X-ray CT scanner and information processing method

Abstract

In an X-ray CT scanner capable of imaging subjects in both supine and standing positions, the calculated output dose should be adjusted to a value appropriate to the condition of the stand. [Solution] The information processing device according to this embodiment comprises a specification unit, a determination unit, and a calculation unit. The specification unit identifies a stand state information that represents the state of the stand, which includes at least one of posture information that represents the posture of the stand having an opening and object information that represents objects other than the subject present in the opening. The determination unit determines dose parameters to be used to calculate the output dose based on the identified stand state information and parameter information that stores dose parameters for calculating the output dose output by the device in association with the stand state information. The calculation unit calculates the output dose using the determined dose parameters.

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 supine position or a standing position is known.

[0003] By the way, in an X-ray CT apparatus, the dose (also referred to as the output dose) output by the X-ray CT apparatus is calculated and output to a user interface, an examination summary, DoseSR (radiation dose structured reporting), and the like. Further, the data output to the user interface, the examination summary, DoseSR, etc. is adjusted to an optimal value for each apparatus by performing calculations using dose parameters.

[0004] Here, in an X-ray CT apparatus capable of imaging a subject in a supine position and a standing position, a bed (top plate) is generally used to support the subject in the supine 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, in the case of imaging in the supine mode and in the case of imaging in the standing mode (or sitting mode), the objects other than the subject present in the aperture of the gantry at the time of 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 supine mode and the case of imaging in the standing mode. That is, the exposure dose of the subject is different between the case of imaging in the supine mode and the case of imaging in the standing mode.

[0006] Incidentally, it is common practice to set only one dose parameter for each X-ray CT scanner. Therefore, even when using the same X-ray CT scanner and the same imaging conditions, the data output to the user interface, examination summary, DoseSR, etc., may not be adjusted to the optimal value depending on the imaging mode. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2018-051305 [Overview of the project] [Problems that the invention aims to solve]

[0008] One of the problems that the embodiments disclosed herein and in the drawings aim to solve is to adjust the calculated output dose to a value suitable for the state of the gantry in an X-ray CT scanner 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]

[0009] The X-ray CT apparatus according to this embodiment comprises a specification unit, a determination unit, and a calculation 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 dose parameters to be used to calculate the output dose based on the identified stand state information and parameter information that stores dose parameters for calculating the output dose output by the apparatus in association with the stand state information. The calculation unit calculates the output dose using the determined dose parameters. [Brief explanation of the drawing]

[0010] [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 the output dose display screen when a subject is photographed in the supine position according to the embodiment. [Figure 5] Figure 5 shows an example of the output dose display screen when a subject is photographed in the 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]

[0011] Hereinafter, embodiments of the X-ray computed tomography apparatus (hereinafter referred to as the X-ray CT (computed tomography) apparatus) and the 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] In Figure 1, the frame 11 is supported as a cantilever beam by the support columns 13, but this is not the only way. For example, the frame 11 may be supported by multiple support columns (e.g., two support columns). The support columns 13 may also be referred to as support columns.

[0018] The stand 11 has an opening 15 that forms an imaging space for imaging the subject P. The stand 11 is a substantially cylindrical structure with the opening 15 formed therein. As shown in Figure 1, the stand 11 houses an X-ray tube 17 and an X-ray detector 19 that are arranged opposite 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 this embodiment.

[0019] The imaging system may also include a data acquisition circuit (hereinafter also referred to as DAS (Data Acquisition System)) 33, a high-voltage generator 31, a collimator, and a wedge, etc. In other words, the stand 11 has an imaging system for imaging the subject P. The stand 11 is supported on the support column 13 so as to be movable in the vertical direction along the support column 13.

[0020] Further, the gantry 11 is supported by the 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.

[0021] The gantry 11 has a main frame (not shown) formed of a metal such as aluminum, and a rotating frame 21 rotatably supported by the main frame via bearings or the like around the rotation axis A1. 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.

[0022] The column 13 is a base that supports the gantry 11 away from the floor surface.

[0023] The column 13 has, for example, a columnar shape such as a cylindrical shape or a prismatic shape. The column 13 is formed of an arbitrary material such as plastic or metal. The column 13 is attached to, for example, a side surface portion of the gantry 11. 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 as to be slidable in the vertical direction for X-ray CT imaging of the subject P in a sitting or standing position.

[0024] 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.

[0025] Also, although the column 13 has been described as having 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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).

[0040] 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.

[0041] 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.

[0042] 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).

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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).

[0053] 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).

[0054] 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.

[0055] 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.

[0056] 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.

[0057] The tabletop moving mechanism 37 moves the tabletop 30 under the control of the movement control circuit 27.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] The movement control circuit 27 controls the movement of the frame 11 and the top plate 30.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] The movement control circuit 27 is implemented by the processor and other components described above.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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).

[0078] 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.

[0079] 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 dose parameters. Parameter information 1011 is used in the dose parameter determination process and the output dose calculation process using the dose parameters by the processing circuit 107 described later.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] The input interface 105 can, for example, be a mouse, keyboard, trackball, switch, button, joystick, touchpad, or touch panel display, as appropriate.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.).

[0091] The processing circuit 107 executes system control functions 111, decision functions 113, calculation functions 115, preprocessing functions 117, reconstruction functions 119, and image processing functions 121 using a processor that executes a program loaded into memory.

[0092] 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 calculation function 115 is an example of a calculation unit.

[0093] Furthermore, the system control function 111, decision function 113, calculation 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, calculation function 115, preprocessing function 117, reconstruction function 119, and image processing function 121, respectively.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] The determination function 113 determines the dose parameters used to calculate the output dose 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).

[0098] Here, the objects present in the X-ray tube path differ between when the subject P is photographed in supine mode and when the subject P is photographed in standing mode, specifically the tabletop 30 and the subject fixing pole 30a.

[0099] Therefore, even when performing imaging with the same X-ray CT scanner 1 under identical imaging conditions except for the imaging mode, and calculating the output dose using the same dose parameters, there may be differences in the radiation exposure of subject P depending on whether the imaging mode is standing or supine. In other words, depending on the imaging mode, it may not be possible to adjust the calculated output dose to the optimal value.

[0100] Therefore, the X-ray CT apparatus 1 according to this embodiment stores optimal dose parameters for each imaging mode, taking into account objects present in the X-ray tube path, and adjusts the calculated output dose to an optimal value by using the dose parameters corresponding to the imaging mode.

[0101] For example, the decision function 113 identifies whether the shooting mode is standing mode or supine mode from the information contained in the shooting protocol for which the selection input has been received by the system control function 111. The decision function 113 refers to the parameter information 1011 in the memory 101 and determines the dose parameters associated with the identified shooting mode as dose parameters to be used in calculating the output dose.

[0102] The calculation function 115 calculates the output dose using the dose parameters determined by the determination function 113.

[0103] For example, when X-rays are not being emitted from the X-ray tube 17, the calculation function 115 uses the dose parameters determined by the determination function 113 to calculate a predicted output dose when the subject P is photographed under imaging conditions such as tube voltage and tube current corresponding to the imaging protocol accepted by the system control function 111.

[0104] Furthermore, for example, when X-rays are being irradiated from the X-ray tube 17, the calculation function 115 uses the dose parameters determined by the determination function 113 to calculate the output dose from the start of X-ray irradiation to the present time. The calculation results are output by methods such as displaying them on the GUI using the system control function 111.

[0105] Here, Figure 4 shows an example of the output dose display screen 1031 when subject P is photographed in supine position.

[0106] The display screen 1031 in Figure 4 is an example of a GUI for receiving various operations from the user, in which the output dose calculated and displayed when subject P is photographed in supine mode is shown. Note that the image PI1 is drawn in the figure for the purpose of indicating that subject P is in supine mode for photographic purposes, but the image PI1 may also be displayed together with the display screen 1031.

[0107] The display screen 1031 has a screen configuration that includes a shooting condition setting section 1033, a reconstruction condition setting section 1035, and an output dose display section 1037.

[0108] The shooting condition setting field 1033 is a display field for an operator that accepts input operations for various shooting conditions (e.g., shooting range, tube voltage, tube current, X-ray tube rotation speed, etc.). In this embodiment, when the system control function 111 receives input from the user to select an shooting protocol, the various shooting conditions corresponding to that shooting protocol are automatically displayed. The user can change and adjust the various shooting conditions based on the automatically displayed conditions.

[0109] The reconstruction condition setting field 1035 is a display field for an operator that accepts input operations for reconstruction conditions used in the reconstruction process (for example, specifying the organ to be imaged). In this embodiment, when the system control function 111 receives input from the user for selecting an imaging protocol, the reconstruction conditions corresponding to that imaging protocol are automatically displayed. The user can change and adjust the reconstruction conditions based on the automatically displayed conditions.

[0110] The output dose display area 1037 is a display area that shows the output dose calculated by the calculation function 115 using the dose parameters determined by the determination function 113. In the example in Figure 4, the output dose display area 1037 displays the output dose calculated using the dose parameters associated with the information representing the supine mode in the parameter information 1011.

[0111] In addition, in the example in Figure 4, CTDIvol, DLP, and SSDE are displayed as output doses.

[0112] Here, CTDIvol represents the absorbed dose of radiation per centimeter received by subject P. DLP represents the absorbed dose of radiation for the scanning area. DLP is calculated using the formula CTDIvol × scanning area (cm). SSDE (Size-specific dose estimates) is a dose index that takes into account differences in the body shape of subject P. SSDE is used to evaluate the approximate absorbed dose of any given cross-section.

[0113] In addition, the output dose display section 1037 also displays information related to the output dose, including information representing the water equivalent diameter Dw used in the SSDE calculation.

[0114] Figure 5 shows an example of the output dose display screen 1032 when subject P is photographed in standing mode.

[0115] The display screen 1032 in Figure 5 is an example of a GUI for receiving various operations from the user, which calculates and displays the output dose when subject P is photographed in standing mode. The photographic image PI2 is drawn in the figure for the purpose of indicating that subject P is in standing mode for ease of explanation, but the photographic image PI2 may also be displayed together with the display screen 1032.

[0116] The display screen 1032 has a screen configuration consisting of a shooting condition setting area 1034, a reconstruction condition setting area 1036, and an output dose display area 1038. The shooting condition setting area 1034 and the reconstruction condition setting area 1036 are the same as the shooting condition setting area 1033 and the reconstruction condition setting area 1035, so their explanation is omitted.

[0117] In the example in Figure 5, the output dose display area 1038 shows the output dose calculated using the dose parameters associated with the information representing the standing mode in the parameter information 1011.

[0118] As shown in Figures 4 and 5, in this embodiment, even when imaging subject P under the same imaging conditions, different values ​​are displayed as output doses on the GUI if the imaging mode is different. This allows the output dose calculated for each imaging mode to be adjusted to the optimal value, enabling the user to perform highly accurate dose management.

[0119] In this embodiment, the system control function 111 has been described in which the calculated output dose is displayed on the GUI, but the method for outputting the output dose is not limited to the above. For example, the system control function 111 may output the calculated output dose to the examination summary, DoseSR, etc.

[0120] 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.

[0121] The reconstruction function 119 performs a reconstruction process on the projection data to generate a reconstructed image.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] In the example shown in Figure 6, the system control function 111 calculates and outputs a predicted output dose when subject P is photographed under the shooting conditions corresponding to the shooting protocol received by the system control function 111 before the subject P is photographed. However, the process of calculating and outputting the output dose may also be performed during or after the photography of subject P.

[0126] 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.

[0127] Next, the determination function 113 identifies the imaging mode of the subject P (step S12). For example, the determination 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 determination function 113 determines whether the identified imaging mode is a supine mode (or an upright mode or a sitting mode) (step S13).

[0128] If the imaging mode is supine mode (step S13: Yes), the determination function 113 refers to the parameter information 1011 in memory 101 and determines the dose parameters associated with supine mode as dose parameters to be used for calculating the output dose (step S14).

[0129] Next, the calculation function 115 calculates the output dose using the dose parameters for the supine mode (step S15). For example, the calculation function 115 calculates the output dose using the imaging conditions corresponding to the imaging protocol received in step S11 and the dose parameters for the supine mode determined in step S14. After step S15, the process proceeds to step S18, which will be described later.

[0130] 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 dose parameters associated with the standing mode as parameters to be used for output dose calculation (step S16).

[0131] Next, the calculation function 115 calculates the output dose using the dose parameters for the standing mode (step S17). For example, the calculation function 115 calculates the output dose using the imaging conditions corresponding to the imaging protocol received in step S11 and the dose parameters for the standing mode determined in step S16.

[0132] Next, the system control function 111 outputs the output dose (step S18) and terminates this process. For example, the system control function 111 controls the display of the output dose calculated in step S15 or S17 on the GUI.

[0133] 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, and determines dose parameters to be used for calculating the output dose based on the identified orientation of the gantry 11 and objects present in the X-ray path, and parameter information 1011 that stores the correspondence between the orientation of the gantry 11 and objects present in the X-ray path and dose parameters for calculating the output dose output by the X-ray CT apparatus 1, and calculates the output dose using the determined dose parameters.

[0134] Here, for example, if the output dose is calculated using the same dose parameters regardless of the state of the stand 11, a difference may occur between the calculated output dose and the actual output dose depending on the state of the stand 11, because the objects in the X-ray path (top plate 30 or subject fixing pole 30a) are different, and the amount of X-ray absorption also differs depending on the object. In contrast, the X-ray CT apparatus 1 according to this embodiment can calculate the output dose using dose parameters corresponding to the type of object in the X-ray path. As a result, the X-ray CT apparatus 1 according to this embodiment can adjust the calculated output dose to a value suitable for the state of the stand 11 (type of object in the X-ray path).

[0135] 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.

[0136] (Variation 1) In the embodiments described above, when the subject P is in a seated position, the method for determining dose parameters and calculating output dose was described as being the same as when the subject P is in a standing position, assuming that the imaging mode is the standing mode. In this modification, the method for storing dose parameters in a seated imaging state (also called seated mode) and calculating output dose using the dose parameters corresponding to the seated mode when the subject P is in a seated position is described.

[0137] In this modified example, the parameter information 1011 in memory 101 stores information indicating that the imaging mode is the seated mode, and the optimal dose parameters for the seated mode, in association with each other.

[0138] In this modified version, the imaging protocol includes information indicating whether the imaging mode is supine, standing, or sitting.

[0139] 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 dose parameters associated with the seated mode as dose parameters to be used in the calculation process of the output dose.

[0140] In this modified version, when the subject P is in a seated position during imaging, dose parameters suitable for the seated position, which differ from those corresponding to the standing position, can be used in the calculation of the output dose. In other words, according to this modified version, the calculated output dose can be adjusted to a more appropriate value.

[0141] (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).

[0142] 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.

[0143] 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.

[0144] 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.

[0145] In this modified example, the parameter information 1011 in memory 101 stores the optimal dose parameter for each angle of the top plate (in this modified example, in 5° increments from 90° to 180°).

[0146] In this modified version, the imaging protocol includes information indicating the angle of the tabletop used to image subject P.

[0147] The determination function 113 refers to the parameter information 1011 in the memory 101 and determines the dose parameter associated with the information representing the angle of the top plate included in the imaging protocol received by the system control function 111 as the dose parameter to be used in the output dose calculation process.

[0148] In this modified version, dose parameters appropriate to the angle of the top plate can be used in the calculation process of the output dose. In other words, according to this modified version, the calculated output dose can be adjusted to a more appropriate value.

[0149] (Variation 3) In the embodiments described above, a configuration was described in which the optimal dose parameters for each shooting mode were predetermined. In this modification, a configuration is described in which the same dose parameters are used regardless of the shooting mode, and the optimal calculation method for each shooting mode (such as multiplying the calculated output dose by a correction coefficient prepared for each shooting mode) is predetermined for each shooting mode.

[0150] In this modified example, the parameter information 1011 of memory 101 stores one dose parameter. Furthermore, 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 or the subject fixing pole 30a).

[0151] In this modified example, the system control function 111 performs a process of associating and storing information representing the shooting mode with a correction coefficient. In this case, the system control function 111 is an example of a memory control unit.

[0152] In this modified example, the calculation 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 calculation function 115 refers to the calculation information in memory 101 and identifies the correction coefficient associated with the identified imaging mode.

[0153] The calculation function 115 calculates the output dose using the dose parameters stored in the parameter information 1011 of the memory 101, and the value obtained by multiplying the calculation result by a specified correction coefficient is taken as the output dose.

[0154] According to this modification, it becomes unnecessary to prepare dose parameters for each shooting mode, thus reducing the workload associated with preparing dose parameters.

[0155] (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.

[0156] 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.

[0157] 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 dose parameters in association with each other.

[0158] 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 information.

[0159] The determination function 113 identifies information representing an object present in the X-ray tube path from the information contained in the imaging protocol received by the system control function 111.

[0160] The determination function 113 refers to the parameter information 1011 in the memory 101 and determines the dose parameters associated with the information representing the objects present in the identified X-ray tube path as dose parameters to be used in the output dose calculation process.

[0161] 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.

[0162] 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, dose parameters suitable for such imaging can be used in the calculation process of the output dose. In other words, according to this modified example, the calculated output dose can be adjusted to a more appropriate value.

[0163] According to at least one embodiment or modification described above, in an X-ray CT scanner capable of imaging subjects in a supine or standing position, the calculated output dose can be adjusted to an optimal value.

[0164] 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]

[0165] 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 Calculation 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 dose parameters used to calculate the output dose based on the identified mounting status information and parameter information that stores the mounting status information and dose parameters for calculating the output dose output by the device in association, A calculation unit that calculates the output dose using the determined dose parameters, 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, for each type of object, object information representing the type of object and dose parameters that differ for each type of object, in association with each type of object, in the parameter information. 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 based on the dose parameter associated with the top plate, using the dose 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 based on the dose parameter associated with the subject holder, using the dose 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 calculating the output dose of 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 mounting status information and parameter information that stores the mounting status information and dose parameters for calculating the output dose output by the device in association, the dose parameters used for calculating the output dose are determined. The output dose is calculated using the determined dose parameters. Information processing methods.

Images