X-ray CT apparatus, program product, and information processing method

Abstract

The invention relates to an X-ray CT apparatus, a program product, and an information processing method. The X-ray CT device comprises an X-ray generating device and an X-ray inspector for detecting X-rays emitted by the X-ray generating device and passing through an object to be detected, and is an X-ray CT device for collecting X-ray projection data of at least two kinds of X-ray energy and reconstructing the X-ray projection data into a dual-energy image. The X-ray detector is provided with: an acquisition unit that acquires object information including physical quantity and physical characteristic information of the object, and X-ray characteristic information of the X-ray spectrum, the X-ray filter, and the X-ray detector; and an X-ray imaging condition determination unit that determines the respective X-ray imaging conditions when collecting the X-ray projection data of at least two kinds of X-ray energy irradiated by the X-ray generation device, on the basis of the object information acquired by the acquisition unit, the X-ray spectrum, and the X-ray characteristic information of the X-ray filter and the X-ray detector.

Description

Technical Field

[0001] The present technology relates to an X-ray CT device, a program and an information processing method. Background Art

[0002] Currently, the more common X-ray CT devices have the following structures: dual energy imaging that can realize switching the X-ray tube voltage between low voltage (such as 80kV) and high voltage (such as 140kV) using one X-ray tube during scanning and taking pictures, dual energy imaging that uses two X-ray tubes to simultaneously take pictures of low voltage (such as 80kV) and high voltage (such as 140kV) of the X-ray tube voltage, dual energy imaging that uses a two-layer X-ray detector to collect low energy X-ray components and high energy X-ray components, and dual energy imaging that uses a semiconductor X-ray detector to distinguish between low energy X-ray components and high energy X-ray components and collect them.

[0003] [Prior art literature]

[0004] [Patent Document]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2012-100913 Summary of the invention

[0006] [Problems to be Solved by the Invention]

[0007] However, the X-ray CT apparatus disclosed in Patent Document 1 does not consider the point that more appropriate X-ray radiographic conditions for dual energy imaging are determined according to different types of scanned objects (detected objects). In a more appropriate case, the following points may be included: considering the linear quality of X-rays output from the X-ray tube and passing through the X-ray filter and the energy detection distribution of the X-ray detector, the X-ray absorption coefficient ratio (dual energy ratio) of the detected object at low and high voltages of the X-ray tube voltage is further expanded, and the SN ratio at low and high voltages of the X-ray tube voltage is made as equal as possible. However, when there is a bow-tie filter that controls the distribution of irradiated X-rays in the imaging field channel direction, the bow-tie filter may also be included in the X-ray filter.

[0008] From one aspect, an object of the present invention is to provide an X-ray CT apparatus or the like which can determine more appropriate X-ray radiography conditions for dual energy imaging according to an object to be scanned.

[0009] [Solution to solve the problem]

[0010] An X-ray CT device in one embodiment of the present disclosure includes an X-ray generating device and an X-ray detector for detecting X-rays emitted from the X-ray generating device and penetrating an object to be detected. The X-ray CT device reconstructs a dual-energy image after collecting X-ray projection data of at least two X-ray energies, and has: an acquisition unit for acquiring information about the object to be detected including physical quantities and physical property information of the object to be detected, and X-ray property information of an X-ray spectrum, an X-ray filter, and an X-ray detector; and an X-ray imaging condition determination unit for determining respective X-ray imaging conditions when collecting X-ray projection data of at least two X-ray energies emitted by the X-ray generating device, based on the information about the object to be detected and the X-ray property information of the X-ray spectrum, the X-ray filter, and the X-ray detector acquired by the acquisition unit.

[0011] The X-ray CT device includes an X-ray filter, and reconstructs multiple density tomograms such as monochrome tomograms of each keV (effective energy), water density tomograms, and iodine density tomograms by reconstructing dual energy images.

[0012] A program in one embodiment of the present disclosure is to perform the following processing on a computer: obtaining information on the object to be detected, including physical quantities and physical property information of the object to be detected as a detection object, as well as X-ray characteristic information of the X-ray spectrum, X-ray filter and X-ray detector, obtained by X-rays of at least two types of X-ray energies irradiated by an X-ray generating device; and determining various X-ray photography conditions when collecting X-ray projection data of at least two types of X-ray energies irradiated by the X-ray generating device based on the acquired information on the object to be detected and the X-ray characteristic information of the X-ray spectrum, X-ray filter and X-ray detector.

[0013] An information processing method in one embodiment of the present disclosure is to perform the following processing on a computer: obtaining information on the object to be detected, including physical quantities and physical property information of the object to be detected as a detection object, as well as X-ray characteristic information of the X-ray spectrum, X-ray filter and X-ray detector, obtained by X-rays of at least two types of X-ray energies irradiated by an X-ray generating device; and determining various X-ray photography conditions when collecting X-ray projection data of at least two types of X-ray energies irradiated by the X-ray generating device based on the obtained information on the object to be detected and the X-ray characteristic information of the X-ray spectrum, X-ray filter and X-ray detector.

[0014] [Effects of the invention]

[0015] According to the present disclosure, an X-ray CT apparatus or the like can be provided which determines more appropriate X-ray imaging conditions during dual energy imaging according to the object to be scanned. In a more appropriate case, the following points can be included: considering the line quality of the X-ray output from the X-ray tube and passing through the X-ray filter and the energy detection distribution of the X-ray detector, the X-ray absorption coefficient ratio (dual energy ratio) of the object to be detected at the low voltage and high voltage of the X-ray tube voltage is further expanded, and the SN ratio at the low voltage and high voltage of the X-ray tube voltage is made as equal as possible. However, when there is a bow-tie filter that controls the distribution of the irradiated X-rays in the imaging field channel direction, the bow-tie filter can also be included in the X-ray filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram showing an overview of the X-ray CT apparatus according to the first embodiment.

[0017] Figure 2 It is an explanatory diagram of the rotation of the X-ray generator and the 2D X-ray detector.

[0018] Figure 3 This is a functional block diagram showing an example of the functional units included in the X-ray CT apparatus (central processing unit).

[0019] Figure 4 This is a flowchart of the schematic operation of the X-ray CT apparatus.

[0020] Figure 5 This is a flowchart showing the details of data collection in the general operation of the X-ray CT apparatus.

[0021] Figure 6 This is a flowchart of details of determination (simulation) of X-ray imaging conditions in data collection of an X-ray CT apparatus.

[0022] Figure 7 This is a flowchart showing the details of pre-processing in the general operation of the X-ray CT apparatus.

[0023] Figure 8 This is a flowchart of the 3D back projection process in the general operation of the X-ray CT apparatus.

[0024] Fig. 9 This is a diagram for explaining the flow of data processed in image reconstruction using dual energy imaging.

[0025] Fig.10 This is a functional block diagram showing, by way of example, the functional units included in the X-ray CT apparatus (central processing unit) according to the second embodiment.

[0026] Fig.11 This is an explanatory diagram showing an example of an X-ray imaging condition table (comparison table).

[0027] Fig.12 This is a flowchart showing the details of data collection (check list) in the general operation of the X-ray CT system. DETAILED DESCRIPTION

[0028] (Implementation method 1)

[0029] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings showing embodiments thereof. Figure 1 This is a schematic diagram of the outline of the X-ray CT apparatus 1 involved in the first embodiment. The X-ray CT apparatus 1 includes an operation console 2, an imaging table 4 arranged in an X-ray inspection room R, an X-ray generating device 5, an operation controller 6, a 2D X-ray detector 7, a lifting mechanism 8, and a data acquisition system 9 (DAS: Data Acquisition System). In addition, an imaging unit 10 is provided in the X-ray inspection room R. The imaging unit 10 may be connected to the operation console 2 in a communicable manner and serve as a part of the X-ray CT apparatus 1.

[0030] The operation console 2 includes an input device 21 , a data collection buffer memory 22 , a monitor 23 , a storage device 24 , and the central processing unit 3 .

[0031] The input device 21 may be, for example, an input device of a user operating system such as a keyboard or a mouse, or an input / output I / F of a communication system for inputting data sent from other computers.

[0032] The data collection buffer memory 22 is connected to the central processing device 3 and the data collection device 9 arranged in the X-ray inspection room R in a communicable manner, and outputs the X-ray detector data obtained from the data collection device 9 to the central processing device 3 .

[0033] The monitor 23 is a display device such as a display. The X-ray detector data is processed by the central processing unit 3 , and an image (dual energy image, X-ray dual energy tomogram) reconstructed from the X-ray detector data is displayed on the monitor 23 .

[0034] The central processing unit 3 functions as an image reconstruction unit and reconstructs an X-ray dual energy tomogram based on X-ray projection data detected by the 2D X-ray detector 7 (X-ray detector) by executing a program stored in the storage device 24 .

[0035] The storage device 24 includes volatile storage areas such as SRAM (Static Random Access Memory), DRAM (Dynamic Random Access Memory), and flash memory, and non-volatile storage areas such as EEPROM or hard disk. The storage device 24 pre-stores the program to be executed by the central processing unit 3 and the data referenced during processing. The program stored in the storage device 24 may be a program that is read and stored from a storage medium that can be read from the operation console 2. In addition, it may be a program downloaded from an external computer (not shown) connected to a communication network (not shown) and stored in the storage device 24.

[0036] The central processing unit 3 has one or more CPUs (Central Processing Units), MPUs (Micro-Processing Units), GPUs (Graphics Processing Units) and other computing processing devices with timing functions, and performs various information processing and control processing related to the X-ray CT device 1, including tomographic image reconstruction related processing, by reading and executing programs stored in the storage device 24.

[0037] The X-ray generating device 5 includes an X-ray tube controller 54, an X-ray tube 51, an X-ray filter 53, a bow-tie filter 531 and a collimator 52. Its structure is to perform high-energy and low-energy dual-energy imaging by using at least two types of X-ray energies.

[0038] The X-ray tube controller 54 is connected to the control controller 6 in a communicable manner, and changes the tube voltage of the X-ray tube 51 according to the control signal and high voltage output by the control controller 6, thereby controlling the start and stop of X-ray irradiation by the X-ray tube 51. The X-ray tube controller 54 is composed of, for example, a microcomputer in which a control unit such as a CPU and a storage unit are packaged together.

[0039] The X-ray tube 51 can emit high energy X-rays and low energy X-rays, for example. The tube voltage of the X-ray tube 51 corresponding to the high energy and low energy X-ray tubes 51 is determined according to the control signal and high voltage sent by the X-ray tube controller 54.

[0040] The X-ray filters 53 are respectively arranged on the high-energy and low-energy X-ray tubes 51, including the X-ray filters 53 through which the high-energy X-rays pass and the X-ray filters 53 through which the low-energy X-rays pass. The X-ray filter 53 is provided with a filter characteristic variable structure that makes the filter characteristic variable, and the filter characteristic can be changed according to the control signal sent by the operation controller 6 or the X-ray tube controller 54. The filter characteristic (X-ray filter characteristic) is, for example, a characteristic determined by the material of the filter and the thickness of the filter (the passing distance of the X-ray). According to the control signal sent by the operation controller 6, etc., the X-ray filter 53 can replace filters of different materials through the filter characteristic variable structure set in the X-ray filter 53, for example, replacing a lead filter with an iron filter, or replacing filters of different thicknesses in filters of the same material. The bow-tie filter 531 changes the X-ray absorption coefficient in the channel direction of the imaging field of view and controls the distribution of the irradiated X-rays in the channel direction.

[0041] The linear quality of X-rays varies according to the tube voltage value of the X-ray tube 51 or the filter characteristics of the X-ray filter 53. The X-ray generating device 5 adopts a structure that makes the tube voltage value and the X-ray filter characteristics variable, thereby irradiating the object H to be detected with high-energy and low-energy X-rays of appropriate linear quality, thereby realizing dual-energy imaging with high efficiency.

[0042] The collimator 52 , for example, includes a slice thickness direction collimator and a channel direction collimator, and collimates and shapes the X-rays generated by the X-ray tube 51 .

[0043] The object H to be detected is placed on the photographic table 4 and rotated a predetermined number of times according to the control signal output by the operation controller 6. The photographic table 4 irradiates the entire circumference of the object H to be detected placed on the photographic table 4 with X-rays by rotating. In the present embodiment, it is not limited to the case where the photographic table 4 rotates, and the photographic table 4 may be fixed, and the X-ray generator 5, the 2D X-ray detector 7, and the data collection device 9 may rotate relative to the photographic table 4. In other words, the photographic table 4 may be relatively rotated with the X-ray generator 5, the 2D X-ray detector 7, and the data collection device 9, so that the entire circumference of the object H to be detected in the rotation direction is irradiated with X-rays.

[0044] The lifting mechanism 8 lifts and lowers the imaging table 4 or the X-ray generator 5, the 2D X-ray detector 7, and the data collection device 9, and adopts a structure in which the imaging table 4, the X-ray generator 5, the 2D X-ray detector 7, and the data collection device 9 move relative to each other in the vertical direction. The lifting mechanism 8 moves the imaging table 4, the X-ray generator 5, etc. relative to each other in the vertical direction according to the control signal output by the operation controller 6. In this way, the X-ray can be irradiated to the entire area of ​​the object H in the vertical direction (height direction).

[0045] The operation controller 6 is connected to the central processing unit 3 of the operation console 2 in a communicable manner, and controls or drives the X-ray generator 5, the imaging table 4, the lifting mechanism 8, the 2D X-ray detector 7 and the data collection device 9 according to the instruction information output by the central processing unit 3. The operation controller 6 can be composed of a microcomputer in which a control unit such as a CPU and a storage unit are packaged together.

[0046] The 2D X-ray detector 7, for example, has a plurality of detector columns (X-ray detector channels). In the 2D X-ray detector 7, a plurality of channels for detecting X-rays penetrating the object H to be detected and collecting X-ray detector data are arranged along the channel direction relative to the rotation direction of the object H to be detected and along the vertical column direction along the rotation axis during rotation.

[0047] The data collection device 9 collects X-ray detector data from the 2D X-ray detector 7 , and outputs the X-ray detector data to the central processing device 3 via the data collection buffer memory 22 .

[0048] The imaging unit 10, such as a camera, is arranged at a position above the photographing table 4 in the X-ray inspection room R, etc., to ensure that the entire object H placed on the photographing table 4 is within the photographing range. The imaging unit 10 outputs the image data of the object H photographed to the operation console 2 (central processing unit 3). The imaging unit 10 is equivalent to an object information acquisition device, which is used to obtain physical quantities such as the shape and size of the object H or physical property information such as the material of the object H. The object information acquisition device is not limited to the imaging unit 10 such as a camera, but can also be a 3D scanning device or a three-dimensional dimension measuring device. These devices included in the X-ray CT device 1, for example, can also be devices with the same structure, the same role and function as the various devices of the X-ray CT device described in Japanese Patent No. 5220374, Japanese Patent No. 5213016, and Japanese Patent Publication No. 2007-20906.

[0049] Figure 2 This is an explanatory diagram of the rotation of the X-ray generator 5 and the 2D X-ray detector 7. The X-ray tube 51 and the 2D X-ray detector 7 rotate relative to the imaging table around the rotation center, which is the center of the imaging table. When the vertical direction is the Y direction, the horizontal direction is the X direction, and the imaging table travel direction perpendicular to these directions is the Z direction, the rotation plane of the X-ray tube 51 and the 2D X-ray detector 7 is the XY plane.

[0050] The X-ray tube 51 generates an X-ray beam called a cone beam. The viewing angle 0° is defined as when the central axis of the cone beam is parallel to the Y direction. The 2D X-ray detector 7 has, for example, a detector array of 300 channels x 3000 columns. In the 2D X-ray detector 7, a plurality of channels for detecting X-rays penetrating the object H to be detected and collecting X-ray detector data are arranged in a channel direction relative to the rotation direction of the object H to be detected by the imaging table 4 and the like and in a vertical column direction along the rotation axis during rotation.

[0051] The X-ray detector data collected after X-ray irradiation is transmitted from the 2D X-ray detector 7 to the data collection device 9, where A / D conversion is performed and output to the data collection buffer memory 22. The data input to the data collection buffer memory 22 is processed and reconstructed into an image tomogram in the central processing unit 3 and displayed on the monitor 23.

[0052] Figure 3 This is a functional block diagram showing an example of the functional units included in the X-ray CT apparatus 1 (central processing unit 3). The central processing unit 3 in the X-ray CT apparatus 1 functions as an acquisition unit 31, an X-ray imaging condition determination unit 32, and an output unit 33 by executing a program stored in the storage device 24. The program includes simulation-related program modules or subroutines executed by the simulation execution unit 321 described later.

[0053] The acquisition unit 31 acquires the image data of the object H to be detected output from the imaging unit 10. Alternatively, the acquisition unit 31 may also acquire the physical quantities such as the shape and size and the physical property information such as the material of the object H to be detected input by the operator of the operation console 2 via the input device 21. These physical quantities and physical property information of the object H to be detected may be in the form of drawing information (3D CAD data) of the object H to be detected, for example, and the acquisition unit 31 may also acquire the drawing information of the object H to be detected via the input device 21 having a communication system I / F function or a communication device for communicating with other computers. Alternatively, the acquisition unit 31 may also acquire, for example, a positioning scan image photographed for use as a positioning image from the data collection buffer memory 22.

[0054] The acquisition unit 31 derives the physical quantities such as the shape and size and the physical property information such as the material of the object H to be detected based on the image data, drawing information or positioning scan image of the object H to be detected acquired in the above manner, and outputs the derived physical quantities and physical property information to the X-ray imaging condition determination unit 32. The acquisition unit 31 can also derive the physical quantities and physical property information based on the image data, for example, by pattern matching the image of the object H to be detected and extracted through edge detection. Alternatively, the acquisition unit 31 can also use an object detection algorithm having a segmented network function for performing object detection, such as a learning model composed of RCNN or SSD (Single Shot Multibox Detector), YOLO (You Only Look Once), etc., to detect the object H to be detected based on the image data and derive the physical quantities and physical property information of the object H to be detected. Alternatively, the physical quantities and physical property information of the object H to be detected can also be derived using a 3D scanning device or a three-dimensional dimension measuring device.

[0055] Furthermore, the acquisition unit 31 acquires, for example, the X-ray spectrum, the X-ray filter 53, and the X-ray characteristic information of the 2D X-ray detector 7 (X-ray detector) from the data collection buffer memory 22. The acquisition unit 31 outputs the acquired X-ray characteristic information and the object information (physical quantity and physical characteristic information of the object) to the X-ray imaging condition determination unit 32.

[0056] The X-ray imaging condition determination unit 32 includes a simulation execution unit 321, a filter characteristic determination unit 322, and an X-ray tube voltage determination unit 323, and performs simulation using the X-ray characteristic information output by the acquisition unit 31 and the physical quantity and physical characteristic information of the object H as input factors, and determines a preferred or most preferred X-ray imaging condition when detecting the object H. More preferably, the X-ray imaging condition includes the following points: considering the radiation quality of the X-ray output from the X-ray tube and passing through the X-ray filter 53 and the energy detection distribution of the 2D X-ray detector 7 (X-ray detector), further expanding the X-ray absorption coefficient ratio (dual energy ratio) of the object H at the low voltage and high voltage of the X-ray tube voltage, and making the SN ratio at the low voltage and high voltage of the X-ray tube voltage as equal as possible. With this X-ray imaging condition, the preferred or most preferred X-ray radiation quality can be achieved. The simulation execution unit 321 determines whether the low X-ray tube voltage and the high X-ray tube voltage derived by the simulation satisfy a predetermined condition related to SNR (noise ratio), for example, that the SN ratios at the low voltage and the high voltage of the X-ray tube voltage are as equal as possible, and determines the preferred X-ray imaging condition when detecting the object H according to the determination result. The predetermined condition is, for example, a condition that the SNR (noise ratio) of the low X-ray tube voltage and the high X-ray tube voltage derived by the simulation is less than a predetermined value. Alternatively, the simulation execution unit 321 may derive a DE (Dual Energy) ratio of a high X-ray tube voltage value (high energy X-ray tube voltage value) and a low X-ray tube voltage value (low energy X-ray tube voltage value) based on the physical quantity and physical property information of the object H as input factors, and perform an optimization simulation to increase the DE ratio. The filter characteristic determination unit 322 determines the filter characteristics of the high energy and low energy X-ray filters 53 according to the simulation result of the simulation execution unit 321. The X-ray tube voltage determination unit 323 determines the X-ray tube voltage values ​​of the high energy and low energy X-ray tubes 51, respectively, based on the simulation result of the simulation execution unit 321. The X-ray imaging condition determination unit 32 may be a device that determines the X-ray imaging conditions of the two X-ray energies by determining the X-ray tube voltage values, X-ray tube current values, imaging time, and X-ray filter 53 of the X-rays of the two X-ray energies, respectively, based on the object information acquired by the acquisition unit 31, the X-ray spectrum, and the X-ray characteristic information of the X-ray filter 53 and the 2D X-ray detector 7 (X-ray detector).

[0057] The radiation quality of X-rays varies according to the tube voltage value of the X-ray tube 51 or the filter characteristics of the X-ray filter 53. Therefore, by determining the tube voltage value of the X-ray tube 51 and the filter characteristics of the X-ray filter 53 based on the simulation results, it is possible to determine the X-ray imaging conditions that achieve the corresponding X-ray radiation quality. The X-ray imaging condition determination unit 32 outputs information on the X-ray imaging conditions including the determined filter characteristics and X-ray tube voltage value to the output unit 33.

[0058] The output unit 33 generates information related to control parameters for controlling the X-ray generator 5 based on the information related to the X-ray imaging conditions obtained from the X-ray imaging condition determination unit 32, and outputs the information related to the control parameters to the operation controller 6. The information related to the X-ray imaging conditions includes information related to the filter characteristics and the X-ray tube voltage value. The output unit 33 generates information related to the control parameters based on the filter characteristics and the X-ray tube voltage value, and outputs the information to the operation controller 6.

[0059] The control controller 6 performs relevant control according to the control parameters output by the output unit 33, including setting the tube voltage value of the X-ray tube 51 and setting the filter characteristics by changing or adjusting the X-ray filter 53. Alternatively, the following device may be used: the information related to the X-ray imaging conditions including the filter characteristics and the X-ray tube voltage value is output to the control controller 6, and the control controller 6 outputs the control parameters generated according to the filter characteristics and the X-ray tube voltage value to the X-ray tube controller 54 and the X-ray filter 53, thereby controlling the X-ray tube 51 and the X-ray filter 53.

[0060] Although the central processing unit 3 of the operation console 2 is used above, it is not limited to this, and other controllers such as the operation controller 6 can also be used for processing. Alternatively, it is also possible that these central processing units 3, the operation controller 6, and the X-ray tube controller 54, which have information calculation and processing functions, cooperate to operate as a series of functional units. Alternatively, it is also possible that these functional units are undertaken by an external server connected to the central processing unit 3 of the operation console 2 in a communicable manner via an external network such as the Internet, and the central processing unit 3 of the operation console 2 obtains the processing results of the external server and functions as a series of functional units based on the obtained processing results.

[0061] Figure 4 This is a flowchart schematically showing the operation of the X-ray CT apparatus 1 . Figure 5 This is a flowchart showing details of data collection (simulation) in the general operation of the X-ray CT apparatus 1 . Figure 6 This is a flowchart of details of determination (simulation) of X-ray imaging conditions in data collection by the X-ray CT apparatus 1 . Figure 7 This is a flowchart showing the details of pre-processing in the general operation of the X-ray CT apparatus 1 . Figure 8 This is a flowchart of the 3D back projection process in the general operation of the X-ray CT apparatus 1. The X-ray CT apparatus 1 starts the process or operation corresponding to the flowchart based on instruction data including an operation instruction input from the operation console 2, for example.

[0062] The X-ray CT apparatus 1 performs data collection (S11). The processing involved in the data collection is, for example, a subroutine-based processing. Figure 5 The following process shown is executed.

[0063] The X-ray CT apparatus 1 acquires the object information, the X-ray spectrum, the X-ray filter 53, and the X-ray characteristic information of the 2D X-ray detector 7 (X-ray detector) (S111). The X-ray CT apparatus 1 acquires the object information of the corresponding object H, including the image data of the object H output by the imaging unit 10, the information of the object H input from the input device 21, or the positioning scan image of the object H. In addition, the X-ray CT apparatus 1 acquires the X-ray spectrum, the X-ray filter 53, and the X-ray characteristic information of the 2D X-ray detector 7 (X-ray detector).

[0064] The X-ray CT apparatus 1 performs simulation based on the acquired object information and X-ray characteristic information to determine the X-ray imaging conditions (S112). The processing involved in determining the X-ray imaging conditions is, for example, a subprogrammed processing. Figure 6 The following process shown is executed.

[0065] The X-ray CT device 1 derives the X-ray spectra of various low X-ray tube voltages and high X-ray tube voltages (S1121). The X-ray CT device 1, for example, derives the X-ray spectra of various low X-ray tube voltages and high X-ray tube voltages by measuring using an X-ray flat panel detector having a scintillator and a photodiode. Alternatively, the X-ray CT device 1 may also be a device that obtains the X-ray spectra of various low X-ray tube voltages and high X-ray tube voltages by simulation.

[0066] The X-ray CT device 1 derives the X-ray spectrum emitted by the X-ray tube based on the material and thickness of the X-ray tube opening (S1122). The X-ray CT device 1 derives the X-ray spectrum after the X-ray filter 53 (after passing through the X-ray filter 53) based on the various materials and thicknesses of the X-ray filter 53 (S1123). The X-ray CT device 1, for example, obtains the material and thickness of the X-ray tube opening and the various materials and thicknesses of the X-ray filter 53 stored in the storage device 24 by referring to the storage device 24. The X-ray CT device 1 derives the X-ray spectrum based on the acquired information.

[0067] The X-ray CT apparatus 1 derives the X-ray spectrum after passing through the object to be detected (the object to be detected) (S1124). The X-ray CT apparatus 1 obtains the X-ray spectrum that can be captured by the scintillator and predicts the amount of X-rays that can be obtained (S1125). The X-ray CT apparatus 1, for example, obtains the X-ray spectrum that can be captured by the scintillator included in the X-ray flat panel detector and predicts the amount of X-rays that can be obtained.

[0068] The X-ray CT apparatus 1 determines whether the simulation of both the low X-ray tube voltage and the high X-ray tube voltage has been completed, and whether the imaging conditions that can achieve a sufficient SNR (noise ratio) have been obtained (S1126). The X-ray CT apparatus 1 determines whether the low X-ray tube voltage and the high X-ray tube voltage derived by the simulation meet, for example, a prescribed condition related to the SNR (noise ratio). The prescribed condition refers to, for example, a condition that the SNR (noise ratio) of the low X-ray tube voltage and the high X-ray tube voltage derived by the simulation is below a prescribed value. When the imaging conditions that can achieve a sufficient SNR (noise ratio) have not been obtained (S1126: No), the X-ray CT apparatus 1 performs a loop process and executes S1121 again. When the loop process is performed when the imaging conditions that can achieve a sufficient SNR (noise ratio) have not been obtained by simulation, the X-ray CT apparatus 1 (central processing unit 3) may also perform an iterative process, that is, the set value (input factor) when executing the simulation is changed according to a prescribed unit and repeatedly executed. Alternatively, the X-ray CT apparatus 1 may derive a DE (Dual Energy) ratio of a high X-ray tube voltage value (a high energy X-ray tube voltage value) and a low X-ray tube voltage value (a low energy X-ray tube voltage value) when performing a simulation of a low X-ray tube voltage and a high X-ray tube voltage, and perform an optimization simulation to increase the DE ratio.

[0069] When the imaging conditions that can achieve sufficient SNR (noise ratio) are obtained (S1126: Yes), the X-ray CT device 1 determines the imaging conditions consisting of the most preferred low X-ray tube voltage and high X-ray tube voltage, and X-ray filter conditions (S1127). After executing the processing of S112, the X-ray CT device 1 executes the processing of S113. The X-ray CT device 1 is not limited to: executing the processing after S113 after executing the processing of S112. After executing the processing of S112, the X-ray CT device 1 performs data collection and imaging at 80kV and 140kV to reconstruct the dual-energy image. In addition, the X-ray CT device 1 can also display the reconstructed dual-energy image, and display a monochromatic tomogram (monochromatic image), a water density tomogram, an iodine density tomogram, etc.

[0070] The X-ray CT apparatus 1 derives control parameters according to the determined X-ray imaging conditions (S113). The X-ray CT apparatus 1 determines the filter characteristics of the high-energy and low-energy X-ray filters 53 and the X-ray tube voltage values ​​of the high-energy and low-energy X-ray tubes 51 of the simulated X-ray imaging conditions, and derives control parameters for controlling the X-ray generator 5 according to the determined filter characteristics and X-ray tube voltage values. This series of processing from S111 to S113 may also be operations performed by the central processing unit 3 of the operation console 2 included in the X-ray CT apparatus 1, for example. Alternatively, the central processing unit 3 and the operation controller 6 may cooperate to perform a series of operations.

[0071] The X-ray CT apparatus 1 irradiates X-rays using the X-ray tube voltage value and the X-ray filter 53 selected according to the control parameters (S114). The X-ray CT apparatus 1 selects or sets the X-ray tube voltage value and the X-ray filter 53 according to the derived control parameters, and irradiates X-rays under the set conditions. The X-ray CT apparatus 1 collects data detected by the 2D X-ray detector 7 (X-ray detector data) (S115).

[0072] The X-ray CT apparatus 1 performs preprocessing (S12). The preprocessing is performed as a subroutine, for example. Figure 7 The following process is performed as shown. The X-ray CT device 1 performs offset correction (S121). The X-ray CT device 1 performs logarithmic conversion (S122). The X-ray CT device 1 performs X-ray dose correction (S123). The X-ray CT device 1 performs sensitivity correction (S124). The pre-processing includes the above-mentioned offset correction, logarithmic conversion, X-ray dose correction and sensitivity correction. The X-ray CT device 1 pre-processes the X-ray detector data and converts it into projection data.

[0073] The X-ray CT apparatus 1 performs beam hardening correction ( S13 ). The X-ray CT apparatus 1 performs beam hardening correction on the pre-processed projection data.

[0074] The X-ray CT apparatus 1 performs a Z filter addition process ( S14 ) The X-ray CT apparatus 1 performs a Z filter addition process on the projection data on which the beam hardening correction has been performed, and applies a filter in the column direction (Z direction).

[0075] The X-ray CT apparatus 1 performs image reconstruction and superposition processing ( S15 ). The X-ray CT apparatus 1 performs reconstruction function superposition processing by, for example, performing Fourier transform, multiplying by a reconstruction function, and then performing inverse Fourier transform.

[0076] The X-ray CT device 1 performs 3D back projection processing (S16). The X-ray CT device 1 performs 3D back projection processing on the projection data that has been subjected to reconstruction function superposition processing to obtain back projection data. In this embodiment, a spiral scan is performed, and the image reconstructed is subjected to 3D image reconstruction on a surface perpendicular to the Z axis, the XY plane. The following reconstruction area is parallel to the XY plane. The processing involved in the 3D back projection processing, for example, as a subroutine processing, is performed according to Figure 8 The following process shown is executed.

[0077] The X-ray CT device 1 extracts projection data corresponding to each pixel in the reconstruction area (S161). The X-ray CT device 1 focuses on one of the full views (i.e., a 360-degree view or a "180-degree + fan angle" view) required for image reconstruction of the tomogram, and extracts projection data corresponding to each pixel in the reconstruction area.

[0078] The X-ray CT apparatus 1 multiplies each projection data by the cone beam reconstruction weighting coefficient to create back projection data ( S162 ). The X-ray CT apparatus 1 multiplies each projection data by the cone beam reconstruction weighting coefficient to create back projection data.

[0079] The X-ray CT apparatus 1 adds the back-projection data to the projection data on a pixel-by-pixel basis (S163). The X-ray CT apparatus 1 adds the projection data to the back-projection data that has been cleaned in advance on a pixel-by-pixel basis.

[0080] The X-ray CT apparatus 1 determines whether the full view back projection data required for image reconstruction has been added (S164). The X-ray CT apparatus 1 determines whether the back projection data addition process has been performed for the full view (i.e., 360-degree view or "180-degree + fan angle" view) required for image reconstruction of the tomogram. When the process has not been performed for the full view (S164: No), a loop process is performed to implement the S161 process again. By performing this loop process, the X-ray CT apparatus 1 repeats the processes of S161 to S163 for the full view. When the process has been performed for the full view (S164: Yes), the X-ray CT apparatus 1 performs the process of S17.

[0081] The X-ray CT apparatus 1 performs post-processing ( S17 ). The X-ray CT apparatus 1 performs post-processing such as image filter superposition and CT value conversion on the back-projection data to obtain a tomogram.

[0082] The X-ray CT apparatus 1 performs image display (S18). The X-ray CT apparatus 1 displays the tomogram obtained by performing the post-processing on the monitor 23. The general operation of the X-ray CT apparatus 1 shown in this series of flows may be implemented using the processing described in, for example, Japanese Patent No. 5220374, Japanese Patent No. 5213016, or Japanese Patent Publication No. 2007-20906.

[0083] Fig. 9 This is an explanatory diagram of the data flow processed in image reconstruction using dual energy imaging. The X-ray CT device 1 performs image reconstruction into a monochrome tomogram by performing dual energy imaging. BH (beam hardening) correction is performed on the projection data formed by the high X-ray tube voltage (high X-ray tube voltage projection data) and the projection data formed by the low X-ray tube voltage (low X-ray tube voltage projection data) obtained by irradiating two different X-rays with high X-ray tube voltage values ​​and low X-ray tube voltage values. Thus, for example, when the first substance is water and the second substance is iodine (iodine), water density projection data and iodine density projection data are generated. In other words, multiple material density projection data can be obtained.

[0084] By processing these water density projection data and Iodine density projection data using filtered back projection, the image is reconstructed into a water density tomogram and an Iodine density tomogram. By linearly combining the reconstructed water density tomogram and the Iodine density tomogram, the image is reconstructed into a monochrome tomogram. Therefore, it is possible to reconstruct a dual-energy X-ray image that includes at least one of a plurality of material density tomograms and monochrome tomograms. The data flow processed in the image reconstruction using dual-energy imaging can also be implemented using the processing described in, for example, Japanese Patent No. 5220374, Japanese Patent No. 5213016, and Japanese Patent Publication No. 2012-245235.

[0085] According to the present embodiment, the X-ray CT apparatus 1 acquires the object information including the physical quantity and physical property information of the object H, and determines the X-ray imaging condition related information corresponding to the preferred X-ray quality (X-ray quality) of the object H based on the acquired object information. The X-ray CT apparatus 1 uses a predetermined simulation method to determine the X-ray imaging condition related information, so the X-ray imaging condition related information can be efficiently determined. The X-ray CT apparatus 1 can also determine the X-ray quality (X-ray quality) of the X-rays before and after the object H when collecting the X-ray data of two energies irradiated to the object H. By determining the X-ray imaging condition related information corresponding to the preferred X-ray quality of the object H as described above, the X-ray filter 53 can be optimized according to the physical quantity such as the size of the object H and the physical property information such as the material, so that the DE ratio at high X-ray tube voltage and low X-ray tube voltage is increased, and the collection, image shooting and image display of the dual energy imaging tomogram with the most preferred SNR (sound ratio) can be realized.

[0086] According to the present embodiment, the X-ray CT apparatus 1 determines the X-ray imaging conditions by determining the filter characteristics such as the filter type or thickness of the X-ray filter 53 with a high X-ray tube voltage and the X-ray filter 53 with a low X-ray tube voltage used when dual energy imaging is performed. Therefore, when dual energy imaging is performed, the X-ray filter 53 that can achieve the X-ray quality that is preferred for the object H to be detected can be efficiently selected. In addition, the X-ray CT apparatus 1 determines the information related to the X-ray imaging conditions by determining the tube voltage value of the high X-ray tube voltage and the tube voltage value of the low X-ray tube voltage used when dual energy imaging is performed. Therefore, when dual energy imaging is performed, each tube voltage value that can achieve the X-ray imaging conditions that are preferred for the object H to be detected can be efficiently selected.

[0087] (Implementation method 2)

[0088] Fig.10 This is a functional block diagram showing, by way of example, the functional units included in the X-ray CT apparatus 1 (central processing unit 3) according to Embodiment 2. The central processing unit 3 of the X-ray CT apparatus 1 according to Embodiment 2 is the same as that of Embodiment 1, and functions as an acquisition unit 31, an X-ray imaging condition determination unit 32, and an output unit 33 by executing a program stored in the storage device 24. The configurations of the acquisition unit 31 and the output unit 33 of Embodiment 2 are the same as those of the acquisition unit 31 and the output unit 33 of Embodiment 1.

[0089] The X-ray imaging condition determination unit 32 of the second embodiment includes a table reference unit 324, a filter characteristic determination unit 322, and an X-ray tube voltage determination unit 323. The table reference unit 324 refers to the X-ray imaging condition table 241 stored in the storage device 24 based on the object information output by the acquisition unit 31, and derives the X-ray tube voltage value (low tube voltage value and high tube voltage value) and the filter characteristics (filter type and filter thickness) corresponding to the physical quantity and physical characteristic information contained in the object information. The filter characteristic determination unit 322 and the X-ray tube voltage determination unit 323 determine the filter characteristics and the X-ray tube voltage value based on the derivation results of the table reference unit 324, and output them to the output unit 33.

[0090] Fig.112 is an explanatory diagram showing an example of an X-ray imaging condition table 241 (reference table). The X-ray imaging condition table 241 is stored in the storage device 24 and corresponds to a reference table that the central processing unit 3 refers to in the process of determining the X-ray imaging conditions. The structure of the X-ray imaging condition table 241 may be, for example, an information table as a simulation based on the first embodiment. The X-ray imaging condition table 241 is not limited to being stored in the storage device 24, but may be stored in another computer or storage device that is connected to the operation console 2 in a communicable manner, and the central processing unit 3 refers to the X-ray imaging condition table 241 by accessing the other computer from the operation console 2 (central processing unit 3).

[0091] The management items (metadata) of the X-ray imaging condition table 241 include, for example, physical quantity and physical characteristic information as items related to the detected object information, low tube voltage value and high tube voltage value as items related to the X-ray tube voltage value, and filter type and filter thickness as items related to the filter characteristics. Furthermore, the management items (metadata) related to the X-ray characteristic information of the X-ray imaging condition table 241 include, for example, items related to the X-ray characteristic information of the X-ray spectrum, the X-ray filter 53, and the 2D X-ray detector 7 (X-ray detector).

[0092] The physical quantity stores information related to the size and shape of the object H. The physical property information stores information related to the material of the object H. The X-ray spectrum, the X-ray filter 53, and the X-ray property information of the 2D X-ray detector 7 (X-ray detector) store specific X-ray property information. These object information and X-ray property information are equivalent to input factors for determining (deriving) X-ray imaging conditions including X-ray tube voltage values ​​and filter characteristics.

[0093] The low tube voltage value stores a low X-ray tube voltage value that is preferred when detecting the object H corresponding to the object information. The high tube voltage value stores a high X-ray tube voltage value that is preferred when detecting the object H corresponding to the object information.

[0094] The filter type stores information related to the filter type, such as the material of each X-ray filter 53 (the X-ray filter 53 through which high-energy X-rays pass and the X-ray filter 53 through which low-energy X-rays pass) that is preferred when detecting the object H corresponding to the object information. The filter thickness stores information related to the thickness size of each X-ray filter 53 (the X-ray filter 53 through which high-energy X-rays pass and the X-ray filter 53 through which low-energy X-rays pass) that is preferred when detecting the object H corresponding to the object information.

[0095] By combining the information such as the high X-ray tube voltage value, the low X-ray tube voltage value, the filter type and the filter thickness derived by referring to the X-ray imaging condition table 241, it is ensured that the X-ray quality preferred for the object H is achieved by combining the X-ray spectrum, the X-ray filter 53 and the 2D X-ray detector 7 (X-ray detector) with the object information.

[0096] Fig.12 1 is a flowchart showing the details of data collection (comparison table) in the general operation of the X-ray CT apparatus 1. The X-ray CT apparatus 1 of the second embodiment performs the processing of S11 to S18 in the same manner as the first embodiment. The X-ray CT apparatus 1 of the second embodiment performs the processing of S11 related to data collection, for example, as a subroutine processing, according to Fig.12 The following process shown is executed.

[0097] The X-ray CT apparatus 1 acquires object information, an X-ray spectrum, and X-ray characteristic information of the X-ray filter 53 and the 2D X-ray detector 7 (X-ray detector) ( S211 ). The X-ray CT apparatus 1 acquires object information similarly to the first embodiment.

[0098] The X-ray CT apparatus 1 determines the X-ray imaging conditions by referring to the X-ray imaging condition table 241 based on the acquired object information and X-ray characteristic information (S212). The X-ray CT apparatus 1 refers to the X-ray imaging condition table 241 stored in the storage device 24 based on the object information and X-ray characteristic information output by the acquisition unit 31, and derives the X-ray imaging conditions including the X-ray tube voltage values ​​(low tube voltage value and high tube voltage value) and filter characteristics (filter type and filter thickness) corresponding to the physical quantities and physical characteristic information contained in the object information. The X-ray radiation quality is determined based on these derived X-ray tube voltage values ​​(low tube voltage value and high tube voltage value) and filter characteristics (filter type and filter thickness).

[0099] The X-ray CT apparatus 1 derives a control parameter based on the determined X-ray imaging condition (S213). The X-ray CT apparatus 1 irradiates X-rays using the X-ray tube voltage value and the X-ray filter 53 selected based on the control parameter (S214). The X-ray CT apparatus 1 collects data detected by the 2D X-ray detector 7 (X-ray detector data) (S215). The X-ray CT apparatus 1 performs the processing of S213 to S215 in the same manner as S113 to S115 of the first embodiment.

[0100] According to the present embodiment, the X-ray CT apparatus 1 refers to the X-ray imaging condition table 241 (reference table) stored in advance in a predetermined storage area to determine (derive) the X-ray imaging conditions including the X-ray tube voltage value (low tube voltage value and high tube voltage value) and the filter characteristics (filter type and filter thickness), which are the determining factors for irradiating X-rays with a preferred X-ray quality. Therefore, the determination of the X-ray imaging conditions can be efficiently achieved.

[0101] In this embodiment, the X-ray CT apparatus 1 determines the X-ray imaging conditions by using the X-ray imaging condition table 241 based on the acquired object information and X-ray characteristic information, but the present invention is not limited thereto. The X-ray CT apparatus 1 may also determine the X-ray imaging conditions by using a determination algorithm contained in a program pre-stored in a predetermined storage area of ​​the storage device 24 or the like based on the acquired object information and X-ray characteristic information. The program structure containing the determination algorithm is: using the object information and X-ray characteristic information as input factors, and outputting an imaging condition that can achieve a sufficient SNR (noise ratio) for the object. Alternatively, the X-ray CT apparatus 1 may also determine the X-ray imaging conditions by using a learning model pre-stored in a predetermined storage area of ​​the storage device 24 or the like based on the acquired object information and X-ray characteristic information. The learning model has been learned, and outputs an imaging condition that can achieve a sufficient SNR (noise ratio) for the object by inputting the object information and X-ray characteristic information. The learning model, for example, can be a learning model constructed by a neural network (NN) that processes the information of the object to be detected of the image data of the object to be detected output by the camera unit 10 as input data, or other learning algorithms not limited to NN, wherein neural networks include CNN (Convolutional Neural Network), RCNN (Regions with Convolutional Neural Network), etc., and other learning algorithms include SVM (Support Vector Machine), Bayesian network, regression tree, etc.

[0102] It should be understood that the embodiments disclosed herein are illustrative in all aspects and not restrictive. The technical features described in the embodiments may be combined with each other, and all changes within the scope of the claims and the scope equivalent to the claims are intended to be included within the scope of the present invention.

[0103] [Explanation of symbols]

[0104] RX-ray inspection room

[0105] H Detected object

[0106] 1X-ray CT device

[0107] 2 Operation console

[0108] 21 Input Devices

[0109] 22 Data collection buffer memory

[0110] 23 Monitors

[0111] 24 Storage Devices

[0112] 241 X-ray photography conditions table

[0113] 3 Central Processing Unit

[0114] 31 Acquisition Department

[0115] 32X-ray radiography condition determination department

[0116] 321 Simulation Execution Department

[0117] 322 Filter characteristic determination unit

[0118] 323X-ray tube voltage determination unit

[0119] 324 Form Reference

[0120] 33 Output section

[0121] 4 Photography table

[0122] 5X-ray generator

[0123] 51X-ray tube

[0124] 52 Collimator

[0125] 53X-ray filter

[0126] 531 Bowtie filter

[0127] 54X-ray tube controller

[0128] 6. Operate the controller

[0129] 72D X-ray Detector

[0130] 8 Lifting mechanism

[0131] 9. Data Collection Device

[0132] 10. Camera Department.

Claims

1. An X-ray CT device, characterized in that: The invention comprises an X-ray generator and an X-ray detector for detecting X-rays emitted from the X-ray generator and penetrating an object to be detected, and is an X-ray CT device for collecting X-ray projection data of at least two X-ray energies and reconstructing them into a dual-energy image. And it has: an acquisition unit that acquires information of the object to be detected including physical quantity and physical characteristic information of the object to be detected, and X-ray spectrum, X-ray filter and X-ray characteristic information of the X-ray detector; An X-ray imaging condition determination unit determines respective X-ray imaging conditions when collecting X-ray projection data of at least two types of X-ray energies irradiated by the X-ray generating device, based on the information of the detected object acquired by the acquisition unit and the X-ray characteristic information of the X-ray spectrum, X-ray filter and X-ray detector.

2. The X-ray CT device according to claim 1, characterized in that: The X-ray imaging condition determination unit determines the respective X-ray imaging conditions when collecting X-ray projection data of at least two energies irradiated by the X-ray generating device, using a predetermined simulation method or a method referring to an information table based on the simulation, based on the information of the object to be detected and the X-ray spectrum, X-ray filter and X-ray characteristic information of the X-ray detector acquired by the acquisition unit.

3. The X-ray CT apparatus according to claim 1, characterized in that: The X-ray generator includes an X-ray filter through which the X-rays of at least the two X-ray energies pass and the X-ray quality is adjusted. The X-ray imaging condition determination unit determines the filter characteristics of each of the X-ray filters based on the detected object information acquired by the acquisition unit and the X-ray characteristic information of the X-ray spectrum, X-ray filter and X-ray detector, thereby determining the X-ray imaging conditions of the X-rays of each of the two X-ray energies.

4. The X-ray CT apparatus according to any one of claims 1 to 3, characterized in that: The X-ray imaging condition determination unit determines the X-ray tube voltage value, X-ray tube current value, imaging time and X-ray filter of the X-rays of the two X-ray energies based on the detected object information and X-ray spectrum, X-ray filter and X-ray characteristic information of the X-ray detector acquired by the acquisition unit, thereby determining the X-ray imaging conditions of the X-rays of the two X-ray energies.

5. The X-ray CT apparatus according to claim 1, characterized in that: The acquisition unit for acquiring the information of the detected object including the physical quantity and physical property information of the detected object acquires the information of the detected object based on at least one of the appearance image, positioning scan image and drawing information of the detected object.

6. The X-ray CT apparatus according to claim 1, characterized in that: An image reconstruction unit is provided for reconstructing an X-ray dual energy tomogram based on X-ray projection data detected by the X-ray detector, The image reconstruction unit obtains a plurality of material density projection data based on the collected X-ray projection data of at least two types of X-ray energies, and reconstructs the data into an X-ray dual energy tomogram including at least one of a plurality of material density tomograms and a monochromatic tomogram.

7. The X-ray CT apparatus according to any one of claims 1 to 6, characterized in that: The X-ray imaging condition determination unit determines the respective X-ray imaging conditions when collecting X-ray projection data of at least two types of energies irradiated by the X-ray generating device, based on the information of the object to be detected acquired by the acquisition unit and the X-ray spectrum, X-ray filter and X-ray characteristic information of the X-ray detector, using a comparison table, a judgment algorithm or a learning model pre-stored in a prescribed storage area.

8. A program product, comprising a computer program, wherein the computer program causes a computer to execute the following processing: Acquire information on the object to be detected, including physical quantity and physical property information of the object to be detected, obtained by X-rays of at least two X-ray energies emitted by an X-ray generator, and X-ray property information of an X-ray spectrum, an X-ray filter, and an X-ray detector, Based on the acquired information of the object to be detected and the X-ray characteristic information of the X-ray spectrum, X-ray filter and X-ray detector, the respective X-ray photography conditions are determined when collecting X-ray projection data of at least two types of X-ray energies irradiated by the X-ray generating device.

9. An information processing method for causing a computer to perform the following processing: Acquire information on the object to be detected, including physical quantity and physical property information of the object to be detected, obtained by X-rays of at least two X-ray energies emitted by an X-ray generator, and X-ray property information of an X-ray spectrum, an X-ray filter, and an X-ray detector, Based on the acquired information of the object to be detected and the X-ray characteristic information of the X-ray spectrum, X-ray filter and X-ray detector, the respective X-ray photography conditions are determined when collecting X-ray projection data of at least two types of X-ray energies irradiated by the X-ray generating device.

Images