Multiphase flow quasi-dynamic phantom for ct device testing and ct device testing method

Abstract

A kind of multiphase flow quasi-dynamic phantom for CT equipment test and CT equipment test method, multiphase flow quasi-dynamic phantom includes shell, guide pipe, multiphase flow field column;Guide pipe is located in shell, multiphase flow field column is solid structure, at least one bubble is distributed in, multiphase flow field column is detachably arranged in guide pipe, and can move along the axial direction of guide pipe.Multiphase flow quasi-dynamic phantom simulates the movement of multiphase flow field column in guide pipe, can simulate most of the motion characteristics in real multiphase flow flow field, to realize the test of CT equipment for multiphase flow measurement.CT equipment test method utilizes multiphase flow quasi-dynamic phantom, can obtain the true value data and dynamic measurement data of multiphase flow flow field using existing measurement method, to realize the test of CT equipment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of multiphase flow, and particularly relates to a quasi-dynamic multiphase flow phantom for CT device testing and a CT device testing method. BACKGROUND

[0002] Multiphase flow is extremely complex, and the key technical problem in discovering and extracting scientific principles from physical phenomena is the measurement of multiphase flow. Current multiphase flow measurement methods include high-speed photographic imaging, radiographic imaging, ultrasonic imaging, optical fiber probes, etc., which can quickly obtain measurement parameters of the flow field flow. With the development of technology, the time resolution and spatial resolution of flow field measurement technology have rapidly improved, and one important technical route is to use high-speed X-ray CT (Computed Tomography) devices to perform three-dimensional measurement of multiphase flow fields. In order to objectively evaluate the measurement accuracy of the CT device, the usual practice is to select a suitable test object, compare the measurement data of the test object by the CT device with the known true value data, and evaluate the measurement performance of the CT device.

[0003] In high temporal and spatial resolution measurement of multiphase flow fields, the physical properties of the multiphase flow field determine that two completely identical flow fields cannot be obtained. If an actual multiphase flow field is used as a test object, the corresponding true value data cannot be obtained, which leads to the inability to reasonably evaluate the performance of the CT device in actual multiphase flow measurement. In addition, motion artifacts will be generated when the CT device measures a similar multiphase flow field motion system, which damages the temporal and spatial resolution of the device. Therefore, it is desirable to develop a technology that can simulate the dynamic effects of multiphase flow fields and obtain true value data using existing measurement methods to achieve testing of the CT device. SUMMARY

[0004] The present application provides a quasi-dynamic multiphase flow phantom for CT device testing, comprising a shell, a guide pipe, and a multiphase flow field column.

[0005] The guide pipe is arranged in the shell, the multiphase flow field column is of a solid structure and has at least one bubble distributed therein, and the multiphase flow field column is detachably arranged in the guide pipe and can move along the axial direction of the guide pipe.

[0006] Preferably, the shell, the multiphase flow field column, and the guide pipe are all made of a polymer material that allows X-ray penetration; and / or

[0007] The multiphase flow field column is cylindrical, and the guide pipe is a circular pipe, the inner diameter of the guide pipe being adapted to the outer diameter of the multiphase flow field column.

[0008] Preferably, the axial direction of the guide tube is arranged vertically or forms an angle with the vertical direction, and the angle is less than or equal to 15°; and / or

[0009] The multiphase flow quasi-dynamic phantom further comprises a driving mechanism, and the multiphase flow field column is connected with the driving mechanism and can move in the axial direction of the guide tube under the action of the driving mechanism.

[0010] Preferably, one guide tube and one multiphase flow field column form a phantom unit, and the multiphase flow quasi-dynamic phantom comprises a plurality of phantom units, and the plurality of phantom units are substantially uniformly distributed in the shell.

[0011] The embodiment of the present application further provides a CT device testing method, which utilizes the multiphase flow quasi-dynamic phantom, and comprises the following steps:

[0012] Step 1: using a reference CT device to scan the multiphase flow field column, the guide tube and the shell, to obtain first static three-dimensional structure data of the multiphase flow field column and second static three-dimensional structure data of the guide tube and the shell;

[0013] Step 2: making the multiphase flow field column move at an accelerated or decelerated speed in the guide tube, and simultaneously using a CT device to be tested to scan the multiphase flow quasi-dynamic phantom, to obtain dynamic measurement data of the multiphase flow quasi-dynamic phantom at a plurality of different speeds;

[0014] Step 3: calculating true value data at each speed respectively according to the first static three-dimensional structure data and the second static three-dimensional structure data, and calculating a structure similarity index corresponding to each speed based on the true value data and the dynamic measurement data.

[0015] Preferably, the step 1 comprises:

[0016] using a reference CT device to scan the multiphase flow field column to obtain voxel format data of the multiphase flow field column in a static state, and using a reference CT device to scan the guide tube and the shell to obtain voxel format data of the guide tube and the shell, wherein each voxel stores a floating point number, and the floating point number represents a density measurement value corresponding to the voxel;

[0017] performing binaryzation processing on the voxel format data of the multiphase flow field column to obtain first static three-dimensional structure data of the multiphase flow field column, and performing binaryzation processing on the voxel format data of the guide tube and the shell to obtain second static three-dimensional structure data of the guide tube and the shell.

[0018] Preferably, the step 2 comprises:

[0019] putting the multiphase flow column into the guide pipe to make the multiphase flow column accelerate or decelerate in the guide pipe, and using the CT device to be tested to scan the multiphase flow dynamic phantom for multiple rounds to obtain original dynamic measurement data;

[0020] extracting data of multiple target rounds from the original dynamic measurement data, wherein each target round corresponds to a different speed of the multiphase flow column, and performing CT reconstruction and binarization processing on the extracted data to obtain dynamic measurement data of the multiphase flow dynamic phantom at multiple different speeds.

[0021] Preferably, the true value data is calculated according to the first static three-dimensional structure data and the second static three-dimensional structure data by the following steps:

[0022] selecting a time T in the target round as a time for calculating the structural similarity index;

[0023] determining a relative position relationship between the multiphase flow column, the guide pipe and the shell at the time T according to the original dynamic measurement data;

[0024] splicing the first static three-dimensional structure data and the second static three-dimensional structure data according to the relative position relationship to obtain the true value data at the speed corresponding to the target round.

[0025] Preferably, the calculation formula of the structural similarity index SSIM is:

[0026]

[0027] wherein, μ x ,μ y respectively represent the average values of the true value data and the dynamic measurement data; σ x ,σ y ,σ xy respectively represent the standard deviations of the true value data and the dynamic measurement data and the covariance of the two; C1 and C2 are constants.

[0028] Preferably, the CT device testing method further comprises:

[0029] determining the maximum reliable testing speed of the CT device to be tested according to the threshold of the structural similarity index.

[0030] The embodiment of the application further provides a CT device testing method using the multiphase flow dynamic phantom, comprising:

[0031] Step 1: using a reference CT device to scan the multiphase flow field column, the guide pipe and the shell, obtaining first static three-dimensional structure data of the multiphase flow field column and second static three-dimensional structure data of the guide pipe and the shell;

[0032] Step 2: moving the multiphase flow field column in the guide pipe at a predetermined speed, and using a CT device to be tested to scan the multiphase flow field column, obtaining dynamic measurement data of the multiphase flow field column at the predetermined speed;

[0033] Step 3: calculating true value data at the predetermined speed according to the first static three-dimensional structure data and the second static three-dimensional structure data, and calculating a structure similarity index at the predetermined speed based on the true value data and the dynamic measurement data;

[0034] Step 4: repeating steps 2 and 3, moving the multiphase flow field column in the guide pipe at different predetermined speeds, and obtaining a structure similarity index corresponding to each predetermined speed.

[0035] The present application has the following beneficial effects:

[0036] 1. The multiphase flow field column simulates the movement of the multiphase flow field in the guide pipe, can simulate most of the movement characteristics in the real multiphase flow field, and thus realizes the testing of the CT device for measuring the multiphase flow.

[0037] 2. The CT device testing method uses the multiphase flow field column, can obtain true value data and dynamic measurement data of the multiphase flow field by using existing measurement methods, and thus realizes the testing of the CT device.

[0038] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0039] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout the different views of the drawings.

[0040] Figure 1 A structural schematic diagram of a multiphase flow field column for CT device testing according to an exemplary embodiment of the present application is shown.

[0041] Figure 2 A structural schematic diagram of a multiphase flow field column for CT device testing according to an exemplary embodiment of the present application is shown.

[0042] Figure 3A structural schematic diagram of a shell of a multiphase flow dynamic phantom for CT device testing according to an exemplary embodiment of the present application is shown.

[0043] Figure 4 A structural schematic diagram of a multiphase flow dynamic phantom for CT device testing according to an exemplary embodiment of the present application is shown.

[0044] BRIEF DESCRIPTION OF DRAWINGS

[0045] 1, drive mechanism; 2, guide tube; 3, shell; 4, multiphase flow column; 5, air bubble. DETAILED DESCRIPTION

[0046] The preferred embodiments of the present application will be described in more detail below. Although the preferred embodiments of the present application are described below, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0047] The exemplary embodiment of the present application provides a multiphase flow dynamic phantom for CT device testing, comprising a shell, a guide tube, a multiphase flow column;

[0048] The guide tube is arranged in the shell, the multiphase flow column is of a solid structure and has at least one air bubble arranged therein, and the multiphase flow column is detachably arranged in the guide tube and can move along the axial direction of the guide tube.

[0049] The multiphase flow dynamic phantom simulates the motion of multiphase flow by the motion of the multiphase flow column in the guide tube, can simulate most of the motion characteristics in the real multiphase flow field, and thus can test the CT device for multiphase flow measurement.

[0050] Further, the shell, the multiphase flow column and the guide tube are all made of a material that allows X-ray penetration, preferably a polymer material that allows X-ray penetration, and more preferably a low-density polymer material that allows X-ray penetration. For example, the shell, the multiphase flow column and the guide tube are all made of transparent acrylic material. According to actual needs, air bubbles are formed inside the multiphase flow column to simulate the actual flow field in terms of shape, size and distribution.

[0051] Further, the multiphase flow column is cylindrical, the guide tube is a circular tube, the inner diameter of the guide tube is adapted to the outer diameter of the multiphase flow column, so that the multiphase flow column can move smoothly along the axial direction of the guide tube without deflection. Generally, the motion speed of fluid in the multiphase flow field is mainly along the vertical direction, with a small component in the horizontal direction, and thus the axial direction of the guide tube is arranged along the vertical direction or forms an angle with the vertical direction, and the angle is preferably less than or equal to 15°.

[0052] Further, the shell is used to simulate the reactor structure where the multiphase flow field is located, to support and fix the guide pipe, and to keep the guide pipe stable. In addition, the shell can be designed as a quick-release structure to facilitate individual measurement of the multiphase flow field column.

[0053] Further, the multiphase flow quasi-dynamic phantom further comprises a driving mechanism, and the multiphase flow field column is connected to the driving mechanism and can move in the guide pipe along the axial direction of the guide pipe under the action of the driving mechanism. The driving mechanism can be used to conveniently control the movement speed of the multiphase flow field column, so as to simulate the movement speed of the different phase state structures in the multiphase flow field. The driving mechanism comprises, for example, a motor and a necessary transmission mechanism, and the transmission mechanism is used to convert the rotation of the motor into the linear motion of the multiphase flow field column.

[0054] Further, one guide pipe and one multiphase flow field column form one phantom unit, and the multiphase flow quasi-dynamic phantom can comprise a plurality of phantom units, and the plurality of phantom units are substantially uniformly distributed in the shell. When the multiphase flow quasi-dynamic phantom comprises a plurality of phantom units, a complex multiphase flow field can be simulated. In this case, if the driving mechanism is used to drive the multiphase flow field columns of the respective phantom units, the same driving mechanism is applied to drive the respective multiphase flow field columns, so as to ensure the relative movement characteristics of the respective multiphase flow field columns.

[0055] The embodiment of the present application also provides a CT device test method, which utilizes the multiphase flow quasi-dynamic phantom, and comprises the following steps:

[0056] Step 1: using a reference CT device to scan the multiphase flow field column, the guide pipe and the shell, to obtain first static three-dimensional structure data of the multiphase flow field column, and second static three-dimensional structure data of the guide pipe and the shell.

[0057] In step 1, the reference CT device refers to a CT device that has been tested or calibrated and meets the measurement requirements. The reference CT device is used to scan the multiphase flow field column alone, so as to obtain voxel format data of the multiphase flow field column in a static state. Each voxel stores a floating-point number, which represents the density measurement value corresponding to the voxel. Since the bubble has a different density from the surrounding solid, the voxel format data can represent the three-dimensional spatial distribution of the bubble in a static state.

[0058] Similarly, the reference CT device is used to scan the guide pipe and the shell as a whole, so as to obtain voxel format data of the guide pipe and the shell in a static state. Similarly, each voxel stores a floating-point number, which represents the density measurement value corresponding to the voxel.

[0059] Preferably, the voxel format data is subjected to binaryzation processing, so as to obtain the first static three-dimensional structure data of the multiphase flow field column and the second static three-dimensional structure data of the guide pipe and the shell. After binaryzation processing, the value 1 in the voxel format data represents a bubble, and the value 0 represents a non-bubble.

[0060] Step 2: make the multiphase flow column accelerate or decelerate in the guide tube, and use the CT device to be tested to scan the multiphase flow quasi-dynamic phantom to obtain dynamic measurement data of the multiphase flow quasi-dynamic phantom at different speeds.

[0061] Specifically, the multiphase flow column is placed in the guide tube, and the multiphase flow column is accelerated or decelerated in the guide tube, and the multiphase flow quasi-dynamic phantom is scanned multiple times using the CT device to be tested to obtain the original dynamic measurement data.

[0062] The data of the target round is extracted from the original dynamic measurement data, wherein each target round corresponds to a different speed of the multiphase flow column. The data of the target round extracted from the original dynamic measurement data includes the radiation dose distribution received by the X-ray detector when the CT device is exposed at different focal points. After processing by the CT reconstruction algorithm, the reconstructed three-dimensional structure data can be obtained. The three-dimensional structure data obtained by reconstruction is a prior art in the field, and will not be described here. Since the multiphase flow column is in motion, the motion state of the multiphase flow column inside is different when exposed at different focal points, which will introduce artifacts in the reconstructed data.

[0063] The original dynamic measurement data is also voxel format data, each voxel stores a floating point number representing the density measurement value corresponding to the voxel. The extracted data of the multiple target rounds is binarized to obtain the dynamic measurement data of the multiphase flow quasi-dynamic phantom at different speeds. Similarly, after binarization, the value 1 in the voxel format data represents a bubble, and the value 0 represents a non-bubble.

[0064] Step 3: calculate the true value data at each speed according to the first static three-dimensional structure data and the second static three-dimensional structure data, and calculate the structural similarity index corresponding to each speed based on the true value data and the dynamic measurement data.

[0065] Specifically, the true value data is calculated according to the first static three-dimensional structure data and the second static three-dimensional structure data according to the following steps:

[0066] Select time T in the target round as the time for calculating the structural similarity index;

[0067] According to the original dynamic measurement data, determine the relative position relationship between the multiphase flow column and the guide tube and the shell at time T;

[0068] According to the relative position relationship, splice the first static three-dimensional structure data and the second static three-dimensional structure data to obtain the true value data at the speed corresponding to the target round.

[0069] Each scanning lasts for a short period (about several milliseconds to tens of milliseconds), and a time point T is selected in the period. According to the original dynamic measurement data, the relative position relationship between the multiphase flow field column and the guide pipe and the shell at the time point T is determined, so as to splice the first static three-dimensional structure data and the second static three-dimensional structure data, and obtain the true value data corresponding to the target round of speed. The method of data splicing is the prior art in the field, and will not be described here.

[0070] Then, the performance of the CT device is evaluated using the structural similarity index SSIM as an evaluation index, and the calculation formula of the SSIM is as follows:

[0071]

[0072] Wherein, μ x ,μ y respectively represent the average values of the true value data and the dynamic measurement data; σ x ,σ y ,σ xy respectively represent the standard deviations of the true value data and the dynamic measurement data and the covariance thereof; V1,C2 are constants. The true value data and the dynamic measurement data are both voxel format data, the average value is the average value of the data corresponding to each voxel in the voxel format data, and the standard deviation is the standard deviation of the data corresponding to each voxel in the voxel format data.

[0073] Further, the CT device testing method further comprises: determining the maximum reliable testing speed of the CT device to be tested according to the threshold of the structural similarity index.

[0074] In step 3, the structural similarity index corresponding to each speed is calculated, the threshold of the structural similarity index is compared with the structural similarity indexes at different speeds, and when the structural similarity index at a certain speed is greater than the threshold of the structural similarity index, it indicates that the CT device to be tested meets the dynamic measurement requirements of the multiphase flow system. Comparing the structural similarity indexes at different speeds with the threshold of the structural similarity index can determine the maximum reliable testing speed of the CT device to be tested, which represents the maximum speed at which the test result is reliable (i.e. meets a certain accuracy).

[0075] In another embodiment, the present application provides a CT device testing method using the multiphase flow quasi-dynamic phantom, comprising:

[0076] Step 1: using a reference CT device to scan the multiphase flow field column, the guide pipe and the shell, to obtain the first static three-dimensional structure data of the multiphase flow field column and the second static three-dimensional structure data of the guide pipe and the shell;

[0077] Step 2: moving the multiphase flow field column in the guide pipe at a predetermined speed, and using the CT device to be tested to scan the multiphase flow quasi-dynamic phantom to obtain dynamic measurement data of the multiphase flow quasi-dynamic phantom at the predetermined speed;

[0078] Step 3: calculating the true value data at the predetermined speed according to the first static three-dimensional structure data and the second static three-dimensional structure data, and calculating the structure similarity index at the predetermined speed based on the true value data and the dynamic measurement data;

[0079] Step 4: repeating steps 2 and 3 to move the multiphase flow field column in the guide pipe at different predetermined speeds to obtain the structure similarity index corresponding to each predetermined speed.

[0080] The difference between this embodiment and the previous embodiment is that in step 2, the multiphase flow field column moves in the guide pipe at a constant predetermined speed. In this case, steps 2 and 3 need to be repeated multiple times to obtain the structure similarity index at different predetermined speeds. The other details of this embodiment are similar to those of the previous embodiment and will not be repeated here.

[0081] Specifically, the motor can be used to drive the multiphase flow field column to move in the guide pipe at a constant predetermined speed.

[0082] Example 1

[0083] Figure 1 A structural diagram of a multiphase flow quasi-dynamic phantom for CT device testing according to an example embodiment of the present application is shown, Figure 2 A structural diagram of a multiphase flow field column of a multiphase flow quasi-dynamic phantom for CT device testing according to an example embodiment of the present application is shown, Figure 3 A structural diagram of a shell of a multiphase flow quasi-dynamic phantom for CT device testing according to an example embodiment of the present application is shown.

[0084] As Figures 1-3 shown, the present embodiment provides a multiphase flow quasi-dynamic phantom for CT device testing, which includes a driving mechanism 1, a shell 3, a guide pipe 2, and a multiphase flow field column 4.

[0085] The guide pipe 2 is arranged in the shell 3, the multiphase flow field column 4 has a solid structure and is internally distributed with a plurality of air bubbles 5, the multiphase flow field column 4 is detachably arranged in the guide pipe 2 and can move along the axial direction of the guide pipe 2.

[0086] The shell, the multiphase flow column and the guide pipe are all made of acrylic material. The shell 3 is a cylinder with a diameter of 200 mm, which is composed of two parts to facilitate the fixation of the guide pipe 2. The multiphase flow column 4 is a cylinder, and the guide pipe 2 is a circular pipe. The inner diameter of the guide pipe 2 is adapted to the outer diameter of the multiphase flow column 4, so that the multiphase flow column can move axially in the guide pipe without deflection. The axial direction of the guide pipe 2 is arranged vertically.

[0087] In this embodiment, the driving mechanism 1 is a release-free falling mechanism, which includes a pin and a connecting line connected to the pin. The other end of the connecting line is connected to the multiphase flow column 4. When the driving mechanism receives a control signal, the pin is retracted, and the multiphase flow column 4 freely falls along the guide pipe 2. By changing the initial height of the multiphase flow column 4, the movement speed of the multiphase flow column 4 can be changed. This structure has lower cost and better anti-electromagnetic interference performance compared to motor driving.

[0088] The CT device testing method of this embodiment includes:

[0089] Step 1: Use the reference CT device to scan the multiphase flow column 4 and scan the guide pipe 2 and the shell 3 to obtain the first static three-dimensional structure data of the multiphase flow column 4 and the second static three-dimensional structure data of the guide pipe 2 and the shell 3.

[0090] Step 2: Send a control signal to make the driving mechanism act, and the multiphase flow column 4 freely falls in the guide pipe 2, while the multiphase flow standard dynamic phantom is scanned by the CT device to be tested to obtain dynamic measurement data of the multiphase flow standard dynamic phantom at different speeds.

[0091] Step 3: According to the first static three-dimensional structure data and the second static three-dimensional structure data, the true value data at each speed is calculated respectively, and based on the true value data and the dynamic measurement data, the structural similarity index corresponding to each speed is calculated. The calculation results are shown in the following table:

[0092] Speed of movement (m / s) 0.2 0.4 0.6 0.8 1.0 1.2 SSIM 0.9847 0.9805 0.9741 0.9645 0.8914 0.8352

[0093] Taking the threshold value of the structural similarity index as 0.90, it can be determined that when the movement speed of the multiphase flow column is lower than 0.8 m / s, the CT device can meet the dynamic measurement requirements of the multiphase flow system, and this movement speed can be determined as the maximum credible test speed of the CT device to be tested.

[0094] Example 2

[0095] Figure 4A structural schematic of a multiphase flow quasi-dynamic phantom for CT device testing according to an exemplary embodiment of the present application is shown. The difference from Embodiment 1 is that one guide tube 2 and one multiphase flow field column 4 form a phantom unit, the multiphase flow quasi-dynamic phantom includes four phantom units, which are substantially uniformly distributed in the shell 3 along the circumferential direction. Among them, two guide tubes 2 are arranged in the vertical direction, and the two guide tubes 2 form an included angle of 5° with the vertical direction. This multiphase flow quasi-dynamic phantom can simulate multiphase flow with a certain horizontal directional motion component.

[0096] The above has described various embodiments of the present application, the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A multiphase flow quasi-dynamic phantom for CT device testing, characterized in that, Includes the outer shell, guide tube, and multiphase flow field column; The guide tube is disposed inside the outer shell. The multiphase flow field column is a solid structure with at least one bubble distributed inside. The multiphase flow field column is detachably disposed inside the guide tube and can move along the axial direction of the guide tube. The axial direction of the guide tube is set along the vertical direction or forms an angle with the vertical direction, wherein the angle is less than or equal to 15°.

2. The multiphase quasi-dynamic phantom of claim 1, wherein, The outer casing, the multiphase flow field column, and the guide tube are all made of a polymer material that allows X-ray penetration; and / or The multiphase flow field column is cylindrical, and the guide tube is circular, with the inner diameter of the guide tube being adapted to the outer diameter of the multiphase flow field column.

3. The multiphase quasi-dynamic phantom of claim 1, wherein, The multiphase flow dynamic model also includes a driving mechanism. The multiphase flow field column is connected to the driving mechanism and can move along the axial direction of the guide tube within the guide tube under the action of the driving mechanism.

4. The multiphase quasi-dynamic phantom of claim 1, wherein, A guide tube and a multiphase flow field column form a phantom unit. The multiphase flow quasi-dynamic phantom includes multiple phantom units, which are substantially evenly distributed within the outer shell.

5. A CT device testing method using the multiphase flow quasi-dynamic phantom according to any one of claims 1-3, characterized in that, include: Step 1: Use a reference CT scanner to scan the multiphase flow field column, the guide tube, and the outer shell to obtain the first static three-dimensional structural data of the multiphase flow field column and the second static three-dimensional structural data of the guide tube and the outer shell; Step 2: Accelerate or decelerate the multiphase flow field column inside the guide tube, and scan the multiphase flow dynamic phantom using the CT device to be tested to obtain dynamic measurement data of the multiphase flow dynamic phantom at multiple different speeds. Step 3: Calculate the true value data for each speed based on the first static three-dimensional structural data and the second static three-dimensional structural data. Based on the true value data and the dynamic measurement data, calculate the structural similarity index corresponding to each speed.

6. The method of claim 5, wherein, Step 1 includes: The multiphase flow field column is scanned using a reference CT scanner to obtain voxel format data of the multiphase flow field column under static conditions. The guide tube and the outer shell are also scanned using the reference CT scanner to obtain voxel format data of the guide tube and the outer shell. Each voxel stores a floating-point number, which represents the density measurement value corresponding to the voxel. The voxel format data of the multiphase flow field column is binarized to obtain the first static three-dimensional structural data of the multiphase flow field column. The voxel format data of the guide tube and the shell are binarized to obtain the second static three-dimensional structural data of the guide tube and the shell.

7. The method of claim 5, wherein: Step 2 includes: The multiphase flow field column is placed in the guide tube, and the multiphase flow field column is made to accelerate or decelerate in the guide tube. At the same time, the multiphase flow field column is scanned multiple times using the CT equipment under test to obtain the original dynamic measurement data. Data from multiple target cycles are extracted from the original dynamic measurement data, where each target cycle corresponds to a different velocity of the multiphase flow field column. The extracted data are then subjected to CT reconstruction and binarization to obtain dynamic measurement data of the multiphase flow quasi-dynamic phantom at multiple different velocities.

8. The method of claim 7, wherein: The true value data is calculated based on the first static three-dimensional structure data and the second static three-dimensional structure data according to the following steps: Select time T in the target round as the time to calculate the structural similarity index; Based on the original dynamic measurement data, the relative positional relationship between the multiphase flow field column, the guide tube, and the outer shell at time T is determined; Based on the relative positional relationship, the first static three-dimensional structure data and the second static three-dimensional structure data are spliced ​​together to obtain the true value data of the speed corresponding to the target round.

9. The method of claim 5, wherein, The formula for calculating the structural similarity index SSIM is as follows: wherein denote the mean values of the true data and the dynamic measurement data, respectively; denote the standard deviations of the true data and the dynamic measurement data, respectively, and the covariance of both; is a constant.

10. The method of claim 5, wherein, Also includes: The maximum reliable test speed of the CT device under test is determined based on the threshold of the structural similarity index.

11. A CT device testing method using the multiphase flow quasi-dynamic phantom according to any one of claims 1-3, characterized in that, include: Step 1: Use a reference CT scanner to scan the multiphase flow field column, the guide tube, and the outer shell to obtain the first static three-dimensional structural data of the multiphase flow field column and the second static three-dimensional structural data of the guide tube and the outer shell; Step 2: Move the multiphase flow field column in the guide tube at a predetermined speed, and at the same time use the CT device to be tested to scan the multiphase flow dynamic phantom to obtain the dynamic measurement data of the multiphase flow dynamic phantom at the predetermined speed. Step 3: Calculate the true value data at the predetermined speed based on the first static three-dimensional structural data and the second static three-dimensional structural data; and calculate the structural similarity index at the predetermined speed based on the true value data and the dynamic measurement data. Step 4: Repeat steps 2 and 3 to make the multiphase flow field column move in the guide tube at different predetermined speeds, and obtain the structural similarity index corresponding to each predetermined speed.

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