X-ray CT device, determination method, and program

Abstract

To determine a state of an X-ray tube more efficiently.SOLUTION: An X-ray CT apparatus includes a photon counting type X-ray detector, a storage unit, an acquisition unit, and a determination unit. The photon counting type X-ray detector detects an X-ray radiated from the X-ray tube by the photon. The storage unit stores first energy spectrum information acquired by detecting the X-ray at a first timing. The acquisition unit acquires second energy spectrum information by detecting the X-ray at a second timing later than the first timing. The determination unit determines a state of the X-ray tube on the basis of the first energy spectrum information and the second energy spectrum information.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to an X-ray CT apparatus, a determination method, and a program. [Background technology]

[0002] Conventionally, a photon counting type X-ray computed tomography (PCCT) device using X-rays generated by an X-ray tube has been known. The PCCT device calculates the ratio between the count number of X-ray photons transmitted through the subject and the spectrum of the X-ray photons before transmitting through the subject (hereinafter referred to as the air irradiation spectrum) for each of a plurality of energy bins, and calculates the linear attenuation coefficient for each of a plurality of energy bins (energy bands), thereby reconstructing a cross-sectional image of the subject.

[0003] However, X-ray CT systems are sometimes equipped with X-ray tubes (hereinafter referred to as "non-standard tubes") that are designed differently from the recommended ones. Non-standard tubes have different target materials and target angles, and different filter materials and thicknesses, resulting in different air irradiation spectra. To prevent the installation of non-standard tubes, there is a method of incorporating an electronic board with an individual ID number recorded on it into the X-ray tube and matching the ID number with the system. However, this matching method has problems such as restrictions on the gantry design due to changes in the external shape and increased weight of the X-ray tube, and increased manufacturing costs.

[0004] Furthermore, with long-term use of the X-ray tube in an X-ray CT system, the anode material in the X-ray tube (hereinafter referred to as the anode material) deteriorates. This deterioration of the anode material attenuates the output of soft X-rays (low-energy X-rays with poor penetration) in the air irradiation spectrum. If the air irradiation spectrum differs, the linear attenuation coefficient cannot be derived correctly, which can cause artifacts such as CT value shifts in the reconstructed cross-sectional images. Therefore, in order to avoid CT value shifts, it was necessary to know the net air irradiation spectrum during CT scanning. Thus, in the past, it was sometimes impossible to efficiently determine the condition of the X-ray tube. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent Application Publication No. 2013 / 0083901 Summary of the Invention [Problem to be solved by the invention]

[0006] One of the problems to be solved by the present invention is to more efficiently determine the state of an X-ray tube. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem, and problems corresponding to the effects of each configuration shown in the embodiments described below can also be positioned as other problems. [Means for solving the problem]

[0007] An X-ray CT apparatus according to an embodiment includes a photon-counting X-ray detector, a storage unit, an acquisition unit, and a determination unit. The photon-counting X-ray detector detects X-rays irradiated from an X-ray tube in photon units. The storage unit stores first energy spectrum information acquired by detecting X-rays at a first timing. The acquisition unit acquires second energy spectrum information by detecting X-rays at a second timing that is later than the first timing. The determination unit determines the state of the X-ray tube based on the first energy spectrum information and the second energy spectrum information. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a configuration diagram of an X-ray CT apparatus 1 according to an embodiment. [Figure 2] FIG. 4 is a diagram showing an example of data stored in a memory 41. [Figure 3] 6 is a flowchart showing an example of a determination process for determining whether or not the replaced X-ray tube 11 is an irregular tube. [Figure 4] FIG. 10 is a diagram for explaining comparison of count values ​​of energy bins containing specific X-rays. [Figure 5] 10 is a flowchart showing a series of steps in a deterioration degree determination process. [Figure 6] FIG. 10 is a diagram for explaining acquisition of count values ​​for two different energy bins. DETAILED DESCRIPTION OF THE INVENTION

[0009] An X-ray CT apparatus, a determination method, and a program according to an embodiment will be described below with reference to the drawings. In the following embodiments, parts with the same reference numerals perform similar operations, and redundant description will be omitted as appropriate. For concrete explanation, the X-ray computed tomography apparatus according to the embodiment will be described as a photon-counting X-ray computed tomography apparatus (hereinafter referred to as an X-ray CT (Computed Tomography) apparatus) capable of performing photon-counting CT. The X-ray CT apparatus is an apparatus capable of reconstructing X-ray CT image data with a high signal-to-noise ratio by counting X-rays transmitted through a subject using a photon-counting X-ray detector (hereinafter referred to as a photon-counting X-ray detector). Note that the X-ray computed tomography apparatus according to the embodiment may have an integral type (current-mode measurement type) X-ray detector instead of the photon-counting X-ray detector.

[0010] FIG. 1 is a configuration diagram of an X-ray CT apparatus 1 according to an embodiment. The X-ray CT apparatus 1 includes, for example, a gantry 10, a bed apparatus 30, and a console apparatus 40. For convenience of explanation, FIG. 1 shows both a view of the gantry 10 from the Z-axis direction and a view of the gantry 10 from the X-axis direction, but in reality, there is only one gantry apparatus 10. In this embodiment, the rotation axis of the rotating frame 17 in a non-tilted state or the longitudinal direction of the tabletop 33 of the bed apparatus 30 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.

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

[0012] The X-ray tube 11 generates X-rays by irradiating thermions from a cathode (filament) to an anode (target) when a high voltage is applied from the X-ray high-voltage generator 14. The X-ray tube 11 includes a vacuum tube. For example, the X-ray tube 11 may be a rotating anode type X-ray tube that generates X-rays by irradiating a rotating anode with thermions. The X-ray tube 11 has a unique energy spectrum depending on the material and thickness of the X-ray filter, the material and thickness of the target, and the target angle. In the X-ray CT system 1, it is important to provide the energy spectrum expected by the system. The contrast of the scanned image changes depending on the energy spectrum, and in PCCT systems in particular, changes in the energy spectrum have a significant impact on material decomposition performance.

[0013] The wedge 12 is a filter for adjusting the amount of X-rays irradiated from the X-ray tube 11 to the subject P. The wedge 12 is a filter that transmits and attenuates the X-rays irradiated from the X-ray tube 11 so that the distribution of the X-ray dose irradiated from the X-ray tube 11 to the subject P becomes a predetermined distribution. For example, the wedge 12 is also called a wedge filter or a bow-tie filter. The wedge 12 is made by processing aluminum to have a predetermined target angle and a predetermined thickness, for example.

[0014] The collimator 13 is a mechanism for narrowing down the irradiation range of the X-rays that have passed through the wedge 12. The collimator 13 narrows down the irradiation range of the X-rays, for example, by forming a slit by combining multiple lead plates. The collimator 13 is also sometimes called an X-ray aperture.

[0015] The X-ray high voltage device 14 includes, for example, a high voltage generator and an X-ray control device. The high voltage generator includes an electric circuit including a transformer, a rectifier, etc. The high voltage generator generates a high voltage to be applied to the X-ray tube 11. The X-ray control device controls the output voltage of the high voltage generator according to the X-ray dose to be generated in the X-ray tube 11. The high voltage generator may be a type that boosts voltage using the above-mentioned transformer or may be a type that boosts voltage using an inverter. The X-ray high voltage device 14 may be provided on the rotating frame 17 or on the side of a fixed frame (not shown) of the gantry device 10. The fixed frame is a support frame that allows the rotating frame 17 to rotate. The X-ray control device controls the output voltage of the high voltage generator according to the X-ray dose to be generated in the X-ray tube 11.

[0016] The X-ray detector 15 is, for example, a photon counting detector (PCD). The X-ray detector 15 counts X-ray photons generated by the X-ray tube 11. For example, the X-ray detector 15 detects X-rays irradiated from the X-ray tube 11 and passing through the subject P on a photon-by-photon basis, and outputs an electrical signal corresponding to the X-ray dose to the DAS 16. Specifically, the X-ray detector 15 is configured to record the energy of each incident X-ray photon. The X-ray detector 15 amplifies the detected output signal and then counts the number of incident X-ray photons for each window divided according to the signal level, thereby recording the X-ray energy range in a counter and arranging it in a bin. The X-ray detector 15 has, for example, multiple detector element rows in which multiple detector elements are arranged in the channel direction along an arc centered on the focal point of the X-ray tube 11. The X-ray detector 15 has, for example, a structure in which multiple detector element rows are arranged in the slice direction (row direction).

[0017] Specifically, the X-ray detector 15 is an indirect conversion detector having, for example, a grid, a scintillator array, and a photosensor array. The scintillator array has multiple scintillators. The scintillator has scintillator crystals that output light with a photon amount corresponding to the amount of incident X-rays. The grid is arranged on the X-ray incident side of the scintillator array and has an X-ray shielding plate that has the function of absorbing scattered X-rays. The grid is sometimes called a collimator (one-dimensional collimator or two-dimensional collimator). The photosensor array has multiple photosensor groups. The photosensor group has multiple photosensors. The photosensor has the function of amplifying light received from the scintillator and converting it into an electrical signal. The photosensor is, for example, a photomultiplier tube (PMT), an avalanche photodiode (APD), or a silicon photomultiplier (SiPM). The photosensor receives light from the scintillator and outputs an electrical signal (pulse) corresponding to the incident X-ray photons. The electrical signal output from each detection element is also referred to as a detection signal. The peak value (voltage) of this electrical signal (pulse) correlates with the energy value of the X-ray photon. The X-ray detector 15 may be a direct conversion type detector having a semiconductor element that converts incident X-rays into an electrical signal. The X-ray detector 15 is an example of an X-ray detection unit.

[0018] The DAS 16 includes, for example, an amplifier, an integrator, and an A / D converter. The amplifier amplifies the electrical signal output by each X-ray detection element of the X-ray detector 15. The integrator integrates the amplified electrical signal over a view period (described below). The A / D converter converts the electrical signal indicating the integration result 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 that indicates the rotation angle of the X-ray tube 11. The view period is the period from the rotation angle corresponding to a certain view number to the rotation angle corresponding to the next view number. The DAS 16 may detect the view switching 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 a full scan is performed and X-rays are continuously emitted by the X-ray tube 11, the DAS 16 collects a group of detection data for the entire circumference (360 degrees). When a half scan is performed and X-rays are continuously emitted by the X-ray tube 11, the DAS 16 collects detection data for half the circumference (180 degrees). The DAS 16 is also an example of a data acquisition unit.

[0019] The rotating frame 17 is an annular member that supports the X-ray tube 11, wedge 12, collimator 13, and X-ray detector 15 in opposing positions. The rotating frame 17 is supported by a fixed frame so as to be rotatable around the subject P introduced inside. The rotating frame 17 also supports the X-ray high-voltage generator 14 and the DAS 16. The rotating frame 17 is rotatably supported by a non-rotating portion of the gantry device 10 (e.g., a fixed frame; not shown in FIG. 1). The rotation mechanism includes, for example, a motor that generates a rotational driving force and a bearing that transmits the rotational driving force to the rotating frame 17 to rotate it. The motor is provided in, for example, the non-rotating portion, and the bearing is physically connected to the rotating frame 17 and the motor, so that the rotating frame rotates in response to the rotational force of the motor.

[0020] The rotating frame 17 and the non-rotating portion are each provided with a non-contact or contact communication circuit, which enables communication between the unit supported by the rotating frame 17 and the non-rotating portion or a device external to the gantry 10. For example, if optical communication is used as the non-contact communication method, the detection data generated by the DAS 16 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 the non-rotating portion of the gantry 10, and the data is then transferred from the non-rotating portion to the console device 40 by the transmitter. Note that other communication methods may also be used, such as non-contact data transmission methods such as capacitive coupling and radio wave methods, as well as contact data transmission methods using slip rings and electrode brushes. The rotating frame 17 is not limited to being an annular member, but may also be an arm-like member, as long as it can support and rotate the X-ray tube 11, etc.

[0021] The X-ray CT device 1 is, for example, a Rotate / Rotate-Type X-ray CT device (third generation CT) in which both the X-ray tube 11 and the X-ray detector 15 are supported by a rotating frame 17 and rotate around the subject P, but is not limited to this and may also be a Stationary / Rotate-Type X-ray CT device (fourth generation CT) in which multiple X-ray detection elements arranged in a circular ring are fixed to a fixed frame and the X-ray tube 11 rotates around the subject P.

[0022] The control device 18 includes, for example, a processing circuit having a processor such as a CPU (Central Processing Unit), and a drive mechanism including a motor, an actuator, etc. The control device 18 receives input signals from an input interface 43 attached to the console device 40 or the gantry device 10, and controls the operations of the gantry device 10 and the bed device 30.

[0023] The control device 18, for example, rotates the rotating frame 17, tilts the gantry 10, and moves the tabletop 33 of the bed 30. When tilting the gantry 10, the control device 18 rotates the rotating frame 17 around an axis parallel to the Z-axis direction based on the inclination angle (tilt angle) input to the input interface 43. The control device 18 grasps the rotation angle of the rotating frame 17 from the output of a sensor (not shown), etc. The control device 18 also provides the rotation angle of the rotating frame 17 to the processing circuit 50 as needed. The control device 18 may be provided in the gantry 10 or in the console device 40. The control device 18 is an example of a control unit.

[0024] The bed device 30 is a device that places and moves the subject P to be scanned and introduces the subject P into the rotating frame 17 of the gantry device 10. The bed device 30 has, 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 (Y-axis 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 subject P is placed, along the support frame 34 in the longitudinal direction of the top plate 33 (Z-axis direction). The top plate 33 is a plate-shaped member on which the subject P is placed.

[0025] The bed driving device 32 may move not only the tabletop 33 but also the support frame 34 in the longitudinal direction of the tabletop 33. Alternatively, the gantry 10 may be movable in the Z-axis direction, and the rotation frame 17 may be controlled to move around the subject P by the movement of the gantry 10. Alternatively, both the gantry 10 and the tabletop 33 may be movable. The X-ray CT apparatus 1 may be an apparatus in which the subject 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 10 rotates the rotation frame 17 about an axial direction perpendicular to the floor surface. The X-ray CT apparatus 1 does not necessarily have to have the bed device 30. For example, if the opening of the X-ray CT apparatus 1 has a substantially cylindrical shape extending vertically, the subject will be imaged in an upright position, and the bed device 30 is not required.

[0026] The console device 40 includes, for example, a memory 41, a display 42, an input interface 43, a network connection circuit 44, and a processing circuit 50. In the 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.

[0027] 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, reconstructed image (CT image) data, etc. These data may be stored in an external memory with which the X-ray CT apparatus 1 can communicate, instead of (or in addition to) the memory 41. The external memory is controlled by, for example, a cloud server that manages the external memory, by the cloud server accepting a read / write request. The external memory is realized by, for example, a system called PACS (Picture Archiving and Communication Systems). PACS is a system that systematically stores images captured by various imaging diagnostic apparatuses, etc. The memory 41 is an example of a storage unit.

[0028] FIG. 2 is a diagram illustrating an example of data stored in the memory 41. As shown in FIG. 2, the memory 41 stores information such as imaging conditions 41-1, which set various conditions (scan conditions, etc.) when imaging the subject P, projection data 41-2 generated by the processing circuitry 50, reconstructed image data 41-3, sample data 41-4 used to determine differences in X-ray tube settings and the degree of deterioration, determination results 41-5, and notification information 41-6. The sample data 41-4 is first energy spectrum (irradiation spectrum) information acquired by detecting X-rays from a regular X-ray tube (regular tube) having a design recommended at a first timing. The first timing is, for example, the timing at which the X-ray CT device 1 is shipped. The shipping time may be the timing at which the device is shipped from the manufacturer to a customer, or the timing at which initial setup (initial adjustment) is performed after installation at the customer. The notification information 41-6 is information in which notification content is associated with each state of the X-ray tube determined by the determination function 59. The notification information 41-6 may also include information about the notification destination (target person).

[0029] The display 42 displays various types of information. For example, the display 42 outputs medical images (CT images) generated by the processing circuitry 50, a GUI (Graphical User Interface) that accepts various operations by the operator, and the like. The display 42 is, for example, a liquid crystal display, a CRT (Cathode Ray Tube) display, an organic EL (Electro Luminescence) display, or the like. The display 42 may be provided on the gantry device 10. The display 42 may be a desktop type, or may be a display device (for example, a tablet terminal) that can wirelessly communicate with the main body of the console device 40. The display 42 is also an example of a display unit.

[0030] The input interface 43 accepts various input operations by the operator and outputs an electrical signal indicating the content of the accepted input operation to the processing circuitry 50. For example, the input interface 43 accepts input operations such as collection conditions for collecting detection data or projection data, reconstruction conditions for reconstructing a CT image, and image processing conditions for generating a post-processed image from the CT image. For example, the input interface 43 is realized by a mouse, a keyboard, a touch panel, a trackball, a switch, a button, a joystick, a camera, an infrared sensor, a microphone, etc. The input interface 43 may be provided in the gantry device 10. Alternatively, the input interface 43 may be realized by a display device (e.g., a tablet terminal) capable of wireless communication with the main body of the console device 40.

[0031] The network connection circuit 44 includes, for example, a network card having a printed circuit board, a wireless communication module, etc. The network connection circuit 44 implements an information communication protocol according to the type of network to be connected. Examples of networks include a LAN (Local Area Network), a WAN (Wide Area Network), the Internet, a cellular network, a dedicated line, etc.

[0032] 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 preprocessing function 52, a reconstruction processing function 53, an image processing function 54, a scan control function 55, a display control function 56, an adjustment function 57, an acquisition function 58, a determination function 59, a notification function 60, etc. The processing circuitry 50 realizes these functions by, for example, a hardware processor executing a program stored in the memory 41.

[0033] The hardware processor refers to a circuit such as a CPU, a graphics processing unit (GPU), an application specific integrated circuit (ASIC), a programmable logic device (e.g., 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 memory 41, the program may be directly embedded in the circuit of the hardware processor. In this case, the hardware processor realizes its function by reading and executing the program embedded in the circuit. The hardware processor is not limited to being configured as a single circuit, but may be configured as a single hardware processor by combining multiple independent circuits to realize each function. Furthermore, multiple components may be integrated into a single hardware processor to realize each function. Furthermore, the processing circuit 50 is an example of a processing unit. The acquisition function 58 is an example of an acquisition unit. The determination function 59 is an example of a determination unit. The notification function 60 is an example of a notification unit.

[0034] Each component of the console device 40 or the processing circuitry 50 may be distributed and realized by multiple pieces of hardware. The processing circuitry 50 may not be a component of the console device 40, but may be realized by a processing device capable of communicating with the console device 40. The processing device is, for example, a workstation connected to one X-ray CT device, or a device (e.g., a cloud server) connected to multiple X-ray CT devices and collectively executing processing equivalent to that of the processing circuitry 50 described below. In other words, the configuration of this embodiment can also be realized as an X-ray CT system (medical diagnostic system) in which an X-ray CT device and other processing devices are connected via a network.

[0035] 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 .

[0036] The pre-processing function 52 performs pre-processing such as logarithmic conversion processing, offset correction processing, inter-channel sensitivity correction processing, and beam hardening correction on the detection data output by the DAS 16 to generate projection data 41-2, and stores the generated projection data 41-2 in the memory 41. Note that the data before pre-processing (detection data) and the data after pre-processing may be collectively referred to as projection data.

[0037] The reconstruction processing function 53 performs reconstruction processing using a filtered backprojection method, an iterative reconstruction method, or the like on the projection data 41-2 generated by the preprocessing function 52 to generate reconstructed image data (CT image data) 41-3, and stores the generated reconstructed image data 41-3 in the memory 41.

[0038] The image processing function 54 converts the reconstructed image data 41-3 into three-dimensional image data or cross-sectional image data of an arbitrary cross section by a known method based on an input operation received by the input interface 43. The generation of the three-dimensional image data may be performed by the reconstruction processing function 53.

[0039] The scan control function 55 controls the collection process of detection data in the gantry device 10 by issuing instructions to the X-ray high voltage device 14, the DAS 16, the control device 18, and the bed driving device 32. The scan control function 55 controls the operation of each part when capturing an alignment image, an actual captured image, and an image used for diagnosis.

[0040] The display control function 56 controls the display mode of the display 42. For example, the display control function 56 controls the display 42 to display a reconstructed image generated by the processing circuitry 50, a GUI image that accepts various operations by the operator, and the like.

[0041] The adjustment function 57 controls adjustment processes when the X-ray CT apparatus 1 is shipped and when parts such as the X-ray tube 11 are replaced. The adjustment processes include, for example, calibration, IF adjustment (adjusting the filament current value (IF value) of the X-ray tube 11), and seeding (applying a load to the X-ray tube at a low voltage in advance to increase the internal vacuum and remove residues, etc.). The adjustment function 57 executes the above-described adjustment processes when an execution instruction is received from the user via the input interface 43, when it detects that the target object (e.g., the X-ray tube) has been replaced, when the tube warms up, or at a predetermined interval.

[0042] The acquisition function 58 acquires data for determining design differences and the degree of deterioration of the X-ray tube 11, etc. For example, the acquisition function 58 acquires first energy spectrum information acquired by detecting X-rays at the timing (first timing) when the operating conditions of the device are adjusted at the time of shipping the X-ray CT apparatus 1, and stores the acquired first energy spectrum information as sample data 41-4 in the memory 41. The acquisition function 58 may also acquire sample data 41-4 including first energy spectrum information acquired from an external device via the network connection circuit 44 and store the sample data 41-4 in the memory 41.

[0043] Furthermore, the acquisition function 58 acquires second energy spectrum information acquired by detecting X-rays at a timing such as when the X-ray tube 11 is replaced (for example, a second timing later than the first timing). The acquisition function 58 may acquire the first energy spectrum information or the second energy spectrum information when a predetermined adjustment process (for example, IF adjustment) is executed as a trigger among the one or more adjustment processes executed by the adjustment function 57. Furthermore, the acquisition function 58 may execute the process of acquiring the first energy spectrum information or the second energy spectrum information when an execution instruction is received from the user via the input interface 43.

[0044] The determination function 59 determines the state of the object such as the X-ray tube 11 based on the first energy spectrum information and the second energy spectrum information acquired by the acquisition function 58. The determination function 59 also stores the determination result as a determination result 41-5 in the memory 41. Details of the determination function 59 will be described later.

[0045] The notification function 60 notifies the subject of notification content (such as a warning) corresponding to the state of the X-ray tube determined by the determination function 59, from among multiple notification contents included in the notification information 41-6 stored in the memory 41. For example, the notification function 60 may display the warning information on the display 42, or may notify the subject of the warning information via the network connection circuit 44 to a terminal used by the subject (for example, a portable terminal such as a smartphone or a tablet terminal, or a fixed terminal).

[0046] (About the judgment function) Next, the details of the determination function 59 will be described. The determination function 59 determines whether the object is a non-genuine product or not, and determines the degree of deterioration of the object, by determining the state of the object, such as the X-ray tube 11. In the following, the X-ray tube 11 will be used as an example of the object. In addition, in the following process, it is assumed that first energy spectrum information using a genuine X-ray tube 11 (genuine tube) has already been acquired at a first timing, such as at the time of shipment, and stored in the memory 41 as sample data 41-4.

[0047] FIG. 3 is a flowchart showing an example of a determination process for determining whether the replaced X-ray tube 11 is a non-genuine tube. In the example of FIG. 3, after the X-ray tube 11 is replaced, the adjustment function 57 executes an adjustment process for the X-ray CT device 1 after the replacement of the X-ray tube 11 (step S100). Next, the acquisition function 58 acquires second energy spectrum information (step S102) triggered by the execution of a predetermined process in the adjustment process after replacement. Next, the acquisition function 58 acquires first energy spectrum information, which is sample data 41-4 stored in the memory 41 (step S104). Next, the determination function 59 acquires count values ​​of energy bins containing specific X-rays from each of the first energy spectrum information and the second energy spectrum information (step S106).

[0048] Fig. 4 is a diagram for explaining the comparison of count values ​​of energy bins containing specific X-rays. In the example of Fig. 4, the horizontal axis represents energy (keV) and the vertical axis represents photon count values ​​(cnt). The example of Fig. 4 also shows a first energy spectrum ES1 acquired from sample data 41-4 and a second energy spectrum ES2 acquired after the exchange.

[0049] 4, energy bins (energy bands) B1 to B7 are set at predetermined intervals for each of the first energy spectrum ES1 and the second energy spectrum ES2. Note that instead of being set at predetermined intervals, the intervals of the energy bins may be different for each bin, or may be set arbitrarily depending on the interval to be determined.

[0050] For example, the determination function 59 performs the determination using the count value of an energy bin including the characteristic X-rays of the first energy spectrum ES1 obtained from the X-ray tube 11, which is a normal tube, among the energy bins shown in FIG. 4. The characteristic X-rays are, for example, a portion whose count value varies greatly depending on the material contained in the X-ray tube 11. The determination function 59 may also perform the comparison using the count value of an energy bin including the K-absorption edge energy of the anode material in the X-ray tube 11. In the example of FIG. 4, the determination function 59 obtains a count value C11 (hereinafter referred to as the first count value) of an energy bin B4 including the specific X-rays. Similarly, the determination function 59 obtains a count value C12 (hereinafter referred to as the second count value) of the energy bin B4 from the second energy spectrum ES2.

[0051] 3, the determination function 59 determines whether the difference (differential value) between the first count value C11 and the second count value C12 is equal to or greater than a threshold value (step S108). If it is determined that the difference is equal to or greater than the threshold value, the determination function 59 determines that the replaced X-ray tube is an irregular tube (step S110). Furthermore, instead of determining that the replaced X-ray tube is an irregular tube, the determination function 59 may determine that the performance of the X-ray tube corresponding to the first energy spectrum information and the X-ray tube corresponding to the second energy spectrum information is different.

[0052] Next, the notification function 60 notifies the subject of information (warning information) indicating that the replaced X-ray tube is a non-standard tube (step S112). This ends the processing of this flowchart. Also, in the processing of step S108, if the difference between the first count value and the second count value is less than the threshold value, the replaced X-ray tube is considered to be a standard tube, and the processing of this flowchart ends. Note that in this case, the notification function 60 may notify the subject of information indicating that the replaced X-ray tube is a standard tube.

[0053] As described above, the determination function 59 can more efficiently determine the state of the X-ray tube by narrowing down the determination to energy bins among all energy bins B1 to B7 that vary greatly depending on the design of the X-ray tube 11, etc. Note that in the above-described determination process, differences in target materials may be determined based on determination results using energy bins that include characteristic X-rays with different energies emitted depending on the material (substance) of the X-ray tube target. Also, in the above process, if the count value of an energy bin differs due to differences in filter material, thickness, or target angle, the determination may be performed using that energy bin. Also, the determination function 59 is not limited to a specific energy bin, and may perform determination using all energy bins, or may perform determination by comparing the first energy spectrum with the second energy spectrum.

[0054] Next, a description will be given of the process of determining the deterioration degree of the X-ray tube in the determination function 59. Fig. 5 is a flowchart showing the flow of a series of processes in the process of determining the deterioration degree. In the example of Fig. 5, it is assumed that sample data 41-4 is stored in advance in the memory 41.

[0055] 5, the determination function 59 determines whether the number of scans (number of slices) of the X-ray CT device 1 is equal to or greater than a predetermined number, or whether a predetermined time has elapsed since the previous determination process was performed (step S200). If it is determined that the number of scans is equal to or greater than the predetermined number, or a predetermined time has elapsed since the previous scan, the acquisition function 58 acquires second energy spectrum information (step S202). Next, the acquisition function 58 acquires sample data (first energy spectrum information) 41-4 from the memory 41 (step S204). Next, the determination function 59 acquires count values ​​of two different energy bins from the acquired first energy spectrum information and second energy spectrum information (step S206).

[0056] Fig. 6 is a diagram for explaining the acquisition of count values ​​of two different energy bins. In the example of Fig. 6, similarly to Fig. 4, energy bins B1 to B7 are assigned to each of the first energy spectrum ES1 and the second energy spectrum ES2. The determination function 59 acquires count values ​​of two different energy bins from each of the first energy spectrum ES1 and the second energy spectrum ES2. Of the two different energy bins, the one with lower energy is referred to as the low-energy energy bin (low-energy bin), and the one with higher energy is referred to as the high-energy energy bin (high-energy bin).

[0057] 6, the determination function 59 obtains a count value C12 of the energy bin B2 and a count value C13 of the energy bin B6 of the first energy spectrum ES1. Similarly, the determination function 59 obtains a count value C22 of the energy bin B2 and a count value C23 of the energy bin B6 of the second energy spectrum ES2.

[0058] Returning to FIG. 5 , the determination function 59 then calculates the ratio of the count value of the low-energy bin to the count value of the high-energy bin in the first energy spectrum ES1 (e.g., output ratio C12 / C13) and the ratio of the count value of the low-energy bin to the count value of the high-energy bin in the second energy spectrum ES2 (e.g., output ratio C22 / C23) (step S208). Next, the determination function 59 determines whether the difference between the count ratios is equal to or greater than a threshold (step S210). If it is determined that the difference is equal to or greater than the threshold, the determination function 59 determines the degree of deterioration according to the difference (step S212). In the process of step S212, the determination function 59 determines, for example, that the greater the difference, the greater the degree of deterioration. Furthermore, when determining the degree of deterioration of the anode material, the determination function 59 may determine the degree of deterioration of the anode material by referring to a correspondence table between the output ratios of the low-energy bin to the high-energy bin and the anode thickness, which is stored in advance in the memory 41. The correspondence table is generated in advance, for example, through simulation or actual measurement before shipping the X-ray CT apparatus 1. The correspondence table may also be stored in the sample data 41-4. If a similar correspondence table has been generated in advance for materials other than the anode material, the determination function 59 may similarly determine the degree of deterioration for the other materials (materials).

[0059] Next, the notification function 60 notifies the subject of information based on the determination result (for example, information indicating the degree of deterioration or information indicating that maintenance is required) (step S214). This ends the processing of this flowchart. Also, if it is determined in the processing of step S200 that the number of scans is not equal to or greater than the predetermined number and that a predetermined time has not elapsed since the previous scan, or if it is determined in the processing of step S210 that the difference in count ratio is not equal to or greater than the threshold, the processing of this flowchart ends.

[0060] In the process of step S200, the processes from step S202 onwards may be performed at a timing of the user's choice (for example, at a timing instructed by a serviceman from the console). In the above-mentioned determination process, the degree of deterioration can be determined more efficiently, and the subject can be notified of the condition more accurately.

[0061] <Modification> The above embodiment may be implemented by using a PCD as a Ref (Reference) detector of the CT device instead of using the main detector of the PCCT device. Also, the sample data in the embodiment may be installed or updated after shipment by downloading via a network or by using a recording medium such as a magnetic memory. In addition, in the embodiment, the determination function 59 may perform determination by changing (narrowing) the energy width of the bin so as to focus on an area including characteristic X-rays or an area including scattered X-rays depending on the content of the determination.

[0062] According to at least one of the embodiments described above, the X-ray CT device of the embodiment includes a photon-counting X-ray detector that detects X-rays irradiated from the X-ray tube in photon units, a memory unit that stores first energy spectrum information acquired by detecting X-rays at a first timing, an acquisition unit that acquires second energy spectrum information by detecting X-rays at a second timing that is later than the first timing, and a determination unit that determines the state of the X-ray tube based on the first energy spectrum information and the second energy spectrum information, thereby making it possible to more efficiently determine the state of the X-ray tube.

[0063] Specifically, according to this embodiment, for example, air irradiation spectra can be easily inspected, and X-ray tubes whose air irradiation spectra differ from the recommended values ​​can be detected. Furthermore, according to this embodiment, by comparing the counts for each energy bin of the sample energy spectrum data with the energy spectrum of the installed X-ray tube, X-ray tubes that provide inappropriate air irradiation spectra that cause artifacts such as CT value shifts can be detected and notified to the subject. Furthermore, because the air irradiation spectra are compared using a PCD installed in the PCCT device, there is no need to introduce an external device, as typified by conventional verification methods in which an electronic board with an individual ID number is embedded in the X-ray tube for verification. This avoids changes to the device's external dimensions, increases in weight, and increases in manufacturing costs.

[0064] The above-described embodiment can be expressed as follows. A memory for storing programs; a processor, the memory stores first energy spectrum information acquired by detecting X-rays at a first timing; The processor executes the program, The photon-counting X-ray detector detects the X-rays emitted from the X-ray tube in photon units. detecting X-rays at a second timing that is later than the first timing to obtain second energy spectrum information; determining a state of the X-ray tube based on the first energy spectrum information and the second energy spectrum information; X-ray CT device.

[0065] Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various reductions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as the inventions described in the claims and their equivalents. [Explanation of symbols]

[0066] 1...X-ray CT device, 10...mounting device, 11...X-ray tube, 12...wedge, 13...collimator, 14...X-ray high voltage device, 15...X-ray detector, 16...data acquisition system, 17...rotating frame, 18...control device, 30...bed device, 40...console device, 50...processing circuit, 51...system control function, 52...preprocessing function, 53...reconstruction processing function, 54...image processing function, 55...scan control function, 56...display control function, 57...adjustment function, 58...acquisition function, 59...determination function, 60...notification function

Claims

1. a photon-counting X-ray detector that detects X-rays emitted from an X-ray tube in photon units; a storage unit that stores first energy spectrum information acquired by detecting X-rays at a first timing; an acquisition unit that acquires second energy spectrum information by detecting X-rays at a second timing that is later than the first timing; a determination unit that determines a state of the X-ray tube based on the first energy spectrum information and the second energy spectrum information, the first timing is a timing when a regular X-ray tube is installed, and the second timing is a timing when the X-ray tube is replaced, the determination unit determines whether the replaced X-ray tube is an unauthorized X-ray tube. X-ray CT device.

2. the determination unit determines the state of the X-ray tube based on a difference between a photon count value in a predetermined energy bin included in the first energy spectrum information and a photon count value in the predetermined energy bin included in the second energy spectrum information. The X-ray CT apparatus according to claim 1 .

3. the determination unit determines a degree of deterioration of the X-ray tube based on a comparison result between a photon count value of each of two different energy bins among a plurality of energy bins included in the first energy spectrum information and a photon count value of each of the two different energy bins among a plurality of energy bins included in the second energy spectrum information.

3. The X-ray CT apparatus according to claim 1.

4. a notification unit that issues a predetermined notification to a subject based on the state of the X-ray tube determined by the determination unit, The X-ray CT apparatus according to any one of claims 1 to 3.

5. A photon counting X-ray detector that detects X-rays irradiated from an X-ray tube in photon units; a storage unit that stores first energy spectrum information acquired by detecting X-rays at a first timing; an acquisition unit that acquires second energy spectrum information by detecting X-rays at a second timing that is later than the first timing; a determination unit that determines a state of the X-ray tube based on a photon count value of a predetermined energy bin among a plurality of energy bins included in the first energy spectrum information and a photon count value of the predetermined energy bin among a plurality of energy bins included in the second energy spectrum information, the predetermined energy bin is an energy bin in which the count value changes significantly in accordance with a change in the anode of the X-ray tube; X-ray CT device.

6. The predetermined energy bin is an energy bin that includes characteristic X-rays corresponding to the X-ray tube installed at the first timing, the determination unit determines the state of the X-ray tube at the second timing based on a difference between a photon count value of the predetermined energy bin among a plurality of energy bins included in the first energy spectrum information and a photon count value of the predetermined energy bin among a plurality of energy bins included in the second energy spectrum information.

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

7. The predetermined energy bins are two different energy bins, the determination unit determines the state of the X-ray tube at the second timing based on a ratio of photon count values ​​of the two different energy bins among a plurality of energy bins included in the first energy spectrum information and a ratio of photon count values ​​of the two different energy bins among a plurality of energy bins included in the second energy spectrum information.

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

8. The computer A photon-counting X-ray detector detects the X-rays emitted from the X-ray tube in photon units; storing first energy spectrum information acquired by detecting X-rays at a first timing in a storage unit; detecting X-rays at a second timing that is later than the first timing to obtain second energy spectrum information; determining a state of the X-ray tube based on the first energy spectrum information and the second energy spectrum information; the first timing is a timing when a regular X-ray tube is installed, and the second timing is a timing when the X-ray tube is replaced, determining whether the replaced X-ray tube is an unauthorized X-ray tube based on the first energy spectrum information and the second energy spectrum information; Judgment method.

9. On the computer, The photon-counting X-ray detector detects the X-rays emitted from the X-ray tube in photon units; storing first energy spectrum information acquired by detecting X-rays at a first timing in a storage unit; detecting X-rays at a second timing that is later than the first timing to obtain second energy spectrum information; determining a state of the X-ray tube based on the first energy spectrum information and the second energy spectrum information; the first timing is a timing when a regular X-ray tube is installed, and the second timing is a timing when the X-ray tube is replaced, determining whether the replaced X-ray tube is an unauthorized X-ray tube based on the first energy spectrum information and the second energy spectrum information; program.

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