JP2023135610A - Radiation diagnostic apparatus, radiation detector, and output determination method - Google Patents

Abstract

To reduce an influence of oblique incidence of radiation with respect to a radiation detector.SOLUTION: A radiation diagnostic apparatus according to the present embodiment includes a plurality of radiation detection elements and a determination unit. The plurality of radiation detection elements are arranged in a two-dimensional direction. The determination unit determines, based on a first output related to a first detection element included in the plurality of radiation detection elements and a second output related to a second detection element in the circumference of the first detection element, an output corresponding to a reconstitution position of the first detection element.SELECTED DRAWING: Figure 1

Description

Embodiments disclosed in this specification and the drawings relate to a radiation diagnostic apparatus, a radiation detector, and an output determination method.

Conventionally, in X-ray computed tomography (CT) equipment, detection modules in which X-ray conversion elements are arranged in a planar manner are arranged in an arc shape in the fan angle direction, thereby creating an arc-shaped X-ray detector. The technology to construct it is known. Since such an arc-shaped X-ray detector is flat in the direction of the cone angle, the angle of incidence of the X-rays on the X-ray conversion element increases as the cone angle increases.

Generally, in terms of reconstruction theory of detected X-rays, it is assumed that the X-rays are incident at the position on the surface of the X-ray conversion element. However, when X-rays obliquely enter the surface of the X-ray conversion element, where the X-rays are absorbed in the deep direction of the X-ray conversion element is a stochastic event. There is a possibility that the radiation is absorbed not only by the ray conversion element but also by other adjacent X-ray conversion elements. This reduces the spatial resolution of the X-ray detector in the cone angle direction, which may cause the image quality of the X-ray image data to deteriorate, such as elongating the image along the body axis of the subject, for example.

For this reason, there is a technique in which a detector module composed of a plurality of X-ray conversion elements is made into small modules, and the surface of the X-ray conversion element is oriented in the X-ray incident direction in each small module. However, in such a structure, the image quality may deteriorate due to the generation of scattered radiation caused by the structure of the small module.

In addition, X-ray conversion elements used as direct conversion type X-ray detectors that directly convert X-rays into electric charges using semiconductors or rare gases have a lower X-ray absorption cross section than indirect conversion type detectors. Small in comparison. Further, the thickness of a direct conversion type X-ray detector is generally thicker than the X-ray conversion element used in an indirect conversion type X-ray detector due to the semiconductor crystal acting as a photoelectric conversion element. For these reasons, the distance through which X-rays that enter obliquely in the X-ray conversion element of a direct conversion X-ray detector increases, and direct conversion X-ray detectors are more susceptible to the effects of obliquely entering X-rays. It becomes easier.

Furthermore, in an X-ray flat detector (FPD) used for general X-ray photography, all X-ray conversion elements are arranged on a large-area surface. Therefore, not only the column direction (cone angle direction) but also the channel direction (fan angle direction) are affected by the oblique incidence of X-rays, and the image quality of the X-ray image data may deteriorate. Furthermore, since the penetrating power of an X-ray photon differs depending on the energy of the X-ray photon, for example, in a photon counting detector, the degree of influence of oblique incidence of X-rays depends on the Depends on the energy range. As a result, the position of the X-ray conversion element projected by the energy bin is shifted, and the image quality of the X-ray image data may deteriorate.

JP2020-075078A

One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to reduce the influence of radiation obliquely entering a radiation detector. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problems. Problems corresponding to the effects of each configuration shown in the embodiments described later can also be positioned as other problems.

The radiological diagnostic apparatus according to this embodiment includes a plurality of radiation detection elements and a determining section. The plurality of radiation detection elements are arranged in a two-dimensional direction. The determination unit is configured to determine the above based on a first output related to a first detection element included in the plurality of radiation detection elements and a second output related to a second detection element surrounding the first detection element. An output corresponding to the reconstructed position of the first detection element is determined.

FIG. 1 is a diagram showing an example of the configuration of a PCCT apparatus 1 according to the first embodiment. FIG. 2 is a diagram showing a part of the X-ray detector closer to the end of the opening than the midplane, together with X-rays obliquely entering the X-ray detector, according to the first embodiment. FIG. 3 is a flowchart illustrating an example of the procedure of output determination processing according to the first embodiment. FIG. 4 is a diagram showing a part of the X-ray detector closer to the end of the opening than the midplane, together with X-rays obliquely entering the X-ray detector, according to a modification of the first embodiment. FIG. 5 is a diagram showing an example of the configuration of an X-ray detector corresponding to the radiation detector according to the second embodiment.

Embodiments of a radiation diagnostic apparatus, a radiation detector, and an output determination method will be described below with reference to the drawings. In the following embodiments, parts with the same reference numerals perform similar operations, and redundant explanations will be omitted as appropriate. Note that the radiation diagnostic apparatus and radiation detector according to the present application are not limited to the embodiments described below. Moreover, in order to make the description concrete, it is assumed that the radiation according to the embodiment is an X-ray. Note that the radiation according to the embodiments is not limited to X-rays, and may be other radiations (charged particles or electromagnetic waves according to various wavelengths).

The radiation detector according to the embodiment has a plurality of radiation detection elements arranged in a two-dimensional direction. The two-dimensional directions are, for example, a cone angle direction and a fan angle direction. The cone angle direction and fan angle direction will be explained later. Hereinafter, in order to make the description concrete, it is assumed that the X-ray detector is a photon counting type X-ray detector (hereinafter referred to as a photon counting type X-ray detector). The photon-counting X-ray detector includes, for example, a direct conversion X-ray detector that includes a semiconductor element that directly converts incident X-rays into electrical signals. Note that the photon counting type X-ray detector may include an indirect conversion type X-ray detector instead of a direct conversion type X-ray detector.

Note that the radiation detector according to the embodiment is not limited to a photon counting type X-ray detector, and may be an integral type (also referred to as a current mode measurement type or an energy integral type) X-ray detector. At this time, the integral type X-ray detector includes a direct conversion type or indirect conversion type X-ray detector. For example, the radiation detector may include, as an integral type X-ray detector, an X-ray flat detector (Flat Panel Detector (FPD)) used in general X-ray photography.

Furthermore, in order to make the description more concrete, it is assumed that the radiological diagnostic apparatus according to the embodiment is an X-ray computed tomography (CT) apparatus. More specifically, the radiological diagnostic apparatus according to the embodiment will be described as a photon counting type X-ray CT apparatus (hereinafter referred to as a PCCT apparatus) that can perform photon counting CT. A PCCT device is a device that can reconstruct X-ray CT image data with a high signal-to-noise ratio by counting X-rays that have passed through a subject using, for example, a direct conversion type X-ray detector. Note that the radiation diagnostic apparatus according to the embodiment may be an X-ray CT apparatus having an integral type X-ray detector instead of the photon counting type X-ray detector. Further, the radiological diagnostic apparatus may be an X-ray diagnostic apparatus having an FPD (for example, an X-ray diagnostic apparatus for general imaging, an X-ray diagnostic apparatus for circulatory organs (angiography), etc.).

(First embodiment)
FIG. 1 is a diagram showing an example of the configuration of a PCCT apparatus 1 according to the first embodiment. Note that the PCCT apparatus 1 may also be referred to as a radiation image diagnostic apparatus. As shown in FIG. 1, the PCCT apparatus 1 includes a gantry device 10, a bed device 30, and a console device 40. In the present embodiment, the rotation axis of the rotation frame 13 in a non-tilted state or the longitudinal direction of the top plate 33 of the bed device 30 is defined as the Z-axis direction, or an axial direction perpendicular to the Z-axis direction and horizontal to the floor surface. The axis direction perpendicular to the X-axis direction and the Z-axis direction, and perpendicular to the floor surface, is defined as the Y-axis direction. Although a plurality of gantry apparatuses 10 are depicted in FIG. 1 for convenience of explanation, the actual configuration of the PCCT apparatus 1 includes only one gantry apparatus 10.

The gantry device 10 and the bed device 30 operate based on the user's operation via the console device 40 or the user's operation via the operation unit provided on the gantry device 10 or the bed device 30. The gantry device 10, the bed device 30, and the console device 40 are connected to each other by wire or wirelessly so that they can communicate with each other.

The gantry device 10 is a device having an imaging system that irradiates the subject P with X-rays 100 and collects detection data of the X-rays 100 that have passed through the subject P. More specifically, the gantry device 10 includes an X-ray tube 11 (X-ray generation section), a wedge 16, a collimator 17, an X-ray detector 12, an X-ray high voltage device 14, and a DAS (Data Acquisition system) 18, a rotating frame 13, and a control device 15.

The X-ray tube 11 generates X-rays 100 by irradiating thermoelectrons from the cathode (filament) toward the anode (target) by applying high voltage and supplying filament current from the X-ray high voltage device 14. It's a vacuum tube. X-rays 100 are generated when the hot electrons collide with the target. X-rays 100 generated at the tube focal point in the X-ray tube 11 are shaped into a cone beam shape via, for example, a collimator 17, and are irradiated onto the subject P. For example, the X-ray tube 11 includes a rotating anode type X-ray tube that generates X-rays by irradiating a rotating anode with thermoelectrons.

As shown in FIG. 1, the X-rays 100 irradiated in a cone beam shape have a fan-like shape that spreads in the X-axis direction. Therefore, the angle indicating the spread of the X-rays 100 irradiated in a cone beam shape in the X-axis direction is called a fan angle. Further, the angle indicating the depth in the Z-axis direction of the X-rays 100 irradiated in a cone beam shape is called a cone angle. Therefore, the X-axis direction is also called the fan angle direction, and the Z-axis direction is also called the cone angle direction.

The X-ray detector 12 detects photons of X-rays generated by the X-ray tube 11. Specifically, the X-ray detector 12 detects the X-rays emitted from the X-ray tube 11 and passed through the subject P in units of photons, and outputs an electrical signal corresponding to the amount of X-rays to the DAS 18 . The X-ray detector 12 has, for example, a plurality of detection elements (also referred to as X-ray detection elements) arranged in a fan angle direction (also referred to as a channel direction) along one circular arc centered on the focal point of the X-ray tube 11. It has multiple detection element rows. In the X-ray detector 12, the plurality of detection element rows are arranged flat along the Z-axis direction. That is, the X-ray detector 12 has, for example, a structure in which a plurality of detection element rows are arranged flat along the cone angle direction (also referred to as the row direction, row direction, or slice direction). The plurality of detection elements in the X-ray detector 12 correspond to the plurality of radiation detection elements in the radiation detector.

Note that the PCCT apparatus 1 includes a Rotate/Rotate-Type (third generation CT) in which an X-ray tube 11 and an X-ray detector 12 rotate around the subject P as a unit, and a large number of There are various types such as Stationary/Rotate-Type (4th generation CT) in which the detection element is fixed and only the X-ray tube 11 rotates around the subject P, and any type can be applied to this embodiment. .

The X-ray detector 12 is a direct conversion type X-ray detector that includes a semiconductor element that converts incident X-rays into charges. The X-ray detector 12 of this embodiment includes, for example, at least one high voltage electrode, at least one semiconductor crystal, and multiple readout electrodes. The semiconductor element is also called an X-ray conversion element. The semiconductor crystal is realized by, for example, CdTe (cadmium telluride), CdZnTe (cadmium zinc telluride: CZT), or the like. In the X-ray detector 12, electrodes are provided on two surfaces facing each other with a semiconductor crystal in between and perpendicular to the Y direction. That is, the X-ray detector 12 is provided with a plurality of anode electrodes (also referred to as readout electrodes or pixel electrodes) and cathode electrodes (also referred to as common electrodes) with a semiconductor crystal interposed therebetween. Hereinafter, the surface formed by the cathode electrode will be referred to as a cathode surface.

A bias voltage is applied between the read electrode and the common electrode. In the X-ray detector 12, when X-rays are absorbed by the semiconductor crystal, electron-hole pairs are generated, the electrons move to the anode side (anode electrode (readout electrode) side), and the holes move to the cathode side ( By moving to the cathode electrode side), a signal related to X-ray detection is output from the X-ray detector 12 to the DAS 18.

The rotating frame 13 supports the X-ray tube 11 and the X-ray detector 12 rotatably around a rotation axis. Specifically, the rotating frame 13 supports the X-ray tube 11 and the X-ray detector 12 so as to face each other. The rotating frame 13 is an annular frame that rotates the X-ray tube 11 and the X-ray detector 12 by a control device 15, which will be described later. The rotating frame 13 is rotatably supported by a fixed frame made of metal such as aluminum. The rotating frame 13 receives power from the drive mechanism of the control device 15 and rotates around the rotation axis at a constant angular velocity.

Note that the rotating frame 13 further supports an X-ray high voltage device 14 and a DAS 18 in addition to the X-ray tube 11 and the X-ray detector 12. Such a rotating frame 13 is housed in a substantially cylindrical casing in which an opening (bore) forming an imaging space is formed. The central axis of the opening coincides with the rotation axis of the rotating frame 13.

The X-ray high voltage device 14 has electric circuits such as a transformer and a rectifier, and has the function of generating a high voltage to be applied to the X-ray tube 11 and a filament current to be supplied to the X-ray tube 11. It has a generator and an X-ray control device that controls the output voltage according to the X-rays emitted by the X-ray tube 11. The high voltage generator may be of a transformer type or an inverter type. Note that the X-ray high voltage device 14 may be provided on the rotating frame 13 or may be provided on the fixed frame (not shown) side of the gantry device 10. Note that the fixed frame is a frame that rotatably supports the rotating frame 13.

The control device 15 includes a processing circuit including a CPU (Central Processing Unit), and a drive mechanism such as a motor and an actuator. The processing circuit includes, as hardware resources, a processor such as a CPU or an MPU (Micro Processing Unit), and a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory). Further, the control device 15 may be configured using, for example, a GPU (Graphics Processing Unit), an application specific integrated circuit (ASIC), a programmable logic device (for example, a simple programmable logic device), or a programmable logic device (for example, a simple programmable logic device). ble Logic Device: SPLD), composite It may be realized by a processor such as a programmable logic device (CPLD) or a field programmable gate array (FPGA).

When the processor is, for example, a CPU, the processor realizes functions by reading and executing programs stored in memory. On the other hand, if the processor is an ASIC, instead of storing the program in memory, the functionality is built directly into the processor's circuitry as a logic circuit. Note that each processor of this embodiment is not limited to being configured as a single circuit for each processor, but may also be configured as a single processor by combining multiple independent circuits to realize its functions. good. Furthermore, multiple components may be integrated into one processor to implement its functionality.

The control device 15 also has a function of receiving input signals from the console device 40 or the input interface 43 attached to the gantry device 10 and controlling the operations of the gantry device 10 and the bed device 30. For example, the control device 15 receives an input signal and performs control to rotate the rotating frame 13, control to tilt the gantry device 10, and control to operate the bed device 30 and the top plate 33. Note that the control for tilting the gantry device 10 is performed by the control device 15, which rotates the frame around an axis parallel to the This may be realized by rotating 13. Further, the control device 15 may be provided on the gantry device 10 or may be provided on the console device 40.

The wedge 16 is a filter for adjusting the amount of X-rays 100 emitted from the X-ray tube 11. Specifically, the wedge 16 transmits the X-rays 100 emitted from the X-ray tube 11 so that the X-rays 100 emitted from the X-ray tube 11 to the subject P have a predetermined distribution. It is a filter that attenuates by The wedge 16 is, for example, a wedge filter or a bow-tie filter, and is a filter made of aluminum processed to have a predetermined target angle and a predetermined thickness.

The collimator 17 is a lead plate or the like for narrowing down the X-rays 100 transmitted through the wedge 16 into an X-ray irradiation range, and forms a slit by combining a plurality of lead plates or the like.

DAS (Data Acquisition System) 18 has a plurality of counting circuits. Each of the plurality of counting circuits includes an amplifier that performs amplification processing on the electrical signal output from each detection element of the X-ray detector 12, and an A/D converter that converts the amplified electrical signal into a digital signal. and generates detection data that is the result of counting processing using the detection signal of the X-ray detector 12. The result of the counting process is data in which the number of X-ray photons is assigned to each energy bin. An energy bin corresponds to an energy region of a predetermined width. For example, the DAS 18 counts photons (X-ray photons) originating from X-rays irradiated from the X-ray tube 11 and transmitted through the subject P, and detects the result of a counting process in which the energy of the counted photons is discriminated. Generate as data. DAS 18 is an example of a data collection unit.

The detection data generated by the DAS 18 is transferred to the console device 40. The detected data is a data set of the channel number of the generating detector pixel, the column number, the view number indicating the collected view (also referred to as the projection angle), and the value indicating the detected X-ray dose. Note that as the view number, the order in which the views were collected (collection time) may be used, or a number representing the rotation angle of the X-ray tube 11 (eg, 1 to 1000) may be used. Each of the plurality of counting circuits in the DAS 18 is realized, for example, by a circuit group equipped with circuit elements capable of generating detection data. In this embodiment, "detected data" simply refers to pure raw data detected by the X-ray detector 12 and before preprocessing, and raw data obtained by preprocessing the pure raw data. It encompasses both meanings. Note that the data before preprocessing (detection data) and the data after preprocessing may be collectively referred to as projection data.

The bed device 30 is a device on which a subject P to be scanned is placed and moved, and includes a base 31, a bed driving device 32, a top plate 33, and a top support frame 34. The base 31 is a casing that supports the top support frame 34 movably in the vertical direction. The bed driving device 32 is a motor or an actuator that moves the top plate 33 on which the subject P is placed in the longitudinal axis direction of the top plate 33. The bed driving device 32 moves the top plate 33 under the control of the console device 40 or the control device 15. The top plate 33 provided on the upper surface of the top plate support frame 34 is a plate on which the subject P is placed. In addition to the top plate 33, the bed driving device 32 may move the top plate support frame 34 in the longitudinal direction of the top plate 33.

The console device 40 is a device that controls the gantry device 10 and generates CT image data based on the scan results by the gantry device 10. The console device 40 includes a memory 41 (storage unit), a display 42 (display unit), an input interface 43 (input unit), and a processing circuit 44 (processing unit). Data communication between the memory 41, display 42, input interface 43, and processing circuit 44 is performed via a bus (BUS).

The memory 41 is realized by, for example, a semiconductor memory element such as a RAM (Random Access Memory), a flash memory, an HDD (Hard Disk Drive), an SSD (Solid State Drive), an optical disk, or the like. The memory 41 also reads and writes various information with portable storage media such as CDs (Compact Discs), DVDs (Digital Versatile Discs), and flash memories, and semiconductor memory devices such as RAMs (Random Access Memory). It may also be a drive device that does this. The memory 41 stores, for example, projection data and reconstructed image data. Furthermore, the storage area of the memory 41 may be located within the PCCT apparatus 1 or may be located within an external storage device connected via a network. Furthermore, the memory 41 stores a control program according to this embodiment. Furthermore, the memory 41 is an example of a storage section.

The display 42 displays various information. For example, the display 42 outputs a medical image (CT image) generated by the processing circuit 44, a GUI (Graphical User Interface) for accepting various operations from an operator, and the like. For example, as the display 42, a liquid crystal display (LCD), an organic electroluminescence display (OELD), a plasma display, or any other display can be used as appropriate. Further, the display 42 may be provided on the gantry device 10. Further, the display 42 may be of a desktop type, or may be configured with a tablet terminal or the like that can communicate wirelessly with the console device 40 main body.

The input interface 43 receives various input operations from an operator, converts the received input operations into electrical signals, and outputs the electrical signals to the processing circuit 44 . For example, the input interface 43 receives from the operator acquisition conditions when collecting projection data, reconstruction conditions when reconstructing a CT image, image processing conditions when generating a post-processed image from a CT image, etc. . As the input interface 43, for example, a mouse, keyboard, trackball, switch, button, joystick, touch pad, touch panel display, etc. can be used as appropriate.

Note that in this embodiment, the input interface 43 is not limited to one that includes physical operation components such as a mouse, keyboard, trackball, switch, button, joystick, touch pad, and touch panel display. For example, examples of the input interface 43 include 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 the processing circuit 44. . Further, the input interface 43 is an example of an input section. Further, the input interface 43 may be provided in the gantry device 10. Furthermore, the input interface 43 may be configured with a tablet terminal or the like that can communicate wirelessly with the main body of the console device 40.

The processing circuit 44 controls the operation of the entire PCCT apparatus 1 according to the input operation electrical signal output from the input interface 43. For example, the processing circuit 44 includes a system control function 441 , a preprocessing function 442 , a reconstruction processing function 443 , a scan control function 444 , an image processing function 445 , a display control function 446 , and a determination function 447 . Here, for example, the system control function 441, preprocessing function 442, reconstruction processing function 443, scan control function 444, image processing function 445, display control function 446, and determination Each processing function executed by the function 447 is recorded in the memory 41 in the form of a computer-executable program.

The processing circuit 44 is, for example, a processor, and implements functions corresponding to the read programs by reading each program from the memory 41 and executing them. In other words, the processing circuit 44 in a state where each program is read has each function shown in the processing circuit 44 of FIG. The processing circuit 44 that implements the system control function 441 is an example of a control unit. The processing circuit 44 that implements the preprocessing function 442 is an example of a preprocessing section. The processing circuit 44 that implements the reconfiguration processing function 443 is an example of a reconfiguration processing section. The processing circuit 44 that implements the scan control function 444 is an example of a scan control section. The processing circuit 44 that implements the image processing function 445 is an example of an image processing section. The processing circuit 44 that implements the display control function 446 is an example of a display control section. The processing circuit 44 that implements the decision function 447 is an example of a decision unit. Further, the processing circuit 44 may be used as an example of a control section.

Note that although FIG. 1 shows a case where the system control function 441, preprocessing function 442, reconstruction processing function 443, scan control function 444, and display control function 446 are realized by a single processing circuit 44, this The embodiment is not limited to this. For example, the processing circuit 44 may be configured by combining a plurality of independent processors, and each processor may implement each processing function by executing each program. Further, each processing function of the processing circuit 44 may be appropriately distributed or integrated into a single processing circuit or a plurality of processing circuits.

The processing circuit 44 controls various functions of the processing circuit 44 using the system control function 441 based on input operations received from the operator via the input interface 43 .

The processing circuit 44 uses a preprocessing function 442 to perform preprocessing such as logarithmic conversion processing, offset correction processing, sensitivity correction processing between channels, and beam hardening correction on the ideal detection data determined by the determination function 447. Generate data that has been subjected to Ideal detection data will be explained later.

The processing circuit 44 uses a reconstruction processing function 443 to perform reconstruction processing using a filtered back projection method, a successive approximation reconstruction method, etc. on the projection data generated by the preprocessing function 442, and generates a CT image. Generate data.

The processing circuit 44 uses the scan control function 444 to acquire two-dimensional positioning image data of the subject P for determining the scan range, imaging conditions, and the like. Note that the positioning image data is sometimes called scano image data or scout image data.

The processing circuit 44 uses the image processing function 445 to convert the CT image data generated by the reconstruction processing function 443 into a tomographic image of an arbitrary cross section by a known method based on the input operation received from the operator via the input interface 43. Convert to image data or 3D image data. Note that the generation of three-dimensional image data may be directly performed by the reconstruction processing function 443.

The processing circuit 44 causes the display control function 446 to display the tomographic image data and three-dimensional image data processed by the image processing function 445 on the display 42. Further, the display control function 446 causes the display 42 to display various GUIs (Graphical User Interfaces).

The processing circuit 44 uses the determination function 337 to determine the first output regarding the first detection element included in the plurality of radiation detection elements (the plurality of detection elements in the X-ray detector 12) and the surrounding area of the first detection element. and a second output related to the second detection element, an output corresponding to the reconstructed position of the first detection element is determined. The reconstruction position is, for example, a position that is used in reconstruction calculation based on the determined output and indicates a representative point of the first detection element. The reconstruction position is, for example, the surface (cathode surface) of the first detection element that the X-rays reach. Note that the reconstruction position is not limited to the cathode surface of the first detection element. For example, it may be at any position inside the semiconductor crystal on the anode electrode of the first detection element. Hereinafter, in order to make the description more specific, it is assumed that the reconstruction position is the incident position where the X-rays are incident on the cathode surface of the first detection element.

The processing circuit 44 receives from the determination function 337 a first output related to a first detection element included in the plurality of detection elements in the X-ray detector 12 and a first output related to a second detection element surrounding the first detection element. Based on the second output, determine the ideal output for the first detection element when the X-ray incident position is the surface (cathode surface) where the X-rays reach in the first detection element. . The X-ray incident position is, for example, the surface of the X-ray detector 12 where the X-ray path (also referred to as ray) to the first detection element first hits. In other words, the incident position of the X-ray corresponds to the position where, for example, an X-ray path that has passed through the subject P or a direct ray path that does not pass through the subject P, rather than the scattered X-rays, hits the cathode surface. .

The second detection element is not limited to, for example, at least one detection element adjacent to the first detection element, but is a plurality of detection elements surrounding the first detection element. The first output corresponds to detection data (pure raw data or count number) regarding the first detection element, and the second output corresponds to detection data (pure raw data or count number) regarding the second detection element. Note that when the radiological diagnostic apparatus is an X-ray diagnostic apparatus or an integral type X-ray CT apparatus, for example, the first output corresponds to pure raw data output from the first detection element, and the second output corresponds to corresponds to pure raw data output from the second detection element.

The ideal output means, for example, that when X-rays obliquely enter the cathode surface (hereinafter referred to as the opposing surface) facing the readout electrode (hereinafter referred to as the first electrode) of the first detection element, the corresponding It corresponds to the output (for example, count number or current value) regarding the first electrode when electrons generated by X-rays are read out at the first electrode. For example, the opposing surface corresponds to a surface directly above the first electrode along the Y-axis direction. Further, the second detection element is set in advance according to the incident angle of the X-ray ray that obliquely enters the opposing surface. In the PCCT apparatus 1, the first output, the second output, and the output corresponding to the reconstructed position of the first detection element (for example, may be referred to as an ideal output) are This is the number of counts. At this time, the ideal output corresponds to the output count when the surface of the X-ray detector 12 that the X-ray path to the first detection element first hits is counted as the incident position of the X-rays.

Specifically, the processing circuit 44 uses the determining function 447 to select a plane that includes the first detection element and the second detection element among the two-dimensional directions (channel direction and column direction) in which the plurality of detection elements are arranged. A first weight corresponding to a first angle from the reference line to the first detection element and a second angle from the reference line to the second detection element in the inner direction (for example, column direction). An output corresponding to the reconstructed position of the first detection element (ideal output regarding the first detection element) is determined using the corresponding second weight. That is, the determination function 447 performs a weighted calculation for each of the plurality of detection elements in the X-ray detector 12 using the outputs of the detection elements surrounding each of the detection elements, so that the determination function 447 statistically calculates the An expected output, that is, a plausible ideal output is calculated.

The reference line is, for example, a line connecting the center (midplane) in the cone angle direction of the X-ray detector 12 and the focal point of the tube. The first weight and the second weight are the material that converts X-rays (radiation) into electrons or visible light in the first detection element and the second detection element, the thickness of the material, and the It is set based on the angle of incidence on the detection element. For example, in the case of a direct conversion type X-ray detector, the material is a semiconductor crystal. Further, in the case of an indirect conversion type X-ray detector, the material is, for example, a scintillator. The angle at which the X-rays enter the first detection element corresponds to the first angle. The first weight and the second weight are determined by, for example, various simulations (for example, Monte Carlo simulation) using the first angle, the thickness and material of the semiconductor crystal, or a preliminary calibration test (experiment). Set in advance.

If the direction in the plane including the first detection element and the second detection element is, for example, the cone angle direction (column direction), that is, the first detection element and the second detection element are arranged in the cone angle direction. If they are arranged along the same line, the angle from the reference line to the first detection element is the angle between the reference line and the straight line connecting the first detection element and the tube focal point (hereinafter referred to as the first cone angle). ). Furthermore, when the direction in the plane including the first detection element and the second detection element is, for example, the cone angle direction (column direction), the angle from the reference line to the second detection element (hereinafter referred to as the second detection element) (referred to as the cone angle) corresponds to the angle between the straight line connecting the second detection element and the tube focal point and the reference line.

That is, when the first detection element and the second detection element are arranged along the cone angle direction, the processing circuit 44 uses the determination function 447 to determine the first detection element from the reference line to the first detection element. For example, by using a first weight corresponding to the first cone angle and a second weight corresponding to the second cone angle from the reference line to the second detection element, The first multiplication value obtained by multiplying the weight and the second multiplication value obtained by multiplying the second output by the second weight are added to obtain the output corresponding to the reconstructed position of the first detection element (first multiplication value). Determine the ideal output for the sensing element.

FIG. 2 is a diagram showing a part of the X-ray detector 12 closer to the end of the opening than the midplane, together with X-rays obliquely entering the X-ray detector 12. More specifically, FIG. 2 shows the end of the opening on the + side in the Z-axis direction, that is, the opening near the end on the + side in the Z-axis direction (the feet of the subject P) of the top plate 131 shown in FIG. A portion of the X-ray detector 12 near the end is shown along with X-rays obliquely entering the X-ray detector 12.

In FIG. 2, it is assumed that the first detection element is the readout electrode _CN . In addition, in FIG. 2, a portion of the X-rays _{N seg} generated in the X-ray tube 11 is an X-ray ( (hereinafter referred to as oblique X-rays). In FIG. 2, the ratio of the first output from the readout electrode C N to the total output from the plurality of readout electrodes (readout electrode C _N , readout electrode C _N+1 , readout electrode C _{N+2 )} caused by oblique X-rays is shown. is shown as 70%. In other words, the above 70% indicates the rate at which a portion of the X-rays N _seg is converted into electric charge in the semiconductor crystal surrounded by the dotted line in the area directly above the readout electrode _CN .

In addition, in FIG. 2, the second output output from the read electrode C N+1 with respect to the total output from the plural read electrodes (read electrode C _N , read electrode C _N+1 , read electrode C _{N+ 2} ) caused by oblique X-rays is shown. The percentage is shown as 29%. In other words, the above 29% indicates the rate at which a portion of the X-rays N _seg is converted into electric charge in the semiconductor crystal surrounded by the dotted line in the area directly above the readout electrode C _N+1 .

In addition, in FIG. 2, the second output output from the read electrode C N+2 with respect to the total output from the plural read electrodes (read electrode C _N , read electrode C _N+1 , read electrode C _{N+2 )} caused by oblique X-rays is shown. The percentage is shown as 1%. In other words, the above 1% indicates the rate at which a portion of the X-rays N _seg is converted into electric charge in the semiconductor crystal surrounded by the dotted line in the area directly above the readout electrode C _N+2 . In the example shown in FIG. 2, the second detection element corresponds to two readout electrodes C _N+1 and readout electrode C _N+2 .

That is, assuming the _{geometry of} the detection element and the oblique incidence of X- _rays as shown in FIG. 29% of the output and 1% of the output from readout electrode C _N+2 contribute to the ideal output C _iN of the first output. Specifically, in the example shown in FIG. 2, the ideal output C _iN for the first detection element (readout electrode C _N ) is calculated using the following equation (1).

On the right side of equation (1), C _N indicates the output (first output) related to the first detection element, that is, the readout electrode C _N. Furthermore, on the right side of equation (1), C _N+1 and C _N+2 indicate second outputs related to the second detection element (readout electrode C _N+1 and readout electrode C _N+2 ). Furthermore, on the right side of equation (1), k _N,N indicates the first weight, and k _N,N+1 and k _{N, N+2} indicate the second weight. As shown in FIG. 2, the first weights k _N,N are 0.7, and the second weights k _N,N+1 and k _N,N+2 are 0.29 and 0.01, respectively. Therefore, the processing circuit 44 uses the determination function 447 to determine the ideal output C _iN regarding the first detection element (readout electrode C _N ) using the following calculation formula (2).

The numerical values (0.7, 0.29.0.01) for the first weight and second weight in FIG. It varies depending on the angle of incidence, ie the column number. Generally, when the total number of detection elements along the column direction is n, and they are numbered from 1 to n along the cone angle direction (Z-axis direction), equation (1) is expressed as follows. It is generalized and expressed by equation (3).

は、複数の検出素子にそれぞれ対応する複数の理想的な出力を成分として有する理想出力ベクトルを示している。また、上式（３）における右辺のベクトル

は、複数の検出素子にそれぞれ対応する複数の出力（実測値）をベクトルの成分として有する実測出力ベクトルを示している。 Vector on the left side in equation (3) above

indicates an ideal output vector having as components a plurality of ideal outputs respectively corresponding to a plurality of detection elements. Also, the vector on the right side in the above equation (3)

indicates an actually measured output vector having as vector components a plurality of outputs (actually measured values) respectively corresponding to a plurality of detection elements.

は、複数の検出素子に関する複数の重みを行列として表している。換言すれば、重み行列は、Ｘ線検出器１２に関する出力の実測値を示す実測出力ベクトル

と、Ｘ線検出器１２に関する理想的な出力を示す理想出力ベクトル

とにおける各成分（複数の検出素子各々に関する出力）の相関係数を重みとして示す係数行列（例えば、相関行列）に相当する。列方向に沿った検出素子の総数ｎが奇数の場合、素子番号ｎ／２＋１は、ミッドプレーンに対応する。このとき、重みｋ_{ｎ／２＋１，ｉ}（１≦ｉ≦ｎ：ｎ／２＋１を除く）は、すべてゼロとなり、重みｋ_{ｎ／２＋１，ｎ／２＋１}は１となる。また、理想的には、係数行列は、１行Ｎ列とＮ行１列とを結ぶ対角線に対して対称な成分を有する行列となる。 Also, the matrix on the right side of the above equation (3) (hereinafter referred to as the weight matrix)

represents a plurality of weights regarding a plurality of detection elements as a matrix. In other words, the weight matrix is a measured output vector indicating the measured value of the output regarding the X-ray detector 12.

and an ideal output vector indicating the ideal output regarding the X-ray detector 12.

This corresponds to a coefficient matrix (for example, a correlation matrix) that indicates, as a weight, the correlation coefficient of each component (output regarding each of a plurality of detection elements) in and. When the total number n of detection elements along the column direction is an odd number, element number n/2+1 corresponds to the midplane. At this time, the weights k _{n/2+1, i} (excluding 1≦i≦n: n/2+1) are all zero, and the weights k _{n/2+1, n/2+1} are 1. Further, ideally, the coefficient matrix is a matrix having components that are symmetrical with respect to a diagonal line connecting the 1st row, Nth column and the Nth row, 1st column.

In the weight matrix, qualitatively, the larger the cone angle of a detection element, the greater the weight of adjacent elements in a direction with a larger cone angle (and multiple detection elements including the adjacent element along the larger direction). The weight becomes larger, and the weight related to the output of the detection element itself becomes smaller. For example, in the diagonal components of the weight matrix, the first weight becomes smaller as the number of rows and columns increases or decreases from the weight k _{n/2, n/2} corresponding to the midplane. For example, in the off-diagonal components of the weight matrix, from the weight k _{n/2, n/2} corresponding to the midplane, as the number of rows and columns increases or decreases, the second weight along the direction of the larger cone angle The second weight for the detection element increases. In other words, in the weight matrix, the first weight decreases and the second weight increases as the first angle increases in each of the plurality of detection elements. Weight matrices generated through various simulations (for example, Monte Carlo simulations) or preliminary calibration tests (experiments) are stored in the memory 41.

In the example shown in FIG. 2 and the above formula, only the cone angle direction is focused, but the fan angle direction may be focused instead of the cone angle direction. Further, for example, when an FPD is used as the X-ray detector 12, that is, when the incident angle of X-rays becomes large in a channel with a large fan angle, the dimension of the matrix calculation using the above formula may be expanded. At this time, the actual measured output vector and the ideal output vector are, for example, matrices that indicate the outputs of a plurality of detection elements in the cone angle direction and the fan angle direction, and the weight matrix uses the cone angle direction and the fan angle direction as arguments (subscripts). It becomes a 4-fold tensor with .

Note that the above processing realized by the determination function 447 may be realized by the preprocessing function 442. At this time, the preprocessing function 442 executes the processing content by the determination function 447 on the data before preprocessing (for example, count number) before executing the preprocessing. Further, the above-mentioned processing realized by the determination function 447 may be realized by the DAS 18. At this time, the DAS 18 executes the processing content by the determination function 447 on the detected data (for example, pure raw data or raw data (count number)).

The processing circuit 44 outputs the ideal output determined for each of the plurality of detection elements by the determination function 447 to the preprocessing function 442 . Determination of the ideal output by the determination function 447 corresponds to correcting the influence of oblique incidence of X-rays on the X-ray detector 12. That is, the ideal output corresponds to correction data in which the influence of oblique incidence of X-rays on the X-ray detector 12 is corrected. The preprocessing function 442 performs preprocessing on the correction data to generate projection data (hereinafter referred to as corrected projection data). The corrected projection data corresponds to projection data in which the influence of oblique incidence of X-rays on the X-ray detector 12 is reduced. The reconstruction processing function 443 generates a reconstructed image (hereinafter referred to as a corrected reconstructed image) by performing reconstruction processing on the corrected projection data. That is, the processing circuit 44 uses the reconstruction processing function 443 to perform reconstruction processing on the projection data based on the output corresponding to the reconstruction position, and generates a reconstructed image (corrected reconstructed image). The corrected reconstructed image is, for example, stored in the memory 41 and displayed on the display 42 by the display control function 446. The corrected reconstructed image corresponds to a reconstructed image in which the influence of oblique incidence of X-rays on the X-ray detector 12 has been corrected.

The overall configuration of the PCCT apparatus 1 as an example of a radiological diagnostic apparatus has been described above. Hereinafter, the procedure of the output determination process will be explained using FIG. 3. The output determination process consists in determining an output corresponding to the reconstructed position of the first detection element based on the collected first output and second output. FIG. 3 is a flowchart illustrating an example of the procedure of the output determination process.

(Output determination process)
(Step S301)
The data acquisition circuit 18 scans the subject P to obtain a first output related to a first detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction, and a second output around the first detection element. and a second output for the detection element. As a result, the first output and the second output are obtained.

(Step S302)
The processing circuit 44 determines, by means of a determination function 447, an output corresponding to the reconstructed position of the first detection element based on the first output and the second output. The determination of the output corresponding to the reconstructed position is based on the above description, so the description will be omitted.

The radiation diagnostic apparatus according to the first embodiment described above has a first output related to a first detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction, and a periphery of the first detection element. and a second output for the second detection element, an output corresponding to the reconstructed position of the first detection element (eg, an ideal output for the first detection element) is determined. For example, the radiological diagnostic apparatus according to the present embodiment has a first detection element from a reference line to a first detection element in a direction within a plane including a first detection element and a second detection element among two-dimensional directions. The output corresponding to the reconstruction position (for example, the ideal output ) to determine. Specifically, the radiological diagnostic apparatus according to the present embodiment has a first multiplication value obtained by multiplying a first output by a first weight, and a second multiplication value obtained by multiplying a second output by a second weight. The output corresponding to the reconstructed position (eg, the ideal output) is determined by adding the values and .

For example, the radiological diagnostic apparatus according to the first embodiment is an X-ray CT apparatus, the two-dimensional directions are a cone angle direction and a fan angle direction, the radiation is X-rays, and the first The detection element and the second detection element are arranged along the cone angle direction, and the first weight corresponds to the first cone angle from the reference line to the first detection element, and the second detection element from the reference line An output (for example, an ideal output) corresponding to the reconstruction position is determined using the second weight corresponding to the second cone angle up to the element. At this time, in the radiological diagnostic apparatus according to the present embodiment, the first output, the second output, and the output corresponding to the reconstruction position (for example, ideal output) are the number of counts obtained by counting photons in X-rays. It may be. The radiological diagnostic apparatus according to the present embodiment performs reconstruction processing on projection data based on an output (for example, ideal output) corresponding to a reconstruction position, and generates a reconstructed image. In the radiological diagnostic apparatus according to the first embodiment, the first weight and the second weight are the material that converts radiation into electrons or visible light in the first detection element and the second detection element, and the material that converts radiation into electrons or visible light in the first detection element and the second detection element. It is set based on the thickness of the material and the angle at which the radiation enters the first detection element (i.e., the angle of incidence of the X-ray obliquely entering the opposing surface), and as the first angle becomes larger, the first The weight of the second one is decreased and the second weight is increased.

For these reasons, according to the radiological diagnostic apparatus according to the first embodiment, the pure raw data or the raw data is not affected by oblique entry of X-rays into the opposing surface due to at least one of the cone angle and the fan angle. The effects can be corrected. As a result, according to the present radiological diagnostic apparatus, it is possible to correct the positional deviation of the radiation detection position caused by oblique incidence of X-rays and obtain projection data at a position corresponding to the original X-ray detection position. . From the above, according to the present radiological diagnostic apparatus, deterioration in image quality such as image stretching in the body axis direction and/or left and right directions of the subject P is reduced, and medical images (projection data) with improved spatial resolution are reduced. X-ray images or corrected reconstructed images) can be generated. Therefore, according to the present radiological diagnostic apparatus, the quality of the radiological examination for the subject P can be improved.

(Application example)
The PCCT device 1 collects data (number of counts) for each energy region (energy bin). Furthermore, the semiconductor crystal of the X-ray detector 12 in the PCCT apparatus 1 has a smaller X-ray absorption cross-section than that of a normal integral type X-ray detector. Therefore, the thickness of the X-ray detector 12 in the PCCT apparatus 1 is thicker than that of a normal integral type X-ray detector. For these reasons, the higher the energy of the X-rays, the greater the influence of oblique incidence of the X-rays on the reconstructed image. That is, in the conventional PCCT apparatus 1, the reconstructed image reconstructed for each energy bin has a higher energy representing the energy bin. The image will be stretched.

Therefore, this application example uses a plurality of weight matrices corresponding to a plurality of energy bins to determine an ideal output for each of a plurality of energy bins. In a plurality of weight matrices, the contribution rate _kN,N to its own detection element corresponding to the first weight decreases, and includes adjacent elements in the X-ray detector 12 near the + side end in the Z-axis direction. The contribution rate k _N,N'>N corresponding to the second weight from the second detection element to the first detection element increases. In addition, in the plurality of weight matrices, in the X-ray detector 12 near the − side end in the Z-axis direction, a contribution corresponding to the second weight from the second detection element including adjacent elements to the first detection element is The rate k _{N, N'<N} increases. In other words, the first weight in each of the plurality of energy bins decreases as the energy becomes higher in the plurality of representative energies representing the plurality of energy bins, and the second weight in each of the plurality of energy bins decreases as the energy becomes higher in the plurality of representative energies representing the plurality of energy bins. Energy increases as the energy increases.

The first output in this application example is, for example, a plurality of first counts corresponding to a plurality of energy bins in X-rays. Further, the second output in this application example is, for example, a plurality of second counts corresponding to a plurality of energy bins in X-rays. At this time, the processing circuit 44 uses the determination function 447 to select the plurality of energy bins based on the first weight, the second weight, the first count number, and the second count number for each of the plurality of energy bins. Determine the count number as an output (eg, ideal output) corresponding to each reconstructed position.

Specifically, the processing circuit 44 uses the following equation (4) by the determination function 447 to determine the output (for example, ideal output) corresponding to the reconstruction position for each of the plurality of energy bins.

は、複数の検出素子にそれぞれ対応する複数の再構成位置に対応する出力（例えば、理想的な出力）を成分として有する、エネルギービンごとの理想出力ベクトルを示している。また、上式（４）における右辺のベクトル

は、複数の検出素子にそれぞれ対応する複数の出力（実測値）をベクトルの成分として有する、エネルギービンごとの実測出力ベクトルを示している。 The vector on the left side in the above equation (4)

indicates an ideal output vector for each energy bin, which has as a component outputs (for example, ideal outputs) corresponding to a plurality of reconstruction positions corresponding to a plurality of detection elements, respectively. Also, the vector on the right side in the above equation (4)

indicates an actually measured output vector for each energy bin, which has a plurality of outputs (actually measured values) corresponding to a plurality of detection elements as vector components.

は、複数の検出素子に関する複数の重みをエネルギービンごとの行列として表している。式（４）の両辺におけるエネルギービンは、すべて同一のエネルギービンを表している。エネルギービンごとの重み行列は、エネルギービンごとの実測出力ベクトル

と、エネルギービンごとの理想出力ベクトル

とにおける各成分（複数の検出素子各々に関する出力）の相関係数を重みとして示す係数行列（例えば、相関行列）に相当する。エネルギービンごとの重み行列における他の特徴は、第１の実施形態と同様なため、説明は省略する。また、決定機能４４７における処理も、エネルギービンごとに第１の実施形態と同様な処理が繰り返されるため、説明は省略する。 Also, the weight matrix for each energy bin on the right side of equation (4) above is

represents a plurality of weights regarding a plurality of detection elements as a matrix for each energy bin. The energy bins on both sides of equation (4) all represent the same energy bin. The weight matrix for each energy bin is the measured output vector for each energy bin.

and the ideal output vector for each energy bin.

This corresponds to a coefficient matrix (for example, a correlation matrix) that indicates, as a weight, the correlation coefficient of each component (output regarding each of a plurality of detection elements) in and. Other features in the weight matrix for each energy bin are the same as in the first embodiment, so their description will be omitted. Furthermore, since the same processing as in the first embodiment is repeated for each energy bin in the determination function 447, a description thereof will be omitted.

In the radiation diagnostic apparatus according to the application example of the first embodiment described above, the first output is a plurality of first counts corresponding to a plurality of energy bins in X-rays, and the second output is is a plurality of second count numbers corresponding to a plurality of energy bins, and for each of the plurality of energy bins, the first weight, the second weight, the first count number, and the second count number are Based on this, a count number as an output (for example, an ideal output) corresponding to a reconstruction position for each of a plurality of energy bins is determined. Furthermore, in the radiation diagnostic apparatus according to this application example, the first weight in each of the plurality of energy bins decreases as the energy increases in the plurality of representative energies representing the plurality of energy bins, and the first weight in each of the plurality of energy bins decreases as the energy increases. The weight of 2 increases as the energy becomes higher in a plurality of representative energies.

From the above, according to the radiation diagnostic apparatus according to the application example of the first embodiment, since the contribution rate differs depending on the energy of X-rays, a weight matrix (coefficient matrix) for each energy bin is used to The independently measured counts can be corrected. According to the radiological diagnostic apparatus according to this application example, it is possible to more accurately correct the oblique incidence of X-rays, and it is possible to further improve the accuracy of count correction. In addition, since the semiconductor detector used as the X-ray detector 12 has a small X-ray cross-sectional area, and the influence of oblique incidence of X-rays tends to be large, the radiation diagnostic apparatus according to this application example makes it possible to correct the can increase the effect of

In addition, according to the radiological diagnostic apparatus according to this application example, the difference in the influence of oblique incidence between energy bins when performing spectral imaging can be alleviated by the calculation in the determination function 447, and Even in counting imaging, which is integration, it is possible to accurately correct the influence of oblique incidence of X-rays. In other words, according to the radiological diagnostic apparatus according to this application example, the degree of positional deviation that varies depending on the energy bin can be corrected for each energy bin, so the positional deviation between the energy bins is corrected, and accurate spectral Imaging becomes possible. For these reasons, the radiological diagnostic apparatus according to this application example can improve the spatial resolution of the reconstructed image in the body axis direction. Other effects are the same as those in the first embodiment, so their explanations will be omitted.

(Modified example)
In this modification, the X-ray detector 12 is constituted by a plurality of small modules each having a plurality of detection elements. That is, the X-ray detector 12 in this modification does not have an integral configuration in which a plurality of detection elements are arranged two-dimensionally, but by arranging detectors in small module units, it can be used as a large-area detector. is constructed. At this time, when the small modules are arranged in the designed position, a gap is always generated between two adjacent small modules.

FIG. 4 is a diagram showing a part of the X-ray detector 12 closer to the end of the opening than the midplane, together with X-rays obliquely entering the X-ray detector 12, according to this modification. The difference between FIG. 2 and FIG. 4 is that there is a gap between the Nth readout electrode C _N and the (N+1)th readout electrode C _N+1 . As shown in FIG. 4, the X-rays that have obliquely entered the gap obliquely enter the detection elements around the readout electrode _CN including adjacent elements. Each component in the weight matrix in this modification is set in consideration of gaps, as shown in FIG. 4. That is, as shown in FIG. 4, when there is a gap between the first detection element and the second detection element corresponding to the readout electrode _CN , the first weight is set smaller than when there is no gap. The second weight is set larger than that in the case where there is no gap.

As a result, according to the present modification, the components (each correction term) in the weight matrix in the first embodiment and the application example of the first embodiment take into account the increase in oblique incidence of X-rays due to the gap. can be set, and compensation for discontinuities in the measured output due to gaps between small modules in the X-ray detector 12 can be performed. In other words, according to this modification, a plurality of small detector modules are tiled, and gaps between the detector modules are fixed in areas where the gaps between the detector modules are not evenly spaced to prevent interference. Therefore, even in a region where the influence of oblique incidence of X-rays on adjacent elements is large, an ideal output can be calculated by setting the weights. Other effects in this modified example are the same as those in the first embodiment and the applied example of the first embodiment, so description thereof will be omitted.

(Second embodiment)
The difference from the first embodiment is that the radiation detector has a processing circuit that performs the decision function 447. Hereinafter, in order to make the description more specific, it is assumed that the radiation detector is an X-ray detector mounted on a PCCT apparatus. At this time, in the PCCT apparatus 1 shown in FIG. 1, the determination function 447 in the processing circuit 44 becomes unnecessary.

FIG. 5 is a diagram showing an example of the configuration of an X-ray detector 20 corresponding to the radiation detector in this embodiment. As shown in FIG. 5, the X-ray detector 20 includes a plurality of X-ray detection elements 21, a data acquisition circuit (DAS) 18, and a processing circuit 23. Since the plurality of X-ray detection elements 21 arranged in a two-dimensional direction are the same as those in the first embodiment, the explanation thereof will be omitted. Note that the multiple X-ray detection elements 21 correspond to, for example, multiple radiation detection elements.

For example, the DAS 18 collects a first count number based on the output from a first detection element included in the plurality of X-ray detection elements, and collects a first count number from a second detection element around the first detection element. A second count number is collected based on the output of. The configuration and functions of the DAS 18 are the same as those in the first embodiment, so descriptions thereof will be omitted.

The processing circuit 23 is, for example, a processor, and implements functions corresponding to the read programs by reading each program from the memory 41 and executing them. The hardware configuration of the processing circuit 23 is the same as that in the first embodiment, so a description thereof will be omitted. Based on the first count number and the second count number, the processing circuit 23 uses the determination function 447 to determine the first position when the radiation incident position is the surface where the radiation first reaches in the first detection element. Determine the ideal number of counts for the detection elements. The specific processing content by the determination function 447 is the same as that in the first embodiment, so a description thereof will be omitted. Further, the processing procedure of the output determination process in this embodiment is the same as that in the first embodiment, so the description thereof will be omitted.

As the application example and modification example of the second embodiment, the application example and modification example of the first embodiment can be used as appropriate, so the description thereof will be omitted. Further, the effects of the second embodiment are also the same as those of the first embodiment, so explanations thereof will be omitted.

When the technical idea of this embodiment is realized by an output determination method, the output determination method includes a first output related to a first detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction, and a first output related to a first detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction. and a second output regarding a second detection element around the detection element, and determine an output corresponding to a reconstructed position of the first detection element based on the first output and the second output. do. The processing procedure and effects of this output determination method are the same as those of the first embodiment, so their explanation will be omitted.

When the technical idea of this embodiment is realized by an output determination program, the output determination program causes a computer to output a first output related to a first detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction. and a second output regarding a second sensing element around the first sensing element, and based on the first output and the second output, the reconstructed position of the first sensing element is determined. Determining the corresponding output. At this time, a program that can cause a computer to execute the method can be stored and distributed in a storage medium such as a magnetic disk (hard disk, etc.), optical disk (CD-ROM, DVD, etc.), semiconductor memory, etc. . The processing procedures and effects in the output determination program are the same as those in the first embodiment, so their explanation will be omitted.

According to at least one embodiment described above, the influence of radiation obliquely entering the radiation detector can be reduced.

Although several embodiments of the invention have been described, these embodiments are presented by way of example 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 changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention as well as within the scope of the invention described in the claims and its equivalents.

Regarding the above embodiments, etc., the following additional notes are disclosed as one aspect and optional features of the invention.
(Additional note 1)
a plurality of radiation detection elements arranged in a two-dimensional direction;
An output corresponding to a reconstructed position of the first detection element based on a first output regarding the first detection element included in the plurality of radiation detection elements and a second output regarding the second detection element. a deciding section that decides;
A radiation detector comprising:
(Additional note 2)
The determining unit is configured to determine a first angle from a reference line to a first detecting element in a direction within a plane including the first detecting element and the second detecting element among the two-dimensional directions. An output corresponding to the reconstructed position is determined using a first weight and a second weight corresponding to a second angle from the reference line to the second detection element, and A weight may be provided to each of the plurality of second detection elements.
(Additional note 3)
The determining unit adds a first multiplication value obtained by multiplying the first output by the first weight, and a second multiplication value obtained by multiplying the second output by the second weight. Accordingly, an output corresponding to the reconstructed position may be determined.
(Additional note 4)
The radiation detector is installed in an X-ray computed tomography apparatus,
The two-dimensional directions are a cone angle direction and a fan angle direction,
The radiation is an X-ray,
The first detection element and the second detection element are arranged along the cone angle direction,
The determining unit is configured to set the first weight according to the first cone angle from the reference line to the first detection element, and the first weight according to the second cone angle from the reference line to the second detection element. A weight of 2 may be used to determine the output corresponding to the reconstructed position.
(Appendix 5)
The first output, the second output, and the output corresponding to the reconstruction position may be counts of photons in the X-rays.
(Appendix 6)
The first output is a plurality of first counts according to a plurality of energy bins in the X-ray,
The second output is a plurality of second counts according to the plurality of energy bins,
The determining unit determines the plurality of energies based on the first weight, the second weight, the first count number, and the second count number for each of the plurality of energy bins. A count number as an output corresponding to the reconstructed position for each bin may be determined.
(Appendix 7)
The first weight in each of the plurality of energy bins decreases as the energy increases in a plurality of representative energies representing the plurality of energy bins,
The second weight in each of the plurality of energy bins may increase as the energy becomes higher in the plurality of representative energies.
(Appendix 8)
The first weight and the second weight are:
A material that converts the radiation into electrons or visible light in the first detection element and the second detection element, a thickness of the material, and a first angle at which the radiation enters the first detection element. is set based on
As the first angle increases, the first weight may decrease and the second weight may increase.
(Appendix 9)
When there is a gap between the first detection element and the second detection element, the first weight is set smaller than when there is no gap, and the second weight is set when there is no gap. It may be set larger than in the case.
(Appendix 10)
An X-ray computed tomography apparatus equipped with the radiation detector according to any one of Supplementary Notes 1 to 10,
comprising a reconstruction processing unit that performs reconstruction processing on projection data based on an output corresponding to the reconstruction position and generates a reconstructed image;
X-ray computed tomography equipment.
(Appendix 11)
The reconstruction position may be a position that is used in reconstruction calculation based on the output and indicates a representative point of the first detection element.
(Appendix 12)
A first count number is collected based on the output from a first detection element included in the plurality of radiation detection elements, and a first count number is collected based on the output from a second detection element surrounding the first detection element. , further comprising a data collection circuit that collects a second count number,
The determining unit may determine a count number corresponding to a reconfiguration position of the first detection element based on the first count number and the second count number.
(Appendix 13)
An X-ray computed tomography apparatus comprising the radiation detector according to any one of Supplementary Notes 1 to 12.
(Appendix 14)
Collecting a first output related to a first detection element and a second output related to a second detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction,
determining an output corresponding to a reconstructed position of the first detection element based on the first output and the second output;
An output determination method comprising:
(Appendix 15)
to the computer,
Collecting a first output related to a first detection element and a second output related to a second detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction,
determining an output corresponding to a reconstructed position of the first detection element based on the first output and the second output;
A computer-readable non-volatile storage medium that stores an output determination program that realizes.

1 PCCT device 11 X-ray tube 12 X-ray detector 18 DAS
20 X-ray detector 21 Plural X-ray detection elements 23 Processing circuit 40 Console device 41 Memory 42 Display 43 Input interface 44 Processing circuit 100 X-ray 441 System control function 442 Pre-processing function 443 Reconstruction processing function 444 Scan control function 445 Image Processing function 446 Display control function 447 Decision function P Subject

Claims (13)

a plurality of radiation detection elements arranged in a two-dimensional direction;
The first detection is performed based on a first output related to a first detection element included in the plurality of radiation detection elements and a second output related to a second detection element surrounding the first detection element. a determining unit that determines an output corresponding to the reconstructed position of the element;
A radiological diagnostic device equipped with. The determining unit is configured to determine a first angle from a reference line to a first detecting element in a direction within a plane including the first detecting element and the second detecting element among the two-dimensional directions. determining an output corresponding to the reconstructed position using a first weight and a second weight according to a second angle from the reference line to the second detection element;
The radiological diagnostic apparatus according to claim 1. The determining unit adds a first multiplication value obtained by multiplying the first output by the first weight, and a second multiplication value obtained by multiplying the second output by the second weight. determining an output corresponding to the reconstructed position;
The radiological diagnostic apparatus according to claim 2. The radiological diagnostic device is an X-ray computed tomography device,
The two-dimensional directions are a cone angle direction and a fan angle direction,
The radiation is X-rays,
The first detection element and the second detection element are arranged along the cone angle direction,
The determining unit is configured to set the first weight according to the first cone angle from the reference line to the first detection element, and the first weight according to the second cone angle from the reference line to the second detection element. determining an output corresponding to the reconstructed position using a weight of 2;
The radiological diagnostic apparatus according to claim 2 or 3. The first output, the second output, and the output corresponding to the reconstruction position are counts of photons in the X-ray,
The radiological diagnostic apparatus according to claim 4. The first output is a plurality of first counts according to a plurality of energy bins in the X-ray,
The second output is a plurality of second counts according to the plurality of energy bins,
The determining unit determines the plurality of energies based on the first weight, the second weight, the first count number, and the second count number for each of the plurality of energy bins. determining a count number as an output corresponding to the reconstructed position for each bin;
The radiological diagnostic apparatus according to claim 5. The first weight in each of the plurality of energy bins decreases as the energy increases in a plurality of representative energies representing the plurality of energy bins,
The second weight in each of the plurality of energy bins increases as the energy increases in the plurality of representative energies,
The radiological diagnostic apparatus according to claim 6. The first weight and the second weight are:
A material that converts radiation into electrons or visible light in the first detection element and the second detection element, a thickness of the material, and a first angle at which the radiation enters the first detection element. set based on
As the first angle increases, the first weight decreases and the second weight increases;
The radiological diagnostic apparatus according to claim 2. When there is a gap between the first detection element and the second detection element, the first weight is set smaller than when there is no gap, and the second weight is set when there is no gap. is set larger than the case,
The radiological diagnostic apparatus according to claim 2. further comprising a reconstruction processing unit that performs reconstruction processing on projection data based on an output corresponding to the reconstruction position and generates a reconstructed image;
The radiological diagnostic apparatus according to claim 1. The reconstruction position is a position that is used in reconstruction calculation based on the output and indicates a representative point of the first detection element.
The radiological diagnostic apparatus according to claim 1. a plurality of radiation detection elements arranged in a two-dimensional direction;
A first count number is collected based on the output from a first detection element included in the plurality of radiation detection elements, and a first count number is collected based on the output from a second detection element surrounding the first detection element. , a data collection circuit that collects a second count number;
a determining unit that determines a count number corresponding to a reconstructed position of the first detection element based on the first count number and the second count number;
A radiation detector comprising: A first output related to a first detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction and a second output related to a second detection element surrounding the first detection element are collected. ,
determining an output corresponding to a reconstructed position of the first detection element based on the first output and the second output;
An output determination method comprising:

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