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

Abstract

To provide an X-ray CT apparatus, etc. for more optimally determining an X-ray imaging condition for dual energy imaging according to an object to be examined as an object to be scanned.SOLUTION: An X-ray CT apparatus including an X-ray generator and an X-ray detector for detecting an X-ray emitted from the X-ray generator and passing through an object to be examined for collecting X-ray projection data on at least two kinds of X-ray energy and reconstructing a dual energy image includes: an acquisition unit for acquiring information on the object to be examined including a physical amount and physical property information on the object to be examined, and X-ray characteristic information on an X-ray spectrum, an X-ray filter, and the X-ray detector; and an X-ray imaging condition determination unit for determining each X-ray imaging condition when collecting the X-ray projection data on the at least two kinds of X-ray energy emitted from the X-ray generator on the basis of the information on the object to be examined, and the X-ray characteristic information on the X-ray spectrum, the X-ray filter, and the X-ray detector acquired by the acquisition unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Known X-ray CT devices are configured to perform dual energy imaging, in which one X-ray tube captures images while switching the X-ray tube voltage between a low voltage (e.g., 80 kV) and a high voltage (e.g., 140 kV) during scanning; dual energy imaging, in which two X-ray tubes capture images simultaneously at a low X-ray tube voltage (e.g., 80 kV) and a high voltage (e.g., 140 kV); dual energy imaging, in which a two-layer X-ray detector collects low and high X-ray energy components; and dual energy imaging, in which a semiconductor X-ray detector distinguishes between and collects low and high X-ray energy components. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-100913 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the X-ray CT device disclosed in Patent Document 1 does not consider the point of determining the X-ray imaging conditions for dual energy imaging more optimally according to different types of scan objects (inspected objects). The meaning of more optimal may include the point of increasing the ratio of the X-ray absorption coefficient of the subject at low and high X-ray tube voltages (dual energy ratio) and making the SN ratio at low and high X-ray tube voltages as equal as possible, taking into consideration the radiation quality of the 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. However, if a bowtie filter that controls the irradiated X-ray distribution in the channel direction of the imaging field of view exists, the X-ray filter may also include the bowtie filter.

[0005] In one aspect, an object of the present invention is to provide an X-ray CT apparatus and the like that can more optimally determine X-ray imaging conditions for dual energy imaging according to an object to be scanned. [Means for solving the problem]

[0006] An X-ray CT device in one embodiment of the present disclosure includes an X-ray generator and an X-ray detector that detects X-rays irradiated from the X-ray generator and passed through an object to be inspected, and collects X-ray projection data of at least two types of X-ray energies to reconstruct a dual energy image. The X-ray CT device is equipped with an acquisition unit that acquires object information including physical quantity and physical property information of the object to be inspected, and an X-ray spectrum, an X-ray filter, and X-ray characteristic information of the X-ray detector, and an X-ray imaging condition determination unit that determines each of the X-ray imaging conditions when collecting X-ray projection data of at least two types of X-ray energies irradiated from the X-ray generator, based on the object information and the X-ray spectrum, the X-ray filter, and the X-ray detector acquired by the acquisition unit. The X-ray CT device includes an X-ray filter, and by reconstructing dual energy images, multiple density tomographic images such as monochromatic tomographic images, water density tomographic images, and iodine density tomographic images of each keV (effective energy) are reconstructed.

[0007] A program in one aspect of the present disclosure causes a computer to acquire inspection object information including physical quantity and property information of an inspection object that is to be inspected by X-rays of at least two types of X-ray energies irradiated from an X-ray generating device, and X-ray characteristic information of an X-ray spectrum, an X-ray filter, and an X-ray detector, and executes a process of determining each of the X-ray shooting conditions when collecting X-ray projection data of at least two types of X-ray energies irradiated from the X-ray generating device based on the acquired inspection object information.

[0008] An information processing method according to one aspect of the present disclosure acquires inspection object information including physical quantity and property information of an inspection object to be inspected using X-rays of at least two types of X-ray energies irradiated from an X-ray generating device, and X-ray characteristic information of an X-ray spectrum, an X-ray filter, and an X-ray detector, and causes a computer to execute a process of determining each of the X-ray shooting conditions when collecting X-ray projection data of at least two types of X-ray energies irradiated from the X-ray generating device based on the acquired inspection object information. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide an X-ray CT apparatus or the like that determines the X-ray imaging conditions for dual energy imaging more optimally according to the object to be scanned. The meaning of more optimal may include increasing the ratio of the X-ray absorption coefficient of the subject at low and high X-ray tube voltages (dual energy ratio) in consideration of the radiation quality of the X-rays output from the X-ray tube and passed through the X-ray filter and the energy detection distribution of the X-ray detector, and making the SN ratio at low and high X-ray tube voltages as similar as possible. However, if a bowtie filter that controls the irradiated X-ray distribution in the channel direction of the imaging field of view is present, the X-ray filter may also include the bowtie filter. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing an overview of an X-ray CT apparatus according to a first embodiment. [Diagram 2]FIG. 2 is an explanatory diagram showing the rotation of an X-ray generator and a two-dimensional X-ray detector. [Diagram 3] FIG. 2 is a functional block diagram illustrating functional units included in the X-ray CT apparatus (central processing unit). [Figure 4] FIG. 2 is a flow chart showing a schematic operation of the X-ray CT apparatus. [Diagram 5] FIG. 2 is a flow chart showing details of data collection in the general operation of the X-ray CT apparatus. [Figure 6] FIG. 11 is a flow diagram showing details of the determination (simulation) of X-ray imaging conditions in data collection by the X-ray CT scanner. [Figure 7] FIG. 4 is a flowchart showing details of pre-processing in the general operation of the X-ray CT apparatus. [Figure 8] FIG. 11 is a flowchart showing a three-dimensional backprojection process in the schematic operation of the X-ray CT apparatus. [Figure 9] FIG. 11 is an explanatory diagram showing the flow of data processed in screen reconstruction by dual energy imaging. [Figure 10] 10 is a functional block diagram illustrating functional units included in the X-ray CT apparatus (central processing unit) according to the second embodiment. FIG. [Figure 11] FIG. 2 is an explanatory diagram illustrating an example of an X-ray imaging condition table (lookup table). [Figure 12] FIG. 2 is a flow chart showing details of data collection (lookup table) in the general operation of the X-ray CT apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (Embodiment 1) Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments. Fig. 1 is a schematic diagram showing an overview of an X-ray CT device 1 according to the first embodiment. The X-ray CT device 1 includes an operation console 2, an imaging table 4 arranged in an X-ray examination room R, an X-ray generator 5, a controller 6, a two-dimensional X-ray detector 7, a lifting mechanism 8, and a data acquisition device 9 (DAS: Data Acquisition System). Furthermore, an imaging unit 10 is provided in the X-ray examination room R, and the imaging unit 10 is connected to the operation console 2 so as to be able to communicate with the X-ray CT device 1, and may be configured as a part of the X-ray CT device 1.

[0012] The operation console 2 includes an input device 21 , a data collection buffer 22 , a monitor 23 , a storage device 24 and a central processing unit 3 .

[0013] The input device 21 may be, for example, a user-operated input device such as a keyboard or a mouse, or a communication-type input / output I / F into which data transmitted from another computer is input.

[0014] The data collection buffer 22 is communicatively connected to the central processing unit 3 and a data collection device 9 arranged in the X-ray examination room R, and outputs the X-ray detector data acquired from the data collection device 9 to the central processing unit 3.

[0015] 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 (a dual energy image, an X-ray dual energy tomographic image) reconstructed from the X-ray detector data is displayed on the monitor 23. The central processing unit 3 executes a program stored in the memory device 24 to function as an image reconstruction unit that reconstructs an X-ray dual energy tomographic image based on the X-ray projection data detected by the two-dimensional X-ray detector 7 (X-ray detector).

[0016] The storage device 24 includes a volatile storage area such as a static random access memory (SRAM), a dynamic random access memory (DRAM), a flash memory, etc., and a non-volatile storage area such as an EEPROM or a hard disk. The storage device 24 stores in advance the programs executed by the central processing unit 3 and data referenced during processing. The programs stored in the storage device 24 may be programs read from a recording medium readable by the operation console 2. Alternatively, the programs may be downloaded from an external computer (not shown) connected to a communication network (not shown) and stored in the storage device 24.

[0017] The central processing unit 3 has an arithmetic processing device equipped with a timing function, such as one or more CPUs (Central Processing Units), MPUs (Micro-Processing Units), GPUs (Graphics Processing Units), etc., and performs various information processing, control processing, etc. related to the X-ray CT device 1, including processing related to the reconstruction of tomographic images, by reading and executing programs stored in the memory device 24.

[0018] The X-ray generating device 5 includes an X-ray tube controller 54, an X-ray tube 51, an X-ray filter 53, a bowtie filter 531, and a collimator 52, and is configured to enable dual energy imaging using high energy and low energy by using at least two types of X-ray energy.

[0019] The X-ray tube controller 54 is communicatively connected to the control controller 6, and changes the tube voltage of the X-ray tube 51 based on the control signal and high voltage output from the control controller 6, and controls the start and stop of X-ray irradiation from the X-ray tube 51. The X-ray tube controller 54 may be configured, for example, by a microcomputer or the like in which a control unit such as a CPU and a storage unit are packaged.

[0020] The X-ray tube 51 irradiates, for example, high-energy X-rays and low-energy X-rays. The tube voltage of each of the X-ray tubes 51 corresponding to high energy and low energy is determined based on a control signal and a high voltage from the X-ray tube controller 54.

[0021] The X-ray filters 53 are provided corresponding to the high-energy and low-energy X-ray tubes 51, respectively, and include an X-ray filter 53 through which high-energy X-rays pass and an X-ray filter 53 through which low-energy X-rays pass. The X-ray filter 53 is provided with a filter characteristic variable mechanism for varying the filter characteristics, and can change the filter characteristics based on a control signal output from the control controller 6 or the X-ray tube controller 54. The filter characteristics (X-ray filter characteristics) are determined based on, for example, the material of the filter and the thickness of the filter (the distance through which X-rays pass). The X-ray filter 53 can be replaced with a filter of a different material, for example, a lead filter with an iron filter, or a filter of the same material but with a different thickness, by the filter characteristic variable mechanism provided in the X-ray filter 53 based on a control signal from the control controller 6 or the like. The bowtie filter 531 changes the X-ray absorption coefficient in the channel direction of the imaging field of view to control the irradiated X-ray distribution in the channel direction.

[0022] The quality of the X-rays changes depending on the tube voltage value of the X-ray tube 51 or the filter characteristics of the X-ray filter 53. Since the X-ray generator 5 is configured to vary the tube voltage value and the X-ray filter characteristics, high-energy and low-energy X-rays of appropriate quality are irradiated onto the object to be inspected H, thereby enabling efficient dual-energy imaging.

[0023] The collimator 52 includes, for example, a slice thickness direction collimator and a channel direction collimator, and collimates and shapes the X-rays generated from the X-ray tube 51 .

[0024] An object H to be inspected is placed on the imaging table 4, which rotates at a predetermined number of revolutions in response to a control signal output from the controller 6. As the imaging table 4 rotates, X-rays are irradiated over the entire circumference of the object H to be inspected placed on the imaging table 4. In this embodiment, the imaging table 4 is not limited to being rotated, and the imaging table 4 may be fixed, and the X-ray generator 5, the two-dimensional X-ray detector 7, and the data collector 9 may rotate relative to the imaging table 4. In other words, the imaging table 4, the X-ray generator 5, the two-dimensional X-ray detector 7, and the data collector 9 may be rotated relatively to the imaging table 4, so that X-rays are irradiated over the entire circumference of the object H in the rotation direction.

[0025] The lifting mechanism 8 is configured to lift and lower the imaging table 4 or the X-ray generator 5, the two-dimensional X-ray detector 7, and the data collecting device 9, so that the imaging table 4, the X-ray generator 5, the two-dimensional X-ray detector 7, and the data collecting device 9 move relatively in the vertical direction. The lifting mechanism 8 moves the imaging table 4, the X-ray generator 5, etc. relatively in the vertical direction based on a control signal output from the controller 6. This makes it possible to irradiate the X-rays over the entire area of ​​the object H in the vertical direction (height direction).

[0026] The control controller 6 is communicatively connected to the central processing unit 3 of the operation console 2, and controls or drives the X-ray generator 5, the radiography table 4, the lifting mechanism 8, the two-dimensional X-ray detector 7, and the data collecting device 9 based on instruction information output from the central processing unit 3. The control controller 6 may be configured, for example, by a microcomputer or the like in which a control unit such as a CPU and a storage unit are packaged.

[0027] The two-dimensional X-ray detector 7 has, for example, a plurality of detector rows (X-ray detector channels). The two-dimensional X-ray detector 7 has a plurality of channels that detect X-rays transmitted through the inspection object H and collect X-ray detector data, which are arranged in a channel direction along the direction in which the inspection object H is relatively rotated and in a row direction along the rotation axis when the inspection object H is rotated.

[0028] The data acquisition device 9 acquires X-ray detector data from the two-dimensional X-ray detector 7 , and outputs the X-ray detector data to the central processing unit 3 via a data acquisition buffer 22 .

[0029] The imaging unit 10 is, for example, a camera, and is provided in the X-ray inspection room R, such as above the imaging table 4, so that the entire object H placed on the imaging table 4 is captured within the imaging range. The imaging unit 10 outputs image data of the object H captured by the imaging unit 10 to the operation console 2 (central processing unit 3). The imaging unit 10 corresponds to an object information acquisition device for acquiring 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, and may be a 3D scanner device or a 3D dimension measuring device. These devices included in the X-ray CT device 1 may have the same configurations, actions, and functions as the devices of the X-ray CT device 1 described in, for example, Japanese Patent Publication No. 5220374, Japanese Patent Publication No. 5213016, and Japanese Patent Publication No. 2007-20906.

[0030] 2 is an explanatory diagram showing the rotation of the X-ray generator 5 and the two-dimensional X-ray detector 7. The X-ray tube 51 and the two-dimensional X-ray detector 7 rotate around the center of rotation, which is the center of the imaging table, relative to the imaging table. When the vertical direction is the Y direction, the horizontal direction is the X direction, and the table travel direction perpendicular to these is the Z direction, the rotation plane of the X-ray tube 51 and the two-dimensional X-ray detector 7 is the XY plane.

[0031] The X-ray tube 51 generates an X-ray beam called a cone beam. The view angle is 0° when the central axis direction of the cone beam is parallel to the Y direction. The two-dimensional X-ray detector 7 has, for example, 300 channels x 3000 detector rows. In the two-dimensional X-ray detector 7, a plurality of channels that detect X-rays transmitted through the subject and collect X-ray detector data are arranged in a channel direction along the direction in which the subject H is relatively rotated by the imaging table 4 or the like, and in a row direction along the axis of rotation during rotation.

[0032] X-rays are irradiated and the collected X-ray detector data is A / D converted by the data collection device 9 from the two-dimensional X-ray detector 7 and output to the data collection buffer 22. The data input to the data collection buffer 22 is processed by the central processing unit 3, and the data is reconstructed into a tomographic image and displayed on the monitor 23.

[0033] 3 is a functional block diagram illustrating functional units included in the X-ray CT apparatus 1 (central processing unit 3). The central processing unit 3 of the X-ray CT apparatus 1 executes a program stored in the storage device 24 to function as an acquisition unit 31, an X-ray imaging condition determination unit 32, and an output unit 33. The program includes program modules or subroutines related to a simulation executed by a simulation execution unit 321, which will be described later.

[0034] The acquiring unit 31 acquires image data of the object H to be inspected output from the imaging unit 10. Alternatively, the acquiring unit 31 may acquire physical quantities such as the shape and size of the object H to be inspected, and physical property information such as the material, input from the operator of the operation console 2 via the input device 21. The physical quantities and physical property information of the object H to be inspected are, for example, in the form of drawing information (three-dimensional CAD data) of the object H to be inspected, and the acquiring unit 31 may acquire the drawing information of the object H to be inspected via the input device 21 having a communication I / F function or a communication device for communicating with another computer. Alternatively, the acquiring unit 31 may acquire, for example, a scout image captured as a positioning image from the data collection buffer 22.

[0035] The acquisition unit 31 derives physical quantities such as the shape and size of the object H and physical property information such as the material based on the image data, drawing information, or scout image of the object H thus acquired, and outputs the derived physical quantities and physical property information to the X-ray imaging condition determination unit 32. The acquisition unit 31 may derive the physical quantities and physical property information based on the image data, for example, by pattern matching the image of the object H extracted by edge detection. Alternatively, the acquisition unit 31 may detect the object H from the image data using an object detection algorithm having a function of a segmentation network that performs object detection, such as a learning model configured by RCNN, SSD (Single Shot Multibook Detector), YOLO (You Only Look Once), etc., and derive the physical quantities and physical property information of the object H. Alternatively, the acquisition unit 31 may derive the physical quantities and physical property information of the object H using a 3D scanner device or a 3D dimension measurement device.

[0036] Furthermore, the acquiring unit 31 acquires the X-ray spectrum, the X-ray filter 53, and X-ray characteristic information of the two-dimensional X-ray detector 7 (X-ray detector) from, for example, the data collection buffer 22. The acquiring unit 31 outputs the acquired X-ray characteristic information and inspection object information (physical quantity and property information of the inspection object) to the X-ray imaging condition determining unit 32.

[0037] 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 a simulation using the X-ray characteristic information output by the acquisition unit 31 and the physical quantity and property information of the object H as input factors to determine X-ray imaging conditions that are suitable or more optimal for inspecting the object H. The meaning of being more optimal includes the point of increasing the ratio (dual energy ratio) of the X-ray absorption coefficient of the object H at low and high X-ray tube voltages in consideration of the radiation quality of the X-rays output from the X-ray tube and passing through the X-ray filter 53 and the energy detection distribution of the two-dimensional X-ray detector 7 (X-ray detector), and making the SN ratio at low and high X-ray tube voltages as similar as possible. The X-ray imaging conditions can provide suitable or more optimal X-ray radiation quality. The simulation execution unit 321 judges 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 ratio at the low voltage and the high voltage of the X-ray tube voltage is as equal as possible, and determines the X-ray imaging condition suitable for inspecting the inspection object H based on the judgment result. The predetermined condition is, for example, a condition that the SNR (noise ratio) at the low X-ray tube voltage and the high X-ray tube voltage derived by the simulation is equal to or less than a predetermined value. Alternatively, the simulation execution unit 321 may derive a DE (Dual Energy) ratio between 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 inspection object H, which are input factors, and perform an optimization simulation to increase the DE ratio. The filter characteristic determination unit 322 determines the filter characteristics of each of the high energy and low energy X-ray filters 53 based on the simulation result by 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 based on the results of the simulation performed by the simulation execution unit 321 .The X-ray imaging condition determination unit 32 may determine the X-ray imaging conditions for the X-rays of each of the two types of X-ray energies by determining the X-ray tube voltage value, X-ray tube current value, imaging time, and X-ray filter 53 for each of the X-rays of the two types of X-ray energies based on the object information acquired by the acquisition unit 31 and the X-ray characteristic information of the X-ray spectrum, the X-ray filter 53, and the two-dimensional X-ray detector 7 (X-ray detector).

[0038] The radiation quality of the X-ray changes depending on the tube voltage value of the X-ray tube 51 or the filter characteristics of the X-ray filter 53. Therefore, it is possible to determine the X-ray imaging conditions that will result in the radiation quality of the X-ray 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. The X-ray imaging condition determination unit 32 outputs information on the X-ray imaging conditions, including the determined filter characteristics and the X-ray tube voltage value, to the output unit 33.

[0039] The output unit 33 generates information on control parameters for controlling the X-ray generator 5 based on information on X-ray imaging conditions acquired from the X-ray imaging condition determination unit 32, and outputs the information on the control parameters to the control controller 6. The information on X-ray imaging conditions includes information on filter characteristics and X-tube voltage value, and the output unit 33 generates information on the control parameters based on the filter characteristics and X-tube voltage value, and outputs it to the control controller 6.

[0040] Based on the control parameters output from the output unit 33, the control controller 6 controls the setting of the tube voltage value of the X-ray tube 51 and the setting of filter characteristics by changing or adjusting the X-ray filter 53. Alternatively, the control controller 6 may output information on X-ray imaging conditions including filter characteristics and X-ray tube voltage value to the control controller 6, and the control controller 6 may output control parameters generated based on these filter characteristics and X-ray tube voltage value to the X-ray tube controller 54 and the X-ray filter 53 to control the X-ray tube 51 and the X-ray filter 53.

[0041] Although the central processing unit 3 of the operation console 2 is used, the present invention is not limited to this and may be processed by other controllers such as a control controller. Alternatively, a group of devices having an information calculation function such as the central processing unit 3, the control controller, and the X-ray controller may work together as a series of functional units. Alternatively, these functional units may be performed by an external server communicably connected to the central processing unit 3 of the operation console 2 via an external network such as the Internet, and the central processing unit 3 of the operation console 2 may acquire the processing result by the external server and function as a series of functional units based on the acquired processing result.

[0042] FIG. 4 is a flow diagram showing the general operation of the X-ray CT device 1. FIG. 5 is a flow diagram showing details of data collection (simulation) in the general operation of the X-ray CT device 1. FIG. 6 is a flow diagram showing details of determination (simulation) of X-ray imaging conditions in data collection by the X-ray CT device. FIG. 7 is a flow diagram showing details of pre-processing in the general operation of the X-ray CT device 1. FIG. 8 is a flow diagram showing three-dimensional back projection processing in the general operation of the X-ray CT device 1. The X-ray CT device 1 starts the processing or operation of the flowchart based on instruction data including operation instructions inputted via the operation console 2, for example.

[0043] The X-ray CT apparatus 1 performs data collection (S11). The process related to the data collection is performed, for example, as a subroutine process according to the following flow shown in FIG.

[0044] The X-ray CT device 1 acquires the object information, the X-ray spectrum, and the X-ray characteristic information of the X-ray filter 53 and the two-dimensional X-ray detector 7 (X-ray detector) (S111). The X-ray CT device 1 acquires the object information of the object H, such as the image data of the object H output from the imaging unit 10, the information of the object H input from the input device 21, or a scout image of the object H. Furthermore, the X-ray CT device 1 acquires the X-ray spectrum, and the X-ray characteristic information of the X-ray filter 53 and the two-dimensional X-ray detector 7 (X-ray detector).

[0045] The X-ray CT apparatus 1 performs a simulation based on the acquired subject information and X-ray characteristic information to determine X-ray imaging conditions (S112). The process for determining the X-ray imaging conditions is performed, for example, as a sub-routine process, according to the following flow shown in FIG. 6.

[0046] The X-ray CT apparatus 1 derives X-ray spectra of various low X-ray tube voltages and high X-ray tube voltages (S1121). The X-ray CT apparatus 1 derives X-ray spectra of various low X-ray tube voltages and high X-ray tube voltages, for example, by measuring with an X-ray flat panel equipped with a scintillator and a photodiode. Alternatively, the X-ray CT apparatus 1 may obtain X-ray spectra of various low X-ray tube voltages and high X-ray tube voltages by simulation.

[0047] The X-ray CT apparatus 1 derives the X-ray spectrum emitted from the X-ray tube based on the material and thickness of the opening of the X-ray tube (S1122). The X-ray CT apparatus 1 derives the X-ray spectrum after the X-ray filter 53 (after passing through the X-ray filter 53) with various materials and thicknesses of the X-ray filter 53 (S1123). The X-ray CT apparatus 1 obtains, for example, by referring to the storage device 24, the material and thickness of the opening of the X-ray tube and the various materials and thicknesses of the X-ray filter 53 stored in the storage device 24. The X-ray CT apparatus 1 derives the X-ray spectrum based on the obtained information.

[0048] The X-ray CT apparatus 1 derives the X-ray spectrum after passing through the subject (the object to be examined) (S1124). The X-ray CT apparatus 1 obtains the X-ray spectrum that can be captured by the scintillator and predicts the resulting X-ray dose (S1125). The X-ray CT apparatus 1 obtains, for example, the X-ray spectrum that can be captured by the scintillator included in the X-ray flat panel and predicts the resulting X-ray dose.

[0049] The X-ray CT device 1 completes the simulation for both the low X-ray tube voltage and the high X-ray tube voltage, and judges whether or not imaging conditions that provide a sufficient SNR (noise ratio) have been obtained (S1126). The X-ray CT device 1 judges whether or not the low X-ray tube voltage and the high X-ray tube voltage derived by the simulation satisfy, for example, a predetermined condition related to the SNR (noise ratio). The predetermined condition is, for example, a condition that the SNR (noise ratio) due to the low X-ray tube voltage and the high X-ray tube voltage derived by the simulation is equal to or less than a predetermined value. If imaging conditions that provide a sufficient SNR (noise ratio) have not been obtained (S1126: NO), the X-ray CT device 1 performs a loop process to execute S1121 again. When performing the loop process if imaging conditions that provide a sufficient SNR (noise ratio) have not been obtained by the simulation, the X-ray CT device 1 (the central processing unit 3) may perform an iteration process in which a set value (input factor) for executing the simulation is changed in units of a predetermined number and repeated. Alternatively, when simulating a low X-ray tube voltage and a high X-ray tube voltage, the X-ray CT device 1 may derive a DE (Dual Energy) ratio between 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), and perform an optimization simulation to increase the DE ratio.

[0050] When the imaging conditions that provide a sufficient SNR (Signal to Noise Ratio) are obtained (S1126: YES), the X-ray CT device 1 determines the imaging conditions based on the optimal low and high X-ray tube voltages and X-ray filter conditions (S1127). The X-ray CT device 1 executes the process of S1121 and then executes the process of S113. The X-ray CT device 1 is not limited to the case where it executes the process of S1121 and then executes the process of S113 and thereafter. After executing the process of S1121, the X-ray CT device 1 collects and captures data at 80 kV and 140 kV, and reconstructs a dual energy image. Furthermore, the X-ray CT device 1 may display the reconstructed dual energy image, and may display a monochromatic tomographic image, a water density image, an iodine density image, or the like.

[0051] The X-ray CT device 1 derives control parameters according to the determined X-ray imaging conditions (S113). The X-ray CT device 1 determines the filter characteristics of the high-energy and low-energy X-ray filters 53 and the X-tube voltage values ​​of the high-energy and low-energy X-ray tubes 51, which are X-ray imaging conditions of the simulation results, and derives control parameters for controlling the X-ray generator 5 based on the determined filter characteristics and X-tube voltage values. A series of processes from S111 to S113 may be performed by, for example, the central processing unit 3 of the operation console 2 included in the X-ray CT device 1. Alternatively, the central processing unit 3 and the controller 6 may cooperate to perform a series of processes.

[0052] The X-ray CT device 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 device 1 selects or sets the X-ray tube voltage value and the X-ray filter 53 based on the derived control parameters, and irradiates X-rays under the set conditions. The X-ray CT device 1 collects data (X-ray detector data) detected by the two-dimensional X-ray detector 7 (S115).

[0053] The X-ray CT apparatus 1 performs pre-processing (S12). The pre-processing is performed, for example, as a subroutine process according to the following flow shown in FIG. 7. The X-ray CT apparatus 1 performs offset correction (S121). The X-ray CT apparatus 1 performs logarithmic conversion (S122). The X-ray CT apparatus 1 performs X-ray dose correction (S123). The X-ray CT apparatus 1 performs sensitivity correction (S124). The pre-processing includes the offset correction, logarithmic conversion, X-ray dose correction, and sensitivity correction. The X-ray CT apparatus 1 performs pre-processing on the X-ray detector data and converts it into projection data.

[0054] 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.

[0055] The X-ray CT apparatus 1 performs Z-filter convolution processing (S14). The X-ray CT apparatus 1 performs Z-filter convolution processing, which applies a filter in the row direction (Z direction) to the beam-hardening-corrected projection data.

[0056] The X-ray CT apparatus 1 performs image reconstruction and convolution processing (S15). The X-ray CT apparatus 1 performs reconstruction function convolution processing, for example, by performing Fourier transform, multiplying by a reconstruction function, and performing inverse Fourier transform.

[0057] The X-ray CT apparatus 1 performs a three-dimensional back projection process (S16). The X-ray CT apparatus 1 performs a three-dimensional back projection process on the projection data that has been subjected to the reconstruction function convolution process to obtain back projection data. In this embodiment, a helical scan is performed, and the image that is reconstructed is a three-dimensional image reconstructed on a plane perpendicular to the Z axis, the XY plane. The following reconstruction region is parallel to the XY plane. The processing related to the three-dimensional back projection process is performed, for example, as a subroutine process according to the following flow shown in FIG. 8.

[0058] The X-ray CT apparatus 1 extracts projection data corresponding to each pixel in the reconstruction area (S161). The X-ray CT apparatus 1 focuses on one view among all views required for image reconstruction of a tomographic image (i.e., 360-degree views or "180-degree + fan angle" views), and extracts projection data corresponding to each pixel in the reconstruction area.

[0059] The X-ray CT apparatus 1 multiplies each projection data by the cone beam reconstruction weighting coefficient to generate back projection data (S162). The X-ray CT apparatus 1 multiplies the projection data by the cone beam reconstruction weighting coefficient to generate back projection data.

[0060] The X-ray CT apparatus 1 adds the back projection data to the projection data in a pixel-by-pixel correspondence (S163). The X-ray CT apparatus 1 adds the projection data to the back projection data that has been cleared in advance in a pixel-by-pixel correspondence.

[0061] The X-ray CT apparatus 1 determines whether or not the backprojection data of all views required for image reconstruction has been added (S164). The X-ray CT apparatus 1 determines whether or not the addition process of the backprojection data has been performed for all views required for image reconstruction of a tomographic image (i.e., 360-degree views or "180-degree + fan angle" views). If the process has not been performed for all views (S164: NO), the X-ray CT apparatus 1 performs a loop process to execute the process of S161 again. By performing this loop process, the X-ray CT apparatus 1 repeats the processes of S161 to S163 for all views. If the process has been performed for all views (S164: YES), the X-ray CT apparatus 1 executes the process of S17.

[0062] The X-ray CT apparatus 1 performs post-processing (S17). The X-ray CT apparatus 1 performs post-processing such as image filter convolution and CT value conversion on the backprojection data to obtain a tomographic image.

[0063] The X-ray CT apparatus 1 displays the image (S18). The X-ray CT apparatus 1 displays the tomographic image obtained by performing post-processing on the monitor 23. The general operation of the X-ray CT apparatus 1 shown in this series of flows may be performed using the processes described in, for example, Japanese Patent No. 5220374, Japanese Patent No. 5213016, and Japanese Patent Laid-Open No. 2007-20906.

[0064] FIG. 9 is an explanatory diagram showing the flow of data processed in image reconstruction by dual energy imaging. The X-ray CT device 1 performs a process of image reconstruction of a monochromatic tomographic image by performing dual energy imaging. BH (beam hardening) correction is performed on each of projection data by a high X-ray tube voltage (high X-ray tube voltage projection data) and projection data by a low X-ray tube voltage (low X-ray tube voltage projection data) obtained by irradiating two different types of X-rays, a high X-ray tube voltage value and a low X-ray tube voltage value. As a result, for example, when the first substance is water and the second substance is iodine, water density projection data and iodine density projection data are generated. That is, a plurality of substance density projection data can be obtained.

[0065] The water density projection data and the iodine density projection data are processed using a filtered back projection method, whereby a water density tomogram and an iodine density tomogram are image-reconstructed. The reconstructed water density tomogram and the iodine density tomogram are linearly combined to image-reconstruct a monochromatic tomogram. Thus, a dual-energy X-ray image including at least one of a plurality of material density tomograms and monochromatic tomograms can be reconstructed. The flow of data processed in the image reconstruction by the dual-energy imaging may be performed using the processes described in, for example, Japanese Patent Publication No. 5220374, Japanese Patent Publication No. 5213016, and Japanese Patent Publication No. 2012-245235.

[0066] According to this embodiment, the X-ray CT device 1 acquires information on the object H including the physical quantity and property information thereof, and determines information on the X-ray imaging conditions corresponding to the X-ray radiation quality (X-ray radiation quality) suitable for the object H based on the acquired information on the object H. The X-ray CT device 1 determines information on the X-ray imaging conditions using a simulation method determined in advance, and therefore can efficiently determine information on the X-ray imaging conditions. The X-ray CT device 1 may determine the radiation quality (X-ray radiation quality) of the X-rays before and after the object H when collecting X-ray data of two types of energy irradiated to the object H. By determining information on the X-ray imaging conditions suitable for the X-ray radiation quality suitable for the object H in this way, the X-ray filter 53 can be optimized so that the DE ratio is large at high X-ray tube voltage and low X-ray tube voltage according to the physical quantity such as the size of the object H and property information such as the material, and a dual energy imaging tomographic image with an optimal SNR (noise ratio) can be collected, reconstructed, and displayed.

[0067] According to this embodiment, the X-ray CT device 1 determines the X-ray imaging conditions by determining the filter characteristics based on the filter type or thickness of each 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 in performing dual energy imaging. Therefore, when performing dual energy imaging, the X-ray filter 53 that provides an X-ray radiation quality suitable for the object H can be efficiently selected. Furthermore, the X-ray CT device 1 determines information on 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 in performing dual energy imaging. Therefore, when performing dual energy imaging, each tube voltage value that provides an X-ray imaging condition suitable for the object H can be efficiently selected.

[0068] (Embodiment 2) 10 is a functional block diagram illustrating 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 executes a program stored in the storage device 24, as in embodiment 1, to function as an acquisition unit 31, an X-ray imaging condition determination unit 32, and an output unit 33. The acquisition unit 31 and the output unit 33 of embodiment 2 have the same configuration as the acquisition unit 31 and the output unit 33 of embodiment 1.

[0069] 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 subject object information output from the acquisition unit 31, and derives 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 quantity and physical property information included in the subject 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 result of the table reference unit 324, and output them to the output unit 33.

[0070] 11 is an explanatory diagram illustrating an example of an X-ray imaging condition table 241 (lookup table). The X-ray imaging condition table 241 is stored in the storage device 24, and corresponds to a lookup table that the central processing unit 3 refers to in the process of determining the X-ray imaging conditions. The X-ray imaging condition table 241 may be configured as an information table based on the simulation of the first embodiment, for example. 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 communicably connected from the operation console 2, and the central processing unit 3 may refer to the X-ray imaging condition table 241 by accessing the other computer or the like from the operation console 2 (central processing unit 3).

[0071] The X-ray imaging condition table 241 includes, as management items (metadata), for example, physical quantity and physical property information which are items related to information of an object to be inspected, low and high tube voltage values ​​which are items related to X-ray tube voltage values, and filter type and filter thickness which are items related to filter characteristics. Furthermore, the X-ray imaging condition table 241 includes, as management items (metadata) related to X-ray characteristic information, for example, items related to X-ray spectrum, X-ray filter 53, and X-ray characteristic information of the two-dimensional X-ray detector 7 (X-ray detector).

[0072] The physical quantity stores information about the size and shape dimensions of the object H to be inspected. The physical property information stores information about the material and ingredients of the object H to be inspected. The X-spectrum, the X-ray filter 53, and the X-ray characteristic information of the two-dimensional X-ray detector 7 (X-ray detector) store X-ray characteristic information specific to each of them. The object information and X-ray characteristic information correspond to input factors for determining (deriving) X-ray imaging conditions including the X-ray tube voltage value and the filter characteristics.

[0073] The low tube voltage value stores a low X-ray tube voltage value suitable for inspecting the object H of the corresponding object information. The high tube voltage value stores a high X-ray tube voltage value suitable for inspecting the object H of the corresponding object information.

[0074] The filter type stores information on the filter type such as the material of each of the X-ray filters 53 (X-ray filters 53 through which high-energy X-rays pass and X-ray filters 53 through which low-energy X-rays pass) suitable for inspecting the object H of the corresponding object information. The filter thickness stores information on the thickness dimension of each of the X-ray filters 53 (X-ray filters 53 through which high-energy X-rays pass and X-ray filters 53 through which low-energy X-rays pass) suitable for inspecting the object H of the corresponding object information.

[0075] These high X-ray tube voltage values, low X-ray tube voltage values, filter types and filter thicknesses derived by referring to the X-ray shooting condition table 241 are combined to provide an X-ray radiation quality suitable for the object to be inspected H, which is identified by a combination of the X-ray spectrum, the X-ray filter 53 and the X-ray characteristic information of the two-dimensional X-ray detector 7 (X-ray detector), and the object to be inspected information.

[0076] Fig. 12 is a flow diagram showing details of data collection (lookup table) in the general operation of the X-ray CT device 1. The X-ray CT device 1 of the second embodiment performs processes from S11 to S18 in the same manner as in the first embodiment. In the X-ray CT device 1 of the second embodiment, the process related to data collection in S11 is performed, for example, as a subroutine process according to the following flow shown in Fig. 12.

[0077] The X-ray CT apparatus 1 acquires the object information, the X-ray spectrum, and the X-ray characteristic information of the X-ray filter 53 and the two-dimensional X-ray detector 7 (X-ray detector) (S211). The X-ray CT apparatus 1 acquires the object information in the same manner as in the first embodiment.

[0078] The X-ray CT device 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 device 1 derives the X-ray imaging conditions including the X-ray tube voltage value (low tube voltage value and high tube voltage value) and the filter characteristic (filter type and filter thickness) corresponding to the physical quantity and physical property information included in the X-ray characteristic information and the object information by referring to the X-ray imaging condition table 241 stored in the storage device 24 based on the object information and the X-ray characteristic information output from the acquisition unit 31. The X-ray radiation quality is determined based on the derived X-ray tube voltage value (low tube voltage value and high tube voltage value) and the filter characteristic (filter type and filter thickness).

[0079] The X-ray CT apparatus 1 derives control parameters according to the determined X-ray imaging conditions (S213). The X-ray CT apparatus 1 irradiates X-rays using an X-ray tube voltage value and an X-ray filter 53 selected according to the control parameters (S214). The X-ray CT apparatus 1 collects data (X-ray detector data) detected by the two-dimensional X-ray detector 7 (S215). The X-ray CT apparatus 1 performs the processes from S213 to S215 similar to S113 to S115 in the first embodiment.

[0080] According to this embodiment, the X-ray CT device 1 refers to an X-ray imaging condition table 241 (lookup table) pre-stored in a specified memory area to determine (derive) X-ray imaging conditions including the X-ray tube voltage value (low tube voltage value and high tube voltage value) and filter characteristics (filter type and filter thickness), which are determining factors for irradiating X-rays of suitable X-ray radiation quality, and therefore, can efficiently determine the X-ray imaging conditions.

[0081] In the present embodiment, the X-ray CT device 1 determines the X-ray imaging conditions by using the X-ray imaging condition table 241 based on the acquired inspection object information and X-ray characteristic information, but is not limited thereto. The X-ray CT device 1 may determine the X-ray imaging conditions using a judgment algorithm included in a program pre-stored in a predetermined storage area such as the storage device 24 based on the acquired inspection object information and X-ray characteristic information. The program including the judgment algorithm is configured to output imaging conditions that provide a sufficient SNR (Signal to Noise Ratio) for the inspection object using the inspection object information and X-ray characteristic information as input factors. Alternatively, the X-ray CT device 1 may determine the X-ray imaging conditions using a learning model pre-stored in a predetermined storage area such as the storage device 24 based on the acquired inspection object information and X-ray characteristic information. The learning model is trained to output imaging conditions that provide a sufficient SNR (Signal to Noise Ratio) for the inspection object by inputting the inspection object information and X-ray characteristic information. The learning model may be, for example, a neural network (NN) such as CNN (Convolutional Neural Network) or RCNN (Regions with Convolutional Neural Network) that handles image data of the object to be inspected output from the imaging unit 10 as object information as input data, or may be a learning model constructed using other learning algorithms, such as an SVM (Support Vector Machine), a Bayesian network, or a regression tree, without being limited to a NN.

[0082] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The technical features described in each embodiment can be combined with each other, and the scope of the present invention is intended to include all modifications within the scope of the claims and the scope equivalent to the claims. [Explanation of symbols]

[0083] RX ray inspection room H Inspection item 1 X-ray CT device 2 Operation Console 21 Input Devices 22 Data Collection Buffer 23 Monitor 24 Storage device 241 X-ray condition table 3. Central Processing Unit 31 Acquisition Department 32 X-ray photography condition determination unit 321 Simulation Execution Department 322 Filter characteristic determination section 323 X-ray tube voltage determination unit 324 Table Reference Section 33 Output section 4. Shooting table 5. X-ray generator 51 X-ray tube 52 Collimator 53 X-ray Filter 531 Bowtie Filter 54 X-ray tube controller 6 Controller 7. Two-dimensional X-ray detector 8 Lifting mechanism 9 Data Collection Equipment 10. Imaging unit

Claims

1. 1. An X-ray CT apparatus comprising: an X-ray generator; and an X-ray detector for detecting X-rays irradiated from the X-ray generator and passing through an object to be inspected, the X-ray CT apparatus collecting X-ray projection data of at least two types of X-ray energy and reconstructing a dual energy image, an acquisition unit that acquires inspection object information including physical quantity and property information of the inspection object, and X-ray spectrum, X-ray filter, and X-ray characteristic information of the X-ray detector; an X-ray imaging condition determination unit that determines each X-ray imaging condition when collecting X-ray projection data of at least two types of X-ray energies irradiated from the X-ray generator based on the inspection object information acquired by the acquisition unit and X-ray characteristic information of an X-ray spectrum, an X-ray filter, and an X-ray detector; An X-ray CT apparatus comprising:

2. The X-ray imaging condition determination unit determines each of the X-ray imaging conditions when collecting X-ray data of at least two types of energy irradiated from the X-ray generator, using a predetermined simulation method or a method of referring to an information table based on the simulation, based on the imaging object information acquired by the acquisition unit.

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

3. the X-ray generating device includes an X-ray filter through which X-rays of at least the two types of X-ray energies pass and X-ray quality is adjusted; The X-ray imaging condition determination unit determines filter characteristics of each of the X-ray filters based on the inspection object information acquired by the acquisition unit and X-ray characteristic information of the X-ray spectrum, the X-ray filter, and the X-ray detector, thereby determining X-ray imaging conditions for each of the two types of X-ray energies.

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

4. The X-ray imaging condition determination unit determines an X-ray tube voltage value, an X-ray tube current value, an imaging time, and an X-ray filter for each of the two types of X-ray energies based on the inspection object information acquired by the acquisition unit and X-ray characteristic information of an X-ray spectrum, an X-ray filter, and an X-ray detector, thereby determining X-ray imaging conditions for each of the two types of X-ray energies.

4. The X-ray CT apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

5. The acquiring unit acquires inspection object information including physical quantity and physical property information of the inspection object based on at least one of an appearance image, a scout image, and drawing information of the inspection object.

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

6. an image reconstruction unit that reconstructs an X-ray dual energy tomographic image based on the 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 projection data of at least two types of X-ray energies, and reconstructs an X-ray dual energy tomographic image including at least one of a plurality of material density tomographic images and a monochromatic tomographic image.

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

7. The X-ray imaging condition determination unit determines each of the X-ray imaging conditions when collecting X-ray data of at least two types of energy irradiated from the X-ray generator, using a lookup table, a judgment algorithm, or a learning model pre-stored in a predetermined storage area, based on the inspection object information acquired by the acquisition unit, and X-ray characteristic information of an X-ray spectrum, an X-ray filter, and an X-ray detector.

7. The X-ray CT apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

8. On the computer, Obtaining inspection object information including physical quantity and property information of an inspection object to be inspected by X-rays of at least two types of X-ray energies irradiated from an X-ray generating device, and X-ray characteristic information of an X-ray spectrum, an X-ray filter, and an X-ray detector; Based on the obtained information on the object to be inspected, respective X-ray imaging conditions for collecting X-ray projection data of at least two types of X-ray energy irradiated from the X-ray generating device are determined. A program that executes a process.

9. Obtaining inspection object information including physical quantity and property information of an inspection object to be inspected by X-rays of at least two types of X-ray energies irradiated from an X-ray generating device, and X-ray characteristic information of an X-ray spectrum, an X-ray filter, and an X-ray detector; Based on the obtained information on the object to be inspected, respective X-ray imaging conditions for collecting X-ray projection data of at least two types of X-ray energy irradiated from the X-ray generating device are determined. An information processing method for causing a computer to execute processing.

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