Detection element determination method

Abstract

To reduce cost relating to implementation of a correcting X-ray detector.SOLUTION: A correcting X-ray detector includes: multiple detection elements for detecting an X-ray; an acquisition unit; and a determination unit. The acquisition unit acquires multiple output values corresponding to the multiple detection elements respectively. The determination unit determines a detection element to be used for generating correction data on the basis of multiple output values.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The embodiments disclosed in this specification and the drawings relate to a corrective X-ray detector, an X-ray CT apparatus, and a detection element determination method. [Background technology]

[0002] In recent years, in X-ray CT (Computed Tomography) devices, a technique has been known in which, in addition to an X-ray detector for imaging, a correction X-ray detector is used to correct the variation of X-rays emitted from an X-ray tube. Generally, such a correction X-ray detector requires a dedicated design, even though only one is needed for one X-ray CT device, which is problematic in terms of cost and development effort. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-140975 A [Patent Document 2] JP 2013-140962 A [Patent Document 3] JP 2019-113392 A Summary of the Invention [Problem to be solved by the invention]

[0004] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to reduce the cost associated with mounting the corrective 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 later can also be positioned as other problems. [Means for solving the problem]

[0005] A correction X-ray detector according to an embodiment includes a plurality of detection elements for detecting X-rays, an acquisition unit, and a determination unit. The acquisition unit acquires a plurality of output values ​​corresponding to the plurality of detection elements. The determination unit determines a detection element to be used for generating correction data based on the plurality of output values. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of an X-ray CT apparatus according to the first embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of the configuration of the corrective X-ray detector according to the first embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of a scintillator array and a detection element array included in the corrective X-ray detector according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing an example of detection element determination performed by the determination function according to the first embodiment. [Diagram 5] FIG. 5 is a flowchart showing the processing procedure of the processing performed by the X-ray CT apparatus according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing an example of the configuration of a corrective X-ray detector according to the second embodiment. [Figure 7] FIG. 7 is a diagram showing an example of a scintillator array, a detection element array, and a collimator included in the corrective X-ray detector according to the second embodiment. [Figure 8] FIG. 8 is a diagram showing an example of detection element determination performed by the determination function according to the second embodiment. [Figure 9] FIG. 9 is a flowchart showing the processing procedure of the processing performed by the X-ray CT apparatus according to the second embodiment. [Figure 10] FIG. 10 is a diagram showing an example of the configuration of a corrective X-ray detector and a DAS according to the third embodiment. [Figure 11] FIG. 11 is a diagram showing an example of the configuration of a corrective X-ray detector and a processing circuit of a console device according to the fourth embodiment. [Figure 12]FIG. 12 is a flowchart showing a detection element determination method according to the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, with reference to the drawings, embodiments of the corrective X-ray detector, the X-ray CT device, and the detection element determination method disclosed in the present application will be described. Here, the configurations shown in the drawings are schematic, and the dimensions of each component shown in the drawings and the dimensional ratios between the components may differ from the actual ones. Furthermore, the dimensions of the same component and the dimensional ratios between the components may be shown differently between the drawings.

[0008] (First embodiment) FIG. 1 is a diagram showing an example of the configuration of an X-ray CT apparatus according to the first embodiment.

[0009] For example, as shown in FIG. 1, an X-ray CT apparatus 1 according to this embodiment includes a gantry device 10, a bed device 30, and a console device 40.

[0010] In this embodiment, the rotation axis of the rotating frame 13 in the 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 direction that is perpendicular to the Z-axis direction and horizontal to the floor surface is defined as the X-axis direction. The axis direction that is perpendicular to the Z-axis direction and perpendicular to the floor surface is defined as the Y-axis direction.

[0011] The gantry device 10 is a device that irradiates X-rays onto a subject P, such as a patient, detects the X-rays that have passed through the subject P, and outputs the X-rays to a console device 40. Specifically, the gantry device 10 has an X-ray tube 11, an X-ray detector 12, a rotating frame 13, an X-ray high voltage device 14, a control device 15, a wedge 16, an X-ray aperture 17, and a DAS (Data Acquisition System) 18. For convenience of explanation, the gantry device 10 viewed from the X-axis direction and the Z-axis direction are shown in FIG. 1, but the X-ray CT device 1 has one gantry device 10.

[0012] X-ray tube 11 is a vacuum tube having a cathode (filament) that generates thermoelectrons and an anode (target) that generates X-rays upon collision with the thermoelectrons. Specifically, X-ray tube 11 generates X-rays by irradiating thermoelectrons from the cathode to the anode upon application of high voltage from X-ray high voltage device 14. For example, X-ray tube 11 is a rotating anode type X-ray tube that generates X-rays by irradiating a rotating anode with thermoelectrons.

[0013] The X-ray detector 12 has a plurality of detection elements that detect X-rays irradiated from the X-ray tube 11 and passing through the subject P, and each detection element outputs an electrical signal corresponding to the detected X-ray dose to the DAS 18. Specifically, the X-ray detector 12 has a plurality of detection element rows in which a plurality of detection elements are arranged in a channel direction along the circumferential direction of an arc centered on the focus of the X-ray tube 11, and has a structure in which each detection element row is arranged in a slice direction (also called the row direction).

[0014] For example, the X-ray detector 12 is an indirect conversion type detector having a collimator, a scintillator array, and a detector array. The collimator is arranged on the X-ray incident side of the scintillator array, and has an X-ray shielding plate that absorbs scattered X-rays. For example, the collimator is a one-dimensional collimator or a two-dimensional collimator. The collimator is also called a grid. The scintillator array is arranged on the X-ray incident side of the detector array, and has a plurality of scintillators. Each scintillator has a scintillator crystal that outputs light with a photon amount corresponding to the dose of the incident X-ray. The detector array has a plurality of detector elements, and each detector element converts light output from the scintillator into an electric signal corresponding to the amount of light. For example, the detector array is configured by arranging a plurality of subarrays in the channel direction and the slice direction, in which a plurality of detector elements are arranged one-dimensionally (n rows x 1 column) or two-dimensionally (n rows x m columns) on the same plane. Furthermore, for example, the detection element is a light receiving element such as a photodiode (PD) or a photomultiplier tube (PMT).

[0015] The rotating frame 13 is an annular frame that rotates the X-ray tube 11 and the X-ray detector 12 around a rotation axis (Z-axis). Specifically, the rotating frame 13 is supported by a fixed frame (not shown) so as to be rotatable around the rotation axis while supporting the X-ray tube 11 and the X-ray detector 12 facing each other. The rotating frame 13 rotates around the rotation axis under the control of the control device 15, thereby rotating the X-ray tube 11 and the X-ray detector 12 around the rotation axis. The rotating frame 13 further comprises and supports an X-ray high voltage device 14 and a DAS 18 in addition to the X-ray tube 11 and the X-ray detector 12.

[0016] The X-ray high voltage device 14 has electric circuits such as a transformer and a rectifier, and includes a high voltage generator having a function of generating a high voltage to be applied to the X-ray tube 11, and an X-ray control device that controls the output voltage according to the X-ray output irradiated 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 within the gantry device 10, or may be provided on a fixed frame (not shown) that rotatably supports the rotating frame 13.

[0017] The wedge 16 is a filter for adjusting the dose of X-rays irradiated from the X-ray tube 11. Specifically, the wedge 16 is a filter that transmits and attenuates the X-rays irradiated from the X-ray tube 11 so that the X-rays irradiated from the X-ray tube 11 to the subject P have a predetermined distribution. For example, the wedge 16 is a filter made of processed aluminum so as to have a predetermined target angle and a predetermined thickness. The wedge 16 is also called a wedge filter or a bow-tie filter.

[0018] The X-ray aperture 17 includes a lead plate or the like for narrowing down the irradiation range of the X-rays transmitted through the wedge 16, and a slit is formed by combining a plurality of lead plates or the like.

[0019] The DAS 18 is a processing circuit that generates detection data based on an electrical signal output from each detection element of the X-ray detector 12. Specifically, the DAS 18 generates detection data by amplifying an electrical signal output from each detection element of the X-ray detector 12 and converting the amplified electrical signal from an analog signal to a digital signal. Here, the detection data generated by the DAS 18 is transmitted from a transmitter having a light emitting diode (LED) provided on the rotating frame 13 to a receiver having a photodiode provided on a non-rotating part (e.g., a support frame, etc.) of the gantry 10 by optical communication, and is then transferred to the console device 40. Note that the method of transmitting the detection data from the rotating frame 13 to the non-rotating part of the gantry 10 is not limited to optical communication, and any method of non-contact data transmission may be adopted.

[0020] The control device 15 has a driving mechanism such as a motor and an actuator, and a processing circuit for controlling the driving mechanism. The control device 15 has a function of receiving an input signal from an input interface 43 (described later) attached to the console device 40 or the gantry device 10 and controlling the operation of the gantry device 10 and the bed device 30. For example, the control device 15 receives an input signal and controls the rotation of the rotating frame 13, the tilt of the gantry device 10, and the operation of the bed device 30 and the tabletop 33. The control of tilting the gantry device 10 is 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 by the input interface 43 attached to the gantry device 10. The control device 15 may be provided in the gantry device 10 or in the console device 40.

[0021] 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 plate 33, and a support frame 34. The base 31 is a housing that supports the support frame 34 so that it can move in the vertical direction. The bed driving device 32 is a motor or actuator that moves the top plate 33, on which the subject P is placed, in the longitudinal direction of the top plate 33. The top plate 33, which is provided on the upper surface of the support frame 34, is a plate on which the subject P is placed. Note that the bed driving device 32 may move the support frame 34 in the longitudinal direction of the top plate 33 in addition to the top plate 33.

[0022] The console device 40 is a device that accepts operations of the X-ray CT apparatus 1 by an operator and reconstructs CT image data using detection data collected by the gantry device 10. The console device 40 has a memory 41, a display 42, an input interface 43, and a processing circuit 44. Note that, although an example in which the console device 40 and the gantry device 10 are separate entities will be described here, the gantry device 10 may include the console device 40 or some of the components of the console device 40.

[0023] The memory 41 is realized by, for example, a semiconductor memory element such as a RAM (Random Access Memory), a flash memory, a hard disk, an optical disk, etc. The memory 41 stores, for example, projection data and CT image data.

[0024] 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 an operator, and the like. For example, the display 42 is a liquid crystal display or a CRT (Cathode Ray Tube) display. Note that, for example, the display 42 may be provided on the gantry device 10. Also, for example, 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.

[0025] The input interface 43 receives various input operations from an operator, converts the received input operations into electrical signals, and outputs the electrical signals to the processing circuit 44. For example, the input interface 43 receives from the operator collection conditions for collecting projection data, reconstruction conditions for reconstructing CT image data, image processing conditions for generating post-processed images from CT images, and the like. For example, the input interface 43 is realized by a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touchpad for performing input operations by touching the operation surface, a touchscreen in which a display screen and a touchpad are integrated, a non-contact input circuit using an optical sensor, a voice input circuit, and the like. For example, the input interface 43 may be provided in the gantry device 10. For example, the input interface 43 may be configured by a tablet terminal or the like capable of wireless communication with the console device 40 main body. In addition, the input interface 43 is not limited to only those having physical operation parts such as a mouse and a keyboard. 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 console device 40 and outputs this electrical signal to the processing circuit 44.

[0026] The processing circuitry 44 controls the overall operation of the X-ray CT apparatus 1. For example, the processing circuitry 44 has a control function 441, a pre-processing function 442, a reconstruction processing function 443, an image processing function 444, and a display control function 445.

[0027] The control function 441 controls each part of the X-ray CT device 1 based on an input operation received from an operator via the input interface 43. For example, the control function 441 controls the CT scan by controlling the X-ray high voltage device 14, the control device 15, and the DAS 18. The control function 441 also controls the generation and display of CT image data by controlling the pre-processing function 442, the reconstruction processing function 443, the image processing function 444, and the display control function 445.

[0028] The pre-processing function 442 generates projection data by performing pre-processing such as logarithmic conversion processing, offset correction processing, inter-channel sensitivity correction processing, beam hardening correction, etc. on the detection data output from the DAS 18. Note that the data before pre-processing (detection data) and the data after pre-processing may be collectively referred to as projection data.

[0029] 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, and generates CT image data (reconstructed image data).

[0030] The image processing function 444 converts the CT image data generated by the reconstruction processing function 443 into cross-sectional image data of an arbitrary cross section, rendering image data of an arbitrary viewpoint direction, etc. Specifically, the image processing function 444 performs known three-dimensional image processing on the CT image data based on an input operation received from an operator via the input interface 43, thereby converting the data into tomographic image data of an arbitrary cross section, rendering image data of an arbitrary viewpoint direction, etc. For example, the three-dimensional image processing referred to here is volume rendering, surface rendering, image value projection processing, MPR (Multi-Planar Reconstruction) processing, CPR (Curved MPR) processing, etc. Note that the three-dimensional image processing may be performed directly by the reconstruction processing function 443.

[0031] The display control function 445 causes the display 42 to display images based on various image data generated by the reconstruction processing function 443 and the image processing function 444. For example, the display control function 445 causes the display 42 to display a CT image based on CT image data, a cross-sectional image based on cross-sectional image data of an arbitrary cross section, a rendering image of an arbitrary viewpoint direction based on rendering image data of an arbitrary viewpoint direction, and the like. Also, for example, the display control function 445 causes the display 42 to display an image for displaying an operation screen.

[0032] Here, for example, the processing circuitry 44 is realized by a processor. In this case, the processing functions possessed by the processing circuitry 44 are stored in the memory 41 in the form of programs executable by a computer. Then, the processing circuitry 44 realizes the processing functions corresponding to each program by reading each program from the memory 41 and executing it. In other words, the processing circuitry 44 has each processing function shown in the processing circuitry 44 in FIG. 1 in a state where each program is read.

[0033] The above describes the overall configuration of the X-ray CT apparatus 1 according to this embodiment. With this configuration, the X-ray CT apparatus 1 according to this embodiment includes the corrective X-ray detector 100 for correcting the X-rays irradiated from the X-ray tube 11 in addition to the X-ray detector 12 for imaging.

[0034] Here, the corrective X-ray detector 100 detects X-rays irradiated from the X-ray tube 11, and generates correction data for correcting fluctuations in the X-rays.

[0035] However, generally, even though only one such corrective X-ray detector is needed per X-ray CT scanner, a dedicated design is required, which poses problems in terms of cost and development effort.

[0036] For this reason, the X-ray CT apparatus 1 according to this embodiment is configured to enable the cost associated with mounting the corrective X-ray detector 100 to be reduced.

[0037] Specifically, the correction X-ray detector 100 includes a plurality of detection elements that detect X-rays, an acquisition unit that acquires a plurality of output values ​​corresponding to each of the plurality of detection elements, and a determination unit that determines the detection elements to be used for generating correction data based on the plurality of output values.

[0038] According to this configuration, when a defective detection element is included among the multiple detection elements, correction data can be generated using detection elements other than the defective detection element. As a result, for example, multiple detection elements that were manufactured for use in the X-ray detector 12 for imaging but became unusable because they included a defective detection element can be diverted to the correction X-ray detector 100, and the correction X-ray detector 100 can be manufactured at low cost. Therefore, according to this embodiment, the cost associated with mounting the correction X-ray detector 100 can be reduced.

[0039] Hereinafter, a detailed description will be given of the corrective X-ray detector 100 and the X-ray CT apparatus 1 according to this embodiment. Note that in this embodiment, an example will be described in which the corrective X-ray detector 100 has one channel.

[0040] FIG. 2 is a diagram showing an example of the configuration of the corrective X-ray detector 100 according to the first embodiment.

[0041] 2, the corrective X-ray detector 100 is configured separately from the X-ray detector 12 for imaging, and is fixed to a rotating frame 13 in the gantry 10 by a support member (not shown) such as a rigid frame. Here, the corrective X-ray detector 100 is provided between the X-ray tube 11 and the wedge 16 so as not to enter the imaging area using the X-ray detector 12. This prevents the X-rays incident on the corrective X-ray detector 100 from being changed by the wedge 16 or the X-ray aperture 17. The corrective X-ray detector 100 may be configured integrally with the wedge 16 or the X-ray aperture 17.

[0042] The corrective X-ray detector 100 detects the X-rays irradiated from the X-ray tube 11 and generates correction data for correcting the fluctuation of the X-rays. The correction data generated by the corrective X-ray detector 100 is transferred to the console device 40 via the DAS 18 and used to correct the fluctuation of the dose of the X-rays irradiated from the X-ray tube 11.

[0043] Specifically, the corrective X-ray detector 100 has a scintillator array 110, a detector element array 120, and a corrective DAS .

[0044] FIG. 3 is a diagram showing an example of the scintillator array 110 and the detection element array 120 included in the corrective X-ray detector 100 according to the first embodiment.

[0045] 3, the scintillator array 110 is disposed on the X-ray incident surface of the detector array 120, and has a plurality of scintillators 111. Each scintillator 111 has a scintillator crystal that outputs light with an amount of photons corresponding to the dose of the incident X-rays.

[0046] Furthermore, the detection element array 120 has a plurality of detection elements 121, and each detection element 121 converts light output from the scintillator 111 into an electrical signal according to the amount of light. For example, the detection element array 120 is configured by arranging a plurality of detection elements one-dimensionally (n rows×1 column) or two-dimensionally (n rows×m columns) on the same plane. For example, the detection elements are light receiving elements such as PDs and PMTs.

[0047] Here, for example, the multiple detection elements 121 included in the detection element array 120 are fabricated for use in the X-ray detector 12 for imaging. For example, as the detection element array 120, a subarray of detection elements fabricated for use in the X-ray detector 12 for imaging is used.

[0048] In this embodiment, one channel C is associated with at least some of the detection elements 121 included in the detection element array 120. For example, one channel C is associated with all of the detection elements 121 included in the detection element array 120.

[0049] 3, the number of scintillators 111 included in the scintillator array 110 is the same as the number of detector elements 121 included in the detector array 120, but the number of scintillators 111 and the number of detector elements 121 may or may not match. For example, the scintillator array 110 may be configured such that one scintillator 111 is disposed on one detector element 121, or such that one scintillator 111 is disposed on a plurality of detector elements 121. Also, for example, the scintillator array 110 may be configured to cover all detector elements 121 included in the detector array 120, or may be configured to cover only the detector elements 121 associated with the channel C.

[0050] 2, the correction DAS 130 is a processing circuit that generates correction data based on the electrical signals output from each detection element 121 of the detection element array 120. Specifically, the correction DAS 130 generates the correction data by amplifying the electrical signals output from each detection element 121 of the detection element array 120 and converting the amplified electrical signals from analog signals to digital signals.

[0051] Specifically, the correction DAS 130 has an acquisition function 131, a determination function 132, and a generation function 133. Here, the acquisition function 131 is an example of an acquisition unit. The determination function 132 is an example of a determination unit. The generation function 133 is an example of a generation unit.

[0052] The acquisition function 131 acquires a plurality of output values ​​corresponding to each of the plurality of detector elements 121 included in the detector element array 120 .

[0053] Specifically, the acquisition function 131 acquires the output value of the electrical signal output from each detection element 121 of the detection element array 120 when X-rays are irradiated from the X-ray tube 11 to the scintillator array 110 of the corrective X-ray detector 100.

[0054] The determination function 132 determines, based on the multiple output values ​​acquired by the acquisition function 131, the detection elements to be used for generating the correction data.

[0055] Specifically, the determination function 132 performs threshold processing on the multiple output values ​​acquired by the acquisition function 131, and determines the detection elements to be used for generating the correction data based on the result of the threshold processing.

[0056] At this time, the determination function 132 determines the detection element to be used for generating the correction data from among the detection elements 121 to which the channel is associated.

[0057] FIG. 4 is a diagram showing an example of detection element determination performed by the determination function 132 according to the first embodiment.

[0058] For example, as shown in Fig. 4, the determination function 132 detects a detection element 121 having an output value less than an expected value E among the detection elements 121 associated with the channel C. Then, the determination function 132 determines a detection element 121 other than the detected detection element 121 as a detection element to be used for generating correction data. Note that in the example shown in Fig. 4, the detection element 121 determined as the detection element to be used for generating correction data is hatched with diagonal lines.

[0059] Here, the expected value E is a threshold value for determining whether or not the detection element 121 can sufficiently detect X-rays. For example, the expected value E is set in advance based on actual measurements, standard values, etc., when the corrective X-ray detector 100 is installed at an installation site such as a hospital.

[0060] Thereby, when the detection element array 120 includes a defective detection element 121 whose output value is less than the expected value E, the detection element 121 is excluded from the detection elements used for generating the correction data. As a result, when a defective detection element is included among the multiple detection elements 121, the correction data can be generated using the detection elements 121 other than the defective detection element 121.

[0061] Returning to FIG. 2, the generation function 133 generates correction data based on the detection element determined by the determination function 132 .

[0062] Specifically, the generating function 133 generates the correction data by using the sum of the output values ​​of the detection elements determined by the determining function 132. Alternatively, for example, the generating function 133 may generate the correction data by using the average value of the output values ​​of the detection elements, or may generate the correction data by using the maximum value.

[0063] In this manner, the correction data generated by the generation function 133 is transferred to the console device 40 via the DAS 18 and stored in the memory 41. The correction data stored in the memory 41 is then read out by the processing circuit 44 and used to correct fluctuations in the dose of X-rays irradiated from the X-ray tube 11.

[0064] Here, for example, the correction DAS 130 is realized by a processor. In this case, each processing function of the correction DAS 130 is stored in a memory (not shown) in the form of a program executable by a computer. Then, the correction DAS 130 realizes the processing function corresponding to each program by reading each program from the memory and executing it. In other words, the correction DAS 130 has each processing function shown in the correction DAS 130 in FIG. 2 when each program is read.

[0065] FIG. 5 is a flowchart showing the procedure of processing performed by the X-ray CT apparatus 1 according to the first embodiment.

[0066] The process described below is executed, for example, when the X-ray CT apparatus 1 is installed at an installation site such as a hospital, or when the X-ray CT apparatus 1 is adjusted.

[0067] 5, first, when the processing circuitry 44 receives a start instruction from the operator via the input interface 43 (step S101, Yes), it controls the X-ray high voltage device 14 to irradiate X-rays from the X-ray tube 11 to the scintillator array 110 of the corrective X-ray detector 200 (step S102). This step corresponds to the control function 441. In this step, for example, the processing circuitry 44 reads out a program corresponding to the control function 441 from the memory 41 and executes it, thereby realizing the control function 441.

[0068] Next, the correction DAS 130 acquires a plurality of output values ​​corresponding to the plurality of detection elements 121 included in the detection element array 120 (step S103). This step corresponds to the acquisition function 131. In this step, for example, the correction DAS 130 reads out a program corresponding to the acquisition function 131 from a memory and executes it, thereby realizing the acquisition function 131.

[0069] Next, the correction DAS 130 detects detection elements 121 with output values ​​less than an expected value among the detection elements 121 associated with the channels based on the acquired multiple output values ​​(step S104). Then, the correction DAS 130 determines detection elements 121 other than the detected detection elements 121 as detection elements to be used for generating correction data (step S105). These steps correspond to the determination function 132. In these steps, for example, the correction DAS 130 reads out a program corresponding to the determination function 132 from a memory and executes it, thereby realizing the determination function 132.

[0070] Next, the correction DAS 130 generates correction data based on the determined detection elements (step S106). This step corresponds to the generating function 133. In this step, for example, the correction DAS 130 reads out a program corresponding to the generating function 133 from a memory and executes it, thereby realizing the generating function 133.

[0071] As described above, in the first embodiment, the correction X-ray detector 100 includes a plurality of detection elements 121 that detect X-rays. Then, the acquisition function 131 of the correction DAS 130 acquires a plurality of output values ​​corresponding to each of the plurality of detection elements 121, and the determination function 132 determines the detection element to be used for generating correction data based on the plurality of output values.

[0072] According to such a configuration, as described above, when a defective detection element is included among the multiple detection elements 121, correction data can be generated using detection elements 121 other than the defective detection element 121. As a result, for example, multiple detection elements that were manufactured for use in the X-ray detector 12 for imaging but became unusable because they included a defective detection element can be diverted to the correction X-ray detector 100, and the correction X-ray detector 100 can be manufactured at low cost. Therefore, according to this embodiment, the cost associated with mounting the correction X-ray detector 100 can be reduced.

[0073] (Modification of the first embodiment) In the above-described first embodiment, the determination function 132 determines the detection element using the expected value of the output value, but the embodiment is not limited to this. For example, the determination function 132 may determine the detection element by further using the upper limit value of the output value.

[0074] In that case, for example, the determination function 132 detects, among the detection elements 121 to which the channel is associated, a detection element 121 whose output value is less than the expected value or exceeds an upper limit value greater than the expected value, and determines a detection element 121 other than the detected detection element 121 as the detection element to be used for generating correction data.

[0075] Here, the upper limit value is a threshold value for detecting detection elements 121 that cause an error in signal processing because the output value is too large in the corrective X-ray detector 100. For example, the upper limit value is set in advance based on actual measurement values, standard values, etc., when the corrective X-ray detector 100 is installed at an installation site such as a hospital.

[0076] As a result, if the detector array 120 includes a detector element 121 whose output value will result in an error in signal processing, the detector element 121 is further excluded from the detector elements used to generate correction data.

[0077] According to such a configuration, by using only the detection elements 121 whose output values ​​do not result in errors in signal processing, it becomes possible to generate correction data with higher accuracy.

[0078] Second embodiment In the above-mentioned first embodiment, an example in which the correction X-ray detector has one channel has been described, but the embodiment is not limited thereto. For example, the correction X-ray detector may have multiple channels. Therefore, in the following, as a second embodiment, an example in which the correction X-ray detector has multiple channels will be described. In addition, in the following, the differences from the first embodiment will be mainly described, and the components common to the first embodiment will be denoted by the same reference numerals and detailed description will be omitted.

[0079] FIG. 6 is a diagram showing an example of the configuration of a corrective X-ray detector 200 according to the second embodiment.

[0080] 6, the corrective X-ray detector 200 is configured separately from the X-ray detector 12 for imaging, and is fixed to the rotating frame 13 in the gantry 10 by a support member such as a rigid frame (not shown). Here, the corrective X-ray detector 200 is provided between the X-ray tube 11 and the wedge 16 so as not to enter the imaging area using the X-ray detector 12. This prevents the X-rays incident on the corrective X-ray detector 200 from being changed by the wedge 16 or the X-ray aperture 17. The corrective X-ray detector 200 may be configured integrally with the wedge 16 or the X-ray aperture 17.

[0081] The corrective X-ray detector 200 detects the X-rays irradiated from the X-ray tube 11, and generates correction data for each channel to correct the fluctuation of the X-rays. The correction data generated by the corrective X-ray detector 200 is transferred to the console device 40 via the DAS 18 for each channel, and is used to correct the fluctuation of the dose and energy spectrum of the X-rays irradiated from the X-ray tube 11.

[0082] Specifically, the corrective X-ray detector 200 has a scintillator array 110, a detector element array 120, a collimator 240, and a corrective DAS 230. Here, the scintillator array 110 and the detector element array 120 each have the configuration described in the first embodiment.

[0083] FIG. 7 is a diagram showing an example of a scintillator array 110, a detection element array 120, and a collimator 240 included in a corrective X-ray detector 200 according to the second embodiment.

[0084] For example, as shown in FIG. 7, in this embodiment, a plurality of detector elements 121 included in a detector element array 120 are divided into a plurality of groups, and each group is associated with an individual channel C.

[0085] In this embodiment, the corrective X-ray detector 200 is further provided with a collimator 240 for preventing crosstalk between channels.

[0086] The collimator 240 is arranged on the X-ray incident side of the multiple detection elements 121 included in the detection element array 120, and is configured in a grid shape divided into multiple sections by X-ray shielding plates 241 that absorb scattered X-rays.

[0087] Specifically, the collimator 240 is disposed on the X-ray incident surface of the scintillator array 110. For example, the collimator 240 is a one-dimensional collimator or a two-dimensional collimator. The collimator 240 is divided into sections the same number as the number of channels C, and is positioned so that one section is disposed above a group of detection elements 121 corresponding to each channel.

[0088] Here, in order to reliably prevent crosstalk between channels, it is necessary to precisely position each section of the collimator 240 with respect to each group of the detection elements 121 that are divided into channels in advance. Furthermore, it is necessary to precisely position the X-ray shielding plate 241 of the collimator 240 so that it is inclined toward the focal point of the X-ray tube 11.

[0089] However, the detection elements used in X-ray detectors for imaging are typically smaller and more numerous than the detection elements required in corrective X-ray detectors, making it difficult to precisely position the collimator 240 and requiring costly implementation techniques.

[0090] For this reason, in this embodiment, the corrective X-ray detector 200 can be manufactured using a low-cost mounting technique that does not require precise positioning of the collimator 240.

[0091] 6, the correction DAS 230 is a processing circuit that generates correction data based on the electrical signals output from each detection element 121 of the detection element array 120. Specifically, the correction DAS 230 generates the correction data by amplifying the electrical signals output from each detection element 121 of the detection element array 120 and converting the amplified electrical signals from analog signals to digital signals.

[0092] Specifically, the correction DAS 230 has an acquisition function 231, a determination function 232, and a generation function 233. Here, the acquisition function 231 is an example of an acquisition unit. The determination function 232 is an example of a determination unit. The generation function 233 is an example of a generation unit.

[0093] The acquisition function 231 acquires a plurality of output values ​​corresponding to each of the plurality of detector elements 121 included in the detector element array 120 .

[0094] Specifically, the acquisition function 231 acquires the output value of the electrical signal output from each detection element 121 of the detection element array 120 when X-rays are incident on the scintillator array 110 of the corrective X-ray detector 200 from the X-ray tube 11.

[0095] The determination function 232 determines the detection element to be used for generating the correction data based on the multiple output values ​​acquired by the acquisition function 231.

[0096] Specifically, the determination function 232 performs threshold processing on the multiple output values ​​acquired by the acquisition function 231, and determines the detection elements to be used for generating the correction data based on the result of the threshold processing.

[0097] At this time, the determination function 232 determines, for each channel, a detection element to be used for generating correction data from among the detection elements 121 included in the corresponding group.

[0098] FIG. 8 is a diagram showing an example of detection element determination performed by the determination function 232 according to the second embodiment.

[0099] For example, as shown in Fig. 8, the determination function 232 detects, for each channel C, a detection element 121 whose output value is equal to or greater than an expected value E among the detection elements 121 included in the corresponding group. Then, the determination function 232 determines the detected detection element 121 as a detection element to be used for generating correction data. In the example shown in Fig. 8, the detection element 121 determined as a detection element to be used for generating correction data is hatched with diagonal lines.

[0100] Here, similarly to the first embodiment, the expected value E is a threshold value for determining whether or not the detection element 121 can sufficiently detect X-rays. For example, the expected value E is set in advance based on actual measurements, standard values, etc., when the corrective X-ray detector 100 is installed at an installation site such as a hospital.

[0101] In this way, in the detection element array 120, detection elements 121 whose output values ​​are less than the expected value E because they are in positions where X-rays are blocked by the X-ray shielding plate 241 of the collimator 240 are excluded from detection elements used for generating correction data. As a result, it becomes possible to generate correction data using detection elements 121 in the detection element array 120 other than detection elements 121 in positions where X-rays are blocked by the X-ray shielding plate 241 of the collimator 240.

[0102] Furthermore, similarly to the first embodiment, when a defective detection element 121 having an output value less than the expected value E is included in the detection element array 120, the detection element 121 is excluded from the detection elements used for generating the correction data. As a result, also in this embodiment, when a defective detection element is included among the multiple detection elements 121, the correction data can be generated using the detection elements 121 other than the defective detection element 121.

[0103] Returning to FIG. 6, the generation function 233 generates correction data for each channel based on the detection element determined by the determination function 232 .

[0104] Specifically, the generating function 233 generates the correction data for each channel by using the sum of the output values ​​of the detection elements determined by the determining function 232. Alternatively, for example, the generating function 233 may generate the correction data for each channel by using the average value of the output values ​​of the detection elements, or may generate the correction data by using the maximum value.

[0105] In this way, the correction data generated by the generation function 233 is transferred to the console device 40 via the DAS 18 for each channel, and stored in the memory 41. The correction data stored in the memory 41 is then read by the processing circuitry 44 and used to correct fluctuations in the dose and energy spectrum of X-rays irradiated from the X-ray tube 11. For this reason, for example, in this embodiment, filters (not shown) with different X-ray shielding capabilities are attached to each section of the collimator 240 so that X-rays with different energy spectra are detected for each channel. By comparing the correction data with different energy spectra, a change in the tube voltage can be detected.

[0106] FIG. 9 is a flowchart showing the procedure of processing performed by the X-ray CT apparatus 1 according to the second embodiment.

[0107] The process described below is executed, for example, when the X-ray CT apparatus 1 is installed at an installation site such as a hospital, or when the X-ray CT apparatus 1 is adjusted.

[0108] 9, first, when the processing circuitry 44 receives a start instruction from the operator via the input interface 43 (step S201, Yes), it controls the X-ray high voltage device 14 to irradiate X-rays from the X-ray tube 11 to the scintillator array 110 of the corrective X-ray detector 200 (step S202). This step corresponds to the control function 441. In this step, for example, the processing circuitry 44 reads out a program corresponding to the control function 441 from the memory 41 and executes it, thereby realizing the control function 441.

[0109] Next, the correction DAS 230 acquires a plurality of output values ​​corresponding to the plurality of detection elements 121 included in the detection element array 120 (step S203). This step corresponds to the acquisition function 231. In this step, for example, the correction DAS 230 reads out a program corresponding to the acquisition function 231 from a memory and executes it, thereby realizing the acquisition function 231.

[0110] Next, the correction DAS 230 detects, for each channel, a detection element 121 having an output value equal to or greater than an expected value among the detection elements 121 included in the corresponding group based on the acquired multiple output values ​​(step S204). Then, the correction DAS 230 determines, for each channel, the detected detection element 121 as a detection element to be used for generating correction data (step S205). These steps correspond to the determination function 232. In these steps, for example, the correction DAS 230 reads out a program corresponding to the determination function 232 from a memory and executes it, thereby realizing the determination function 232.

[0111] Next, the correction DAS 230 generates correction data for each channel based on the determined detection element (step S206). This step corresponds to the generation function 233. In this step, for example, the correction DAS 230 reads out a program corresponding to the generation function 233 from a memory and executes it, thereby realizing the generation function 233.

[0112] As described above, in the second embodiment, the correction X-ray detector 200 includes a plurality of detection elements 121 that detect X-rays. Then, the acquisition function 231 of the correction DAS 230 acquires a plurality of output values ​​corresponding to each of the plurality of detection elements 121, and the determination function 232 determines the detection element to be used for generating correction data based on the plurality of output values.

[0113] According to this configuration, as in the first embodiment, when a defective detection element is included among the multiple detection elements 121, correction data can be generated using detection elements 121 other than the defective detection element 121. As a result, for example, multiple detection elements that were manufactured for use in the X-ray detector 12 for imaging but became unusable because they included a defective detection element can be diverted to the correction X-ray detector 200, and the correction X-ray detector 200 can be manufactured at low cost. Therefore, according to this embodiment, the cost associated with mounting the correction X-ray detector 200 can be reduced.

[0114] In the second embodiment, the multiple detection elements 121 included in the detection element array 120 are divided into multiple groups, and each group is associated with an individual channel C. Then, the determination function 232 determines, for each channel, a detection element to be used for generating correction data from among the detection elements 121 included in the corresponding group.

[0115] According to such a configuration, as described above, it becomes possible to generate correction data using detection elements 121 in the detection element array 120 other than the detection elements 121 located at positions where X-rays are blocked by the X-ray shielding plates 241 of the collimator 240. This makes it possible to manufacture the corrective X-ray detector 200 using a low-cost mounting technique that does not strictly position the collimator 240. Therefore, according to this embodiment, it is possible to further reduce the cost associated with mounting the corrective X-ray detector 200.

[0116] (First modified example of the second embodiment) In the above-described second embodiment, the determination function 232 determines the detection element using the expected value of the output value, but the embodiment is not limited to this. For example, the determination function 232 may determine the detection element by further using the upper limit value of the output value.

[0117] In that case, for example, the determination function 232 detects, for each channel, among the detection elements 121 included in the corresponding group, a detection element 121 whose output value is greater than or equal to an expected value and less than an upper limit value greater than the expected value, and determines the detected detection element 121 as the detection element to be used for generating correction data.

[0118] Here, similarly to the modified example of the first embodiment, the upper limit value is a threshold value for detecting detection elements 121 that cause an error in signal processing due to an output value that is too large in the corrective X-ray detector 200. For example, the upper limit value is set in advance based on actual measurement values, standard values, etc., when the corrective X-ray detector 200 is installed at an installation location such as a hospital.

[0119] As a result, if the detector array 120 includes a detector element 121 whose output value will result in an error in signal processing, the detector element 121 is further excluded from the detector elements used to generate correction data.

[0120] According to such a configuration, by using only the detection elements 121 whose output values ​​do not result in errors in signal processing, it becomes possible to generate correction data with higher accuracy.

[0121] (Second Modification of the Second Embodiment) In addition, in the above-mentioned second embodiment, an example has been described in which the acquisition function 231 acquires the output value of the electrical signal output from each detection element 121 of the detection element array 120 when X-rays are irradiated from the X-ray tube 11 to the scintillator array 110 of the correction X-ray detector 200, but the embodiment is not limited to this.

[0122] For example, it is known that the position of the focal point of the X-ray tube 11 varies due to heat generation, and when the position of the focal point varies, the angle of incidence of the X-rays incident on the scintillator array 110 of the corrective X-ray detector 200 also varies. When the angle of incidence of the X-rays incident on the scintillator array 110 varies, the detection elements 121 in the detection element array 120 whose X-rays are blocked by the X-ray shielding plate 241 of the collimator 240 also vary.

[0123] Therefore, for example, correction data may be generated taking into consideration fluctuations in the position of the focal point in the X-ray tube 11.

[0124] In this case, the acquisition function 231 varies the position of the focal point in the X-ray tube 11 to a plurality of different positions, and acquires a plurality of output values ​​corresponding to each of the plurality of detection elements 121 included in the detection element array 120 for each of the different positions. Furthermore, the determination function 232 determines a detection element to be used for generating correction data for each different focal point position. Furthermore, the generation function 233 generates correction data for each different focal point position based on the detection element determined by the determination function 232.

[0125] In this way, the correction data generated by the generation function 233 is transferred to the console device 40 via the DAS 18 for each different focal position, and is stored in the memory 41. The correction data stored in the memory 41 is then read out by the processing circuitry 44 and used to correct fluctuations in the dose and energy spectrum of the X-rays irradiated from the X-ray tube 11.

[0126] According to such a configuration, for example, when imaging the subject P, the position of the focal point is identified based on the temperature of the X-ray tube 11, and correction data corresponding to the identified position is used, thereby making it possible to more accurately correct fluctuations in the dose and energy spectrum of the X-rays irradiated from the X-ray tube 11.

[0127] Alternatively, for example, the determination function 232 may detect detection elements for each different focal position, identify detection elements that are detected in duplicate at all positions, and determine the identified detection elements as the detection elements to be used for generating correction data.

[0128] According to such a configuration, even when the incident angle of the X-rays incident on the scintillator array 110 varies due to a change in the position of the focal point in the X-ray tube 11, correction data is generated using only the detection elements 121 whose X-rays are not blocked by the X-ray shielding plate 241 of the collimator 240. This makes it possible to more accurately correct the fluctuations in the dose and energy spectrum of the X-rays irradiated from the X-ray tube 11.

[0129] (Third embodiment) In the above-mentioned first and second embodiments, an example in which the correction X-ray detector has an acquisition function, a determination function, and a generation function has been described, but the embodiment is not limited thereto. For example, the DAS 18 that generates detection data based on an electrical signal output from the X-ray detector 12 for imaging may further have an acquisition function, a determination function, and a generation function. Therefore, in the following, as a third embodiment, an example in which the DAS 18 has an acquisition function, a determination function, and a generation function will be described. In the following, differences from the first and second embodiments will be mainly described, and components common to the first and second embodiments will be denoted by the same reference numerals and detailed description will be omitted.

[0130] In this embodiment, an example in which the corrective X-ray detector has one channel will be described.

[0131] FIG. 10 is a diagram showing an example of the configuration of a corrective X-ray detector 300 and a DAS 18 according to the third embodiment.

[0132] 10, in this embodiment, a corrective X-ray detector 300 has a scintillator array 110 and a detection element array 120. Here, the scintillator array 110 and the detection element array 120 each have the configuration described in the first embodiment.

[0133] Moreover, the DAS 18 has an acquisition function 181, a decision function 182, and a generation function 183. Here, the acquisition function 181 is an example of an acquisition unit. The decision function 182 is an example of a decision unit. The generation function 183 is an example of a generation unit.

[0134] The acquisition function 181, the decision function 182, and the generation function 183 have the same functions as the acquisition function 131, the decision function 132, and the generation function 133 described in the first embodiment, respectively, except that they are realized by the DAS 18.

[0135] In this manner, the correction data generated by the generation function 183 is transferred to the console device 40 and stored in the memory 41. The correction data stored in the memory 41 is then read out by the processing circuitry 44 and used to correct fluctuations in the dose of X-rays irradiated from the X-ray tube 11.

[0136] Here, for example, DAS18 is realized by a processor. In this case, each processing function of DAS18 is stored in a memory (not shown) in the form of a program executable by a computer. Then, DAS18 realizes the processing function corresponding to each program by reading each program from the memory and executing it. In other words, DAS18 has each processing function shown in DAS18 in FIG. 10 when each program is read.

[0137] As described above, in the third embodiment, the correction X-ray detector 300 includes a plurality of detection elements 121 that detect X-rays. Then, the acquisition function 181 of the DAS 18 acquires a plurality of output values ​​corresponding to each of the plurality of detection elements 121, and the determination function 182 determines the detection element to be used for generating correction data based on the plurality of output values.

[0138] According to this configuration, as in the first embodiment, when a defective detection element is included among the multiple detection elements 121, correction data can be generated using detection elements 121 other than the defective detection element 121. As a result, for example, multiple detection elements that were manufactured for use in the X-ray detector 12 for imaging but became unusable because they included a defective detection element can be diverted to the correction X-ray detector 300, and the correction X-ray detector 300 can be manufactured at low cost. Therefore, according to this embodiment, the cost associated with mounting the correction X-ray detector 300 can be reduced.

[0139] (Modification of the third embodiment) In the above-described third embodiment, the correction X-ray detector has one channel, but the embodiment is not limited to this. For example, the correction X-ray detector may have multiple channels.

[0140] In that case, for example, the corrective X-ray detector 300 has a scintillator array 110, a detection element array 120, and a collimator 240. Here, the scintillator array 110, the detection element array 120, and the collimator 240 each have the configuration described in the second embodiment.

[0141] Furthermore, except that the acquisition function 181, the decision function 182, and the generation function 183 are realized by the DAS 18, they have the same functions as the acquisition function 231, the decision function 232, and the generation function 233 described in the second embodiment, respectively.

[0142] In this way, the correction data generated by the generation function 233 is transferred to the console device 40 for each channel and stored in the memory 41. The correction data stored in the memory 41 is then read out by the processing circuitry 44 and used to correct fluctuations in the dose and energy spectrum of the X-rays irradiated from the X-ray tube 11.

[0143] According to this configuration, similarly to the second embodiment, correction data can be generated using detection elements 121 in the detection element array 120 other than the detection elements 121 located at positions where X-rays are blocked by the X-ray shielding plates 241 of the collimator 240. This makes it possible to manufacture the corrective X-ray detector 200 using a low-cost mounting technique that does not strictly position the collimator 240. Therefore, according to this embodiment, the cost associated with mounting the corrective X-ray detector 200 can be further reduced.

[0144] (Fourth embodiment) In the above-mentioned third embodiment, an example in which the DAS 18 has an acquisition function, a decision function, and a generation function has been described, but the embodiment is not limited thereto. For example, the processing circuit 44 of the console device 40 may further have an acquisition function, a decision function, and a generation function. Therefore, in the following, as the fourth embodiment, an example in which the processing circuit 44 of the console device 40 has an acquisition function, a decision function, and a generation function will be described. In the following, differences from the first to third embodiments will be mainly described, and components common to the first to third embodiments will be denoted by the same reference numerals and detailed description will be omitted.

[0145] In this embodiment, an example in which the corrective X-ray detector has one channel will be described.

[0146] FIG. 11 is a diagram showing an example of the configuration of a corrective X-ray detector 300 and a processing circuit 44 of a console device 40 according to the fourth embodiment.

[0147] 11, in this embodiment, a corrective X-ray detector 300 has a scintillator array 110 and a detection element array 120. Here, the scintillator array 110 and the detection element array 120 each have the configuration described in the first embodiment.

[0148] Moreover, the processing circuit 44 of the console device 40 has an acquisition function 446, a determination function 447, and a generation function 448 in addition to the control function 441, preprocessing function 442, reconstruction processing function 443, image processing function 444, and display control function 445 (not shown in FIG. 11) shown in FIG. 1. Here, the acquisition function 446 is an example of an acquisition section. Also, the determination function 447 is an example of a determination section. Also, the generation function 448 is an example of a generation section.

[0149] The acquisition function 446, the decision function 447 and the generation function 448 have functions similar to the acquisition function 131, the decision function 132 and the generation function 133 described in the first embodiment, respectively, except that they are realized by the processing circuit 44 of the console device 40.

[0150] In this manner, the correction data generated by the generation function 448 is stored in the memory 41. The correction data stored in the memory 41 is then read out by the processing circuitry 44 and used to correct fluctuations in the dose of X-rays irradiated from the X-ray tube 11.

[0151] Here, for example, the processing circuitry 44 is realized by a processor. In this case, each processing function possessed by the processing circuitry 44 is stored in the memory 41 in the form of a program executable by a computer. Then, the processing circuitry 44 realizes the processing function corresponding to each program by reading and executing each program from the memory 41. In other words, the processing circuitry 44 has each processing function shown in the processing circuitry 44 in FIG. 11 in a state where each program is read.

[0152] As described above, in the fourth embodiment, the correction X-ray detector 300 includes a plurality of detection elements 121 that detect X-rays. Then, the acquisition function 446 of the processing circuitry 44 of the console device 40 acquires a plurality of output values ​​corresponding to each of the plurality of detection elements 121, and the determination function 447 determines the detection element to be used for generating correction data based on the plurality of output values.

[0153] According to this configuration, as in the first embodiment, when a defective detection element is included among the multiple detection elements 121, correction data can be generated using detection elements 121 other than the defective detection element 121. As a result, for example, multiple detection elements that were manufactured for use in the X-ray detector 12 for imaging but became unusable because they included a defective detection element can be diverted to the correction X-ray detector 300, and the correction X-ray detector 300 can be manufactured at low cost. Therefore, according to this embodiment, the cost associated with mounting the correction X-ray detector 300 can be reduced.

[0154] (Modification of the fourth embodiment) In the above-described fourth embodiment, the correction X-ray detector has one channel, but the embodiment is not limited to this. For example, the correction X-ray detector may have multiple channels.

[0155] In that case, for example, the corrective X-ray detector 300 has a scintillator array 110, a detection element array 120, and a collimator 240. Here, the scintillator array 110, the detection element array 120, and the collimator 240 each have the configuration described in the second embodiment.

[0156] In addition, except that the acquisition function 446, the decision function 447 and the generation function 448 are realized by the processing circuit 44 of the console device 40, they respectively have the same functions as the acquisition function 231, the decision function 232 and the generation function 233 described in the second embodiment.

[0157] In this way, the correction data generated by the generation function 448 is stored for each channel in the memory 41. The correction data stored in the memory 41 is read out by the processing circuitry 44 and used to correct fluctuations in the dose and energy spectrum of the X-rays irradiated from the X-ray tube 11.

[0158] According to this configuration, similarly to the second embodiment, correction data can be generated using detection elements 121 in the detection element array 120 other than the detection elements 121 located at positions where X-rays are blocked by the X-ray shielding plates 241 of the collimator 240. This makes it possible to manufacture the corrective X-ray detector 200 using a low-cost mounting technique that does not strictly position the collimator 240. Therefore, according to this embodiment, the cost associated with mounting the corrective X-ray detector 200 can be further reduced.

[0159] Fifth embodiment Furthermore, according to each of the above-described embodiments and modified examples, as described above, a plurality of detection elements that were manufactured for use in the X-ray detector 12 for imaging but became unusable due to including a defective detection element can be repurposed into the correction X-ray detector 100.

[0160] Hereinafter, as a fifth embodiment, a detection element determination method for determining detection elements to be used for generating correction data in the corrective X-ray detector 100 when such detection elements are diverted will be described.

[0161] FIG. 12 is a flowchart showing a detection element determination method according to the fifth embodiment.

[0162] For example, as shown in FIG. 12, the detection element determination method according to this embodiment includes steps S501 to S503.

[0163] In step S501, a detector element array including a defective detector element is detected from among a plurality of detector element arrays manufactured for use in the X-ray detector 12 for imaging.

[0164] Specifically, in step S501, for each of a plurality of detector element arrays produced for use in the X-ray detector 12 for imaging, each detector element included in the detector element array is inspected by a predetermined inspection method to determine whether or not it contains a defective detector element. Here, a detector element array determined to contain no defective detector elements is determined to be used in the X-ray detector 12 for imaging. On the other hand, a detector element array determined to contain defective detector elements is determined to be used in the X-ray detector 100 for correction.

[0165] Next, in step S502, the detection element array detected in step S501 is implemented as a detection element array of a correction X-ray detector.

[0166] Specifically, in step S502, the detector element array detected in step S501 is implemented in the X-ray CT device 1 by using it as a detector element array of a corrective X-ray detector relating to any of the above-mentioned embodiments or modified examples.

[0167] Next, in step S503, a detection element to be used for generating correction data is determined from among the multiple detection elements included in the detection element array implemented in step S502.

[0168] Specifically, in step S503, as described in the above-mentioned embodiments or modifications, the determination function determines the detection elements to be used for generating the correction data.

[0169] For example, the detection element determination method according to the present embodiment further includes a step of obtaining, by an acquisition function, a plurality of output values ​​corresponding to the plurality of detection elements implemented in step S502. Then, in step S503, a determination function determines a detection element to be used for generating correction data based on the plurality of output values. For example, the determination function performs threshold processing on the plurality of output values, and determines a detection element to be used for generating correction data based on the result of the threshold processing.

[0170] Also, for example, the detection element determination method according to the present embodiment further includes a step of associating one channel with at least some of the detection elements implemented in step S502 by the correction DAS. In this case, in step S503, as described in the first embodiment, the modified example of the first embodiment, the third embodiment, or the fourth embodiment, a determination function is used to determine a detection element to be used for generating correction data from among the detection elements with which the channel is associated.

[0171] Alternatively, for example, the detection element determination method according to the present embodiment may further include a step of dividing the multiple detection elements implemented in step S502 into multiple groups and associating each group with an individual channel. In this case, in step S503, as described in the second embodiment, the modified example of the second embodiment, the modified example of the third embodiment, or the modified example of the fourth embodiment, a determination function is used to determine, for each channel, a detection element to be used for generating the correction data from among the detection elements included in the corresponding group.

[0172] Also, for example, the detection element determination method according to this embodiment may use an acquisition function to vary the focal position of the X-ray tube to multiple different positions, and acquire multiple output values ​​corresponding to each of the multiple detection elements included in the detection element array implemented in step S502, as described in the second modification of the second embodiment. In this case, in step S503, the determination function determines the detection elements to be used for generating correction data for each different focal position, as described in the second modification of the second embodiment.

[0173] (Other embodiments) In each of the above-described embodiments, the correction X-ray detector is provided between the X-ray tube 11 and the wedge 16, but the embodiments are not limited to this. For example, the correction X-ray detector may be disposed on the same detection surface as the X-ray detector 12 for imaging. In this case, the correction X-ray detector may be configured separately from the X-ray detector 12, or may be configured integrally with the X-ray detector 12.

[0174] In addition, in each of the above-mentioned embodiments, examples have been described in which the acquisition unit, determination unit, and generation unit in this specification are realized by the acquisition function, determination function, and generation function of the processing circuits (DAS130 for correction, DAS230 for correction, DAS18, and processing circuit 44), respectively, but the embodiments are not limited to this. For example, the acquisition unit, determination unit, and generation unit in this specification may be realized by only hardware, only software, or a combination of hardware and software, in addition to being realized by the acquisition function, determination function, and generation function described in the embodiments.

[0175] In addition, in each of the above-mentioned embodiments, each processing function described as being realized by a single processing circuit may be realized, for example, by combining multiple independent processors to configure a processing circuit and having each processor execute a program. Also, each processing function possessed by a processing circuit may be appropriately distributed or integrated and realized in a single or multiple processing circuits. Also, each processing function possessed by a processing circuit may be realized by a mixture of hardware and software such as a circuit. Also, here, an example in which a single memory 41 stores a program corresponding to each processing function has been described, but the embodiment is not limited to this. For example, a configuration in which multiple storage circuits are distributed and arranged, and a processing circuit reads out and executes a corresponding program from each storage circuit may be used.

[0176] In addition, the term "processor" used in the above description means a circuit such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or an Application Specific Integrated Circuit (ASIC), a programmable logic device (e.g., a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), and 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 a memory circuit. On the other hand, when the processor is an ASIC, for example, instead of storing a program in a memory circuit, the function is directly incorporated as a logic circuit in the circuit of the processor. Note that each processor in this embodiment is not limited to being configured as a single circuit for each processor, but may be configured as a single processor by combining multiple independent circuits to realize the function. Furthermore, the multiple components in FIG. 1 may be integrated into a single processor to realize the function.

[0177] In addition, in the above-mentioned embodiment and modified example, each component of each device shown in the figure is functionally conceptual, and does not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution or integration of each device is not limited to that shown in the figure, and all or a part of it can be functionally or physically distributed or integrated in any unit according to various loads, usage conditions, etc. Furthermore, all or any part of each processing function performed by each device can be realized by a CPU and a program analyzed and executed by the CPU, or can be realized as hardware using wired logic.

[0178] Furthermore, among the processes described in the above-mentioned embodiments and modifications, all or part of the processes described as being performed automatically can be performed manually, or all or part of the processes described as being performed manually can be performed automatically by a known method. In addition, the information including the processing procedures, control procedures, specific names, various data and parameters shown in the above documents and drawings can be changed arbitrarily unless otherwise specified.

[0179] According to at least one of the embodiments described above, it is possible to reduce the cost associated with mounting the corrective X-ray detector.

[0180] Although some 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 in the scope of the invention and its equivalents as described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0181] 1 X-ray CT device 18 DAS 40 Console device 44 Processing circuit 100,200,300 Correction X-ray detector 110 Scintillator Array 120 Detector Array 130,230 Correction DAS 240 Collimator 131,231,181,446 Acquisition function 132,232,182,447 Decision function 133,233,183,448 generation function

Claims

1. A detection element determination method applied to an X-ray CT apparatus including a main detector for imaging and a correction X-ray detector including a plurality of detection elements for detecting X-rays, the detection elements being produced for use in the main detector for imaging but being unusable for the main detector for imaging because they include a defective detection element, comprising: detecting a detector element array including defective detector elements and detector elements other than the defective detector elements from among a plurality of detector element arrays produced for use in the main detector; Implementing the detected detector array as the plurality of detector elements of the correction X-ray detector; determining a detection element to be used for generating correction data from among a plurality of detection elements included in the mounted detection element array; A detection element determination method comprising:

2. obtaining a plurality of output values ​​corresponding to each of the plurality of detection elements; The step of determining the detection element includes determining a detection element to be used for generating the correction data based on the plurality of output values. The detection element determination method according to claim 1 .

3. the step of determining the detection element includes performing a threshold process on the plurality of output values, and determining a detection element to be used for generating the correction data based on a result of the threshold process. The detection element determination method according to claim 2 .

4. The method further includes the step of: associating one channel with at least a portion of the plurality of detection elements; the step of determining the detection element includes determining a detection element to be used for generating the correction data among detection elements to which the channel is associated; The detection element determination method according to any one of claims 1 to 3.

5. further comprising the step of dividing the plurality of detector elements into a plurality of groups and associating a separate channel with each group; the step of determining the detection elements includes determining, for each of the channels, a detection element to be used for generating the correction data from among detection elements included in a corresponding group; The detection element determination method according to any one of claims 1 to 3.

6. the step of acquiring the output values ​​includes: varying a position of a focal spot of an X-ray tube to a plurality of different positions; and acquiring a plurality of output values ​​corresponding to each of the plurality of detection elements for each of the different positions; the step of determining a detection element includes determining, for each of the different positions, a detection element to be used for generating the correction data. The detection element determination method according to claim 2 or 3.

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