Ct method, system, device, and medium based on two-direction refraction angle signals

Abstract

This application discloses a CT method, system, device, and medium based on two-directional refraction angle signals. It utilizes a differential-phase CT optical path structure with a source grating, a beam splitter grating, and an analysis grating tilted towards the sample rotation axis. The angle between the direction of the refraction angle signal acquisition and the x-axis is adjusted to ω. When the sample rotation angle is ω, a first refraction angle signal is acquired; when the sample rotation angle is ω, a second refraction angle signal is acquired. Based on the first and second refraction angle signals, the refraction angle signals in the x-axis and y-axis directions of the measurement coordinate system are calculated. During the process of rotating the sample relative to the measurement coordinate system and acquiring the refraction angle signals required for CT reconstruction, it is not necessary to change the direction of the refraction angle signal acquisition, thus achieving the acquisition of two-directional refraction angle signals and reconstructing a refractive index image and a refractive index gradient image without stripe artifacts.

Description

Technical Field

[0001] This invention generally relates to the field of optical imaging technology, and specifically to a CT method, system, device and medium based on two-directional refraction angle signals. Background Technology

[0002] Figure 1 The existing differential phase CT imaging optical path includes an X-ray source 11, a source grating 12, a sample 13, a beam splitter grating 14, an analysis grating 15, and a detector 16. The source grating 12, beam splitter grating 14, and analysis grating 15 are parallel to the rotation axis of the sample 13, and can only acquire refraction angle signals perpendicular to the sample rotation axis. The analytical algorithm for reconstructing the refractive index using the refraction angle signals perpendicular to the sample rotation axis is as follows:

[0003]

[0004] Where δ represents the decrease in the real part of the refractive index. The refraction angle signal is perpendicular to the sample rotation axis, and Φ is the phase shift. Let ρ be the Dirac function, and ρ be the spatial frequency along the x-axis. and Let (x′, y′, z′) represent the inverse Fourier transform and inverse Fourier transform along the x-axis, and (x′, y′, z′) and (x, y, z) represent the sample coordinate system and the measurement coordinate system, respectively. The relationship between the two coordinate systems is as follows:

[0005]

[0006] in The angle between the two coordinate systems is denoted as .

[0007] Current differential phase CT imaging optical paths can only acquire the refraction angle signal perpendicular to the sample rotation axis. However, a complete refraction angle signal includes not only the refraction angle signal perpendicular to the sample rotation axis but also the refraction angle signal parallel to the sample rotation axis. In other words, the complete refraction angle is a two-dimensional vector determined by the refraction angle signals in both directions. Using only the refraction angle signal perpendicular to the sample rotation axis will not only produce stripe artifacts perpendicular to the sample rotation axis in the reconstructed sagittal and coronal images of the refractive index but also will fail to reconstruct the refractive index gradient. Figure 2 , Figure 3 and Figure 4 The images shown are the refractive index coronal, sagittal, and tomographic images reconstructed using the refraction angle signal perpendicular to the sample rotation axis, respectively. It is evident that stripe artifacts perpendicular to the sample rotation axis appear in the coronal and sagittal images. The reason for these stripe artifacts is the lack of a refraction angle signal parallel to the sample rotation axis during reconstruction. Summary of the Invention

[0008] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a CT method, system, device and medium based on two-direction refraction angle signals.

[0009] In a first aspect, the present invention provides a differential phase CT method based on two-direction refraction angle signals, comprising:

[0010] Based on a differential phase CT optical path structure with the source grating, beam splitter grating, and analysis grating tilted towards the sample rotation axis, the angle between the direction of the acquired refraction angle signal and the x-axis is adjusted to ω. At a sample rotation angle of... At that time, the first refraction angle signal was acquired when the sample rotation angle was... At that time, the second refraction angle signal was collected;

[0011] Calculate the refraction angle signals in the x-axis and y-axis directions of the measurement coordinate system based on the first and second refraction angle signals:

[0012]

[0013]

[0014] Where ω is the angle between the direction of the acquired refraction angle signal and the x-axis, 0° < ω < 90°, and Φ is the phase shift. The sample rotation angle is The first refraction angle signal collected at that time, The sample rotation angle is The second refraction angle signal was collected at that time.

[0015] Secondly, the present invention provides a CT system based on two-directional refraction angle signals, characterized in that it includes:

[0016] The differential phase CT optical path structure includes a source grating, a beam splitter grating, and an analysis grating, wherein the source grating, the beam splitter grating, and the analysis grating are tilted relative to the sample rotation axis;

[0017] The differential phase CT optical path structure adjusts the angle between the direction of the acquired refraction angle signal and the x-axis to ω, when the sample rotation angle is... At that time, the first refraction angle signal was acquired when the sample rotation angle was... At that time, the second refraction angle signal was collected;

[0018] Processing apparatus, the processing apparatus comprising:

[0019] The acquisition module is used to acquire the first refraction angle signal and the second refraction angle signal;

[0020] The processing module is used to calculate the refraction angle signals in the x-axis and y-axis directions of the measurement coordinate system based on the first refraction angle signal and the second refraction angle signal.

[0021]

[0022]

[0023] Where ω is the angle between the direction of the acquired refraction angle signal and the x-axis, 0° < ω < 90°, and Φ is the phase shift. The sample rotation angle is The first refraction angle signal collected at that time, The sample rotation angle is The second refraction angle signal was collected at that time.

[0024] Thirdly, the present invention also provides an electronic device comprising a processor and a memory, wherein the memory stores at least one instruction, at least one program, a code set, or an instruction set, wherein the instruction, the program, the code set, or the instruction set is loaded and executed by the processor to implement the steps of the differential phase CT method based on two-direction refraction angle signals described in the first aspect.

[0025] Fourthly, the present invention also provides a computer-readable storage medium storing one or more programs that can be executed by one or more processors to implement the steps of the differential phase CT method based on two-direction refraction angle signals described in the first aspect.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] In the existing differential phase CT optical path structure, this invention adjusts the angle between the grating strip and the sample rotation axis from 0° to ω, that is, adjusts the angle between the direction of the acquired refraction angle signal and the x-axis from 0° to ω, where 0° < ω < 90°. This is achieved when the sample rotation angle is... At that time, the first refraction angle signal was acquired when the sample rotation angle was... At the same time, the second refraction angle signal is acquired; based on the first and second refraction angle signals, the refraction angle signals in the x-axis and y-axis directions in the measurement coordinate system are calculated. During the process of rotating the sample relative to the measurement coordinate system and acquiring the refraction angle signals required for CT reconstruction, there is no need to change the acquisition direction of the refraction angle signal, so as to acquire the refraction angle signals in two directions and reconstruct the refractive index image and refractive index gradient image without strip artifacts. Attached Figure Description

[0028] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0029] Figure 1 A schematic diagram of the structure of a conventional differential phase CT imaging optical path according to an embodiment of this application is shown;

[0030] Figures 2 to 4 The images shown are sagittal, coronal, and tomographic images reconstructed using the refraction angle signal perpendicular to the sample rotation axis.

[0031] Figure 5 A flowchart of the differential phase CT method based on two-direction refraction angle signals according to an embodiment of this application is shown;

[0032] Figure 6 A schematic diagram of the differential phase CT optical path structure according to an embodiment of this application is shown;

[0033] Figures 7 to 8 A schematic diagram of a simplified method for acquiring refraction angle signals in two directions, as described in an embodiment of this application, is shown.

[0034] Figures 9 to 11 The embodiments of this application illustrate sagittal, coronal, and tomographic images reconstructed using two-directional refraction angle signals.

[0035] Figure 12 This illustration shows a schematic diagram of a two-dimensional vector function for pure color description related to an embodiment of this application;

[0036] Figure 13 An image of three-dimensional reconstruction of the refractive index gradient according to an embodiment of this application is shown;

[0037] Figure 14 This application illustrates one-dimensional projected gradient images of the refractive index gradient on a sample cross-section, as shown in the embodiments of this application.

[0038] Figure 15 This illustrates another one-dimensional projection gradient image of the refractive index gradient on a sample section, as described in an embodiment of this application.

[0039] Figures 16 to 18 The illustration shows two-dimensional projected gradient images of the refractive index gradient in the coronal, sagittal, and transverse planes, according to embodiments of this application.

[0040] Figure 19 A structural block diagram of the processing apparatus according to an embodiment of this application is shown;

[0041] Figure 20 A schematic diagram of the structure of a computer device according to an embodiment of this application is shown. Detailed Implementation

[0042] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0043] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0044] Please refer to Figure 5 , Figure 5 A flowchart of the differential phase CT method based on two-direction refraction angle signals provided in this application is shown.

[0045] Step 51, the differential phase CT optical path structure based on the source grating, beam splitter grating, and analysis grating tilted to the sample rotation axis is as follows: Figure 6 As shown, the angle between the direction of the collected refraction angle signal and the x-axis is adjusted to ω, and the sample rotation angle is... At that time, the first refraction angle signal was acquired when the sample rotation angle was... At that time, the second refraction angle signal was collected;

[0046] Step 52: Calculate the refraction angle signals in the x-axis and y-axis directions of the measurement coordinate system based on the first and second refraction angle signals.

[0047]

[0048]

[0049] Where ω is the angle between the direction of the acquired refraction angle signal and the x-axis, 0° < ω < 90°, and Φ is the phase shift. The sample rotation angle is The first refraction angle signal acquired at that time, such as Figure 7 As shown; The sample rotation angle is The second refraction angle signal collected at that time, such as Figure 8 As shown.

[0050] The method also includes an analytical algorithm for accurately reconstructing the refractive index based on formula (5) and the refraction angle signals in the x-axis and y-axis directions of the measurement coordinate system:

[0051]

[0052] Substituting equations (3) and (4) into equation (5), we obtain an analytical algorithm for accurately reconstructing the refractive index by acquiring refractive angle signals from two directions without changing the direction of the refractive angle signal acquisition:

[0053]

[0054] Where δ(x′,y′,z′) is the decrease in the real part of the refractive index. and These are the Fourier transform and inverse Fourier transform along the x-axis, respectively. and They are the Fourier transform and inverse Fourier transform along the y-axis respectively. ρ is the spatial frequency of the x-axis, ν is the spatial frequency along the y-axis, and a and b are two adjustment factors, where 0 < a ≤ 1 and 0 ≤ b ≤ 1, which respectively adjust the weights of the refraction angle signals in the x-axis direction and the y-axis direction.

[0055] In Equation (6), there are two mechanisms for adjusting the weights of the refraction angle signals in the x-axis direction and the y-axis direction. One is software adjustment based on the two adjustment factors a and b, and the other is hardware adjustment based on the grating rotation angle ω.

[0056] Figures 9 to 11 It is the refractive index image reconstructed according to Equation (6). In Figure 9 and Figure 10 There are no strip artifacts in the coronal image and sagittal image.

[0057] The analytical algorithm for reconstructing the refractive index gradient using the refraction angle signals in the x-axis and y-axis directions in the measurement coordinate system is:

[0058]

[0059] Substituting Equation (3) and Equation (4) into Equation (7), the analytical algorithm for reconstructing the refractive index gradient that can collect the refraction angle signals in two directions without changing the collection direction of the refraction angle signals is:

[0060] <​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0067]

[0068] The method also includes: constructing a refractive index gradient Analytical algorithm for two-dimensional projection gradient of any selected profile;

[0069] set up If the refractive index gradient is parallel to the normal vector of the selected profile, then... The two-dimensional projection gradient of the selected profile is:

[0070]

[0071] in,

[0072]

[0073]

[0074] When the direction of the two-dimensional projection gradient is:

[0075]

[0076] The normalized two-dimensional projection gradient value is:

[0077]

[0078] Two-dimensional vectors can be described using pure colors. A pure color has a saturation of 1. Different colors distinguish vector directions. In each color direction, a normalized pure color value represents the relative magnitude of the vector, ranging from 0 to 1. For example, red, yellow, green, cyan, blue, and magenta represent 0°, 60°, 120°, 180°, 240°, and 300° directions, respectively. The normalized color value in each direction represents the relative magnitude of the vector. See [link to relevant documentation]. Figure 12 .

[0079] Figures 13 to 18 To be based on the refractive index gradient The reconstructed image. Figure 13 for Three-dimensional reconstruction; Figure 14 and Figure 15 They are respectively Two one-dimensional projection gradient images of the sample cross-section, the former parallel to the mouse hair and the latter perpendicular to the mouse hair; Figure 16 , Figure 17 , Figure 18 They are respectively Two-dimensional projection gradient images in the coronal, sagittal, and sectional planes. From The reconstructed image of the projection gradient shows that, parallel to... The reconstructed image has the highest contrast in the direction of the projection gradient, perpendicular to the direction of the projection gradient. The projection gradient direction results in the lowest reconstructed image contrast. For example, Figure 15 The image is a one-dimensional projection gradient image perpendicular to the mouse hair; the mouse hair is very clear, while... Figure 14 In the image, the one-dimensional projection gradient is parallel to the mouse hair, and the mouse hair is almost invisible.

[0080] Please refer to Figure 19 , Figure 19 A structural block diagram of a CT system based on two-directional refraction angle signals provided in an embodiment of this application is shown.

[0081] The system includes:

[0082] The differential phase CT optical path structure includes an X-ray source 61, a source grating 62, a beam splitter grating 64, an analysis grating 65, and a detector 66. The source grating 62, the beam splitter grating 64, and the analysis grating 65 are tilted to the rotation axis of the sample 63.

[0083] The differential phase CT optical path structure adjusts the angle between the direction of the acquired refraction angle signal and the x-axis to ω, when the sample rotation angle is... At that time, the first refraction angle signal was acquired when the sample rotation angle was... At that time, the second refraction angle signal was collected;

[0084] Processing apparatus 200, the processing apparatus comprising:

[0085] Acquisition module 201 is used to acquire the first refraction angle signal and the second refraction angle signal;

[0086] Processing module 202 is used to calculate the refraction angle signals in the x-axis and y-axis directions of the measurement coordinate system based on the first refraction angle signal and the second refraction angle signal.

[0087]

[0088]

[0089] Where ω is the angle between the direction of the acquired refraction angle signal and the x-axis, 0° < ω < 90°, and Φ is the phase shift. The sample rotation angle is The first refraction angle signal collected at that time, The sample rotation angle is The second refraction angle signal was collected at that time.

[0090] Optionally, the processing device further includes a first processing module for an analytical algorithm to accurately reconstruct the refractive index based on formula (5) and the refraction angle signals in the x-axis and y-axis directions of the measurement coordinate system:

[0091]

[0092] Substituting Equation (3) and Equation (4) into Equation (5), an analytical algorithm for accurately reconstructing the refractive index can be obtained, where the acquisition direction of the refraction angle signal does not need to be changed to acquire the refraction angle signals in two directions:

[0093]

[0094] where δ is the reduction in the real part of the refractive index, and are the Fourier transform and inverse Fourier transform along the x-axis respectively, and are the Fourier transform and inverse Fourier transform along the y-axis respectively, ρ is the spatial frequency along the x-axis, ν is the spatial frequency along the y-axis, a and b are two control factors, 0 < a ≤ 1, 0 ≤ b ≤ 1, which respectively control the weights of the refraction angle signals in the x-axis direction and the y-axis direction.

[0095] Optionally, the processing device further includes a second processing module for using an analytical algorithm to reconstruct the refractive index gradient from the refraction angle signals in the x-axis and y-axis directions in the measurement coordinate system:

[0096] [[ID=2...]]

[0097] Substituting Equation (3) and Equation (4) into Equation (7), the analytical algorithm for reconstructing the refractive index gradient can be obtained as:

[0098]

[0099] where, is the refractive index gradient, are the unit vectors of the x′-axis, y′-axis, and z′-axis in the sample coordinate system respectively, [[ID=3...]] are the unit vectors of the x-axis and y-axis in the measurement coordinate system respectively.

[0100] Optionally, the second processing module is further configured to construct an analytical algorithm for the one-dimensional projection gradient of the refractive index gradient in an arbitrarily selected direction;

[0101] Let the unit vector in the selected direction be In the sample coordinate system, its expression is:

[0102]

[0103] where γ is the latitude, 0 ≤ γ < π, ψ is the longitude, 0 ≤ ψ < 2π, then the one-dimensional projection gradient of the refractive index gradient in the selected direction is:

[0104] ​

[0105] Optionally, the second processing module is also used to construct the refractive index gradient. Analytical algorithm for two-dimensional projection gradient of any selected profile;

[0106] set up If the refractive index gradient is parallel to the normal vector of the selected profile, then... The two-dimensional projection gradient of the selected profile is:

[0107]

[0108] in,

[0109]

[0110]

[0111] Optionally, when the two-dimensional projection gradient direction is:

[0112]

[0113] The normalized two-dimensional projection gradient value is:

[0114]

[0115] The CT system based on two-direction refraction angle signals proposed in this application can acquire two-direction refraction angle signals without changing the acquisition direction of the refraction angle signals during the process of rotating the sample relative to the measurement coordinate system and acquiring the refraction angle signals required for CT reconstruction. It can reconstruct a refractive index image and a refractive index gradient image without strip artifacts, and can display the one-dimensional projection gradient of the refractive index gradient in any selected direction and the two-dimensional projection gradient in any selected section.

[0116] On the other hand, this application also provides a computer-readable storage medium, which may be included in the server described in the following embodiments; or it may exist independently and not assembled into the server. Electronic devices such as Figure 20 As shown, the server includes a central processing unit (CPU) 2101, which can perform various appropriate actions and processes based on programs stored in read-only memory (ROM) 2102 or programs loaded from storage into random access memory (RAM) 2104. RAM 2103 also stores various programs and data required for system operation. The CPU 2101, ROM 2102, and RAM 2103 are interconnected via bus 2104. Input / output (I / O) interface 2105 is also connected to bus 2105.

[0117] The following components are connected to I / O interface 2105: an input section 2106 including a keyboard, mouse, etc.; an output section 2107 including a cathode ray tube (CRT), liquid crystal display (LCD), etc., and speakers, etc.; a storage section 2108 including a hard disk, etc.; and a communication section 2109 including a network interface card such as a LAN card, modem, etc. The communication section 2109 performs communication processing via a network such as the Internet. A drive is also connected to I / O interface 2105 as needed. Removable media 2111, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., are installed on drive 2110 as needed so that computer programs read from them can be installed into storage section 2108 as needed.

[0118] In particular, according to embodiments of the present invention, the above-described reference process Figure 1 The described process can be implemented as a computer software program. For example, embodiments of the present invention include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowchart. In such embodiments, the computer program can be downloaded and installed from a network via a communication component, and / or installed from a removable medium. When the computer program is executed by a central processing unit (CPU) 2101, it performs the functions defined in the system of this application.

[0119] It should be noted that the computer-readable medium shown in this invention can be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this invention, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. In this invention, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. Computer-readable signal media can also be any computer-readable medium other than computer-readable storage media, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wireless, wire, optical fiber, RF, etc., or any suitable combination thereof.

[0120] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0121] The units described in the embodiments of the present invention can be implemented in software or hardware, and can also be located in a processor. The names of these units do not necessarily limit the specific unit itself. The described units or modules can also be located in a processor or a control processor. For example, a control processor can be described as including an acquisition module and a processing module. Again, the names of these units or modules do not necessarily limit the specific unit or module itself. For example, an acquisition module can be described as "a module for acquiring a first refraction angle signal and a second refraction angle signal".

[0122] The aforementioned computer-readable medium carries one or more programs that, when executed by a server, cause the server to implement the CT method based on bidirectional refraction angle signals as described in the above embodiments. The server may also be other electronic devices.

[0123] For example, the server can achieve the following: Figure 2 As shown: Step 10, based on the differential phase CT optical path structure where the source grating, beam splitter grating, and analysis grating are tilted towards the sample rotation axis, the angle between the direction of the acquired refraction angle signal and the x-axis is adjusted to ω, at a sample rotation angle of... At that time, the first refraction angle signal was acquired when the sample rotation angle was... At that time, the second refraction angle signal is acquired; in step 20, the refraction angle signals in the x-axis and y-axis directions in the measurement coordinate system are calculated based on the first and second refraction angle signals:

[0124]

[0125]

[0126] It should be noted that although several modules or units for the device used to perform actions have been mentioned in the detailed description above, this division is not mandatory. In fact, according to embodiments of this disclosure, the features and functions of two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided and embodied by multiple modules or units.

[0127] Furthermore, although the steps of the method in this disclosure are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or a step may be broken down into multiple steps.

[0128] Through the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein can be implemented by software or by combining software with necessary hardware.

[0129] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of disclosure in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the foregoing disclosed concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A differential phase CT method based on two-direction refraction angle signals, characterized in that, include: Based on a differential phase CT optical path structure with the source grating, beam splitter grating, and analysis grating tilted towards the sample rotation axis, the angle between the direction of the acquired refraction angle signal and the x-axis is adjusted to ω. At a sample rotation angle of... At that time, the first refraction angle signal was acquired when the sample rotation angle was... At that time, the second refraction angle signal was collected; Calculate the refraction angle signals in the x-axis and y-axis directions of the measurement coordinate system based on the first and second refraction angle signals. Where ω is the angle between the direction of the acquired refraction angle signal and the x-axis, 0° < ω < 90°, and Φ is the phase shift. The sample rotation angle is The first refraction angle signal collected at that time, The sample rotation angle is The second refraction angle signal was collected at that time; It also includes an analytical algorithm for accurately reconstructing the refractive index based on formula (5) and the refraction angle signals in the x-axis and y-axis directions of the measurement coordinate system: (5)； Substituting equations (3) and (4) into equation (5), we obtain an analytical algorithm for accurately reconstructing the refractive index by acquiring refractive angle signals from two directions without changing the direction of the refractive angle signal acquisition: (6)； Where δ(x′,y′,z′) is the decrease in the real part of the refractive index. and These are the Fourier transform and inverse Fourier transform along the x-axis, respectively. and These are the Fourier transform and inverse Fourier transform along the y-axis, respectively; ρ is the spatial frequency along the x-axis; v is the spatial frequency along the y-axis; a and b are two control factors; 0 , The weights of the x-axis refraction angle signal and the y-axis refraction angle signal are adjusted respectively.

2. The differential phase CT method based on two-direction refraction angle signals according to claim 1, characterized in that, The analytical algorithm for reconstructing the refractive index gradient using the refraction angle signals along the x and y axes of the measurement coordinate system is as follows: (7)； Substituting equations (3) and (4) into equation (7), we obtain the analytical algorithm for reconstructing the refractive index gradient by acquiring refractive angle signals in two directions without changing the direction of the refractive angle signal acquisition: (8)； in, For the refractive index gradient, These are the unit vectors of the x′, y′, and z′ axes in the sample coordinate system, respectively. and These are the unit vectors for the x-axis and y-axis in the measurement coordinate system, respectively.

3. The differential phase CT method based on two-direction refraction angle signals according to claim 2, characterized in that, Also includes: Constructing the refractive index gradient An analytical algorithm for one-dimensional projection gradient in any chosen direction; Let the unit vector in the selected direction be... In the sample coordinate system, it is expressed as: Where γ is latitude, 0 ≤ γ < π, and ψ is longitude, 0 ≤ ψ < 2π, then the refractive index gradient The one-dimensional projection gradient in the selected direction is:

4. The differential phase CT method based on two-direction refraction angle signals according to claim 2, characterized in that, Also includes: Constructing the refractive index gradient Analytical algorithm for two-dimensional projection gradient of any selected profile; set up If the refractive index gradient is parallel to the normal vector of the selected profile, then... The two-dimensional projection gradient of the selected profile is: (11)； in, (12)； 5. The differential phase CT method based on two-direction refraction angle signals according to claim 4, characterized in that, When the direction of the two-dimensional projection gradient is: The normalized two-dimensional projection gradient value is:

6. A CT system based on two-directional refraction angle signals, characterized in that, include: The differential phase CT optical path structure includes a source grating, a beam splitter grating, and an analysis grating, wherein the source grating, the beam splitter grating, and the analysis grating are tilted relative to the sample rotation axis; The differential phase CT optical path structure adjusts the angle between the direction of the acquired refraction angle signal and the x-axis to ω, when the sample rotation angle is... At that time, the first refraction angle signal was acquired when the sample rotation angle was... At that time, the second refraction angle signal was collected; Processing apparatus, the processing apparatus comprising: The acquisition module is used to acquire the first refraction angle signal and the second refraction angle signal; The processing module is used to calculate the refraction angle signals in the x-axis and y-axis directions of the measurement coordinate system based on the first refraction angle signal and the second refraction angle signal. Where ω is the angle between the direction of the acquired refraction angle signal and the x-axis, 0° < ω < 90°, and Φ is the phase shift. The sample rotation angle is The first refraction angle signal collected at that time, The sample rotation angle is The second refraction angle signal was collected at that time; It also includes an analytical algorithm for accurately reconstructing the refractive index based on formula (5) and the refraction angle signals in the x-axis and y-axis directions of the measurement coordinate system: (5)； Substituting equations (3) and (4) into equation (5), we obtain an analytical algorithm for accurately reconstructing the refractive index by acquiring refractive angle signals from two directions without changing the direction of the refractive angle signal acquisition: (6)； Where δ(x′,y′,z′) is the decrease in the real part of the refractive index. and These are the Fourier transform and inverse Fourier transform along the x-axis, respectively. and These are the Fourier transform and inverse Fourier transform along the y-axis, respectively; ρ is the spatial frequency along the x-axis; v is the spatial frequency along the y-axis; a and b are two control factors; 0 , The weights of the x-axis refraction angle signal and the y-axis refraction angle signal are adjusted respectively.

7. An electronic device, characterized in that, The electronic device includes a processor and a memory, wherein the memory stores at least one instruction, at least one program, code set, or instruction set, and the instruction, program, code set, or instruction set is loaded and executed by the processor to implement the steps of the differential phase CT method based on two-direction refraction angle signals as described in any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores one or more programs, which can be executed by one or more processors to implement the steps of the differential phase CT method based on two-direction refraction angle signals as described in any one of claims 1 to 5.

Images