X-ray CT scanner and information processing method

Abstract

In an X-ray CT scanner capable of imaging subjects in at least supine and standing positions, calculations related to VolumeEC should be performed under conditions appropriate to the state of the gantry. [Solution] The information processing device according to this embodiment comprises a specification unit, a determination unit, a calculation unit, and an adjustment unit. The specification unit specifies stand state information representing the state of a stand having an aperture. The determination unit determines the VolumeEC parameters to be used in the VolumeEC calculation based on the specified stand state information and parameter information that stores the stand state information in association with VolumeEC parameters for performing calculations related to VolumeEC, which is a function for adjusting the X-ray irradiation conditions for a subject. The calculation unit performs calculations related to VolumeEC using the determined VolumeEC parameters. The adjustment unit adjusts the X-ray irradiation conditions based on the calculation results of the VolumeEC calculation.

Description

Technical Field

[0001] The embodiments disclosed in this specification and the drawings relate to an X-ray CT apparatus and an information 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 lying position or a standing position is known.

[0003] By the way, some X-ray CT apparatuses have a function called VolumeEC, which is a function of adjusting the intensity of X-rays based on information such as the body thickness and CT value of the subject inferred from the scan image so as to obtain an image with a specified image quality as a function of reducing the exposure dose of the subject. For example, by using VolumeEC, it is possible to image a subject using the minimum X-ray irradiation conditions that can ensure image quality while reducing noise.

[0004] Here, in an X-ray CT apparatus capable of imaging a subject in a lying position and a standing position, a bed (top plate) is generally used to support the subject in the lying position, and a columnar subject holder (also referred to as a subject fixing pole) is generally used to support the subject in the standing position.

[0005] Therefore, when imaging is performed in the lying mode and when imaging is performed in the standing mode (or sitting mode), objects other than the subject present in the aperture of the gantry during imaging are different between the top plate and the subject fixing pole. For this reason, there is a difference in the X-ray absorption amount of the subject between the case of imaging in the lying mode and the case of imaging in the standing mode.

[0006] Therefore, even when using the same X-ray CT scanner and the same imaging conditions, the image quality of the generated images may differ depending on the imaging mode. For example, when acquiring a scan image of a subject, even when using the same X-ray CT scanner and the same imaging conditions, the image quality of the scan image may differ depending on whether the imaging mode is supine or standing.

[0007] Furthermore, in the aforementioned VolumeEC, the thickness and CT value of the subject's body are estimated based on the scan image. This means that, depending on the imaging mode, it may not be possible to correctly estimate the thickness and CT value of the subject's body, and therefore, it may not be possible to correctly derive the X-ray irradiation conditions necessary to obtain a CT image of the specified quality. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2018-051305 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] One of the problems that the embodiments disclosed herein and in the drawings aim to solve is to perform calculations related to Volume EC under conditions suitable for the state of the gantry in an X-ray CT apparatus capable of imaging subjects in at least supine and standing positions. 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]

[0010] The X-ray CT apparatus according to this embodiment comprises a specification unit, a determination unit, a calculation unit, and an adjustment unit. The specification unit identifies a gantry state information that represents the state of the gantry, including at least one of posture information representing the orientation of the gantry having an opening and object information representing objects other than the subject present in the opening. The determination unit determines the VolumeEC parameters to be used in the VolumeEC calculation based on the identified gantry state information and parameter information that stores the gantry state information in association with VolumeEC parameters for performing calculations related to VolumeEC, which is a function for adjusting the X-ray irradiation conditions for the subject. The calculation unit performs the VolumeEC calculation using the determined VolumeEC parameters. The adjustment unit adjusts the X-ray irradiation conditions based on the calculation results of the VolumeEC calculation. [Brief explanation of the drawing]

[0011] [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 shows an example of a scan image taken of a subject in the supine position according to the embodiment. [Figure 5] Figure 5 shows an example of a scan image taken of a subject in standing mode according to the embodiment. [Figure 6] Figure 6 is a flowchart showing an example of a process performed by the X-ray CT apparatus according to this embodiment. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of an X-ray computed tomography (X-ray CT) apparatus and an information processing method will be described 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.

[0013] 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.

[0014] 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.

[0015] The gantry unit 10 is a scanning device configured for performing X-ray CT imaging on a subject P in an upright or supine position. The console unit 100 is a computer that controls the gantry unit 10.

[0016] The mounting device 10 comprises a mounting frame (also called a gantry) 11, a support column 13, a rotary drive device 23, and a mounting frame control device 25.

[0017] The frame 11 has an imaging system for photographing a subject P and an opening 15 into which the subject P can be inserted. The support column 13 supports the frame 11 so that the orientation of the opening 15 can be changed between the vertical and horizontal directions, and so that the frame 11 can be moved along the vertical direction.

[0018] In addition, in FIG. 1, the gantry 11 is supported as a cantilever beam by the support column 13, but it is not limited to this. For example, the gantry 11 may be supported by a plurality of support columns (for example, two support columns). The support column 13 may also be referred to as a support column part.

[0019] The gantry 11 has an opening 15 that forms a imaging space for imaging 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 for imaging the subject P in the present embodiment.

[0020] In addition, 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 for imaging the subject P. The gantry 11 is supported by the support column 13 so as to be movable in the vertical direction along the support column 13.

[0021] Also, the gantry 11 is supported by the support column 13 so 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.

[0022] The gantry 11 has 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 by 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 slidably contact the annular electrode.

[0023] The support column 13 is a base that supports the gantry 11 away from the floor surface.

[0024] The support column 13 has a columnar shape, such as a cylindrical or prismatic shape. The support column 13 is made of any material, such as plastic or metal. The support column 13 is attached to the side of the frame 11, for example. The support column 13 supports the frame 11 so that it can slide vertically, with the rotation axis A1 of the opening 15 facing approximately perpendicular to the floor surface, in order to perform X-ray CT imaging of a subject P in a seated or standing position.

[0025] Typically, the support column 13 is provided on one side of the frame 11. However, this embodiment is not limited to this. For example, two support columns 13 may be connected to both sides of the frame 11. That is, at least one support column 13 supports the frame 11 so that it can move vertically.

[0026] Furthermore, although the support column 13 is described as having a columnar shape, this embodiment is not limited to this. For example, the support column 13 may have any shape, such as a U-shape, as long as it can support at least one side of the frame 11.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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, the subject P is photographed in a standing position with the subject fixing pole 30a present inside the rigging device 11. The subject P can maintain a stable standing posture without swaying by lightly leaning their back against the subject fixing pole 30a.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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).

[0041] 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.

[0042] 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.

[0043] 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).

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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).

[0054] 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).

[0055] 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.

[0056] 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.

[0057] 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.

[0058] The tabletop moving mechanism 37 moves the tabletop 30 under the control of the movement control circuit 27.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] The movement control circuit 27 controls the movement of the frame 11 and the top plate 30.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] The movement control circuit 27 is implemented by the processor and other components described above.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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).

[0079] Memory 101 is a storage device such as an HDD (Hard Disk Drive), SSD (Solid State Drive), or integrated circuit memory that stores various types of information. For example, memory 101 stores projection data and reconstructed image data.

[0080] Furthermore, for example, memory 101 stores parameter information 1011. Parameter information 1011 stores information indicating whether the imaging mode is supine or standing, associated with the VolumeEC parameters. Parameter information 1011 is used in the VolumeEC parameter determination process and the X-ray irradiation condition adjustment process by the processing circuit 107 described later.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] The input interface 105 can, for example, be a mouse, keyboard, trackball, switch, button, joystick, touchpad, or touch panel display, as appropriate.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.).

[0092] The processing circuit 107 executes system control functions 111, decision functions 113, adjustment functions 115, preprocessing functions 117, reconstruction functions 119, and image processing functions 121 using a processor that executes programs loaded into memory.

[0093] Here, the system control function 111 is an example of a reception unit. The decision function 113 is an example of a specification unit and a decision unit. The adjustment function 115 is an example of a calculation unit and an adjustment unit.

[0094] Furthermore, the system control function 111, decision function 113, adjustment 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, decision function 113, adjustment function 115, preprocessing function 117, reconstruction function 119, and image processing function 121, respectively.

[0095] 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.

[0096] 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.

[0097] In this embodiment, the input operation includes the selection of the imaging protocol. The imaging protocol also includes information indicating whether the imaging mode is standing mode or supine mode.

[0098] The determination function 113 determines the VolumeEC parameters to be used in the calculation process related to VolumeEC based on the type of object present in the X-ray tube path (between the X-ray tube 17 and the X-ray detector 19). For example, the calculation process related to VolumeEC is a process that calculates estimated values ​​such as the body thickness and CT value of the subject P based on the scan image.

[0099] Here, Figure 4 shows an example of a scan image taken of subject P in supine mode. Figure 5 shows an example of a scan image taken of subject P in standing mode. As shown in Figures 4 and 5, the objects present in the X-ray tube path differ between when subject P is photographed in supine mode and when subject P is photographed in standing mode, specifically the tabletop 30 and the subject fixing pole 30a.

[0100] Therefore, differences occur in the amount of X-ray absorption by the subject P, resulting in differences in the image quality of the scan. Consequently, even if the same VolumeEC parameters are used to calculate the body thickness and CT value of the subject P, the calculation results may differ depending on whether the imaging mode is standing or supine. In other words, depending on the imaging mode, it may not be possible to correctly estimate the body thickness and CT value of the subject P, and the X-ray irradiation conditions may not be adjusted to the optimal conditions.

[0101] Therefore, the X-ray CT apparatus 1 according to this embodiment stores the optimal VolumeEC parameters for each imaging mode, taking into account objects present in the X-ray tube path, and adjusts the X-ray irradiation conditions to optimal conditions by calculating the body thickness and CT value of the subject P using the VolumeEC parameters corresponding to the imaging mode.

[0102] For example, the decision function 113 identifies whether the shooting conditions and shooting mode are standing mode or supine mode from the information contained in the shooting protocol selected by the system control function 111. The decision function 113 refers to the parameter information 1011 in the memory 101 and determines the VolumeEC parameters associated with the identified shooting mode as VolumeEC parameters to be used in the calculation process related to VolumeEC.

[0103] The adjustment function 115 performs calculations related to VolumeEC using the VolumeEC parameters determined by the determination function 113. Furthermore, the adjustment function 115 adjusts the X-ray irradiation conditions based on the calculation results related to VolumeEC.

[0104] For example, the adjustment function 115 uses the VolumeEC parameters determined by the determination function 113 to calculate the body thickness and CT value of the subject P. Based on the calculated body thickness and CT value of the subject P, the adjustment function 115 adjusts the X-ray irradiation conditions (e.g., tube voltage and tube current) so that a CT image of the specified quality is generated. In this embodiment, the information representing the specified quality is included in the imaging protocol.

[0105] Furthermore, the adjustment function 115 performs the process of adjusting the above-mentioned X-ray irradiation conditions in real time while the subject P is being scanned. As a result, the X-ray CT apparatus 1 according to this embodiment can perform calculations related to VolumeEC under optimal conditions, reduce the radiation dose to the subject P, and scan the subject P using the minimum X-ray irradiation conditions that can ensure image quality while reducing noise.

[0106] Returning to Figure 1, let's continue the explanation. The preprocessing function 117 generates data by applying preprocessing such as logarithmic transformation, offset correction, inter-channel sensitivity correction, and beam hardening correction to the raw data output from DAS33. Note that the data before preprocessing is also called raw data, and the data after preprocessing is also called projected data.

[0107] The reconstruction function 119 performs a reconstruction process on the projection data to generate a reconstructed image.

[0108] For example, the reconstruction function 119 applies to the projection data generated by the preprocessing function 117. CT image data is generated by performing reconstruction processing 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. The reconstruction function 119 stores the generated reconstructed image data in the memory 101.

[0109] The image processing function 121 applies various image processing to the reconstructed image generated 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.

[0110] The following describes the processes performed by the X-ray CT apparatus 1 according to this embodiment. Figure 6 is a flowchart showing an example of the processes performed by the X-ray CT apparatus 1 according to this embodiment.

[0111] 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.

[0112] Next, the decision function 113 identifies the imaging mode of the subject P (step S12). For example, the decision function 113 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 decision function 113 determines whether the identified imaging mode is a supine mode (or an upright mode) (step S13).

[0113] If the shooting mode is supine mode (step S13: Yes), the determination function 113 refers to the parameter information 1011 in memory 101 and determines the VolumeEC parameter associated with supine mode as the VolumeEC parameter to be used in the calculation process related to VolumeEC (step S14).

[0114] Next, the system control function 111 acquires a scan image of the subject P in supine mode (step S15). For example, the system control function 111 controls each part of the X-ray CT apparatus 1 according to the user's operation and acquires a scan image of the subject P. Note that a scan image of the subject P taken in supine mode may have been acquired in advance.

[0115] Next, the adjustment function 115 performs calculations related to VolumeEC using the VolumeEC parameters in supine mode (step S16). For example, the adjustment function 115 uses the VolumeEC parameters in supine mode determined in step S14 to calculate the body thickness and CT value of the subject P.

[0116] Next, the adjustment function 115 adjusts the X-ray irradiation conditions (step S17). For example, based on the body thickness and CT value of the subject P calculated in step S16, the adjustment function 115 adjusts the X-ray irradiation conditions so that a CT image with image quality corresponding to the information representing the specified image quality included in the imaging protocol accepted in step S11 is generated.

[0117] Next, the system control function 111 irradiates the subject P with X-rays under the adjusted X-ray irradiation conditions (step S18). For example, the system control function 111 controls each part of the X-ray CT scanner 1 and irradiates the subject P with X-rays under the X-ray irradiation conditions adjusted in step S17.

[0118] Next, the system control function 111 determines whether it has been instructed to end the imaging of subject P in supine mode (step S19). If it has not been instructed to end the imaging of subject P in supine mode (step S19: No), the process returns to step S17. On the other hand, if it has been instructed to end the imaging of subject P in supine mode (step S19: Yes), this process ends.

[0119] On the other hand, if the shooting mode in step S13 is either standing mode or sitting mode (step S13: No), the determination function 113 refers to the parameter information 1011 in memory 101 and determines the VolumeEC parameter associated with the standing mode as the VolumeEC parameter to be used in the calculation process related to VolumeEC (step S20).

[0120] Next, the system control function 111 acquires a scan image of the subject P in either standing or sitting mode (step S21). For example, the system control function 111 controls each part of the X-ray CT apparatus 1 according to the user's operation to acquire a scan image of the subject P. Note that a scan image of the subject P taken in standing mode may have been acquired in advance.

[0121] Next, the adjustment function 115 performs calculations related to VolumeEC using the VolumeEC parameters in the standing mode (step S22). For example, the adjustment function 115 uses the VolumeEC parameters in the standing mode determined in step S14 to calculate the body thickness and CT value of the subject P.

[0122] Next, the adjustment function 115 adjusts the X-ray irradiation conditions (step S23). For example, based on the body thickness and CT value of the subject P calculated in step S16, the adjustment function 115 adjusts the X-ray irradiation conditions so that a CT image with image quality corresponding to the information representing the specified image quality included in the imaging protocol accepted in step S11 is generated.

[0123] Next, the system control function 111 irradiates the subject P with X-rays under the adjusted X-ray irradiation conditions (step S24). For example, the system control function 111 controls each part of the X-ray CT scanner 1 and irradiates the subject P with X-rays under the X-ray irradiation conditions adjusted in step S17.

[0124] Next, the system control function 111 determines whether it has been instructed to finish imaging of the subject P in standing or sitting mode (step S25). If it has not been instructed to finish imaging of the subject P in standing or sitting mode (step S25: No), the process returns to step S17. On the other hand, if it has been instructed to finish imaging of the subject P in standing or sitting mode (step S25: Yes), this process ends.

[0125] As described above, the X-ray CT apparatus 1 according to this embodiment identifies the orientation of the gantry 11 and objects present in the X-ray path, determines the VolumeEC parameters to be used in the VolumeEC calculation based on the identified orientation of the gantry 11 and objects present in the X-ray path, and parameter information 1011 that stores the orientation of the gantry 11 and objects present in the X-ray path in association with VolumeEC parameters for performing calculations related to VolumeEC, performs calculations related to VolumeEC using the determined VolumeEC parameters, and adjusts the X-ray irradiation conditions based on the calculation results of the VolumeEC calculation.

[0126] For example, if calculations related to VolumeEC are performed using the same VolumeEC parameters regardless of the state of the gantry 11, the objects present in the X-ray path (top plate 30 or subject fixing pole 30a) will differ, and the amount of X-ray absorption will also differ depending on the object. Therefore, depending on the state of the gantry 11, there is a possibility that the image quality of the scan image of the subject P will differ. Consequently, even if calculations related to VolumeEC (such as the body thickness and CT value of the subject P) are performed using the same VolumeEC parameters, there may be differences in the calculation results related to VolumeEC. In other words, depending on the state of the gantry 11, it may not be possible to perform calculations related to VolumeEC correctly, and the X-ray irradiation conditions may not be able to be adjusted to the optimal conditions. In contrast, the X-ray CT apparatus 1 according to this embodiment can perform calculations related to VolumeEC using VolumeEC parameters corresponding to the type of object present in the X-ray path. As a result, the X-ray CT apparatus 1 according to this embodiment can perform calculations related to VolumeEC under conditions suitable for the state of the gantry 11 (the type of object present in the X-ray path).

[0127] 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.

[0128] (Variation 1) In the embodiments described above, when the subject P is in a seated position, the method for determining the VolumeEC parameters and performing calculations related to VolumeEC was described, assuming that the imaging mode is the standing mode, similar to when the subject P is in a standing position. In this modified example, the VolumeEC parameters for the seated imaging state (also called the seated mode) are stored, and when the subject P is in a seated position, the method for performing calculations related to VolumeEC is described using the VolumeEC parameters corresponding to the seated mode.

[0129] In this modified example, the parameter information 1011 in memory 101 stores information indicating that the shooting mode is the seated mode, and the optimal VolumeEC parameters for the seated mode, in association with each other.

[0130] In this modified version, the imaging protocol includes information indicating whether the imaging mode is supine, standing, or sitting.

[0131] If the imaging mode included in the imaging protocol received by the system control function 111 is a seated mode, the determination function 113 refers to the parameter information 1011 in the memory 101 and determines the VolumeEC parameter associated with the seated mode as the VolumeEC parameter to be used for calculation processing related to VolumeEC.

[0132] In this modified example, when the support structure is in a seated position, VolumeEC parameters suitable for the seated mode, different from those corresponding to the standing mode, can be used in the VolumeEC calculation process. In other words, according to this modified example, VolumeEC calculations can be performed under more suitable conditions.

[0133] (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).

[0134] 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.

[0135] 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.

[0136] 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.

[0137] In this modified example, the parameter information 1011 in memory 101 stores the VolumeEC parameter that is optimal for each angle of the top panel (in this modified example, in 5° increments from 90° to 180°).

[0138] In this modified version, the imaging protocol includes information indicating the angle of the tabletop used to image subject P.

[0139] The determination function 113 refers to the parameter information 1011 in the memory 101 and determines the VolumeEC parameter associated with the information representing the angle of the top plate included in the shooting protocol received by the system control function 111 as the VolumeEC parameter to be used for calculation processing related to VolumeEC.

[0140] In this modified version, VolumeEC parameters suitable for the angle of the top plate can be used in the calculation process related to VolumeEC. In other words, according to this modified version, calculations related to VolumeEC can be performed under more suitable conditions.

[0141] (Variation 3) In the embodiments described above, a configuration was described in which the optimal VolumeEC parameter for each shooting mode was predetermined. In this modification, a configuration is described in which the same VolumeEC parameter is used regardless of the shooting mode, and the optimal calculation method for each shooting mode (such as multiplying by a correction coefficient prepared for each shooting mode after the calculation related to VolumeEC) is predetermined for each shooting mode.

[0142] In this modified example, the parameter information 1011 of memory 101 stores one VolumeEC parameter. Memory 101 also stores calculation information. The calculation information stores information representing the imaging mode and a correction coefficient in association. Here, the correction coefficient is determined considering the type of object present in the X-ray tube path (e.g., the top plate 30 and the subject fixing pole 30a).

[0143] In this modified example, the system control function 111 performs a process of storing information representing the shooting mode and the correction coefficient in association. In this case, the system control function 111 is an example of a memory control unit.

[0144] In this modified example, the adjustment function 115 identifies the imaging mode for imaging the subject P from the information contained in the imaging protocol received by the system control function 111. The adjustment function 115 refers to the calculation information in the memory 101 and identifies the correction coefficient associated with the identified imaging mode.

[0145] The adjustment function 115 performs calculations related to VolumeEC using the VolumeEC parameters determined by the determination function 113, and multiplies the calculation result by a specified correction coefficient to obtain the value that is the calculation result for VolumeEC.

[0146] This modified version eliminates the need to prepare a VolumeEC parameter for each shooting mode, thereby reducing the workload associated with preparing the VolumeEC parameter.

[0147] (Modification 4) In the embodiments described above, the configuration described was one in which the object present in the X-ray tube path was either a top plate 30 or a subject fixing pole 30a. In this modified example, a configuration is described in which an object other than a top plate 30 or a subject fixing pole 30a is inserted into the opening 15 of the frame 11 to perform imaging of the subject P.

[0148] In this modified example, when imaging subject P in supine mode, in addition to the tabletop 30 (CT bed), an angio bed, a flat tabletop, and an operating table are used. Note that the above is just one example of the type of bed used for imaging subject P in supine mode, and other types of beds (tabletops) may be used for imaging subject P.

[0149] In this modified example, the parameter information 1011 in memory 101 stores the imaging conditions, information representing objects present in the X-ray tube path, and the VolumeEC parameters in association with each other.

[0150] In this modified version, the imaging protocol includes information representing objects present in the X-ray tube path. Examples of information representing the type of object present in the X-ray tube path include object information and rigging status information.

[0151] The determination function 113 identifies information representing the imaging conditions and objects present in the X-ray tube path from the information contained in the imaging protocol received by the system control function 111.

[0152] The determination function 113 refers to the parameter information 1011 in the memory 101 and determines the VolumeEC parameters associated with the information representing the objects present in the identified X-ray tube path as the VolumeEC parameters to be used in the calculation process related to VolumeEC.

[0153] 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.

[0154] In this modified example, even when imaging of the subject P is performed by inserting something other than the top plate 30 or the subject fixing pole 30a into the opening 15 of the frame 11, the VolumeEC parameters suitable for such imaging can be used in the calculation process related to VolumeEC. In other words, according to this modified example, calculations related to VolumeEC can be performed under more suitable conditions.

[0155] According to at least one embodiment and modification described above, in an X-ray CT apparatus capable of imaging subjects in at least supine and standing positions, calculations related to VolumeEC can be performed under conditions suitable for the state of the gantry.

[0156] 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]

[0157] 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 Decision Function 115 Adjustment 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 that determines the VolumeEC parameters to be used in the VolumeEC calculation based on the identified stand state information and parameter information that stores the stand state information and VolumeEC parameters for performing calculations related to VolumeEC, which is a function for adjusting the X-ray irradiation conditions for the subject, A calculation unit that performs calculations related to VolumeEC using the determined VolumeEC parameters, Based on the calculation results related to the VolumeEC, an adjustment unit adjusts the X-ray irradiation conditions, An X-ray CT scanner equipped with [a specific feature].

2. The aforementioned frame status information includes the object information, The system further includes a storage control unit that stores in the parameter information a corresponding object information representing the type of object and VolumeEC parameters, at least partially different for each type of object, for each type of object. The X-ray CT apparatus according to claim 1.

3. 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 claim 2.

4. The memory control unit performs the following processes: determine a calculation method for VolumeEC based on the VolumeEC parameter associated with the top plate, using the VolumeEC parameter associated with other objects including the subject holder, and store the calculation method and information representing the type of object in the parameter information; or determine a calculation method for VolumeEC based on the VolumeEC parameter associated with the subject holder, using the VolumeEC parameter associated with other objects including the top plate, and store the calculation method and information representing the type of object in the parameter information. The X-ray CT apparatus according to claim 3.

5. 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 3.

6. 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 5.

7. An information processing method for adjusting the X-ray irradiation conditions of an X-ray CT scanner, Identify a stand state information that represents 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. Based on the identified rigging status information and parameter information that stores the rigging status information and VolumeEC parameters for performing calculations related to VolumeEC, which is a function for adjusting the X-ray irradiation conditions for the subject, the VolumeEC parameters to be used in the VolumeEC calculations are determined. Using the determined VolumeEC parameters, the calculations related to VolumeEC are performed. Based on the calculation results related to the VolumeEC, the X-ray irradiation conditions are adjusted. Information processing methods.

Images