

[0107] [Variation Example]

[0108] Furthermore, the embodiments and examples disclosed herein should be considered illustrative rather than restrictive in all respects. The scope of the invention is defined by the claims rather than by the description of the embodiments and examples, and includes all modifications (variations) within the meaning and scope equivalent to the claims.

[0109] For example, the X-ray tube may be configured in a way that the first relative focal point position of the first electron irradiation unit relative to the subject at the first shooting angle, the second relative focal point position of the second electron irradiation unit relative to the subject at the first shooting angle, the third relative focal point position of the first electron irradiation unit relative to the subject at the second shooting angle, and the fourth relative focal point position of the second electron irradiation unit relative to the subject at the second shooting angle are different from each other, and the focal distance p between the first focal point of the first electron irradiation unit and the second focal point of the second electron irradiation unit and the number of focal points N in the target are preset.

[0110] Alternatively, the shooting control unit may be configured to individually control electron illumination from multiple electron illumination units, and to select two or more electron illumination units from the multiple electron illumination units to simultaneously illuminate the electrons. In this case, the focal distance p can be appropriately changed according to the selected electron illumination units, so an electron illumination unit moving mechanism may not be required.

[0111] Alternatively, for example, the first to fourth relative focus positions can be configured on the outline of a polygon rather than on an arc centered on the rotation axis of the rotating mechanism, as long as they are configured at different positions that do not overlap with each other as the shooting angle changes.

[0112] Alternatively, for example, the first electron irradiation unit and the second electron irradiation unit may be arranged offset in the vertical direction on a rotating surface orthogonal to the rotation axis of the rotating mechanism.

[0113] Alternatively, for example, the shooting control unit may be configured to replace at least one of the following parameters: the distance between focal points p, the distance between focal subjects d, the number of shooting angles V, the rotation angle range θ of the rotating mechanism, the number of focal points N in the target, and the number of relative focal positions m, with other parameters or to add other parameters, and adjust at least one of these parameters, thereby making the first relative focal position to the ninth relative focal position different in a way that they do not overlap.

[0114] Additionally, X-ray imaging devices can also be used for medical purposes. In this case, the subject is a living organism being examined.

[0115] Alternatively, for example, multiple electron irradiation sections may also include a thermionic electron source.

[0116] [Example]

[0117] Those skilled in the art will understand that the exemplary embodiments described are specific examples of the following forms.

[0118] (Project 1)

[0119] An X-ray imaging device, comprising:

[0120] An X-ray tube includes at least a first electron irradiation section and a second electron irradiation section for irradiating electrons at different focal positions of a target;

[0121] A detector for detecting X-rays emitted from the X-ray tube;

[0122] A subject-carrying section is disposed between the X-ray tube and the detector, and carries the subject;

[0123] A rotating mechanism that rotates one of the imaging section containing the X-ray tube and the detector, and the subject mounting section, to change the imaging angle of the subject; and

[0124] The control unit acquires multiple projected image data from the detector at various shooting angles, and generates a CT image based on the acquired multiple projected image data.

[0125] The control unit performs the following controls:

[0126] Electrons are simultaneously irradiated from the first electron irradiation unit and the second electron irradiation unit at each of the plurality of said shooting angles; and

[0127] The first relative focal point position of the first electronic irradiation unit relative to the subject at the first shooting angle, the second relative focal point position of the second electronic irradiation unit relative to the subject at the first shooting angle, the third relative focal point position of the first electronic irradiation unit relative to the subject at the second shooting angle, and the fourth relative focal point position of the second electronic irradiation unit relative to the subject at the second shooting angle are different in a way that they do not overlap with each other.

[0128] By simultaneously irradiating electrons onto different focal positions of the target from multiple electron irradiation units, including a first electron irradiation unit and a second electron irradiation unit, at each of the multiple shooting angles, multiple projected image data corresponding to the number of electron irradiation units can be acquired at each shooting angle. Therefore, the number of acquired projected image data can be increased without increasing the shooting time. Furthermore, by making the first to fourth relative focal positions different in a non-overlapping manner, the shooting angles of the subject in the projected image data acquired at each shooting angle, corresponding to the number of electron irradiation units, are different from each other. Therefore, projected image data at different shooting angles can be acquired from each of the acquired multiple projected image data. Therefore, a sufficient number of shooting angles (number of fields of view) of projected image data can be acquired from the increased projected image data. For these reasons, the increase in shooting time spent acquiring projected image data can be suppressed, and artifacts caused by a small number of shooting angles can be reduced.

[0129] (Project 2)

[0130] According to the X-ray imaging apparatus of Project 1, the control unit is configured such that, as the imaging angle changes, the first relative focal point position, the second relative focal point position, the third relative focal point position, and the fourth relative focal point position are arranged at different, non-overlapping, circular arc positions centered on the rotation axis of the rotating mechanism.

[0131] In this case, the distance between each of the first to fourth relative focal positions and the subject can be kept constant as the shooting angle changes. Therefore, when generating CT images based on the projection image data obtained at each of the first to fourth relative focal positions, compared with the case where the distances between each of the first to fourth relative focal positions and the subject are different, CT images can be easily generated through reconstruction processing.

[0132] (Project 3)

[0133] According to the X-ray imaging apparatus of Project 1 or Project 2, the first electron irradiation unit and the second electron irradiation unit simultaneously irradiate electrons at each of the plurality of imaging angles based on the control of the control unit, and are arranged in a rotational plane orthogonal to the rotational axis of the rotational mechanism.

[0134] In this case, since the first electron irradiation unit and the second electron irradiation unit can be arranged on the same plane at each of the first to fourth relative focal positions that vary with the shooting angle, when generating CT images based on the projection image data acquired at each of the first to fourth relative focal positions, it is easier to generate CT images through reconstruction processing compared to the case where the first electron irradiation unit and the second electron irradiation unit are not arranged on the same plane at each of the first to fourth relative focal positions.

[0135] (Project 4)

[0136] According to any one of Items 1 to 3, in the X-ray imaging apparatus, the control unit adjusts at least one of the following: the inter-focal distance between the first focal point of the first electron irradiation unit and the second focal point of the second electron irradiation unit; the inter-focal distance between the first focal point or the second focal point and the subject; the number of imaging angles; the rotation angle range of the rotation mechanism; the number of focal points in the target; and the number of relative focal points, including the second relative focal point, existing from the first relative focal point to the second relative focal point, thereby making the first relative focal point, the second relative focal point, the third relative focal point, and the fourth relative focal point different in a non-overlapping manner.

[0137] In this case, the control unit can easily make the first to fourth relative focus positions different in a non-overlapping manner by adjusting at least one of the following: the distance between focus points, the distance between focus subjects, the number of shooting angles, the rotation angle range, the number of focus points, and the number of relative focus positions. Therefore, a sufficient number of shooting angles (fields of view) of projection image data can be acquired from the increased projection image data, thus suppressing the increase in shooting time spent acquiring projection image data. Furthermore, since the number of shooting angles is small, artifacts caused by the small amount of projection image data acquired can be easily reduced.

[0138] (Project 5)

[0139] According to the X-ray imaging apparatus of Project 4, the control unit is configured such that the first relative focal position, the second relative focal position, the third relative focal position and the fourth relative focal position are different in a manner that does not overlap with each other, based on the following formula (1).

[0140]

[0141] Here, p is the distance between focal points, d is the distance between the subjects at the focal points, V is the number of shooting angles, θ is the rotation angle range of the rotating mechanism, N is the number of focal points in the target, and m is the number of relative focal points, including the second relative focal point, that exist between the first relative focal point position and the second relative focal point position.

[0142] In this case, the control unit can more easily differentiate the first relative focus position to the fourth relative focus position in a non-overlapping manner based on the aforementioned equation (1). Therefore, the increase in the shooting time spent acquiring projected image data can be suppressed, and since the number of shooting angles is small, artifacts caused by the small number of projected image data acquisitions can be reduced more easily.

[0143] (Project 6)

[0144] The X-ray imaging apparatus according to any one of Projects 1 to 5, wherein the X-ray tube includes the target, and at least a first electron irradiation unit and a second electron irradiation unit for respectively irradiating electrons to different focal positions on the target.

[0145] The detector is configured to simultaneously detect X-rays based on electrons irradiated by the first electron irradiation unit and X-rays based on electrons irradiated by the second electron irradiation unit.

[0146] In this case, the X-ray tube includes a target and at least a first electron irradiation section and a second electron irradiation section that simultaneously irradiate electrons to different focal positions on the target. The detector can simultaneously detect X-rays based on the first electron irradiation section and X-rays based on the second electron irradiation section. Therefore, compared with the case of having an X-ray tube including a target and a first electron irradiation section, or multiple X-ray tubes including an X-ray tube including a target and a second electron irradiation section, the increase in the number of parts and the complexity of the structure can be suppressed.

[0147] (Project 7)

[0148] An X-ray tube is used in an X-ray imaging device that acquires multiple projection image data at multiple imaging angles and generates CT images based on the acquired multiple projection image data.

[0149] The X-ray tube includes at least a first electron irradiation section and a second electron irradiation section that simultaneously irradiate electrons at different focal positions of the target, and

[0150] The distance between the first focal point of the first electronic irradiation unit and the second focal point of the second electronic irradiation unit relative to the subject at the first shooting angle, the third focal point of the first electronic irradiation unit relative to the subject at the second shooting angle, and the fourth focal point of the second electronic irradiation unit relative to the subject at the second shooting angle are preset in a way that they do not overlap.

[0151] By simultaneously irradiating electrons onto different focal positions of the target from multiple electron irradiation units, including a first electron irradiation unit and a second electron irradiation unit, at each of the multiple shooting angles, multiple projected image data corresponding to the number of electron irradiation units can be acquired at each shooting angle. Therefore, the number of acquired projected image data can be increased without increasing the shooting time. Furthermore, since the focal distance between the first focal point of the first electron irradiation unit and the second focal point of the second electron irradiation unit, and the number of focal points in the target are preset in a manner where the first to fourth relative focal points do not overlap, projected image data at different shooting angles can be acquired from each of the acquired multiple projected image data. Therefore, a sufficient number of shooting angles (number of fields of view) of projected image data can be acquired from the increased projected image data. For these reasons, the increase in shooting time spent acquiring projected image data can be suppressed, and artifacts caused by a small number of shooting angles can be reduced.

Claims

1. An X-ray imaging device, comprising: An X-ray tube includes at least a first electron irradiation section and a second electron irradiation section for irradiating electrons at different focal positions of a target; A detector for detecting X-rays emitted from the X-ray tube; A subject-carrying section is disposed between the X-ray tube and the detector, and carries the subject; A rotating mechanism that rotates one of the imaging section containing the X-ray tube and the detector and the subject mounting section, so as to change the imaging angle of the subject; as well as The control unit acquires multiple projected image data from the detector at various shooting angles, and generates a computed tomography (CT) image based on the acquired multiple projected image data. The control unit performs the following controls: Electrons are simultaneously irradiated from the first electron irradiation unit and the second electron irradiation unit at each of the plurality of said shooting angles; and The first relative focal point position of the first electronic irradiation unit relative to the subject at the first shooting angle, the second relative focal point position of the second electronic irradiation unit relative to the subject at the first shooting angle, the third relative focal point position of the first electronic irradiation unit relative to the subject at the second shooting angle, and the fourth relative focal point position of the second electronic irradiation unit relative to the subject at the second shooting angle are different in a manner that does not overlap with each other.

2. The X-ray imaging apparatus according to claim 1, wherein, The control unit is configured such that, as the shooting angle changes, the first relative focus position, the second relative focus position, the third relative focus position, and the fourth relative focus position are arranged at different positions on an arc with the rotation axis of the rotating mechanism as the center, and they do not overlap with each other.

3. The X-ray imaging apparatus according to claim 1, wherein, The first electron irradiation unit and the second electron irradiation unit simultaneously irradiate electrons according to each of the plurality of shooting angles, based on the control of the control unit, and are arranged side by side in a rotation plane orthogonal to the rotation axis of the rotation mechanism.

4. The X-ray imaging apparatus according to claim 1, wherein, The control unit adjusts at least one of the following: the focal distance between the first focal point of the first electronic irradiation unit and the second focal point of the second electronic irradiation unit; the focal distance between the first focal point or the second focal point and the subject; the number of shooting angles; the rotation angle range of the rotating mechanism; the number of focal points in the target; and the number of relative focal points, including the second relative focal point, existing from the first relative focal point to the second relative focal point. This makes the first relative focal point, the second relative focal point, the third relative focal point, and the fourth relative focal point different in a non-overlapping manner.

5. The X-ray imaging apparatus according to claim 4, wherein, The control unit is configured such that the first relative focal position, the second relative focal position, the third relative focal position, and the fourth relative focal position are different in a manner that does not overlap with each other, based on the following formula (1). Here, p is the distance between focal points, d is the distance between the subjects at the focal points, V is the number of shooting angles, θ is the rotation angle range of the rotating mechanism, N is the number of focal points in the target, and m is the number of relative focal points, including the second relative focal point, that exist between the first relative focal point position and the second relative focal point position.

6. The X-ray imaging apparatus according to claim 1, wherein, The X-ray tube includes the target, and at least a first electron irradiation section and a second electron irradiation section that respectively irradiate electrons to different focal positions on the target. The detector is configured to simultaneously detect X-rays based on electrons irradiated by the first electron irradiation unit and X-rays based on electrons irradiated by the second electron irradiation unit.

7. An X-ray tube used in an X-ray imaging apparatus, the X-ray imaging apparatus acquiring multiple projection image data at multiple imaging angles, and generating a computed tomography (CT) image based on the acquired multiple projection image data. The X-ray tube includes at least a first electron irradiation section and a second electron irradiation section that simultaneously irradiate electrons at different focal positions of the target, and The distance between the first focal point of the first electronic irradiation unit and the second focal point of the second electronic irradiation unit relative to the subject at the first shooting angle, the third focal point of the first electronic irradiation unit relative to the subject at the second shooting angle, and the fourth focal point of the second electronic irradiation unit relative to the subject at the second shooting angle are preset in a way that they do not overlap.

Images