Radiation diagnostic apparatus, radiation detector, and output determination method

Abstract

A radiation diagnostic apparatus of the embodiments has a plurality of radiation detecting elements and a processing circuit. The plurality of radiation detecting elements are arranged in a two-dimensional direction. The processing circuit determines an ideal output related to a first detecting element included in the plurality of radiation detecting elements, in a case where a surface where radiation first arrives in the first detecting element is set as an incident position of the radiation, based on a first output related to the first detecting element and a second output related to a second detecting element.

Description

Technical Field

[0001] This invention relates to a radiological diagnostic device, a radiological detector, and a method for determining output. Background Technology

[0002] Previously, it was known that in X-ray computed tomography (CT) equipment, a technique was used to construct an arc-shaped X-ray detector by arranging detection modules with X-ray conversion elements arranged in a planar pattern in an arc shape along the fan-shaped angular direction. Because such an arc-shaped X-ray detector is flat in the cone-angle direction, the larger the cone angle, the larger the incident angle of X-rays on the X-ray conversion elements.

[0003] Typically, the reconstruction theory of detected X-rays is considered to assume that the X-rays are incident at the surface of the X-ray conversion element. However, when X-rays are incident obliquely relative to the surface of the X-ray conversion element, the location where these X-rays are absorbed in the deeper direction of the X-ray conversion element is a probabilistic event. Therefore, the X-rays are not limited to the incident X-ray conversion element and may be absorbed by other adjacent X-ray conversion elements. As a result, the spatial resolution in the cone direction of the X-ray detector decreases, for example, the image may be elongated along the body axis of the subject, leading to a decrease in the image quality of the X-ray image data.

[0004] Therefore, there is a technique that miniaturizes detector modules composed of multiple X-ray conversion elements, aligning the surface of each small module with the X-ray conversion element surface facing the X-ray incident direction. However, in such a configuration, image quality can deteriorate due to the generation of scattered rays caused by the structure of the small modules.

[0005] Furthermore, the X-ray conversion element used in direct-conversion X-ray detectors, which directly convert X-rays into electrical charge using semiconductors or inert gases, has a smaller X-ray absorption cross-sectional area than that of indirect-conversion detectors. Additionally, the thickness of direct-conversion X-ray detectors is generally greater than that of the X-ray conversion element used in indirect-conversion X-ray detectors due to the semiconductor crystal that functions as the photoelectric conversion element. Because of these factors, the travel distance of obliquely incident X-rays within the X-ray conversion element of a direct-conversion X-ray detector is longer, making it more susceptible to the effects of oblique X-ray incidence.

[0006] Furthermore, in flat panel detectors (FPDs) commonly used in X-ray radiography, all X-ray conversion elements are positioned on a large surface area. Therefore, not only in the column direction (cone angle direction), but also in the channel direction (fan angle direction), the image quality of the X-ray image data can be affected by the oblique entry of X-rays, sometimes resulting in deterioration. Moreover, since the penetrating power of X-ray photons varies depending on their energy, the degree of influence of oblique entry of X-rays varies depending on the energy domain of the X-rays, for example in photon counting detectors. Consequently, the position of the X-ray conversion elements projected from the energy bin shifts, leading to a deterioration in the image quality of the X-ray image data. Summary of the Invention

[0007] Technical solution one relates to a radiological diagnostic device, which includes: a plurality of radiological detection elements arranged in a two-dimensional direction; and a processing circuit that determines an output corresponding to the reconstructed position of the first detection element based on a first output related to a first detection element included in the plurality of radiological detection elements and a second output related to a second detection element.

[0008] Technical solution two relates to a radiation detector, comprising: a plurality of radiation detection elements arranged in a two-dimensional direction; a data collection circuit that collects a first count based on the output of a first detection element included in the plurality of radiation detection elements, and collects a second count based on the output of a second detection element surrounding the first detection element; and a processing circuit that determines a count corresponding to the reconstructed position of the first detection element based on the first count and the second count.

[0009] Technical solution three relates to an output determination method, which includes the following steps: collecting 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; and determining an output corresponding to the reconstructed position of the first detection element based on the first output and the second output. Attached Figure Description

[0010] Figure 1 This is a diagram showing an example of the structure of the PCCT device 1 according to the first embodiment.

[0011] Figure 2 This is a diagram showing, in relation to the first embodiment, a portion of the X-ray detector located at the end of the plane closer to the opening, together with X-rays obliquely entering the X-ray detector.

[0012] Figure 3 This is a flowchart illustrating an example of the order of output determination processing related to the first embodiment.

[0013] Figure 4 This is a variation of the first embodiment, showing a portion of the X-ray detector on the end side closer to the opening than the midplane, together with X-rays obliquely entering the X-ray detector.

[0014] Figure 5 This is a diagram showing an example of the structure of an X-ray detector corresponding to the radiation detector of the second embodiment. Detailed Implementation

[0015] The radiological diagnostic apparatus of the embodiment includes a plurality of radiological detection elements and a processing circuit. The plurality of radiological detection elements are arranged in a two-dimensional direction. The processing circuit determines an output corresponding to the reconstructed position of the first detection element based on a first output related to a first detection element included in the plurality of radiological detection elements and a second output related to a second detection element surrounding the first detection element.

[0016] The following is a reference to the appendix. Figure 1 The embodiments of the radiodiagnostic apparatus and radiodetector will be described below. In the following embodiments, it is assumed that parts with the same reference numerals perform the same operations, and repeated descriptions are omitted where appropriate. Furthermore, the radiodiagnostic apparatus and radiodetector of this application are not limited to the embodiments shown below. In addition, for the sake of detail, it is assumed that the radiation in the embodiments is X-ray. However, the radiation in the embodiments is not limited to X-rays, and may also be other types of radiation (electromagnetic waves corresponding to charged particles and various wavelengths), etc.

[0017] The radiation detector described in this embodiment has multiple radiation detection elements arranged in a two-dimensional direction. The two-dimensional direction is, for example, a cone-angle direction and a sector-angle direction. The cone-angle direction and sector-angle direction will be explained later. Hereinafter, for the sake of detail, it is assumed to be a photon-counting X-ray detector (hereinafter referred to as a photon-counting type X-ray detector). A photon-counting type X-ray detector, for example, is a direct-conversion type X-ray detector having a semiconductor element that directly converts incident X-rays into electrical signals. Alternatively, a photon-counting type X-ray detector may be used instead of a direct-conversion type X-ray detector, and may be an indirect-conversion type X-ray detector.

[0018] Furthermore, the radiation detector in the embodiments is not limited to a photon counting type X-ray detector, but can also be an integrating type (also called a current-mode measurement method or energy integration type) X-ray detector. In this case, the integrating type X-ray detector can be a direct conversion type or an indirect conversion type X-ray detector. For example, the radiation detector can also be an integrating type X-ray detector and has an X-ray planar detector (flat panel detector (FPD)) commonly used in X-ray radiography.

[0019] Furthermore, for the sake of detail, the radiological diagnostic apparatus described in the embodiments is assumed to be an X-ray computed tomography (CT) apparatus. More specifically, it is assumed that the radiological diagnostic apparatus described in the embodiments is a photon-counting type X-ray CT apparatus (hereinafter referred to as a PCCT apparatus) capable of performing photon-counting CT. A PCCT apparatus is, for example, a device that can reconstruct X-ray CT image data with a high SN ratio by counting the X-rays passing through the subject using a direct conversion type X-ray detector. Alternatively, the radiological diagnostic apparatus described in the embodiments may also be an X-ray CT apparatus that has an integrating type X-ray detector instead of a photon-counting type X-ray detector. In addition, the radiological diagnostic apparatus may also be an X-ray diagnostic apparatus with an FPD (e.g., a general radiographic X-ray diagnostic apparatus, a circulatory X-ray diagnostic apparatus (angiography apparatus, etc.)).

[0020] (First Embodiment)

[0021] Figure 1 This diagram illustrates an example of the structure of the PCCT apparatus 1 according to the first embodiment. Additionally, the PCCT apparatus 1 may also be referred to as a radiographic imaging diagnostic apparatus. Figure 1 As shown, the PCCT device 1 includes a stand assembly 10, an examination bed assembly 30, and a control console assembly 40. Furthermore, in this embodiment, the rotation axis of the rotating frame 13 in its non-tilted state or the length direction of the top plate 33 of the examination bed assembly 30 is defined as the Z-axis direction; the axis orthogonal to the Z-axis direction and horizontal relative to the floor surface is defined as the X-axis direction; and the axis orthogonal to the Z-axis direction and perpendicular to the floor surface is defined as the Y-axis direction. Figure 1 For ease of explanation, multiple stage devices 10 are depicted, but as the actual structure of the PCCT device 1, the stage device 10 is one.

[0022] The stand device 10 and the examination bed device 30 operate based on user operation via the control console device 40 or via operation units provided on the stand device 10 or the examination bed device 30. The stand device 10, the examination bed device 30, and the control console device 40 can communicate with each other via wired or wireless connection.

[0023] The stage 10 is a device for a radiographic system that irradiates a 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 stage 10 includes an X-ray tube 11 (X-ray generating unit), a wedge 16, a collimator 17, an X-ray detector 12, an X-ray high-voltage device 14, a DAS (Data Acquisition System) 18, a rotating frame 13, and a control device 15.

[0024] X-ray tube 11 is a vacuum tube that generates X-rays 100 by irradiating thermionic electrons from the cathode (filament) toward the anode (target) through the application of high voltage from X-ray high-voltage device 14 and the supply of filament current. X-rays 100 are generated by the collision of thermionic electrons with the target. The X-rays 100 generated at the focal point of the X-ray tube 11 are shaped into a cone shape by collimator 17, for example, and irradiate the subject P. For example, X-ray tube 11 may be a rotating anode type X-ray tube that generates X-rays by irradiating thermionic electrons toward a rotating anode.

[0025] like Figure 1 As shown, the X-rays 100 irradiated in a cone-beam shape are arranged in a fan-shaped pattern along the X-axis. Therefore, the angle representing the expansion of the X-rays 100 in the X-axis direction is called the fan angle. Furthermore, the angle representing the depth of the X-rays 100 in the Z-axis direction is called the cone angle. Therefore, the X-axis direction is also called the fan angle direction, and the Z-axis direction is called the cone angle direction.

[0026] X-ray detector 12 detects photons of X-rays generated by X-ray tube 11. Specifically, X-ray detector 12 detects X-rays that have been irradiated from X-ray tube 11 and passed through the subject P in photon units, and outputs an electrical signal corresponding to the X-ray dose to DAS 18. X-ray detector 12, for example, has multiple rows of detection elements (also called X-ray detection elements) arranged along an arc in a sector direction (also called channel direction) centered on the focal point of X-ray tube 11. In X-ray detector 12, the multiple rows of detection elements are arranged flatly along the Z-axis direction. That is, X-ray detector 12, for example, has a configuration in which multiple rows of detection elements are arranged flatly along a cone direction (also called column direction, row direction, slice direction). The multiple detection elements of X-ray detector 12 correspond to the multiple radiation detection elements of a radiation detector.

[0027] Furthermore, in the PCCT apparatus 1, there are various types, such as Rotate / Rotate-Type (3rd generation CT) in which the X-ray tube 11 and X-ray detector 12 are integrated and rotate around the subject P, and Stationary / Rotate-Type (4th generation CT) in which many detection elements are fixed in a ring array and only the X-ray tube 11 rotates around the subject P. Regardless of the type, it can be applied to this embodiment.

[0028] The X-ray detector 12 is a direct conversion type X-ray detector having a semiconductor element that converts incident X-rays into electrical charge. 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 made of, for example, CdTe (cadmium telluride) or CdZnTe (cadmium zinc telluride, CZT). In the X-ray detector 12, electrodes are provided on two surfaces facing each other and orthogonal to the Y direction, sandwiching the semiconductor crystal. That is, in the X-ray detector 12, multiple anode electrodes (also called readout electrodes or pixel electrodes) and cathode electrodes (also called common electrodes) are provided sandwiching the semiconductor crystal. Hereinafter, the surface formed by the cathode electrode will be referred to as the cathode surface.

[0029] A bias voltage is applied between the readout electrode and the common electrode. In the X-ray detector 12, if X-rays are absorbed by the semiconductor crystal, electron-hole pairs are generated. Electrons move toward the anode side (anode electrode (readout electrode) side) and holes move toward the cathode side (cathode electrode side), thereby outputting a signal related to the detection of X-rays from the X-ray detector 12 to the DAS 18.

[0030] The rotating frame 13 rotatably supports the X-ray tube 11 and the X-ray detector 12 about a rotation axis. Specifically, the rotating frame 13 supports the X-ray tube 11 and the X-ray detector 12 opposite to each other. The rotating frame 13 is an annular frame that allows the X-ray tube 11 and the X-ray detector 12 to rotate via a control device 15 described later. The rotating frame 13 is rotatably supported by a fixed frame made of a metal such as aluminum. The rotating frame 13 receives power from the drive mechanism of the control device 15 and rotates about the rotation axis at a certain angular velocity.

[0031] In addition to the X-ray tube 11 and the X-ray detector 12, the rotating frame 13 also supports the X-ray high-voltage device 14 and the DAS 18. This rotating frame 13 is housed in a generally cylindrical shell with an opening (cavity) forming a photographic space. The central axis of the opening is aligned with the rotation axis of the rotating frame 13.

[0032] The X-ray high-voltage device 14 includes: a high-voltage generating device with circuitry including a transformer (converter) and a rectifier, capable of generating a high voltage applied to the X-ray tube 11 and supplying filament current to the X-ray tube 11; and an X-ray control device for controlling the output voltage corresponding to the X-rays irradiated by the X-ray tube 11. The high-voltage generating device can be either a transformer or an inverter. Furthermore, the X-ray high-voltage device 14 can be mounted on the rotating frame 13 or on the fixed frame (not shown) side of the stage assembly 10. The fixed frame is a frame that rotatably supports the rotating frame 13.

[0033] The control device 15 includes processing circuitry with a CPU (Central Processing Unit) and drive mechanisms such as motors and actuators. The processing circuitry, as hardware resources, includes processors such as CPUs and MPUs (Micro Processing Units) and memories such as ROM (Read Only Memory) and RAM (Random Access Memory). Furthermore, the control device 15 may also be implemented using processors such as GPUs (Graphics Processing Units), Application Specific Integrated Circuits (ASICs), or programmable logic devices (e.g., Simple Programmable Logic Devices (SPLDs), Complex Programmable Logic Devices (CPLDs), and Field Programmable Gate Arrays (FPGAs)).

[0034] In the case of a processor such as a CPU, the processor implements its functions by reading and executing a program stored in memory. On the other hand, in the case of an ASIC, instead of storing the program in memory, the functionality is directly incorporated into the processor's circuitry as logic circuitry. Furthermore, the processors in this embodiment are not limited to being configured as a single circuit; multiple independent circuits can be combined to form a single processor to implement its functions. Moreover, multiple components can be merged into a single processor to achieve its functions.

[0035] Furthermore, the control device 15 has the function of receiving input signals from the input interface 43 mounted on the console device 40 or the platform device 10, and controlling the operation of the platform device 10 and the examination bed device 30. For example, the control device 15 controls the rotation of the rotating frame 13 upon receiving input signals, controls the tilting of the platform device 10, and controls the movement of the examination bed device 30 and the top plate 33. In addition, the control of tilting the platform device 10 can also be 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 43 mounted on the platform device 10. Furthermore, the control device 15 can be provided on either the platform device 10 or the console device 40.

[0036] The wedge 16 is a filter used to adjust the X-ray dose of the X-rays 100 irradiated from the X-ray tube 11. Specifically, the wedge 16 is a filter that allows the X-rays 100 irradiated from the X-ray tube 11 to pass through and attenuate, so that the X-rays 100 irradiated from the X-ray tube 11 onto the subject P are distributed in a predetermined manner. The wedge 16 is, for example, a wedge filter or a bow-tie filter, formed by machining aluminum to a predetermined target angle and thickness.

[0037] The collimator 17 is a lead plate or the like used to narrow the X-ray 100 after passing through the wedge 16 to the X-ray irradiation range, and a slit is formed by the combination of multiple lead plates or the like.

[0038] The DAS (Data Acquisition System) 18 has multiple counting circuits. Each counting circuit includes an amplifier that amplifies the electrical signals output from each detection element of the X-ray detector 12, and an A / D converter that converts the amplified electrical signals into digital signals, generating the result of the counting process using the detection signals from the X-ray detector 12, i.e., detection data. The result of the counting process is data representing the number of X-ray photons allocated to each energy bin. An energy bin corresponds to a defined width of energy domain. For example, the DAS 18 counts the photons (X-ray photons) originating from X-rays irradiated from the X-ray tube 11 and passing through the subject P, generating the result of the counting process that identifies the energy of the counted photons as detection data. The DAS 18 is an example of a data collection unit.

[0039] The detection data generated by DAS18 is transferred to the control console device 40. The detection data is a collection of data including the channel number, column number, viewpoint number (also called projection angle) of the detector pixel of the generation source, and the dose value of the detected X-rays. Alternatively, the viewpoint number can be the order in which the viewpoints were collected (collection time) or a number representing the rotation angle of the X-ray tube 11 (e.g., 1 to 1000). The multiple counting circuits in DAS18 are implemented, for example, by a circuit group equipped with circuit elements capable of generating detection data. Furthermore, in this embodiment, the term "detection data" includes both the raw data detected by the X-ray detector 12 before preprocessing and the raw data after preprocessing. Alternatively, both the data before preprocessing (detection data) and the data after preprocessing may be collectively referred to as projection data.

[0040] The examination table device 30 is a device for placing and moving a subject P to be scanned. It includes a base 31, an examination table drive device 32, a top plate 33, and a top plate support frame 34. The base 31 is a housing that movably supports the top plate support frame 34 in the vertical direction. The examination table drive device 32 is a motor or actuator that moves the top plate 33, on which the subject P is placed, along the long axis of the top plate 33. The examination table drive device 32 moves the top plate 33 according to the control of the control console device 40 or the control device 15. The top plate 33, which is located on the upper surface of the top plate support frame 34, is the plate on which the subject P is placed. In addition, the examination table drive device 32 can also move the top plate support frame 34 along the long axis of the top plate 33, in addition to the top plate 33.

[0041] The control console 40 is a device that performs control of the gantry device 10 and generates CT image data based on the scanning results of the gantry device 10. The control console 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, the display 42, the input interface 43, and the processing circuit 44 is performed via a bus.

[0042] The memory 41 is implemented, for example, by semiconductor memory elements such as RAM (Random Access Memory), flash memory, HDD (Hard Disk Drive), SSD (Solid State Drive), optical disc, etc. Furthermore, the memory 41 can also be a drive device for reading and writing various information between removable storage media such as CD (Compact Disc), DVD (Digital Versatile Disc), flash memory, or semiconductor memory elements such as RAM (Random Access Memory). The memory 41 stores, for example, projection data and reconstructed image data. Furthermore, the storage area of ​​the memory 41 can be located either within the PCCT device 1 or in an external storage device connected via a network. Additionally, the memory 41 stores control programs related to this embodiment. Moreover, the memory 41 is an example of a storage unit.

[0043] Display 42 displays various information. For example, display 42 outputs medical images (CT images) generated by processing circuit 44 and a GUI (Graphical User Interface) for handling various operations from the operator. For example, display 42 can be a liquid crystal display (LCD), an organic EL display (OELD), a plasma display, or any other type of display. Furthermore, display 42 can also be mounted on stand 10. Additionally, display 42 can be desktop type or a tablet terminal capable of wireless communication with the main control unit 40.

[0044] Input interface 43 accepts various input operations from the operator, converts the accepted input operations into electrical signals, and outputs them to processing circuit 44. For example, input interface 43 accepts collection conditions when collecting projection data, reconstruction conditions when reconstructing CT images, and image processing conditions when generating post-processed images from CT images. As input interface 43, appropriate devices such as mice, keyboards, trackballs, switches, buttons, joysticks, touchpads, and touch panel displays can be used.

[0045] Furthermore, in this embodiment, the input interface 43 is not limited to a structure that includes physical operating components such as a mouse, keyboard, trackball, switch, button, joystick, touchpad, and touch panel display. For example, a processing circuit that receives electrical signals corresponding to input operations from an external input device that is separately provided from the device and outputs such electrical signals to the processing circuit 44 is also included in the example of the input interface 43. In addition, the input interface 43 is an example of an input unit. Furthermore, the input interface 43 may also be provided on the stand device 10. Furthermore, the input interface 43 may also be composed of a tablet terminal or the like that capable of wireless communication with the main body of the control console device 40.

[0046] The processing circuit 44 controls the overall operation of the PCCT device 1 based on the electrical signal of the input operation output from the input interface 43. For example, the processing circuit 44 includes system control function 441, preprocessing function 442, reconstruction processing function 443, scan control function 444, image processing function 445, display control function 446, and decision function 447. Here, for example... Figure 1 The components of the processing circuit 44 shown, namely system control function 441, preprocessing function 442, reconstruction processing function 443, scanning control function 444, image processing function 445, display control function 446, and decision function 447, are all executed in the form of a program that can be executed by a computer and are recorded in the memory 41.

[0047] The processing circuit 44, for example, is a processor that reads and executes programs from the memory 41 to achieve the functions corresponding to the read programs. In other words, the processing circuit 44, which reads the state of each program, has the ability to... Figure 1 The processing circuit 44 represents the various functions. The processing circuit 44 that implements system control function 441 is an example of a control unit. The processing circuit 44 that implements preprocessing function 442 is an example of a preprocessing unit. The processing circuit 44 that implements reconstruction processing function 443 is an example of a reconstruction processing unit. The processing circuit 44 that implements scan control function 444 is an example of a scan control unit. The processing circuit 44 that implements image processing function 445 is an example of an image processing unit. The processing circuit 44 that implements display control function 446 is an example of a display control unit. The processing circuit 44 that implements decision function 447 is an example of a decision unit. Alternatively, the processing circuit 44 may also be used as an example of a control unit.

[0048] In addition, Figure 1The diagram illustrates a scenario where system control function 441, preprocessing function 442, reconstruction processing function 443, scanning control function 444, and display control function 446 are implemented by a single processing circuit 44. However, this embodiment is not limited to this. For example, the processing circuit 44 may also be configured by combining multiple independent processors, with each processor executing its own program to implement each processing function. Furthermore, the processing functions of the processing circuit 44 may be appropriately distributed or combined into one or more processing circuits for implementation.

[0049] The processing circuit 44 controls various functions based on input operations received by the operator from the system control function 441 via the input interface 43.

[0050] The processing circuit 44 generates preprocessed data through the preprocessing function 442, which performs logarithmic transformation, offset correction, inter-channel sensitivity correction, and harness hardening correction on the ideal detection data determined by the determination function 447. The ideal detection data will be explained later.

[0051] The processing circuit 44 uses the reconstruction processing function 443 to reconstruct the projection data generated by the preprocessing function 442 using methods such as filter-corrected inverse projection or successive approximate reconstruction, and generates CT image data.

[0052] The processing circuit 44 acquires two-dimensional positioning image data of the subject P through the scan control function 444, which is used to determine the scanning range, imaging conditions, etc. Alternatively, the positioning image data may also be referred to as scan image data or scout image data.

[0053] The processing circuit 44, through the image processing function 445, transforms the CT image data generated by the reconstruction processing function 443 based on input operations received from the operator via the input interface 43 into tomographic image data of arbitrary sections or three-dimensional image data using known methods. Alternatively, the generation of three-dimensional image data can also be performed directly by the reconstruction processing function 443.

[0054] The processing circuit 44, through the display control function 446, enables the display 42 to display the tomographic image data and three-dimensional image data processed by the image processing function 445. Furthermore, the display control function 446 enables the display 42 to display various GUIs (Graphical User Interfaces).

[0055] Processing circuit 44, through determination function 337, determines an output corresponding to the reconstruction position of the first detection element, based on a first output related to a first detection element included in the plurality of radiation detection elements (the plurality of detection elements of X-ray detector 12) and a second output related to a second detection element surrounding the first detection element. This reconstruction position is, for example, used in a calculation of reconstruction based on the determined output and represents the location of a representative point of the first detection element. The reconstruction position is, for example, the surface (cathode surface) where X-rays reach in the first detection element. Furthermore, the reconstruction position is not limited to the cathode surface of the first detection element. For example, it could be any position within the semiconductor crystal on the anode electrode of the first detection element. Hereinafter, for the sake of detail, it is assumed that the reconstruction position is the incident position of X-rays on the cathode surface of the first detection element.

[0056] Processing circuit 44, through decision function 337, determines an ideal output related to the first detection element, based on a first output related to a first detection element included among the plurality of detection elements of the X-ray detector 12, and a second output related to a second detection element surrounding the first detection element, when the surface (cathode surface) where the X-ray reaches in the first detection element is set as the incident position of the X-ray. The incident position of the X-ray is, for example, the surface of the X-ray detector 12 where the X-ray path (also called a line) leading to the first detection element first encounters. In other words, the incident position of the X-ray corresponds to, for example, the position where the X-ray path that has passed through the subject P, rather than a scattered X-ray, or a direct line path that has not passed through the subject P, encounters the cathode surface.

[0057] The second detection element is not limited to at least one detection element adjacent to the first detection element, but may also be a plurality of detection elements surrounding the first detection element. The first output corresponds to the detection data (pure raw data or counts) related to the first detection element, and the second output corresponds to the detection data (pure raw data or counts) related to the second detection element. Furthermore, in the case of a radiological diagnostic device such as an X-ray diagnostic device or an integrating X-ray CT device, for example, the first output corresponds to the pure raw data output from the first detection element, and the second output corresponds to the pure raw data output from the second detection element.

[0058] The ideal output, for example, corresponds to the output (e.g., count or current value) related to the first electrode when electrons generated by the X-ray are read out by the first electrode when the X-ray is obliquely incident on the cathode surface (hereinafter referred to as the opposing surface) opposite the readout electrode (hereinafter referred to as the first electrode) of the first detection element. For example, the opposing surface corresponds to the surface directly above the first electrode along the Y-axis direction. Furthermore, the second detection element is preset according to the incident angle of the ray of the X-ray obliquely incident on the opposing surface. In the PCCT apparatus 1, the first output, the second output, and the output corresponding to the reconstruction position of the first detection element (e.g., also referred to as the ideal output) are counts obtained by counting photons in the X-ray. At this time, the ideal output corresponds to the output count when the surface of the X-ray detector 12, which is first encountered by the X-ray path leading to the first detection element, is taken as the incident position of the X-ray.

[0059] Specifically, the processing circuit 44, through the determination function 447, determines the output corresponding to the reconstruction position of the first detection element (the ideal output related to the first detection element) in a direction (e.g., the column direction) within a two-dimensional direction (channel direction and column direction) where multiple detection elements are arranged, using a first weight corresponding to a first angle from the reference line to the first detection element and a second weight corresponding to a second angle from the reference line to the second detection element. That is, the determination function 447 performs a weighted calculation for each of the multiple detection elements of the X-ray detector 12 using the outputs of the detection elements surrounding each of the detection elements, thereby statistically calculating the output that each detection element would normally expect to be the output, i.e., the most likely ideal output.

[0060] The baseline is, for example, the line connecting the center (mid-plane) of the cone direction of the X-ray detector 12 to the focal point of the tube. The first and second weights are set based on the material in the first and second detection elements that converts X-rays (radiation) into electrons or visible light, the thickness of that material, and the angle at which the X-rays are incident on the first detection element. For example, in the case of a direct-conversion type X-ray detector, the material is a semiconductor crystal. Furthermore, 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 are incident on the first detection element corresponds to the first angle described above. The first and second weights are preset, for example, through various simulations (e.g., Monte Carlo simulations) using the first angle, the thickness of the semiconductor crystal, and the material, or through prior calibration tests (experiments).

[0061] When the direction within the plane including the first and second detection elements is, for example, the cone-angle direction (column direction), that is, when the first and second detection elements are arranged along the cone-angle direction, the angle from the reference line to the first detection element is equivalent to the angle between the line connecting the first detection element to the focus of the tube and the reference line (hereinafter referred to as the first cone angle). Furthermore, when the direction within the plane including the first and second detection elements 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 cone angle) is equivalent to the angle between the line connecting the second detection element to the focus of the tube and the reference line.

[0062] That is, when the first detection element and the second detection element are arranged along the cone angle direction, the processing circuit 44, through the determination function 447, uses a first weight corresponding to the first cone angle from the reference line to the first detection element and a second weight corresponding to the second cone angle from the reference line to the second detection element. For example, it adds the first multiplication value obtained by multiplying the first output by the first weight to the second multiplication value obtained by multiplying the second output by the second weight, and determines the output corresponding to the reconstruction position of the first detection element (the ideal output related to the first detection element).

[0063] Figure 2 This diagram shows a portion of the X-ray detector 12 located at the end of the plane closest to the opening, along with X-rays obliquely entering the X-ray detector 12. More specifically... Figure 2 The end of the opening on the + side of the Z-axis direction, i.e., the distance... Figure 1 The part of the opening near the end of the Z-axis direction of the top plate 131 (the foot of the subject P) is shown together with the X-ray detector 12 and the X-rays obliquely entering the X-ray detector 12.

[0064] exist Figure 2 In the above, it is assumed that the first detection element is the readout electrode C. N Furthermore, in Figure 2 A portion of the X-rays N generated in X-ray tube 11 seg This shows the readout electrode C corresponding to the first detection element. N X-rays (hereinafter referred to as oblique-incident X-rays) that enter obliquely at the opposing cathode surfaces (opposing surfaces). Figure 2 In the middle, from the readout electrode C N The first output is relative to the multiple readout electrodes (readout electrode C) caused by obliquely incident X-rays. N Reading electrode C N+1 Reading electrode C N+2 The percentage of the total output is represented by 70%. In other words, the aforementioned 70% represents the percentage at the readout electrode C. NIn the semiconductor crystal surrounded by dotted lines in the region directly above, a portion of the X-rays N seg The proportion that is converted into electric charge.

[0065] In addition, Figure 2 In the middle, from the readout electrode C N+1 The second output is relative to the output from multiple readout electrodes (readout electrode C) caused by obliquely incident X-rays. N Reading electrode C N+1 Reading electrode C N+2 The percentage of the total output is represented by 29%. In other words, the aforementioned 29% represents the percentage at the readout electrode C. N+1 In the semiconductor crystal surrounded by dotted lines in the region directly above, a portion of the X-rays N seg The proportion that is converted into electric charge.

[0066] In addition, Figure 2 In the middle, from the readout electrode C N+2 The second output is relative to the output from multiple readout electrodes (readout electrode C) caused by obliquely incident X-rays. N Reading electrode C N+1 Reading electrode C N+2 The percentage of the total output is represented by 1%. In other words, the aforementioned 1% represents the percentage of the total output at the readout electrode C. N+2 In the semiconductor crystal surrounded by dotted lines in the region directly above, a portion of the X-rays N seg The proportion converted into electric charge. Figure 2 In the example shown, the second detection element and the readout electrode C N+1 and readout electrode C N+2 Two correspondences.

[0067] That is, in the envision Figure 2 Given the geometry of the detection element and the oblique ingress of X-rays as shown, regarding a portion of the X-ray N... seg , from readout electrode C N 70% of the output comes from the readout electrode C. N+1 29% of the output and from the readout electrode C N+2 1% of the output contributes to the ideal output C of the first output. iN Specifically, in Figure 2 In the example shown, with the first detection element (readout electrode C) N The ideal output C iN It is calculated by the following formula (1).

[0068] C iN =k N,N ×C N +k N，N+1 ×CN+1 +k N，N+2 ×C N+2 …(1)

[0069] On the right side of equation (1), C N This indicates the first detection element, i.e., the readout electrode C. N The relevant output (first output). Furthermore, on the right-hand side of equation (1), C N+1 and C N+2 This indicates the relationship with the second detection element (readout electrode C). N+1 and readout electrode C N+2 The second output is related to ). Furthermore, on the right-hand side of equation (1), k N，N Indicates the first weight, k N，N+1 and k N，N+2 This indicates the second weight. For example... Figure 2 As shown, the first weight k N，N It is 0.7, the second weight k N，N+1 k N，N+2 The values ​​are 0.29 and 0.01, respectively. Therefore, the processing circuit 44, through the determination function 447, uses the following calculation formula (2) to determine the value of the first detection element (readout electrode C). N The ideal output C iN .

[0070] C iN =0.7×C N +0.29×C N+1 +0.1×C N+2 …(2)

[0071] Figure 2 The values ​​of the first and second weights in equation (2) (0.7, 0.29, 0.01) are examples that vary depending on the angle of incidence of the X-rays to the first detection element, i.e., the column number. Generally, when the total number of detection elements along the column direction is n, and they are assigned numbers from 1 to n along the cone angle direction (Z-axis direction), equation (1) is generalized by the following equation (3).

[0072]

[0073] The vector on the left side of equation (3) above

[0074]

[0075] This represents an ideal output vector with multiple ideal outputs corresponding to multiple detection elements as components. Furthermore, the vector on the right-hand side of equation (3) above...

[0076]

[0077] This represents a measured output vector, which consists of multiple outputs (measured values) corresponding to multiple detection elements.

[0078] Furthermore, the matrix on the right side of equation (3) above (hereinafter referred to as the weight matrix)

[0079]

[0080] Multiple weights associated with multiple detection elements are represented as matrices. In other words, the weight matrix is ​​equivalent to a measured output vector representing the measured values ​​of the output associated with the X-ray detector 12.

[0081]

[0082] And represents the ideal output vector related to the ideal output of X-ray detector 12.

[0083]

[0084] The correlation coefficients of each component (the outputs associated with each of the multiple detection elements) are used as the coefficient matrix (e.g., the correlation matrix) for the weights. When the total number of detection elements n along the column direction is odd, the element number n / 2+1 corresponds to the midplane. In this case, the weight k... n / 2+1，i (1≤i≤n: all values ​​except n / 2+1) are zero, weight k n / 2+1，n / 2+1 The value is 1. Furthermore, ideally, the coefficient matrix is ​​a matrix with components that are symmetric with respect to the diagonal connecting the 1-row N-column and N-row 1-column axes.

[0085] Qualitatively, in the weight matrix, the larger the cone angle of a detection element, the greater the weight of its adjacent elements (and multiple detection elements along that larger direction, including the adjacent element) in the direction with a larger cone angle, and the smaller the weight related to the output of the detection element itself. For example, in the diagonal component of the weight matrix, as the number of rows and columns increases or decreases, the first weight changes from the weight k corresponding to the midplane. n / 2，n / 2 The weight decreases. Furthermore, for example, in the off-diagonal components of the weight matrix, as the number of rows and columns increases or decreases, the second weight associated with the second detection element along the direction with the larger cone angle decreases from the weight k corresponding to the midplane. n / 2，n / 2 The weight increases. In other words, in the weight matrix, for each of the multiple detection elements, as the first angle increases, the first weight decreases and the second weight increases. The weight matrix generated by various simulations (e.g., Monte Carlo simulations) or through prior calibration experiments is stored in memory 41.

[0086] In the Figure 2In the examples of the above numerical expressions, only the cone angle direction is considered, but the sector angle direction can also be considered instead of the cone angle direction. Furthermore, for example, when an FPD is used as an X-ray detector 12, i.e., when the incident angle of X-rays increases in a channel with a larger sector angle, the dimension of the matrix operations in the above numerical expressions can be expanded. In this case, the measured output vector and the ideal output vector are, for example, matrices representing the outputs related to multiple detection elements with respect to the cone angle direction and the sector angle direction, and the weight matrix is ​​a fourth-order tensor with the cone angle direction and the sector angle direction as independent variables (tails).

[0087] Furthermore, the processing described above by the decision function 447 can also be implemented by the preprocessing function 442. In this case, before the preprocessing is executed, the preprocessing function 442 performs the processing based on the decision function 447 on the unprocessed data (e.g., counts). Additionally, the processing described above by the decision function 447 can also be implemented by the DAS 18. In this case, the DAS 18 performs the processing based on the decision function 447 on the detection data (e.g., pure raw data or raw data (counts)).

[0088] The processing circuit 44 outputs the ideal output determined by the determination function 447 for each of the multiple detection elements to the preprocessing function 442. The ideal output determined by the determination function 447 corresponds to the correction of the effect of the oblique ingress of X-rays relative to the X-ray detector 12. That is, the ideal output is equivalent to the corrected data after the effect of the oblique ingress of X-rays relative to the X-ray detector 12 has been corrected. The preprocessing function 442 performs preprocessing on the corrected data to generate projection data (hereinafter referred to as corrected projection data). This corrected projection data corresponds to the projection data after the effect of the oblique ingress of X-rays relative to the X-ray detector 12 has been reduced. The reconstruction processing function 443 generates a reconstructed image (hereinafter referred to as a corrected reconstructed image) by reconstructing the corrected projection data. That is, the processing circuit 44 performs reconstruction processing on the projection data based on the output corresponding to the reconstruction position through the reconstruction processing function 443 to generate a reconstructed image (corrected reconstructed image). The corrected reconstructed image is stored, for example, in the memory 41 and displayed on the display 42 through the display control function 446. The corrected reconstructed image is equivalent to the reconstructed image after the effect of the oblique ingress of X-rays relative to the X-ray detector 12 has been corrected.

[0089] The overall structure of PCCT device 1, as an example of a radiological diagnostic device, has been described above. Hereinafter, using... Figure 3 The order of output decision processing is explained. Based on the collected first and second outputs, the output decision processing determines the output corresponding to the reconstruction position of the first detection element. Figure 3 This is a flowchart illustrating an example of how the output determines the order of processing.

[0090] (Output determines processing)

[0091] (Step S301)

[0092] The data acquisition circuit 18 collects a first output relating to a first detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction, and a second output relating to a second detection element surrounding the first detection element, by scanning the subject P. Thus, the first output and the second output are obtained.

[0093] (Step S302)

[0094] Processing circuit 44, through determination function 447, determines the 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 this reconstructed position is omitted from the explanation given above.

[0095] The radiodiagnostic apparatus of the first embodiment described above determines an output (e.g., an ideal output related to the first detection element) corresponding to the reconstruction position of the first detection element based on a first output related to a first detection element included in a plurality of radiodiagnostic elements arranged in a two-dimensional direction, and a second output related to a second detection element surrounding the first detection element. For example, the radiodiagnostic apparatus of this embodiment determines the output (e.g., an ideal output) corresponding to the reconstruction position in a direction in a two-dimensional plane including the first and second detection elements using a first weight corresponding to a first angle from the reference line to the first detection element and a second weight corresponding to a second angle from the reference line to the second detection element. Specifically, the radiodiagnostic apparatus of this embodiment determines the output (e.g., an ideal output) corresponding to the reconstruction position by adding a first multiplication value obtained by multiplying the first output by the first weight to a second multiplication value obtained by multiplying the second output by the second weight.

[0096] For example, the radiological diagnostic apparatus of the first embodiment is an X-ray CT apparatus, with two-dimensional directions being the cone-angle direction and the sector-angle direction, and the radiation being X-rays. A first detection element and a second detection element are arranged along the cone-angle direction. Using the aforementioned first weight corresponding to the first cone angle from the reference line to the first detection element and a second weight corresponding to the second cone angle from the reference line to the second detection element, the output corresponding to the reconstruction position (e.g., the ideal output) is determined. In this case, in the radiological diagnostic apparatus of this embodiment, the first output, the second output, and the output corresponding to the reconstruction position (e.g., the ideal output) can also be counts obtained by counting photons in the X-rays. The radiological diagnostic apparatus of this embodiment performs reconstruction processing on projection data based on the output (e.g., the ideal output) corresponding to the reconstruction position to generate a reconstructed image. Furthermore, in the radiological diagnostic apparatus of the first embodiment, the first weight and the second weight are set based on the material of the first detection element and the second detection element that converts radiation into electrons or visible light, the thickness of the material, and the angle at which the radiation is incident on the first detection element (i.e., the incident angle of X-rays obliquely incident on the opposing surface). As the first angle increases, the first weight decreases and the second weight increases.

[0097] Because of these, according to the radiological diagnostic apparatus of the first embodiment, the influence on the pure raw data or raw data caused by the oblique intrusion of X-rays toward the opposing plane due to at least one of the cone angle and the sector angle can be corrected. Therefore, according to this radiological diagnostic apparatus, the positional deviation of the detection position of the radiation caused by the oblique intrusion of X-rays can be corrected, and projection data at the position corresponding to the original detection position of the X-rays can be obtained. Because of the above, according to this radiological diagnostic apparatus, the image quality degradation such as image elongation in the body axis direction and / or left-right direction of the subject P is reduced, and medical images (X-ray images based on projection data or corrected reconstructed images) with improved spatial resolution can be generated. Therefore, according to this radiological diagnostic apparatus, the quality of radiological examination of the subject P can be improved.

[0098] (Application Example)

[0099] PCCT apparatus 1 collects data (counts) for each energy domain (energy chamber). Furthermore, the semiconductor crystal of the X-ray detector 12 in PCCT apparatus 1 has a smaller X-ray absorption cross-section compared to a conventional integrating X-ray detector. Therefore, the thickness of the X-ray detector 12 in PCCT apparatus 1 is thicker than that of a conventional integrating X-ray detector. Because of this, the higher the X-ray energy, the greater the effect of the oblique intrusion of the X-rays on the reconstructed image. That is, in conventional PCCT apparatus 1, the higher the energy of the energy chamber represented by the reconstructed image, the more elongated the image is along the body axis of the subject P.

[0100] Therefore, this application example uses multiple weight matrices corresponding to multiple energy chambers to determine the ideal output for each of the multiple energy chambers. In the multiple weight matrices, the contribution rate k of the detection element corresponding to the first weight is... N，N The decrease corresponds to the contribution rate k of the second detection element (including adjacent elements) in the X-ray detector 12, which is closer to the end on the + side of the Z-axis direction, to the second weight of the first detection element. N，N’>N Increase. Furthermore, in multiple weight matrices, the contribution rate k corresponding to the second weight of the second detection element (including adjacent elements) in the X-ray detector 12, which is closer to the end on the Z-axis side, to the second weight of the first detection element. N，N’<N Increase. In other words, among the multiple representative energies representing multiple energy cells, the higher the energy, the lower the primary weight of each energy cell; and among the multiple representative energies, the higher the energy, the higher the secondary weight of each energy cell.

[0101] The first output of this application example is, for example, a plurality of first counts corresponding to the plurality of energy chambers of X-rays. Furthermore, the second output of this application example is, for example, a plurality of second counts corresponding to the plurality of energy chambers of X-rays. At this time, the processing circuit 44, through the determination function 447, determines, based on the first weight, the second weight, the first count, and the second count, the count as the output (e.g., the ideal output) corresponding to the reconstructed position of each of the plurality of energy chambers.

[0102] Specifically, the processing circuit 44 determines the output (e.g., the ideal output) corresponding to the reconfiguration position of each of the multiple energy cells by using the following equation (4) through the determination function 447.

[0103]

[0104] The vector on the left side of equation (4) above

[0105]

[0106] This represents the ideal output vector of each energy cell, which, as a component, has an output (e.g., an ideal output) corresponding to multiple reconstruction positions respectively corresponding to multiple detection elements. Furthermore, the vector on the right-hand side of equation (4) above...

[0107]

[0108] This represents the measured output vector of each energy cell, which is a component of a vector and has multiple outputs (measured values) corresponding to multiple detection elements.

[0109] Furthermore, the weight matrix of each energy cell on the right side of equation (4) above

[0110]

[0111] The weights associated with multiple detection elements are represented as matrices for each energy chamber. All energy chambers on both sides of equation (4) represent the same energy chamber. The weight matrix for each energy chamber is equivalent to representing the measured output vector of each energy chamber.

[0112]

[0113] and the ideal output vector of each energy cell

[0114]

[0115] The correlation coefficients of each component (the outputs associated with each of the multiple detection elements) are represented as a weighted coefficient matrix (e.g., a correlation matrix). Other features in the weight matrix of each energy chamber are the same as in the first embodiment, so descriptions are omitted. Furthermore, the processing in the determination function 447 is also performed repeatedly for each energy chamber in the same manner as in the first embodiment, so descriptions are omitted.

[0116] In the radiodiagnostic apparatus of the application example of the first embodiment described above, the first output is a plurality of first counts corresponding to a plurality of energy chambers of X-rays, and the second output is a plurality of second counts corresponding to a plurality of energy chambers. For each of the plurality of energy chambers, based on the first weight, the second weight, the first count, and the second count, a count is determined as the output (e.g., the ideal output) corresponding to the reconstructed position of each of the plurality of energy chambers. Furthermore, in the radiodiagnostic apparatus of this application example, among the plurality of representative energies representing the plurality of energy chambers, the higher the energy, the lower the first weight of each of the plurality of energy chambers; and among the plurality of representative energies, the higher the energy, the higher the second weight of each of the plurality of energy chambers.

[0117] As described above, according to the radiological diagnostic apparatus of the application example of the first embodiment, since the contribution rate varies depending on the energy of the X-rays, it is possible to use the weight matrix (coefficient matrix) of each energy chamber to correct the counts measured independently for each energy chamber. According to the radiological diagnostic apparatus of this application example, more accurate correction can be made regarding the oblique intrusion of X-rays, further improving the accuracy of the count correction. Furthermore, in semiconductor detectors used as X-ray detectors 12, since the X-ray cross-sectional area is small, there is a tendency for the influence of the oblique intrusion of X-rays to increase; therefore, according to the radiological diagnostic apparatus of this application example, the correction effect can be further enhanced.

[0118] In addition, according to the radiological diagnostic apparatus of this application example, the difference in the effect of the oblique intrusion between energy chambers during spectral imaging through the calculation of the determination function 447 can be mitigated, and the effect of the oblique intrusion of X-rays can be accurately corrected in counting imaging, which is a cumulative process of spectral imaging. That is, according to the radiological diagnostic apparatus of this application example, the degree of positional deviation, which varies depending on the energy chamber, can be corrected for each energy chamber, so the positional deviation between energy chambers is corrected, and accurate spectral imaging can be performed. Because of these, according to the radiological diagnostic apparatus of this application example, the spatial resolution of the reconstructed image in the volume axis direction can be improved. Other effects are the same as in the first embodiment, so descriptions are omitted.

[0119] (Modified Example)

[0120] This variation involves an X-ray detector 12 composed of multiple small modules each having multiple detection elements. That is, in this variation of the X-ray detector 12, instead of a single structure where multiple detection elements are arranged in a two-dimensional manner, a large-area surface detector is constructed by arranging detectors in small module units. In this case, when the small modules are arranged in the designed positions, gaps will inevitably occur between adjacent small modules.

[0121] Figure 4 Regarding this modified example, the figure shows a portion of the X-ray detector 12 on the end side closer to the opening than the midplane, together with the X-rays obliquely entering the X-ray detector 12. Figure 2 and Figure 4 The difference lies in the Nth readout electrode C N With the (N+1)th readout electrode C N+1 There are gaps between them. For example... Figure 4 As shown, X-rays obliquely inserted into the gap are directed toward the readout electrode C containing the adjacent element. N The surrounding detection elements are angled inwards. The components in the weight matrix of this variant example are as follows: Figure 4 As shown, the setting takes into account the gap. That is, as... Figure 4 As shown, at the corresponding readout electrode C N When there is a gap between the first detection element and the second detection element, the first weight is set to be smaller than that when there is no gap, and the second weight is set to be larger than that when there is no gap.

[0122] Through these means, according to this modification, the components (correction terms) in the weight matrix of the first embodiment and the application example of the first embodiment can be set considering the increase in the oblique intrusion of X-rays caused by the gap, and it is possible to compensate for the discontinuity of the measured output caused by the gap between the small modules of the X-ray detector 12. That is, according to this modification, in regions where multiple detector modules that are modularized are spliced ​​together, where the gap between the detector modules is not equidistant to prevent interference, or in regions where the influence of the oblique intrusion of X-rays into adjacent elements increases due to the gap between the detector modules, it is also possible to calculate the ideal output by setting the weights. Other effects of this modification are the same as those of the first embodiment and the application example of the first embodiment, so descriptions are omitted.

[0123] (Second Implementation)

[0124] The difference from the first embodiment is that the radiation detector has a processing circuit that performs the decision function 447. Hereinafter, for the sake of detail, it is assumed that the radiation detector is an X-ray detector mounted in a PCCT device. In this case, Figure 1 In the PCCT device 1 shown, the decision function 447 in the processing circuit 44 is no longer needed.

[0125] Figure 5 This is a diagram showing an example of the structure of an X-ray detector 20 corresponding to the radiation detector of this embodiment. (See diagram for example.) Figure 5 As shown, the X-ray detector 20 includes a plurality of X-ray detection elements 21, a data collection circuit (DAS) 18, and a processing circuit 23. The plurality of X-ray detection elements 21, arranged in a two-dimensional direction, are the same as in the first embodiment, so description is omitted. Furthermore, the plurality of X-ray detection elements 21 may correspond, for example, to a plurality of radiation detection elements.

[0126] For example, DAS18 collects a first count based on the output from a first detection element included in a plurality of X-ray detection elements, and collects a second count based on the output from a second detection element surrounding the first detection element. The structure and function of DAS18 are the same as in the first embodiment, so description is omitted.

[0127] The processing circuit 23, for example, is a processor that reads and executes programs from the memory 41 to implement the functions corresponding to each read program. The hardware structure of the processing circuit 23 is the same as in the first embodiment, so its description is omitted. The processing circuit 23, through the determination function 447, determines an ideal count related to the first detection element, based on the first count and the second count, when the surface where the radiation first reaches the first detection element is set as the incident position of the radiation. The specific processing performed by the determination function 447 is the same as in the first embodiment, so its description is omitted. Furthermore, the processing order of the output determination processing in this embodiment is the same as in the first embodiment, so its description is omitted.

[0128] As examples of applications and modifications of the second embodiment, since examples of applications and modifications of the first embodiment can be appropriately utilized, descriptions are omitted. Furthermore, the effects of the second embodiment are the same as those of the first embodiment, so descriptions are also omitted.

[0129] In implementing the technical concept of this embodiment through an output determination method, the output determination method collects 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. Based on the first and second outputs, it determines the output corresponding to the reconstructed position of the first detection element. The processing order and effects of this output determination method are the same as those of the first embodiment, so the description is omitted.

[0130] In implementing the technical concept of this embodiment through an output determination procedure, the output determination procedure enables a computer to perform the following processing: collecting 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; and determining an output corresponding to the reconstruction position of the first detection element based on the first and second outputs. At this time, the program enabling the computer to execute this method can also be saved to a storage medium such as a disk (hard disk, etc.), optical disk (CD-ROM, DVD, etc.), or semiconductor memory and distributed. The processing order and effects in the output determination procedure are the same as in the first embodiment, so the description is omitted.

[0131] According to at least one of the embodiments described above, the effects caused by the oblique entry of radiation into the radiation detector can be reduced.

[0132] Several embodiments of the present invention have been described, but these embodiments are merely illustrative and not intended to limit the scope of the invention. These new embodiments can be implemented in a wide 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 within the scope or spirit of the invention, and are included within the scope of the invention as described in the claims and its equivalents.

[0133] Regarding the above-described embodiments, the following notes are disclosed as a technical solution and optional feature of the invention.

[0134] (Postscript 1)

[0135] A radiation detector includes: a plurality of radiation detection elements arranged in a two-dimensional direction; and a determination unit that determines an output corresponding to the reconstruction position of the first detection element 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.

[0136] (Postscript 2)

[0137] Alternatively, the decision unit may use a first weight corresponding to a first angle from the reference line to the first detection element and a second weight corresponding to a second angle from the reference line to the second detection element in the plane containing the first and second detection elements in the two-dimensional direction to determine the output corresponding to the reconstructed position; the second weight is provided to each of the plurality of second detection elements.

[0138] (Note 3)

[0139] Alternatively, the decision unit may determine the output corresponding to the reconstructed position by adding the first multiplication value obtained by multiplying the first output by the first weight to the second multiplication value obtained by multiplying the second output by the second weight.

[0140] (Postscript 4)

[0141] Alternatively, the aforementioned radiation detector is mounted on an X-ray computed tomography apparatus; the aforementioned two-dimensional direction is the cone angle direction and the sector angle direction; the aforementioned radiation is X-ray; the aforementioned first detection element and the aforementioned second detection element are arranged along the aforementioned cone angle direction; the aforementioned determination unit uses the aforementioned first weight corresponding to the first cone angle from the reference line to the first detection element and the aforementioned second weight corresponding to the second cone angle from the aforementioned reference line to the second detection element to determine the output corresponding to the aforementioned reconstruction position.

[0142] (Note 5)

[0143] Alternatively, the first output, the second output, and the output corresponding to the reconstructed position mentioned above can be the count obtained by counting the photons in the X-rays mentioned above.

[0144] (Note 6)

[0145] Alternatively, the first output may be a plurality of first counts corresponding to the plurality of energy chambers of the X-ray; the second output may be a plurality of second counts corresponding to the plurality of energy chambers; and the decision unit may, based on the first weight, the second weight, the first count, and the second count, determine the count as the output corresponding to the reconstructed position of each of the plurality of energy chambers.

[0146] (Note 7)

[0147] Alternatively, among the multiple representative energies representing the aforementioned multiple energy chambers, the higher the energy, the lower the aforementioned first weight of each of the aforementioned multiple energy chambers; and among the multiple representative energies, the higher the energy, the higher the aforementioned second weight of each of the aforementioned multiple energy chambers.

[0148] (Note 8)

[0149] Alternatively, the first weight and the second weight may be set based on the material in the first and second detection elements that converts the radiation into electrons or visible light, the thickness of the material, and the first angle at which the radiation is incident on the first detection element; as the first angle increases, the first weight decreases and the second weight increases.

[0150] (Note 9)

[0151] Alternatively, when there is a gap between the first detection element and the second detection element, the first weight is set to be smaller than when there is no gap, and the second weight is set to be larger than when there is no gap.

[0152] (Postscript 10)

[0153] An X-ray computed tomography apparatus is provided for mounting the radiation detector described in any one of Appendices 1 to 10, and includes a reconstruction processing unit that performs reconstruction processing on projection data based on output corresponding to the reconstruction position and generates a reconstructed image.

[0154] (Postscript 11)

[0155] Alternatively, the reconstructed position may be the position used in the calculation of the reconstruction based on the above output and represented by the representative point of the first detection element.

[0156] (Postscript 12)

[0157] Alternatively, it may also include a data collection circuit that collects a first count based on the output of a first detection element included in the plurality of radiation detection elements and collects a second count based on the output of a second detection element surrounding the first detection element; the decision unit determines the count corresponding to the reconstructed position of the first detection element based on the first count and the second count.

[0158] (Postscript 13)

[0159] An X-ray computed tomography apparatus comprising the radiation detector described in any one of Appendices 1 to 12.

[0160] (Postscript 14)

[0161] An output determination method collects a first output relating to a first detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction, and a second output relating to a second detection element surrounding the first detection element; and determines an output corresponding to the reconstructed position of the first detection element based on the first output and the second output.

[0162] (Postscript 15)

[0163] A computer-readable non-volatile storage medium stores an output determination program that enables a computer to: collect a first output relating to a first detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction, and a second output relating to a second detection element surrounding the first 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.

Claims

1. A radiological diagnostic device, wherein, have: Multiple radiation detection elements are arranged in a two-dimensional direction; and The processing circuit, based on a first weight corresponding to a first angle from the reference line to the first detection element, a second weight corresponding to a second angle from the reference line to the second detection element, a first output related to the first detection element included in the plurality of radiation detection elements, and a second output related to the second detection element included in the plurality of radiation detection elements, in a direction within the plane including the first and second detection elements in the aforementioned two-dimensional direction, determines an output corresponding to the reconstructed position of the first detection element. The determined output is the ideal output corresponding to the case where the radiation is detected at the surface that is first reached by the first detection element as the incident position.

2. The radiological diagnostic device as claimed in claim 1, wherein, The aforementioned second weight is provided to each of the plurality of aforementioned second detection elements.

3. The radiological diagnostic device as described in claim 2, wherein, The processing circuit determines the output corresponding to the reconstructed position by adding the first multiplication value obtained by multiplying the first output by the first weight to the second multiplication value obtained by multiplying the second output by the second weight.

4. The radiological diagnostic apparatus as described in claim 2, wherein, The aforementioned radiological diagnostic device is an X-ray computed tomography (CT) device. The two-dimensional directions mentioned above are the cone angle direction and the sector angle direction. The aforementioned radiation is X-rays. The first detection element and the second detection element are arranged along the cone angle direction. The processing circuit described above uses the first weight corresponding to the first cone angle from the reference line to the first detection element and the second weight corresponding to the second cone angle from the reference line to the second detection element to determine the output corresponding to the reconstructed position.

5. The radiological diagnostic apparatus as described in claim 4, wherein, The first output, the second output, and the output corresponding to the reconstructed position are the counts obtained by counting the photons in the X-rays.

6. The radiological diagnostic apparatus as described in claim 5, wherein, The first output mentioned above refers to multiple first counts corresponding to the multiple energy chambers of the aforementioned X-ray. The second output mentioned above consists of multiple second counts corresponding to the aforementioned multiple energy cells. The aforementioned processing circuit determines, based on the first weight, the second weight, the first count, and the second count, the count corresponding to the reconstructed position of each of the plurality of energy chambers.

7. The radiological diagnostic apparatus as claimed in claim 6, wherein, Among the multiple representative energies representing the aforementioned multiple energy chambers, the higher the energy, the lower the aforementioned first weight of each of the aforementioned multiple energy chambers; Among the aforementioned representative energies, the higher the energy, the greater the increase in the second weight of each of the aforementioned energy chambers.

8. The radiological diagnostic apparatus as claimed in claim 2, wherein, The first weight and the second weight are set based on the material in the first detection element and the second detection element that converts the radiation into electrons or visible light, the thickness of the material, and the first angle at which the radiation is incident on the first detection element. As the first angle increases, the first weight decreases, and the second weight increases.

9. The radiological diagnostic apparatus as claimed in claim 2, wherein, When there is a gap between the first detection element and the second detection element, the first weight is set to be smaller than when there is no gap, and the second weight is set to be larger than when there is no gap.

10. The radiological diagnostic apparatus as claimed in claim 1, wherein, The aforementioned processing circuit performs reconstruction processing on the projection data based on the output corresponding to the aforementioned reconstruction position to generate a reconstructed image.

11. The radiological diagnostic apparatus as claimed in claim 1, wherein, The reconstructed position is the position used in the calculation of the reconstruction based on the above output and is used to represent the representative point of the first detection element.

12. A radiation detector, wherein, have: Multiple radiation detection elements are arranged in a two-dimensional direction; The data collection circuit collects a first count based on the output of a first detection element included in the plurality of radiation detection elements, and collects a second count based on the output of a second detection element surrounding the first detection element; and The processing circuit determines a count corresponding to the reconstructed position of the first detection element based on a first weight corresponding to the first angle from the reference line to the first detection element, a second weight corresponding to the second angle from the reference line to the second detection element, the first count, and the second count in the plane including the first and second detection elements in the two-dimensional direction. The count is an ideal output corresponding to the case where the surface first reached by the radiation in the first detection element is counted as the incident position.

13. An output determination method, wherein, The following steps are required: Collects a first output relating to a first detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction, and a second output relating to a second detection element surrounding the first detection element; and Based on the first weight corresponding to the first angle from the baseline to the first detection element, the second weight corresponding to the second angle from the baseline to the second detection element, the first output, and the second output in the plane including the first and second detection elements in the two-dimensional direction, the output corresponding to the reconstructed position of the first detection element is determined. The determined output is the ideal output corresponding to the case where the radiation is detected at the surface that is first reached by the first detection element as the incident position.

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