CN116763330A

CN116763330A - Radiation diagnosis device, radiation detector, and output determination method

Info

Publication number: CN116763330A
Application number: CN202310245310.9A
Authority: CN
Inventors: 石田祥大
Original assignee: Canon Medical Systems Corp
Current assignee: Canon Medical Systems Corp
Priority date: 2022-03-15
Filing date: 2023-03-14
Publication date: 2023-09-19

Abstract

The radiation diagnostic apparatus of the related embodiment has a plurality of radiation detection elements and a processing circuit. The plurality of radiation detection elements are arranged in two dimensions. The processing circuit determines an ideal output for the 1 st detection element when a surface on which radiation first reaches the 1 st detection element is set as an incident position of the radiation, based on the 1 st output for the 1 st detection element and the 2 nd output for the 2 nd detection element included in the plurality of radiation detection elements.

Description

Radiation diagnosis device, radiation detector, and output determination method

Technical Field

The invention relates to a radiation diagnosis device, a radiation detector and an output determination method.

Background

Conventionally, in an X-ray computed tomography (Computed Tomography:ct) apparatus, a technique is known in which detection modules each having an X-ray conversion element arranged in a planar manner are arranged in a circular arc shape in a fan-shaped angular direction, thereby constructing an arc-shaped X-ray detector. Since such an arc-shaped X-ray detector is flat in the cone angle direction, the larger the cone angle is, the larger the incident angle of the X-ray to the X-ray conversion element is.

In general, as a reconstruction theory of the detected X-rays, it can be considered that the X-rays are incident at the position of the incident X-ray conversion element surface. However, in the case where the X-ray is inclined with respect to the surface of the X-ray conversion element, it is a probability event that the X-ray is absorbed in the deep direction of the X-ray conversion element, and therefore the X-ray is not limited to the incident X-ray conversion element, and may be absorbed by another adjacent X-ray conversion element. As a result, the spatial resolution in the cone angle direction of the X-ray detector may be reduced, for example, the image may be elongated in the body axis direction of the subject, which may cause a reduction in the image quality of the X-ray image data.

Therefore, there is a technology of miniaturizing a detector module composed of a plurality of X-ray conversion elements, and directing the X-ray conversion element surface in the X-ray incidence direction in units of each small module. However, in such a structure, there are cases where the image quality is deteriorated due to the occurrence of scattered rays or the like caused by the structure of the small module.

Further, an X-ray conversion element used as a direct conversion type X-ray detector for directly converting X-rays into electric charges using a semiconductor, an inert gas, or the like has a smaller absorption cross-sectional area of X-rays than an indirect conversion type detector. The thickness of the direct conversion type X-ray detector is generally thicker than that of the X-ray conversion element used in the indirect conversion type X-ray detector by the semiconductor crystal functioning as the photoelectric conversion element. Because of this, the penetration distance of the X-ray that is obliquely incident into the X-ray conversion element of the direct conversion type X-ray detector is longer, and in the direct conversion type X-ray detector, the influence due to the oblique incident of the X-ray is more likely to occur.

In an X-ray flat panel detector (flat panel detector: flat Panel Detector (FPD)) that is generally used in X-ray photography, all X-ray conversion elements are coordinated on a large-area surface. Therefore, the channel direction (fan angle direction) is affected by the oblique incidence of the X-rays, not only in the column direction (cone angle direction), but also in some cases, the image quality of the X-ray image data may be deteriorated. Further, since the penetration force of an X-ray photon differs depending on the energy of the X-ray photon, for example, in the photon counting detector (Photon Counting Detector), the degree of influence of the oblique incidence of the X-ray differs depending on the energy domain of the X-ray. As a result, the position of the X-ray conversion element projected by the energy bin (energy bin) is shifted, and thus the image quality of the X-ray image data may be degraded.

Disclosure of Invention

A first aspect relates to a radiation diagnosis apparatus, comprising: a plurality of radiation detection elements arranged in a two-dimensional direction; and a processing circuit configured to determine an output corresponding to a reconstruction position of the 1 st detection element based on a 1 st output of the 1 st detection elements included in the plurality of radiation detection elements and a 2 nd output of the 2 nd detection element.

A second aspect 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 1 st count number based on outputs from a 1 st detection element included in the plurality of radiation detection elements, and collects a 2 nd count number based on outputs from a 2 nd detection element around the 1 st detection element; and a processing circuit configured to determine a count number corresponding to a reconstructed position of the 1 st detection element based on the 1 st count number and the 2 nd count number.

A third aspect relates to an output determination method, including: collecting 1 st output concerning a 1 st detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction and 2 nd output concerning a 2 nd detection element around the 1 st detection element; based on the 1 st output and the 2 nd output, an output corresponding to the reconstruction position of the 1 st detection element is determined.

Drawings

Fig. 1 is a diagram showing an example of the structure of a PCCT apparatus 1 according to embodiment 1.

Fig. 2 is a view showing a part of the X-ray detector on the side of the end portion of the opening with respect to the mid-plane (midplane) in embodiment 1 together with the X-rays obliquely entering the X-ray detector.

Fig. 3 is a flowchart showing an example of the procedure of the output determination processing according to embodiment 1.

Fig. 4 is a diagram showing a part of the X-ray detector on the side of the end portion of the midplane which is open with respect to the modification of embodiment 1, together with the X-rays which are obliquely incident on the X-ray detector.

Fig. 5 is a diagram showing an example of the structure of an X-ray detector corresponding to the radiation detector according to embodiment 2.

Detailed Description

The radiation diagnostic apparatus of the related embodiment has a plurality of radiation detection elements and a processing circuit. The plurality of radiation detection elements are arranged in two dimensions. The processing circuit determines an output corresponding to a reconstruction position of the 1 st detection element based on a 1 st output of the 1 st detection elements included in the plurality of radiation detection elements and a 2 nd output of the 2 nd detection elements around the 1 st detection element.

Hereinafter, an embodiment of a radiation diagnosis apparatus and a radiation detector will be described with reference to the drawings. In the following embodiments, the same operations are assumed to be performed in the same parts with the same reference numerals, and overlapping descriptions are appropriately omitted. The radiation diagnosis apparatus and the radiation detector according to the present application are not limited to the embodiments described below. In addition, for the sake of materialization of the description, it is assumed that the radiation of the related embodiment is X-rays. The radiation according to the embodiment is not limited to X-rays, and may be other radiation (electromagnetic waves corresponding to charged particles and various wavelengths) or the like.

The radiation detector of the related embodiment has a plurality of radiation detecting elements arranged in two-dimensional directions. The two-dimensional direction is, for example, a cone angle direction and a fan angle direction. The taper angle direction and the fan angle direction will be described later. In the following, for the sake of explanation, an X-ray detector of photon counting system (hereinafter referred to as photon counting X-ray detector) will be assumed. The photon counting type X-ray detector includes, for example, a direct conversion type X-ray detector including a semiconductor element for directly converting incident X-rays into an electrical signal. In addition, the photon counting type X-ray detector may have an indirect conversion type X-ray detector instead of the direct conversion type X-ray detector.

The radiation detector according to the embodiment is not limited to the photon counting type X-ray detector, and may be an integrated type (also referred to as a current mode measurement system or an energy integration type) X-ray detector. In this case, the integrated X-ray detector has a direct conversion type or an indirect conversion type. For example, the radiation detector may have an X-ray plane detector (flat panel detector: flat Panel Detector (FPD)) which is generally used in X-ray radiography as an integrated type X-ray detector.

The radiation diagnosis apparatus according to the embodiment is assumed to be an X-ray computed tomography (Computed Tomography:ct) apparatus for the sake of concrete description. More specifically, the radiation diagnosis apparatus according to the embodiment will be described assuming that it is a Photon Counting (PCCT) apparatus (hereinafter referred to as PCCT apparatus) capable of performing Photon Counting CT. The PCCT apparatus is an apparatus that can reconstruct X-ray CT image data with a high SN ratio by counting X-rays transmitted through a subject using a direct conversion type X-ray detector, for example. The radiation diagnosis apparatus according to the embodiment may be an X-ray CT apparatus having an integrated X-ray detector instead of the photon counting type X-ray detector. The radiation diagnosis device may be an X-ray diagnosis device having an FPD (for example, a general imaging X-ray diagnosis device, a circulator X-ray diagnosis device (Angiography device), or the like).

(embodiment 1)

Fig. 1 is a diagram showing an example of the structure of a PCCT apparatus 1 according to embodiment 1. The PCCT apparatus 1 may be referred to as a radiographic diagnostic apparatus. As shown in fig. 1, the PCCT apparatus 1 includes a gantry apparatus 10, a bed apparatus 30, and a console apparatus 40. In the present embodiment, the rotation axis of the rotation frame 13 in the non-tilted state and the longitudinal direction of the top plate 33 of the table device 30 are defined as the Z-axis direction, the axial direction perpendicular to the Z-axis direction and horizontal to the floor surface is defined as the X-axis direction, and the axial direction perpendicular to the Z-axis direction and vertical to the floor surface is defined as the Y-axis direction. In fig. 1, for convenience of explanation, a plurality of gantry apparatuses 10 are depicted, but the gantry apparatus 10 is one as a structure of an actual PCCT apparatus 1.

The gantry apparatus 10 and the bed apparatus 30 operate based on an operation from a user via the console apparatus 40 or based on an operation from a user via an operation unit provided in the gantry apparatus 10 or the bed apparatus 30. The gantry apparatus 10, the bed apparatus 30, and the console apparatus 40 can be connected in communication with each other by wire or wirelessly.

The gantry apparatus 10 is an apparatus having a photographing system for irradiating the subject P with X-rays 100 and collecting detection data of the X-rays 100 transmitted through the subject P. More specifically, the gantry apparatus 10 has an X-ray tube 11 (X-ray generating section), a wedge section 16, a collimator 17, an X-ray detector 12, X-ray high voltage devices 14, DAS (Data Acquisition System), a rotating frame 13, and a control device 15.

The X-ray tube 11 is a vacuum tube that generates X-rays 100 by radiating hot electrons from a cathode (filament) toward an anode (target) by application of a high voltage from an X-ray high voltage device 14 and supply of a filament current. X-rays 100 are generated by hot electrons impinging on the target. The X-rays 100 generated at the spherical focal point of the X-ray tube 11 are formed into a cone beam shape, for example, via the collimator 17, and are irradiated to the subject P. For example, the X-ray tube 11 includes a rotating anode type X-ray tube that generates X-rays by radiating hot electrons to a rotating anode.

As shown in fig. 1, the X-ray 100 irradiated in a cone beam shape has a fan-like (fan-like) spread shape in the X-axis direction. Therefore, an angle indicating the expansion of the X-axis direction of the X-ray 100 irradiated in a cone beam shape is referred to as a fan angle. The angle indicating the depth of the X-ray 100 irradiated in the cone beam shape in the Z-axis direction is referred to as a cone angle. Therefore, the X-axis direction is also referred to as a fan angle direction, and the Z-axis direction is referred to as a 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 X-rays irradiated from the X-ray tube 11 and passing through the subject P in photon units, and outputs an electrical signal corresponding to the X-ray dose to the DAS 18. The X-ray detector 12 has, for example, a plurality of detection element rows in which a plurality of detection elements (also referred to as X-ray detection elements) are arranged in a fan-shaped angular direction (also referred to as a channel direction) along 1 circular arc around the focal point of the X-ray tube 11. In the X-ray detector 12, a plurality of detection element rows are arranged flat along the Z-axis direction. That is, the X-ray detector 12 has a structure in which a plurality of the detection element rows are arranged flat along the taper angle direction (also referred to as the row direction, and the slice direction), for example. The plurality of detection elements of the X-ray detector 12 correspond to the plurality of radiation detection elements of the radiation detector.

The PCCT apparatus 1 includes various types such as a rotation/rotation-Type (3 rd generation CT) in which the X-ray tube 11 and the X-ray detector 12 Rotate around the subject P as a unit, and a Stationary/rotation-Type (4 th generation CT) in which a plurality of detection elements arranged in a ring-shaped array are fixed and only the X-ray tube 11 rotates around the subject P, and can be applied to the present embodiment.

The X-ray detector 12 is a direct conversion type X-ray detector having a semiconductor element for converting incident X-rays into electric charges. The X-ray detector 12 of the present embodiment includes, for example, at least 1 high-voltage electrode, at least 1 semiconductor crystal, and a plurality of readout electrodes. The semiconductor element is also called an X-ray conversion element. Semiconductor crystallization is realized by CdTe (cadmium telluride: cadmium telluride) or CdZnTe (cadmium zinc telluride: cadmium Zinc telluride: CZT) or the like, for example. In the X-ray detector 12, electrodes are provided on two surfaces facing each other across the semiconductor crystal 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 is referred to as a cathode surface.

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

The rotation 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 so as to face each other. The rotary frame 13 is a circular frame that rotates the X-ray tube 11 and the X-ray detector 12 by a control device 15 described later. The rotary frame 13 is rotatably supported by a fixed frame formed of metal such as aluminum. The rotating frame 13 receives power from a driving mechanism of the control device 15 and rotates around a rotation axis at a constant angular velocity.

The rotating frame 13 supports the X-ray high voltage device 14 and the DAS18 in addition to the X-ray tube 11 and the X-ray detector 12. Such a rotary frame 13 is accommodated in a substantially cylindrical housing formed with an opening (bore) as a photographing space. The central axis of the opening coincides with the rotation axis of the rotation frame 13.

The X-ray high voltage device 14 includes: a high voltage generator having a circuit such as a transformer (inverter) and a rectifier, and having a 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; and an X-ray control device for controlling an output voltage corresponding to the X-rays irradiated from the X-ray tube 11. The high voltage generating device may be of a transformer type or an inverter type. The X-ray high voltage device 14 may be provided on the rotating frame 13 or on the fixed frame (not shown) side of the gantry apparatus 10. The fixed frame is a frame that rotatably supports the rotary frame 13.

The control device 15 includes a processing circuit such as CPU (Central Processing Unit), and a driving mechanism such as a motor and an actuator. The processing circuit includes a processor such as a CPU and an MPU (Micro Processing Unit) and memories such as ROM (Read Only Memory) and RAM (Random Access Memory) as hardware resources. The control device 15 may be implemented by a processor such as GPU (Graphics Processing Unit), an application specific integrated circuit (Application Specific Integrated Circuit: ASIC), a programmable logic device (e.g., a simple programmable logic device (Simple Programmable Logic Device: SPLD), a complex programmable logic device (Complex Programmable Logic Device: CPLD), or a field programmable gate array (Field Programmable Gate Array: FPGA)), or the like.

In the case where the processor is, for example, a CPU, the processor realizes functions by reading out and executing a program stored in the memory. On the other hand, in the case where the processor is an ASIC, instead of saving the program in the memory, the function is directly incorporated as a logic circuit into the circuit of the processor. The processors of the present embodiment are not limited to the case where the processors are configured as a single circuit, and a plurality of independent circuits may be combined to form 1 processor, thereby realizing the functions. Further, a plurality of components may be combined with 1 processor to realize the functions.

The control device 15 has a function of receiving an input signal from an input interface 43 attached to the console device 40 or the gantry device 10 and performing operation control of the gantry device 10 and the bed device 30. For example, the control device 15 performs control of rotating the rotating frame 13, tilting the gantry 10, and operating the couch device 30 and the top 33 in response to an input signal. The control of tilting the gantry apparatus 10 may be realized by the control device 15 rotating the rotating frame 13 about an axis parallel to the X-axis direction based on tilt angle (tilt angle) information input from the input interface 43 mounted on the gantry apparatus 10. The control device 15 may be provided in the stand device 10 or in the console device 40.

The wedge 16 is a filter for adjusting the X-ray dose of the X-ray 100 irradiated from the X-ray tube 11. Specifically, the wedge portion 16 is a filter that transmits and attenuates the X-rays 100 irradiated from the X-ray tube 11 so that the X-rays 100 irradiated from the X-ray tube 11 to the subject P have a predetermined distribution. The wedge 16 is, for example, a wedge filter (wedge filter) or a bow tie filter (bow-tie filter), and is formed by processing aluminum so as to have a predetermined target angle and a predetermined thickness.

The collimator 17 is a lead plate or the like for narrowing the X-ray 100 transmitted through the wedge 16 to the X-ray irradiation range, and a slit is formed by a combination of a plurality of lead plates or the like.

DAS (Data Acquisition System) 18 has a plurality of counting circuits. The plurality of counting circuits each include an amplifier for amplifying the electric signal output from each detection element of the X-ray detector 12 and an a/D converter for converting the amplified electric signal into a digital signal, and generate detection data, which is a result of the counting process using the detection signal of the X-ray detector 12. The result of the counting process is data of the photon number of the X-ray assigned to each Energy Bin (Energy Bin). The energy bin corresponds to an energy domain of a predetermined width. For example, the DAS18 counts photons (X-ray photons) from the X-rays irradiated from the X-ray tube 11 and transmitted through the subject P, and generates, as detection data, a result of a counting process for discriminating the energy of the counted photons. The DAS18 is an example of a data collection unit.

The detection data generated by the DAS18 is transferred to the console device 40. The detection data is a set of data that generates a channel number, a column number, a view angle number indicating a collected view angle (also referred to as a projection angle) and a value indicating a dose of the detected X-rays of the detector pixel of the source. As the view angle number, a sequence in which the views are collected (collection time) may be used, or a number (for example, 1 to 1000) indicating the rotation angle of the X-ray tube 11 may be used. Each of the plurality of counter circuits in the DAS18 is implemented by, for example, a circuit group including circuit elements capable of generating detection data. In the present embodiment, the term "detection data" includes both the raw data before the preprocessing and the raw data after the preprocessing are detected and performed by the X-ray detector 12. In addition, the data before preprocessing (detection data) and the data after preprocessing may be collectively referred to as projection data.

The couch device 30 is a device for placing and moving a subject P to be scanned, and includes a base 31, a couch driving device 32, a table 33, and a table support frame 34. The base 31 is a housing 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 33 on which the subject P is placed in the longitudinal direction of the top 33. The couch driving device 32 moves the top 33 in accordance with the control by the console device 40 or the control by 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, the table driving device 32 may move the table support frame 34 in the longitudinal direction of the table 33 in addition to the table 33.

The console device 40 is a device that performs control of the gantry device 10, generation of CT image data based on a scanning result of the gantry device 10, and the like. The console device 40 has a memory 41 (storage section), a display 42 (display section), an input interface 43 (input section), and a processing circuit 44 (processing section). Data communication between the memory 41, the display 42, the input interface 43 and the processing circuit 44 takes place via a BUS (BUS).

The memory 41 is implemented by, for example, a semiconductor memory element such as RAM (Random Access Memory) or flash memory, HDD (Hard disk Drive) or SSD (Solid State Drive), an optical disk, or the like. The memory 41 may be a drive device that reads and writes various information from and to a removable storage medium such as CD (Compact Disc), DVD (Digital Versatile Disc), or flash memory, or a semiconductor memory element such as RAM (Random Access Memory). The memory 41 stores projection data and reconstructed image data, for example. The storage area of the memory 41 may be located in the PCCT apparatus 1 or in an external storage device connected via a network. The memory 41 stores a control program according to the present embodiment. The memory 41 is an example of a storage unit.

The display 42 displays various information. For example, the display 42 outputs a medical image (CT image) generated by the processing circuit 44, GUI (Graphical User Interface) for receiving various operations from an operator, and the like. For example, as the display 42, a liquid crystal display (LCD: liquid Crystal Display), an organic EL display (OELD: organic Electro Luminescence Display), a plasma display, or any other display may be suitably used. The display 42 may be provided in the stand device 10. The display 42 may be a desktop type or may be constituted by a tablet terminal or the like capable of wirelessly communicating with the main body of the console device 40.

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 an operator, a collection condition at the time of collecting projection data, a reconstruction condition at the time of reconstructing a CT image, an image processing condition at the time of generating a post-processing image from the CT image, and the like. As the input interface 43, for example, a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touch pad, a touch panel display, and the like can be suitably used.

In the present embodiment, the input interface 43 is not limited to a configuration including physical operation members such as a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touch pad, and a touch panel display. For example, a processing circuit that receives an electric signal corresponding to an input operation from an external input device provided separately from the apparatus and outputs the electric signal to the processing circuit 44 is also included in the example of the input interface 43. The input interface 43 is an example of an input unit. The input interface 43 may be provided in the stand device 10. The input interface 43 may be constituted by a tablet terminal or the like capable of wireless communication with the main body of the console device 40.

The processing circuit 44 controls the operation of the entire PCCT apparatus 1 based on the input operation electric 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 respective processing functions executed by the system control function 441, the preprocessing function 442, the reconstruction processing function 443, the scan control function 444, the image processing function 445, the display control function 446, and the determination function 447, which are constituent elements of the processing circuit 44 shown in fig. 1, are recorded in the memory 41 in the form of programs executable by a computer.

The processing circuit 44 is, for example, a processor, and reads out and executes each program from the memory 41, thereby realizing a function corresponding to each read-out program. In other words, the processing circuit 44 in a state in which the respective programs are read out has respective functions shown in the processing circuit 44 in fig. 1. The processing circuit 44 implementing the system control function 441 is an example of a control unit. The processing circuit 44 implementing the preprocessing function 442 is an example of a preprocessing section. The processing circuit 44 that realizes the reconstruction processing function 443 is an example of a reconstruction processing unit. The processing circuit 44 that realizes the scan control function 444 is an example of a scan control unit. The processing circuit 44 that realizes the image processing function 445 is an example of an image processing section. The processing circuit 44 implementing the display control function 446 is an example of a display control section. The processing circuit 44 implementing the decision function 447 is an example of a decision unit. The processing circuit 44 may be used as an example of the control unit.

In fig. 1, the system control function 441, the preprocessing function 442, the reconstruction processing function 443, the scan control function 444, and the display control function 446 are implemented by a single processing circuit 44, but the present embodiment is not limited to this. For example, the processing circuit 44 may be configured by combining a plurality of independent processors, and each processing function may be realized by each processor executing each program. The processing functions of the processing circuit 44 may be implemented by being appropriately distributed or combined in a single or a plurality of processing circuits.

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

The processing circuit 44 generates, by the preprocessing function 442, preprocessed data obtained by performing logarithmic conversion processing, offset correction processing, inter-channel sensitivity correction processing, harness hardening correction, and the like on the ideal detection data determined by the determination function 447. The ideal detection data will be described later.

The processing circuit 44 performs reconstruction processing using a filter correction back projection method, a successive approximation reconstruction method, or the like on the projection data generated by the preprocessing function 442 by the reconstruction processing function 443, and generates CT image data.

The processing circuit 44 obtains two-dimensional positioning image data of the subject P for determining a scanning range, a scanning condition, and the like by the scanning control function 444. In addition, the positioning image data may be referred to as scan image data or scout (scout) image data.

The processing circuit 44 converts CT image data generated by the reconstruction processing function 443 based on an input operation received from an operator via the input interface 43 into tomographic image data or three-dimensional image data of an arbitrary cross section by a known method by the image processing function 445. The three-dimensional image data may be generated directly by the reconstruction processing function 443.

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

The processing circuit 44 determines an output corresponding to the reconstruction position of the 1 st detection element based on the 1 st output of the 1 st detection element included in the plurality of radiation detection elements (the plurality of detection elements of the X-ray detector 12) and the 2 nd output of the 2 nd detection elements around the 1 st detection element by the determination function 337. The reconstructed position is used for calculation of the reconstruction based on the determined output, and represents the position of the representative point of the 1 st detection element, for example. The reconstruction position is, for example, a surface (cathode surface) on which the X-rays reach in the 1 st detection element. The reconstruction position is not limited to the cathode surface of the 1 st detection element. For example, the anode electrode of the 1 st detection element may be located at any position inside the semiconductor crystal. In the following, for the sake of explanation, it is assumed that the reconstruction position is the incidence position of the X-ray on the cathode surface with respect to the 1 st detection element.

The processing circuit 44 determines, by the determination function 337, an ideal output concerning the 1 st detection element when the surface (cathode surface) on which the X-ray reaches is the X-ray incidence position in the 1 st detection element, based on the 1 st output concerning the 1 st detection element included in the plurality of detection elements of the X-ray detector 12 and the 2 nd output concerning the 2 nd detection elements around the 1 st detection element. The position of incidence of the X-rays is, for example, the surface of the X-ray detector 12 where the X-ray path (also called line) to the 1 st detection element first hits. In other words, the incident position of the X-ray corresponds to the position: for example, the X-ray path after passing through the subject P or the position where the direct line path not passing through the subject P hits the cathode surface is not a scattered ray of the X-ray.

The 2 nd detection element is not limited to at least one detection element adjacent to the 1 st detection element, and may be a plurality of detection elements surrounding the 1 st detection element. The 1 st output corresponds to the detection data (raw data or count number) related to the 1 st detection element, and the 2 nd output corresponds to the detection data (raw data or count number) related to the 2 nd detection element. In the case where the radiation diagnosis apparatus is an X-ray diagnosis apparatus or an integrated X-ray CT apparatus, for example, the 1 st output corresponds to the plain raw data output from the 1 st detection element, and the 2 nd output corresponds to the plain raw data output from the 2 nd detection element.

The ideal output corresponds to, for example, an output (for example, a count number or a current value) of the 1 st electrode when electrons generated by the X-ray are read out by the 1 st electrode when the X-ray is obliquely incident on a cathode surface (hereinafter, referred to as an opposing surface) opposing the readout electrode (hereinafter, referred to as the 1 st electrode) of the 1 st detection element. For example, the facing surface corresponds to a surface directly above the 1 st electrode along the Y-axis direction. The 2 nd detection element is preset according to the incidence angle of the line (ray) of the X-ray obliquely entering the facing surface. In the PCCT apparatus 1, the 1 st output, the 2 nd output, and the output (for example, may also be referred to as ideal output) corresponding to the reconstruction position of the 1 st detection element are count numbers obtained by counting photons in X-rays. At this time, the ideal output corresponds to an output count in the case where the surface of the X-ray detector 12, which is first touched by the X-ray path leading to the 1 st detection element, is counted as the incident position of the X-ray.

Specifically, the processing circuit 44 determines, by the determination function 447, an output (ideal output concerning the 1 st detection element) corresponding to the reconstruction position of the 1 st detection element using the 1 st weight corresponding to the 1 st angle from the reference line to the 1 st detection element and the 2 nd weight corresponding to the 2 nd angle from the reference line to the 2 nd detection element in the direction (for example, the column direction) in the plane including the 1 st detection element and the 2 nd detection element, out of the two-dimensional directions (the channel direction and the column direction) in which the plurality of detection elements are arrayed. That is, the determination function 447 performs a weighted calculation by using the outputs of the detection elements around each of the plurality of detection elements of the X-ray detector 12, thereby statistically calculating the output that each of the detection elements originally desires as the output, that is, the most likely ideal output.

The reference line is, for example, a line connecting the center (middle plane) of the cone angle direction of the X-ray detector 12 with the focal point of the tube sphere. The 1 st weight and the 2 nd weight are set based on a material for converting X-rays (radiation) into electrons or visible light in the 1 st detection element and the 2 nd detection element, a thickness of the material, and an angle at which the X-rays are incident on the 1 st detection element. For example, in the case of a direct conversion type X-ray detector, the material is a semiconductor crystal. In the case of an indirect conversion type X-ray detector, the material is, for example, a scintillator. The angle at which the X-ray is incident on the 1 st detection element corresponds to the 1 st angle. The 1 st and 2 nd weights are set in advance by various simulations (for example, monte carlo simulation) using the 1 st angle, the thickness and the material of the semiconductor crystal, or a correction test (experiment) in advance, for example.

In the case where the direction in the plane including the 1 st detection element and the 2 nd detection element is, for example, the taper angle direction (column direction), that is, in the case where the 1 st detection element and the 2 nd detection element are aligned along the taper angle direction, the angle from the reference line to the 1 st detection element corresponds to the angle between the straight line connecting the 1 st detection element and the focal point of the tube ball and the reference line (hereinafter, referred to as 1 st taper angle). In the case where the direction in the plane including the 1 st detection element and the 2 nd detection element is, for example, the taper angle direction (column direction), the angle from the reference line to the 2 nd detection element (hereinafter referred to as the 2 nd taper angle) corresponds to the angle between the reference line and the straight line connecting the 2 nd detection element and the focal point of the pipe ball.

That is, when the 1 st detection element and the 2 nd detection element are arranged along the taper angle direction, the processing circuit 44 uses the 1 st weight corresponding to the 1 st taper angle from the reference line to the 1 st detection element and the 2 nd weight corresponding to the 2 nd taper angle from the reference line to the 2 nd detection element by the determination function 447, and adds, for example, the 1 st multiplication value obtained by multiplying the 1 st output by the 1 st weight and the 2 nd multiplication value obtained by multiplying the 2 nd output by the 2 nd weight to determine the output corresponding to the reconstruction position of the 1 st detection element (ideal output concerning the 1 st detection element).

Fig. 2 is a diagram showing a part of the X-ray detector 12 on the side of the end portion opening from the middle plane together with the X-rays obliquely entering the X-ray detector 12. More specifically, fig. 2 shows a part of the X-ray detector 12 that is close to the end of the opening on the +side in the Z-axis direction, that is, the end of the opening that is closer to the end of the top 131 on the +side in the Z-axis direction (the foot of the subject P) shown in fig. 1, together with the X-rays that are obliquely incident on the X-ray detector 12.

In FIG. 2, it is assumed that the 1 st detection element is the readout electrode C _N . In addition, in fig. 2, a part N of the X-rays generated in the X-ray tube 11 _seg Is shown in contact with the sense electrode C corresponding to the 1 st detection element _N X-rays (hereinafter referred to as oblique X-rays) obliquely entering at the opposing cathode surface (opposing surface). In FIG. 2, the electrode C is read out from _N Output 1 st output is relative to the output from the plurality of sense electrodes (sense electrode C) _N Reading electrode C _N+1 Reading electrode C _N+2 ) The ratio of the total output of (2) is represented by 70%. In other words, 70% is shown at the sense electrode C _N In the semiconductor crystal surrounded by the dotted line of the region directly above (1), a part of N of X-rays _seg Is converted into a ratio of electric charges.

In addition, in FIG. 2, the electrode C will be read out from _N+1 Output 2 nd output relative to the output from the plurality of sense electrodes (sense electrode C) caused by oblique X-rays _N Reading electrode C _N+1 Reading electrodeC _N+2 ) The ratio of the total output of (2) is represented by 29%. In other words, 29% is shown at the sense electrode C _N+1 In the semiconductor crystal surrounded by the dotted line of the region directly above (1), a part of N of X-rays _seg Is converted into a ratio of electric charges.

In addition, in FIG. 2, the electrode C will be read out from _N+2 Output 2 nd output relative to the output from the plurality of sense electrodes (sense electrode C) caused by oblique X-rays _N Reading electrode C _N+1 Reading electrode C _N+2 ) The ratio of the total output of (2) is represented by 1%. In other words, 1% is expressed in the sense electrode C _N+2 In the semiconductor crystal surrounded by the dotted line of the region directly above (1), a part of N of X-rays _seg Is converted into a ratio of electric charges. In the example shown in FIG. 2, the 2 nd detection element and the readout electrode C _N+1 Reading electrode C _N+2 Is a function of the two corresponding pairs of the two.

That is, when the geometry of the detection element and the oblique incidence of the X-rays as shown in fig. 2 are assumed, a part of the N-rays is taken into consideration _seg From the sense electrode C _N 70% of the output from the sense electrode C _N+1 29% of the output from the sense electrode C _N+2 1% of the output of (2) contributes to the ideal output C of the 1 st output _iN . Specifically, in the example shown in fig. 2, the first detection element (the readout electrode C _N ) Related ideal output C _iN Calculated by the following formula (1).

C _iN ＝k _N,N ×C _N +k _N，N+1 ×C _N+1 +k _N，N+2 ×C _N+2 …(1)

On the right side of formula (1), C _N Indicating the reading electrode C as the 1 st detection element _N The relevant output (1 st output). Further, to the right of formula (1), C _N+1 C (C) _N+2 Representing the detection element (readout electrode C) corresponding to the 2 nd detection element _N+1 Reading electrode C _N+2 ) The 2 nd output concerned. Further, on the right side of formula (1), k _N，N Represents the 1 st weight, k _N，N+1 K _N，N+2 Representing the 2 nd weight. As shown in FIG. 2, the 1 st weight k _N，N Is 0.7, thWeight k of 2 _N，N+1 ，k _N，N+2 0.29 and 0.01, respectively. Therefore, the processing circuit 44 determines the detection element 1 (the readout electrode C) by the determination function 447 using the following equation (2) _N ) Related ideal output C _iN 。

C _iN ＝0.7×C _N +0.29×C _N+1 +0.1×C _N+2 …(2)

The values (0.7,0.29, 0.01) of the 1 st weight and the 2 nd weight in fig. 2 and expression (2) are examples, and vary depending on the incident angle of the X-ray to the 1 st detection element, i.e., the column number. In general, when the total number of detection elements in the column direction is n and numbers are given from 1 to n in the taper angle direction (Z-axis direction), the expression (1) is generally represented by the following expression (3).

Vector on left in the above formula (3)

An ideal output vector having a plurality of ideal outputs corresponding to the plurality of detection elements, respectively, as components is represented. In addition, the right vector in the above formula (3)

An actual measurement output vector having a plurality of outputs (actual measurement values) corresponding to the plurality of detection elements, respectively, as components of the vector is shown.

In addition, the matrix on the right side in the above formula (3) (hereinafter referred to as weight matrix)

The plurality of weights associated with the plurality of detection elements are represented as a matrix. In other words, the weight matrix corresponds to an actual measurement output vector that will represent an actual measurement value of the output related to the X-ray detector 12

And an ideal output vector representing an ideal output associated with the X-ray detector 12

The correlation coefficient of each component (output associated with each of the plurality of detection elements) is used as a coefficient matrix (e.g., correlation matrix) of the weights. In the case where the total number n of detection elements along the column direction is an odd number, the element number n/2+1 corresponds to a midplane. At this time, weight k _n/2+1，i (1.ltoreq.i.ltoreq.n: all zeros except n/2+1), weight k _{n/2+1，n/2+1} 1. In addition, the coefficient matrix is desirably a matrix having components symmetrical with respect to a diagonal line connecting 1 row and N columns and N rows and 1 columns.

In the weight matrix, qualitatively, the larger the taper angle of a detection element, the larger the weight of an adjacent element (and a plurality of detection elements including the adjacent element and extending in the larger direction) in the direction in which the taper angle is larger than the detection element, the smaller the weight of the detection element itself. For example, in the diagonal component of the weight matrix, the 1 st weight is increased or decreased from the weight k corresponding to the midplane as the number of rows and columns increases or decreases _n/2，n/2 The onset becomes smaller. In addition, for example, in the off-diagonal component of the weight matrix, as the number of rows and columns increases and decreases, the 2 nd weight of the 2 nd detection element along the direction in which the taper angle is large is determined from the weight k corresponding to the midplane _n/2，n/2 And increases. In other words, in the weight matrix, in each of the plurality of detection elements, as the 1 st angle becomes larger, the 1 st weight decreases and the 2 nd weight increases. The various simulations (e.g. monte carlo simulation) or weight matrices generated by prior correction experiments (experiments) are stored in a memory 41.

In the example shown in fig. 2 and the above-described expression, only the taper angle direction is focused, but the fan angle direction may be focused instead of the taper angle direction. In the case where an FPD is used as the X-ray detector 12, that is, in the case where the incidence angle of the X-rays is increased in a channel having a large fan angle, the dimensions of the matrix operation of the above-described expression may be extended. In this case, the actual measurement output vector and the ideal output vector are, for example, matrices representing outputs of a plurality of detection elements with respect to the taper angle direction and the fan angle direction, and the weight matrix is a tensor of 4 times having the taper angle direction and the fan angle direction as independent variables (tail marks).

The above-described processing by the decision function 447 can also be implemented by the preprocessing function 442. At this time, the preprocessing function 442 executes processing content based on the decision function 447 on data (for example, the count number) before preprocessing before execution of preprocessing. The above processing performed by the decision function 447 can also be performed by the DAS 18. At this time, DAS18 performs processing based on decision function 447 on detected data (e.g., raw data or raw data (count)).

The processing circuit 44 outputs the ideal output determined by the determination function 447 with respect to each of the plurality of detection elements to the preprocessing function 442. The ideal output determined by the determination function 447 corresponds to correction of the effect of the oblique incidence of the X-rays with respect to the X-ray detector 12. That is, the ideal output corresponds to correction data in which the influence of the oblique incidence of the 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 correction projection data). The corrected projection data corresponds to projection data in which the influence of the oblique incidence of the X-rays with respect to 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 a reconstruction process for 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 by the reconstruction processing function 443, and generates a reconstructed image (corrected reconstructed image). The corrected reconstructed image is stored in, for example, the memory 41, and is displayed on the display 42 through the display control function 446. The corrected reconstructed image corresponds to a reconstructed image in which the influence of the oblique incidence of the X-rays on the X-ray detector 12 is corrected.

The overall configuration of the PCCT apparatus 1, which is an example of the radiation diagnosis apparatus, is described above. The order of the output determination processing will be described below with reference to fig. 3. The output determination process determines an output corresponding to the reconstructed position of the 1 st detection element based on the 1 st output and the 2 nd output collected. Fig. 3 is a flowchart showing an example of the procedure of the output determination process.

(output determination processing)

(step S301)

The data collection circuit 18 collects, by scanning the subject P, the 1 st output concerning the 1 st detection element included in the plurality of radiation detection elements arrayed in the two-dimensional direction and the 2 nd output concerning the 2 nd detection elements around the 1 st detection element. Thus, the 1 st output and the 2 nd output are obtained.

(step S302)

The processing circuit 44 determines an output corresponding to the reconstruction position of the 1 st detection element based on the 1 st output and the 2 nd output by the determination function 447. The determination of the output corresponding to the reconstruction position is based on the above description, and therefore, the description thereof is omitted.

The radiation diagnosis apparatus according to embodiment 1 described above determines an output corresponding to the reconstruction position of the 1 st detection element (for example, an ideal output relating to the 1 st detection element) based on the 1 st output relating to the 1 st detection element included in the plurality of radiation detection elements arranged in the two-dimensional direction and the 2 nd output relating to the 2 nd detection elements around the 1 st detection element. For example, the radiation diagnostic apparatus according to the present embodiment determines an output (for example, an ideal output) corresponding to a reconstruction position using a 1 st weight corresponding to a 1 st angle from a reference line to the 1 st detection element and a 2 nd weight corresponding to a 2 nd angle from the reference line to the 2 nd detection element in a direction in a plane including the 1 st detection element and the 2 nd detection element in a two-dimensional direction. Specifically, the radiation diagnostic apparatus according to the present embodiment determines an output (for example, an ideal output) corresponding to the reconstruction position by adding a 1 st multiplication value obtained by multiplying a 1 st output by a 1 st weight to a 2 nd multiplication value obtained by multiplying a 2 nd output by a 2 nd weight.

For example, the radiation diagnosis apparatus according to embodiment 1 is an X-ray CT apparatus, the two-dimensional direction is a cone angle direction and a fan angle direction, the radiation is an X-ray, the 1 st detection element and the 2 nd detection element are arranged along the cone angle direction, and an output (for example, ideal output) corresponding to the reconstruction position is determined using the 1 st weight corresponding to the 1 st cone angle from the reference line to the 1 st detection element and the 2 nd weight corresponding to the 2 nd cone angle from the reference line to the 2 nd detection element. In this case, in the radiation diagnosis apparatus according to the present embodiment, the 1 st output, the 2 nd output, and the output (for example, ideal output) corresponding to the reconstruction position may be the count number obtained by counting photons in the X-rays. The radiation 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 radiation diagnosis apparatus according to embodiment 1, the 1 st weight and the 2 nd weight are set based on the material of the 1 st detection element and the 2 nd detection element for converting radiation into electrons or visible light, the thickness of the material, and the angle at which the radiation is incident on the 1 st detection element (i.e., the angle of incidence of the X-ray obliquely entering the opposing surface), and as the 1 st angle increases, the 1 st weight decreases and the 2 nd weight increases.

Because of this, according to the radiation diagnosis apparatus of embodiment 1, it is possible to correct the influence on the plain raw data or the raw data caused by the oblique incidence of the X-rays to the opposing surface due to at least one of the cone angle and the fan angle. Thus, according to the present radiation diagnostic apparatus, the positional deviation of the detection position of the radiation caused by the oblique incidence of the X-ray can be corrected, and projection data at a position corresponding to the original detection position of the X-ray can be obtained. As described above, according to the present radiation diagnostic apparatus, degradation of image quality such as image extension in the body axis direction and/or the left-right direction of the subject P is reduced, and a medical image (an X-ray image based on projection data or a corrected reconstructed image) with improved spatial resolution can be generated. Therefore, according to the present radiation diagnostic apparatus, the quality of the radiation examination of the subject P can be improved.

(application example)

The PCCT apparatus 1 collects data (count number) for each energy domain (energy bin). The semiconductor crystal of the X-ray detector 12 in the PCCT apparatus 1 has a smaller absorption cross-sectional area of the X-rays than a normal integrated 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 X-ray detector. Because of this, the higher the energy of the X-rays, the greater the impact caused by the 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, that is, the higher energy reconstructed image, and the image extends along the body axis direction of the subject P.

Therefore, this application example uses a plurality of weight matrices corresponding to a plurality of energy bins, and determines an ideal output for each of the plurality of energy bins. In the plurality of weight matrices, the contribution rate k to the own detection element corresponding to the 1 st weight _N，N Lowering a contribution rate k corresponding to a 2 nd weight from a 2 nd detection element including an adjacent element to a 1 st detection element in the X-ray detector 12 closer to an end portion on the +side in the Z-axis direction _N，N’>N And (3) increasing. In addition, among the plurality of weight matrices, a contribution ratio k corresponding to the 2 nd weight from the 2 nd detection element including the adjacent element to the 1 st detection element in the X-ray detector 12 which is closer to the end of the side in the Z-axis direction _N，N’<N And (3) increasing. In other words, among the plurality of representative energies representing the plurality of energy bins, the higher the energy, the smaller the 1 st weight of each of the plurality of energy bins; the higher the energy among the plurality of representative energies, the more the 2 nd weight of each of the plurality of energy bins increases.

The 1 st output of the present application example is, for example, a plurality of 1 st count numbers corresponding to a plurality of energy bins of the X-rays. The 2 nd output of the present application is, for example, a plurality of 2 nd counts corresponding to a plurality of energy bins of the X-rays. At this time, the processing circuit 44 determines, by the determination function 447, the count number which is the output (for example, ideal output) corresponding to the reconstruction position of each of the plurality of energy bins based on the 1 st weight, the 2 nd weight, the 1 st count number, and the 2 nd count number for each of the plurality of energy bins.

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

Vector on left in the above formula (4)

An ideal output vector for each energy bin having, as a component, outputs (e.g., ideal outputs) corresponding to a plurality of reconstruction locations corresponding to a plurality of detection elements, respectively, is represented. Further, the right vector in the above formula (4)

The actual measurement output vector for each energy bin, which has a plurality of outputs (actual measurement values) corresponding to a plurality of detection elements, respectively, as components of the vector, is represented.

Furthermore, the weight matrix of each energy bin on the right side of equation (4) above

The plurality of weights associated with the plurality of sensing elements are represented 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 of each energy bin is equivalent to the actual measurement output vector of each energy bin

And an ideal output vector for each energy bin

The correlation coefficient of each component (output associated with each of the plurality of detection elements) is represented as a coefficient matrix (e.g., correlation matrix) of weights. Other features of the weight matrix for each energy bin are the same as those of embodiment 1, and therefore, description thereof is omitted. The processing in the determination function 447 is also repeated for each energy bin in the same manner as in embodiment 1, and therefore the description thereof will be omitted.

In the radiation diagnosis apparatus according to the application example of embodiment 1 described above, the 1 st output is a plurality of 1 st count numbers corresponding to a plurality of energy bins of the X-ray, the 2 nd output is a plurality of 2 nd count numbers corresponding to a plurality of energy bins, and the count numbers that are outputs (for example, ideal outputs) corresponding to the reconstruction positions of each of the plurality of energy bins are determined for each of the plurality of energy bins based on the 1 st weight, the 2 nd weight, the 1 st count number, and the 2 nd count number. Further, in the radiation diagnosis apparatus pertaining to the present application, among the plurality of representative energies representing the plurality of energy bins, the higher the energy, the smaller the 1 st weight of each of the plurality of energy bins; the higher the energy among the plurality of representative energies, the more the 2 nd weight of each of the plurality of energy bins increases.

As described above, according to the radiation diagnostic apparatus of the application example of embodiment 1, since the contribution ratio varies depending on the energy of the X-ray, the count number independently measured for each energy bin can be corrected using the weight matrix (coefficient matrix) for each energy bin. According to the radiation diagnosis apparatus of the present application example, the correction can be performed more accurately with respect to the oblique incidence of the X-rays, and the accuracy of the correction of the count number can be further improved. Further, in the semiconductor detector used as the X-ray detector 12, since the X-ray cross-sectional area is small, the influence of the oblique incidence of the X-rays tends to be large, and therefore, according to the radiation diagnosis apparatus of the present application example, the effect of correction can be further increased.

In addition, according to the radiation diagnostic apparatus of the present application example, the difference in the influence of the diagonal-in between the energy bins at the time of the Spectral imaging (Spectral imaging) by the operation of the determination function 447 can be alleviated, and furthermore, the influence of the diagonal-in of the X-rays can be accurately corrected even in the counting imaging (counting imaging) which is the accumulation of the Spectral imaging. That is, according to the radiation diagnostic apparatus of the present application example, the degree of positional deviation that varies depending on the energy bins can be corrected for each energy bin, so that positional deviation between energy bins is corrected, and accurate spectral imaging can be performed. Because of this, according to the radiation diagnostic apparatus of the present application example, the spatial resolution in the body axis direction of the reconstructed image can be improved. Other effects are similar to those of embodiment 1, and therefore, description thereof is omitted.

(modification)

In this modification, the X-ray detector 12 is constituted by a plurality of small modules having a plurality of detection elements. That is, in the X-ray detector 12 of the present modification, a large-area surface detector is constructed by arranging detectors in small module units instead of an integrated structure in which a plurality of detection elements are two-dimensionally arranged. At this time, when the small modules are arranged at the design position, a gap must occur between two adjacent small modules.

Fig. 4 is a diagram showing a part of the X-ray detector 12 on the side of the end portion opening from the middle plane together with the X-rays obliquely entering the X-ray detector 12 in the present modification. The difference between FIG. 2 and FIG. 4 is that at the Nth sense electrode C _N And (n+1) th readout electrode C _N+1 With a gap therebetween. As shown in FIG. 4, X-rays that are tilted into the gap are directed toward a sense electrode C containing adjacent elements _N Is inclined into the surrounding detection element. The components in the weight matrix of the present modification are shown in FIG. 4, and the weight matrix is examinedThe gap is set. That is, as shown in FIG. 4, the electrode C is formed corresponding to the read electrode _N When there is a gap between the 1 st detection element and the 2 nd detection element, the 1 st weight is set smaller than when there is no gap, and the 2 nd weight is set larger than when there is no gap.

With these, according to this modification, the components (correction terms) in the weight matrix of the application examples of embodiment 1 and embodiment 1 can be set in consideration of the increase in the oblique incidence of the X-rays due to the gap, and the discontinuity of the actually measured output caused by the gap between the small modules of the X-ray detector 12 can be compensated for. That is, according to this modification, even in a region where a plurality of small-sized detector modules are spliced, gaps between the detector modules are not equally spaced for preventing interference, or a region where influence of the oblique penetration of the X-rays into the adjacent element is large due to the gaps between the detector modules, the ideal output can be calculated by setting the weight. Other effects of the present modification are the same as those of embodiment 1 and the application example of embodiment 1, and therefore, the description thereof will be omitted.

(embodiment 2)

The difference from embodiment 1 is that the radiation detector has a processing circuit that performs the decision function 447. In the following, for the sake of explanation, it is assumed that the radiation detector is an X-ray detector mounted in the PCCT apparatus. At this time, in the PCCT apparatus 1 shown in fig. 1, the decision function 447 in the processing circuit 44 is no longer required.

Fig. 5 is a diagram showing an example of the structure of the X-ray detector 20 corresponding to the radiation detector of the present embodiment. As shown in fig. 5, the X-ray detector 20 has a plurality of X-ray detection elements 21, a data acquisition circuit (DAS) 18, and a processing circuit 23. The plurality of X-ray detection elements 21 and the plurality of X-ray detection elements 21 arranged in the two-dimensional direction are the same as those of embodiment 1, and therefore, the description thereof is omitted. The plurality of X-ray detection elements 21 correspond to a plurality of radiation detection elements, for example.

The DAS18 collects the 1 st count number based on outputs from the 1 st detection element included in the plurality of X-ray detection elements, and collects the 2 nd count number based on outputs from the 2 nd detection elements around the 1 st detection element, for example. The structure and function of DAS18 are the same as those of embodiment 1, and therefore, description thereof is omitted.

The processing circuit 23 is, for example, a processor, and reads out and executes each program from the memory 41, thereby realizing a function corresponding to each read-out program. The hardware configuration of the processing circuit 23 is the same as that of embodiment 1, and therefore, the description thereof is omitted. The processing circuit 23 determines, by the determination function 447, the ideal count for the 1 st detection element when the surface on which the radiation first reaches in the 1 st detection element is set as the radiation incident position, based on the 1 st count and the 2 nd count. The specific processing performed by the decision function 447 is the same as that of embodiment 1, and therefore, the description thereof is omitted. The processing procedure of the output determination processing of the present embodiment is the same as that of embodiment 1, and therefore, the description thereof is omitted.

As the application example and the modification of embodiment 2, the application example and the modification of embodiment 1 can be used appropriately, and therefore, the description thereof will be omitted. Note that, since the effects of embodiment 2 are similar to those of embodiment 1, the description thereof is omitted.

In the case where the technical idea of the present embodiment is implemented by the output determination method, the output determination method collects the 1 st output concerning the 1 st detection element included in the plurality of radiation detection elements arranged in the two-dimensional direction and the 2 nd output concerning the 2 nd detection elements around the 1 st detection element, and determines the output corresponding to the reconstruction position of the 1 st detection element based on the 1 st output and the 2 nd output. The processing procedure and effect of the present output determination method are the same as those of embodiment 1, and therefore, the description thereof will be omitted.

When the technical idea of the present embodiment is realized by an output determination program, the output determination program causes a computer to realize the following processing: the 1 st output concerning the 1 st detection element included in the plurality of radiation detection elements arranged in the two-dimensional direction and the 2 nd output concerning the 2 nd detection element around the 1 st detection element are collected, and the output corresponding to the reconstruction position of the 1 st detection element is determined based on the 1 st output and the 2 nd output. In this case, a program for causing a computer to execute the method may be stored in a storage medium such as a magnetic disk (hard disk or the like), an optical disk (CD-ROM, DVD or the like), or a semiconductor memory and distributed. The processing procedure and effects in the output determination program are the same as those in embodiment 1, and therefore, the description thereof will be omitted.

According to at least one embodiment or the like described above, the influence of the oblique entrance of the radiation beam to the radiation detector can be reduced.

Several embodiments of the present invention have been described, but these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

As for the above embodiments and the like, the following supplementary notes are disclosed as an aspect and optional feature of the present invention.

(additionally, 1)

A radiation detector is provided with: a plurality of radiation detection elements arranged in a two-dimensional direction; and a determining unit configured to determine an output corresponding to a reconstruction position of the 1 st detection element based on the 1 st output of the 1 st detection element and the 2 nd output of the 2 nd detection element included in the plurality of radiation detection elements.

(additionally remembered 2)

The determination unit may determine the output corresponding to the reconstruction position by using a 1 st weight corresponding to a 1 st angle from the reference line to the 1 st detection element and a 2 nd weight corresponding to a 2 nd angle from the reference line to the 2 nd detection element in a direction in a plane including the 1 st detection element and the 2 nd detection element in the two-dimensional direction; the 2 nd weight is provided to each 2 nd detection element of the plurality of 2 nd detection elements.

(additionally, the recording 3)

The determination unit may determine an output corresponding to the reconstruction position by adding a 1 st multiplication value obtained by multiplying the 1 st output by the 1 st weight to a 2 nd multiplication value obtained by multiplying the 2 nd output by the 2 nd weight.

(additionally remembered 4)

The radiation detector may be mounted on an X-ray computed tomography apparatus; the two-dimensional directions are a cone angle direction and a fan angle direction; the radiation is X-rays; the 1 st detection element and the 2 nd detection element are arranged along the taper angle direction; the determination unit determines an output corresponding to the reconstruction position using the 1 st weight corresponding to a 1 st taper angle from the reference line to the 1 st detection element and the 2 nd weight corresponding to a 2 nd taper angle from the reference line to the 2 nd detection element.

(additionally noted 5)

The 1 st output, the 2 nd output, and the output corresponding to the reconstruction position may be a count obtained by counting photons in the X-ray.

(additionally described 6)

The 1 st output may be a plurality of 1 st counts corresponding to a plurality of energy bins of the X-rays; the 2 nd output is a plurality of 2 nd counts corresponding to the plurality of energy bins; the determination unit determines, for each of the plurality of energy bins, a count number that is an output corresponding to the reconstruction position of each of the plurality of energy bins based on the 1 st weight, the 2 nd weight, the 1 st count number, and the 2 nd count number.

(additionally noted 7)

The 1 st weight of each of the plurality of energy bins may be decreased as the energy is higher among the plurality of representative energies representing the plurality of energy bins; the 2 nd weight of each of the plurality of energy bins increases as the energy is higher among the plurality of representative energies.

(additionally noted 8)

The 1 st weight and the 2 nd weight may be set based on a material of the 1 st detection element and the 2 nd detection element for converting the radiation into electrons or visible light, a thickness of the material, and a 1 st angle at which the radiation is incident on the 1 st detection element; as the 1 st angle increases, the 1 st weight decreases and the 2 nd weight increases.

(additionally, the mark 9)

In the case where there is a gap between the 1 st detection element and the 2 nd detection element, the 1 st weight may be set smaller than in the case where there is no gap, and the 2 nd weight may be set larger than in the case where there is no gap.

(additionally noted 10)

An X-ray computed tomography apparatus on which the radiation detector described in any one of supplementary notes 1 to 10 is mounted, 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.

(additionally noted 11)

The reconstruction position may be a position used for calculation of the reconstruction based on the output and indicating the representative point of the 1 st detection element.

(additional recording 12)

The radiation detector may further include a data collection circuit that collects a 1 st count based on an output from a 1 st detection element included in the plurality of radiation detection elements and collects a 2 nd count based on an output from a 2 nd detection element around the 1 st detection element; the determination unit determines the count number corresponding to the position of the reconstruction of the 1 st detection element based on the 1 st count number and the 2 nd count number.

(additional recording 13)

An X-ray computed tomography apparatus provided with the radiation detector described in any one of supplementary notes 1 to 12.

(additional recording 14)

An output determining method for collecting 1 st output concerning 1 st detection elements included in a plurality of radiation detection elements arranged in a two-dimensional direction and 2 nd output concerning 2 nd detection elements around the 1 st detection elements; based on the 1 st output and the 2 nd output, an output corresponding to the reconstruction position of the 1 st detection element is determined.

(additional recording 15)

A computer-readable non-transitory storage medium storing an output decision program that causes a computer to realize: collecting 1 st output concerning a 1 st detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction and 2 nd output concerning a 2 nd detection element around the 1 st detection element; based on the 1 st output and the 2 nd output, an output corresponding to the reconstruction position of the 1 st detection element is determined.

Claims

1. A radiation diagnosis device is provided with:

a plurality of radiation detection elements arranged in a two-dimensional direction; and

and a processing circuit configured to determine an output corresponding to a reconstruction position of the 1 st detection element based on a 1 st output of the 1 st detection elements included in the plurality of radiation detection elements and a 2 nd output of the 2 nd detection elements included in the plurality of radiation detection elements.

2. The radiation diagnosis apparatus according to claim 1, wherein,

the processing circuit determines an output corresponding to the reconstruction position using a 1 st weight corresponding to a 1 st angle from the reference line to the 1 st detection element and a 2 nd weight corresponding to a 2 nd angle from the reference line to the 2 nd detection element in a direction in a plane including the 1 st detection element and the 2 nd detection element in the two-dimensional direction;

The 2 nd weight is provided to each 2 nd detection element of the plurality of 2 nd detection elements.

3. The radiation diagnosis apparatus according to claim 2, wherein,

the processing circuit determines an output corresponding to the reconstruction position by adding a 1 st multiplication value obtained by multiplying the 1 st output by the 1 st weight to a 2 nd multiplication value obtained by multiplying the 2 nd output by the 2 nd weight.

4. The radiation diagnosis apparatus according to claim 2, wherein,

the above-mentioned radiation diagnosis apparatus is an X-ray computed tomography apparatus,

the above two-dimensional directions are the cone angle direction and the fan angle direction,

the above-mentioned radiation is an X-ray,

the 1 st detection element and the 2 nd detection element are arranged along the taper angle direction,

the processing circuit determines an output corresponding to the reconstruction position using the 1 st weight corresponding to a 1 st taper angle from the reference line to the 1 st detection element and the 2 nd weight corresponding to a 2 nd taper angle from the reference line to the 2 nd detection element.

5. The radiation diagnosis apparatus according to claim 4, wherein,

the 1 st output, the 2 nd output, and the output corresponding to the reconstruction position are counts obtained by counting photons in the X-ray.

6. The radiation diagnosis apparatus according to claim 5, wherein,

the 1 st output is a plurality of 1 st counts corresponding to a plurality of energy bins of the X-rays,

the 2 nd output is a plurality of 2 nd counts corresponding to the plurality of energy bins,

the processing circuit determines, for each of the plurality of energy bins, a count number that is an output corresponding to the reconstruction position of each of the plurality of energy bins based on the 1 st weight, the 2 nd weight, the 1 st count number, and the 2 nd count number.

7. The radiation diagnosis apparatus according to claim 6, wherein,

the 1 st weight of each of the plurality of energy bins is reduced as the energy is higher among the plurality of representative energies representing the plurality of energy bins;

the 2 nd weight of each of the plurality of energy bins increases as the energy is higher among the plurality of representative energies.

8. The radiation diagnosis apparatus according to claim 2, wherein,

the 1 st weight and the 2 nd weight are set based on a material that converts the radiation into electron or visible light in the 1 st detection element and the 2 nd detection element, a thickness of the material, and a 1 st angle at which the radiation is incident on the 1 st detection element;

As the 1 st angle increases, the 1 st weight decreases and the 2 nd weight increases.

9. The radiation diagnosis apparatus according to claim 2, wherein,

when there is a gap between the 1 st detection element and the 2 nd detection element, the 1 st weight is set smaller than that when there is no gap, and the 2 nd weight is set larger than that when there is no gap.

10. The radiation diagnosis apparatus according to claim 1, wherein,

the processing circuit performs reconstruction processing on projection data based on an output corresponding to the reconstruction position, and generates a reconstructed image.

11. The radiation diagnosis apparatus according to claim 1, wherein,

the reconstruction position is a position used for calculation of the reconstruction based on the output and representing the representative point of the 1 st detection element.

12. A radiation detector is provided with:

a plurality of radiation detection elements arranged in a two-dimensional direction;

a data collection circuit that collects a 1 st count number based on outputs from a 1 st detection element included in the plurality of radiation detection elements, and collects a 2 nd count number based on outputs from a 2 nd detection element around the 1 st detection element; and

And a processing circuit configured to determine a count number corresponding to a reconstructed position of the 1 st detection element based on the 1 st count number and the 2 nd count number.

13. An output determining method includes the steps of:

collecting 1 st output concerning a 1 st detection element included in a plurality of radiation detection elements arranged in a two-dimensional direction and 2 nd output concerning a 2 nd detection element around the 1 st detection element;

based on the 1 st output and the 2 nd output, an output corresponding to the reconstruction position of the 1 st detection element is determined.