Direct conversion type X-ray detector, X-ray detection method, and X-ray computed tomography apparatus

Abstract

To alleviate a reduction in spatial resolution in a cone angle direction of a direct conversion type X-ray detector.SOLUTION: A direct conversion type X-ray detector according to an embodiment comprises: a plurality of anode electrodes; at least one cathode electrode; and an electric field forming unit. The plurality of anode electrodes are arranged in a cone angle direction of an incident X-ray. The cathode electrode is located closer to the incident side of the X-ray than the plurality of anode electrodes, and faces the plurality of anode electrodes. The electric field forming unit forms an electric field in a direction based on the cone angle of the X-ray between the plurality of anode electrodes and the cathode electrode.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The embodiments disclosed in this specification and the drawings relate to a direct conversion type X-ray detector, an X-ray detection method, and an X-ray computed tomography apparatus. [Background technology]

[0002] In a conventional X-ray computed tomography (CT) device, a technique is known in which an X-ray detector with an arc surface is constructed by arranging detection modules, each having a planar array of X-ray conversion elements, in an arc shape in the fan angle direction. Because such an X-ray detector with an arc surface is flat in the cone angle direction, the incident angle of X-rays on the X-ray conversion elements increases as the cone angle increases.

[0003] Generally, in the reconstruction theory of detected X-rays, X-rays are considered to have been incident at the position on the surface of the X-ray conversion element where they were incident. However, when X-rays are incident obliquely, they may be absorbed not only by the X-ray conversion element where they were incident, but also by other adjacent X-ray conversion elements. This may reduce the spatial resolution in the cone angle direction of the X-ray detector, which may cause a deterioration in the image quality of X-ray image data. In particular, X-ray conversion elements used in direct conversion X-ray detectors, which directly convert X-rays into electric charges, are generally thicker than X-ray conversion elements used in indirect conversion X-ray detectors, and are therefore more susceptible to the effects of oblique X-ray incidence. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-075078 Summary of the Invention [Problem to be solved by the invention]

[0005] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to reduce the degradation of spatial resolution in the cone angle direction of a direct conversion X-ray detector. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be positioned as other problems. [Means for solving the problem]

[0006] A direct conversion X-ray detector according to an embodiment includes a plurality of anode electrodes, at least one cathode electrode, and an electric field forming unit. The anode electrodes are arranged in the cone angle direction of incident X-rays. The cathode electrode is located on the X-ray incident side of the anode electrodes and faces the anode electrodes. The electric field forming unit forms an electric field between the anode electrodes and the cathode electrode in a direction based on the X-ray cone angle. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of an X-ray CT apparatus according to the first embodiment. [Figure 2] FIG. 2 is a diagram showing an example of the configuration of the X-ray detector according to the first embodiment. [Figure 3] FIG. 3 is a diagram illustrating an example of the configuration of an X-ray detector according to a comparative example. [Figure 4] FIG. 4 is a diagram showing in detail an example of the direction of the electric field of the X-ray detector according to the first embodiment. [Figure 5] FIG. 5 is a flowchart showing an example of the flow of X-ray detection in the X-ray CT apparatus according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing an example of the configuration of the X-ray detector according to the second embodiment. [Figure 7] FIG. 7 is a diagram showing an example of the configuration of an X-ray detector according to the third embodiment. [Figure 8] FIG. 8 is a diagram showing an example of the configuration of an X-ray detector according to the fourth embodiment. [Figure 9] FIG. 9 is a diagram showing another example of the configuration of the X-ray detector according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of a direct conversion type X-ray detector, an X-ray detection method, and an X-ray computed tomography apparatus will be described in detail with reference to the drawings.

[0009] (First embodiment) 1 is a diagram showing an example of the configuration of an X-ray computed tomography (CT) apparatus 1 (hereinafter referred to as the X-ray CT apparatus 1) according to the first embodiment. The X-ray CT apparatus 1 may also be referred to as a radiation image diagnostic apparatus.

[0010] As shown in FIG. 1, the X-ray CT apparatus 1 includes a gantry device 10, a bed device 30, and a console device 40.

[0011] In this embodiment, the rotation axis of the rotating frame 13 in a non-tilted state or the longitudinal direction of the tabletop 33 of the bed device 30 is defined as the Z-axis direction, the axis perpendicular to the Z-axis direction and horizontal to the floor surface is defined as the X-axis direction, and the axis perpendicular to the Z-axis direction and perpendicular to the floor surface is defined as the Y-axis direction. For convenience of explanation, multiple gantry devices 10 are depicted in Figure 1, but the actual configuration of the X-ray CT device 1 includes only one gantry device 10.

[0012] The gantry 10 and the bed 30 operate based on a user's operation via the console 40 or an operation unit provided on the gantry 10 or the bed 30. The gantry 10, the bed 30, and the console 40 are connected to each other by wire or wirelessly so as to be able to communicate with each other.

[0013] The gantry device 10 is an apparatus having an imaging system that irradiates an object P with X-rays 100 and collects detection data of the X-rays 100 that have passed through the object P. More specifically, the gantry device 10 has an X-ray tube 11 (X-ray generation 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.

[0014] The X-ray tube 11 is a vacuum tube that generates X-rays 100 by irradiating thermoelectrons from a cathode (filament) toward an anode (target) through application of high voltage and supply of filament current from an X-ray high voltage device 14. X-rays 100 are generated when the thermoelectrons collide with the target. The X-rays 100 generated at the tube focus in the X-ray tube 11 are shaped into a cone beam via, for example, a collimator 17, and are irradiated onto the subject P. For example, the X-ray tube 11 may be a rotating anode type X-ray tube that generates X-rays by irradiating a rotating anode with thermoelectrons.

[0015] As shown in Figure 1, X-rays 100 irradiated in a cone beam shape spread in a fan shape in the X-axis direction. For this reason, the angle indicating the spread of X-rays 100 irradiated in a cone beam shape in the X-axis direction is called the fan angle. Also, the angle indicating the depth of X-rays 100 irradiated in a cone beam shape in the Z-axis direction is called the cone angle. For this reason, the X-axis direction is also called the fan angle direction, and the Z-axis direction is also called the cone angle direction.

[0016] The X-ray detector 12 detects the X-rays emitted from the X-ray tube 11 and passed through the subject P, and outputs an electrical signal corresponding to the X-ray dose to the DAS 18.

[0017] The X-ray detector 12 has, for example, a plurality of detector element rows in which a plurality of detector elements are arranged in the channel direction along one arc centered on the focal point of the X-ray tube 11. Each of the plurality of detector elements detects the amount of incident X-rays 100. There are various types of X-ray CT apparatus 1, such as a rotate / rotate-type (third generation CT) in which the X-ray tube 11 and the X-ray detector 12 rotate together around the subject P, and a stationary / rotate-type (fourth generation CT) in which a large number of X-ray detector elements arrayed in a ring shape are fixed and only the X-ray tube 11 rotates around the subject P, and any of these types can be applied to this embodiment.

[0018] More specifically, the X-ray detector 12 is a direct conversion type X-ray detector having a semiconductor element that converts incident X-rays into electric charges. The X-ray detector 12 of this embodiment includes at least one high-voltage electrode, at least one semiconductor element, and multiple readout electrodes. The semiconductor element is also called an X-ray conversion element.

[0019] The X-ray detector 12 also includes a potential control device 120 that controls the potential of the high-voltage electrode. The potential control device 120 is an example of an electric field forming unit in this embodiment. The configuration of the X-ray detector 12 will be described in detail later.

[0020] Furthermore, the X-ray detector 12 of this embodiment may be of an energy integrated type collection method or a photon counting type collection method.

[0021] The rotating frame 13 supports the X-ray tube 11 and the X-ray detector 12 rotatably around a rotation axis. Specifically, the rotating frame 13 is an annular frame that supports the X-ray tube 11 and the X-ray detector 12 facing each other and rotates the X-ray tube 11 and the X-ray detector 12 using a control device 15, which will be described later. The rotating frame 13 is rotatably supported on a fixed frame made of a metal such as aluminum. The rotating frame 13 receives power from a drive mechanism of the control device 15 and rotates around the rotation axis at a constant angular velocity.

[0022] The rotating frame 13 supports not only the X-ray tube 11 and the X-ray detector 12, but also the X-ray high voltage generator 14 and the DAS 18. The rotating frame 13 is housed in a substantially cylindrical housing having an opening (bore) that forms the imaging space. The central axis of the opening coincides with the rotation axis of the rotating frame 13.

[0023] The X-ray high voltage device 14 includes a high-voltage generator having electrical circuits such as a transformer and a rectifier, and having the function of generating a high voltage to be applied to the X-ray tube 11 and a filament current to be supplied to the X-ray tube 11, and an X-ray control device that controls the output voltage according to the X-rays emitted by the X-ray tube 11. The high-voltage generator may be of a transformer type or an inverter type. The X-ray high-voltage device 14 may be provided on the rotating frame 13, or may be provided on the fixed frame (not shown) side of the gantry device 10. The fixed frame is a frame that rotatably supports the rotating frame 13.

[0024] The control device 15 includes a processing circuit having a central processing unit (CPU) and the like, and a drive mechanism for a motor, an actuator, and the like. The processing circuit includes, as hardware resources, a processor such as a CPU or a microprocessing unit (MPU) and a memory such as a read-only memory (ROM) or a random access memory (RAM). The control device 15 may also be implemented by a processor such as a graphics processing unit (GPU), an application specific integrated circuit (ASIC), or a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), or a field programmable gate array (FPGA)). When the processor is a CPU, for example, the processor realizes a function by reading and executing a program stored in memory. On the other hand, when the processor is an ASIC, instead of storing a program in memory, the function is directly incorporated into the processor circuit as a logic circuit. Each processor in this embodiment is not limited to being configured as a single circuit, but may be configured as a single processor by combining multiple independent circuits, or may be configured to realize the functions of a single processor by integrating multiple components.

[0025] The control device 15 also has a function of receiving input signals from the console device 40 or an input interface 43 attached to the gantry 10 and controlling the operation of the gantry 10 and the bed 30. For example, the control device 15 receives input signals and controls the rotation of the rotating frame 13, the tilt of the gantry 10, and the operation of the bed 30 and the tabletop 33. Note that the control of tilting the gantry 10 may be realized by the control device 15 rotating the rotating frame 13 around an axis parallel to the X-axis direction based on inclination angle (tilt angle) information input via the input interface 43 attached to the gantry 10. The control device 15 may be provided in the gantry 10 or in the console device 40.

[0026] The wedge 16 is a filter for adjusting the amount of X-rays 100 irradiated from the X-ray tube 11. Specifically, the wedge 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 or a bow-tie filter, and is a filter made by processing aluminum to have a predetermined target angle and a predetermined thickness.

[0027] The collimator 17 is a lead plate or the like for constricting the X-rays 100 transmitted through the wedge 16 to an X-ray irradiation range, and a slit is formed by combining a plurality of lead plates or the like.

[0028] The DAS (Data Acquisition System) 18 has an amplifier that amplifies the electrical signals output from each X-ray detection element of the X-ray detector 12 and an A / D converter that converts the electrical signals into digital signals, and generates detection data. The detection data generated by the DAS 18 is transferred to the console device 40. The DAS 18 is also an example of a data acquisition unit.

[0029] In this embodiment, the term "detection data" encompasses both pure raw data detected by the X-ray detector 12 and before preprocessing, and raw data obtained by preprocessing the pure raw data. The data before preprocessing (detection data) and the data after preprocessing may also be collectively referred to as projection data.

[0030] The bed device 30 is a device on which the subject P to be scanned is placed and moved, and includes a base 31, a bed driving device 32, a top 33, and a top support frame 34. The base 31 is a housing that supports the top support frame 34 so that it can move vertically. The bed driving device 32 is a motor or actuator that moves the top 33, on which the subject P is placed, in the longitudinal direction of the top 33. The bed driving device 32 moves the top 33 under the control of the console device 40 or the control device 15. The top 33, which is provided on the upper surface of the top support frame 34, is a plate on which the subject P is placed. Note that the bed driving device 32 may move the top support frame 34 in addition to the top 33 in the longitudinal direction of the top 33.

[0031] The console device 40 is a device that controls the gantry device 10 and generates CT image data based on the scan results obtained by the gantry device 10. The console device 40 has 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 (BUS).

[0032] The memory 41 is realized by, for example, a semiconductor memory element such as a random access memory (RAM), a flash memory, a hard disk drive (HDD), a solid state drive (SSD), an optical disk, etc. The memory 41 may also be a portable storage medium such as a compact disc (CD), a digital versatile disc (DVD), or a flash memory, or a drive that reads and writes various information from and to a semiconductor memory element such as a random access memory (RAM). The memory 41 stores, for example, projection data and reconstructed image data. The storage area of ​​the memory 41 may be located within the X-ray CT apparatus 1 or may be located in an external storage device connected via a network. The memory 41 stores a control program according to this embodiment. The memory 41 is an example of a storage unit.

[0033] The display 42 displays various types of information. For example, the display 42 outputs medical images (CT images) generated by the processing circuitry 44, a GUI (Graphical User Interface) for receiving various operations from the operator, and the like. For example, the display 42 may be a liquid crystal display (LCD), an organic electroluminescence display (OLED), a plasma display, or any other display, as appropriate. The display 42 may also be provided on the gantry device 10. The display 42 may be a desktop type, or may be configured as a tablet terminal or the like capable of wireless communication with the console device 40 main body.

[0034] The input interface 43 accepts various input operations from the operator, converts the accepted input operations into electrical signals, and outputs the electrical signals to the processing circuitry 44. For example, the input interface 43 accepts from the operator acquisition conditions for acquiring projection data, reconstruction conditions for reconstructing CT images, image processing conditions for generating post-processed images from CT images, etc. As the input interface 43, for example, a mouse, keyboard, trackball, switch, button, joystick, touchpad, touch panel display, etc. can be used as appropriate.

[0035] In this embodiment, the input interface 43 is not limited to one having physical operation components such as a mouse, keyboard, trackball, switch, button, joystick, touchpad, and touch panel display. For example, an example of the input interface 43 also includes an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the device and outputs the electrical signal to the processing circuit 44. The input interface 43 is also an example of an input unit. The input interface 43 may also be provided in the gantry device 10. The input interface 43 may also be configured as a tablet terminal or the like that is capable of wireless communication with the console device 40 main body.

[0036] The processing circuitry 44 controls the overall operation of the X-ray CT apparatus 1 in response to electrical signals of input operations output from the input interface 43. For example, the processing circuitry 44 includes a system control function 441, a pre-processing function 442, a reconstruction processing function 443, a scan control function 444, an image processing function 445, and a display control function 446. Here, for example, the processing functions executed by the system control function 441, the pre-processing function 442, the reconstruction processing function 443, the scan control function 444, the image processing function 445, and the display control function 446, which are components of the processing circuitry 44 shown in FIG. 1, are recorded in the memory 41 in the form of computer-executable programs. The processing circuitry 44 is, for example, a processor, which reads and executes each program from the memory 41 to realize a function corresponding to the read program. In other words, the processing circuitry 44 in a state in which each program has been read has the functions shown in the processing circuitry 44 in FIG. 1. The system control function 441 is an example of a control unit. The pre-processing function 442 is an example of a pre-processing unit. The reconstruction processing function 443 is an example of a reconstruction processing unit. The scan control function 444 is an example of a scan control unit. The image processing function 445 is an example of an image processing unit. The display control function 446 is an example of a display control unit. Furthermore, the processing circuitry 44 may be an example of a control unit.

[0037] 1 illustrates a case where the system control function 441, preprocessing function 442, reconstruction processing function 443, scan control function 444, and display control function 446 are realized by a single processing circuit 44, but the embodiment is not limited to this. For example, the processing circuit 44 may be configured by combining multiple independent processors, and each processor may realize each processing function by executing a respective program. Furthermore, each processing function of the processing circuit 44 may be realized by being appropriately distributed or integrated into a single or multiple processing circuits.

[0038] The system control function 441 controls various functions of the processing circuit 44 based on input operations received from an operator via the input interface 43 .

[0039] The pre-processing function 442 generates data by performing pre-processing such as logarithmic conversion, offset correction, inter-channel sensitivity correction, and beam hardening correction on the detection data output from the DAS 18 .

[0040] The reconstruction processing function 443 performs reconstruction processing using a filtered back projection method, an iterative reconstruction method, or the like on the projection data generated by the preprocessing function 442 to generate CT image data.

[0041] The scan control function 444 acquires two-dimensional positioning image data of the subject P for determining the scan range, imaging conditions, etc. Note that the positioning image data may also be called scano image data or scout image data.

[0042] The image processing function 445 converts the CT image data generated by the reconstruction processing function 443 into tomographic image data of an arbitrary cross section or three-dimensional image data by a known method based on an input operation received from the operator via the input interface 43. Note that the generation of three-dimensional image data may be performed directly by the reconstruction processing function 443.

[0043] The display control function 446 causes the display 42 to display the tomographic image data and three-dimensional image data processed by the image processing function 445. The display control function 446 also causes the display 42 to display various GUIs (Graphical User Interfaces).

[0044] Next, the X-ray detector 12 will be described in detail.

[0045] Fig. 2 is a diagram showing an example of the configuration of the X-ray detector 12 according to the first embodiment. Fig. 2 shows the X-ray detector 12 as viewed from the X-axis direction.

[0046] The X-ray detector 12 includes a plurality of high-voltage electrodes 121a-121e, one semiconductor element 122, and a plurality of read electrodes 123a-123e. The plurality of high-voltage electrodes 121a-121e, the semiconductor element 122, and the plurality of read electrodes 123a-123e form one detection module 124. The X-ray detector 12 includes a plurality of detection modules 50 arranged in the fan angle direction. Note that the number of high-voltage electrodes 121a-121e and read electrodes 123a-123e included in one detection module 124 is not limited to the example shown in FIG. 2.

[0047] Hereinafter, when there is no need to distinguish between the individual high-voltage electrodes 121a to 121e, they will simply be referred to as high-voltage electrodes 121. Furthermore, when there is no need to distinguish between the individual read electrodes 123a to 123e, they will simply be referred to as read electrodes 123.

[0048] 2 shows a graph representing the distribution of the potential of the high-voltage electrodes 121a to 121e for each position in the cone angle direction of the X-rays incident on the X-ray detector 12. Since the high-voltage electrodes 121a to 121e have negative potentials, the vertical axis of the graph has a unit of "-V."

[0049] In this embodiment, in one detection module 124, the plurality of read electrodes 123a to 123e and the plurality of high voltage electrodes 121a to 121e are arranged in the cone angle direction of the X-rays 100, respectively.

[0050] In the X-ray detector 12, multiple detection modules 124 are arranged to form a curve in the fan angle direction. Therefore, the shape of the X-ray detector 12 is an arc surface in the fan angle direction. In addition, the shape of the X-ray detector 12 is a flat surface in the cone angle direction. Therefore, the incident angle of the X-rays 100 with respect to the semiconductor element 122 increases as the cone angle increases in the X-ray detector 12.

[0051] The high-voltage electrodes 121a to 121e are located closer to the incident side of the X-rays 100 than the read electrodes 123a to 123e, and face the read electrodes 123a to 123e. The high-voltage electrodes 121a to 121e are an example of cathode electrodes in this embodiment. The high-voltage electrodes 121a to 121e are arranged along the cone angle direction of the incident X-rays 100.

[0052] The semiconductor element 122 is located between the high voltage electrodes 121a to 121e and the readout electrodes 123a to 123e, and converts the X-rays 100 incident from the high voltage electrodes 121a to 121e side into electric charges.

[0053] The readout electrodes 123a to 123e read out, as electric signals, the electric charges converted from the X-rays 100 by the semiconductor element 122. The electric signals read out by the readout electrodes 123a to 123e are amplified by the DAS 18, converted into digital signals, and transferred to the console device 40 as detection data. The readout electrodes 123a to 123e are an example of anode electrodes in this embodiment. The reading out of electric charges by the readout electrodes 123a to 123e is also referred to as collecting electric charges.

[0054] The high-voltage electrodes 121a to 121e have a negative potential, and the readout electrodes 123a to 123e have a positive potential. Due to the potential difference between the high-voltage electrodes 121a to 121e and the readout electrodes 123a to 123e, the electric charges converted from the X-rays by the semiconductor element 122 move to the readout electrodes 123a to 123e. An electric field is formed between the high-voltage electrodes 121a to 121e and the readout electrodes 123a to 123e.

[0055] More specifically, the electric field between the high-voltage electrodes 121a-121e and the readout electrodes 123a-123e is formed by a collection of electric fields formed by countless point charges. The direction of the electric field as a whole is determined by the size and density distribution of each point charge.

[0056] Furthermore, in this embodiment, the potential control device 120 controls each of the high-voltage electrodes 121a-121e, among the multiple high-voltage electrodes 121a-121e arranged in the cone angle direction of the incident X-rays 100, so that the potential of the high-voltage electrodes 121 increases as they are further from the center (midplane) in the cone angle direction. For example, the potential control device 120 applies different voltages to the multiple high-voltage electrodes 121a-121e at different positions along the cone angle direction, thereby generating an electric field oriented based on the cone angle. The potential control device 120 receives power from a power supply device (not shown).

[0057] As shown in FIG. 2, high-voltage electrode 121c located in the center in the cone angle direction has the lowest potential, and high-voltage electrode 121a and high-voltage electrode 121e located at the ends in the cone angle direction have the highest potential.

[0058] The specific values ​​of the potentials of the multiple high-voltage electrodes 121a-121e are not particularly limited, but are determined depending on the length of the X-ray detector 12 in the Z-axis direction and the size of the cone angle of the X-rays 100, etc. The polarities of the high-voltage electrodes 121a-121e and the number of the high-voltage electrodes 121a-121e may be changed depending on the characteristics of the X-ray detector 12.

[0059] It is assumed that even the potentials of the high voltage electrodes 121a and 121e, which have the highest potentials among the plurality of high voltage electrodes 121a to 121e, are lower than the potentials of the read electrodes 123a to 123e. It is also assumed that the potentials of the plurality of high voltage electrodes 121a to 121e are equal.

[0060] Specifically, the direction of the electric field between the high-voltage electrodes 121a to 121e and the read electrodes 123a to 123e travels in a straight line from the high-voltage electrode 121c to the read electrode 123c near the center of the cone angle direction of the X-ray detector 12. Furthermore, the direction of the electric field becomes more oriented away from the center of the cone angle direction of the X-ray detector 12 the farther away from the center of the cone angle direction of the X-ray detector 12. Therefore, the direction of the electric field between the high-voltage electrodes 121a to 121e and the read electrodes 123a to 123e is determined based on the cone angle of the X-rays 100. Since electric charges move along the direction of the electric field, the electric charges converted from the X-rays 100 by the semiconductor element 122 move to the read electrodes 123a to 123e in a direction determined based on the cone angle of the X-rays 100.

[0061] The direction of the electric field between the high-voltage electrodes 121a-121e and the readout electrodes 123a-123e is tilted so as to spread symmetrically toward both ends, for example, with the center position of the cone angle direction perpendicular to the X-ray tube 11 as the center. Note that the direction of the electric field does not need to be completely equal to the cone angle of the X-rays 100, as long as the tilt direction is at least the same.

[0062] For example, charges converted from X-rays 100 that have traveled straight from the X-ray tube 11 and are incident on the high-voltage electrode 121c of the X-ray detector 12 travel straight along the direction of the electric field and move to the readout electrode 123c. In this case, charges converted from X-rays 100 that are incident on the high-voltage electrode 121c are read out as an electrical signal from the readout electrode 123c. Charges converted from X-rays 100 that are incident on the high-voltage electrode 121e move obliquely along the direction of the electric field and move to the readout electrode 123e. Therefore, charges converted from X-rays 100 that are incident on the same high-voltage electrode 121 are read out by the same readout electrode 123.

[0063] Here, the relationship between the direction of the electric field and the readout of the electric charges will be described in detail with reference to FIGS.

[0064] First, as a comparative example, the configuration of a general X-ray detector will be described.

[0065] Fig. 3 is a diagram showing an example of the configuration of an X-ray detector 5 according to a comparative example. Fig. 3 shows a part of the X-ray detector 5 according to the comparative example as viewed from the X-axis direction. The right side of Fig. 3 is the center side in the cone angle direction of the X-ray detector 5, and the left side of Fig. 3 is the end side.

[0066] The X-ray detector 5 according to the comparative example includes a high-voltage electrode 51, a semiconductor element 52, and a plurality of read electrodes 53a to 53g. One set of the high-voltage electrode 51, the semiconductor element 52, and the plurality of read electrodes 53a to 53g is referred to as one detection module 50. The X-ray detector 5 includes a plurality of detection modules 50. When there is no need to particularly distinguish between the individual read electrodes 53a to 53g, they are simply referred to as read electrodes 53.

[0067] In this comparative example, one detection module 50 includes one high-voltage electrode 51. On the side of the high-voltage electrode 51 in this comparative example, there is no difference in potential in the cone angle direction and it is constant. Therefore, the direction of the electric field between the high-voltage electrode 51 and the multiple read electrodes 53a to 53g is perpendicular from the high-voltage electrode 51 to the multiple read electrodes 53a to 53g.

[0068] X-rays 100a to 100c incident on high-voltage electrode 51 are converted into electric charges by semiconductor element 52, but the position in the Y-axis direction of semiconductor element 52 at which X-rays 100a to 100c are absorbed is statistically random and therefore difficult to control.

[0069] 3, X-rays 100b incident on high-voltage electrode 51 are absorbed in first region 521 or second region 522 of semiconductor element 52. Charges converted from the portion of X-rays 100b absorbed in first region 521 of semiconductor element 52 move along the direction of the electric field to readout electrode 53d and are read out from readout electrode 53d. Charges converted from the portion of X-rays 100b absorbed in second region 522 of semiconductor element 52 move along the direction of the electric field to readout electrode 53c and are read out from readout electrode 53c. That is, in the comparative example, some of the charges converted from X-rays 100b incident from the same position on high-voltage electrode 51 are read out from readout electrode 53d, and the other portion is read out from readout electrode 53c adjacent to readout electrode 53d. Similarly, charges converted from X-rays 100a and 100c incident on other locations of the high-voltage electrode 51 are read out separately to the adjacent readout electrodes 53, respectively.

[0070] Generally, in the reconstruction theory of detected X-rays 100, the X-rays 100 are considered to have been incident at the surface position of the semiconductor element 52 on which they were incident. However, if the X-rays 100 are incident at an oblique angle, the X-rays 100 may be absorbed not only by the semiconductor element 52 on which they were incident, but also by other adjacent semiconductor elements. This may reduce the spatial resolution of the X-ray detector 5 in the cone angle direction, which may cause a deterioration in the image quality of the X-ray image data. In particular, the X-ray conversion elements used in direct conversion X-ray detectors, which directly convert the X-rays 100 into electric charges, are generally thicker than the X-ray conversion elements used in indirect conversion X-ray detectors, and are therefore more susceptible to the effects of oblique X-ray incidence.

[0071] In contrast to this, the X-ray detector 12 of this embodiment differs from the X-ray detector 5 of the comparative example in that the direction of the electric field between the high-voltage electrode 121 and the readout electrode 123 is tilted along the cone angle of the X-rays 100. Therefore, when the X-rays 100 obliquely enter the X-ray detector 12, the electric charges converted from the obliquely entering X-rays 100 move in the same direction as the obliquely entering X-rays 100.

[0072] Fig. 4 is a diagram showing in detail an example of the direction of the electric field of the X-ray detector 12 according to the first embodiment. The right side of Fig. 4 is the center side in the cone angle direction of the X-ray detector 12, and the left side of Fig. 4 is the end side.

[0073] Note that the number of high-voltage electrodes 121 and read electrodes 123 included in the detection module 124 of the X-ray detector 12 shown in Figure 4 is different from the example shown in Figure 2, but the detection modules 124 shown in both Figures 2 and 4 are just examples, and the numbers of high-voltage electrodes 121 and read electrodes 123 are not limited to these.

[0074] As shown in FIG. 4, in the X-ray detector 12 according to the first embodiment, the electric charges move obliquely in the same direction as the cone angle of the X-rays 100 due to the inclination of the direction of the electric field between the high-voltage electrodes 121a to 121g and the readout electrodes 123a to 123g.

[0075] For example, X-rays 100b incident on high-voltage electrode 121d are absorbed in region 1221 of semiconductor element 122. Then, X-rays 100b absorbed in region 1221 of semiconductor element 122 are converted into charges by semiconductor element 122. The charges converted from X-rays 100b move in a direction away from the center along the direction of the electric field and are read out by readout electrode 123c. In X-ray detector 12 of this embodiment, all charges based on X-rays 100b incident on high-voltage electrode 121d are read out by readout electrode 123c, regardless of the depth position in semiconductor element 122 at which the X-rays were absorbed.

[0076] Furthermore, all charges based on X-rays 100a incident on high-voltage electrode 121c are read out by read electrode 123b. All charges based on X-rays 100c incident on high-voltage electrode 121e are read out by read electrode 123d. That is, in the X-ray detector 12 of this embodiment, among the multiple high-voltage electrodes 121a to 121g included in the detection module 124, charges based on X-rays 100 incident on the same high-voltage electrode 121 are read out by the same read electrode 123. Furthermore, as shown in FIG. 4, X-rays 100 incident on the high-voltage electrode 121 are read out by read electrode 123 located at a position shifted away from the center position of the X-ray detector 12 in the cone angle direction (Z-axis direction) from the incident position on the high-voltage electrode 121. The shift between the incident position and read electrode 123 changes depending on the magnitude of the cone angle and the incident position. The read electrode 123 is placed at a position that takes this position shift into consideration. In FIG. 4, the read electrodes 123b to 123d correspond one-to-one to the high-voltage electrodes 121c to 121e, respectively, but this configuration is just an example, and the read electrodes 123b to 123d and the high-voltage electrodes 121c to 121e do not necessarily have to have a one-to-one relationship.

[0077] In other words, the projection data based on the charges read out by the readout electrode 123c is based on the X-rays 100b that entered the X-ray detector 12 from the position of the high-voltage electrode 121d. For the projection data based on the charges read out by the other readout electrodes 123, it is possible to uniquely identify the position of the high-voltage electrode 121 in the X-ray detector 12 from which the X-rays 100 entered.

[0078] Therefore, when the reconstruction processing function 443 of the processing circuitry 44 reconstructs the projection data, the reconstruction processing can be performed in accordance with the actual correspondence between the high-voltage electrodes 121a to 121g and the readout electrodes 123a to 123g.

[0079] Next, a flow of detecting the X-rays 100 in the X-ray CT apparatus 1 of this embodiment configured as above will be described.

[0080] 5 is a flowchart showing an example of the flow of detection of X-rays 100 in the X-ray CT apparatus 1 according to the first embodiment. The processing flow of this flowchart is common to both positioning imaging and main imaging. The processing of this flowchart is executed, for example, when a technician or the like operates the input interface 43 of the console device 40 to start imaging while the subject P is placed on the tabletop 33. In addition, the explanation of FIG. 5 will be given taking the configuration of the X-ray detector 12 explained in FIG. 2 as an example.

[0081] First, the potential control device 120 controls each of the high-voltage electrodes 121a-121e included in each of the plurality of detection modules 124 included in the X-ray detector 12 so that the potential of the high-voltage electrode 121 increases as the distance from the center in the cone angle direction increases among the plurality of high-voltage electrodes 121a-121e included in each of the plurality of detection modules 124 included in the X-ray detector 12. The potential control device 120 also controls the potential of the plurality of read electrodes 123a-123e included in each of the plurality of detection modules 124 included in the X-ray detector 12 (S1).

[0082] By controlling the potential in this way, the direction of the electric field between the high voltage electrodes 121a to 121e and the readout electrodes 123a to 123e becomes a direction that spreads from the center of the X-ray detector 12 toward both ends, similar to the cone angle of the X-rays 100.

[0083] The potentials of the multiple read electrodes 123a to 123e included in each of the multiple detection modules 124 are all equal positive potentials. Note that, since the potentials of the read electrodes 123 are all equal, the same potential may be maintained at all times without being controlled by the potential control device 120.

[0084] The X-ray tube 11 generates X-rays 100 by applying a high voltage and supplying a filament current from the X-ray high voltage device 14. The X-rays 100 generated at the tube focus in the X-ray tube 11 are shaped into a cone beam via, for example, a collimator 17, and are irradiated onto the subject P. The rotating frame 13 rotates around the subject P while holding the X-ray tube 11 and the X-ray detector 12 (S2).

[0085] X-rays 100 emitted from the X-ray tube 11 are incident on the X-ray detector 12. The semiconductor element 122 of the X-ray detector 12 converts the incident X-rays 100 into an electric charge (S3).

[0086] Each of the plurality of read electrodes 123a to 123e corresponding to the plurality of high voltage electrodes 121a to 121e reads out the electric charges converted from the X-rays 100 as an electric signal (S4).

[0087] Then, the DAS 18 amplifies the electrical signal read out by the readout electrode 123 of the X-ray detector 12, and then performs A / D conversion to convert the amplified signal into a digital signal (S5).

[0088] The DAS 18 transfers the digital signal to the console device 40 as detection data (S6). At this point, the processing of this flowchart ends. In this flowchart, pre-processing of the detection data and reconstruction processing, etc., executed by the console device 40 are not shown.

[0089] As described above, the X-ray detector 12 of this embodiment includes a plurality of read electrodes 123 arranged in the cone angle direction of the incident X-rays 100, a plurality of high-voltage electrodes 121 positioned closer to the incidence side of the X-rays 100 than the plurality of read electrodes 123 and facing the plurality of read electrodes 123, and a potential control device 120 that forms an electric field oriented based on the cone angle between the plurality of read electrodes 123 and the read electrodes 123. Therefore, the X-ray detector 12 of this embodiment can reduce the possibility that X-rays 100 incident from the same position are read out by different read electrodes 123, thereby mitigating a decrease in the spatial resolution of the X-ray detector 12 in the cone angle direction.

[0090] More specifically, according to the X-ray detector 12 of this embodiment, X-rays 100 incident from the same position are read out toward the same readout electrode 123. Therefore, when the projection data is reconstructed based on the detection data read out from the readout electrode 123, the incident position in the reconstruction theory can be made to coincide with the actual incident position, thereby reducing the degradation of the spatial resolution in the cone angle direction of the reconstructed CT image data.

[0091] Another method for reducing the degradation of spatial resolution in the cone angle direction is to arrange the detection module into smaller modules, with each module facing the X-ray incidence direction. In this case, each small module can be oriented in accordance with the cone angle direction. However, this structure can cause scattered rays due to the structure of the small modules, potentially degrading image quality. In contrast, the X-ray detector 12 of this embodiment can accommodate the X-ray detector 12 within the same plane while also addressing oblique X-ray incidence, thereby reducing the degradation of spatial resolution due to scattered rays compared to the comparative example.

[0092] Furthermore, the potential control device 120 of the X-ray detector 12 of this embodiment applies different voltages to the multiple high-voltage electrodes 121a-121e at each position along the cone angle direction, thereby generating an electric field oriented based on the cone angle. Therefore, according to the X-ray detector 12 of this embodiment, the distribution of the potentials of the multiple high-voltage electrodes 121a-121e can be adjusted, and the direction of the electric field between the multiple high-voltage electrodes 121a-121e and the multiple high-voltage electrodes 121a-121e can be changed according to the cone angle.

[0093] Furthermore, the method executed by the X-ray detector 12 of this embodiment includes a potential control step in which the potential control device 120 controls the potential of each of the multiple high-voltage electrodes 121a to 121e included in the X-ray detector 12 so that the potential becomes higher the further away from the center in the cone angle direction, and a readout step in which each of the multiple readout electrodes 123a to 123e corresponding to the multiple high-voltage electrodes 121a to 121e arranged in the cone angle direction of the X-rays 100 reads out charges converted from the X-rays 100. Therefore, according to the X-ray detector 12 of this embodiment, by each of the multiple readout electrodes 123a to 123e reading out charges converted from the X-rays 100 incident at the position of the corresponding high-voltage electrode 121a to 121e, it is possible to easily identify from which position in the cone angle direction the charges read out from each of the readout electrodes 123a to 123e are based the X-rays 100 incident.

[0094] In this embodiment, the potential control device 120 controls the potential of each of the multiple high-voltage electrodes 121 included in the X-ray detector 12, but the control entity is not limited to this. For example, the X-ray high-voltage device 14, the control device 15, or the processing circuitry 44 of the console device 40 may control the potential of each of the multiple high-voltage electrodes 121. For example, the system control function 441 of the processing circuitry 44 may have a function to control the potential of each of the multiple high-voltage electrodes 121.

[0095] The method for adjusting the potential distribution of the multiple high-voltage electrodes 121a-121e is not limited to voltage control by the potential control device 120. For example, resistors of different values ​​may be provided for each of the multiple high-voltage electrodes 121a-121e. In this case, the potential control device 120 does not need to individually control the multiple high-voltage electrodes 121a-121e. For example, the potential control device 120 simply applies a uniform voltage to the high-voltage electrodes 121a-121e. Alternatively, the X-ray detector 12 may not include the potential control device 120, and a power supply device may apply a uniform voltage to the high-voltage electrodes 121a-121e. In such a configuration, the potential control device 120 or the power supply device and the resistors provided for each of the multiple high-voltage electrodes 121a-121e are an example of an electric field forming unit.

[0096] (Second embodiment) In the first embodiment described above, the X-ray detector 12 includes a plurality of high-voltage electrodes 121a to 121e for each detection module 124. In contrast, in the second embodiment, the X-ray detector 12 includes a second electrode different from the high-voltage electrode located on the surface of the semiconductor element 122, thereby adjusting the direction of the electric field to a direction along the cone angle.

[0097] 6 is a diagram showing an example of the configuration of an X-ray detector 12 according to the second embodiment. As shown in FIG. 6, the X-ray detector 12 of this embodiment includes one high-voltage electrode 1121, one semiconductor element 122, multiple readout electrodes 123a to 123e, and one second electrode 125 per detection module 124. The X-ray detector 12 includes multiple detection modules 50 in the fan angle direction. The number of readout electrodes 123a to 123e and second electrodes 125 included in one detection module 124 is not limited to the example shown in FIG. 6. The high-voltage electrode 1121 may be referred to as a first electrode when distinguishing it from the second electrode 125.

[0098] In this embodiment, each detection module 124 includes one high-voltage electrode 1121. Therefore, the high-voltage electrode 1121 has a uniform negative potential in the cone angle direction. In this embodiment, the potential control device 120 simply applies a specified voltage to the high-voltage electrode 1121. Alternatively, the X-ray detector 12 may not include the potential control device 120, and a power supply device may apply a specified voltage to the high-voltage electrode 1121.

[0099] The second electrode 125 is an electrode having a negative potential, and is provided at a position overlapping with the high-voltage electrode 1121 in the incident direction of the X-rays 100 in at least a part of the region in the cone angle direction of the X-rays 100. The value of the potential of the second electrode 125 is not particularly limited, but is lower than the potential of the high-voltage electrode 1121. The high-voltage electrode 1121 and the second electrode 125 are examples of cathode electrodes in this embodiment.

[0100] In this embodiment, the partial area where the high-voltage electrode 1121 and the second electrode 125 overlap is the area near the center in the cone angle direction, as shown in Fig. 6. Therefore, as shown in the graph in Fig. 6, the potential of the cathode electrode near the center in the cone angle direction is lower than the potential at both ends in the cone angle direction.

[0101] Therefore, also in this embodiment, due to the potential difference in the cone angle direction, the direction of the electric field between the high-voltage electrode 1121 and the plurality of read electrodes 123a to 123e is inclined so as to widen toward both ends, similar to the cone angle of the X-rays 100. In other words, also in this embodiment, X-rays 100 incident from the same position on the high-voltage electrode 1121 are read by the same read electrode 123, regardless of the depth position in the semiconductor element 122 at which they are absorbed.

[0102] As described above, the X-ray detector 12 of this embodiment can achieve the same effect as the first embodiment by providing a plurality of cathode electrodes in at least a part of the region in the cone angle direction in the incident direction of the X-rays 100. Furthermore, the X-ray detector 12 of this embodiment does not need to provide a plurality of high-voltage electrodes for each detection module 124, which can reduce an increase in the number of parts.

[0103] (Modification of the second embodiment) Furthermore, the overlapping areas of the high-voltage electrode 1121 and the second electrode 125 may be at both ends in the cone angle direction. In this case, the second electrode 125 has, for example, a positive potential. Because the second electrode 125 makes the potential at both ends in the cone angle direction higher than that at the center, the direction of the electric field between the high-voltage electrode 1121 and the plurality of read electrodes 123a to 123e is tilted to widen toward both ends, similar to the cone angle of the X-rays 100.

[0104] Furthermore, the number of second electrodes 125 is not limited to one or two, but may be three or more.

[0105] (Third embodiment) In the second embodiment described above, the second electrode 125 is provided so as to overlap the high-voltage electrode 1121. In contrast, in this third embodiment, the X-ray detector 12 includes another electrode at a position that does not overlap the high-voltage electrode 1121.

[0106] Fig. 7 is a diagram showing an example of the configuration of an X-ray detector 12 according to the third embodiment. As shown in Fig. 7, the X-ray detector 12 of this embodiment includes, for each detection module 124, one high-voltage electrode 1121, one semiconductor element 122, multiple read electrodes 123a to 123e, one third electrode 126, and one fourth electrode 127. The X-ray detector 12 includes multiple detection modules 50 arranged in the fan angle direction.

[0107] The number of read electrodes 123a to 123e included in one detection module 124 is not limited to the example shown in Fig. 6. In Fig. 2, the X-ray detector 12 has two additional electrodes, the third electrode 126 and the fourth electrode 127, but the number of additional electrodes is not limited to two. For example, the number of additional electrodes is one or more.

[0108] The third electrode 126 and the fourth electrode 127 are provided at positions that do not overlap with the high voltage electrode 1121 and the read electrodes 123a to 123e in the cone angle direction.

[0109] The third electrode 126 and the fourth electrode 127 have a positive potential. Therefore, as shown in the graph of Fig. 7, the potential of the high-voltage electrode 1121, the third electrode 126, and the fourth electrode 127 near the center in the cone angle direction is lower than the potential at both ends in the cone angle direction. Therefore, the direction of the electric field between the high-voltage electrode 1121 and the read electrodes 123a to 123e is tilted as if pulled toward both ends.

[0110] With this configuration, also in this embodiment, due to the potential difference in the cone angle direction, the direction of the electric field between the high voltage electrode 1121 and the multiple read electrodes 123a to 123e has an inclination that widens toward both ends, similar to the cone angle of the X-rays 100.

[0111] As described above, according to the X-ray detector 12 of this embodiment, the third electrode 126 and the fourth electrode 127 are provided at positions that do not overlap with the high-voltage electrode 1121 and the readout electrodes 123a to 123e in the cone angle direction, thereby achieving the same effects as those of the first embodiment. Also, in the X-ray detector 12 of this embodiment, it is not necessary to provide multiple high-voltage electrodes for each detection module 124, so that an increase in the number of parts can be reduced.

[0112] (Fourth embodiment) In the second and third embodiments described above, the X-ray detector 12 was provided with a second electrode 125, a third electrode 126, or a fourth electrode 127 that was different from the high-voltage electrode 1121 located on the surface of the semiconductor element 122, but in this fourth embodiment, the direction of the electric field is adjusted by providing a dielectric between the high-voltage electrode 1121 and the semiconductor element 122.

[0113] Fig. 8 is a diagram showing an example of the configuration of an X-ray detector 12 according to the fourth embodiment. As shown in Fig. 8, the X-ray detector 12 of this embodiment includes, for each detection module 124, one high-voltage electrode 1121, one semiconductor element 122, multiple read electrodes 123a to 123e, and one dielectric 128. The X-ray detector 12 includes multiple detection modules 50 arranged in the fan angle direction.

[0114] The dielectric 128 has a shape that becomes thicker as it moves away from the center of the X-ray detector 12 in the cone angle direction. In the example shown in FIG. 8, the dielectric 128 has a wedge-shaped recess that is centered at the center of the X-ray detector 12 in the cone angle direction and becomes thicker symmetrically toward the ends. The dielectric 128 acts as a resistance to the electric field between the high-voltage electrode 1121 and the multiple read electrodes 123a to 123e, so the thicker the dielectric 128, the weaker the electric field becomes. Therefore, at the center of the X-ray detector 12 in the cone angle direction, charges that travel orthogonally from the high-voltage electrode 1121 to the multiple read electrodes 123c move obliquely away from the center as they approach the ends in the cone angle direction. In other words, the dielectric 128 changes the direction of the electric field based on the cone angle. In this embodiment, the potential control device 120 simply applies a specified voltage to the high-voltage electrode 1121. Alternatively, the X-ray detector 12 may not include the potential control device 120, and a power supply device may apply a specified voltage to the high-voltage electrode 1121. The potential control device 120 or the power supply device and the dielectric 128 are an example of an electric field forming unit in this embodiment. Alternatively, the formation of an electric field may include deformation of the electric field, and the dielectric 128 alone may be an example of an electric field forming unit in this embodiment.

[0115] With this configuration, also in this embodiment, the direction of the electric field between the high voltage electrode 1121 and the plurality of read electrodes 123a to 123e is inclined so as to widen toward both ends, similar to the cone angle of the X-rays 100.

[0116] As described above, the X-ray detector 12 of this embodiment has a dielectric 128 between the high-voltage electrode 1121 and the semiconductor element 122 that becomes thicker as it moves away from the center in the cone angle direction, and therefore can achieve the same effects as the first embodiment.

[0117] Furthermore, the X-ray detector 12 of this embodiment does not need to include multiple high-voltage electrodes 121a to 121e, the second electrode 125, the third electrode 126, or the fourth electrode 127, etc., so the high-voltage supply system can be a single system, which contributes to reducing the number of parts and simplifying control.

[0118] The shape of the dielectric 128 is not limited to the example shown in Fig. 8. Fig. 9 is a diagram showing another example of the configuration of the X-ray detector 12 according to the fourth embodiment. As shown in Fig. 9, the dielectric 1128 may have a shape like a concave lens with both surfaces concave in a hyperbolic shape. In this case, too, the dielectric 1128 has a shape that becomes thicker as it moves away from the center in the cone angle direction.

[0119] (Modification 1 of the first to fourth embodiments) In the above-described embodiments, the X-ray detector 12 provided in the X-ray CT apparatus 1 is given as an example of a direct conversion type X-ray detector, but the direct conversion type X-ray detector is not limited to this. For example, an FPD (Flat Panel Detector) may be used as an example of a direct conversion type X-ray detector.

[0120] (Modification 2 of the first to fourth embodiments) 2 and 6 to 9 in the above-described embodiments, the high-voltage electrodes 121a to 121e, 1121 are shown at the top and the read electrodes 123a to 123e are shown at the bottom, but the positional relationship between the high-voltage electrodes 121a to 121e, 1121 and the read electrodes 123a to 123e is not limited to this. For example, the read electrodes may be located at the top and the high-voltage electrodes may be located at the bottom.

[0121] The various data handled in this specification are typically digital data.

[0122] According to at least one of the embodiments described above, it is possible to reduce the degradation of the spatial resolution in the cone angle direction of the direct conversion type X-ray detector.

[0123] Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations of embodiments can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

[0124] With respect to the above embodiment, the following supplementary notes are disclosed as one aspect and optional features of the invention.

[0125] (Appendix 1) a plurality of anode electrodes arranged in the cone angle direction of the incident X-rays; at least one cathode electrode located on the X-ray incident side of the plurality of anode electrodes and facing the plurality of anode electrodes; an electric field forming unit that forms an electric field between the plurality of anode electrodes and the cathode electrode in a direction based on a cone angle of the X-rays; A direct conversion X-ray detector comprising:

[0126] (Appendix 2) The electric field forming unit of the direct conversion type X-ray detector may apply a different voltage to each position along the cone angle direction to generate an electric field in a direction based on the cone angle.

[0127] (Appendix 3) The direct conversion type X-ray detector includes a plurality of the cathode electrodes arranged along the cone angle direction.

[0128] (Appendix 4) The direct conversion type X-ray detector includes a plurality of cathode electrodes in the incident direction of the X-rays in at least a part of the region in the cone angle direction.

[0129] (Appendix 5) In the direct conversion type X-ray detector, the partial region is a region near the center in the cone angle direction or both ends in the cone angle direction.

[0130] (Appendix 6) The direct conversion X-ray detector has one or more other electrodes provided at positions that do not overlap with the cathode electrode and the plurality of anode electrodes in the cone angle direction.

[0131] (Appendix 7) the direct conversion type X-ray detector further includes a semiconductor element between the cathode electrode and the plurality of anode electrodes that converts incident X-rays into electric charges; The electric field forming portion is a dielectric material located between the cathode electrode and the semiconductor element, and has a shape that becomes thicker as it moves away from the center in the cone angle direction.

[0132] (Appendix 8) a potential control step of controlling the potential of each of a plurality of cathode electrodes arranged in a cone angle direction of an X-ray included in the direct conversion X-ray detector so that the potential increases with increasing distance from the center in the cone angle direction; a readout step in which each of a plurality of anode electrodes arranged in a cone angle direction of the X-rays and corresponding to the plurality of cathode electrodes reads out electric charges converted from the X-rays; A method comprising:

[0133] (Appendix 9) an X-ray generating unit that generates X-rays; a direct conversion X-ray detector; The direct conversion type X-ray detector comprises: a plurality of anode electrodes arranged in a cone angle direction of the incident X-rays; at least one cathode electrode located on the X-ray incident side of the plurality of anode electrodes and facing the plurality of anode electrodes; and an electric field forming unit that forms an electric field between the plurality of anode electrodes and the cathode electrode in a direction based on the cone angle of the X-rays. X-ray computed tomography equipment. [Explanation of symbols]

[0134] 1 X-ray CT device 11 X-ray tube 12 X-ray detector 18 DAS 40 Console device 41 memory 42 Display 43 Input Interface 44 Processing circuit 100 X-rays 120 Potential control device 121, 121a~121g, 1121 High voltage electrodes 122 Semiconductor elements 123,123a~123g readout electrode 124 Detection Module 125 2nd electrode 126 3rd electrode 127 4th electrode 128,1128 Dielectric 441 System Control Functions 442 Pre-processing function 443 Reconstruction Processing Function 444 Scan Control Function 445 Image Processing Function 446 Display Control Function P Subject

Claims

1. a plurality of anode electrodes arranged in a cone angle direction of the incident X-rays; at least one cathode electrode located on an X-ray incident side of the plurality of anode electrodes and facing the plurality of anode electrodes; an electric field forming unit that forms an electric field between the plurality of anode electrodes and the cathode electrode in a direction based on a cone angle of the X-rays; A direct conversion X-ray detector comprising:

2. the electric field forming unit applies a different voltage to each position along the cone angle direction to generate an electric field oriented based on the cone angle.

2. The direct conversion X-ray detector of claim 1.

3. a plurality of the cathode electrodes arranged along the cone angle direction; 3. The direct conversion X-ray detector according to claim 2.

4. a plurality of cathode electrodes in an incident direction of the X-rays in at least a part of the region in the cone angle direction; 3. The direct conversion X-ray detector according to claim 2.

5. The partial region is a region near the center in the cone angle direction or both ends in the cone angle direction.

5. The direct conversion X-ray detector according to claim 4.

6. providing one or more other electrodes at positions that do not overlap the cathode electrode and the plurality of anode electrodes in the cone angle direction; 2. The direct conversion X-ray detector of claim 1.

7. a semiconductor element between the cathode electrode and the plurality of anode electrodes for converting incident X-rays into electric charges; the electric field forming portion is a dielectric material located between the cathode electrode and the semiconductor element, the dielectric material having a shape that becomes thicker as it moves away from the center in the cone angle direction.

2. The direct conversion X-ray detector of claim 1.

8. a potential control step of controlling the potential of each of a plurality of cathode electrodes arranged in a cone angle direction of an X-ray included in the direct conversion X-ray detector so that the potential increases with increasing distance from the center of the cone angle direction; a readout step in which charges converted from the X-rays are read out by each of a plurality of anode electrodes corresponding to the plurality of cathode electrodes, the anode electrodes being arranged in a cone angle direction of the X-rays; A method comprising:

9. an X-ray generating unit that generates X-rays; a direct conversion X-ray detector; The direct conversion X-ray detector comprises: a plurality of anode electrodes arranged in a cone angle direction of the incident X-rays; at least one cathode electrode located on an X-ray incident side of the plurality of anode electrodes and facing the plurality of anode electrodes; an electric field forming unit that forms an electric field between the plurality of anode electrodes and the cathode electrode in a direction based on a cone angle of the X-rays, X-ray computed tomography equipment.

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