X-ray computed tomography apparatus

Abstract

To generate a CT image easy for a user to confirm.SOLUTION: An X-ray computed tomography apparatus includes a gantry body, a correction unit, and a reconstruction unit. The gantry body rotatably supports an X-ray tube, an X-ray detector, and a data acquisition unit around a central axis of a bore. The X-ray tube generates X-rays, the X-ray detector detects the X-rays generated from the X-ray tube and passing through a subject, and the data acquisition circuit acquires projection data via the X-ray detector. The correction unit corrects the detection angle information of the projection data according to a correction amount based on a first reference angle in a rotation direction of the X-ray tube and a subject angle that defines a direction of the subject in the bore. The reconstruction unit reconstructs a CT image related to the subject based on the projection data and the corrected detection angle information.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments disclosed in this specification and the drawings relate to an X-ray computed tomography apparatus. [Background technology]

[0002] X-ray computed tomography equipment reconstructs CT images based on projection data collected in conjunction with information about the rotational angle of the X-ray tube. Essentially, the CT image is reconstructed so that the 0° rotational frame position in the gantry is at the top of the image.

[0003] In addition, some X-ray computed tomography systems are capable of both standing and sitting position imaging, allowing imaging in any orientation relative to the gantry. Even in standing and sitting position imaging, reconstruction is performed based on angle information, so the orientation of the subject at the time of imaging may not match the orientation of the subject on the image. In this case, if image processing is performed to rotate the reconstructed image to match the orientation of the subject on the image to the orientation of the subject at the time of imaging, the image may become blurred or the time required for image processing may be extended depending on the angle of rotation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-202321 Summary of the Invention [Problem to be solved by the invention]

[0005] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to generate CT images that are easy for users to check. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be positioned as other problems. [Means for solving the problem]

[0006] An X-ray computed tomography apparatus according to an embodiment includes a gantry body, a correction unit, and a reconstruction unit. The gantry body supports an X-ray tube, an X-ray detector, and a data acquisition unit rotatably around the central axis of a bore. The X-ray tube generates X-rays, the X-ray detector detects the X-rays generated from the X-ray tube and passing through a subject, and the data acquisition circuit collects projection data via the X-ray detector. The correction unit corrects detection angle information of the projection data according to a correction amount based on a first reference angle in the rotation direction of the X-ray tube and a subject angle that determines the orientation of the subject in the bore. The reconstruction unit reconstructs a CT image of the subject based on the projection data and the corrected detection angle information. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of the arrangement of an X-ray computed tomography apparatus according to the first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of an imaging posture of the X-ray computed tomography apparatus according to the first embodiment. [Figure 3] FIG. 3 is another view illustrating an example of the imaging posture of the X-ray computed tomography apparatus according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing the positional relationship between the gantry body and the subject, and the relationship with the reconstructed image. [Figure 5] FIG. 5 is a diagram schematically showing the flow of a CT examination according to the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating the determination of the object angle. [Figure 7] FIG. 7 is a diagram illustrating an example of calculation of the correction amount. [Figure 8] FIG. 8 is a diagram illustrating an example of correction of detected angle information. [Figure 9] FIG. 9 is a diagram illustrating CT images reconstructed from uncorrected projection data and corrected projection data. [Figure 10] FIG. 10 is a diagram illustrating the orientation of a subject in CT imaging in a supine position and an upright position. [Figure 11] FIG. 11 is a diagram showing a display screen. [Figure 12] FIG. 12 is a diagram showing an example of the arrangement of an X-ray computed tomography apparatus according to the second embodiment. [Figure 13] FIG. 13 is a diagram schematically showing the flow of a CT examination according to the second embodiment. [Figure 14] FIG. 14 is a diagram illustrating an example of correction amounts stored in association with projection data. [Figure 15] FIG. 15 is a diagram showing an example of the arrangement of an X-ray computed tomography apparatus according to the third embodiment. [Figure 16] FIG. 16 is a diagram showing the orientation of the subject and the exposure start position in supine position imaging. [Figure 17] FIG. 17 is a diagram showing the orientation of the subject and the position of the X-ray tube in standing position imaging. DETAILED DESCRIPTION OF THE INVENTION

[0008] (First embodiment) Hereinafter, an embodiment of an X-ray computed tomography apparatus will be described in detail with reference to the drawings.

[0009] 1 is a diagram showing the configuration of an X-ray computed tomography apparatus 1 according to the first embodiment. The X-ray computed tomography apparatus 1 irradiates a subject with X-rays from an X-ray tube 17 and detects the irradiated X-rays with an X-ray detector 19. The X-ray computed tomography apparatus 1 generates a CT image of the subject based on the output from the X-ray detector 19.

[0010] As shown in FIG. 1, the X-ray computed tomography apparatus 1 includes a gantry 10 and a console 40. For example, the gantry 10 is installed in a CT examination room, and the console 40 is installed in a control room adjacent to the CT examination room. The gantry 10 and the console 40 are connected to each other by wire or wirelessly so that they can communicate with each other. The gantry 10 is equipped with a mechanism for performing X-ray computed tomography (hereinafter referred to as X-ray CT imaging) on ​​a subject in a supine or standing position. The console 40 is a computer that controls the gantry 10. The X-ray computed tomography apparatus 1 can also be used in a sitting position instead of a standing position.

[0011] Although not shown in FIG. 1, the X-ray computed tomography apparatus 1 further includes a bed device on which the subject is placed. The bed device may be included in the configuration of the X-ray computed tomography apparatus 1, or may be configured externally to the X-ray computed tomography apparatus 1. The X-ray computed tomography apparatus 1 may also include a support device that supports the subject during upright imaging. The support device corresponds to the top plate of the bed device in supine CT. The support device may be fixed to the floor surface or may be movable while supporting the subject. The support device may also serve as the bed device. The X-ray computed tomography apparatus 1 does not necessarily need to include a support device for upright imaging.

[0012] The direction perpendicular to the floor surface is referred to as the Y-axis direction, the direction of the rotation axis of the gantry body 11 during imaging in the supine position that is horizontally orthogonal to the Y-axis direction and is referred to as the Z-axis direction, and the direction horizontally orthogonal to the Y-axis direction and the Z-axis direction is referred to as the X-axis direction. The -Y-axis direction is referred to as downward, the +Y-axis direction as upward, the -X-axis direction as backward, and the +X-axis direction as forward. The Y-axis is parallel to the central axis A1 of the gantry body 11 during imaging in the upright position. For example, when imaging in the upright position, the subject approaches below the gantry body 11 from the rear.

[0013] As shown in Fig. 1, the gantry 10 has a gantry main body 11 and a support 13. The gantry main body 11 performs X-ray CT imaging. The gantry main body 11 is a substantially cylindrical structure with an opening (bore) 15. The gantry main body 11 houses an X-ray tube 17, an X-ray detector 19, a high-voltage generator 31, and a data acquisition system (DAS) 33, which are arranged to face each other across the bore 15.

[0014] More specifically, the gantry main body 11 further includes a main frame (not shown) made of a metal such as aluminum, and a rotating frame 21 rotatably supported by the main frame around a central axis A1 via bearings or the like. An annular electrode (not shown) is provided at the contact point of the main frame with the rotating frame 21. A conductive slider (not shown) is attached to the contact point of the main frame so as to make sliding contact with the annular electrode. The rotating frame 21 is a metal frame made of a metal such as aluminum and formed into an annular shape, and has, for example, an X-ray tube 17 and an X-ray detector 19 attached thereto.

[0015] The rotating frame 21 receives power from a rotation drive device (not shown) and rotates at a constant angular velocity around the central axis A1 of the bore 15. The rotation drive device generates power for rotating the rotating frame 21 under the control of the gantry control device 23. The rotation drive device is realized by a motor such as a direct drive motor or a servo motor, for example.

[0016] The support pillar 13 is a base that supports the gantry main body 11 at a distance from the floor surface. The support pillar 13 has a columnar shape such as a cylindrical or rectangular pillar shape. The support pillar 13 is attached to, for example, the side surface of the gantry main body 11. The support pillar 13 supports the gantry main body 11 so that the gantry main body 11 can slide vertically relative to the floor surface in a position where the central axis A1 of the bore 15 is maintained perpendicular to the floor surface in order to perform X-ray CT imaging of a subject in a standing or sitting position.

[0017] Typically, the support pillar 13 is provided on one side of the gantry body 11. However, this embodiment is not limited to this. For example, two support pillars 13 may be connected to both sides of the gantry body 11. That is, at least one support pillar 13 supports the gantry body 11 so that it can move in the vertical direction. Furthermore, although the support pillar 13 has been described as having a columnar shape, this embodiment is not limited to this. For example, the support pillar 13 may have any shape, such as a U-shape, as long as it can support at least one side of the gantry body 11.

[0018] As shown in FIG. 1 , the support column 13 houses a drive device (hereinafter referred to as a support column drive device) 25 for sliding the gantry main body 11 in the vertical direction. The support column drive device 25 generates power for sliding the gantry main body 11 in the vertical direction under the control of the gantry control device 23. Specifically, the support column drive device 25 generates power by driving at a rotation speed according to the duty ratio, etc., of a drive signal from the gantry control device 23. The support column 13 receives power from the support column drive device 25 and slides the gantry main body 11 in the vertical direction relative to the support column 13. The support column drive device 25 is realized by a motor such as a servo motor, for example.

[0019] The support column 13 supports the gantry body 11 so that it can rotate around the horizontal axis X. Specifically, the support column 13 receives power from the support column drive device 25, and rotates the gantry body 11 relative to the support column 13 around the horizontal axis. The support column drive device 25 rotates the gantry body 11 between the horizontal and vertical directions by rotating internal teeth in a swivel bearing, for example, under the control of the gantry control device 23. Note that the rotation mechanism that rotates the gantry body 11 is not limited to a swivel bearing, and may be realized by a known mechanism. Rotation of the gantry body 11 by the rotation mechanism enables switching between upright and supine position imaging.

[0020] Fig. 2 is a diagram showing the posture of the gantry 10 during imaging in an upright position, and Fig. 3 is a diagram showing the posture of the gantry 10 during imaging in a supine position. The gantry main body 11 shown in Fig. 2 is supported so that the bore 15 faces vertically relative to the floor surface. The gantry main body 11 shown in Fig. 3 is supported so that the bore 15 faces horizontally relative to the floor surface. The support pillars 13 shown in Figs. 2 and 3 support the gantry main body 11 rotatably about a horizontal axis so that the bore 15 faces horizontally or vertically relative to the floor surface.

[0021] As shown in FIG. 1, the X-ray tube 17 generates X-rays when a high voltage is applied from a high-voltage generator 31. The high-voltage generator 31 is attached to, for example, the rotating frame 21. The high-voltage generator 31 generates a high voltage to be applied to the X-ray tube 17 under the control of the gantry control device 23 from power supplied from a power supply device (not shown) of the gantry main body 11 via a ring-shaped electrode. The high-voltage generator 31 and the X-ray tube 17 are connected via a high-voltage cable (not shown). The high voltage generated by the high-voltage generator 31 is applied to the X-ray tube 17 via the high-voltage cable.

[0022] The X-ray detector 19 detects X-rays generated from the X-ray tube 17 and transmitted through the subject. The X-ray detector 19 is equipped with a plurality of X-ray detection elements (not shown) arranged on a two-dimensional curved surface. Each X-ray detection element detects X-rays from the X-ray tube 17 and converts them into an electrical signal having a peak value corresponding to the intensity of the detected X-rays. Each X-ray detection element includes, for example, a scintillator and a photoelectric conversion element. The scintillator receives X-rays and generates fluorescence. The photoelectric conversion element converts the generated fluorescence into a charge pulse. The charge pulse has a peak value corresponding to the intensity of the X-rays. Specifically, the photoelectric conversion element is a circuit element such as a photomultiplier tube or a photodiode that converts fluorescence into an electrical signal. Note that the X-ray detector 19 according to this embodiment is not limited to an indirect conversion type detector that first converts X-rays into fluorescence and then converts it into an electrical signal, but may be a direct conversion type detector that directly converts X-rays into an electrical signal.

[0023] The DAS 33 is realized by a processor such as a semiconductor integrated circuit in which an integrating circuit and an A / D converter provided for each of a plurality of X-ray detection elements are implemented in parallel. The DAS 33 executes a data collection function 331 and a correction function 332 by a processor that executes a program loaded in a memory. The functions 331 and 332 do not necessarily have to be realized by a single processing circuit. A semiconductor integrated circuit may be configured by combining a plurality of independent processors, and the functions 331 and 332 may be realized by each processor executing a program.

[0024] The DAS 33, by implementing the data collection function 331, collects digital data indicating the intensity of X-rays attenuated by the subject for each view. The DAS 33 is connected to the X-ray detector 19, for example, within the gantry main body 11. The integration circuit integrates electrical signals from the X-ray detection elements over a predetermined view period to generate an integrated signal. The A / D converter A / D converts the generated integrated signal to generate digital data having a data value corresponding to the peak value of the integrated signal. The converted digital data is called projection data. The projection data is a set of digital values ​​of X-ray dose identified by the channel number and column number of the X-ray detection element that generated it, and a view number indicating the acquired view. The projection data is supplied to the console 40, for example, via a non-contact data transmission device (not shown) housed in the gantry main body 11.

[0025] The DAS 33 corrects the detection angle information of the projection data according to a correction amount based on the first reference angle and the subject angle by implementing the correction function 332. The first reference angle is a reference angle in the rotation direction of the X-ray tube for calculating the correction amount. The first reference angle is set as the start angle of image reconstruction. The subject angle is an angle that determines the orientation of the subject placed in the bore 15 in the rotation direction of the X-ray tube. The detection angle information indicates at what angle in the rotation direction of the X-ray tube 17 the X-rays detected by the X-ray detector 19 were generated. For example, the detection angle information may be associated with a view number and / or a digital value of the X-ray dose as projection data.

[0026] The gantry control device 23 controls the column drive device 25, the high-voltage generator 31, the DAS 33, etc. in accordance with commands from the console 40. The gantry control device 23 has, as hardware resources, a processor such as a CPU (Central Processing Unit) and storage devices (memories) such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The gantry drive system is a drive system for the components of the gantry main body 11, such as the high-voltage generator 31, the column drive device 25, and the rotation drive device of the rotating frame 21.

[0027] The console 40 has a processing circuit 41, a memory 42, a display 43, an input interface 44, and a communication interface 45. Data communication between the processing circuit 41, the memory 42, the display 43, the input interface 44, and the communication interface 45 is performed via a bus (BUS). Note that although the console 40 will be described as being separate from the gantry 10, the gantry 10 may include the console 40 or some of the components of the console 40.

[0028] The memory 42 is a storage device such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or an integrated circuit storage device that stores various types of information. The memory 42 stores, for example, projection data and reconstructed image data. In addition to an HDD or SSD, the memory 42 may be a portable storage medium such as a CD (Compact Disc), a DVD (Digital Versatile Disc), or a flash memory. The memory 42 may also be a drive device that reads and writes various types of information from and to semiconductor memory elements such as flash memory and RAM (Random Access Memory). The storage area of ​​the memory 42 may be located within the X-ray computed tomography apparatus 1 or in an external storage device connected via a network. The memory 42 stores a database, which will be described later.

[0029] The display 43 displays various types of information. For example, the display 43 outputs medical images (CT images) generated by the processing circuit 41, a GUI (Graphical User Interface) for receiving various operations from the user, and the like. Any of a variety of displays can be used as the display 43, as appropriate. For example, a liquid crystal display (LCD), a cathode ray tube (CRT) display, an organic electroluminescence display (OLED), or a plasma display can be used as the display 43. The display 42 may be provided on the stand 10. The display 43 may be a desktop type, or may be configured as a tablet terminal or the like capable of wireless communication with the console 40 main body.

[0030] The input interface 44 accepts various input operations from the user, converts the accepted input operations into electrical signals, and outputs the electrical signals to the processing circuitry 41. For example, the input interface 44 accepts, from the user, acquisition conditions for acquiring projection data and a subject angle indicating the orientation of the subject. Examples of the input interface 44 that can be used as appropriate include a mouse, keyboard, trackball, switch, button, joystick, touchpad, and touch panel display. Note that, in this embodiment, the input interface 44 is not limited to a device equipped with physical operation components such as a mouse, keyboard, trackball, switch, button, joystick, touchpad, and touch panel display. For example, an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the apparatus and outputs the electrical signal to the processing circuitry 41 is also included as an example of the input interface 44. The input interface 44 may also be provided on the gantry 10. The input interface 44 may also be configured as a tablet terminal or the like capable of wireless communication with the console 40 main body.

[0031] The communication interface 45 is an interface for data communication with other computers. For example, the communication interface 45 transmits and receives projection data and / or CT image data to and from a PACS (Picture Archiving and Communication System) via a network.

[0032] The processing circuitry 41 controls the overall operation of the X-ray computed tomography apparatus 1 in response to electrical signals of input operations output from the input interface 44. For example, the processing circuitry 41 has, as hardware resources, a processor such as a CPU and memories such as ROM and RAM. The processing circuitry 41 executes an imaging control function 411, a determination function 412, a calculation function 413, a reconstruction function 414, a display control function 415, and the like, by a processor that executes a program loaded in the memory. Each of the functions 411 to 415 is not limited to being realized by a single processing circuit. A processing circuit may be configured by combining multiple independent processors, and each processor may execute a program to realize each of the functions 411 to 415.

[0033] In the imaging control function 411, the processing circuitry 41 issues a command to the gantry control device 23 so that the gantry 10 performs X-ray CT imaging in accordance with the scan conditions. The gantry control device 23 controls the column drive device 25, the high-voltage generator 31, the DAS 33, etc. in accordance with a command from the console 40 so that X-ray CT imaging is performed.

[0034] In the determination function 412, the processing circuitry 41 determines an object angle that indicates the orientation of the object. As a means for determination, for example, the input interface 44, projection data, an optical camera, or various physical sensors may be used.

[0035] In the calculation function 413, the processing circuitry 41 calculates the correction amount used by the correction function 332 of the DAS 33 based on the subject angle and the second reference angle. The second reference angle is the reference angle of the rotation coordinate system of the CT image. For example, the second reference angle is the angle at which the rotation angle around the center point of the CT image is located approximately at the center of the upper side. Note that the second reference angle can be determined to be any angle. The correction amount is the amount of change in the detected angle information.

[0036] In the reconstruction function 414, the processing circuitry 41 reconstructs a CT image of the subject based on the projection data and detection angle information output from the DAS 33. The processing circuitry 41 reconstructs a CT image in which the subject angle is directed toward approximately the center of the upper side. If the detection angle information is corrected in the correction function 415, the processing circuitry 41 reconstructs a CT image of the subject based on the projection data and detection angle information corrected by the correction function 415. The CT image represents the spatial distribution of CT values ​​used to evaluate the attenuation coefficient of a material. The processing circuitry 41 converts the CT image into a cross-sectional image of an arbitrary cross section or a rendering image of an arbitrary viewpoint direction. The conversion is performed based on an input operation received from a user via the input interface 43. For example, the processing circuitry 41 performs three-dimensional image processing such as volume rendering, surface volume rendering, image value projection processing, MPR (Multi-Planer Reconstruction) processing, and CPR (Curved MPR) processing on the CT image to generate rendering image data of an arbitrary viewpoint direction. As the image reconstruction algorithm, an existing image reconstruction algorithm such as the FBP (filtered back projection) method or the iterative reconstruction method may be used.

[0037] In the display control function 415, the processing circuitry 41 displays various information related to CT imaging on the display 43.

[0038] An example of the operation of the X-ray computed tomography apparatus according to the first embodiment will be described below.

[0039] FIG. 4 is a diagram showing the first reference angle, the second reference angle, and the orientation of a CT image. The first reference angle AR1 is a reference angle along the rotation direction of the X-ray tube 17. In this embodiment, the first reference angle AR1 is treated as 0°. The CT image I41 is defined by a Cartesian coordinate system formed by a vertical axis A2 and a horizontal axis A3 that are orthogonal to each other at a center point P1, and a rotational coordinate system that defines a deflection angle clockwise from the vertical axis A3. The second reference angle AR2 is a reference angle of the rotational coordinate system of the CT image. The first reference angle AR1 is set to coincide with the second reference angle AR2. As an example, the second reference angle AR2 is set to an angle at which the rotation angle around the center point of the CT image is located approximately at the center of the upper side. In this case, as shown in FIG. 4, the second reference angle AR2 is 0°. That is, the rotation angle of 0° of the X-ray tube 17 is set to correspond to 0° in the coordinate system of the image space. The direction DR2 of the second reference angle AR2 coincides with the positive direction of the vertical axis A3. In other words, in the rotating coordinate system, the direction DR2 is the 0° direction. The direction DR2 and the direction DR1 of the first reference angle are the same direction. The front of the image of the subject S in the CT image I41 is in the direction DR2. This is because the front of the subject S in the bore 15 faces in the direction DR2 during CT imaging. As another example, if the left side of the subject S in the bore 15 faces in the direction DR2 during CT imaging, a CT image is obtained by rotating the image of the subject S in the CT image I41 by -90° in the rotating coordinate system.

[0040] The first reference angle and the second reference angle do not have to be the same, but for the sake of specific explanation, it is assumed below that the first reference angle and the second reference angle are the same at 0° in the rotation direction of the X-ray tube 17.

[0041] FIG. 5 is a diagram showing a procedure of a CT examination according to the first embodiment.

[0042] As shown in Fig. 5, the processing circuitry 41 determines the object angle by implementing the determination function 412 (step S11). In step S11, it is assumed that the object is not positioned in the bore 15. The object angle represents an angle that determines the orientation of the object in the setting. It is expected that the object will actually be placed in the bore 15 so as to be located at the object angle determined in step S11.

[0043] The subject angle is an angle that determines the orientation of the subject placed in the bore 15 in the rotation direction of the X-ray tube. However, the subject angle may be defined in any orientation of the subject's body, and may be defined as an angle in the lateral direction of the subject or an angle in the back direction of the subject. For example, the subject angle may be defined in the front direction of the subject.

[0044] The object angle may be determined to any angle. The method for determining the object angle is not particularly limited. For example, the processing circuitry 41 determines the object angle according to a user instruction, such as by directly inputting a numerical value or by using a GUI.

[0045] FIG. 6 is a diagram showing the object angle. The arrow AW1 shown in FIG. 6 is a GUI component that indicates the object angle AS1. As shown in FIG. 6, the object angle AS1 is determined in accordance with a user's instruction via the GUI. For example, by moving the arrow AW1 around the central axis A1 of the bore 15 in accordance with the user's instruction, the object angle AS1 is determined in accordance with the angle of the arrow AW1. By using the GUI, it is possible to intuitively determine the object angle.

[0046] When step S11 is performed, the processing circuitry 41, by implementing the calculation function 413, calculates a correction amount such that the detected angle information corresponding to the object angle determined in step S11 substantially coincides with the second reference angle (step S12). The processing circuitry 41 transmits the calculated correction amount to the DAS 33 of the gantry body 11 via the bus.

[0047] FIG. 7 is a diagram illustrating an example of how the correction amount is calculated. As shown in FIG. 7, the first reference angle AR1 is 0°, the subject angle AS2 is defined as the front of the subject S, and the subject angle AS2 is 315°. In this case, without correction, a CT image is obtained in which the front direction of the subject S is shifted by +45° from the direction of approximately the center of the upper edge of the CT image (the 0° direction). To reconstruct a CT image in which the front of the subject S is oriented in the direction of the second reference angle AR2, the projection data acquired from the front of the subject S may be reconstructed as projection data acquired at the second reference angle AR2. That is, the detected angle information of the projection data acquired at the subject angle AS2 may be corrected to the second reference angle AR2. Therefore, the correction amount may be calculated by subtracting the subject angle from the angle obtained by adding 360° to the second reference angle AR2 or the second reference angle AS2. The correction amount in FIG. 7 is calculated as, for example, −315° or +45°.

[0048] The correction amount may be calculated so that the second reference angle AR2 and the subject angle AS2 are any angle. For example, the second reference angle AR2 and the subject angle AS2 may be corrected to 90°. In this case, the correction amount may be calculated as the angle obtained by adding 90° to the second reference angle AR2 or the angle obtained by adding 450° to the second reference angle AS2, minus the subject angle. This allows for the acquisition of a CT image in which the lateral direction of the subject S is oriented toward approximately the center of the top edge of the CT image (0° direction).

[0049] After step S12 is performed, the processing circuitry 41 performs CT imaging (step S13) by implementing the imaging control function 411. Prior to the CT imaging in step S13, the subject is placed under the bore 15. Under the control of the imaging control function 411, the DAS 33 implements the data collection function 331 to collect projection data relating to the subject.

[0050] When step S13 is performed, the DAS 33, by realizing the correction function 332, corrects the detected angle information of the projection data collected in step S13 according to the correction amount calculated in step S12 when collecting the projection data (step S14). In the first embodiment, the DAS 33 corrects the detected angle information of the projection data. In other words, the detected angle information is corrected in the gantry main body 11. After correcting the detected angle information, the non-contact data transmission device transmits the projection data to the console 40.

[0051] 8 is a diagram showing uncorrected projection data PD1 and corrected projection data PD2 of detection angle information. The uncorrected projection data PD1 and corrected projection data PD2 have a view number, X-ray intensity, and detection angle information. The view number is a serial number of the X-ray sampling period. The X-ray intensity is the intensity of X-rays detected by the X-ray detector 19. The detection angle information indicates the rotation angle of the X-ray tube 17 when the projection data is collected.

[0052] In FIG. 8, the subject angle AS2 is assumed to be 315°. The reconstruction start position SP1 and the reconstruction start position SP2 are address positions on the projection data at which the reconstruction of one CT image starts, and are set to the address positions of the projection data for the detection angle information of the first reference angle. The CT image is reconstructed so that the direction of the detection angle information for the reconstruction start positions SP1 and SP2 points toward approximately the center of the top side. That is, when the first reference angle and the second reference angle are the same, a CT image is obtained in which the direction of the second reference angle points toward approximately the center of the top side. Therefore, by correcting the detection angle information so that the detection angle information for the subject angle AS2 is the first reference angle, a CT image in which the subject angle points toward approximately the center of the top side can be obtained.

[0053] The reconstruction start positions SP1 and SP2 in FIG. 8 are projection data with detection angle information of 0°. As an example, if the correction amount is +45°, the processing circuitry 41 rewrites all detection angle information of the uncorrected projection data PD1 to an angle of +45°. For example, the detection angle information in the uncorrected projection data PD1 with the view number 128, X-ray intensity 1000, and detection angle information of 315° is corrected to 0°. The correction of the detection angle information may be performed on the projection data collected in all channels and all columns. As a result, it is possible to arrange the projection data corresponding to the detection angle information of the object angle AS2 (projection data with the view number 128) at the reconstruction start position SP2.

[0054] After step S14 is performed, the processing circuitry 41 reconstructs the CT image by implementing the reconstruction function 414 so that the subject angle coincides with the second reference angle in the CT image (step S15). In step S15, the processing circuitry 41 reconstructs the CT image based on the detection angle information corrected in step S14 and the projection data.

[0055] FIG. 9 illustrates the relationship between detected angle information and the orientation of the subject image in a CT image. The upper part of FIG. 9 shows uncorrected projection data PD1 and a CT image I91 obtained by reconstructing the uncorrected projection data PD1. The lower part of FIG. 9 shows corrected projection data PD2 and a CT image I92 obtained by reconstructing the corrected projection data PD2. CT images I91 and I92 are generated by the same reconstruction process. In the uncorrected projection data PD1, the detected angle information of the projection data corresponding to the subject's front direction is 315°, which is an angle different from the second reference angle AR2 of 0°. In this case, in CT image I91, the front of the subject image does not face the direction of approximately the center MP1 of the upper side. On the other hand, in the corrected projection data PD2, the detected angle information of the projection data corresponding to the subject's front direction is 0°, which is the same angle as the second reference angle AR2 of 0°. Therefore, in CT image I92, the front of the subject image faces the direction of approximately the center MP1 of the upper side. As a result, it is possible to reconstruct a CT image of an object whose object angle is oriented with its top side facing up, without changing the reconstruction process, regardless of the actual orientation of the object.

[0056] When step S15 is performed, the processing circuitry 41, by implementing the display control function 415, displays the CT image reconstructed in step S15 on the display 43 (step S16). For example, the processing circuitry 41 may display the CT image I92 in FIG. 9. This makes it possible to display a CT image of a subject whose subject angle is oriented in a fixed direction, regardless of the actual orientation of the subject. Note that the processing circuitry 41 may display, together with the CT image, for example, the correction amount calculated in step S12, or may display an input screen for the user to input the subject angle.

[0057] When step S16 is performed, the CT examination according to the first embodiment is completed.

[0058] The correction of the orientation of the subject on the CT image shown in FIG. 5 is one example, and various additions, modifications and / or deletions are possible as long as the gist of the first embodiment is not changed.

[0059] (Variation 1) The processing circuitry 41 in the first embodiment determines the object angle using a GUI in accordance with a user's instruction. The processing circuitry 41 in the first modification determines the object angle using a camera, a physical sensor, and / or projection data. In this case, the object angle is determined after the object is aligned, so the object angle coincides with the orientation of the object.

[0060] Specifically, the subject angle may be determined by capturing an image of the subject, a pole for fixing the subject's posture during standing imaging, and / or a chair used during sitting imaging. When the subject angle is determined by capturing an image using a camera, the subject angle may be determined by analyzing the subject's orientation, the pole's installation position, and / or the chair's installation orientation from the captured image using image recognition or the like. The subject angle may also be determined by detecting physical quantities related to the subject, the pole, and / or the chair using a physical sensor. The subject angle may also be determined by recognizing the subject's orientation by calculating the subject's body thickness from the X-ray dose of projection data collected by the imaging control function 411. The subject's body thickness may be, for example, projection data collected by a positioning scan and / or a main scan. When projection data collected by a main scan is used, steps S11 and S12 may be performed after step S13.

[0061] As described above, according to the first modification, it is possible to mechanically and accurately determine the object angle.

[0062] (Variation 2) The X-ray computed tomography apparatus in the first embodiment performs correction by directly rewriting the projection data. The X-ray computed tomography apparatus in the second modification performs correction by rewriting the projection data read into RAM during reconstruction. Since the second modification relates to a method for correcting the detected angle information in step S14 in the first embodiment, step S14 in FIG. 5 will be described. Note that prior to step S14, the memory 42 provided in the console 40 is assumed to store the projection data and the detected angle information of the projection data.

[0063] In step S14, the processing circuitry 41 corrects the detected angle information of the projection data read from the memory 42 for pre-processing of reconstruction. Specifically, the detected angle information of the projection data read from the memory 42 to the RAM of the DAS 33 during pre-processing of reconstruction is corrected based on the correction amount. The projection data to be corrected is the projection data expanded on the RAM. It is preferable that the projection data stored in the memory 42 is stored without correction.

[0064] As described above, according to the second modification, it is possible to correct the orientation of the subject on the CT image without directly rewriting the projection data.

[0065] (Variation 3) The X-ray computed tomography apparatus in the first embodiment reconstructs a CT image based on the projection data and corrected detection angle information after CT imaging. The X-ray computed tomography apparatus in the third modification reconstructs a real-time CT image based on the projection data and corrected detection angle information in a view range going back from the current view number by the number of views required for image reconstruction during CT imaging.

[0066] The real-time CT images are displayed without post-reconstruction processing. As shown in FIG. 5 or FIG. 13, all corrections of the projection data in the first embodiment are performed as pre-reconstruction processing. Therefore, this embodiment can also be applied to real-time CT images. Furthermore, the processing circuitry 51 displays the real-time CT images one by one on the display 43 by implementing the display control function 515. Note that the X-ray computed tomography apparatus according to the third modification can also correct the orientation of the subject and display the positioning image.

[0067] As described above, according to Modification 3, it is possible to display a real-time CT image in which the orientation of the subject has been corrected. Note that Modification 3 can also be applied to Modification 2.

[0068] (Variation 4) The X-ray computed tomography apparatus in the first embodiment corrects the orientation of the subject on the CT image for one CT scan. The X-ray computed tomography apparatus in the fourth modification corrects the orientation of the subject on the CT image for multiple CT scans to align them.

[0069] By implementing the correction function 322, the DAS 33 calculates a correction amount for the second CT scan such that the positional relationship between the reference angle and the subject angle in the first CT scan performed by the gantry 10, in which the central axis A1 of the bore 15 is oriented in the Y-axis direction or the Z-axis direction, approximately matches the positional relationship between the reference angle and the subject angle in the second CT scan performed by the gantry 10, in which the central axis A1 of the bore 15 is oriented in a direction different from that in the first CT scan. The first CT scan is, for example, a supine scan, in which the central axis A1 of the bore 15 is oriented in the Z-axis direction. The second CT scan is, for example, an upright scan, in which the central axis A1 of the bore 15 is oriented in the Y-axis direction.

[0070] FIG. 10 shows the orientation of the subject S in the bore 15 during supine position imaging SC1 and upright position imaging SC2. The left diagram shows supine position imaging SC1. At this time, the gantry main body 11 and the support column 13 assume the position shown in FIG. 3. The right diagram shows upright position imaging SC2. At this time, the gantry main body 11 and the support column 13 assume the position shown in FIG. 2. During supine position imaging SC1, the first reference angle AR1, the second reference angle AR2, and the subject angle AS3 all coincide at 0°. When reconstruction is performed based on the projection data collected under this condition, a CT image is obtained in which the front direction of the subject S is directed toward approximately the center of the upper side. On the other hand, during upright position imaging SC2, the first reference angle AR1 and the second reference angle AR2 all coincide at 0°, but the subject angle AS4 is 315°. When reconstruction is performed based on the uncorrected projection data collected in this state, a CT image is obtained in which the front direction of the subject S is oriented at +45° from approximately the center of the upper side in the rotational coordinate system of the CT image.

[0071] The processing circuitry 41 corrects the detected angle information of the subject angle AS4 in the upright position image acquisition SC2 to match the subject orientation in the projection data obtained in the supine position image acquisition SC1 with the second subject angle. Specifically, the processing circuitry 41 performs the correction described in the first embodiment, the second embodiment, or Modification 2. Note that the upright position image acquisition SC2 may be the first CT scan, and the supine position image acquisition SC1 may be the second CT scan. In this case, the detected angle information of the subject angle AS3 in the left diagram of FIG. 10 may be corrected to match the subject angle AS4 in the right diagram. Furthermore, three or more projection data may be corrected. In this case, the first CT scan may be fixed, and a new CT scan may be newly designated as the second CT scan.

[0072] 11 is a diagram showing an example of a display screen IF14 displaying a CT image I141 based on uncorrected projection data obtained by supine position imaging SC1 and a CT image I142 based on corrected projection data obtained by upright position imaging SC2. The display screen IF14 displays the CT image I141 and the CT image I142, in which the subject's orientation is aligned on the CT images, together. Furthermore, by implementing the display control function 415, the processing circuitry 41 displays the CT image I141 obtained by supine position imaging SC1 and the CT image I142 obtained by upright position imaging SC2 on the display 43, along with visual information that allows each CT image to be identified. For example, the visual information may be text indicating the body position, such as "supine position" or "standing position."

[0073] It should be noted that three or more CT images may be displayed together. Furthermore, the displayed visual information is not limited to text indicating the body position. For example, it may be a diagram indicating the body position, or may be distinguished by color.

[0074] As described above, according to Modification 4, it is possible to display multiple CT images that are unified in the subject's orientation from projection data captured in the bore while the subject is facing in different directions. Furthermore, by displaying visual information in addition to each CT image, it is possible to distinguish between the CT images.

[0075] (Second embodiment) In the X-ray computed tomography apparatus of the first embodiment, the correction function 332 is included in the gantry 10. In the X-ray computed tomography apparatus of the second embodiment, the correction function is included in the console 50. The X-ray computed tomography apparatus of the second embodiment will be described below. However, components having the same functions as those in the first embodiment will be given the same reference numerals and will be described repeatedly only when necessary.

[0076] Fig. 12 is a diagram showing the configuration of an X-ray computed tomography apparatus 2 according to the second embodiment. As shown in Fig. 12, the X-ray computed tomography apparatus 2 accommodates a DAS 35 in a gantry 10. The DAS 35 collects projection data using a data collection function 331.

[0077] The processing circuit 51 executes an imaging control function 411, a determination function 412, a calculation function 413, a reconstruction function 414, a display control function 415, a correction function 516, a storage function 517, etc., by a processor that executes a program loaded in memory. Each of the functions 411 to 415, 516, and 517 does not necessarily have to be realized by a single processing circuit. A processing circuit may be configured by combining multiple independent processors, and each processor may execute a program to realize each of the functions 411 to 415, 516, and 517. The correction function 516 corresponds to the correction function 332.

[0078] In the correction function 516, the processing circuitry 51 corrects the detected angle information of the projection data in accordance with the correction amount based on the first reference angle and the object angle.

[0079] In the storage function 517, the processing circuitry 51 stores the projection data in the memory 52. ​​For example, the processing circuitry 51 may store the projection data whose detection angle information has been corrected in the memory 52. ​​Note that the amount of correction may be stored in association with the projection data.

[0080] An example of the operation of the X-ray computed tomography apparatus according to the second embodiment will be described below.

[0081] 13 is a diagram showing a processing procedure for a CT examination according to the second embodiment. As shown in Fig. 13, the processing circuitry 51 determines the object angle by implementing the determination function 512 (step S21). Step S21 corresponds to step S11 in the first embodiment.

[0082] After step S21 is performed, the processing circuitry 51, by implementing the calculation function 513, calculates a correction amount such that the detection angle information corresponding to the object angle determined in step S21 substantially coincides with the second reference angle (step S22). Step S22 corresponds to step S12 in the first embodiment.

[0083] After step S22 is performed, the processing circuitry 51 performs CT imaging by implementing the imaging control function 511 (step S23). In step S23, the DAS 35 collects projection data. The non-contact data transmission device transmits the projection data collected by the DAS 35 to the console 50.

[0084] When step S23 is performed, the processing circuit 51, by implementing the correction function 516, corrects the detection angle information of the projection data collected in step S23 according to the correction amount calculated in step S22 before storing the projection data in the memory 52 (step S24).

[0085] When step S24 is performed, the processing circuitry 51 realizes the storage function 516 to store the projection data, the detection angle information of which has been corrected, in the memory 52 (step S25).

[0086] After step S25 is performed, the processing circuitry 51 reconstructs a CT image by implementing the reconstruction function 514 (step S26). Step S26 corresponds to step S15 in the first embodiment.

[0087] When step S26 is performed, the processing circuitry 51 displays the CT image reconstructed in step S26 on the display 53 by implementing the display control function 515 (step S27). Step S27 corresponds to step S16 in the first embodiment.

[0088] When step S27 is performed, the CT examination according to the second embodiment is completed.

[0089] The correction of the orientation of the subject on the CT image shown in FIG. 13 is an example, and various additions, modifications and / or deletions are possible as long as the gist of the second embodiment is not changed.

[0090] Note that Modifications 1-4 are also applicable to the second embodiment, and in Modification 2, the processing circuitry 51 may implement the storage function 517 to associate the correction amount calculated in step S22 with the projection data and store it in the memory 51. In this case, the processing circuitry 51 implements the correction function 516 to correct the detected angle information in accordance with the correction amount stored in step S25.

[0091] FIG. 14 is a diagram showing an example of correction based on a correction amount associated with projection data and stored as incidental information. FIG. 14 shows uncorrected projection data PD1, a correction amount AI1 associated with the uncorrected projection data PD1 and stored, and corrected projection data PD3 expanded in RAM. The uncorrected projection data PD1 corresponds to the uncorrected projection data of FIGS. 8 and 9. The correction amount AI1 is the correction amount calculated in step S22 and stored in step S25 in the second embodiment. The correction amount is, for example, +45°. The processing circuitry 51 corrects the uncorrected projection data PD1 read into the RAM of the processing circuitry 51 during reconstruction based on the correction amount AI1 to generate corrected projection data PD3. By storing the correction amount associated with the projection data, it is possible to correct the orientation of the subject on the CT image even after the CT examination is completed.

[0092] (Summary) The X-ray computed tomography apparatus according to this embodiment has a gantry main body 11 and a processing circuitry 41. The gantry main body 11 supports the X-ray tube 17 and the X-ray detector 19 rotatably around the central axis A1 of the bore 15. The processing circuitry 41 corrects the detection angle information of the projection data in accordance with a correction amount based on a first reference angle in the rotation direction of the X-ray tube 17 and a subject angle that determines the orientation of the subject in the bore 15, and reconstructs a CT image of the subject based on the projection data and the corrected detection angle information.

[0093] Here, this embodiment is compared with a comparative example in which the orientation of the subject on a CT image is corrected as a post-processing step after CT image reconstruction. In the comparative example, the orientation of the subject on a CT image is corrected by rotating the reconstructed CT image as a post-processing step. However, if the rotation angle is not an integer multiple of 90°, the pixel values ​​before rotation do not correspond one-to-one to the pixel values ​​after rotation, resulting in image blurring at the corresponding pixels. Furthermore, because the rotation is performed as a post-processing step for reconstruction, it takes a long time to confirm the corrected CT image. This disrupts the workflow from capturing to interpreting CT images that do not require correction. In contrast to the comparative example, this embodiment corrects the detected angle information of the projection data as a pre-processing step for reconstruction. Therefore, because the detected angle information is corrected, image blurring, as in the comparative example, is eliminated, enabling improved image quality. Furthermore, because only the detected angle information is corrected, the reconstruction process is the same as the comparative example and can be easily implemented. Furthermore, by correcting the detected angle information, the subject image can be oriented in a direction desired by the user.

[0094] (Third embodiment) The X-ray computed tomography apparatuses in the first and second embodiments correct detected angle information to correct the orientation of the subject on the CT image. The X-ray computed tomography apparatus in the third embodiment corrects the exposure start angle. The exposure start angle is the angle in the rotation direction of the X-ray tube 17 at which the X-ray tube 17 starts emitting X-rays during CT imaging. The processing circuitry 61 in the third embodiment may correct the exposure start angle so that the second CT imaging of the subject is performed using the same trajectory of the X-ray tube 17 as in the first CT imaging. The console 60 corresponds to the console 40 in the first embodiment.

[0095] An X-ray computed tomography apparatus according to the third embodiment will be described below, with the same reference numerals used for components having the same functions as those in the first or second embodiment, and redundant explanations will be given only when necessary.

[0096] Fig. 15 is a diagram showing the configuration of an X-ray computed tomography apparatus 3 according to the third embodiment. As shown in Fig. 15, a processing circuit 61 executes an imaging control function 411, a determination function 412, a calculation function 413, a reconstruction function 414, a display control function 415, a correction function 516, an X-ray tube angle control function 618, and the like, by a processor that executes a program loaded in a memory. Each of the functions 411 to 415, 516, and 618 does not necessarily have to be realized by a single processing circuit. A processing circuit may be configured by combining a plurality of independent processors, and each processor may execute a program to realize each of the functions 411 to 415, 516, and 618.

[0097] In the calculation function 413, the processing circuitry 61 calculates a correction amount for the second exposure start angle of the X-ray tube 17 based on the first exposure start angle of the X-ray tube 17, the current position of the X-ray tube 17, and the subject angle. The first exposure start angle is the exposure start angle in the first CT imaging. The second exposure start angle is the exposure start angle in the second CT imaging. For example, the exposure start angle is controlled by the first reference angle.

[0098] In the correction function 516, the processing circuitry 61 corrects the second exposure start angle based on the calculated correction amount before the second CT imaging.

[0099] In the X-ray tube angle control function 618, the processing circuitry 61 moves the X-ray tube 17 to the second exposure start angle corrected by the correction function 516. Specifically, the X-ray tube 17 is moved around the central axis A1 of the bore 15 by the correction amount from the current position of the X-ray tube 17, and the angle of the X-ray tube 17 after the movement is set as the second exposure start angle.

[0100] An example of the operation of the X-ray computed tomography apparatus according to the third embodiment will be described below.

[0101] 16 is a diagram showing the first exposure start angle AE1 in the first CT imaging. As shown in FIG. 16, the first CT imaging is, for example, imaging in a supine position. In FIG. 16, the first exposure start angle AE1 is 0°. The orientation AW16 of the subject S is the front direction of the subject. The subject angle AS5 is 0°. In this case, the X-ray tube 17 starts exposure from the front direction of the subject S.

[0102] FIG. 17 is a diagram showing an uncorrected angle AX1 at which the X-ray tube 17 is positioned in the second CT imaging. As shown in FIG. 17, the second CT imaging is, for example, an upright position imaging. In FIG. 17, the angle AX1 is 0°. The direction AW17 of the subject S is the front direction of the subject. The subject angle is 315°. In this case, the X-ray tube 17 starts exposure from a direction shifted 45° from the front direction of the subject S.

[0103] In order for the X-ray tube 17 to follow the same trajectory relative to the subject S during the first and second CT scans, the processing circuitry 61, by implementing the calculation function 413, calculates a correction amount for matching the first exposure start angle AE1 and the second exposure start angle relative to the subject angle. As an example, the correction amount is calculated as angle AX1 or an angle obtained by adding 360° to angle AX1 minus the subject angle. Specifically, in FIG. 17, the correction amount of the second exposure start angle may be calculated as +315° or −45°. The processing circuitry 61, by implementing the correction function 516, corrects the second exposure start angle in accordance with the calculated correction amount. Specifically, in FIG. 17, the second exposure start angle may be corrected to +315° or −45° from angle AX1 based on the calculated correction amount.

[0104] The processing circuitry 61, by implementing the X-ray tube angle control function 618, moves the exposure start angle of the X-ray tube 17 in the second CT imaging in accordance with the calculated correction amount. In Fig. 17, the second exposure start angle is moved by +315° or -45° from the angle AX1 of 0° to an angle of 315°. As a result, it is possible to match the trajectory of the X-ray tube 17 relative to the orientation of the subject in the first CT imaging and the second CT imaging, which are performed in different body positions.

[0105] (Summary) The X-ray computed tomography apparatus according to this embodiment has a gantry main body 11 and a processing circuit 61. The gantry main body 11 supports the X-ray tube 17 and the X-ray detector 19 rotatably around the central axis A1 of the bore 15. The processing circuit 61 corrects the second exposure start angle in accordance with a correction amount based on the first exposure start angle in the rotation direction of the X-ray tube 17 and the subject angle.

[0106] Here, this embodiment is compared with a comparative example in which the first and second CT imaging are performed without matching the first and second exposure start angles relative to the orientation of the subject. In the comparative example, X-ray exposure is started at different exposure start angles relative to the orientation of the subject in the first and second CT imaging. The CT images contain noise due to the trajectory of the X-ray tube. Therefore, in the comparative example, noise due to the trajectory of the X-ray tube appears in different directions in the CT images captured by the first and second CT imaging, making it difficult to compare the CT images. In contrast to the comparative example, in this embodiment, the first and second CT imaging are performed with the first and second exposure start angles relative to the orientation of the subject matched. Therefore, by making the noise tendencies similar between the reconstructed CT images, it is possible to easily distinguish noise from the subject image.

[0107] According to at least one of the embodiments described above, it is possible to generate a CT image that is easy for the user to check.

[0108] The term "processor" used in the above description refers to a circuit such as a CPU, a GPU, an application specific integrated circuit (ASIC), a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA)). A processor realizes its function by reading and executing a program stored in a memory circuit. Note that instead of storing a program in a memory circuit, the program may be directly embedded in the processor circuit. In this case, the processor realizes its function by reading and executing the program embedded in the circuit. On the other hand, if the processor is, for example, an ASIC, instead of storing a program in a memory circuit, the function is directly embedded in the processor circuit as a logic circuit. Note that each processor in this embodiment is not limited to being configured as a single circuit for each processor, but may be configured as a single processor by combining multiple independent circuits to realize its function. Furthermore, the functions of the components in FIGS. 1, 12, and 15 may be realized by integrating them into one processor.

[0109] Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations of embodiments can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0110] 1 X-ray computed tomography equipment 10 Mounting stand 11 Stand body 13 Posts 15 Aperture 17 X-ray tube 19 X-ray detector 21 Rotating Frame 23 Mounting control device 25 Pillar drive unit 31 High voltage generator 33 Data Acquisition System (DAS) 40 Console 41 Processing circuit 42 memory 43 Display 44 input interfaces 45 Communication Interface 411 Imaging control function 412 Decision Function 413 Calculation Function 414 Reconfiguration function 415 Display Control Function

Claims

1. a gantry body that supports an X-ray tube, an X-ray detector, and a data acquisition circuit so as to be rotatable about a central axis of a bore, wherein the X-ray tube generates X-rays, the X-ray detector detects the X-rays that have been generated from the X-ray tube and passed through a subject, and the data acquisition circuit acquires projection data via the X-ray detector; a correction unit that corrects detected angle information of the projection data according to a correction amount based on a first reference angle in a rotation direction of the X-ray tube and an object angle that determines a direction of the object in the bore; a reconstruction unit that reconstructs a CT image of the subject based on the projection data and the corrected detected angle information; An X-ray computed tomography apparatus comprising:

2. 2. The X-ray computed tomography apparatus according to claim 1, wherein the reconstruction unit reconstructs the CT image so that the subject angle coincides with a second reference angle in the CT image.

3. 3. The X-ray computed tomography apparatus according to claim 2, wherein the second reference angle is an angle at which a rotation angle around a center point of the CT image is located approximately at the center of an upper side.

4. 2. The X-ray computed tomography apparatus according to claim 1, wherein the correction unit is provided in the gantry body and corrects the detected angle information in accordance with the correction amount when the projection data is collected.

5. a storage unit provided in the console for storing the projection data; the correction unit is provided in the console and corrects the detected angle information before the projection data is stored by the storage unit; 2. The X-ray computed tomography apparatus according to claim 1, wherein the storage unit stores the projection data in which the detected angle information has been corrected.

6. a storage unit provided in the console for storing the projection data; 2. The X-ray computed tomography apparatus according to claim 1, wherein the correction unit corrects the detected angle information of the projection data read from the storage unit for preprocessing of reconstruction.

7. the storage unit stores the correction amount in association with the projection data; The X-ray computed tomography apparatus according to claim 6 , wherein the correction unit corrects the detected angle information in accordance with the correction amount stored in association with the projection data.

8. Further comprising a display control unit, the reconstruction unit reconstructs a real-time CT image based on the projection data of a view range going back from a current view number by the number of views required for image reconstruction during CT imaging and the corrected detection angle information, The display control unit displays the real-time CT images one by one on a display device.

7. An X-ray computed tomography apparatus according to claim 4.

9. 2. The X-ray computed tomography apparatus according to claim 1, wherein the subject angle is an angle in a front direction of the subject.

10. The X-ray computed tomography apparatus according to claim 1 , further comprising a determination unit that determines the subject angle in accordance with a user's instruction.

11. The X-ray computed tomography apparatus according to claim 1 , further comprising a determination unit that determines the subject angle based on the projection data.

12. a camera for generating an optical image; The X-ray computed tomography apparatus according to claim 1 , further comprising: a determination unit that determines the subject angle based on the optical image generated by the camera.

13. a physical sensor capable of detecting a physical quantity; The X-ray computed tomography apparatus according to claim 1 , further comprising: a determination unit that determines the subject angle based on the physical quantity detected by the physical sensor.

14. further comprising a support unit, a calculation unit, and a display control unit; the support portion supports the pedestal body rotatably around a horizontal axis so that the bore faces a horizontal direction or a vertical direction with respect to a floor surface; the calculation unit calculates the correction amount for the second CT imaging so as to substantially match a positional relationship between the first reference angle and the detection angle information corresponding to the subject angle in a first CT imaging performed by the gantry, in which the bore is oriented in the horizontal direction or the vertical direction with respect to a floor surface, with a positional relationship between the first reference angle and the detection angle information corresponding to the subject angle in a second CT imaging performed by the gantry main body, in which the bore is oriented in a direction different from that in the first CT imaging; the correction unit corrects the detected angle information related to the second CT imaging in accordance with the correction amount; the reconstruction unit reconstructs a CT image based on the projection data and the corrected detection angle information; The X-ray computed tomography apparatus according to claim 1 , wherein the display control unit displays the CT image obtained by the first CT imaging and the CT image obtained by the second CT imaging together on a display device.

15. 15. The X-ray computed tomography apparatus according to claim 14, wherein the display control unit displays the CT image obtained by the first CT imaging and the CT image obtained by the second CT imaging on the display device together with visual information that enables each of the CT images to be identified.

16. 2. The X-ray computed tomography apparatus according to claim 1, wherein the correction unit corrects an exposure start angle, which is an angle at which exposure of the X-ray tube starts in CT imaging, in accordance with the correction amount in the rotation direction of the X-ray tube.

17. a gantry body that supports an X-ray tube, an X-ray detector, and a data acquisition circuit so as to be rotatable about a central axis of a bore, wherein the X-ray tube generates X-rays, the X-ray detector detects the X-rays that have been generated from the X-ray tube and passed through a subject, and the data acquisition circuit acquires projection data via the X-ray detector; a correction unit that corrects an exposure start angle, which is an angle at which exposure of the X-ray tube starts in CT imaging, according to a correction amount based on a first reference angle in a rotation direction of the X-ray tube and a subject angle that determines a direction of the subject in the bore; An X-ray computed tomography apparatus comprising:

Images