X-ray CT apparatus, control method for x-ray CT apparatus, and program

Abstract

To display an image matched to movement of a top plate and to reduce a deviation amount between an imaging position and a real position of the top plate when scanning is interrupted in an X-ray CT apparatus.SOLUTION: An X-ray CT apparatus includes: an acquisition part acquiring detection data of a detector during photography when a rotary part having an X-ray tube and a detector detecting X-ray passing a subject is rotating; and a reconstruction processing part for generating reconstruction image data from projection data based on the detection data. The reconstruction processing part has a first generation part; a second generation part; and a third generation part. The first generation part generates first reconstruction image data reconstructed from the projection data at a first time interval. The second generation part generates second reconstruction image data for display to a display part at a second time interval from the first reconstruction image data. The third generation part generates third reconstruction image data of higher image quality than the second reconstruction image data at a third time interval.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The embodiments disclosed in this specification and the drawings relate to an X-ray CT apparatus, a control method for an X-ray CT apparatus, and a program. [Background technology]

[0002] X-ray CT (Computed Tomography) systems have been used in the field of medical imaging diagnosis for a long time. X-ray CT systems use images captured by irradiating a subject (patient) with X-rays to perform diagnostics. In diagnostics using X-ray CT systems, a function is implemented that reconstructs and displays images in real time during scanning (or immediately after scanning) to enable image confirmation. This function allows users to determine whether the intended subject position is being scanned or when to interrupt the scan in a specific scan mode. For example, in helical scanning, in which a rotating frame is rotated while the tabletop of a patient table is moved to scan the subject in a spiral, two types of functions are implemented to reconstruct and display images in synchronization with the scan. One function is called a real-time reconstruction function, which reconstructs and displays images at a fixed display frame rate. With the real-time reconstruction function, images are reconstructed using data from the acquired view (detection data) acquired during the period until the image displayed at the display frame rate is switched, resulting in low image quality. Therefore, the real-time reconstruction function does not save the reconstructed images for display. The other function is called the in-view reconstruction function, which reconstructs an image using the detection data of all acquired views during a specified viewing period, and displays and saves it. The in-view reconstruction function includes a 3D landmark reconstruction function. The purpose of the in-view reconstruction function is to enable the image to be checked (to make a diagnosis) immediately after the scan is completed, so it is required to reconstruct an image of higher quality than the image reconstructed by the real-time reconstruction function.

[0003] In recent years, efforts have been made to increase the speed of X-ray CT systems. Therefore, as the speed of X-ray CT systems increases, there is a concern that it may become difficult to determine when to interrupt a helical scan while checking the images displayed in synchronization with the scan. For example, when the tabletop of a helical scan is moved quickly, the real-time reconstruction function may cause the positions of the subject captured in each display image reconstructed according to the display frame rate to become separated (the positions captured in the images become discontinuous), resulting in a loss of continuity. On the other hand, the in-view reconstruction function increases the processing load required to reconstruct high-quality images, making it difficult to reconstruct images synchronized with the position of the tabletop. In these cases, even if the timing to interrupt the scan is determined while checking the images displayed in synchronization with the scan, there is a concern that the misalignment between the image capture position in the displayed image at the time the scan was interrupted and the actual position of the tabletop may become large (the amount of misalignment may become large). Furthermore, in next-generation X-ray CT devices, such as photon counting CT devices, the amount of detected data will be significantly increased compared to current X-ray CT devices, and it is thought that the tendency for the amount of deviation between the imaging position and the actual position of the tabletop to increase will increase. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-208310 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the embodiments disclosed in this specification and the drawings is to provide an X-ray CT device, a control method for an X-ray CT device, and a program that display images in accordance with the movement of the tabletop in an X-ray CT device and reduce the amount of deviation between the imaging position when a scan is interrupted and the actual position of the tabletop. However, the problem to be solved by the embodiments disclosed in this specification and the drawings is not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be positioned as other problems. [Means for solving the problem]

[0006] An X-ray CT apparatus according to an embodiment includes an acquisition unit that acquires detection data from a rotating unit having an X-ray tube and a detector that detects X-rays transmitted through a subject during imaging while the rotating unit is rotating, and a reconstruction processing unit that generates reconstructed image data from projection data based on the detection data, the reconstruction processing unit having a first generation unit, a second generation unit, and a third generation unit. The first generation unit generates first reconstructed image data reconstructed from the projection data at a first time interval. The second generation unit generates second reconstructed image data from the first reconstructed image data at a second time interval to be displayed on a display unit. The third generation unit generates third reconstructed image data at a third time interval, the third reconstructed image data having higher image quality than the second reconstructed image data. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of the arrangement of an X-ray CT apparatus according to an embodiment. [Figure 2] FIG. 2 is a diagram showing an example of the functional configuration of a reconstruction processing function included in the X-ray CT apparatus according to the embodiment. [Figure 3] FIG. 1 is a diagram schematically showing an example of image reconstruction processing in a conventional X-ray CT apparatus. [Figure 4] FIG. 2 is a diagram schematically showing an example of image reconstruction processing in the reconstruction processing function of the X-ray CT apparatus according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an X-ray CT apparatus, a control method for an X-ray CT apparatus, and a program according to an embodiment will be described with reference to the drawings.

[0009] FIG. 1 is a diagram showing an example of the configuration of an X-ray CT (Computed Tomography) apparatus according to an embodiment. The X-ray CT apparatus 1 is a medical image diagnostic apparatus that irradiates a subject (patient) P with X-rays and detects the X-rays that have passed through the subject P. The X-ray CT apparatus 1 generates and displays images such as reconstructed images (e.g., CT images) corresponding to the detected X-rays. This allows the person performing the CT examination (such as a doctor or technician) to visually check whether or not the subject P has a lesion.

[0010] The X-ray CT apparatus 1 includes, for example, a gantry 10, a bed 30, and a console 40. For convenience of explanation, FIG. 1 shows the gantry 10 viewed from both the Z-axis direction and the X-axis direction, but in reality, the X-ray CT apparatus 1 includes only one gantry 10. In this embodiment, the central axis of the rotating frame 17 in a non-tilted state or the longitudinal direction of the tabletop 33 of the bed 30 (the body axis direction of the subject P) is defined as the Z-axis direction, an axis perpendicular to the Z-axis direction and horizontal to the floor surface is defined as the X-axis direction, and a direction perpendicular to the Z-axis direction and perpendicular to the floor surface is defined as the Y-axis direction. The X-ray CT apparatus 1 is an example of an "X-ray CT apparatus."

[0011] The gantry device 10 includes, for example, an X-ray tube device 11 incorporating an X-ray tube, a wedge 12, a collimator 13, an X-ray high voltage device 14, an X-ray detector 15, a data acquisition system (hereinafter referred to as DAS: Data Acquisition System) 16, a rotating frame 17, and a control device 18.

[0012] The X-ray tube device 11 generates X-rays by causing the built-in X-ray tube to emit thermoelectrons from a cathode (filament) toward an anode (target) in response to a high tube voltage applied by an X-ray high voltage device 14. The X-ray tube device 11 includes, for example, a vacuum tube as an X-ray tube. In the following description, for ease of explanation, the X-ray tube device 11 will be described as an X-ray tube. The X-ray tube device 11 is, for example, a rotating anode type X-ray tube that generates X-rays by emitting thermoelectrons from a cathode to a rotating anode. The X-rays generated by the X-ray tube device 11 are irradiated onto the subject P.

[0013] The wedge 12 is a filter for adjusting the dose (X-ray dose) when the subject P is irradiated with X-rays generated by the X-ray tube device 11. The wedge 12 attenuates the X-rays that pass through it so that the distribution of the X-ray dose irradiated on the subject P becomes a predetermined distribution. The wedge 12 is also called a wedge filter or a bow-tie filter. The wedge 12 is made by processing aluminum so as to have a predetermined target angle and a predetermined thickness, for example.

[0014] The collimator 13 is a mechanism for narrowing the irradiation range of the X-rays that have passed through the wedge 12. The collimator 13 narrows the irradiation range of the X-rays, for example, by combining multiple lead plates to form a slit. The collimator 13 is sometimes called an X-ray aperture. The collimator 13 may be an active collimator whose narrowing range can be mechanically driven.

[0015] The X-ray high voltage device 14 includes, for example, a high voltage generator and an X-ray control device. The high voltage generator has an electric circuit including a transformer and a rectifier, and generates a high voltage to be applied to the X-ray tube device 11. The X-ray control device controls the output voltage of the high voltage generator according to the X-ray dose to be generated in the X-ray tube device 11. The high voltage generator may be one that boosts voltage using the above-mentioned transformer, or one that boosts voltage using an inverter. The X-ray high voltage device 14 may be provided on the rotating frame 17, or may be provided on the side of a fixed frame (not shown) provided on the gantry device 10.

[0016] The X-ray detector 15 detects the intensity of X-rays that are generated by the X-ray tube device 11 and that have passed through the subject P and are incident thereon. The X-ray detector 15 outputs an electrical signal (which may be an optical signal, etc.) corresponding to the intensity of the detected X-rays to the DAS 16. The X-ray detector 15 has, for example, multiple X-ray detection element rows. Each of the multiple X-ray detection element rows has multiple X-ray detection elements arranged in the channel direction along an arc centered on the focal point of the X-ray tube device 11. The multiple X-ray detection element rows are arranged in the slice direction (column direction, row direction).

[0017] The X-ray detector 15 is, for example, an indirect detector having a grid, a scintillator array, and a photosensor array. The scintillator array has multiple scintillators. Each scintillator has scintillator crystals. The scintillator crystals emit light at an amount corresponding to the intensity of the incident X-rays. The grid is arranged on the surface of the scintillator array on which the X-rays are incident and has an X-ray shielding plate that absorbs scattered X-rays. The grid is sometimes called a collimator (one-dimensional collimator or two-dimensional collimator). The photosensor array has, for example, a photosensor such as a photomultiplier tube (PMT). The photosensor array outputs an electrical signal corresponding to the amount of light emitted by the scintillator. The X-ray detector 15 may also be a direct conversion detector having a semiconductor element that converts incident X-rays into an electrical signal.

[0018] The DAS 16 includes, for example, an amplifier, an integrator, and an A / D converter. The amplifier amplifies the electrical signal output by each X-ray detection element of the X-ray detector 15. The integrator integrates the electrical signal amplified by the amplifier over a view period (described later). The A / D converter converts the electrical signal indicating the integration result by the integrator into a digital signal. The DAS 16 outputs detection data based on the digital signal to the console device 40. The detection data is a digital value of X-ray intensity identified by the channel number and column number of the X-ray detection element that generated the detection data, and a view number indicating the acquired view (hereinafter referred to as an "acquisition view"). The view number is a number that changes according to the rotation of the rotating frame 17, and is, for example, a number that is incremented according to the rotation of the rotating frame 17. Therefore, the view number is information indicating the rotation angle of the X-ray tube device 11. The view period is the period from the rotation angle corresponding to a certain view number to the rotation angle corresponding to the next view number. In other words, the view period is the period required to obtain detection data for one irradiation time (projection period) of X-rays irradiated from the X-ray tube device 11 to the subject P at the same rotation angle. The DAS 16 may detect the switching of the acquisition view by a timing signal input from the control device 18, by an internal timer, or by a signal acquired from a sensor (not shown). When the X-ray CT device 1 performs a full scan and X-rays are continuously irradiated by the X-ray tube device 11, the DAS 16 collects a group of detection data for the entire circumference (360 degrees). When the X-ray CT device 1 performs a half scan and X-rays are continuously irradiated by the X-ray tube device 11, the DAS 16 collects detection data for half the circumference (180 degrees).

[0019] The DAS 16 is a sequential readout DAS that sequentially reads out electrical signals from the X-ray detection elements arranged in the X-ray detector 15 with a time lag. That is, the DAS 16 does not simultaneously read out electrical signals from the X-ray detection elements arranged in the X-ray detector 15 during a view period, but reads out electrical signals from each X-ray detection element while sequentially moving the X-ray detection elements arranged in the X-ray detector 15 in the slice direction during the same view period.

[0020] The rotating frame 17 is an annular member that supports the X-ray tube assembly 11, the wedge 12, the collimator 13, and the X-ray detector 15 in opposing positions. The rotating frame 17 is supported by a fixed frame so as to be rotatable around the subject P introduced therein. The rotating frame 17 also supports the DAS 16. Detection data output by the DAS 16 is transmitted by optical communication from a transmitter having a light-emitting diode (LED) provided on the rotating frame 17 to a receiver having a photodiode provided on a non-rotating portion of the gantry 10 (e.g., a fixed frame not shown), and then transferred to the console device 40 by the receiver. The method of transmitting the detection data from the rotating frame 17 to the non-rotating portion is not limited to the above-mentioned method using optical communication, and any non-contact transmission method may be adopted. The rotating frame 17 is not limited to an annular member, and may be an arm-like member as long as it can support and rotate the X-ray tube assembly 11 and the like.

[0021] The X-ray CT device 1 is, for example, a Rotate / Rotate-Type X-ray CT device (third generation CT) in which both the X-ray tube device 11 and the X-ray detector 15 are supported by a rotating frame 17 and rotate around the subject P, but is not limited to this and may also be a Stationary / Rotate-Type X-ray CT device (fourth generation CT) in which a plurality of X-ray detection elements arranged in a circular ring are fixed to a fixed frame and the X-ray tube device 11 rotates around the subject P.

[0022] The control device 18 receives input signals from an input interface (not shown), such as an operation switch, attached to the gantry 10 or an input interface 43 attached to the console device 40, and controls the operations of the gantry 10 and the bed device 30. The control device 18 includes, for example, a processing circuit having a processor such as a CPU (Central Processing Unit), and a drive mechanism including, for example, a motor or an actuator, for moving the gantry 10, rotating the rotating frame 17 included in the gantry 10, and moving the bed device 30. In the embodiment, the case where the control device 18 is provided in the gantry 10 is shown, but the control device 18 may also be provided in the console device 40.

[0023] The control device 18, for example, rotates the rotating frame 17, tilts the gantry 10, moves the housing of the gantry 10 (hereinafter simply referred to as the "gantry 10") horizontally toward the top board 33 of the bed 30 (in the Z-axis direction), and moves the top board 33 of the bed 30 up and down in the Y-axis direction (which may include lateral movement in the X-axis direction and rotational movement around the Z-axis). When tilting the gantry 10, the control device 18 tilts the rotating frame 17 about an axis parallel to the Z-axis direction based on a tilt angle (tilt angle) input to an input interface (not shown) or an input interface 43. The control device 18 grasps the tilt angle of the rotating frame 17 based on the output of a sensor (not shown), etc. The control device 18 provides the tilt angle of the rotating frame 17 to the processing circuit 50 as needed.

[0024] The bed device 30 is a device that places and moves the subject P to be scanned and introduces the subject P into the rotating frame 17 of the gantry device 10. The bed device 30 includes, for example, a base 31, a bed drive device 32, a top 33, and a support frame 34. The base 31 includes a housing that supports the support frame 34 so that the support frame 34 can move in the vertical direction (up and down direction). The bed drive device 32 includes a motor and an actuator. The bed drive device 32 moves the top 33 on which the subject P is placed in the vertical direction (Y-axis direction). The bed drive device 32 may move the top 33 on which the subject P is placed laterally in the horizontal direction (X-axis direction) or rotate it around the Z-axis. The bed drive device 32 may move the top 33 on which the subject P is placed along the support frame 34 in the longitudinal direction of the top 33 (Z-axis direction). When the X-ray CT apparatus 1 is a movable gantry-type X-ray CT apparatus, the amount of longitudinal movement of the tabletop 33 by the bed driving device 32 may be an amount sufficient to introduce into the rotating frame 17 a portion of the subject P that is not yet inside the rotating frame 17 even when the control device 18 moves the gantry 10 to the maximum horizontal position, i.e., an amount sufficient to compensate for the horizontal movement of the gantry 10. When the gantry 10 is movable in the Z-axis direction, the bed driving device 32 may move the gantry 10 so that the rotating frame 17 is positioned around the subject P. The bed driving device 32 may be configured to move both the gantry 10 and the tabletop 33. The tabletop 33 is a plate-like member on which the subject P is placed. The X-ray CT apparatus 1 may be an apparatus in which the subject P is scanned in a standing or sitting position. In this case, the X-ray CT apparatus 1 has a subject support mechanism instead of the bed device 30, and the gantry device 10 rotates the rotating frame 17 about an axial direction perpendicular to the floor surface.

[0025] The X-ray tube assembly 11 (which may include the wedge 12 and the collimator 13) is an example of an "X-ray tube." The X-ray detector 15 is an example of a "detector." The rotating frame 17 is an example of a "rotating unit." The DAS 16 is an example of an "acquisition unit." The detection data output by the DAS 16 is an example of "detection data."

[0026] The console device 40 includes, for example, a memory 41, a display 42, an input interface 43, a network connection circuit 44, and a processing circuit 50. In this embodiment, the console device 40 is described as being separate from the gantry device 10, but the gantry device 10 may include some or all of the components of the console device 40.

[0027] The memory 41 is realized by, for example, a semiconductor memory element such as a read-only memory (ROM), a random access memory (RAM), or a flash memory, a hard disk drive (HDD), or an optical disk. The memory 41 stores, for example, detection data output by the DAS 16, projection data generated based on the detection data, reconstructed images, CT images, and other data. These data may be stored in an external memory with which the X-ray CT apparatus 1 can communicate, instead of (or in addition to) the memory 41. The external memory is controlled by, for example, a cloud server that manages the external memory, by the cloud server accepting a read / write request. The external memory may be realized by, for example, a system called a PACS (Picture Archiving and Communication Systems). A PACS is a medical image management system that systematically stores images captured by various imaging diagnostic apparatuses.

[0028] The display 42 displays various types of information. For example, the display 42 displays images such as reconstructed images and CT images generated by the processing circuitry 50, as well as GUI (Graphical User Interface) images that accept various operations by the person performing the CT examination (such as a doctor or technician). The display 42 is, for example, a liquid crystal display (LCD), a CRT (Cathode Ray Tube) display, or an organic EL (Electroluminescence) display. The display 42 may be provided on the gantry device 10. The display 42 may be a desktop type, or may be a display device (for example, a tablet terminal) that can wirelessly communicate with the main body of the console device 40. The display 42 is an example of a "display unit."

[0029] The input interface 43 accepts various input operations from the person performing the CT examination and outputs electrical signals indicating the contents of the accepted input operations to the processing circuitry 50. For example, the input interface 43 accepts input operations such as acquisition conditions for collecting detection data, generation conditions for generating projection data, reconstruction conditions for reconstructing a reconstructed image, and image processing conditions for generating a post-processed image from the reconstructed image. The input interface 43 may be implemented, for example, by a mouse, keyboard, touch panel, trackball, switch, button, joystick, camera, infrared sensor, microphone, etc. The input interface 43 may be implemented by a display device (e.g., a tablet terminal) capable of wireless communication with the main body of the console device 40. In this specification, the input interface 43 is not limited to one having physical operation components such as a mouse or keyboard. For example, an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the device and outputs the electrical signal to a control circuit is also included as an example of an input interface.

[0030] The network connection circuit 44 includes, for example, a network card having a printed circuit board or a wireless communication module. The network connection circuit 44 implements an information communication protocol according to the type of network to be connected. Examples of networks include a local area network (LAN), a wide area network (WAN), the Internet, a cellular network, and a dedicated line. The network connection circuit 44 realizes a connection between the console device 40 and an external memory realized by, for example, the above-mentioned PACS.

[0031] The processing circuitry 50 controls the overall operation of the X-ray CT apparatus 1. The processing circuitry 50 executes, for example, a system control function 51, a preprocessing function 52, a reconstruction processing function 53, an image processing function 54, a scan control function 55, and a display control function 56. The processing circuitry 50 realizes these functions by, for example, a hardware processor executing a program (software) stored in the memory 41.

[0032] The hardware processor refers to a circuit such as a CPU, a graphics processing unit (GPU), a large-scale integration (LSI), a system on chip (SOC), an application-specific integrated circuit (ASIC), or a programmable logic device (e.g., a simple programmable logic device (SPLD) or a complex programmable logic device (CPLD), or a field programmable gate array (FPGA)). Instead of storing a program in memory 41, the hardware processor may be configured so that the program is directly embedded in the circuit. In this case, the hardware processor realizes its function by reading and executing the program embedded in the circuit. The hardware processor is not limited to being configured as a single circuit, but may be configured as a single hardware processor by combining multiple independent circuits to realize each function. Multiple components may be integrated into a single hardware processor to realize each function. Multiple components may be incorporated into a single dedicated LSI to realize each function. Here, the program (software) may be stored in advance in a storage device (a storage device having a non-transitory storage medium) constituting a storage device such as a ROM, RAM, a semiconductor memory element such as a flash memory, or a hard disk drive, or may be stored in a removable storage medium (a non-transitory storage medium) such as a DVD or CD-ROM, and installed in the storage device provided in the console device 40 by inserting the storage medium into a drive device provided in the console device 40. The program (software) may be downloaded in advance from another computer device via a network connected by the network connection circuit 44, and then installed in the storage device provided in the console device 40.A program (software) installed in a storage device included in the console device 40 may be transferred to a processing circuit included in the control device 18 and executed therein.

[0033] Each component of the console device 40 or the processing circuitry 50 may be distributed and realized by multiple pieces of hardware. The processing circuitry 50 may not be a component of the console device 40, but may be realized by a processing device capable of communicating with the console device 40. The processing device is, for example, a workstation connected to one X-ray CT device, or a device (e.g., a cloud server) connected to multiple X-ray CT devices and collectively executing processing equivalent to that of the processing circuitry 50 described below. In other words, the configuration of this embodiment can also be realized as an X-ray CT examination system (medical diagnostic system) in which an X-ray CT device and other processing devices are connected via a network.

[0034] The system control function 51 controls various functions of the processing circuit 50 based on, for example, an input operation received by the input interface 43 .

[0035] The pre-processing function 52 performs pre-processing on the detection data output by the DAS 16 to generate projection data. The pre-processing includes, for example, logarithmic conversion, offset correction, inter-channel sensitivity correction, and beam hardening correction. The pre-processing function 52 stores the generated projection data in the memory 41. The projection data output by the pre-processing function 52 is an example of "projection data."

[0036] The reconstruction processing function 53 performs a predetermined reconstruction process on the projection data generated by the pre-processing function 52 to generate a reconstructed image. Examples of the predetermined reconstruction process include filtered back projection and iterative reconstruction. The reconstruction processing function 53 generates a reconstructed image for display and a reconstructed image for storage. The reconstructed image for display is a reconstructed image that allows the CT examiner to check the scan status of the X-ray CT apparatus 1 in real time, such as determining whether the intended position of the subject P has been scanned or determining when to interrupt scanning of the subject P in a specific scan mode such as a helical scan (described later). The reconstructed image for storage is a reconstructed image that provides a resolution suitable for the CT examiner to perform an examination and diagnosis of the subject P, i.e., can be used for diagnosis. The reconstruction processing function 53 stores the generated reconstructed images for display and storage in the memory 41. The reconstruction processing function 53 may display the generated reconstructed image for display on the display 42. The reconstruction processing function 53 is an example of a "reconstruction processing unit." The reconstructed image generated by the reconstruction processing function 53 is an example of “reconstructed image data.” The helical scan is an example of “imaging of a subject.”

[0037] The image processing function 54 converts the reconstructed image into a three-dimensional image (CT image) or a cross-sectional image of an arbitrary cross section by a known method based on the input operation received by the input interface 43. The conversion into a three-dimensional image may be performed by the pre-processing function 52.

[0038] The scan control function 55 controls the collection process of detection data in the gantry device 10 by issuing instructions to the X-ray high voltage device 14, the DAS 16, the control device 18, and the bed driving device 32. The scan control function 55 controls the operation of each part when capturing an alignment image, an actual captured image, and an image used for an examination or diagnosis.

[0039] The display control function 56 controls the display mode of the display 42. For example, the display control function 56 controls the display 42 to display a reconstructed image generated by the processing circuitry 50, a GUI image that accepts various operations by the person performing the CT examination, and the like.

[0040] With this configuration, the X-ray CT device 1 irradiates the subject P with X-rays generated by the X-ray tube device 11 to capture (scan) the subject P. The X-ray CT device 1 can scan the subject P in various ways, including helical scanning, conventional scanning, and step-and-shoot. Helical scanning is a method of scanning the subject P in a spiral manner by rotating the rotating frame 17 while moving the top plate 33. Conventional scanning is a method of scanning the subject P in a circular orbit by rotating the rotating frame 17 while keeping the top plate 33 stationary. Step-and-shoot is a method of performing conventional scanning in multiple scan areas by moving the position of the top plate 33 at regular intervals.

[0041] Next, we will explain the configuration and operation of the reconstruction processing function 53. Fig. 2 is a diagram showing an example of the functional configuration of the reconstruction processing function 53 provided in the X-ray CT apparatus 1 according to the embodiment. The reconstruction processing function 53 includes, for example, a reconstruction image generation function 532, a reconstruction image display processing function 534, and a reconstruction image storage processing function 536.

[0042] The reconstructed image generating function 532 generates a reconstructed image at a predetermined time interval. The reconstructed image generating function 532 generates a reconstructed image from all projection data corresponding to the detection data of each acquisition view acquired during a predetermined time period (hereinafter referred to as a "first time period") (which may include projection data corresponding to the detection data of one or more acquisition views immediately before the first time period). The first time period (hereinafter referred to as the "first period") is a period during which a reconstructed image for display (hereinafter referred to as a "reconstructed image for display") with an image quality that allows confirmation of the scan status of the subject P being scanned by helical scanning in the X-ray CT device 1 can be generated. For example, the first period is a period during which a reconstructed image for display with an image quality equal to or higher than that of a reconstructed image generated in accordance with a fixed display frame rate can be generated in a real-time reconstruction function implemented in a conventional X-ray CT device to confirm the scan status of helical scanning in real time. In a conventional real-time reconstruction function, the reconstructed image to be displayed is switched at a period that matches the display frame rate, and therefore a reconstructed image is generated using a portion of projection data corresponding to the detection data of the acquisition view acquired during the period from the display of one reconstructed image to the display of the next reconstructed image. In contrast, the reconstructed image generating function 532 generates a reconstructed image for display using projection data corresponding to detection data of all acquisition views acquired during the first period, regardless of the cycle of the display frame rate. Therefore, the reconstructed image for display generated by the reconstructed image generating function 532 has higher image quality than the reconstructed image generated by a conventional real-time reconstruction function. For example, the reconstructed image for display generated by the reconstructed image generating function 532 has high spatial resolution in the body axis direction of the subject P (Z-axis direction shown in FIG. 1).

[0043] The reconstructed image generating function 532 is an example of a "first generating unit." The predetermined time (first time) is an example of a "first time." The reconstructed image for display generated by the reconstruction processing function 53 is an example of a "first reconstructed image data." The scan state is an example of a "shooting state."

[0044] The reconstructed image display processing function 534 generates a reconstructed image for display to be displayed on the display 42 from each reconstructed image for display generated by the reconstructed image generating function 532. At this time, the reconstructed image display processing function 534 dynamically adjusts the display frame rate according to the speed at which the top 33 on which the subject P is placed is moved during helical scanning (hereinafter referred to as the "top moving speed"). That is, the reconstructed image display processing function 534 determines the display frame rate to be synchronized with the movement of the top 33. Then, the reconstructed image display processing function 534 selects a reconstructed image for display generated by the reconstructed image generating function 532 according to the adjusted (determined) display frame rate and outputs the selected image to the display control function 56, thereby displaying the selected image on the display 42. More specifically, the reconstructed image display processing function 534 selects a reconstructed image for display that matches the timing of the display frame rate from the consecutive reconstructed images for display generated by the reconstructed image generating function 532 at each first time interval and outputs the selected image to the display control function 56. In other words, the reconstructed image display processing function 534 performs a thinning process to thin out, from successive reconstructed images for display, reconstructed images for display that do not match the timing of the display frame rate, and outputs the reconstructed images for display to the display control function 56. As a result, even if the movement speed of the top 33 is changed during an examination of the subject P in the X-ray CT apparatus 1 (for example, even if the movement speed of the top 33 is changed when scanning the chest and when scanning the abdomen of the subject P), the reconstructed images for display that represent the scanning status of the subject P can be displayed on the display 42. This allows the person performing the CT examination to check the scanning status in the X-ray CT apparatus 1 in real time and to determine whether the intended position of the subject P has been scanned and when to interrupt the scanning of the subject P.

[0045] The reconstructed image display processing function 534 is an example of a "second generation unit." The display frame rate is an example of a "second time." The reconstructed image for display that the reconstructed image display processing function 534 outputs to the display control function 56 is an example of "second reconstructed image data." The top board movement speed is an example of "top board movement speed." The thinning process is an example of "processing for selecting second reconstructed image data."

[0046] The reconstructed image saving processing function 536 generates a reconstructed image for saving (hereinafter referred to as a "reconstructed image for saving") by additionally performing a predetermined reconstruction process on each reconstructed image for display generated by the reconstructed image generating function 532. The predetermined reconstruction process additionally performed by the reconstructed image saving processing function 536 (hereinafter referred to as "additional process") is a process for improving the image quality of the reconstructed image for saving (improving image quality) using the reconstructed image for display. The additional process may be, for example, image processing or filtering. As the additional process, the reconstructed image saving processing function 536 may perform an image bundling process for bundling multiple consecutive reconstructed images for display to generate a single reconstructed image for saving. As a result, the image quality (spatial resolution) of the reconstructed image for saving generated by the reconstructed image saving processing function 536 is higher than the image quality (spatial resolution) of the reconstructed image for display generated by the reconstructed image generating function 532.

[0047] The reconstructed image saving processing function 536 may generate a reconstructed image for storage using, for example, a machine learning model generated by a learning function (machine learning function) using AI (Artificial Intelligence) in a computing device (not shown). The machine learning model is a trained model that has been trained in advance using, for example, a convolutional neural network (CNN) or a deep neural network (DNN) to output a reconstructed image for storage with improved image quality when a reconstructed image for display generated by the reconstructed image generating function 532 is input. The reconstructed image for storage with improved image quality is a reconstructed image for storage with image quality equivalent to a reconstructed image generated by an in-view reconstruction function implemented to generate a reconstructed image for storage with image quality suitable for use in diagnosis, for example, when a helical scan is performed using a conventional X-ray CT device. The reconstructed image saving processing function 536 obtains a reconstructed image for storage with improved image quality, for example, by inputting multiple reconstructed images for display generated by the reconstructed image generating function 532 into the machine learning model. The reconstructed image saving processing function 536 converts the reconstructed image for storage obtained by the machine learning model into a reconstructed image for storage that has undergone additional processing.

[0048] The additional processing in the reconstructed image saving processing function 536 is not limited to processing performed on the reconstructed image for display. For the purpose of further improving the image quality of the reconstructed image for storage, the reconstructed image saving processing function 536 may generate a reconstructed image for storage from all projection data corresponding to the detection data of each acquisition view acquired during a predetermined long period (hereinafter simply referred to as a "long period") longer than the first period during which the reconstructed image generating function 532 generates the reconstructed image for display (which may include projection data corresponding to the detection data of one or more acquisition views immediately before the predetermined long period). In this case, the predetermined long period is, for example, a period during which at least a reconstructed image for storage with image quality equivalent to that of a reconstructed image generated by a conventional in-view reconstruction function can be generated. In this case, the reconstructed image saving processing function 536 may generate a reconstructed image for storage by performing predetermined reconstruction processing equivalent to that of a conventional in-view reconstruction function on the projection data stored in the memory 41 in parallel with the reconstructed image generating function 532.

[0049] The reconstructed image storage processing function 536 is an example of a "third generation unit." A predetermined long period is an example of a "third time period." The reconstructed image for storage generated by the reconstructed image storage processing function 536 is an example of a "third reconstructed image data." For example, additional processing such as image processing and filtering is an example of an "additional reconstruction processing." A machine learning model is an example of a "trained model." Image bundling processing is an example of processing that "bundles first reconstructed image data to generate one third reconstructed image data." Processing aimed at further improving the image quality of the reconstructed image for storage is an example of processing that "generates third reconstructed image data reconstructed from projection data."

[0050] [Operation of the reconstruction processing function] Next, the operation of the reconstruction processing function 53 will be described. Fig. 3 is a diagram schematically showing an example of image reconstruction processing in a conventional X-ray CT device. Fig. 4 is a diagram schematically showing an example of image reconstruction processing in the reconstruction processing function 53 provided in the X-ray CT device 1 according to the embodiment. Figs. 3 and 4 also show a memory 41 that stores original projection data from which a reconstructed image is generated in the reconstruction processing function 53. Figs. 3 and 4 schematically show an example of how each reconstructed image is generated sequentially as time t passes.

[0051] First, for comparison, an example of the operation of generating a reconstructed image for display and storage in a conventional X-ray CT apparatus will be described with reference to FIG.

[0052] FIG. 3(a) schematically illustrates an example of the operation of a real-time reconstruction function implemented in a conventional X-ray CT system for checking the scan status of a helical scan in real time. The conventional real-time reconstruction function generates a display reconstructed image from projection data corresponding to detection data of each acquisition view acquired during a predetermined period, in accordance with the timing of image display (image switching timing) at a fixed display frame rate. The conventional real-time reconstruction function does not generate a display reconstructed image except when the image is switched at the display frame rate. FIG. 3(a) also schematically illustrates an example of the real-time reconstruction function sequentially generating seven display reconstructed images IMd (display reconstructed images IMd-1 to IMd-7) from projection data stored in memory 41 in accordance with the timing of image switching at the display frame rate. FIG. 3(a) also schematically illustrates periods Pn (hereinafter referred to as "image non-generation periods") Pn-1 to Pn-6 during which no display reconstructed images IMd are generated, which exist between the generation of each display reconstructed image IMd.

[0053] FIG. 3(b) shows a schematic diagram of an example of the operation of an in-view reconstruction function implemented to generate storage reconstructed images suitable for diagnosis when a helical scan is performed with a conventional X-ray CT system. The conventional in-view reconstruction function generates storage reconstructed images from all projection data corresponding to the detection data of each acquisition view acquired over a predetermined long period, which is longer than the predetermined period for generating display reconstructed images with the real-time reconstruction function. FIG. 3(b) shows a schematic diagram of an example of the in-view reconstruction function sequentially generating six storage reconstructed images IMs (storage reconstructed images IMs-1 to IMs-6) from the projection data stored in memory 41 over a predetermined long period. This ensures that the image quality of the storage reconstructed images IMs is higher than that of the display reconstructed images IMd, even with a conventional X-ray CT system. In FIG. 3(b), the width of the time axis direction (time width) of time t in the storage reconstructed images IMs indicates the high spatial resolution in the body axis direction of the subject P (the Z-axis direction shown in FIG. 1). High spatial resolution can also be said to be high image quality of the reconstructed images (here, reconstructed images for storage IMs).

[0054] In this way, in conventional X-ray CT systems, reconstructed images for display IMd are generated sequentially using the real-time reconstruction function, and reconstructed images for storage IMs are generated sequentially using the in-view reconstruction function. However, in conventional X-ray CT systems, the generation of reconstructed images for display IMd using the real-time reconstruction function and the generation of reconstructed images for storage IMs using the in-view reconstruction function are not performed simultaneously. In other words, the real-time reconstruction function and the in-view reconstruction function in conventional X-ray CT systems are functions that are performed exclusively.

[0055] Next, an example of the operation of the reconstruction processing function 53 to generate a reconstructed image for display IMd and a reconstructed image for storage IMs will be described with reference to Fig. 4. In Fig. 4 as well, the time width of each reconstructed image represents the level of image quality.

[0056] The reconstruction processing function 53 generates a reconstructed image for display IMd and a reconstructed image for storage IMs in the following procedure.

[0057] (Step 1): First, the reconstruction processing function 53 sequentially generates, by the reconstructed image generating function 532, reconstructed images for display at each first time interval that is unrelated to the timing of the display frame rate at which images are displayed in the X-ray CT device 1 (timing at which images are switched). FIG. 4(a) schematically shows an example of how the reconstructed image generating function 532 sequentially generates 25 reconstructed images for display IMd (reconstructed images for display IMd-1 to IMd-25) from the projection data stored in the memory 41. As can be seen from the example shown in FIG. 4(a), there is no period during which the reconstructed image generating function 532 does not generate reconstructed images for display IMd. As described above, each reconstructed image for display IMd generated by the reconstructed image generating function 532 has higher image quality than the reconstructed image for display IMd (see FIG. 3(a)) generated by the real-time reconstruction function implemented in conventional X-ray CT devices.

[0058] (Step 2): Next, the reconstruction processing function 53 dynamically adjusts (determines) the display frame rate to match the tabletop movement speed using the reconstructed image display processing function 534. Then, the reconstructed image display processing function 534 sequentially performs a thinning process to thin out the reconstructed images for display generated by the reconstructed image generation function 532 in accordance with the adjusted (determined) display frame rate, and outputs the reconstructed images to the display control function 56 in sequence to display 42. Figure 4(b) schematically shows an example of how the reconstructed image display processing function 534 sequentially outputs each of the reconstructed images for display IMd to the display control function 56 in the following order: reconstructed image for display IMd-1, reconstructed image for display IMd-5, reconstructed image for display IMd-9, reconstructed image for display IMd-13, reconstructed image for display IMd-17, reconstructed image for display IMd-21, and reconstructed image for display IMd-25. 4(b) schematically shows periods Pt during which the reconstructed images for display IMd are thinned out between the reconstructed images for display IMd output by the reconstructed image display processing function 534 to the display control function 56 (hereinafter referred to as "image thinning periods"). For example, in the image thinning period Pt-1 between the reconstructed images for display IMd-1 and the reconstructed images for display IMd-5, the reconstructed images for display IMd-2 to IMd-4 are thinned out. Similarly, in the image thinning periods Pt between the other two reconstructed images for display IMd, the corresponding reconstructed images for display IMd are thinned out.

[0059] (Step 3): Furthermore, the reconstruction processing function 53, using the reconstructed image saving processing function 536, sequentially performs additional processing on each of the reconstructed images for display generated by the reconstructed image generating function 532 to sequentially generate reconstructed images for storage. The reconstructed image saving processing function 536 performs additional processing (e.g., image processing, filter processing, etc.) excluding image bundling processing to generate the same number of reconstructed images for storage as the reconstructed images for display generated by the reconstructed image generating function 532. The reconstructed image saving processing function 536 performs additional processing including image bundling processing to generate reconstructed images for storage corresponding to the number of reconstructed images for display bundled together. Figure 4(c) schematically shows an example of how the reconstructed image saving processing function 536 performs additional processing including image bundling processing to sequentially generate six reconstructed images for storage IMs (reconstructed images for storage IMs-1 to IMs-6) similar to the reconstructed images for storage IMs generated by the in-view reconstruction function implemented in a conventional X-ray CT device (see Figure 3(b)). For example, the reconstructed image for storage IMs-1 is generated by the reconstructed image display processing function 534 performing image bundling processing to bundle consecutive reconstructed images for display IMd-1 to IMd-4 into one. Similarly, the other reconstructed images for storage IMs are generated by the reconstructed image display processing function 534 performing image bundling processing to bundle corresponding multiple reconstructed images for display IMd into one. As a result of the additional processing performed by the reconstructed image storage processing function 536, the image quality (spatial resolution) of the generated reconstructed image for storage IMs becomes higher than the image quality (spatial resolution) of the reconstructed image for storage IMs generated by the reconstructed image generation function 532. Also in FIG. 4(c), the width (time width) of the time axis direction of time t in the reconstructed image for storage IMs indicates that the spatial resolution in the body axis direction of the subject P (Z-axis direction shown in FIG. 1) is high (or this can be rephrased as high image quality).

[0060] In this way, in the reconstruction processing function 53, the reconstructed image generation function 532 sequentially generates reconstructed images IMd for display, the reconstructed image display processing function 534 thins out the reconstructed images IMd for display and sequentially outputs them to the display control function 56 for display on the display 42, and the reconstructed image storage processing function 536 performs additional processing on each reconstructed image IMd for display to sequentially generate reconstructed images IMs for storage.

[0061] In the above description of the operation of the reconstruction processing function 53, the sequential output of the reconstructed images for display IMd by the reconstructed image display processing function 534 to the display control function 56 and the sequential generation of the reconstructed images for storage IMs by the reconstructed image save processing function 536 have been described as being performed in this order, but the sequential output of the reconstructed images for display IMd to the display control function 56 and the sequential generation of the reconstructed images for storage IMs are performed simultaneously. In other words, the reconstruction processing function 53 performs steps 2 and 3 simultaneously. For this reason, the reconstruction processing function 53 may change the proportion of resources allocated to each of the processes of generating the reconstructed images for display by the reconstructed image generating function 532, the thinning process by the reconstructed image display processing function 534, and the additional process on the reconstructed images for display by the reconstructed image save processing function 536 (the generation process of the reconstructed images for storage). For example, by increasing the proportion of resources allocated to the reconstructed image generating function 532, the first period for generating a reconstructed image for display can be lengthened (the number of projection data corresponding to the detection data of the acquisition view used to generate the reconstructed image for display can be increased), thereby enabling the generated reconstructed image for display to have higher image quality. For example, by increasing the proportion of resources allocated to the reconstructed image display processing function 534, the display frame rate for outputting the reconstructed image for display to the display control function 56 can be increased (the amount of thinning of the reconstructed image for display can be adjusted). Even if the movement speed of the top 33 increases, the reconstructed image for display can be displayed following the movement of the top 33, ensuring continuity of the position of the subject P imaged in the reconstructed image for display. For example, by increasing the proportion of resources allocated to the reconstructed image saving processing function 536, the additional processing can be speeded up (the time until the reconstructed image for saving can be confirmed (diagnosed) after the end of scanning (imaging)) and the generated reconstructed image for saving can be further improved in image quality. By changing the proportion of resources allocated to each function of the reconstruction processing function 53, it is possible to achieve a balance (adjust the balance) between the image quality of the reconstructed image for display, the display frame rate when outputting the reconstructed image for display to the display control function 56 (displaying the reconstructed image for display on the display 42), and the image quality of the reconstructed image for storage that is generated.

[0062] The proportions of resources allocated to the reconstruction image generation function 532, the reconstruction image display processing function 534, and the reconstruction image saving processing function 536 included in the reconstruction processing function 53 may be changed, for example, depending on the load conditions of the X-ray CT apparatus 1, the console device 40, the processing circuit 50, and each hardware component corresponding to the reconstruction processing function 53. For example, the proportions of resources allocated to each function included in the reconstruction processing function 53 may be changed so as to adjust the balance of the load on each hardware component. The proportions of resources allocated to the reconstruction image generation function 532, the reconstruction image display processing function 534, and the reconstruction image saving processing function 536 included in the reconstruction processing function 53 may be set, for example, by the person performing the CT examination through an input operation on the input interface 43. In other words, the person performing the CT examination may change the proportions of resources allocated to each function included in the reconstruction processing function 53 depending on the purpose, intention, and preference of the CT examination.

[0063] As described above, in the X-ray CT apparatus 1 of the embodiment, the reconstructed image generating function 532 included in the reconstruction processing function 53 executed in the processing circuitry 50 in the console device 40 sequentially generates the reconstructed images for display IMd at a first time interval that is unrelated to the timing of the display frame rate at which images are displayed in the X-ray CT apparatus 1. Then, in the X-ray CT apparatus 1 of the embodiment, the reconstructed image display processing function 534 included in the reconstruction processing function 53 dynamically adjusts (determines) the display frame rate in accordance with the moving speed (top moving speed) of the tabletop 33, sequentially performs thinning processing on the reconstructed images for display IMd in accordance with the adjusted (determined) display frame rate, sequentially outputs the reconstructed images for display IMd to the display control function 56, and displays the reconstructed images for display IMd on the display 42. As a result, in the X-ray CT apparatus 1 of the embodiment, the person performing the CT examination can check the scan status in real time to determine whether the intended position of the subject P has been scanned in the helical scan, determine the timing to interrupt the scan of the subject P, and so on. In the X-ray CT device 1 of the embodiment, the display reconstructed image IMd is displayed on the display 42 at a display frame rate adjusted (determined) according to the tabletop movement speed, so that when the person performing the CT examination interrupts the scan of the subject P, the amount of deviation between the imaging position of the subject P at the time the scan was interrupted and the position of the stopped tabletop 33 can be reduced.

[0064] In the X-ray CT apparatus 1 of the embodiment, the reconstructed image storage processing function 536 included in the reconstruction processing function 53 sequentially performs additional processing on each of the reconstructed images for display IMd to sequentially generate reconstructed images for storage IMs. As a result, in the X-ray CT apparatus 1 of the embodiment, the person performing the CT examination can perform a suitable examination or diagnosis on the subject P by checking the reconstructed images for storage IMs that have suitable image quality for use in diagnosis and are equivalent to reconstructed images generated by the in-view reconstruction function implemented in conventional X-ray CT apparatuses.

[0065] Furthermore, in the X-ray CT apparatus 1 of the embodiment, the proportion of resources allocated to each process of the reconstructed image generation function 532, the reconstructed image display processing function 534, and the reconstructed image storage processing function 536 provided in the reconstruction processing function 53 may be changed. As a result, in the X-ray CT apparatus 1 of the embodiment, even if the processing load required of the reconstruction processing function 53 increases with future speed increases, for example, it is possible to balance the image quality of the reconstructed image to be displayed, the real-time display of the reconstructed image to be displayed, and the image quality of the reconstructed image to be stored by changing the proportion of resources allocated to each function provided in the reconstruction processing function 53.

[0066] In the X-ray CT apparatus 1 of the above-described embodiment, an example has been described in which each function of the reconstruction processing function 53 is executed by the processing circuit 50 included in the console device 40. However, each function of the reconstruction processing function 53 may be executed by other components, such as a processing circuit (not shown) included in the gantry device 10. The configuration, operation, and processing of the X-ray CT apparatus in this case only need to be equivalent to the configuration, operation, and processing of the X-ray CT apparatus 1 described in the above-described embodiment, and can be easily conceived based on the description of the above-described embodiment. Therefore, a detailed description of the configuration, operation, and processing of the X-ray CT apparatus in the case in which each function of the reconstruction processing function 53 is executed by other components included in the gantry device 10 will be omitted.

[0067] The above-described embodiment can be expressed as follows. An X-ray CT apparatus comprising: an acquisition unit that acquires detection data of the detector during imaging while a rotating unit having an X-ray tube and a detector that detects X-rays transmitted through a subject is rotating; and a reconstruction processing unit that generates reconstructed image data from projection data based on the detection data, processing circuitry; The processing circuitry generating first reconstructed image data reconstructed from the projection data at a first time interval; generating second reconstructed image data from the first reconstructed image data to be displayed on a display unit at second time intervals; generating third reconstructed image data having higher image quality than the second reconstructed image data at a third time interval; X-ray CT device.

[0068] According to at least one embodiment described above, an X-ray CT device (1) includes an acquisition unit (16) that acquires detection data of the detector during imaging while a rotating unit (17) having an X-ray tube (11) and a detector (15) that detects X-rays transmitted through a subject (P) is rotating, and a reconstruction processing unit (53) that generates reconstructed image data from projection data based on the detection data, wherein the reconstruction processing unit includes a first generation unit (532) that generates first reconstructed image data (reconstructed image for display IMd) reconstructed from the projection data at a first time interval, and a second generation unit (533) that generates reconstructed image data from the first reconstructed image data at a second time interval. By having a second generation unit (534) that generates second reconstructed image data to be displayed on the display unit (42) at intervals of 100 seconds, and a third generation unit (536) that generates third reconstructed image data (reconstructed images for storage IMs) of higher image quality than the second reconstructed image data at third time intervals, it is possible to provide an X-ray CT device, a control method for an X-ray CT device, and a program that display an image (reconstructed images for display IMd) that matches the movement of the top plate (33) and reduce the amount of deviation between the imaging position when scanning (imaging) is interrupted and the actual position of the top plate.

[0069] Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0070] 1···X-ray CT device, 10···Gantt device, 11···X-ray tube device, 12···Wedge, 13···Collimator, 14···X-ray high voltage device, 15···X-ray detector, 16···Data acquisition system (DAS), 17···Rotating frame, 18···Control device, 30···Couch device, 31···Base, 32···Couch drive device, 33···Top plate, 34···Support frame, 40···Console device, 41·· · Memory, 42·· Display, 43·· Input interface, 44·· Network connection circuit, 50·· Processing circuit, 51·· System control function, 52·· Preprocessing function, 53·· Reconstruction processing function, 532·· Reconstructed image generation function, 534·· Reconstructed image display processing function, 536·· Reconstructed image storage processing function, 54·· Image processing function, 55·· Scan control function, 56·· Display control function

Claims

1. An X-ray CT apparatus comprising: an acquisition unit that acquires detection data of the detector during imaging while a rotating unit having an X-ray tube and a detector that detects X-rays transmitted through a subject is rotating; and a reconstruction processing unit that generates reconstructed image data from projection data based on the detection data, The reconstruction processing unit a first generator that generates first reconstructed image data reconstructed from the projection data at a first time interval; a second generating unit that generates second reconstructed image data from the first reconstructed image data to be displayed on a display unit at second time intervals; a third generating unit that generates third reconstructed image data having higher image quality than the second reconstructed image data at a third time interval; An X-ray CT device comprising:

2. the first time period is a time period including the projection data for generating the first reconstructed image data having an image quality that allows confirmation of an imaging state of the subject during the imaging; the second generating unit generates the second reconstructed image data by selecting, from the first reconstructed image data, the first reconstructed image data that matches the second time interval. The X-ray CT apparatus according to claim 1.

3. the second generation unit determines the second time interval in accordance with a moving speed of a tabletop on which the subject is placed during the imaging, and generates the second reconstructed image data by selecting the first reconstructed image data that matches the determined second time interval. The X-ray CT apparatus according to claim 2.

4. the second generation unit determines the second time interval in accordance with the moving speed that is changed during the shooting. The X-ray CT apparatus according to claim 3.

5. the reconstruction processing unit changes a ratio of resources allocated to each of a process in which the first generating unit generates the first reconstructed image data, a process in which the second generating unit selects the second reconstructed image data, and a process in which the third generating unit generates the third reconstructed image data.

5. The X-ray CT apparatus according to claim 4.

6. the reconstruction processing unit changes the ratio of the resources allocated to each of the processes to a ratio that balances image quality of the first reconstructed image data, selection of the second reconstructed image data, and image quality of the third reconstructed image data.

6. The X-ray CT apparatus according to claim 5.

7. the third generating unit performs additional reconstruction processing on the first reconstructed image data to generate the third reconstructed image data. The X-ray CT apparatus according to any one of claims 1 to 6.

8. the third generation unit, when receiving the first reconstructed image data, generates the third reconstructed image data using a trained model that has been trained to output the third reconstructed image data; The X-ray CT apparatus according to any one of claims 1 to 6.

9. the third time period is longer than the first time period; the third generating unit generates one set of the third reconstructed image data by bundling a plurality of successive sets of the first reconstructed image data; The X-ray CT apparatus according to any one of claims 1 to 6.

10. the third time period is longer than the first time period; the third generation unit generates the third reconstructed image data reconstructed from the projection data. The X-ray CT apparatus according to any one of claims 1 to 6.

11. A control method for an X-ray CT apparatus including: an acquisition unit that acquires detection data of the detector during imaging while a rotating unit having an X-ray tube and a detector that detects X-rays transmitted through a subject is rotating; and a reconstruction processing unit that generates reconstructed image data from projection data based on the detection data, The computer of the X-ray CT device generating first reconstructed image data reconstructed from the projection data at a first time interval; generating second reconstructed image data from the first reconstructed image data to be displayed on a display unit at second time intervals; generating third reconstructed image data having higher image quality than the second reconstructed image data at a third time interval; A method for controlling an X-ray CT device.

12. A program executed in an X-ray CT apparatus including: an acquisition unit that acquires detection data of the detector during imaging while a rotating unit having an X-ray tube and a detector that detects X-rays transmitted through a subject is rotating; and a reconstruction processing unit that generates reconstructed image data from projection data based on the detection data, The computer of the X-ray CT device generating first reconstructed image data reconstructed from the projection data at a first time interval; generating second reconstructed image data from the first reconstructed image data to be displayed on a display unit at second time intervals; generating third reconstructed image data having higher image quality than the second reconstructed image data at a third time interval; program.

Images