X-ray CT scanner and image processing method

Abstract

To reduce differences in CT image quality caused by variations in the subject's posture during imaging. [Solution] The X-ray CT apparatus according to this embodiment comprises a specification unit, a determination unit, and a generation unit. The specification unit identifies a stand state information that represents the state of the stand, including at least one of posture information representing the orientation of the stand having an opening and object information representing objects other than the subject present in the opening. The determination unit determines image quality adjustment parameters to be used in the reconstruction process based on the identified stand state information and parameter information that associates the stand state information with image quality adjustment parameters consisting of a plurality of parameters that determine the image quality of the reconstructed image generated by the reconstruction process. The generation unit performs a reconstruction process on the first detection data collected by irradiating the subject with X-rays using the determined image quality adjustment parameters, and generates a reconstructed image.

Description

Technical Field

[0001] The embodiments disclosed in this specification and the drawings relate to an X-ray CT apparatus and an image processing method.

Background Art

[0002] Conventionally, an X-ray computed tomography apparatus (hereinafter also referred to as an X-ray CT (computed tomography) apparatus) capable of imaging a subject in a supine position or a standing position is known.

[0003] By the way, in an X-ray CT apparatus, in order for a user to obtain a CT image with a desired image quality, various parameters (hereinafter also referred to as image quality adjustment parameters) for adjusting the image quality of the CT image are used. Known image quality adjustment parameters include correction data for adjusting the image quality based on the pixel values of water and air, X-ray tube alignment representing the arrangement of an X-ray tube provided on a gantry, and image quality parameters for determining the image quality of a CT image.

[0004] In a conventional X-ray CT apparatus capable of imaging a subject in a supine position or a standing position, when adjusting the image quality of a CT image, image quality adjustment parameters corresponding to the imaging conditions are used regardless of the imaging position (imaging mode) of the subject. However, it is known that when imaging in the supine mode and when imaging in the standing mode, the influence of gravity on the unit composed of an X-ray tube, an X-ray detector, etc. inside the gantry is different, so there is a difference in the X-ray data collected.

[0005] Therefore, even when imaging under the same imaging conditions, there is a possibility that a difference in the image quality of the obtained CT image may occur depending on whether the imaging mode is the supine mode or the standing mode.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0007] One of the problems that the embodiments disclosed herein and in the drawings aim to solve is to reduce the differences in CT image quality caused by differences in the subject's posture during imaging. However, the problems that the embodiments disclosed herein and in the drawings aim to solve are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described later can also be positioned as other problems. [Means for solving the problem]

[0008] The X-ray CT apparatus according to this embodiment comprises a specification unit, a determination unit, and a generation unit. The specification unit identifies a stand state information that represents the state of the stand, including at least one of posture information representing the orientation of the stand having an opening and object information representing objects other than the subject present in the opening. The determination unit determines image quality adjustment parameters to be used in the reconstruction process based on the identified stand state information and parameter information that associates the stand state information with image quality adjustment parameters consisting of a plurality of parameters that determine the image quality of the reconstructed image generated by the reconstruction process. The generation unit performs a reconstruction process on the first detection data collected by irradiating the subject with X-rays using the determined image quality adjustment parameters, and generates a reconstructed image. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows an example of the configuration of an X-ray CT apparatus according to an embodiment. [Figure 2] Figure 2 is a perspective view showing an example of the state of the mounting device in the standing mode according to the embodiment. [Figure 3] Figure 3 is a perspective view showing an example of the state of the support device in the supine mode according to the embodiment. [Figure 4] Figure 4 illustrates an example of the calculation process for image quality adjustment parameters according to this embodiment. [Figure 5]Figure 5 illustrates an example of the calculation process for image quality adjustment parameters according to the embodiment. [Figure 6] Figure 6 illustrates an example of determining image quality adjustment parameters and reconstruction processing using image quality adjustment parameters according to this embodiment. [Figure 7] Figure 7 illustrates an example of determining image quality adjustment parameters and reconstruction processing using image quality adjustment parameters according to this embodiment. [Figure 8] Figure 8 is a flowchart showing an example of the calculation and storage process of image quality adjustment parameters according to this embodiment. [Figure 9] Figure 9 is a flowchart showing an example of determining image quality adjustment parameters and reconstruction processing using image quality adjustment parameters according to this embodiment. [Modes for carrying out the invention]

[0010] Embodiments of the X-ray CT apparatus and image processing method will be described below with reference to the drawings. The X-ray CT apparatus according to this embodiment has a structure that allows the orientation of the stand to be changed between an upright imaging state in which the subject P can be imaged in an upright position and a supine imaging state in which the subject P can be imaged in a supine position. In the following embodiments, parts with the same reference numerals perform similar operations, and redundant explanations will be omitted as appropriate.

[0011] Figure 1 shows an example of the configuration of an X-ray CT apparatus 1 according to an embodiment. As shown in Figure 1, the X-ray CT apparatus 1 has a stand unit 10 and a console unit 100. For example, the stand unit 10 is installed in the CT examination room, and the console unit 100 is installed in a control room adjacent to the CT examination room. The stand unit 10 and the console unit 100 are connected to each other by wire or wireless so that they can communicate with each other.

[0012] In this embodiment, the axial direction perpendicular to the floor surface, i.e., the vertical direction, is defined as the Z-axis direction, and the two directions perpendicular to the Z-axis direction and mutually perpendicular are defined as the X-axis direction and the Y-axis direction, respectively.

[0013] The gantry device 10 is a scanning device having a configuration for performing X-ray CT imaging on a subject P in a standing position or a lying position. The console device 100 is a computer that controls the gantry device 10.

[0014] The gantry device 10 includes a gantry (also referred to as a gantry) 11, a column 13, a rotation drive device 23, and a gantry control device 25.

[0015] The gantry 11 has an imaging system related to imaging of the subject P and an opening 15 into which the subject P can be inserted. The column 13 supports the gantry 11 such that the orientation of the opening 15 can be changed between the vertical direction and the horizontal direction and the gantry 11 can be moved along the vertical direction.

[0016] In FIG. 1, the gantry 11 is supported by the column 13 as a cantilever beam, but is not limited thereto. For example, the gantry 11 may be supported by a plurality of columns (for example, two columns). The column 13 may be referred to as a column portion.

[0017] The gantry 11 has an opening 15 that forms an imaging space related to imaging of the subject P. The gantry 11 is a substantially cylindrical structure in which the opening 15 is formed. As shown in FIG. 1, the gantry 11 houses an X-ray tube 17 and an X-ray detector 19 that are arranged to face each other across the opening 15. The X-ray tube 17 and the X-ray detector 19 are included in the imaging system related to imaging of the subject P in the present embodiment.

[0018] The imaging system may further include a data acquisition circuit (hereinafter also referred to as a DAS (Data Acquisition System)) 33, a high voltage generator 31, a collimator, a wedge, and the like. That is, the gantry 11 has an imaging system related to imaging of the subject P. The gantry 11 is supported by the column 13 so as to be movable in the vertical direction along the column 13.

[0019] The gantry 11 is supported by the column 13 such that the orientation of the opening 15 can be changed between the vertical direction and the horizontal direction. The orientation of the opening 15 corresponds to, for example, the direction in which the top plate 30 is inserted into the opening 15, or in other words, the direction along the rotation axis A1.

[0020] The gantry 11 includes a main frame (not shown) formed of a metal such as aluminum, and a rotating frame 21 that is rotatably supported around the rotation axis A1 via bearings or the like by the main frame. An annular electrode (not shown) is provided at the contact portion between the main frame and the rotating frame 21. A conductive slider (not shown) is attached to the contact portion of the main frame so as to make sliding contact with the annular electrode.

[0021] The column 13 is a base that supports the gantry 11 away from the floor surface.

[0022] The column 13 has a columnar shape such as a cylindrical shape or a prismatic shape, for example. The column 13 is formed of an arbitrary material such as plastic or metal, for example. The column 13 is attached to the side surface portion of the gantry 11, for example. The column 13 supports the gantry 11 in a state where the rotation axis A1 of the opening 15 is substantially perpendicular to the floor surface so that the subject P in the sitting or standing position can be subjected to X-ray CT imaging and is slidable in the vertical direction.

[0023] Typically, the column 13 is provided on one side portion of the gantry 11. However, the present embodiment is not limited to this. For example, two columns 13 may be connected to both side portions of the gantry 11. That is, at least one column 13 supports the gantry 11 so as to be movable in the vertical direction.

[0024] Also, although the column 13 has a columnar shape, the present embodiment is not limited to this. For example, the column 13 may have any shape such as a U-shape as long as it can support at least one side portion of the gantry 11.

[0025] The support column 13 supports the frame 11 so that the rotation axis A1 is rotatable around a horizontal axis (hereinafter also referred to as the tilt axis) parallel to the floor surface, between the vertical and horizontal directions. The support column 13 and the frame 11 are connected, for example, via a swivel bearing, so that the frame 11 is rotatable around the tilt axis.

[0026] Specifically, the support column 13 is provided with a linear motion guide along the vertical direction. A swivel seat bearing is provided on the block that can move along the linear motion guide. The block moves along the linear motion guide by the drive of a motor under the control of the movement control circuit 27.

[0027] Furthermore, the gears that mesh with the gears (internal teeth) in the slewing bearing are connected to the motor's rotating shaft via various gears that generate a predetermined torque. The internal teeth in the slewing bearing rotate under the drive of the motor, which is controlled by the movement control circuit 27.

[0028] As a result, the frame 11 is rotatable around the X-axis in Figure 1 and movable along the vertical direction. The linear guide and swivel bearing described above correspond to the frame movement mechanism 131 related to the movement of the frame 11. That is, the frame movement mechanism 131 is mounted on the support column 13.

[0029] The frame movement mechanism 131 moves the frame 11 by moving blocks along a linear guide arranged vertically, under the control of the movement control circuit 27. This allows the frame 11 to move up and down along the vertical direction. The mechanism for moving the frame 11 along the vertical direction is not limited to a linear guide, but may be implemented by a known mechanism such as a rack and pinion.

[0030] Furthermore, the frame movement mechanism 131 rotates the frame 11 between the horizontal and vertical directions by the rotation of the internal teeth in the swivel bearing, under the control of the movement control circuit 27.

[0031] The rotation mechanism for rotating the mount 11 is not limited to a swivel bearing, but may be implemented using a known mechanism. By rotating the mount 11 with the rotation mechanism, it becomes possible to switch between a standing or sitting imaging state (also called standing mode) and a supine imaging state (also called supine mode), that is, to switch between standing mode and supine mode.

[0032] For example, when performing supine imaging on a subject P, the stand movement mechanism 131 rotates the stand 11 under the control of the movement control circuit 27 so that the opening 15 is vertical. After the subject P lies down on the tabletop 30, the tabletop 30 is moved horizontally by the tabletop movement mechanism 37 (described later), making it possible to perform supine imaging on the subject P in the same way as with a normal X-ray CT scanner.

[0033] Furthermore, when performing standing imaging on subject P, the rotation mechanism in the stand movement mechanism 131 rotates the stand 11 under the control of the movement control circuit 27 so that the opening 15 is horizontal. Subject P stands with their back leaning against the support column 13, and standing imaging is performed as the stand 11 moves up and down. In standing mode, the top plate movement mechanism 37, described later, moves the top plate 30 to a position where it does not interfere with the stand under the control of the movement control circuit 27.

[0034] Figure 2 is a perspective view showing an example of the state of the rigging device 10 in standing mode. As shown in Figure 2, in this embodiment, in standing mode, a columnar subject holder (also called a patient fixing pole) 30a is present inside the rigging device 11 when the subject P is photographed in a standing position. The subject P can maintain a stable standing posture without swaying by lightly leaning their back against the patient fixing pole 30a.

[0035] Figure 3 is a perspective view showing an example of the state of the support device 10 in supine mode. As shown in Figure 3, in supine mode, the top plate 30 is supported on the base 35 in a horizontal position via the top plate movement mechanism 37. At this time, the top plate 30 can be freely moved along the long axis of the top plate 30 under the control of the movement control circuit 27.

[0036] The X-ray tube 17 is a vacuum tube that generates X-rays by irradiating thermionic electrons from the cathode (filament) to the anode (target) through the application of a high voltage from the high voltage generator 31 and the supply of filament current. X-rays are generated when thermionic electrons collide with the target. The X-rays generated at the tube's focal point in the X-ray tube 17 are shaped into a cone beam, for example, via a collimator, and irradiated onto the subject P.

[0037] For example, the X-ray tube 17 is a rotating anode type X-ray tube that generates X-rays by irradiating a rotating anode with thermionic electrons. In this embodiment, it can be applied to both single-tube type X-ray CT scanners and so-called multi-tube type X-ray CT scanners, in which multiple pairs of X-ray tubes 17 and X-ray detectors 19 are mounted on a rotating frame 21.

[0038] The X-ray detector 19 detects X-rays irradiated from the X-ray tube 17 and passed through the subject P, and outputs an electrical signal corresponding to the amount of X-rays to the DAS 33. The X-ray detector 19 has, for example, multiple arrays of detection elements arranged in the channel direction along a single arc centered on the focal point of the X-ray tube 17. The X-ray detector 19 has, for example, a structure in which multiple such arrays of detection elements are arranged in the slice direction (column direction, row direction).

[0039] The X-ray CT apparatus 1 includes a Rotate / Rotate-Type (third-generation CT) in which the X-ray tube 17 and X-ray detector 19 rotate together around the subject P, and a Stationary / Rotate-Type (fourth-generation CT) in which a large number of X-ray detection elements are fixed in a ring-shaped array, and only the X-ray tube 17 rotates around the subject P. Both types are applicable to this embodiment. To provide a more detailed explanation, the X-ray CT apparatus 1 of this embodiment will be described using a third-generation CT as an example.

[0040] Furthermore, the X-ray detector 19 is an indirect conversion type detector having, for example, a grid, a scintillator array, and a photosensor array. The scintillator array has multiple scintillators, and each scintillator has a scintillator crystal that outputs light in a quantity of photons corresponding to the amount of incident X-rays. The grid is positioned on the X-ray incident side of the scintillator array and has an X-ray shielding plate that has the function of absorbing scattered X-rays.

[0041] The grid is sometimes also called a collimator (one-dimensional collimator or two-dimensional collimator). The optical sensor array has the function of converting the amount of light from the scintillator into an electrical signal, and for example, it has optical sensors such as photomultipliers (PMTs).

[0042] The X-ray detector 19 may be a direct conversion type detector having a semiconductor element that converts incident X-rays into an electrical signal. Alternatively, the X-ray detector 19 may be a photon counting type X-ray detector.

[0043] The rotating frame 21 has an opening 15 and is fitted with an X-ray tube 17 that generates X-rays. Specifically, the rotating frame 21 is an annular frame that supports the X-ray tube 17 and the X-ray detector 19 opposite each other and rotates the X-ray tube 17 and the X-ray detector 19 by a stand control device 25, which will be described later.

[0044] The rotating frame 21 is rotatably supported on the main frame via support bearings. The rotating frame 21 receives power from the rotary drive unit 23 under the control of the frame control device 25 and rotates around the rotation axis A1 at a constant angular velocity.

[0045] The rotating frame 21 supports the X-ray tube 17 and X-ray detector 19, as well as a high-voltage generator 31 and DAS 33. This rotating frame 21 is housed in a substantially cylindrical casing with an opening 15 forming the imaging space. The central axis of the opening 15 coincides with the rotation axis A1 of the rotating frame 21.

[0046] The detection data generated by DAS33 is transmitted via optical communication from, for example, a transmitter having a light-emitting diode (LED) to a receiver having a photodiode located on the non-rotating part (e.g., the main frame) of the mounting device 10, and then transferred to the console device 100.

[0047] Furthermore, the method for transmitting detection data from the rotating frame 21 to the non-rotating portion of the mounting device 10 is not limited to the aforementioned optical communication; any non-contact data transmission method may be used.

[0048] The rotary drive unit 23 generates power to rotate the rotating frame 21 according to the control from the frame control device 25. The rotary drive unit 23 generates power by driving at a rotational speed corresponding to the duty cycle of the drive signal from the frame control device 25. The rotary drive unit 23 is implemented by a motor such as a direct drive motor or a servo motor. The rotary drive unit 23 is housed in the frame 11, for example.

[0049] The frame control device 25 controls the high-voltage generator 31, rotary drive device 23, movement control circuit 27, and DAS 33 according to commands from the console device 100. The frame control device 25 also has the function of receiving input signals from the console device 100 and input interfaces attached to the frame device 10 and controlling the operation of the frame device 10.

[0050] For example, the frame control device 25 receives an input signal and performs control to rotate the rotating frame 21, or to tilt the frame device 10. The frame control device 25 may be installed on the support column 13 of the frame device 10, or it may be installed on the console device 100. Furthermore, the functions realized by the frame control device 25 may be incorporated as a frame control function in the processing circuit 107 of the console device 100.

[0051] The rig control device 25 has, as hardware resources, a processing unit (processor) such as a CPU (Central Processing Unit) or MPU (Micro Processing Unit), and a storage device (memory) such as ROM (Read Only Memory) or RAM (Random Access Memory).

[0052] Furthermore, the rig control device 25 may be implemented using an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), another Complex Programmable Logic Device (CPLD), or a Simple Programmable Logic Device (SPLD).

[0053] The processing unit achieves the above function by reading the program stored in the memory device. Alternatively, instead of storing the program in the memory device, the processing unit may be configured to directly incorporate the program into its circuitry. In this case, the processing unit achieves the above function by reading and executing the program incorporated into its circuitry.

[0054] The top plate 30 is capable of supporting the subject P in supine mode and is insertable into the opening 15. The top plate 30 is supported by the base 35 via a top plate movement mechanism 37. Specifically, the top plate 30 is held by the top plate movement mechanism 37 provided at both ends of the base 35 in the Y-axis direction.

[0055] The top plate 30 is movable along the direction through which the opening 15 passes, via the top plate movement mechanism 37. In other words, the top plate 30 is fixed so as to be slidable relative to the mount 11 along the rotation axis A1 of the rotating frame 21 in the imaging system, via the top plate movement mechanism 37.

[0056] The tabletop moving mechanism 37 moves the tabletop 30 under the control of the movement control circuit 27.

[0057] The top plate moving mechanism 37 is composed of, for example, a roller guide. The top plate moving mechanism 37 can be implemented using a friction drive or a belt mechanism. However, the top plate moving mechanism 37 is not limited to roller guides, friction drives, belt mechanisms, etc., and can be implemented using any known mechanism as appropriate.

[0058] The top plate movement mechanism 37 may be mounted on the vertical movement mechanism. The vertical movement mechanism, for example, is mounted on the base 35 and incorporates the top plate movement mechanism 37. The vertical movement mechanism allows the top plate 30 to move in a direction perpendicular to the surface on which the subject P is placed.

[0059] For example, the vertical movement mechanism is realized by an actuator (e.g., a piston type) that moves (pushes up) the rotation axis of the roller guide along the Y-axis. However, the means of realizing the vertical movement mechanism are not limited to actuators.

[0060] Furthermore, a left-right movement mechanism may be provided between the top plate moving mechanism 37 and the top plate 30. For example, top plate support members covering the bottom surface and side surface of the top plate 30 are provided on the bottom surface and side surface of the top plate 30. The left-right movement mechanism includes a block, a ball screw, a motor, and a belt. The ball screw extends along the short axis direction of the top plate 30. The block is attached to the ball screw.

[0061] A top plate support member is connected to the block. The rotational force from the motor is transmitted to the ball screw via a belt. When the motor rotates under the control of the movement control circuit 27, the rotational force from the motor is transmitted to the ball screw. This causes the ball screw to rotate. As the ball screw rotates, the block moves along the short axis direction of the top plate 30.

[0062] The movement control circuit 27 controls the movement of the frame 11 and the top plate 30.

[0063] For example, when the user instructs the user to take an image of the subject P in an upright position, the movement control circuit 27 controls the stand movement mechanism 131 to rotate the stand 11 so that the aperture 15 is vertical.

[0064] Furthermore, for example, if the user instructs the camera to photograph the subject P in an upright position, the movement control circuit 27 controls the top plate movement mechanism 37 so that the top plate 30 is moved to a position where it does not interfere with the stand 11 even when the stand 11 moves along the vertical direction.

[0065] Furthermore, the base 35 may be equipped with a moving mechanism such as casters. In this case, the user may manually move the base 35 to retract the top plate 30, or the base 35 may be automatically moved by a drive source such as a motor to retract the top plate 30.

[0066] The movement control circuit 27 is implemented by the processor and other components described above.

[0067] In Figure 1, the movement control circuit 27 is mounted on the support column 13, but it may also be mounted on the frame 11 or on the console device 100. Furthermore, the functions realized by the movement control circuit 27 may be implemented as movement control functions in the processing circuit 107 or in the frame control device 25.

[0068] The control panel 29 is implemented using switch buttons, a touchpad for input operations by touching the operating surface, and a touch panel display that integrates the display screen and the touchpad. The control panel 29 converts the input operations received from the user into electrical signals and outputs them to the frame control device 25.

[0069] The control panel 29 accepts selection operations for selecting imaging protocols, such as a standing mode for imaging a subject P in an upright position, a seated mode for imaging a subject P in a seated position, or a supine mode for imaging a subject P in a prone position. The control panel 29 is provided, for example, on the support column 13.

[0070] The high-voltage generator 31 has an electrical circuit including a transformer and a rectifier, and generates the high voltage applied to the X-ray tube 17 and the filament current supplied to the X-ray tube 17. The high-voltage generator 31 also controls the output voltage according to the X-rays irradiated by the X-ray tube 17. The high-voltage generator 31 may be a transformer type or an inverter type.

[0071] The high-voltage generator 31 may be installed on the rotating frame 21, or it may be installed on the main frame side of the mounting base 11.

[0072] The wedge (not shown) is a filter for adjusting the amount of X-rays emitted from the X-ray tube 17. Specifically, the wedge is a filter that transmits and attenuates the X-rays emitted from the X-ray tube 17 so that the X-rays emitted from the X-ray tube 17 to the subject P have a predetermined distribution.

[0073] A wedge is, for example, a wedge filter or bow-tie filter, which is a filter made of aluminum that has been processed to have a predetermined target angle or thickness.

[0074] A collimator (not shown) is a lead plate or the like used to focus the X-rays that have passed through the wedge into the X-ray irradiation area, and a slit is formed by combining multiple lead plates or the like.

[0075] The DAS33 includes an amplifier that amplifies the electrical signals output from each X-ray detection element of the X-ray detector 19, and an A / D converter that converts the electrical signals into digital signals, thereby generating detection data. The detection data generated by the DAS33 is transferred to the console device 100. Here, the detection data collected by irradiating the subject P with X-rays is an example of first detection data.

[0076] The console device 100 includes a memory 101, a display 103, an input interface 105, and a processing circuit 107. Data communication between the memory 101, the display 103, the input interface 105, and the processing circuit 107 is performed, for example, via a bus (BUS).

[0077] Memory 101 is a storage device such as an HDD (Hard Disk Drive), SSD (Solid State Drive), or integrated circuit storage device that stores various types of information. For example, memory 101 stores parameter information 1011, which will be described later. Also, for example, memory 101 stores projection data and reconstructed image data.

[0078] Memory 101 may also be a drive device that reads and writes various information to portable storage media such as CDs (Compact Discs), DVDs (Digital Versatile Discs), and flash memory, as well as semiconductor memory elements such as RAM (Random Access Memory), in addition to HDDs and SSDs.

[0079] Furthermore, the storage area of ​​memory 101 may be located within the console device 100 or in an external storage device connected via a network. Memory 101 also stores the control program according to this embodiment. Memory 101 also stores volume data generated by pre-scan and main scans.

[0080] The display 103 displays various types of information. For example, the display 103 outputs medical images (CT images) generated by the processing circuit 107, and a GUI (Graphical User Interface) for receiving various operations from the user.

[0081] As the display 103, for example, a liquid crystal display (LCD), a cathode ray tube (CRT) display, an organic electroluminescent display (OELD), a plasma display, or any other display can be used as appropriate.

[0082] The display 103 may also be mounted on the mounting device 10. Furthermore, the display 103 may be a desktop type, or it may consist of a tablet terminal or the like that can communicate wirelessly with the console device 100. The display 103 corresponds to the display unit.

[0083] The input interface 105 receives various input operations from the user, converts the received input operations into electrical signals, and outputs them to the processing circuit 107. For example, the input interface 105 receives from the user the acquisition conditions when acquiring projection data, the reconstruction conditions when reconstructing CT images, and the image processing conditions when generating post-processed images from CT images.

[0084] The input interface 105 can, for example, be a mouse, keyboard, trackball, switch, button, joystick, touchpad, or touch panel display, as appropriate.

[0085] In this embodiment, the input interface 105 is not limited to those comprising physical operating components such as a mouse, keyboard, trackball, switch, button, joystick, touchpad, and touch panel display.

[0086] For example, an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device located separately from the device, and outputs this electrical signal to a processing circuit 44, is also an example of an input interface 105.

[0087] Furthermore, the input interface 105 may be provided on the mounting device 10. Also, the input interface 43 may consist of the console device 100 main unit and a tablet terminal or the like capable of wireless communication. The input interface 105 corresponds to the input section.

[0088] The processing circuit 107 controls the operation of the entire X-ray CT apparatus 1 in accordance with the electrical signals of input operations output from the input interface 105. For example, the processing circuit 107 has hardware resources such as a processor (CPU, MPU, GPU - Graphics Processing Unit) and memory (ROM, RAM, etc.).

[0089] The processing circuit 107 executes system control functions 111, parameter calculation functions 113, determination functions 115, preprocessing functions 117, reconstruction functions 119, and image processing functions 121 using a processor that executes a program loaded into memory.

[0090] Here, the system control function 111 is an example of a reception unit. The parameter calculation function 113 is an example of a calculation unit and memory control unit. The determination function 115 is an example of a specification unit and determination unit. The reconstruction function 119 is an example of a generation unit.

[0091] Furthermore, the system control function 111, parameter calculation function 113, determination function 115, preprocessing function 117, reconstruction function 119, and image processing function 121 are not limited to being implemented by a single processing circuit. Multiple independent processors may be combined to form a processing circuit, and each processor may execute a program to implement the system control function 111, preprocessing function 117, reconstruction function 119, and image processing function 121, respectively.

[0092] The system control function 111 controls each function of the processing circuit 107 based on input operations received from the user via the input interface 105.

[0093] Specifically, the system control function 111 reads the control program stored in memory 101, loads it onto the memory within the processing circuit 107, and controls each part of the X-ray CT apparatus 1 according to the loaded control program. For example, the system control function 111 controls each function of the processing circuit 107 based on input operations received from the user via the input interface 105.

[0094] In this embodiment, the input operation includes the selection of the shooting protocol. The shooting protocol also includes information indicating whether the shooting mode is standing mode or supine mode. The shooting mode is an example of posture information and is also an example of mount status information.

[0095] The parameter calculation function 113 calculates image quality adjustment parameters to be used in the reconstruction process for each shooting mode. For example, the parameter calculation function 113 performs a scan of the phantom in both the standing mode and the lying mode.

[0096] The parameter calculation function 113 calculates the correction data and X-ray tube alignment (alignment correction value) included in the image quality adjustment parameters for both the standing and supine modes, based on the detection data (hereinafter also referred to as raw data) obtained from the phantom scan. In this case, the raw data is an example of the second detection data.

[0097] Correction data is data used to correct the image quality of the reconstructed image based on the pixel values ​​of water and air. For example, correction data is calculated from the difference between the CT values ​​of water and air calculated from the raw data obtained by scanning a phantom containing water and air, and the ideal CT values ​​of water and air. Correction data is calculated for water and air separately, for each X-ray CT device.

[0098] The alignment correction value is data that corrects the effect of the difference between the position of the X-ray tube 17 relative to the X-ray detector 19 in the design (hereinafter also referred to as the design position) and the position of the X-ray tube 17 relative to the X-ray detector 19 in the actual installation (hereinafter also referred to as the actual position) on the reconstructed image.

[0099] For example, the alignment correction value is calculated from the difference between the raw data obtained by scanning the phantom and the raw data that would be expected to be obtained if the X-ray tube 17 were positioned in the design location. The alignment correction value is calculated for both the anterior-posterior and lateral directions for each X-ray CT device 1.

[0100] Furthermore, the parameter calculation function 113 sets (presets) the image quality parameters included in the image quality adjustment parameters for both the standing mode and the lying mode.

[0101] Image quality parameters are a set of various parameters that determine the image quality of the reconstructed image. Examples of image quality parameters include brightness and contrast (or methods for adjusting brightness and contrast). Image quality parameters are preset for each X-ray CT scanner. Alternatively, image quality parameters may be preset for each user-specified image quality.

[0102] Here, the effect of gravity on the X-ray tube 17 and X-ray detector 19 inside the stand 11 differs depending on whether the image is taken in supine mode or standing mode, which may result in differences in the raw data.

[0103] Therefore, even if imaging is performed using the same X-ray CT scanner 1 under the same imaging conditions except for the imaging mode, and reconstruction processing is performed using the same image quality adjustment parameters, differences in image quality (such as shifts in CT values ​​or the occurrence of noise) may occur depending on whether the imaging mode is standing or supine. In other words, depending on the imaging mode, it may not be possible to obtain a reconstructed image with the image quality desired by the user.

[0104] Therefore, the X-ray CT apparatus 1 according to this embodiment calculates and stores image quality adjustment parameters for each shooting mode, and reduces the difference in image quality caused by differences in shooting modes by using image quality adjustment parameters corresponding to the shooting mode.

[0105] Here, Figure 4 illustrates an example of the calculation process for image quality adjustment parameters in supine mode. As shown in Figure 4, the system control function 111 controls each function of the processing circuit 107 and performs a scan of the phantom F in supine mode to collect raw data RDL1. Note that in Figure 4, a phantom F shaped like a human is scanned in supine mode, but the shape of the phantom F scanned in supine mode is not limited to a human shape.

[0106] Next, the parameter calculation function 113 calculates correction data and alignment correction values ​​as image quality adjustment parameters PL for supine mode, based on the raw data RDL1 collected by scanning the Phantom F in supine mode. Furthermore, the parameter calculation function 113 presets the image quality parameters corresponding to supine mode as image quality adjustment parameters PL for supine mode.

[0107] Furthermore, the parameter calculation function 113 associates information indicating that the shooting mode is supine mode with the calculated or preset image quality adjustment parameter PL and stores it in the parameter information 1011 of the memory 101.

[0108] Figure 5 illustrates an example of the calculation process for image quality adjustment parameters in standing mode. As shown in Figure 5, the system control function 111 controls each function of the processing circuit 107 to perform a scan of the phantom F in standing mode and collect raw data RDS1. In Figure 5, a phantom F shaped like a human is scanned in standing mode, but the shape of the phantom F scanned in standing mode is not limited to a human shape.

[0109] Next, the parameter calculation function 113 calculates correction data and alignment correction values ​​as image quality adjustment parameters PS for the standing mode, based on the raw data RDS1 collected by scanning the Phantom F in standing mode. Furthermore, the parameter calculation function 113 presets the image quality parameters corresponding to the standing mode as image quality adjustment parameters PS for the standing mode.

[0110] Furthermore, the parameter calculation function 113 associates information indicating that the shooting mode is standing mode with the calculated or preset image quality adjustment parameter PS and stores it in the parameter information 1011 of the memory 101.

[0111] Returning to Figure 1, let's continue the explanation. The decision function 115 determines the image quality adjustment parameters to be used in the reconstruction process based on the subject P's imaging posture.

[0112] For example, the decision function 115 identifies whether the shooting mode included in the shooting protocol selected by the system control function 111 is an upright mode or a supine mode. The decision function 115 refers to the parameter information 1011 in the memory 101 and determines the image quality adjustment parameters associated with the identified shooting mode as image quality adjustment parameters to be used in the reconstruction process.

[0113] For example, the preprocessing function 117 generates data that has been preprocessed by logarithmic transformation, offset correction, inter-channel sensitivity correction, beam hardening correction, and other processes applied to the raw data output from the DAS33. The preprocessed data is also called projection data.

[0114] The reconstruction function 119 performs a reconstruction process on the projection data to generate a reconstructed image.

[0115] For example, the reconstruction function 119 performs a process on the projection data generated by the preprocessing function 117 to correct the effect of the difference between the design position and the actual position on the reconstructed image.

[0116] Specifically, the reconstruction function 119 generates corrected projection data that corrects the effect of the difference between the design position and the actual position on the reconstructed image, based on the projection data generated by the preprocessing function 117 and the alignment correction value included in the image quality adjustment parameters determined by the determination function 115. Note that the process of correcting the effect of the difference between the design position and the actual position on the reconstructed image may also be performed by the preprocessing function 117.

[0117] Furthermore, the reconstruction function 119 generates CT image data by performing reconstruction processing on the corrected projection data using methods such as filtered back projection (FBP) and iterative reconstruction. In other words, the reconstruction function 119 generates a reconstructed image based on the output from the imaging system.

[0118] Furthermore, for example, the reconstruction function 119 performs a process to correct the pixel value of each pixel on the reconstructed image.

[0119] Specifically, the reconstruction function 119 performs a process to correct the pixel value of each pixel on the reconstructed image based on the correction data and image quality parameters included in the image quality adjustment parameters determined by the determination function 115. Note that the above process of correcting the pixel value of each pixel on the reconstructed image may also be performed by the image processing function 121, which will be described later.

[0120] The reconstruction function 119 stores the data of the reconstructed image, in which the pixel values ​​of each pixel on the reconstructed image have been corrected, in the memory 101.

[0121] The image processing function 121 applies various image processing to the CT image reconstructed by the reconstruction function 119. For example, the image processing function 121 generates a display image by applying 3D image processing such as volume rendering, surface volume rendering, image value projection processing, MPR (Multi-Planer Reconstruction) processing, and CPR (Curved MPR) processing to the CT image.

[0122] Here, Figure 6 illustrates an example of determining image quality adjustment parameters in supine mode and the reconstruction process applying the determined image quality adjustment parameters. First, the determination function 115 identifies that the shooting mode is supine mode from the shooting protocol selected by the system control function 111.

[0123] Furthermore, as shown in Figure 6, the system control function 111 controls each function of the processing circuit 107 and performs a scan of the subject P in supine mode to collect raw data RDL2. The preprocessing function 117 generates projection data of the subject P scanned in supine mode based on the raw data RDL2.

[0124] The reconstruction function 119 uses the correction data, alignment correction values, and image quality parameters included in the image quality adjustment parameters determined by the determination function 115 to perform a reconstruction process on the projection data and generate a reconstructed image IL.

[0125] Figure 7 illustrates an example of determining image quality adjustment parameters in standing mode and the reconstruction process applying the determined image quality adjustment parameters. First, the determination function 115 identifies that the shooting mode is standing mode from the shooting protocol selected by the system control function 111.

[0126] Furthermore, as shown in Figure 7, the system control function 111 controls each function of the processing circuit 107 and performs a scan of the subject P in standing mode to collect raw data RDS2. The preprocessing function 117 generates projection data of the subject P scanned in standing mode based on the raw data RDS2.

[0127] The reconstruction function 119 uses the correction data, alignment correction values, and image quality parameters included in the image quality adjustment parameters determined by the determination function 115 to perform reconstruction processing on the projection data and generate a reconstructed image IS.

[0128] The following describes the processes performed by the X-ray CT apparatus 1 according to this embodiment. First, the calculation and storage process of image quality adjustment parameters will be described. Figure 8 is a flowchart showing an example of the calculation and storage process of image quality adjustment parameters performed by the X-ray CT apparatus 1 according to this embodiment. As an example, the calculation and storage process of image quality adjustment parameters is performed when the X-ray CT apparatus 1 is installed or during maintenance work.

[0129] First, the system control function 111 collects raw data for calculating image quality adjustment parameters in supine mode (step S1). For example, the system control function 111 controls each function of the processing circuit 107 to perform a scan of the phantom F in supine mode and collects raw data for calculating image quality adjustment parameters in supine mode.

[0130] Next, the parameter calculation function 113 calculates the image quality adjustment parameters for the supine mode (step S2).

[0131] For example, the parameter calculation function 113 calculates correction data and alignment correction values ​​as image quality adjustment parameters for the supine mode based on the raw data for calculating image quality adjustment parameters for the supine mode collected in step S1. The parameter calculation function 113 also presets image quality parameters corresponding to the supine mode as image quality adjustment parameters for the supine mode.

[0132] Next, the parameter calculation function 113 stores the image quality adjustment parameters for the supine mode (step S3). For example, the parameter calculation function 113 associates the information indicating that the shooting mode is supine mode with the image quality adjustment parameters calculated in step S2 and stores them in the parameter information 1011 of the memory 101.

[0133] Next, the system control function 111 collects raw data for calculating image quality adjustment parameters in standing mode (step S4). For example, the system control function 111 controls each function of the processing circuit 107 to perform a scan of the phantom F in standing mode and collects raw data for calculating image quality adjustment parameters in standing mode.

[0134] Next, the parameter calculation function 113 calculates the image quality adjustment parameters for the standing mode (step S5).

[0135] For example, the parameter calculation function 113 calculates correction data and alignment correction values ​​as image quality adjustment parameters for the standing mode based on the raw data for calculating image quality adjustment parameters for the standing mode collected in step S4. The parameter calculation function 113 also presets image quality parameters corresponding to the standing mode as image quality adjustment parameters for the standing mode.

[0136] Next, the parameter calculation function 113 stores the image quality adjustment parameters for the standing mode (step S6) and terminates this process. For example, the parameter calculation function 113 associates the information indicating that the shooting mode is standing mode with the image quality adjustment parameters calculated in step S5 and stores them in the parameter information 1011 of the memory 101.

[0137] Furthermore, the series of processes in steps S4 to S6 may be executed first, followed by the series of processes in steps S1 to S3. Alternatively, the series of processes in steps S1 to S3 and the series of processes in steps S4 to S6 may be executed on separate occasions.

[0138] Next, the process of determining and reconstructing image quality adjustment parameters will be described. Figure 9 is a flowchart showing an example of the process of determining and reconstructing image quality adjustment parameters performed by the X-ray CT apparatus 1 according to this embodiment.

[0139] First, the system control function 111 receives input from the user to select a shooting protocol (step S11). The shooting protocol includes information indicating whether the shooting mode is supine mode or standing mode.

[0140] Next, the determination function 115 identifies the imaging mode of the subject P (step S12). For example, the determination function 115 identifies the imaging mode of the subject P from information indicating whether the imaging mode included in the imaging protocol received in step S11 is a supine mode or an upright mode. Next, the determination function 115 determines whether the identified imaging mode is a supine mode or an upright mode (step S13).

[0141] If the shooting mode is supine mode (step S13: Yes), the determination function 115 refers to the parameter information 1011 in memory 101 and determines the image quality adjustment parameters associated with supine mode as image quality adjustment parameters to be used in the reconstruction process (step S14).

[0142] Next, the system control function 111 collects raw data of the subject P in supine mode (step S15). For example, the system control function 111 controls each function of the processing circuit 107 and performs a scan of the subject P in supine mode to collect raw data.

[0143] Next, the preprocessing function 117 generates projection data (step S16). For example, the preprocessing function 117 generates projection data by applying preprocessing such as logarithmic transformation, offset correction, inter-channel sensitivity correction, and beam hardening correction to the raw data collected in step S15.

[0144] Next, the reconstruction function 119 performs reconstruction processing using the image quality adjustment parameters for the supine mode (step S17). For example, the reconstruction function 119 performs reconstruction processing on the projection data generated in step S16, including various corrections using the image quality adjustment parameters for the standing mode determined in step S15, to generate a reconstructed image. After step S17, the process proceeds to step S22, which will be described later.

[0145] On the other hand, if the shooting mode is standing mode (step S13: No), the determination function 115 refers to the parameter information 1011 in the memory 101 and determines the image quality adjustment parameters associated with the standing mode as image quality adjustment parameters to be used in the reconstruction process (step S18).

[0146] Next, the system control function 111 collects raw data of the subject P in standing mode (step S19). For example, the system control function 111 controls each function of the processing circuit 107 and performs a scan of the subject P in standing mode to collect raw data.

[0147] Next, the preprocessing function 117 generates projection data (step S20). For example, the preprocessing function 117 generates projection data by applying preprocessing such as logarithmic transformation, offset correction, inter-channel sensitivity correction, and beam hardening correction to the raw data collected in step S19.

[0148] Next, the reconstruction function 119 performs reconstruction processing using the image quality adjustment parameters for the standing mode (step S21). For example, the reconstruction function 119 performs reconstruction processing on the projection data generated in step S20, including various correction processes using the image quality adjustment parameters for the standing mode determined in step S18, to generate a reconstructed image.

[0149] Next, the image processing function 121 generates a display image (step S22) and terminates the process. For example, the image processing function 121 generates a display image by applying the above-described 3D image processing to the reconstructed image generated in step S21.

[0150] As described above, the X-ray CT apparatus 1 according to this embodiment identifies the orientation of the cradle 11 having an opening 15 into which the subject P is inserted, determines image quality adjustment parameters to be used for reconstruction processing based on the identified orientation of the cradle 11 and parameter information 1011 that stores the orientation of the cradle 11 in association with image quality adjustment parameters, and performs reconstruction processing on the raw data using the determined image quality adjustment parameters to generate a reconstructed image.

[0151] Here, for example, if the reconstruction process is performed using the same image quality adjustment parameters regardless of the orientation of the gantry 11, the effect of gravity on the units within the gantry 11 (X-ray tube 17 and X-ray detector 19) differs depending on the orientation of the gantry 11, which may result in differences in the image quality of the reconstructed image produced by the reconstruction process. In contrast, the X-ray CT apparatus 1 according to this embodiment can perform the reconstruction process using image quality adjustment parameters corresponding to the orientation of the gantry 11 (for example, supine mode or standing mode). As a result, the X-ray CT apparatus 1 according to this embodiment can reduce differences in the image quality of CT images caused by differences in the imaging posture of the subject P.

[0152] The above-described embodiment can also be modified and implemented as appropriate by changing some of the configuration or functions of the X-ray CT apparatus 1. Therefore, the following describes modified examples of the above-described embodiment as other embodiments. In the following, we will mainly describe the differences from the above-described embodiment, and will omit detailed explanations of points that are common with what has already been described. Furthermore, the modified examples described below may be implemented individually or in combination as appropriate.

[0153] (Variation 1) In the embodiments described above, when the subject P is in a seated position, the method for determining image quality adjustment parameters and performing reconstruction processing was described, assuming that the shooting mode is the standing mode, similar to when the subject P is in a standing position. In this modification, an embodiment is described in which image quality adjustment parameters for a seated shooting state (also called seated mode) are calculated and stored, and when the subject P is in a seated position, reconstruction processing is performed using the image quality adjustment parameters corresponding to the seated mode.

[0154] In this modified example, the system control function 111 performs a scan of the Phantom F in sitting mode, in addition to standing and lying modes, when calculating image quality adjustment parameters. The parameter calculation function 113 calculates (correction data and alignment correction values) or presets (image quality parameters) image quality adjustment parameters for sitting mode based on the raw data obtained from the Phantom F scan in sitting mode.

[0155] The parameter calculation function 113 associates information indicating that the shooting mode is seated mode with the calculated image quality adjustment parameters for seated mode and stores them in the parameter information 1011 of the memory 101.

[0156] In this modified example, the imaging protocol includes information indicating whether the imaging mode is supine, standing, or sitting. If the imaging mode included in the imaging protocol received by the system control function 111 is sitting mode, the determination function 115 refers to the parameter information 1011 in memory 101 and determines the image quality adjustment parameters associated with sitting mode as the image quality adjustment parameters to be used in the reconstruction process.

[0157] In this modified version, when the subject P is in a seated position, image quality adjustment parameters calculated based on raw data obtained by scanning the phantom F in seated mode can be used in the reconstruction process, which are different from the image quality adjustment parameters corresponding to the standing mode. In other words, according to this modified version, the difference in CT image quality caused by differences in the subject P's scanning position can be further reduced.

[0158] (Modification 2) In the embodiments described above, the following configurations were described: the imaging posture being supine (the mounting surface of the support column 13 and the body axis of the subject P are parallel) and standing or sitting (the mounting surface of the support column 13 and the body axis of the subject P are perpendicular). In this modified example, a configuration is described in which the subject P can be imaged by setting the angle between the mounting surface of the support column 13 and the body axis of the subject P to any angle between 90° (the mounting surface of the support column 13 and the body axis of the subject P are perpendicular) and 180° (the mounting surface of the support column 13 and the body axis of the subject P are parallel).

[0159] In this modified example, the top plate movement mechanism 37 has a mechanism that allows the angle of the support column 13 on the top plate 30's surface relative to the installation surface to be changed to any angle between 90° and 180°. The system control function 111 in this modified example accepts input from the user for the desired angle of the support column 13 of the top plate 30 relative to the installation surface (hereinafter also referred to as the top plate angle). As an example, the system control function 111 accepts input for any angle between 90° and 180° in 5° increments.

[0160] In this modified example, the movement control circuit 27 controls the angle of the support column 13 of the top plate 30 with respect to the installation surface (hereinafter also referred to as the angle of the top plate) to any angle between 90° and 180° desired by the user.

[0161] Furthermore, when the angle of the top plate 30 is changed to any angle between 90° and 180° desired by the user, the movement control circuit 27 rotates the frame 11 so that the opening 15 is perpendicular to the surface on which the subject P is placed on the top plate 30.

[0162] In this modified version, the system control function 111 performs a scan of the Phantom F for each angle of the top panel (in this modified version, every 5° from 90° to 180°) when calculating the image quality adjustment parameters. The parameter calculation function 113 calculates the image quality adjustment parameters for each angle of the top panel (correction data and alignment correction values) or presets (image quality parameters) based on the raw data obtained from the Phantom F scan for each angle of the top panel.

[0163] The parameter calculation function 113 associates information representing the angle of the tabletop with the calculated image quality adjustment parameters for the seating mode and stores them in the parameter information 1011 of the memory 101.

[0164] In this modified example, the shooting protocol includes information representing the angle of the top plate. The determination function 115 refers to the parameter information 1011 in the memory 101 and determines the image quality adjustment parameters associated with the angle of the top plate included in the shooting protocol received by the system control function 111 as image quality adjustment parameters to be used in the reconstruction process.

[0165] The parameter calculation function 113 may calculate image quality adjustment parameters for each top panel angle based on raw data collected at a predetermined number of top panel angles. For example, the system control function 111 may perform scans of the Phantom F for top panel angles of 90°, 135°, and 180°, respectively.

[0166] In this case, the parameter calculation function 113 may predict the image quality adjustment parameters for each angle of the top panel, from 90° to 135° and from 135° to 180°, based on the calculation results of the respective image quality adjustment parameters for when the top panel angle is 90°, 135°, and 180°.

[0167] In this way, by calculating image quality adjustment parameters for each angle of the top panel based on raw data collected at multiple predetermined angles of the top panel, it becomes unnecessary to collect raw data at all angles, thereby reducing the processing burden of calculating and storing image quality adjustment parameters.

[0168] In this modified version, image quality adjustment parameters corresponding to the angle of the tabletop used to image the subject P can be used in the reconstruction process. In other words, according to this modified version, differences in CT image quality caused by differences in the imaging posture of the subject P can be further reduced.

[0169] (Variation 3) In the embodiment described above, the parameter calculation function 113 was described in which it calculates correction data for water and air separately for each shooting mode. However, the parameter calculation function 113 may calculate correction data for only one of water or air for each shooting mode.

[0170] For example, the parameter calculation function 113 may calculate correction data for each shooting mode for water only, and for air only for the supine mode (or standing mode). In this case, the reconstruction function 119 may perform reconstruction using common correction data for air.

[0171] Alternatively, for example, the parameter calculation function 113 may calculate correction data for each shooting mode only for air, and for water, it may calculate correction data only for the supine mode (or standing mode). In this case, the reconstruction function 119 may perform reconstruction using common correction data for water.

[0172] According to this modified version, the processing burden related to the calculation of image quality parameters can be reduced.

[0173] (Modification 4) In the embodiment described above, the parameter calculation function 113 was described in a form in which it calculates image quality adjustment parameters for each of the supine and standing modes based on raw data obtained by scanning the phantom F in both supine and standing modes. In this modified example, a form is described in which the image quality adjustment parameters for each of the supine and standing modes are calculated based on raw data obtained by scanning the phantom F in either supine or standing mode.

[0174] In this modified version, when calculating the image quality adjustment parameters, the system control function 111 scans the Phantom F only in supine mode to collect raw data. The parameter calculation function 113 calculates the image quality adjustment parameters for supine mode based on the collected raw data.

[0175] Here, when the imaging mode changes from supine mode to standing mode, it is possible to predict by calculation how the state of the units within the rig 11 (such as the X-ray tube 17 and X-ray detector 19) will change (how the position of the units will change due to the effect of gravity).

[0176] The parameter calculation function 113 predicts the changes in the CT values ​​of water and air, and the changes in the position of the X-ray tube 17 relative to the X-ray detector 19, when the imaging mode changes from supine mode to standing mode, based on the predicted changes in the state of the units within the gantry 11. Based on the predicted results of the changes in the CT values ​​of water and air and the changes in the position of the X-ray tube 17 relative to the X-ray detector 19, the parameter calculation function 113 calculates the correction data and alignment correction values ​​for the standing mode.

[0177] The system control function 111 may also perform a scan of the Phantom F and collect raw data only in standing mode.

[0178] According to this modified version, the processing burden of collecting raw data when calculating image quality adjustment parameters can be reduced.

[0179] (Variation 5) In the embodiment described above, the configuration described was one in which the object other than the subject P present in the opening 15 of the stand 11 during imaging was either the top plate 30 or the patient fixing pole 30a. In this modified example, a configuration is described in which the image quality adjustment parameters are switched depending on the substance other than the subject P that is inserted into the opening 15 of the stand 11, other than the top plate 30 or the patient fixing pole 30a.

[0180] In this modified example, when imaging subject P in supine mode, an angio table may be used in addition to the tabletop 30 (CT table). Note that the above is just one example of the type of table used for imaging subject P in supine mode, and other types of tables (tabletops) may be used for imaging subject P.

[0181] Here, for example, in a system capable of both Angio-CT imaging (Angio-CT mode) and normal CT imaging (Normal-CT mode), the objects present in the X-ray tube path (between the X-ray tube 17 and the X-ray detector 19) will differ between the Angio-CT mode and the Normal-CT mode, specifically between the Angio-CT table and the tabletop 30.

[0182] Even if the same system is used and the same imaging conditions are applied to subject P, differences in the objects present in the X-ray path may result in different image quality of the CT images obtained.

[0183] Therefore, in this modified example, the system control function 111 performs a scan of Phantom F for each type of object present in the X-ray tube path and the shooting mode when calculating the image quality adjustment parameters.

[0184] The parameter calculation function 113 calculates image quality adjustment parameters (correction data and alignment correction values) or presets (image quality parameters) for each type of object present in the X-ray tube path, based on raw data obtained from scanning Phantom F for each type of object present in the X-ray tube path and the shooting mode.

[0185] The parameter calculation function 113 associates information representing the shooting mode, information representing the type of object present in the X-ray tube path, and the calculated image quality adjustment parameters, and stores them in the parameter information 1011 of the memory 101.

[0186] In this modified example, the imaging protocol includes information representing the types of objects present in the X-ray tube path. Examples of this information include object information and rigging status information. The determination function 115 refers to the parameter information 1011 in the memory 101 and determines the image quality adjustment parameters associated with the combination of imaging mode and the types of objects present in the X-ray tube path included in the imaging protocol received by the system control function 111, as image quality adjustment parameters to be used in the reconstruction process.

[0187] Note that there may be multiple objects in the X-ray tube path. Furthermore, the objects in the X-ray tube path may include clothing and intravenous tubes worn by the subject P.

[0188] According to this modified version, it is possible to reduce the differences in CT image quality caused by differences in the types of objects present in the X-ray tube path.

[0189] (Experimental variation 6) In the embodiments described above, a configuration in which the reconstruction process is performed on the console device 100 was explained. In this modification, an example in which the reconstruction process is performed on an external image processing device different from the console device 100 is described.

[0190] In this modified example, the processing circuit of the external image processing device has a parameter calculation function 113, a determination function 115, a preprocessing function 117, a reconstruction function 119, and an image processing function 121.

[0191] The system control function 111 of this modified version associates the collected raw data with information representing the scan target (for example, information indicating whether it is a phantom F or a subject P) and information indicating whether the scanning mode is supine mode or standing mode, and transmits this information to an image processing device connected to the X-ray CT device 1 via a network.

[0192] The parameter calculation function 113 of the image processing device identifies the imaging mode from the raw data obtained by scanning the phantom F transmitted from the X-ray CT device 1, and from the information associated with it, which indicates whether the imaging mode is supine or standing.

[0193] The parameter calculation function 113 calculates image quality adjustment parameters for the supine mode and the standing mode, respectively, and stores them in the parameter information 1011 of the image processing device's memory, in association with information indicating whether the shooting mode is supine mode or standing mode.

[0194] The determination function 115 identifies the imaging mode from information indicating whether the imaging mode is supine or standing, which is associated with the raw data obtained by scanning the subject P transmitted from the X-ray CT device 1. The determination function 115 refers to the parameter information 1011 in memory and determines the image quality adjustment parameters corresponding to the identified imaging mode as image quality adjustment parameters to be used in the reconstruction process.

[0195] The processing of the preprocessing function 117, the reconstruction function 119, and the image processing function 121 is the same as in the embodiment described above, so a description will be omitted.

[0196] According to this modified example, the processing load on the console device 100 can be reduced.

[0197] According to at least one embodiment, modification, etc., described above, it is possible to reduce the difference in CT image quality caused by differences in the subject's posture during imaging.

[0198] While several embodiments have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be implemented in a variety of other forms, and various omissions, substitutions, modifications, and combinations of embodiments are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0199] 1 X-ray CT device 10. Mounting device 11. Gantry 13 Posts 15 Aperture 17 X-ray tube 19 X-ray detector 21 rotation frames 23 Rotary drive device 25. Mounting device 27. Movement control circuit 29. Control Panel 30 Top plate 31 High-voltage generator 33 DAS (Data Acquisition System) 35 base 37. Tabletop moving mechanism 100 Console Devices 101 memory 103 displays 105 Input Interfaces 107 Processing Circuit 111 System control function 113 Parameter calculation function 115 Decision Function 117 Pre-processing function 119 Reconfiguration function 121 Image Processing Functions 131 Mounting mechanism

Claims

1. A specification unit that identifies a stand state information representing the state of the stand, which includes at least one of posture information representing the orientation of the stand having an opening and object information representing objects other than the subject present in the opening, A determination unit determines the image quality adjustment parameters to be used in the reconstruction process based on the identified mount state information and parameter information that associates the mount state information with image quality adjustment parameters consisting of a plurality of parameters that determine the image quality of the reconstructed image generated by the reconstruction process. A generation unit that performs reconstruction processing on first detection data collected by irradiating the subject with X-rays using determined image quality adjustment parameters and generates a reconstructed image, An X-ray CT scanner equipped with [a specific feature].

2. The image quality adjustment parameter includes at least one of the following: correction data that adjusts the image quality of the reconstructed image based on the pixel values ​​of water and air; alignment correction value that represents the difference between the designed position and the actual position of the X-ray tube installed in the gantry; and image quality parameters, which are a set of parameters that determine the image quality of the reconstructed image. The X-ray CT apparatus according to claim 1.

3. The aforementioned mounting frame status information includes the aforementioned attitude information. A calculation unit calculates at least one of the correction data and the alignment correction value based on second detection data collected by irradiating the phantom with X-rays for each orientation of the mount, The system further includes a storage control unit that uses at least one of the calculated correction data and the alignment correction value as the image quality adjustment parameter, and stores it in the parameter information in association with the attitude information representing the attitude of the mount from which the second detection data was collected. The X-ray CT apparatus according to claim 2.

4. The memory control unit stores the image quality parameters as image quality parameters and associates them with the posture information representing the posture of the frame for each posture of the frame in the parameter information. The X-ray CT apparatus according to claim 3.

5. The posture information includes a supine mode representing the posture of the stand when photographing the subject in a supine position, and an upright mode representing the posture of the stand when photographing the subject in an upright position. The X-ray CT apparatus according to claim 3.

6. The calculation unit performs the following processes: calculating image quality parameters associated with other posture information, including the standing mode, based on the image quality parameters associated with the supine mode; or calculating image quality parameters associated with other posture information, including the supine mode, based on the image quality parameters associated with the standing mode. The X-ray CT apparatus according to claim 5.

7. The system further includes a reception unit that receives input for an imaging protocol including at least imaging conditions for imaging the subject and information on the status of the stand, The specified unit identifies the mount status information based on the received shooting protocol. The X-ray CT apparatus according to any one of claims 1 to 6.

8. The aforementioned frame status information includes the object information, The object includes a top plate on which the subject is placed when lying down during imaging, and a columnar subject holder that supports the subject when standing during imaging. The X-ray CT apparatus according to any one of claims 1 to 6.

9. The aforementioned X-ray CT apparatus is capable of performing angio-CT imaging of the subject, The object further includes an angio-CT table on which the subject is placed during angio-CT imaging of the subject. The X-ray CT apparatus according to claim 8.

10. An image processing method for performing reconstruction processing based on detection data collected by an X-ray CT scanner, Identify a stand state information that represents the state of the stand, which includes at least one of the following: posture information representing the orientation of the stand having an opening into which a subject is inserted, and object information representing objects other than the subject present in the opening. Based on the identified mount state information and parameter information that associates the mount state information with image quality adjustment parameters consisting of multiple parameters that determine the image quality of the reconstructed image generated by the reconstruction process, the image quality adjustment parameters to be used in the reconstruction process are determined. The first detection data collected by irradiating the subject with X-rays using the determined image quality adjustment parameters is subjected to reconstruction processing to generate a reconstructed image. Image processing methods.

Images