Correction detector and x-ray CT apparatus

Abstract

To provide a detector for correction that supports increase in a speed of an X-ray CT apparatus equipped with a sequential readout data collection system, and an X-ray CT apparatus including the detector for correction.SOLUTION: A detector for correction according to an embodiment is mounted on an X-ray CT apparatus that generates an image of a subject on the basis of detection data obtained by detecting X-rays having passed through a subject, detects detection data for correction for generating correction data used to correct the detection data, and includes a first detection element, an integration circuit, and an analog / digital converter. The first detection element outputs a first signal obtained by detecting original X-rays before passing through the subject. The integration circuit integrates and holds a charge corresponding to the first signal at a first period based on a period during which the detection data is detected, and outputs a second signal based on the held charge. The analog / digital converter outputs the detection data for correction obtained by converting the second signal into analog / digital data at a second period shorter than the first period.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The embodiments disclosed in this specification and the drawings relate to a correction detector and an X-ray CT apparatus. [Background technology]

[0002] In an X-ray CT (Computed Tomography) device, a patient is irradiated with X-rays generated by an X-ray tube, and the intensity of the X-rays that pass through the patient is detected by an X-ray detector having multiple X-ray detection elements. In an X-ray CT device, the intensity of the X-rays irradiated from the X-ray tube to the patient varies over time. For this reason, in an X-ray CT device, a correction detector that detects the intensity of the original X-rays irradiated from the X-ray tube to the patient is placed near the X-ray tube. The electrical signal that indicates the intensity of the X-rays detected by the X-ray detector and that indicates the intensity of the original X-rays detected by the correction detector is compared to correct the electrical signal that indicates the intensity of the X-rays that have passed through the patient and that is detected by the X-ray detector.

[0003] In recent years, there has been a study on increasing the speed of X-ray CT scanners. In this case, the readout speed of electrical signals from the X-ray detector by the DAS is increased, but in an X-ray CT scanner equipped with a sequential readout DAS, the readout speed of electrical signals from the correction detector must also be increased in accordance with the increase in the readout speed of electrical signals from the X-ray detector. In this case, there is a concern that noise may be included in the electrical signals read out from the correction detector that corresponds to the increase in speed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-107297 A Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the embodiments disclosed in this specification and the drawings is to provide a correction detector that corresponds to the high speed of an X-ray CT device equipped with a data acquisition system that reads out electrical signals from an X-ray detector by sequential readout, and an X-ray CT device equipped with this correction detector. However, the problem to be solved by the embodiments disclosed in this specification and the drawings is 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]

[0006] The correction detector of the embodiment is mounted on an X-ray CT apparatus that generates an image of an object based on detection data obtained by periodically detecting X-rays irradiated from an X-ray tube and passing through the object, and detects correction detection data for generating correction data used to correct the detection data, and includes one first detection element, an integration circuit, and an analog / digital converter. The first detection element detects the original X-ray irradiated from the X-ray tube before passing through the object, and outputs a first signal representing the intensity of the original X-ray. The integration circuit integrates and holds a charge corresponding to the first signal in a first cycle based on a period for detecting the detection data, and outputs a second signal based on the held charge. The analog / digital converter analog / digital converts the second signal in a second cycle shorter than the first cycle, and outputs the correction detection data representing the magnitude of the second signal. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of an X-ray CT apparatus including a correction detector according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of a circuit configuration of a correction detector according to the first embodiment. [Diagram 3] 5 is a timing chart showing an example of the timing of an operation in the correction detector according to the first embodiment. [Figure 4] FIG. 11 is a diagram showing an example of a circuit configuration of a correction detector according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, a correction detector and an X-ray CT device according to an embodiment will be described with reference to the drawings. In the following description, it is assumed that the correction detector is provided in an X-ray CT (Computed Tomography) device for performing CT examinations, and that the X-ray CT device captures CT images, which are images of a subject (patient).

[0009] 1 is a diagram showing an example of the configuration of an X-ray CT device equipped with a correction detector according to an embodiment. The X-ray CT device 1 is a medical image diagnostic device that irradiates X-rays onto a patient P, who is a subject, and detects the X-rays that have passed through the patient P. The X-ray CT device 1 generates and displays images such as a reconstructed image (e.g., a CT image) corresponding to the detected X-rays. This allows a person performing the CT examination (such as a doctor or technician) to visually check whether or not the patient P has a lesion.

[0010] The X-ray CT apparatus 1 includes, for example, a gantry 10, a bed 30, and a console 40. In FIG. 1, for convenience of explanation, the gantry 10 is shown both in the Z-axis direction and in the X-axis direction, but in reality, the X-ray CT apparatus 1 includes only one gantry 10. In this embodiment, the central axis of the rotating frame 17 in a non-tilted state or the longitudinal direction of the top plate 33 of the bed 30 (body axis direction of the patient P) is defined as the Z-axis direction, an axis perpendicular to the Z-axis direction and horizontal to the floor surface is defined as the X-axis direction, and a direction perpendicular to the Z-axis direction and perpendicular to the floor surface is defined as the Y-axis direction. The X-ray CT apparatus 1 is an example of an "X-ray CT apparatus."

[0011] The gantry device 10 includes, for example, an X-ray tube device 11 incorporating an X-ray tube, a wedge 12, a collimator 13, an X-ray high voltage device 14, an X-ray detector 15, a data acquisition system (hereinafter, DAS: Data Acquisition System) 16, a rotating frame 17, a control device 18, a reference detector 20, and a data acquisition system (DAS) 21.

[0012] The X-ray tube device 11 generates X-rays by causing an internal X-ray tube to emit thermoelectrons from a cathode (filament) toward an anode (target) in response to a high tube voltage applied by an X-ray high voltage device 14. The X-ray tube device 11 includes, for example, a vacuum tube as an X-ray tube. In the following description, for ease of explanation, the X-ray tube device 11 will be described as an X-ray tube. The X-ray tube device 11 is, for example, a rotating anode type X-ray tube that generates X-rays by emitting thermoelectrons from a cathode to a rotating anode. The X-rays generated by the X-ray tube device 11 are irradiated onto a patient P.

[0013] The wedge 12 is a filter for adjusting the dose (X-ray amount) when the patient P is irradiated with X-rays generated by the X-ray tube device 11. The wedge 12 attenuates the X-rays passing through it so that the distribution of the X-ray amount irradiated to the patient P becomes a predetermined distribution. The wedge 12 is also called a wedge filter or a bow-tie filter. The wedge 12 is, for example, made by processing aluminum so as to have a predetermined target angle and a predetermined thickness.

[0014] The collimator 13 is a mechanism for narrowing down the irradiation range of the X-rays transmitted through the wedge 12. The collimator 13 narrows down the irradiation range of the X-rays, for example, by combining multiple lead plates to form slits. The collimator 13 may also be called an X-ray aperture. The collimator 13 may be an active collimator whose narrowing range can be mechanically driven.

[0015] X-ray tube assembly 11 (which may include wedge 12 and collimator 13) is an example of an "X-ray tube."

[0016] The X-ray high voltage device 14 includes, for example, a high voltage generator and an X-ray control device. The high voltage generator has an electric circuit including a transformer and a rectifier, and generates a high voltage to be applied to the X-ray tube device 11. The X-ray control device controls the output voltage of the high voltage generator according to the amount of X-rays to be generated by the X-ray tube device 11. The high voltage generator may be one that boosts the voltage using the above-mentioned transformer, or one that boosts the voltage using an inverter. The X-ray high voltage device 14 may be provided on the rotating frame 17, or may be provided on the side of a fixed frame (not shown) provided on the gantry device 10.

[0017] The X-ray detector 15 detects the intensity of X-rays generated by the X-ray tube device 11 and incident upon the patient P. The X-ray detector 15 outputs an electrical signal (which may be an optical signal, etc.) corresponding to the intensity of the detected X-rays to the DAS 16. The X-ray detector 15 has, for example, multiple X-ray detection element rows. In each of the multiple X-ray detection element rows, multiple X-ray detection elements are arranged in the channel direction along an arc centered on the focal point of the X-ray tube device 11. The multiple X-ray detection element rows are arranged in the slice direction (column direction, row direction).

[0018] The X-ray detector 15 is an indirect detector having, for example, a grid, a scintillator array, and a photosensor array. The scintillator array has a plurality of scintillators. Each scintillator has a scintillator crystal. The scintillator crystal emits an amount of light according to the intensity of the incident X-ray. The grid is disposed on the surface of the scintillator array on which the X-ray is incident, and has an X-ray shielding plate having a function of absorbing scattered X-rays. The grid may also be called a collimator (one-dimensional collimator or two-dimensional collimator). The photosensor array has, for example, a photosensor such as a photomultiplier tube (PMT). The photosensor array outputs an electric signal according to the amount of light emitted by the scintillator. The X-ray detector 15 may be a direct conversion detector having a semiconductor element that converts the incident X-ray into an electric signal.

[0019] The DAS 16 includes, for example, an amplifier, an integrator, and an A / D converter. The amplifier amplifies the electric signal output by each X-ray detection element of the X-ray detector 15. The integrator integrates the electric signal amplified by the amplifier over a view period (described later). The A / D converter converts the electric signal indicating the integration result by the integrator into a digital signal. The DAS 16 outputs detection data based on the digital signal to the console device 40. The detection data is a digital value of X-ray intensity identified by the channel number and column number of the X-ray detection element that generated the data, and a view number indicating the acquired view. The view number is a number that changes according to the rotation of the rotating frame 17, and is, for example, a number that is incremented according to the rotation of the rotating frame 17. Therefore, the view number is information indicating the rotation angle of the X-ray tube device 11. The view period is a period that falls within the period from a rotation angle corresponding to a certain view number to a rotation angle corresponding to the next view number. In other words, the view period is a period required to obtain detection data for one irradiation time (projection period) of X-rays irradiated from the X-ray tube device 11 to the patient P at the same rotation angle. The DAS 16 may detect the view switching by a timing signal input from the control device 18, an internal timer, or a signal obtained from a sensor (not shown). When the X-ray CT device 1 performs a full scan and X-rays are continuously irradiated by the X-ray tube device 11, the DAS 16 collects a group of detection data for the entire circumference (360 degrees). When the X-ray CT device 1 performs a half scan and X-rays are continuously irradiated by the X-ray tube device 11, the DAS 16 collects detection data for half the circumference (180 degrees).

[0020] The DAS 16 is a sequential readout DAS that sequentially reads out electrical signals from the X-ray detection elements arranged in the X-ray detector 15 with a time lag. In other words, the DAS 16 does not simultaneously read out electrical signals from the X-ray detection elements arranged in the X-ray detector 15 during a view period, but reads out electrical signals from each X-ray detection element while moving the X-ray detection elements arranged in the X-ray detector 15 in order in the slice direction during the same view period.

[0021] The X-ray detector 15 is an example of a "detector." The multiple X-ray detection elements included in the X-ray detector 15 are an example of a "second detection element." An electrical signal (which may be an optical signal, etc.) output by the X-ray detector 15 according to the intensity of the detected X-rays is an example of a "third signal." The DAS 16 is an example of a "collection unit." The detection data output by the DAS 16 is an example of "detection data." The view period is an example of a "period for detecting detection data" and is also an example of a "first period." The channel direction is an example of a "first direction," and the slice direction (column direction, row direction) is an example of a "second direction." The X-ray detection element row is an example of a "detection element row."

[0022] The reference detector 20 detects the intensity of the X-rays generated by the X-ray tube device 11 and incident thereon. That is, the reference detector 20 detects the intensity of the X-rays (original X-rays) before passing through the patient P. FIG. 1 shows an example in which the reference detector 20 is disposed at a position between the X-ray tube device 11 and the wedge 12, but the position at which the reference detector 20 is disposed may be any position as long as it is a position where the intensity of the X-rays before passing through the patient P can be detected. The reference detector 20 outputs an electric signal (which may be an optical signal or the like) according to the intensity of the detected X-rays to the DAS 21. The reference detector 20 has, for example, one X-ray detection element. That is, the reference detector 20 is a one-channel X-ray detector. The X-ray detection element of the reference detector 20 may be an indirect type detector or a direct conversion type detector, similar to the X-ray detection element of the X-ray detector 15.

[0023] The DAS21 collects detection data for comparison (reference) based on the electrical signals output by the X-ray detection elements of the reference detector 20 (hereinafter referred to as "reference detection data") used to correct the detection data collected by the DAS16. When the DAS16 is a sequential readout DAS, the DAS21 collects reference detection data based on the electrical signals from the reference detector 20 in a cycle shorter than the view period. The DAS21 has, for example, an amplifier, an integrator, and an A / D converter, similar to the DAS16. The configuration of the DAS21 will be described in detail later. The DAS21 performs amplification, integration, and conversion to digital signals on the electrical signals output by the X-ray detection elements of the reference detector 20, and outputs reference detection data (digital values ​​of X-ray intensity detected by the reference detector 20) based on the converted digital signals to the console device 40. The DAS21 may control the execution of the conversion process of the electric signal output by the X-ray detection element of the reference detector 20 into a digital signal, for example, by a timing signal input from the control device 18, by an internal timer, or by a signal acquired from a sensor (not shown). When the X-ray CT device 1 performs a full scan and X-rays are continuously irradiated by the X-ray tube device 11, the DAS21 collects reference detection data for the entire circumference (360 degrees) like the DAS16. When the X-ray CT device 1 performs a half scan and X-rays are continuously irradiated by the X-ray tube device 11, the DAS21 collects reference detection data for half the circumference (180 degrees) like the DAS16. The DAS21 may generate correction data (hereinafter referred to as "reference data") for comparison (reference) used to correct the detection data collected by the DAS16 based on the collected reference detection data, and output the generated reference data to the console device 40.

[0024] The configuration of the reference detector 20 and the DAS 21 is an example of a "correction detector." The X-ray detection element included in the reference detector 20 is an example of a "first detection element." An electrical signal (which may be an optical signal, etc.) output by the reference detector 20 according to the intensity of the detected X-rays is an example of a "first signal." The reference data is an example of "correction data." The reference detection data is an example of "correction detection data."

[0025] The rotating frame 17 is an annular member that supports the X-ray tube device 11, the wedge 12, the collimator 13, and the reference detector 20, and the X-ray detector 15 in a facing manner. The rotating frame 17 is supported by a fixed frame so as to be rotatable around the patient P introduced inside. The rotating frame 17 further supports the DAS 16 and the DAS 21. The detection data output by each of the DAS 16 and the DAS 21 is transmitted by optical communication from a transmitter having a light-emitting diode (LED) provided on the rotating frame 17 to a receiver having a photodiode provided on a non-rotating part of the gantry device 10 (for example, a fixed frame not shown), and is transferred to the console device 40 by the receiver. The method of transmitting the detection data from the rotating frame 17 to the non-rotating part is not limited to the method using optical communication described above, and any non-contact type transmission method may be adopted. The rotating frame 17 is not limited to an annular member, and may be an arm-like member as long as it can support and rotate the X-ray tube device 11, etc.

[0026] The X-ray CT device 1 is, for example, a Rotate / Rotate-type X-ray CT device (third generation CT) in which the X-ray tube device 11 and the reference detector 20, and the X-ray detector 15 are both supported by a rotating frame 17 and rotate around the patient P, but is not limited to this and may be a Stationary / Rotate-type X-ray CT device (fourth generation CT) in which a plurality of X-ray detection elements arranged in a circular ring shape are fixed to a fixed frame and the X-ray tube device 11 rotates around the patient P.

[0027] The control device 18 receives an input signal from an input interface (not shown) such as an operation switch attached to the gantry 10 or an input interface 43 attached to the console device 40, and controls the operations of the gantry 10 and the bed device 30. The control device 18 has, for example, a processing circuit having a processor such as a CPU (Central Processing Unit), and a drive mechanism including, for example, a motor and an actuator, for moving the gantry 10, rotating the rotating frame 17 included in the gantry 10, and moving the bed device 30. In the embodiment, the case where the control device 18 is provided in the gantry 10 is shown, but the control device 18 may be provided in the console device 40.

[0028] The control device 18, for example, rotates the rotating frame 17, tilts the gantry 10, moves the housing of the gantry 10 (hereinafter also simply referred to as the "gantry 10") horizontally toward the top plate 33 of the bed 30 (Z-axis direction), and moves the top plate 33 of the bed 30 up and down in the Y-axis direction (which may include lateral movement in the X-axis direction and rotational movement around the Z-axis). When tilting the gantry 10, the control device 18 tilts the rotating frame 17 about an axis parallel to the Z-axis direction based on an inclination angle (tilt angle) input to an input interface (not shown) or an input interface 43. The control device 18 grasps the inclination angle of the rotating frame 17 based on the output of a sensor (not shown) or the like. The control device 18 provides the inclination angle of the rotating frame 17 to the processing circuit 50 at any time.

[0029] The control device 18 controls the collection of detection data by the DAS16 and the collection of reference detection data by the DAS21. More specifically, the control device 18 controls the period during which the integrators included in the DAS16 and DAS21 integrate the electric signals and the timing for the A / D converters included in the DAS16 and DAS21 to convert the electric signals indicating the integration results into digital signals. The control device 18 outputs timing signals for controlling the components included in each of the DAS16 and DAS21. The control of the DAS16 and DAS21 by the control device 18 will be described in detail later. The control device 18 may control the generation of reference data based on the reference detection data by the DAS16. The control device 18 is an example of a "control unit".

[0030] The bed device 30 is a device that places and moves the patient P to be scanned and introduces the patient P into the rotating frame 17 of the gantry device 10. The bed device 30 includes, for example, a base 31, a bed driving device 32, a top plate 33, and a support frame 34. The base 31 includes a housing that supports the support frame 34 so that the support frame 34 can move in the vertical direction (up and down direction). The bed driving device 32 includes a motor and an actuator. The bed driving device 32 moves the top plate 33 on which the patient P is placed in the up and down direction (Y-axis direction). The bed driving device 32 may move the top plate 33 on which the patient P is placed laterally in the horizontal direction (X-axis direction) or rotate around the Z-axis. The bed driving device 32 may move the top plate 33 on which the patient P is placed in the longitudinal direction of the top plate 33 (Z-axis direction) along the support frame 34. When the X-ray CT device 1 is a gantry-moving type X-ray CT device, the movement amount by which the bed driving device 32 moves the top plate 33 in the longitudinal direction may be an amount that allows a part of the patient P that is not introduced inside the rotating frame 17 to be introduced inside the rotating frame 17 even when the control device 18 moves the gantry device 10 to the maximum horizontal direction, that is, an amount of movement that compensates for the horizontal movement amount of the gantry device 10. When the gantry device 10 is movable in the Z-axis direction, the bed driving device 32 may move the gantry device 10 so that the rotating frame 17 comes around the patient P. The bed driving device 32 may be configured to move both the gantry device 10 and the top plate 33. The top plate 33 is a plate-shaped member on which the patient P is placed. The X-ray CT device 1 may be an apparatus of a type in which the patient P is scanned in a standing or sitting position. In this case, the X-ray CT apparatus 1 has a subject support mechanism instead of the bed device 30, and the gantry device 10 rotates the rotating frame 17 about an axial direction perpendicular to the floor surface.

[0031] The console device 40 includes, for example, a memory 41, a display 42, an input interface 43, and a processing circuit 50. In this embodiment, the console device 40 is described as being separate from the gantry device 10, but the gantry device 10 may include some or all of the components of the console device 40.

[0032] The memory 41 is realized by, for example, a semiconductor memory element such as a ROM (Read Only Memory), a RAM (Random Access Memory), a flash memory, a hard disk drive (HDD), an optical disk, etc. The memory 41 stores, for example, detection data output by the DAS 16, reference detection data output by the DAS 21, projection data generated based on the detection data, a reconstructed image, a CT image, and other data.

[0033] The display 42 displays various types of information. For example, the display 42 displays images such as reconstructed images and CT images generated by the processing circuit 50, and GUI (Graphical User Interface) images that accept various operations by an operator (such as a doctor or technician) of the X-ray CT apparatus 1. The display 42 is, for example, a Liquid Crystal Display (LCD), a CRT (Cathode Ray Tube) display, or an organic EL (Electroluminescence) display. The display 42 may be provided on the gantry device 10.

[0034] The input interface 43 accepts various input operations by the operator of the X-ray CT device 1, and outputs an electric signal indicating the contents of the accepted input operation to the processing circuit 50. For example, the input interface 43 accepts input operations such as collection conditions when collecting detection data, generation conditions when generating projection data, reconstruction conditions when reconstructing a reconstructed image, and image processing conditions when generating a post-processed image from the reconstructed image. The input interface 43 is realized by, for example, a mouse, a keyboard, a touch panel, a trackball, a switch, a button, a joystick, a camera, an infrared sensor, a microphone, and the like. The input interface 43 may be provided on the gantry 10 as an operation switch or the like, with a function of accepting some of the input operations (particularly, a function of horizontally moving the housing of the gantry 10). In this specification, the input interface 43 is not limited to only those having physical operation parts such as a mouse and a keyboard. For example, an electric signal processing circuit that receives an electric signal corresponding to an input operation from an external input device provided separately from the device and outputs the electric signal to a control circuit is also included as an example of the input interface.

[0035] The processing circuitry 50 controls the overall operation of the X-ray CT apparatus 1. The processing circuitry 50 executes, for example, a system control function 51, a pre-processing function 52, a reconstruction processing function 53, an image processing function 54, a display control function 55, and the like. The processing circuitry 50 realizes these functions by, for example, a hardware processor executing a program (software) stored in the memory 41.

[0036] The hardware processor means a circuit such as a CPU, a graphics processing unit (GPU), an application specific integrated circuit (ASIC), a programmable logic device (for example, a simple programmable logic device (SPLD) or a complex programmable logic device (CPLD), or a field programmable gate array (FPGA)). Instead of storing a program in the memory 41, the program may be directly built into the circuit of the hardware processor. In this case, the hardware processor realizes a function by reading and executing the program built into the circuit. The hardware processor is not limited to being configured as a single circuit, and may be configured as one hardware processor by combining multiple independent circuits to realize each function. Multiple components may be integrated into one hardware processor to realize each function. Multiple components may be built into one dedicated LSI to realize each function. Here, the program (software) may be stored in advance in a storage device (storage device having a non-transient storage medium) constituting a storage device such as a ROM, RAM, a semiconductor memory element such as a flash memory, or a hard disk drive, or may be stored in a removable storage medium (non-transient storage medium) such as a DVD or CD-ROM, and may be installed in the storage device of the console device 40 by mounting the storage medium in a drive device of the console device 40. The program (software) may be downloaded in advance from another computer device via a network and installed in the storage device of the console device 40. The program (software) installed in the storage device of the console device 40 may be transferred to a processing circuit of the control device 18 and executed.

[0037] Each component of the console device 40 or the processing circuit 50 may be distributed and realized by multiple pieces of hardware. The processing circuit 50 may be realized by a processing device capable of communicating with the console device 40, instead of being a configuration provided in the console device 40. The processing device is, for example, a workstation connected to one X-ray CT device, or a device (for example, a cloud server) connected to multiple X-ray CT devices and collectively executing processing equivalent to that of the processing circuit 50 described below. In other words, the configuration of this embodiment can also be realized as an X-ray CT inspection system (medical diagnostic system) in which an X-ray CT device and other processing devices are connected via a network.

[0038] The system control function 51 controls various functions of the processing circuit 50 based on, for example, an input operation received by the input interface 43 .

[0039] The pre-processing function 52 generates correction data (reference data) for comparison (reference) used to correct the detection data collected by the DAS16 based on the reference detection data output by the DAS21, and generates projection data by performing pre-processing on the detection data output by the DAS16 using the generated reference data. When the DAS21 generates reference data, the pre-processing function 52 generates projection data by performing pre-processing on the detection data output by the DAS16 using the reference data generated by the DAS21. The pre-processing includes, for example, logarithmic conversion processing, offset correction processing, sensitivity correction processing between channels, and beam hardening correction. The pre-processing function 52 stores the generated projection data in the memory 41.

[0040] The reconstruction processing function 53 performs a predetermined reconstruction process such as a filtered back projection method or an iterative reconstruction method on the projection data generated by the pre-processing function 52 to generate a reconstructed image, and stores the generated reconstructed image in the memory 41.

[0041] The image processing function 54 converts the reconstructed image into a three-dimensional image (CT image) or a cross-sectional image of an arbitrary cross section by a known method based on an input operation received by the input interface 43. The conversion into a three-dimensional image may be performed by the pre-processing function 52.

[0042] The processing circuitry 50, or the pre-processing function 52 (which may include the reconstruction processing function 53 and the image processing function 54) provided in the processing circuitry 50, is an example of an "image generating section."

[0043] The display control function 55 controls the display mode of the display 42. For example, the display control function 55 controls the display 42 to display a reconstructed image generated by the processing circuitry 50, a GUI image for accepting various operations by the operator of the X-ray CT apparatus 1, and the like.

[0044] With this configuration, the X-ray CT device 1 irradiates the patient P with X-rays generated by the X-ray tube device 11 to capture (scan) the patient P. The X-ray CT device 1 can scan the patient P in various ways, such as helical scan, conventional scan, and step-and-shoot. Helical scan is a way to scan the patient P in a spiral shape by rotating the rotating frame 17 while moving the top plate 33. Conventional scan is a way to scan the patient P in a circular orbit by rotating the rotating frame 17 while keeping the top plate 33 stationary. Step-and-shoot is a way to move the position of the top plate 33 at regular intervals to perform conventional scans in multiple scan areas.

[0045] (First embodiment) Next, the configuration of the DAS21 included in the X-ray CT apparatus 1 and the timing of collecting reference detection data in the DAS21 will be described. Fig. 2 is a diagram showing an example of a circuit configuration of the correction detector (DAS21) according to the first embodiment. Fig. 3 is a timing chart showing an example of the operation timing in the correction detector (DAS21) according to the first embodiment.

[0046] [Circuit configuration of the correction detector] First, the circuit configuration of the DAS21 will be described with reference to Fig. 2. Fig. 2 shows a schematic circuit configuration of the DAS21. Fig. 2 also shows an X-ray detection element PD (photosensor) provided in a reference detector 20 that outputs an electrical signal collected by the DAS21 as reference detection data. The X-ray detection element PD accumulates electric charges according to the amount of incident X-rays, and outputs the accumulated electric charges. The DAS21 includes an amplifier Amp, a capacitor Ci, a switch SWi, a switch SWs, a capacitor Cs, and an A / D converter ADC.

[0047] The capacitor Ci holds the electric charge accumulated and output by the X-ray detection element PD during the period when the switch SWi is in the OFF state (open state) by the timing signal Reset. On the other hand, when the switch SWi is in the ON state (closed state) by the timing signal Reset, both ends of the capacitor Ci are shorted via the switch SWi, and the held electric charge is discarded (i.e., the electric charge is reset). The amplifier Amp amplifies the electric charge held in the capacitor Ci and outputs an analog electric signal (hereinafter referred to as an "amplified signal") having a voltage value representing the amount of electric charge held in the capacitor Ci. That is, in the DAS21, an integrator is formed by the capacitor Ci and the switch SWi, and the electric charge output by the X-ray detection element PD during the period when the switch SWi is in the OFF state is integrated and held in the capacitor Ci, and the amplifier Amp performs charge-voltage conversion (hereinafter referred to as "QV conversion"), which converts the electric charge into an amplified signal (an amplified signal representing the voltage value VCi across the capacitor Ci) representing the amount of electric charge held (integrated) in the capacitor Ci.

[0048] When the switch SWs is turned ON by the timing signal Sample, it transfers the charge-voltage converted (QV converted) amplified signal to the capacitor Cs. The A / D converter ADC performs analog / digital conversion on the analog amplified signal transferred to the capacitor Cs, and outputs it to the console device 40 as reference detection data representing the magnitude of the analog amplified signal transferred to the capacitor Cs. In the DAS21, the timing signal Sample turns the switch SWs ON even at a timing in the middle of integrating the charge from the X-ray detection element PD in the integrator, and the amplified signal representing the amount of charge accumulated up to that point is transferred to the capacitor Cs. Therefore, the DAS21 outputs reference detection data representing the magnitude of the amplified signal (voltage value VCi) at the time of transfer to the capacitor Cs.

[0049] The timing signals Reset and Sample may be generated by the DAS 21 itself within each view period, for example based on a view timing VT generated by the controller 18 and input to the DAS 21 to control the timing of the view period.

[0050] The X-ray detection element PD is an example of a "first detection element." The configuration of the capacitor Ci and the switch SWi (which may include the amplifier Amp) is an example of an "integration circuit." The A / D converter ADC is an example of an "analog / digital converter." The amplified signal is an example of a "second signal."

[0051] [Operation of the correction detector] Next, the timing of the operation in the DAS21 will be described with reference to Fig. 3. Fig. 3 shows the relationship between the readout timing of the electrical signals for two X-ray projection periods, i.e., two view periods (view periods V1 and V2), and the period during which the DAS21 collects the electrical signals as reference detection data. In Fig. 3, the period from the view timing VT to the next view timing VT is the view period V. In each view period V, the DAS16 reads out electrical signals from each X-ray detection element arranged in the X-ray detection element row of the X-ray detector 15, performs QV conversion and analog / digital conversion, and collects detection data for each X-ray detection element row. Meanwhile, in each view period V, the DAS21 reads out electrical signals from the X-ray detection elements PD of the reference detector 20, performs QV conversion and analog / digital conversion, and collects reference detection data corresponding to the X-ray detection element row of the X-ray detector 15.

[0052] FIG. 3 shows an example of a case where the DAS21 divides the view period V into five periods, reads out electrical signals from the X-ray detection elements PD in each period (hereinafter referred to as the "division period"), performs QV conversion and analog / digital conversion, and collects reference detection data that is the result of the analog / digital conversion obtained in each division period. FIG. 3 also shows an example of a range of reference detection data used when generating reference data corresponding to the X-ray detection element row of the X-ray detector 15. In the following description, it is assumed that the DAS21 generates reference data based on the collected reference detection data. Furthermore, for comparison, FIG. 3 also shows an example of the timing at which a conventional DAS that performs sequential readout collects reference detection data. In the following description, it is assumed that the DAS21 or the conventional DAS generates reference data based on the collected reference detection data.

[0053] First, the operation timing of the conventional DAS shown for comparison to collect reference detection data will be described. Here, the circuit configuration of the conventional DAS is assumed to be similar to the circuit configuration of the DAS 21 shown in FIG. 2. The operation of the components (more specifically, the switches SWi, SWs, and A / D converter ADC) included in the conventional DAS is assumed to be controlled by the control device 18. The voltage value VCi(CT) shown in FIG. 3 is the voltage value across the capacitor Ci included in the conventional DAS.

[0054] In the conventional DAS, first, at the first timing t0 when the view period V1 starts, the control device 18 turns the switch SWi to the ON state by the timing signal Reset to reset the charge held in the capacitor Ci. FIG. 3 shows a state in which the charge held in the capacitor Ci is reset, and the voltage value VCi (CT) becomes 0 [V]. At this time, the control device 18 turns the switch SWs to the OFF state by the timing signal Sample. After that, the control device 18 turns the switch SWi to the OFF state by the timing signal Reset to hold the charge output by the X-ray detection element PD in the capacitor Ci. FIG. 3 shows a state in which the voltage value VCi (CT) gradually increases in the negative direction by holding the negative charge output by the X-ray detection element PD in the capacitor Ci. As a result, the amplifier Amp outputs an amplified signal representing the amount of charge held in the capacitor Ci. That is, in the conventional DAS, the charge held (integrated) in the capacitor Ci in each division period is QV converted and output.

[0055] Thereafter, at timing t1 when the division period ends, the control device 18 turns switch SWs to the ON state by the timing signal Sample, and transfers the amplified signal that has been integrated and QV converted by capacitor Ci up until this timing t1 to capacitor Cs. As a result, the A / D converter ADC performs analog / digital conversion on the amplified signal transferred to capacitor Cs, and outputs the resulting analog / digital converted data AD1 as reference detection data. Then, the control device 18 turns switch SWs to the OFF state by the timing signal Sample, and turns switch SWi to the ON state by the timing signal Reset, thereby resetting the charge held in capacitor Ci again.

[0056] In the conventional DAS, the control device 18 repeats such control. As a result, the conventional DAS obtains analog / digital conversion data AD for each divided period as reference detection data. In FIG. 3, each divided period is treated as a period for QV conversion, and QV1 to QV 10 The analog-to-digital converted data AD1 to AD 10 This shows that.

[0057] Then, the conventional DAS generates reference data corresponding to the X-ray detection element rows of the X-ray detector 15 based on the respective analog / digital converted data AD. At this time, the conventional DAS generates the reference data by taking a moving average of the reference detection data (analog / digital converted data AD) obtained in each of the five divided periods into which the view period V is divided. For example, when the conventional DAS generates the reference data Ref B When generating (collecting), the result of adding up the analog / digital conversion data AD2 to AD6 is called the reference data Ref BSimilarly, in a conventional DAS, the results of adding the corresponding analog-to-digital conversion data AD are generated as the respective reference data Ref.

[0058] In this way, in the conventional DAS, analog / digital conversion data AD (reference detection data) is collected for each divided period according to the control of the control device 18, and the corresponding analog / digital conversion data AD is added to generate reference data Ref for the corresponding X-ray detection element row.

[0059] Next, a description will be given of the operation timing for collecting the reference detection data by the DAS 21. The voltage value VCi shown in FIG.

[0060] In the DAS 21, the control device 18 first turns the switch SWi to the ON state by the timing signal Reset at the first timing t0 when the view period V1 starts, to reset the charge held in the capacitor Ci, in the same manner as when controlling the conventional DAS. FIG. 3 shows a state in which the voltage value VCi becomes 0 [V] as a result of the charge held in the capacitor Ci being reset. At this time, the control device 18 turns the switch SWs to the OFF state by the timing signal Sample, in the same manner as when controlling the conventional DAS. Thereafter, the control device 18 turns the switch SWi to the OFF state by the timing signal Reset, to hold the charge output by the X-ray detection element PD in the capacitor Ci, in the same manner as when controlling the conventional DAS. FIG. 3 shows a state in which the voltage value VCi gradually increases in the negative direction by holding the negative charge output by the X-ray detection element PD in the capacitor Ci. As a result, the amplifier Amp outputs an amplified signal (amplified signal converted into QV) representing the amount of charge held (integrated) in the capacitor Ci.

[0061] Thereafter, at timing t1 when the division period ends, the control device 18 turns the switch SWs to the ON state by the timing signal Sample, in the same manner as when controlling the conventional DAS, and transfers the amplified signal that has been integrated and QV converted by the capacitor Ci until this timing t1 to the capacitor Cs. As a result, the A / D converter ADC performs analog / digital conversion on the amplified signal transferred to the capacitor Cs, and outputs the resulting analog / digital conversion data AD1 as reference detection data. Then, the control device 18 turns the switch SWs to the OFF state by the timing signal Sample, in the same manner as when controlling the conventional DAS. However, in the DAS21, the control device 18 maintains the switch SWi in the OFF state by the timing signal Reset. In other words, when controlling the DAS21, the control device 18 does not reset the charge held in the capacitor Ci at the start timing of each division period, but continues to hold (integrate) the charge output by the X-ray detection element PD in the capacitor Ci. In other words, in the DAS 21, during each view period V, the charge output by the X-ray detection element PD is held (integrated) in the capacitor Ci.

[0062] In the DAS21, the control device 18 repeats such control within the same view period V. That is, in the DAS21, the control device 18 causes only the transfer to the capacitor Cs of the amplified signal that has been integrated and QV converted by the capacitor Ci in response to the timing signal Sample at the end of each division period. Then, the A / D converter ADC performs analog / digital conversion on the amplified signal that represents the amount of charge held (integrated) in the capacitor Ci, and outputs the resulting analog / digital converted data AD as reference detection data.

[0063] Thereafter, at the first timing t5 when the next (second) view period V2 starts, the control device 18 turns on the switch SWi by the timing signal Reset to reset the charge held in the capacitor Ci, in the same way as at the first timing t0 when the first (first) view period V1 starts. Thereafter, in the same way, during the same view period V, the control device 18 causes the charge output by the X-ray detection element PD to be held (integrated) in the capacitor Ci, and at the first timing t when the next (third or later) view period V3 (not shown) starts, the control device 18 resets the charge held in the capacitor Ci, and obtains the analog-to-digital converted data AD from the first timing to each divided period in each view period V as reference detection data. FIG. 3 shows the period (QV V1 ), and in this view period V1, analog / digital conversion data AD1 to AD5 are obtained at timings t1 to t5 at which the respective divided periods end, and the next (second) view period V2 is subjected to QV conversion (QV V2 ) in this view period V2, analog / digital conversion data AD6 to AD 10 This shows the state in which

[0064] Then, in the DAS21, similar to the conventional DAS, reference data corresponding to the X-ray detection element rows of the X-ray detector 15 is generated based on each analog / digital conversion data AD (reference detection data). However, in the DAS21, the amount of charge held (integrated) in the capacitor Ci represented by each analog / digital conversion data AD is different from that in the conventional DAS. For this reason, in the DAS21, for example, reference data Ref B When generating (collecting), the result of the calculation of the following formula (1) is used as the reference data Ref B In the DAS 21, for example, reference data Ref corresponding to the X-ray detection element rows arranged in row C in the slice direction is generated as CWhen generating (collecting), the result of the calculation of the following formula (2) is used as the reference data Ref C Generate it as:

[0065] Ref B =AD5 - AD1 + AD6 (1)

[0066] Ref C =AD5 - AD2 + AD7 (2)

[0067] Similarly, the DAS 21 performs calculations using the corresponding analog / digital converted data AD based on the same concepts as the above equations (1) and (2), and generates the results as the respective reference data Ref.

[0068] In this way, the DAS 21 collects analog / digital converted data AD (reference detection data) in each divided period under the control of the control device 18, and generates reference data Ref for the corresponding X-ray detection element array by performing a calculation using the corresponding analog / digital converted data AD. Fig. 3 shows how each reference data Ref collected in view period V1 is used to correct detection data of the corresponding X-ray detection element array in view period V2.

[0069] View Period V1(QV V1 ) and view period V2 (QV V2 ), that is, the period of QV conversion in the DAS 21 is an example of a "first period." 10 The period during which the A / D converter ADC outputs the amplified signal transferred to the capacitor Cs, that is, the period during which the A / D converter ADC performs analog-to-digital conversion of the amplified signal transferred to the capacitor Cs, is an example of a "second period."

[0070] As described above, in the DAS21, the charge held in the capacitor Ci is not reset at the start timing of each divided period into which the view period is divided, and the charge output by the X-ray detection element PD is held (integrated) in the capacitor Ci during each view period V. As a result, even if the readout of electrical signals from the X-ray detector 15 by the DAS16 in the X-ray CT device 1 is accelerated, the DAS21 does not need to accelerate the timing of resetting the charge held (integrated) in the capacitor Ci by the switch SWi of the DAS21 in accordance with the readout of electrical signals from the X-ray detector 15 by the DAS16. As a result, in the DAS21, it is possible to reduce concerns associated with the acceleration of the readout of electrical signals from the X-ray detector 15 by the DAS16, such as the inclusion of noise in the amplified signal subjected to QV conversion by switching the switch SWi between the ON state and the OFF state at high speed.

[0071] Second embodiment [Circuit configuration of the correction detector] Next, another configuration of the DAS21 included in the X-ray CT apparatus 1 will be described. FIG. 4 is a diagram showing an example of a circuit configuration of a correction detector (DAS21) according to a second embodiment. In the following description, the DAS21 of the second embodiment is referred to as "DAS21a". FIG. 4 shows a schematic circuit configuration in the DAS21a. FIG. 4 also shows an X-ray detection element PD (photosensor) included in the reference detector 20 that outputs an electric signal collected by the DAS21a as reference detection data. The DAS21a includes an amplifier Amp, a capacitor Ci, a switch SWi, a plurality of switches SWs (switches SWs-1 to SWs-n (n is a natural number)), a plurality of capacitors Cs (capacitors Cs-1 to Cs-n), and a plurality of A / D converters ADC (A / D converters ADC-1 to ADC-n).

[0072] In the DAS21a, the switch SWs, the capacitor Cs, and the A / D converter ADC included in the DAS21 shown in Fig. 2 are each composed of a plurality of components. Each of the components included in the DAS21a is similar to the corresponding component included in the DAS21.

[0073] In the DAS21a, the switch SWs, the capacitor Cs, and the A / D converter ADC form a set. More specifically, in the DAS21a, the switch SWs-1, the capacitor Cs-1, and the A / D converter ADC-1 form a set, the switch SWs-2, the capacitor Cs-2, and the A / D converter ADC-2 form a set, and the switch SWs-n, the capacitor Cs-n, and the A / D converter ADC-n form a set. The number of sets in the DAS21a may be any number necessary to ensure the necessary performance in the X-ray CT device 1 including the DAS21a. In other words, the number of sets in the DAS21a may be any number as long as the DAS16 can collect reference detection data and generate reference data used for correcting detection data collected from the X-ray detector 15 in order to capture a CT image with a resolution necessary for diagnosing the patient P. For example, the number of sets in the DAS21a is the same as the number of divided periods into which the view period is divided. More specifically, when the view period V is divided into five divided periods in the same manner as in the operation of the DAS 21 shown in Fig. 3, "n" is "5." Then, in the DAS 21a, each group obtains analog / digital converted data AD of the corresponding divided period.

[0074] For example, consider a case where the view period V is divided into five divided periods in the same manner as the operation of the DAS 21 shown in Fig. 3. In this case, when the control device 18 turns on the switch SWs-1 by the timing signal Sample-1 at the timing t1 and causes the amplified signal representing the amount of charge integrated in the capacitor Ci from the timing t0 to t1 to be transferred to the capacitor Cs-1, the A / D converter ADC-1 obtains analog / digital conversion data AD1 (reference detection data). Similarly, when the control device 18 turns on the switch SWs-2 by the timing signal Sample-2 at the timing t2 and causes the amplified signal representing the amount of charge integrated in the capacitor Ci from the timing t0 to t2 to be transferred to the capacitor Cs-2, the A / D converter ADC-2 obtains analog / digital conversion data AD2 (reference detection data). Similarly, when the control device 18 turns on the switch SWs-5(n) by the timing signal Sample-5(n) at the timing t5 and transfers the amplified signal representing the amount of charge integrated in the capacitor Ci between the timings t0 and t5 to the capacitor Cs-5(n), the A / D converter ADC-5(n) converts the analog / digital converted data AD 5(n) (Reference detection data) is obtained.

[0075] As a result, DAS21a, like DAS21, generates the results of calculations performed using the corresponding analog / digital conversion data AD (reference detection data) based on the same concept as equations (1) and (2) above as reference data Ref corresponding to each of the X-ray detection element rows of the X-ray detector 15.

[0076] The A / D converters ADC-1 to ADC-n are an example of the "plurality of analog / digital converters."

[0077] As described above, in the DAS21a, similar to the DAS21, the charge held in the capacitor Ci is not reset at the start timing of each divided period into which the view period is divided, and the charge output by the X-ray detection element PD is held (integrated) in the capacitor Ci during each view period V. As a result, in the DAS21a, similar to the DAS21, even if the readout of the electrical signal from the X-ray detector 15 by the DAS16 in the X-ray CT device 1 is accelerated, it is not necessary to accelerate the timing of resetting the charge held (integrated) in the capacitor Ci by the switch SWi provided in the DAS21a in accordance with the readout of the electrical signal from the X-ray detector 15 by the DAS16. As a result, in the DAS21a, similar to the DAS21, it is possible to reduce concerns associated with the acceleration of the readout of the electrical signal from the X-ray detector 15 by the DAS16, such as the inclusion of noise in the amplified signal subjected to QV conversion by switching the switch SWi between the ON state and the OFF state at high speed.

[0078] Furthermore, the DAS21a includes a plurality of sets of switches SWs, capacitors Cs, and A / D converters ADC. For example, the DAS21a includes sets of switches SWs, capacitors Cs, and A / D converters ADC, the number of which corresponds to each of the divided periods into which the view period is divided. This makes it possible to reduce concerns in the DAS21a about a decrease in response speed, an increase in noise, a change to an A / D converter ADC with a larger dynamic range, and the like, which occur when the capacitors Ci have a larger capacity in order to hold (integrate) the charges output by the X-ray detection elements PD during the view period V.

[0079] As described above, in the DAS21 (including DAS21a) of each embodiment, even when the DAS16 reads out an electrical signal from the X-ray detector 15 by dividing the view period into a plurality of divided periods and reading out the electrical signal sequentially, the DAS21 (including DAS21a) does not reset the electrical signal (charge) read out from the reference detector 20 for each divided period, but continues to hold (integrate) the electrical signal (charge) read out from the reference detector 20 during the view period. Then, the DAS21 (including DAS21a) of each embodiment collects reference detection data based on the electrical signal (charge) that is continuously held (integrated). Then, the DAS21 (including DAS21a) of each embodiment performs a calculation using the collected reference detection data, thereby generating correction data (reference data) for comparison (reference) used to correct the detection data collected by the DAS16. As a result, in the DAS21 (including DAS21a) of each embodiment, even if the readout of an electrical signal from the X-ray detector 15 by the DAS16 in the X-ray CT device 1 is accelerated, it is not necessary to accelerate the timing of resetting the electrical signal (charge) read out from the reference detector 20 in accordance with the readout of the electrical signal from the X-ray detector 15 by the DAS16. As a result, in the DAS21 (including DAS21a) of each embodiment, it is possible to reduce concerns associated with the acceleration of the readout of an electrical signal from the X-ray detector 15 by the DAS16, such as noise caused by operating at high speed a component that resets the electrical signal (charge) read out from the reference detector 20.

[0080] In the above-mentioned embodiment, the case where the DAS16 divides the view period into five divided periods has been described as an example. In other words, in the above-mentioned embodiment, the time (divided period) during which the A / D converter ADC outputs the analog / digital converted data AD obtained by analog / digital converting the amplified signal as reference detection data is shorter than the time (view period) during which the DAS21 reads out the electrical signal from the reference detector 20 and QV converts it into an amplified signal. In other words, in the above-mentioned embodiment, the case where the period of the analog / digital conversion is shorter than the period of the QV conversion in the DAS21 has been described as an example. However, the number of divided periods (number of divided periods) into which the view period is divided when the DAS16 reads out the electrical signal from the X-ray detector 15 may be at least two or more, and it is considered that the number of divided periods and the period (time) can be determined according to the number of X-ray detection elements and X-ray detection element rows arranged in the X-ray detector 15 provided in the X-ray CT device 1. Even in this case, in the DAS21, as long as the relationship between the QV conversion period (time) and the analog / digital conversion period (time) is "(QV conversion period (time))>(analog / digital conversion period (time))", the number of divisions of the view period (number of division periods) and the length of each period (time) are not limited. Even if the number of divisions of the view period (number of division periods) and the period (time) are different when the DAS16 reads out an electrical signal from the X-ray detector 15, the configuration, operation (control by the control device 18), and calculation method of the DAS21 (including DAS21a) may be equivalent to the configuration, operation, and calculation method of the DAS21 (including DAS21a) described in the above embodiment, and can be easily considered based on the description of the above embodiment. Therefore, detailed description of the configuration, operation, and calculation method of the DAS21 (including DAS21a) in the case where the number of divisions of the view period (number of division periods) and the period (time) are different when the DAS16 reads out an electrical signal from the X-ray detector 15 is omitted.

[0081] According to at least one of the embodiments described above, a correction detector (configured as 20 and 21) is mounted on an X-ray CT device (1) that generates an image of a subject (P) (e.g., a reconstructed image or a CT image) based on detection data obtained by periodically detecting X-rays irradiated from an X-ray tube (11) and passing through the subject (P), and detects correction detection data (reference detection data) for generating correction data (reference data) used to correct the detection data, the correction detector including a first detection element (PD) that detects the original X-rays irradiated from the X-ray tube before passing through the subject and outputs a first signal (electrical signal) representing the intensity of the original X-rays, and a first detection element (PD) that detects the original X-rays irradiated from the X-ray tube before passing through the subject and outputs a first signal (electrical signal) representing the intensity of the original X-rays based on a period (view period) for detecting the detection data. By having an integration circuit (which may include Ci, SWi, and Amp) that integrates and holds an electric charge corresponding to the first signal in a period (a period of QV conversion) and outputs a second signal (amplified signal) based on the held electric charge, and an analog-to-digital converter (ADC) that performs analog-to-digital conversion of the second signal in a second period (a period for analog-to-digital conversion) shorter than the first period and outputs the correction detection data representing the magnitude of the second signal, it is possible to provide a correction detector that corresponds to the increased speed of an X-ray CT device equipped with a data collection system (16) that reads out electrical signals from an X-ray detector (15) by sequential readout, and an X-ray CT device equipped with this correction detector.

[0082] 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, and modifications 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]

[0083] 1···X-ray CT device, 10···Ground device, 11···X-ray tube device, 12···Wedge, 13···Collimator, 14···X-ray high voltage device, 15···X-ray detector, 16···Data acquisition system (DAS), 17···Rotating frame, 18···Control device, 20···Reference detector, 21···Data acquisition system (DAS), 30···Couch device, 31···Base, 32···Couch drive device, 33···Top plate, 34···Support frame, 40···Console device, 41···Memory, 42···Display, 43···Input interface, 50···Processing circuit, 51···System control function, 52···Preprocessing function, 53···Reconstruction processing function, 54···Image processing function, 55···Display control function

Claims

1. A correction detector is mounted in an X-ray CT apparatus that generates an image of a subject based on detection data obtained by periodically detecting X-rays irradiated from an X-ray tube and passing through the subject, and detects correction detection data for generating correction data used to correct the detection data, a first detection element that detects the original X-rays emitted from the X-ray tube before passing through the subject and outputs a first signal representing the intensity of the original X-rays; an integration circuit that integrates and holds an electric charge corresponding to the first signal during a first cycle based on a period for detecting the detection data, and outputs a second signal based on the held electric charge; an analog / digital converter that performs analog / digital conversion on the second signal in a second period that is shorter than the first period, and outputs the correction detection data that represents the magnitude of the second signal; A correction detector comprising:

2. a plurality of the analog-to-digital converters connected in parallel to the integrating circuit; and outputting the correction detection data obtained by analog-to-digital conversion of the second signal output by the integration circuit when the number of the second periods repeated within the first period is different in each of the analog-to-digital conversions.

2. The corrective detector of claim 1.

3. a time period of the first period is the same as a period for detecting the detection data, The time of the second cycle is a time of a divided period obtained by dividing the time of the first cycle into a plurality of periods.

3. The correction detector according to claim 1 or 2.

4. 1. An X-ray CT apparatus for generating an image of a subject based on detection data obtained by periodically detecting X-rays irradiated from an X-ray tube and passing through the subject, comprising: a correction detector comprising: a first detection element that detects the original X-rays irradiated from the X-ray tube before passing through the subject and outputs a first signal representing the intensity of the original X-rays; an integration circuit that integrates and holds an electric charge corresponding to the first signal in a first cycle based on a period for detecting the detection data and outputs a second signal based on the held electric charge; and an analog / digital converter that analog / digital converts the second signal in a second cycle shorter than the first cycle and outputs correction detection data representing a magnitude of the second signal, the correction detector detecting the correction detection data for generating correction data used to correct the detection data; a detector including a plurality of second detection elements arranged to detect the X-rays that have passed through the subject and output a third signal corresponding to the intensity of the X-rays; a collection unit that periodically collects the third signal in the first period and outputs the detection data based on the collected third signal; a control unit that controls at least integration and retention of charge corresponding to the first signal in the correction detector, analog / digital conversion of the second signal, and collection of the third signal in the collection unit; an image generating unit that generates the correction data based on the correction detection data, corrects the detection data based on the correction data, and generates an image of the subject; An X-ray CT apparatus comprising:

5. the detector includes a plurality of detector element rows arranged in a second direction, the plurality of second detector elements being arranged in a first direction to detect X-rays that have passed through the subject; The control unit is The third signals output by the second detection elements arranged in the detector in the collecting unit are sequentially collected during the first period while the second detection elements arranged in the detector are moved in order in the second direction; causing the correction detector to integrate and hold charge corresponding to the first signal in the first period; performing analog / digital conversion of the second signal in the correction detector for each second period obtained by dividing the first period into a plurality of periods; 5. The X-ray CT apparatus according to claim 4.

6. The image generating unit generating the correction data based on the correction detection data when the number of the second periods repeated within the first period is different; correcting the detection data output by the collecting unit with the correction data based on the correction detection data corresponding to a period during which the third signal of the detection data was collected, to generate an image of the subject.

6. The X-ray CT apparatus according to claim 5.

Images