Photon counting type X-ray imaging diagnostic apparatus and method for generating calibration data for pile-up correction

Abstract

To realize efficient pile-up correction in a photon counting-type X-ray image diagnostic apparatus.SOLUTION: A photon counting-type X-ray image diagnostic apparatus according to an embodiment comprises: an X-ray generation unit; a photon counting-type X-ray detector; a specification unit; a setting unit; a generation unit; and a calibration unit. The specification unit specifies a boundary condition that determines a range of a collection parameter set in which pile-up occurs on the basis of a plurality of detection data sets obtained by executing phantom imaging of detecting the X-ray applied to a phantom with the X-ray detector in the different collection parameter sets. The setting unit sets a margin range based on the boundary condition. The generation unit generates the plurality of collection parameter sets included in a range obtained by adding the margin range to the range of the collection parameter set. The calibration unit generates calibration data for pile-up correction on the basis of the plurality of detection data sets obtained by the plurality of collection parameter sets.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments disclosed in the present specification and drawings relate to a photon counting X-ray diagnostic imaging apparatus and a method for generating calibration data for pile-up correction.

Background Art

[0002] Conventionally, a photon counting computed tomography (PCCT) apparatus equipped with a Photon Counting Detector (PCD) is known.

[0003] In a PCD, pile-up occurs when the dose of incident X-rays is high, and there is a risk that the measured count value deviates from the true count value. For this reason, pile-up correction for correcting the detector response using calibration data for pile-up correction may be performed in some cases.

[0004] However, the calibration data for pile-up correction is generated, for example, based on a plurality of acquired data sets for a plurality of calibration conditions. Here, the calibration conditions include scan conditions such as exposure dose and tube voltage, and the known water equivalent thickness of the phantom to be scanned. For this reason, it is necessary to perform scanning for each of the plurality of calibration conditions, and there has been a problem that pile-up correction is inefficient.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0006] One of the problems that the embodiments disclosed herein aim to solve is to achieve efficient pile-up correction in a photon counting type X-ray imaging system. 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 each configuration shown in the embodiments described later can also be positioned as other problems. [Means for solving the problem]

[0007] The photon counting type X-ray imaging diagnostic apparatus according to this embodiment comprises an X-ray generation unit, a photon counting type X-ray detector, a specification unit, a setting unit, a generation unit, and a calibration unit. The X-ray generation unit generates X-rays. The X-ray detector detects the X-rays from the X-ray generation unit. The specification unit identifies boundary conditions that define the range of acquisition parameter sets in which pileup occurs, based on a plurality of detection datasets obtained by performing phantom imaging, in which X-rays irradiated onto a phantom are detected by the X-ray detector, with a plurality of different acquisition parameter sets. The setting unit sets a margin range based on the boundary conditions. The generation unit generates a plurality of acquisition parameter sets that are included in the range obtained by adding the margin range to the range of the acquisition parameter sets. The calibration unit generates calibration data for pileup correction based on a plurality of detection datasets obtained with the plurality of acquisition parameter sets.

[0008] The photon-counting type X-ray imaging apparatus according to the embodiment comprises an X-ray generating unit that generates X-rays and a photon-counting type X-ray detector that detects X-rays from the X-ray generating unit. The X-ray imaging apparatus generates calibration data for pile-up correction used to correct detection data obtained in imaging in which X-rays irradiated onto a subject are detected by the X-ray detector. The X-ray imaging apparatus comprises an acquisition unit, a collection unit, a calibration unit, and a generation unit. The acquisition unit acquires a first set of multiple acquisition parameters for generating the calibration data based on prior information. The collection unit obtains first detection data by performing phantom imaging in which X-rays irradiated onto a phantom are detected by the X-ray detector using the first set of multiple acquisition parameters. The calibration unit generates the calibration data based on the collected first detection data. The generation unit generates a second set of multiple acquisition parameters for use in phantom imaging to update the generated calibration data, based on the first detection data, the elapsed time since the first detection data was collected, and the usage status since the first detection data was collected. The first and second sets of multiple acquisition parameters are each control parameter sets of the X-ray imaging diagnostic apparatus for obtaining detection data by phantom imaging. In each of the first and second sets of multiple acquisition parameters, some acquisition parameter sets that do not cause pileup are excluded from the multiple acquisition parameter sets that can be set in the X-ray imaging diagnostic apparatus, and the thicker the phantom when obtaining the detection data, the more acquisition parameter sets are excluded from the multiple acquisition parameter sets that can be set in the X-ray imaging diagnostic apparatus.

[0009] The method for generating calibration data for pile-up correction according to the embodiment includes: identifying boundary conditions that define the range of collection parameter sets in which pile-up occurs, based on a plurality of detection datasets obtained by performing phantom imaging, in which X-rays irradiated onto a phantom are detected by an X-ray detector, with a plurality of different collection parameter sets; setting a margin range based on the boundary conditions; generating a plurality of collection parameter sets that are included in the range obtained by adding the margin range to the range of the collection parameter sets; and generating calibration data for pile-up correction based on a plurality of detection datasets obtained with the plurality of collection parameter sets.

[0010] The method for generating calibration data for pile-up correction according to the embodiment is a method for generating calibration data for pile-up correction used to correct detection data obtained in imaging in a photon-counting type X-ray imaging apparatus in which X-rays from an X-ray generator irradiated onto a subject are detected by a photon-counting type X-ray detector. The generation method includes: acquiring a first plurality of acquisition parameter sets for generating the calibration data based on prior information; obtaining first detection data by performing phantom imaging in which X-rays irradiated onto a phantom are detected by the X-ray detector using the first plurality of acquisition parameter sets; generating the calibration data based on the acquired first detection data; and generating a second plurality of acquisition parameter sets to be used in the phantom imaging for updating the generated calibration data, based on the first detection data, the elapsed time since the first detection data was acquired, and the usage status since the first detection data was acquired. The first and second plurality of acquisition parameter sets are each control parameter sets of the X-ray imaging apparatus for obtaining detection data by the phantom imaging. In each of the first and second sets of acquisition parameters, some acquisition parameter sets that do not cause pileup are excluded from the set of acquisition parameter sets that can be set in the X-ray imaging diagnostic device, and the thicker the phantom when obtaining the detection data, the more acquisition parameter sets are excluded from the set of acquisition parameter sets that can be set in the X-ray imaging diagnostic device. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 shows an example of the configuration of a positron emission computed tomography (PET) apparatus according to an embodiment. [Figure 2] Figure 2 is a diagram illustrating the identification of the pile-up generation boundary according to the embodiment. [Figure 3]Figure 3 is a diagram illustrating the setting of calibration conditions used to generate pile-up correction data according to the embodiment. [Figure 4] Figure 4 is a diagram illustrating the setting of calibration conditions used to generate pile-up correction data according to the embodiment. [Figure 5] Figure 5 is a diagram illustrating the setting of calibration conditions used to generate pile-up correction data according to the embodiment. [Figure 6] Figure 6 is a diagram illustrating the setting of calibration conditions used to generate pile-up correction data according to the embodiment. [Figure 7] Figure 7 is a diagram illustrating the setting of calibration conditions used to generate pile-up correction data according to the embodiment. [Figure 8] Figure 8 is a flowchart showing an example of pile-up correction processing according to the embodiment. [Modes for carrying out the invention]

[0012] The following describes a photon counting type X-ray imaging diagnostic apparatus and a method for generating calibration data for pile-up correction according to each embodiment, with reference to the drawings. In the following description, components having the same or substantially the same function as those previously described in the drawings are denoted by the same reference numerals, and are described again only when necessary. Furthermore, even when representing the same part, the dimensions and proportions may differ between drawings. Also, for example, from the viewpoint of ensuring the readability of the drawings, reference numerals are denoted only for major or representative components in the description of each drawing, and reference numerals may not be denoted for components having the same or substantially the same function.

[0013] In the embodiments described below, examples are given in which an information processing device configured to realize a method for generating calibration data for pile-up correction and / or a pile-up correction method using said calibration data is mounted on a photon counting type X-ray imaging diagnostic device equipped with a photon counting detector (PCD).

[0014] Furthermore, in the embodiments described below, a photon-counting type X-ray computed tomography (PCCT) system is used as an example of a photon-counting type X-ray imaging diagnostic device, but the invention is not limited to this. The information processing device according to each embodiment may be implemented by being mounted on other medical imaging diagnostic devices besides the X-ray CT system. In this case, the processor mounted on each medical imaging diagnostic device can implement the method for determining the raw data to be stored according to each embodiment by executing a program read from ROM or the like and loaded into RAM. Other medical imaging diagnostic devices may include various medical imaging diagnostic devices such as X-ray diagnostic devices, SPECT (Single Photon Emission Computed Tomography) devices, SPECT-CT devices which integrate a SPECT device and an X-ray CT device, PET (Positron Emission computed tomography) devices, and PET-CT devices which integrate a PET device and an X-ray CT device. In addition, other medical imaging diagnostic devices such as X-ray rotation angiography (Angiography) devices may be used. In other words, a cone-beam CT scanner, which rotates a C-arm in an X-ray diagnostic device to collect projected X-ray images, can also be used as another medical imaging diagnostic device in addition to an X-ray CT scanner.

[0015] For example, there are various types of X-ray CT scanners, such as third-generation CT and fourth-generation CT, but any type can be applied to each embodiment. Here, third-generation CT is a Rotate / Rotate-Type in which the X-ray tube and detector rotate together around the subject. Fourth-generation CT is a Stationary / Rotate-Type in which a large number of X-ray detection elements are fixed in a ring-shaped array, and only the X-ray tube rotates around the subject.

[0016] Furthermore, the information processing devices according to each embodiment are not limited to being mounted on medical imaging diagnostic equipment such as X-ray CT scanners, but may also be implemented as independent devices using a computer that has a processor such as a CPU (Central Processing Unit) and memory such as ROM (Read Only Memory) or RAM (Random Access Memory) as hardware resources. In this case, the processor mounted on the computer can implement the calibration data generation method and / or pile-up correction method according to each embodiment by executing a program read from ROM, etc., and loaded into RAM.

[0017] Figure 1 shows an example of the configuration of an X-ray CT apparatus 1 as a photon counting type X-ray imaging diagnostic apparatus according to an embodiment. The X-ray CT apparatus 1 irradiates the subject P with X-rays from the X-ray tube 11 and detects the irradiated X-rays with the X-ray detector 12. The X-ray CT apparatus 1 generates a CT image of the subject P based on the output from the X-ray detector 12.

[0018] As shown in Figure 1, the X-ray CT apparatus 1 includes a gantry 10, a couch 30, and a console 40. For convenience of explanation, a plurality of gantries 10 are depicted in Figure 1. The gantry 10 is a scanning device having a configuration for performing X-ray CT imaging on a subject P. The couch 30 is a transport device for placing the subject P to be subjected to X-ray CT imaging thereon and positioning the subject P. The console 40 is a computer that controls the gantry 10. For example, the gantry 10 and the couch 30 are installed in a CT examination room, and the console 40 is installed in a control room adjacent to the CT examination room. The gantry 10, the couch 30, and the console 40 are connected to each other in a wired or wireless manner so as to be capable of communicating with each other.

[0019] Note that the console 40 does not necessarily have to be installed in the control room. For example, the console 40 may be installed in the same room together with the gantry 10 and the couch 30. Alternatively, the console 40 may be incorporated into the gantry 10.

[0020] In the present embodiment, the rotation axis of the rotating frame 13 in the non-tilt state or the longitudinal direction of the top plate 33 of the couch 30 is defined as the Z-axis direction, the axial direction orthogonal to the Z-axis direction and horizontal to the floor surface is defined as the X-axis direction, and the axial direction orthogonal to the Z-axis direction and perpendicular to the floor surface is defined as the Y-axis direction.

[0021] As shown in Figure 1, the gantry 10 includes an X-ray tube 11, an X-ray detector 12, a rotating frame 13, an X-ray high-voltage device 14, a control device 15, a wedge 16, a collimator 17, and a data acquisition circuit (Data Acquisition System: DAS) 18.

[0022] The X-ray tube 11 is a vacuum tube having a cathode (filament) that generates thermoelectrons and an anode (target) that generates X-rays upon being struck by the thermoelectrons. The X-ray tube 10 uses the high voltage supplied from the X-ray high-voltage device 14 to irradiate thermoelectrons from the cathode toward the anode, thereby irradiating the subject P with X-rays.

[0023] Note that the hardware for generating X-rays is not limited to the X-ray tube 11. For example, instead of the X-ray tube 11, a fifth-generation system may be used to generate X-rays. The fifth-generation system includes a focus coil that focuses the electron beam generated from the electron gun, a deflection coil that deflects it electromagnetically, and a target ring that surrounds half of the subject P and generates X-rays when the deflected electron beam collides with it. Here, the hardware for generating X-rays is an example of an X-ray generation unit.

[0024] The X-ray detector 12 is a photon-counting type X-ray detector (PCD) that detects X-rays from the X-ray tube 11. The X-ray detector 12 detects X-rays irradiated from the X-ray tube 11 that have passed through the subject P and outputs an electrical signal corresponding to the detected X-ray dose to the DAS 18. The X-ray detector 12 has, for example, an array of X-ray detection elements arranged in the channel direction along a single arc centered on the focal point of the X-ray tube 11. The X-ray detector 12 has, for example, a structure in which multiple X-ray detection elements are arranged in the slice direction (column direction, row direction) in the channel direction.

[0025] As an example, the X-ray detector 12 comprises, for example, multiple detector modules, a collimator module, a single bias voltage generator, a common electrode, and a conductor. The multiple detector modules are arranged in the channel direction along a single arc centered on the focal point of the X-ray tube 11.

[0026] In each of the multiple detector modules, electrodes are provided on opposing surfaces of semiconductor crystals, such as CdTe (cadmium telluride) or CdZnTe (cadmium zinc telluride: CZT), and an electric field is generated by applying a bias voltage. In the X-ray detector 12, when radiation is absorbed by the crystal, electron-hole pairs are generated, and a signal is output as electrons move to the anode side (anode electrode (pixel electrode) side) and holes move to the cathode side (cathode electrode side).

[0027] Each of the multiple detector modules is provided with multiple anode electrodes and multiple cathode electrodes. In each of the multiple detector modules, the surface formed by the multiple anode electrodes corresponds to the anode surface. In each of the multiple detector modules, the surface formed by the multiple cathode electrodes corresponds to the cathode surface.

[0028] A single bias voltage generator generates a bias voltage applied between a cathode electrode and an anode electrode, both located on a semiconductor crystal. This single bias voltage generator is implemented as hardware, for example, by a single high-voltage power supply (bias power supply). A common electrode is electrically connected to the single bias voltage generator and extends in the channel direction. This common electrode is implemented, for example, by a busbar, which is a metal conductive rod. For the purposes of this explanation, the common electrode will be referred to as a busbar.

[0029] The conductor electrically connects the busbar to the cathode electrode of the semiconductor crystal in each of the multiple detector modules. The outputs from the multiple anode electrodes may be combined as needed, depending on the imaging conditions for the subject P or instructions from the user via the input interface 43. For the sake of detail, the outputs from the multiple anode electrodes will be described below assuming that each is processed independently as an output corresponding to a pixel.

[0030] Each of the multiple anode electrodes (hereinafter referred to as the detection element) outputs one pulse of electrical signal (analog signal) each time an X-ray photon is incident on it. By counting the number of electrical signals (pulses), it is possible to count the number of X-ray photons incident on each detection element. Furthermore, by performing various calculations on this signal, it is possible to measure the energy value of the X-ray photon that caused the output of that signal.

[0031] In addition to the detection element described above, the X-ray detector 12 has multiple application-specific integrated circuits (hereinafter referred to as ASICs (Application Specific Integrated Circuits)) connected to the detection element to count the X-ray photons detected by the detection element. The ASIC counts the number of X-ray photons incident on the detection element by measuring the "number of pulses" output by the detection element. The ASIC also measures the energy of the counted X-ray photons by performing calculations based on the "magnitude (amount of charge)" of each pulse. Furthermore, the ASIC outputs the X-ray photon counting result as digital data to the DAS 18.

[0032] The collimator module comprises a collimator plate and a collimator frame. A conductor is attached to the surface of the collimator module facing the semiconductor crystal. The collimator plate is located on the radiation incident side of the semiconductor crystal. The collimator plate is located between two anode electrodes and is arranged at least in the channel direction. Specifically, the collimator plate is positioned on the X-ray incident side of the cathode electrode. More specifically, multiple collimator plates are arranged along the channel direction at positions facing each other across the semiconductor crystal between two adjacent anode electrodes among a plurality of anode electrodes.

[0033] Furthermore, the collimator plate may have multiple scattered radiation removal sections arranged along a column direction (slice direction) perpendicular to the channel direction. The collimator plate is composed of, for example, an X-ray shielding plate that has the function of absorbing scattered X-rays, and is also called an anti-scatter grid (ASG). Depending on the dimensions in which it is arranged, the ASG may also be called a one-dimensional collimator, a two-dimensional collimator, or simply a grid.

[0034] The collimator frame supports the multiple collimator plates. The collimator frame supports the collimator plates while avoiding the radiation incident surface of the semiconductor crystal. Busbars may be provided at both ends of the collimator frame in the column direction. The busbars may be placed between the collimator frame and the multiple detector modules. Alternatively, the busbars may be placed at both ends of the semiconductor crystal in the column direction, without contact with the semiconductor crystal.

[0035] The X-ray detector 12 may be an indirect conversion type detector having, for example, a grid, a scintillator array, and a photosensor array. The scintillator array has multiple scintillators. The scintillators have scintillator crystals that output light in an amount corresponding to the amount of incident X-rays. The grid is arranged on the X-ray incident surface side of the scintillator array and has an X-ray shielding plate that has the function of absorbing scattered X-rays. The grid may also be called a collimator (one-dimensional collimator or two-dimensional collimator). The photosensor array has the function of converting the amount of light from the scintillators into an electrical signal. As a photosensor, for example, a Si-based photomultiplier tube (SiPM) can be used.

[0036] The rotating frame 13 is an annular frame that supports the X-ray tube 11 and the X-ray detector 12 opposite each other and rotates the X-ray tube 11 and the X-ray detector 12 by a control device 15, which will be described later. The opening 19 of the rotating frame 13 is set to define the field of view (FOV). For example, the rotating frame 13 is a casting made of aluminum. In addition to the X-ray tube 11 and the X-ray detector 12, the rotating frame 13 can also support an X-ray high-voltage device 14, a wedge 16, a collimator 17, and a DAS 18, etc. Furthermore, the rotating frame 13 can also support various other components not shown in Figure 1.

[0037] The X-ray high-voltage device 14 includes a high-voltage generator and an X-ray control device. The high-voltage generator has an electrical circuit including a transformer and a rectifier, and generates the high voltage applied to the X-ray tube 11 and the filament current supplied to the X-ray tube 11. The X-ray control device controls the output voltage according to the X-rays irradiated by the X-ray tube 11. The high-voltage generator may be of the transformer type or the inverter type. The X-ray high-voltage device 14 may be installed on the rotating frame 13 within the stand 10, or on a fixed frame (not shown) within the stand 10. The fixed frame is a frame that rotatably supports the rotating frame 13.

[0038] The control device 15 includes a drive mechanism such as a motor and actuator, and a processing circuit having a processor and memory for controlling this drive mechanism. The control device 15 receives input signals from the input interface 43 and an input interface provided on the frame 10, and controls the operation of the frame 10 and the bed 30. Examples of operation control by the control device 15 include controlling the rotation of the rotating frame 13, controlling the tilt of the frame 10, and controlling the operation of the bed 30. The control of the frame 10 is achieved by the control device 15 rotating the rotating frame 13 around an axis parallel to the X-axis direction based on the tilt angle information input by the input interface attached to the frame 10. The control device 15 may be provided on the frame 10 or on the console 40.

[0039] The wedge 16 is a filter for adjusting the amount of X-rays irradiated from the X-ray tube 11. Specifically, the wedge 16 is a filter that transmits and attenuates the X-rays irradiated from the X-ray tube 11 so that the X-rays irradiated from the X-ray tube 11 to the subject P have a predetermined distribution. For example, the wedge 16 is a wedge filter or a bow-tie filter, and is constructed by processing aluminum or the like to have a predetermined target angle and thickness.

[0040] The collimator 17 limits the irradiation range of X-rays that have passed through the wedge 16. The collimator 17 slidably supports multiple lead plates that shield the X-rays and adjusts the shape of the slit formed by the multiple lead plates. The collimator 17 is sometimes called an X-ray diaphragm.

[0041] The DAS18 reads an electrical signal from the X-ray detector 12 corresponding to the X-ray dose detected by the X-ray detector 12. The DAS18 amplifies the read electrical signal and integrates (adds) the electrical signal over the viewing period to collect detection data having a digital value corresponding to the X-ray dose over the viewing period. The detection data is called projection data. The DAS18 is implemented, for example, by an application-specific integrated circuit (ASIC) equipped with circuit elements capable of generating projection data. The projection data is transmitted to the console 40 via a non-contact data transmission device or the like. Here, the DAS18 is an example of a detection unit.

[0042] The detection data generated by DAS18 is transmitted via optical communication from a transmitter equipped with a light-emitting diode (LED) on the rotating frame 13 to a receiver equipped with a photodiode on the non-rotating part of the base 10 (for example, the fixed frame; not shown in Figure 1), and then forwarded to the console 40. The method of transmitting the detection data from the rotating frame 13 of the rotating part to the non-rotating part of the base 10 is not limited to the aforementioned optical communication; any non-contact data transfer method may be used.

[0043] The patient bed 30 is a device for placing and moving the subject P to be scanned. The patient bed 30 has a base 31, a patient bed drive device 32, a top plate 33, and a support frame 34. The base 31 is a housing that supports the support frame 34 so that it can move in the vertical direction. The patient bed drive device 32 is a drive mechanism that moves the top plate 33 on which the subject P is placed in the longitudinal direction of the top plate 33. The patient bed drive device 32 includes a motor and actuators, etc. The top plate 33 is a plate on which the subject P is placed. The top plate 33 is provided on the upper surface of the support frame 34. The top plate 33 can protrude from the patient bed 30 toward the frame 10 so that the entire body of the subject P can be photographed. The top plate 33 is made of, for example, carbon fiber reinforced plastic (CFRP) which has good X-ray transparency and physical properties such as rigidity and strength. Also, for example, the inside of the top plate 33 is hollow. The support frame 34 supports the top plate 33 so that it can move in the longitudinal direction of the top plate 33. The bed drive device 32 may also move the support frame 34 in the longitudinal direction of the top plate 33 in addition to the top plate 33.

[0044] The console 40 includes a memory 41, a display 42, an input interface 43, and a processing circuit 44. Data communication between the memory 41, the display 42, the input interface 43, and the processing circuit 44 is performed via a bus (BUS). Although the console 40 is described separately from the mounting base 10, the mounting base 10 may include the console 40 or some of its components.

[0045] Memory 41 can be implemented using, for example, semiconductor memory elements such as ROM, RAM, or flash memory, or a hard disk or optical disc. For example, memory 41 stores projection data and reconstructed image data. Also, for example, memory 41 stores various programs. Also, for example, memory 41 stores raw data with flag information (described later) attached, or raw data that has been determined to be retained. The storage area of ​​memory 41 may be located within the X-ray CT apparatus 1, or it may be located in an external storage device connected via a network. Here, memory 41 is an example of a storage unit.

[0046] The display 42 displays various types of information. For example, the display 42 displays medical images (CT images) generated by the processing circuit 44, or a GUI (Graphical User Interface) for receiving various operations from the operator. Various types of displays can be used as the display 42 as appropriate. For example, a liquid crystal display (LCD), a cathode ray tube (CRT) display, an organic electroluminescent display (OLED), or a plasma display can be used as the display 42.

[0047] The display 42 may be installed anywhere in the control room. Alternatively, the display 42 may be installed on the stand 10. Furthermore, the display 42 may be a desktop type, or it may consist of a tablet terminal or the like that can communicate wirelessly with the console 40. Also, one or more projectors may be used as the display 42. Here, the display 42 is just one example of a display unit.

[0048] The input interface 43 receives various input operations from the operator and converts the received input operations into electrical signals, which are then output to the processing circuit 44. For example, the input interface 43 receives data acquisition conditions when collecting projection data, reconstruction conditions when reconstructing CT images, and image processing conditions when generating post-processed images from CT images from the operator.

[0049] The input interface 43 can be, for example, a mouse, keyboard, trackball, switch, button, joystick, touchpad, or touch panel display, as appropriate. However, in this embodiment, the input interface 43 is not limited to those equipped with these physical operating components. 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 this electrical signal to a processing circuit 44 is also included as an example of the input interface 43. Furthermore, the input interface 43 may be provided on the stand 10. In addition, the input interface 43 may consist of a tablet terminal or the like that can communicate wirelessly with the console 40 main unit. Here, the input interface 43 is an example of an input unit.

[0050] The processing circuit 44 controls the operation of the entire X-ray CT apparatus 1. The processing circuit 44 has a processor and memory such as ROM or RAM as hardware resources. The processing circuit 44 executes system control functions 441, image generation functions 442, image processing functions 443, boundary identification functions 444, margin setting functions 445, condition setting functions 446, calibration functions 447, and display control functions 448, etc., using a processor that executes programs loaded into memory. Here, the processing circuit 44 is an example of a processing unit.

[0051] In the system control function 441, the processing circuit 44 controls various functions of the X-ray CT apparatus 1 based on input operations received from the operator via the input interface 43. For example, the system control function 441 controls the CT scan performed on the gantry 10. The processing circuit 44 acquires detection data obtained from the CT scan. As an example, the processing circuit 44 acquires multiple detection data sets by performing phantom imaging under multiple different calibration conditions (acquisition parameter sets). Phantom imaging is performed by detecting X-rays irradiated onto the phantom with the X-ray detector 12. The calibration conditions are the control parameter sets of the X-ray CT apparatus 1 for obtaining detection data through phantom imaging. Here, the processing circuit 44 that realizes the system control function 441 is an example of an acquisition unit.

[0052] In the image generation function 442, the processing circuit 44 generates data by applying preprocessing such as logarithmic transformation, offset correction, inter-channel sensitivity correction, and beam hardening correction to the detection data output from the DAS 18. The processing circuit 44 stores the generated data in the memory 41. Note that the data before preprocessing (detection data) and the data after preprocessing are sometimes collectively referred to as projection data. The processing circuit 44 generates CT image data by performing reconstruction processing on the generated projection data (projection data after preprocessing) using methods such as filtered back projection (FBP method) and iterative reconstruction. The processing circuit 44 stores the reconstructed CT image data in the memory 41. The projection data generated from the counting results obtained from photon counting CT contains information on the energy of X-rays attenuated by passing through the subject P. Therefore, the processing circuit 44 can, for example, reconstruct X-ray CT image data for a specific energy component. Furthermore, the processing circuit 44 can, for example, reconstruct X-ray CT image data for each of multiple energy components.

[0053] Furthermore, in the image generation function 442, the processing circuit 44 can, for example, assign a color tone corresponding to the energy component to each pixel of the X-ray CT image data for each energy component, and generate image data by superimposing multiple X-ray CT image data that are color-coded according to the energy component. In addition, the processing circuit 44 can, for example, use the material's unique K absorption edge to generate image data that enables the identification of the material. Other image data that the processing circuit 44 can generate include monochromatic X-ray image data, density image data, and effective atomic number image data.

[0054] In the image processing function 443, the processing circuit 44 converts the CT image data generated by the image generation function 442 into tomographic data of an arbitrary cross-section or 3D image data using known methods, based on input operations received from the operator via the input interface 43. For example, the processing circuit 44 applies 3D image processing such as volume rendering, surface rendering, image value projection processing, MPR (Multi-Planar Reconstruction) processing, and CPR (Curved MPR) processing to the CT image data to generate rendered image data in an arbitrary viewpoint direction. Note that the generation of 3D image data, such as rendered image data in an arbitrary viewpoint direction, i.e., volume data, may be performed directly by the image generation function 442. Here, the processing circuit 44 that implements the image generation function 442 and the image processing function 443 is an example of an image processing unit.

[0055] In the boundary identification function 444, the processing circuit 44 identifies the pile-up occurrence boundary. The pile-up occurrence boundary is a boundary condition that defines the range of acquisition parameter sets in which a pile-up occurs. As an example, the processing circuit 44 identifies the pile-up occurrence boundary based on multiple detection datasets obtained by performing phantom imaging with multiple different acquisition parameter sets. Here, the processing circuit 44 that realizes the boundary identification function 444 is an example of an identification unit.

[0056] In the margin setting function 445, the processing circuit 44 sets a margin range based on the pile-up generation boundary. For example, the processing circuit 44 sets the margin range on the side of the pile-up generation boundary where pile-up does not occur, among the multiple acquisition parameter sets that can be set in the X-ray CT apparatus 1. For example, the processing circuit 44 determines the size of the margin range based on at least one of the following: fluctuations of the X-ray detector 12, changes in response over time, quantum noise of X-ray generation, and charge sharing. Here, the processing circuit 44 that realizes the margin setting function 445 is an example of a setting unit.

[0057] In the condition setting function 446, the processing circuit 44 sets calibration conditions (acquisition parameter sets) to obtain detection data for generating calibration data for pile-up correction. For example, the processing circuit 44 generates multiple acquisition parameter sets (calibration conditions) that are included in a range that adds a margin range to the range of acquisition parameter sets in which pile-up occurs. In other words, as calibration conditions, some calibration conditions in which pile-up does not occur are excluded from the multiple calibration conditions that can be set in the X-ray CT apparatus 1. For example, the processing circuit 44 generates acquisition parameter sets more densely in the range where the contribution to the image based on the detection data after pile-up correction is high compared to other ranges. For example, the processing circuit 44 generates acquisition parameter sets more densely in the range where the tendency of the pile-up occurrence boundary changes compared to other ranges. For example, the processing circuit 44 excludes more acquisition parameter sets from the multiple acquisition parameter sets that can be set in the X-ray CT apparatus 1 the thicker the phantom when obtaining the detection dataset. Here, the processing circuit 44 that realizes the condition setting function 446 is an example of a generation unit.

[0058] In the calibration function 447, the processing circuit 44 generates calibration data for pile-up correction based on multiple detection datasets obtained from multiple acquisition parameter sets generated by the condition setting function 446. Here, the processing circuit 44 that implements the calibration function 447 is an example of a calibration unit.

[0059] In the display control function 448, the processing circuit 44 displays an image on the display 42 based on various image data generated by the image processing function 443. The images displayed on the display 42 include color images according to the embodiment. The images displayed on the display 42 also include CT images based on CT image data, cross-sectional images based on cross-sectional image data of an arbitrary cross-section, and rendering images of an arbitrary viewpoint direction based on rendering image data of an arbitrary viewpoint direction. The images displayed on the display 42 also include images for displaying operation screens and images for displaying notifications and warnings to the operator.

[0060] Furthermore, each of the functions 441 to 448 is not limited to being implemented in a single processing circuit. A processing circuit 44 may be constructed by combining multiple independent processors, with each processor executing its respective program to realize each of the functions 441 to 448. Here, each of the functions 441 to 448 may be implemented by being appropriately distributed or integrated across one or more processing circuits.

[0061] Although console 40 has been described as a single console that performs multiple functions, it is also acceptable for multiple functions to be performed by separate consoles. For example, the functions of the processing circuits 44 for image generation function 442, image processing function 443, boundary identification function 444, margin setting function 445, condition setting function 446, and calibration function 447 may be distributed among multiple consoles.

[0062] Furthermore, part or all of the processing circuit 44 may not be included in the console 40, but may also be included in an integrated server that performs processing on detection data acquired by multiple medical imaging diagnostic devices in a unified manner.

[0063] At least one of the following processes—calibration data generation, post-processing, pile-up correction, and display—may be performed on either the console 40 or an external workstation. Alternatively, both the console 40 and the workstation may perform the processing simultaneously. As a workstation, a computer with hardware resources such as a processor that implements the functions corresponding to each process, and memory such as ROM or RAM, can be used as appropriate.

[0064] In the reconstruction of X-ray CT image data, either the full-scan reconstruction method or the half-scan reconstruction method may be applied. For example, in the image generation function 442, the processing circuit 44 uses projection data for a full 360 degrees around the subject P when using the full-scan reconstruction method. When using the half-scan reconstruction method, the processing circuit 44 uses projection data for 180 degrees plus the fan angle. For the sake of simplicity, in the following explanation, the processing circuit 44 will be assumed to use the full-scan reconstruction method, which reconstructs the image using projection data for a full 360 degrees around the subject P.

[0065] Furthermore, the technology according to this embodiment can be applied to both single-tube X-ray computed tomography (CT) systems and so-called multi-tube X-ray computed tomography (CT) systems, which have multiple pairs of X-ray tubes and detectors mounted on a rotating ring.

[0066] Furthermore, the technology according to this embodiment is also applicable to an X-ray CT apparatus 1 configured to perform dual-energy imaging. In this case, the X-ray high-voltage device 14 can alternately switch the energy spectrum of the X-rays emitted from the X-ray tube 11 by, for example, high-speed switching of two voltage values. In other words, the X-ray CT apparatus 1 is configured to collect projection data in each acquisition view while modulating the tube voltage at timings according to the control signal for tube voltage modulation. By imaging the subject with different tube voltages, the contrast of the density in the CT image can be improved based on the energy permeability of the material for each X-ray energy spectrum.

[0067] Furthermore, the X-ray CT apparatus 1 according to this embodiment may be configured as an upright CT. In this case, instead of moving the tabletop 33, a patient support mechanism is provided that supports the upright subject P and is configured to move along the rotation axis of the rotating part of the stand 10. Also, the X-ray CT apparatus 1 according to this embodiment may be configured as a mobile CT in which the stand 10 and the patient table 30 are movable.

[0068] Here, a method for generating calibration data for pile-up correction, which is implemented by the X-ray CT apparatus 1 as a photon counting type X-ray imaging diagnostic apparatus according to this embodiment, will be described in more detail with reference to the drawings.

[0069] (Regarding the identification of pile-up boundaries) Figures 2 and 3 are diagrams illustrating the identification of the pile-up generation boundary B according to the respective embodiments. In the graphs of Figures 2 and 3, the vertical axis and horizontal axis represent the equivalent water thickness (μ) and the exposure dose (mA), respectively.

[0070] Here, the radiation dose is an example of the scan conditions for the scan from which the acquired data is obtained, and is at least 1 within the range that can be set in the X-ray CT apparatus 1. The water equivalent thickness is the water equivalent thickness of the phantom used in the scan from which the calibration data is obtained, and is known information. Hereafter, the scan from which the calibration data is obtained may also be referred to as phantom imaging or calibration scan.

[0071] In PCD (Plane Controlled Diode) scanning, a phenomenon called pile-up occurs when the velocity of incident photons is faster than the detector's measurement velocity, resulting in a breakdown of input-output linearity. Therefore, pile-up correction is performed by scanning each of the multiple phantoms corresponding to multiple water equivalent thicknesses under multiple scan conditions to generate calibration data, and then calibrating the CT value by comparing the obtained acquired data with the calibration data (known information).

[0072] For example, calibration data for pile-up correction is a correction table generated using methods such as regression analysis or EM algorithms with multiple collected data for multiple calibration conditions. Here, the calibration conditions include scan conditions such as exposure dose and tube voltage, and the known water equivalent thickness of the phantom being scanned. In other words, calibration data for pile-up correction is information that shows the dependence of water equivalent thickness on exposure dose.

[0073] However, if the calibration conditions include conditions where the detector characteristics do not change depending on the exposure dose, i.e., conditions where pile-up does not occur, then a calibration scan will also be performed for the region R1 where pile-up does not occur. As a result, it is necessary to perform a calibration scan for each of the multiple calibration conditions, which leads to the problem of inefficient pile-up correction, including the generation of calibration data.

[0074] Therefore, the generation of calibration data for pile-up correction according to this embodiment includes identifying the pile-up occurrence boundary B. For example, in the boundary identification function 444, the processing circuit 44 identifies the pile-up occurrence boundary B. As shown in Figure 2, the pile-up occurrence boundary B is the boundary between the region R1 of calibration conditions in which pile-ups occur and the region R2 of calibration conditions in which pile-ups do not occur.

[0075] As an example, in the boundary identification function 444, the processing circuit 44 monitors the count trend of the X-ray detector 12 while changing the exposure dose and the equivalent water thickness to acquire the pile-up occurrence boundary. For example, as illustrated in Figure 2 as calibration condition C (C1, C2, ... CN: N is an arbitrary natural number), the processing circuit 44 monitors the count trend of the X-ray detector 12 at multiple equivalent water thicknesses for arbitrary exposure doses and identifies the pile-up occurrence boundary B. Alternatively, the processing circuit 44 may monitor the count trend of the X-ray detector 12 at multiple exposure doses for arbitrary equivalent water thicknesses and identify the pile-up occurrence boundary B.

[0076] Furthermore, when identifying the pileup boundary B, if calibration scans are performed with numerous calibration conditions, many calibration scans will also be performed on the calibration conditions of region R1 where pileups do not occur. For this reason, in the boundary identification function 444, the processing circuit 44 performs many calibration scans on the pileup initiation region R31 and the region R32 where the pileup initiation trend changes, and appropriately interpolates the other parts.

[0077] Furthermore, in the boundary identification function 444, the processing circuit 44 may identify the pile-up boundary B not only using data acquired by phantom imaging, but also using simulation results based on the performance of the measurement speed of the X-ray detector 12.

[0078] (Regarding setting the margin range) Figure 4 is a diagram illustrating the setting of calibration conditions used to generate pile-up correction data according to the embodiment. In the graph of Figure 4, the vertical axis and horizontal axis represent the equivalent water thickness and exposure dose (mA), respectively.

[0079] In the margin setting function 445, the processing circuit 44 sets a margin range R4 with respect to the identified pileup generation boundary B. The processing circuit 44 sets the margin range R4 on the side of the pileup generation boundary B where pileup does not occur, R1. The processing circuit 44 determines the size of the margin range R4 based on the fluctuations of the X-ray detector 12, changes in response over time, quantum noise of X-ray generation, the effects of charge sharing, etc.

[0080] The fluctuations of the X-ray detector 12 and the changes in its response over time are determined based on statistical values ​​such as the median and mean values ​​of the variations between multiple scans and the variations between multiple detection elements. Predefined values ​​(variation data) for these fluctuations and variations in response over time may be stored in memory 41 or the like. The quantum noise of X-ray generation is calculated, for example, based on the exposure dose (mA). The charging noise is calculated, for example, based on the geometry of the X-ray detector 12 and the exposure dose (mA).

[0081] The size of the margin range R4 may be determined based on measured values, simulation results, or a combination of these.

[0082] The size of the margin range R4 may be the same for each exposure dose, as illustrated in Figure 4, or it may vary depending on the exposure dose. For example, the margin range R4 may be larger in the pile-up initiation region R31 and the region R32 where the tendency for pile-up occurrence changes compared to other regions.

[0083] In Figure 4, the pile-up boundary B is represented by a single straight line, but this is not the only representation. For example, as illustrated in Figure 3, the pile-up boundary B may be represented by a combination of two or more straight lines.

[0084] (Regarding the arrangement of calibration conditions) Figures 5 to 7 are diagrams illustrating the setting of calibration conditions used to generate pile-up correction data according to each embodiment. In the graphs in Figures 5 to 7, the vertical axis and horizontal axis represent the equivalent water thickness and exposure dose (mA), respectively.

[0085] In the condition placement function 446, the processing circuit 44 places the calibration conditions for the calibration scan within the region R2 where pileup occurs plus the margin range R4. As shown in Figures 5 to 7, the calibration conditions (multiple acquisition parameter sets) for the calibration scan that are placed exclude more acquisition parameter sets from the multiple acquisition parameter sets that can be set in the X-ray CT device 1 as the thickness of the phantom (water equivalent thickness) when obtaining the detection dataset increases.

[0086] In the condition placement function 446, the processing circuit 44 places the calibration conditions C for the calibration scan on at least the boundary between the region R1 where pileup does not occur and the margin range R4 (hereinafter referred to as the first placement boundary).

[0087] Furthermore, in the condition placement function 446, the processing circuit 44 places the calibration conditions C for the calibration scan on at least the boundary where the equivalent water thickness is zero (or minimum) among the peripheral parts of the pile-up region R2 (hereinafter referred to as the second placement boundary).

[0088] As an example, in the condition placement function 446, the processing circuit 44 equally divides the space between the first placement boundary and the second placement boundary, as illustrated in Figure 5, and places the calibration conditions C of the calibration scan at each division point (sample point). In other words, the processing circuit 44 places the same number of calibration conditions C for each exposure dose.

[0089] As an example, in the condition placement function 446, the processing circuit 44 divides the space between the first placement boundary and the second placement boundary into a mesh, as illustrated in Figure 6, and places the calibration conditions C of the calibration scan at each division point (sample point). In other words, the processing circuit 44 places the calibration conditions C so that the intervals between each sample point are equal.

[0090] As an example, in the condition placement function 446, the processing circuit 44 randomly sets sample points in the region between the first placement boundary and the second placement boundary, as illustrated in Figure 7, and places the calibration condition C of the calibration scan at each set sample point.

[0091] As an example, in the conditional placement function 446, the processing circuit 44 changes the placement density of sample points in the region between the first placement boundary and the second placement boundary according to their contribution to the image. Specifically, the processing circuit 44 places sample points more densely the greater their contribution to the image. Here, the contribution to the image increases as you move towards the lower right of the graph (where the exposure dose is high and the water equivalent thickness is low), for example, in the examples shown in Figures 5 to 7.

[0092] As an example, in the condition placement function 446, the processing circuit 44 places sample points more densely in the region between the first placement boundary and the second placement boundary, specifically in the pile-up generation start region R31 and the region R32 where the tendency of pile-up generation changes, i.e., the range of calibration conditions where the tendency of the pile-up generation boundary B changes.

[0093] The number of sample points mentioned above is just one example; it should be determined appropriately according to the required image quality and interpolation accuracy.

[0094] (Regarding the generation of calibration data) In the calibration function 447, the processing circuit 44 obtains data through multiple calibration scans for multiple calibration conditions located in the region R2 where pileup occurs plus a margin range R4. The processing circuit 44 also generates a correction table (calibration data) using the multiple data obtained for the multiple calibration conditions, employing methods such as regression analysis and the EM algorithm.

[0095] Furthermore, as calibration conditions, the tube voltage (kV) may be used instead of, or in addition to, the exposure dose, or a combination of the wedge type 16 and FOV may be used. In these cases as well, the pile-up generation boundary B is identified and calibration conditions are set while changing the tube voltage, the wedge type 16, and the FOV within the range that can be set in the X-ray CT apparatus 1, as in the example described above.

[0096] Furthermore, calibration data for pile-up correction can be generated for each exposure dose, water equivalent thickness, tube voltage, wedge type 16 and FOV combination, X-ray detector 12 elements, X-ray detector 12 channels, and X-ray detector 12 segments.

[0097] Here, the method for generating calibration data for pile-up correction and the flow of the pile-up correction method using said calibration data, which are realized by the X-ray CT apparatus 1 as a photon counting type X-ray imaging diagnostic apparatus according to this embodiment, will be described in more detail with reference to the drawings.

[0098] Figure 8 is a flowchart showing an example of pile-up correction processing according to the embodiment.

[0099] As an example, the method for generating calibration data for pile-up correction is realized by a generation process performed by the X-ray CT apparatus 1. As an example, the pile-up correction method is realized by a correction process performed by the X-ray CT apparatus 1.

[0100] In the boundary identification function 444, the processing circuit 44 scans while changing the calibration conditions to identify the pile-up occurrence boundary (S101). Specifically, the processing circuit 44 identifies the pile-up occurrence boundary by monitoring the pile-up occurrence status while changing the exposure dose and the equivalent water thickness.

[0101] In the margin setting function 445, the processing circuit 44 sets a margin range for the identified pileup generation boundary (S102).

[0102] In the condition placement function 446, the processing circuit 44 places calibration conditions in the pile-up generation region including the margin range (S103).

[0103] In the calibration function 447, the processing circuit 44 scans with the configured calibration conditions and generates correction data for pile-up correction based on the multiple acquired data of the multiple calibration conditions obtained (S104).

[0104] For example, after the generation process (S101-S104), the processing circuit 44 in the system control function 441 performs the actual scan.

[0105] In the calibration function 447, the processing circuit 44 performs pile-up correction on the detected data (collected data) of the scan based on the scan conditions for the actual scan and the correction data for pile-up correction (S105).

[0106] If the scan conditions in the actual scan do not match the calibration conditions, the processing circuit 44 applies interpolation from the pile-up correction table of the nearest calibration conditions, or from the pile-up correction table of at least one surrounding calibration condition.

[0107] In this embodiment, the flow is illustrated as one in which a generation process (S101-S104) is performed followed by a scan and a correction process (S105) for the scan, but this is not limited to this. For example, after performing a scan, a generation process may be performed using multiple collected data, including the collected data obtained from the scan.

[0108] As described above, the method for generating calibration data for pile-up correction according to this embodiment first determines the pile-up occurrence boundary and then determines the calibration conditions while taking various fluctuations into consideration. With this configuration, scanning of the region R1 where pile-up does not occur is unnecessary, so a pile-up correction table (calibration data for pile-up correction) can be generated efficiently and effectively.

[0109] The efficient and effective generation of calibration data for pile-up correction contributes to efficient and effective pile-up correction. Furthermore, the pile-up correction method using the calibration data according to this embodiment makes it possible to realize a calibration scheme that takes into account changes in detector response due to pile-up.

[0110] Furthermore, the pile-up generation boundary B, the margin range R4, or calibration conditions including these may be predetermined prior to the generation process. For example, in the system control function 441, the processing circuit 44 acquires predetermined calibration conditions from memory 41 or from outside the X-ray CT apparatus 1. Here, the processing circuit 44 that implements the system control function 441 is an example of an acquisition unit. The predetermined calibration conditions are an example of a first set of multiple acquired parameters for generating calibration data based on prior information. Prior information may include information indicating calibration conditions obtained in a previous generation process in the X-ray CT apparatus 1, or it may include information indicating the pile-up generation situation, individual fluctuations, or changes in response over time. Furthermore, calibration conditions for other X-ray CT apparatuses 1 may be used as prior information.

[0111] In the system control function 441, the processing circuit 44 acquires detection data (first detection data) by performing phantom imaging under predetermined calibration conditions. In the calibration function 447, the processing circuit 44 generates calibration data for pile-up correction using the first detection data.

[0112] Furthermore, in the condition setting function 446, the processing circuit 44 generates new calibration conditions (a second set of multiple acquisition parameters) based on the first detection data. Here, the second set of multiple acquisition parameters is used in a new phantom imaging to update the generated calibration data. As a result, the calibration conditions of the calibration scan are updated according to the state of the previous calibration data, thereby improving the efficiency of calibration data generation.

[0113] Furthermore, in the condition setting function 446, the processing circuit 44 may generate new calibration conditions (a second set of multiple acquisition parameters) based on the elapsed time since the first detection data was collected and / or the usage status since the first detection data was collected, in place of or in addition to the first detection data described above. In other words, the calibration conditions may be changed according to the passage of time and the usage status of the device, not limited to the state of the previous calibration data. This makes it possible to generate appropriate calibration data and achieve appropriate pile-up correction even if the sensor characteristics of the X-ray detector 12 change over time.

[0114] Furthermore, in the boundary identification function 444 and the margin setting function 445, the processing circuit 44 may update the pile-up occurrence boundary B and margin range R4 based on the first detection data when generating the second set of multiple collection parameters.

[0115] In the above description, the term "processor" refers to circuits such as CPUs, GPUs (Graphics Processing Units), ASICs, and Programmable Logic Devices (PLDs). PLDs include Simple Programmable Logic Devices (SPLDs), Complex Programmable Logic Devices (CPLDs), and Field Programmable Gate Arrays (FPGAs). A processor functions by reading and executing a program stored in a memory circuit. The memory circuit containing the program is a computer-readable, non-temporary recording medium. Alternatively, instead of storing the program in a memory circuit, the processor may be configured to directly incorporate the program into its circuitry. In this case, the processor functions by reading and executing the program incorporated into the circuitry. Furthermore, instead of executing the program, the processor may implement the function corresponding to the program through a combination of logic circuits. In this embodiment, each processor is not limited to being configured as a single circuit; multiple independent circuits may be combined to form a single processor, and its functions may be implemented in this way. Furthermore, the multiple components shown in Figure 1 may be integrated into a single processor to realize their functions.

[0116] According to at least one embodiment described above, efficient pile-up correction can be achieved in a photon counting type X-ray imaging device.

[0117] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made 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.

[0118] With respect to the above embodiments, the following additional notes are disclosed as aspects of the invention and selective features.

[0119] (Note 1) An X-ray generating unit that generates X-rays, A photon counting type X-ray detector for detecting X-rays from the X-ray generation unit, A unit that identifies boundary conditions that define the range of acquisition parameter sets in which pileup occurs, based on multiple detection datasets obtained by performing phantom imaging, in which X-rays irradiated onto the phantom are detected by the X-ray detector, with multiple different acquisition parameter sets, A setting unit for setting a margin range based on the aforementioned boundary conditions, A generation unit that generates multiple collection parameter sets included in the range obtained by adding the margin range to the range of the collection parameter set, A calibration unit that generates calibration data for pile-up correction based on multiple detection datasets obtained from the multiple collection parameter sets. A photon counting type X-ray imaging diagnostic device equipped with [a specific feature].

[0120] (Note 2) The setting unit may set the margin range on the side of the collection parameter set where pileup of the boundary conditions does not occur.

[0121] (Note 3) The setting unit may determine the size of the margin range based on at least one of the following: fluctuations in the X-ray detector, changes in response over time, quantum noise of X-ray generation, and charge sharing.

[0122] (Note 4) The generation unit may generate the collection parameter set more densely in the range where the contribution to the image based on the detection data after pile-up correction is high, compared to other ranges.

[0123] (Note 5) The generation unit may generate the collection parameter set more densely in the range where the trend of the boundary conditions changes than in other ranges.

[0124] (Note 6) The generation unit may exclude more acquisition parameter sets from the multiple acquisition parameter sets that can be set in the X-ray imaging diagnostic device as the thickness of the phantom increases when obtaining the detection dataset.

[0125] (Note 7) A photon-counting type X-ray imaging diagnostic apparatus comprising an X-ray generating unit that generates X-rays and a photon-counting type X-ray detector that detects X-rays from the X-ray generating unit, wherein the apparatus generates calibration data for pile-up correction used to correct detection data obtained in imaging in which X-rays irradiated onto a subject are detected by the X-ray detector, An acquisition unit that acquires a first set of multiple acquisition parameters for generating the calibration data based on prior information, A data acquisition unit that obtains first detection data by performing phantom imaging, in which X-rays irradiated onto the phantom are detected by the X-ray detector, using the first set of multiple acquisition parameters, A calibration unit that generates calibration data based on the collected first detection data, A generation unit generates a second set of multiple acquisition parameters used in the phantom imaging to update the generated calibration data, based on the first detection data, the elapsed time since the first detection data was collected, and the usage status since the first detection data was collected. Equipped with, The first and second sets of acquisition parameters are, respectively, control parameter sets of the X-ray imaging diagnostic apparatus for obtaining detection data by phantom imaging. In each of the first and second sets of acquisition parameters, some acquisition parameter sets that do not cause pileup are excluded from the set of acquisition parameter sets that can be set in the X-ray imaging device, and the thicker the phantom when obtaining the detection data, the more acquisition parameter sets are excluded from the set of acquisition parameter sets that can be set in the X-ray imaging device. A photon counting type X-ray imaging diagnostic device.

[0126] (Note 8) The generation unit may generate the plurality of collection parameter sets for at least one of the following: the X-ray exposure dose from the X-ray generation unit, the tube voltage used to generate X-rays by the X-ray generation unit, and the type of wedge provided in the X-ray generation unit.

[0127] (Note 9) Based on multiple detection datasets obtained by performing phantom imaging, in which X-rays irradiated onto the phantom are detected by an X-ray detector, with multiple different sets of acquisition parameters, the boundary conditions that define the range of acquisition parameter sets where pileup occurs are identified. Setting a margin range based on the aforementioned boundary conditions, To generate multiple collection parameter sets that fall within the range obtained by adding the margin range to the range of the collection parameter set, To generate calibration data for pile-up correction based on multiple detection datasets obtained from the multiple collection parameter sets, A method for generating calibration data for pile-up correction, including [specific data].

[0128] (Note 10) A method for generating calibration data for pile-up correction used to correct detection data obtained in imaging in a photon-counting type X-ray imaging diagnostic apparatus, in which X-rays from an X-ray generator irradiated onto a subject are detected by a photon-counting type X-ray detector, Obtaining a first set of multiple collection parameters for generating the calibration data based on prior information, By performing phantom imaging, in which X-rays irradiated onto the phantom are detected by the X-ray detector, using the first set of acquisition parameters, first detection data is obtained. The calibration data is generated based on the collected first detection data, To generate a second set of multiple acquisition parameters used in the phantom imaging to update the generated calibration data, based on at least one of the following: the first detection data, the elapsed time since the first detection data was collected, and the usage status since the first detection data was collected. Includes, The first and second sets of acquisition parameters are, respectively, control parameter sets of the X-ray imaging diagnostic apparatus for obtaining detection data by phantom imaging. In each of the first and second sets of acquisition parameters, some acquisition parameter sets that do not cause pileup are excluded from the set of acquisition parameter sets that can be set in the X-ray imaging device, and the thicker the phantom when obtaining the detection data, the more acquisition parameter sets are excluded from the set of acquisition parameter sets that can be set in the X-ray imaging device. A method for generating calibration data for pile-up correction. [Explanation of Symbols]

[0129] 1 X-ray CT device 10 mounting bases 11 X-ray tube 12 X-ray detectors 13 rotation frames 14 X-ray high-voltage equipment 15 Control device 16 Wedge 17 Collimator 18 Data Collection Circuit 19 Opening 30 berths 31 base 32 Bed drive mechanism 33 Top plate 34 Support Frame 40 Console 41 memory 42 displays 43 Input Interfaces 44 Processing Circuits 441 System control function (acquisition unit) 442 Image generation function 443 Image processing functions 444 Boundary identification function (identification part) 445 Margin setting function (settings section) 446 Conditional placement function (generation part) 447 Calibration function (calibration unit) 448 Display control function

Claims

1. An X-ray generating unit that generates X-rays, A photon counting type X-ray detector for detecting X-rays from the aforementioned X-ray generation unit, A unit that identifies boundary conditions that define the range of acquisition parameter sets in which pileup occurs, based on multiple detection datasets obtained by performing phantom imaging, in which X-rays irradiated onto the phantom are detected by the X-ray detector, with multiple different acquisition parameter sets, A setting unit for setting a margin range based on the aforementioned boundary conditions, A generation unit that generates multiple collection parameter sets included in the range obtained by adding the margin range to the range of the collection parameter set, A calibration unit that generates calibration data for pile-up correction based on multiple detection datasets obtained from the multiple collection parameter sets. A photon counting type X-ray imaging diagnostic device equipped with [a specific feature].

2. The photon counting type X-ray imaging diagnostic apparatus according to claim 1, wherein the setting unit sets the margin range on the side of the collection parameter set where pileup of the boundary conditions does not occur.

3. The photon counting type X-ray imaging apparatus according to claim 1, wherein the setting unit determines the size of the margin range based on at least one of the fluctuations of the X-ray detector, changes in response over time, quantum noise of X-ray generation, and charge sharing.

4. The photon counting type X-ray imaging diagnostic apparatus according to claim 1, wherein the generation unit generates the collection parameter set more densely in the range where the contribution to the image based on the detection data after pile-up correction is high than in other ranges.

5. The photon counting type X-ray imaging diagnostic apparatus according to claim 1, wherein the generation unit generates the collection parameter set more densely in the range where the trend of the boundary conditions changes than in other ranges.

6. The photon counting type X-ray imaging apparatus according to claim 1, wherein the generation unit excludes more acquisition parameter sets from a plurality of acquisition parameter sets that can be set in the X-ray imaging apparatus as the thickness of the phantom when obtaining the detection dataset increases.

7. A photon-counting type X-ray imaging diagnostic apparatus comprising an X-ray generating unit that generates X-rays and a photon-counting type X-ray detector that detects X-rays from the X-ray generating unit, wherein the apparatus generates calibration data for pile-up correction used to correct detection data obtained in imaging in which X-rays irradiated onto a subject are detected by the X-ray detector, An acquisition unit that acquires a first set of multiple acquisition parameters for generating the calibration data based on prior information, A data acquisition unit that obtains first detection data by performing phantom imaging, in which X-rays irradiated onto the phantom are detected by the X-ray detector, using the first set of multiple acquisition parameters, A calibration unit that generates calibration data based on the collected first detection data, A generation unit generates a second set of multiple acquisition parameters used in phantom imaging to update the generated calibration data, based on the first detection data, the elapsed time since the first detection data was collected, and the usage status since the first detection data was collected, at least from the first detection data. Equipped with, The first and second sets of acquisition parameters are, respectively, control parameter sets for the X-ray imaging diagnostic apparatus used to obtain detection data by phantom imaging. In each of the first and second sets of acquisition parameters, some acquisition parameter sets that do not cause pileup are excluded from the set of acquisition parameter sets that can be set in the X-ray imaging diagnostic device, and the thicker the phantom when obtaining the detection data, the more acquisition parameter sets are excluded from the set of acquisition parameter sets that can be set in the X-ray imaging diagnostic device. A photon counting type X-ray imaging diagnostic device.

8. The photon counting type X-ray imaging apparatus according to any one of claims 1 to 7, wherein the generation unit generates the plurality of acquisition parameter sets for at least one of the following: the exposure dose of X-rays from the X-ray generation unit, the tube voltage used to generate X-rays by the X-ray generation unit, and the type of wedge provided in the X-ray generation unit.

9. Based on multiple detection datasets obtained by performing phantom imaging, in which X-rays irradiated onto the phantom are detected by an X-ray detector, with multiple different sets of acquisition parameters, the boundary conditions that define the range of acquisition parameter sets where pileup occurs are identified. Setting a margin range based on the aforementioned boundary conditions, To generate multiple collection parameter sets that fall within the range obtained by adding the margin range to the range of the collection parameter set, To generate calibration data for pile-up correction based on multiple detection datasets obtained from the multiple collection parameter sets, A method for generating calibration data for pile-up correction, including [specific data].

10. A method for generating calibration data for pile-up correction used to correct detection data obtained in imaging in a photon-counting type X-ray imaging diagnostic apparatus, in which X-rays from an X-ray generator irradiated onto a subject are detected by a photon-counting type X-ray detector, Obtaining a first set of multiple collection parameters for generating the calibration data based on prior information, First detection data is obtained by performing phantom imaging, in which X-rays irradiated onto the phantom are detected by the X-ray detector, using the first set of acquisition parameters. The calibration data is generated based on the collected first detection data, To generate a second set of multiple acquisition parameters used in the phantom imaging to update the generated calibration data, based on the first detection data, the elapsed time since the first detection data was collected, and the usage status since the first detection data was collected, at least based on the first detection data. Includes, The first and second sets of acquisition parameters are, respectively, control parameter sets for the X-ray imaging diagnostic apparatus used to obtain detection data by phantom imaging. In each of the first and second sets of acquisition parameters, some acquisition parameter sets that do not cause pileup are excluded from the set of acquisition parameter sets that can be set in the X-ray imaging diagnostic device, and the thicker the phantom when obtaining the detection data, the more acquisition parameter sets are excluded from the set of acquisition parameter sets that can be set in the X-ray imaging diagnostic device. A method for generating calibration data for pile-up correction.

Images