Asymmetric cone-beam inspection method for high-resolution imaging of closed interior of aeroengine

Abstract

The invention discloses an asymmetric cone beam detection method for high-resolution imaging of a closed inner cavity of an aircraft engine, comprising: preparing a mixture of radioactive nuclides and aviation kerosene and injecting the mixture into the closed inner cavity of the aircraft engine; installing and fixing the aircraft engine on a fixed detection table inside a positron emission tomography scanner; a rotating cylinder is provided on the outer periphery of the fixed detection table inside the positron emission tomography scanner, a first detector array composed of a plurality of rows of γ photon detection crystals arranged in an arc shape and a second detector array composed of a plurality of rows of γ photon detection crystals arranged in an arc shape facing the first detector array are provided on the inner wall of the rotating cylinder; the rotating first detector array and the second detector array perform real-time data collection at any angle on γ photon pairs generated by annihilation of the aviation kerosene mixture after nuclides labeling in the closed inner cavity of the aircraft engine; and three-dimensional image reconstruction is performed on the detected γ photon fan beam data to obtain high-resolution imaging.

Description

Technical Field

[0001] The invention relates to the field of positron emission tomography devices and image reconstruction, and in particular to an asymmetric cone beam detection method for high-resolution imaging of a closed inner cavity of an aero-engine. Background Art

[0002] Positron emission tomography (PET) is a technology that uses high-energy gamma photons produced by positron annihilation to image and depict the internal state of an object. The gamma photon pairs produced by positron annihilation have stable direction and energy characteristics, are not affected by changes in the external environment such as electric fields, magnetic fields, and temperature, and can penetrate metals and other materials with high density, which makes PET technology present a unique advantage in industrial non-destructive testing. Using the annihilation phenomenon of positrons, positron annihilation technology has become a non-destructive detection and analysis method for studying the material structure (material surface and internal defects) and electronic state (electron momentum distribution) of materials such as metals, semiconductors, high-temperature superconductors, and polymers. Due to its strong penetration, the use of working fluids as detection sources, and three-dimensional imaging, the prospects for positron annihilation non-destructive testing technology will be very broad once the problem of high-resolution imaging in industrial non-destructive testing is solved.

[0003] With the development of aviation propulsion technology, chemical technology, nuclear industry technology, computing technology and electronic computer application technology, more and more new technologies are applied to industrial non-destructive testing, so higher and higher requirements are put forward for non-destructive testing technology. When PET is used for non-destructive testing in the aviation industry, due to the influence of the inherent low resolution of the detector and the characteristics of γ photons, the internal environment of the aircraft engine is complex, and the resolution is low when imaging the closed cavity. High-resolution imaging of the closed cavity of aircraft engines is of great help to the development of my country's aviation industry, and can provide an efficient means for the detection of the closed cavity of aircraft engines in my country. Summary of the invention

[0004] In view of the problems raised in the background technology, the present invention aims to provide an asymmetric cone-beam detection method for high-resolution imaging of a closed inner cavity of an aircraft engine.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: an asymmetric cone beam detection method for high-resolution imaging of a closed cavity of an aircraft engine, comprising the following steps:

[0006] Step 1: Prepare radioactive nuclides and fully mix them with aviation kerosene;

[0007] Step 2: injecting the mixed radioactive nuclides and aviation kerosene into the closed inner cavity of the aircraft engine;

[0008] Step 3: the aircraft engine after being perfused with a mixture of radioactive nuclides and aviation kerosene is installed and fixed on a fixed detection table inside a positron emission tomography scanner; a rotating cylinder and a rotating power device for driving the rotating cylinder to rotate are arranged on the outer periphery of the fixed detection table inside the positron emission tomography scanner, and the gamma photon detection device of the positron emission tomography scanner comprises a first detector array composed of a plurality of rows of gamma photon detection crystals arranged in a circular arc shape arranged along the axial direction on the inner wall of the rotating cylinder, and a second detector array composed of a plurality of rows of gamma photon detection crystals arranged in a circular arc shape on the inner wall of the rotating cylinder facing the first detector array; the center angle corresponding to the gamma photon detection crystals of the first detector array is 30-90°; the center angle corresponding to the gamma photon detection crystals of the second detector array is 8-10° larger than the center angle corresponding to the gamma photon detection crystals of the first detector array; and the diameter of the first detector array is 1.3-1.6 times that of the second detector array;

[0009] Step 4: Start the rotating cylinder and the positron emission tomography scanner, and the rotating first detector array and the second detector array collect data at any angle in real time on the gamma photon pairs generated by the annihilation of the radionuclide-labeled aviation kerosene mixture in the closed inner cavity of the aircraft engine;

[0010] Step 5: Perform three-dimensional image reconstruction on the γ-photon fan beam data detected by the first detector array and the second detector array to obtain high-resolution imaging of the closed inner cavity of the aircraft engine.

[0011] As a preferred embodiment, in step 1, the radionuclide is 64 Cu, mix the radioactive nuclide and aviation kerosene thoroughly in a blender.

[0012] As a preferred solution, in step 5, the collected γ-photon fan beam data is used to reconstruct a three-dimensional image based on a filtered back-projection algorithm.

[0013] As a preferred solution, in step 5, the fan beam data collected at any angle is reconstructed based on a filtered back projection algorithm.

[0014] In two-dimensional plane, the projection line can be expressed as:

[0015]

[0016] Where, θ is the projection angle, L is the projection distance;

[0017] The projection of the image function F(x,y) in the projection direction is:

[0018]

[0019] When the projection data is back-projected by fan-beam filtering, R(ω) is obtained by Fourier transform, which is then multiplied by the filter function H(ω) and inverse Fourier transformed to obtain the reconstructed image F′(x,y);

[0020] The formula for reconstructing the image is:

[0021]

[0022] Among them, ω is the filter function frequency, R(ω) is the Fourier transform function of the projection function, and H(ω) is the filter function.

[0023] The beneficial effects of the present invention are as follows: an aircraft engine filled with a mixture of radioactive nuclides and aviation kerosene is installed and fixed on a fixed detection table inside a positron emission tomography scanner; a rotating cylinder and a rotating power device for driving the rotating cylinder to rotate are arranged on the outer periphery of the fixed detection table inside the positron emission tomography scanner; a gamma photon detection device of the positron emission tomography scanner comprises a first detector array composed of a plurality of rows of gamma photon detection crystals arranged in an arc shape along the axial direction on the inner wall of the rotating cylinder and a second detector array composed of a plurality of rows of gamma photon detection crystals arranged in an arc shape on the inner wall of the rotating cylinder facing the first detector array; the gamma photons of the first detector array are detected by the detector array; The center angle corresponding to the detection crystal is 30-90°; the center angle corresponding to the γ photon detection crystal of the second detector array is 8-10° larger than the center angle corresponding to the γ photon detection crystal of the first detector array; and the diameter of the first detector array is 1.3-1.6 times that of the second detector array; the rotating first detector array and the second detector array perform real-time data collection at any angle on the γ photon pairs generated by the annihilation of the aviation kerosene mixture after radionuclide labeling in the closed inner cavity of the aircraft engine; the γ photon fan beam data detected by the first detector array and the second detector array are reconstructed into a three-dimensional image to obtain high-resolution imaging of the closed inner cavity of the aircraft engine.

[0024] The patent of the present invention provides a method of adding a high-resolution rotating detector array without changing the inherent resolution of the PET detector to form an asymmetric cone-beam imaging system. The system can reduce the dependence of the imaging system on the inherent resolution of the PET detector. The resolution of the asymmetric cone-beam imaging system is related to the width of the detector array and the distance from the object to be measured to the detector array. The smaller the width of the detector array and the distance from the object to be measured to the detector array, the higher the resolution of the imaging system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a main structural schematic diagram of the present invention.

[0026] In the figure: 1 second detector array, 2 fixed detection platform, 3 first detector array. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0028] like Figure 1 As shown, an asymmetric cone beam detection method for high-resolution imaging of a closed inner cavity of an aircraft engine comprises the following steps:

[0029] Step 1: Prepare the radioactive nuclide 64 Cu, the radioactive nuclide and the aviation kerosene are thoroughly mixed in a blender;

[0030] Step 2: injecting the mixed radioactive nuclides and aviation kerosene into the closed inner cavity of the aircraft engine;

[0031] Step 3: the aircraft engine after being perfused with a mixture of radioactive nuclides and aviation kerosene is installed and fixed on a fixed detection table inside a positron emission tomography scanner; a rotating cylinder and a rotating power device for driving the rotating cylinder to rotate are arranged on the outer periphery of the fixed detection table inside the positron emission tomography scanner, and the gamma photon detection device of the positron emission tomography scanner comprises a first detector array composed of a plurality of rows of gamma photon detection crystals arranged in a circular arc shape arranged along the axial direction on the inner wall of the rotating cylinder, and a second detector array composed of a plurality of rows of gamma photon detection crystals arranged in a circular arc shape on the inner wall of the rotating cylinder facing the first detector array; the center angle corresponding to the gamma photon detection crystals of the first detector array is 30-90°; the center angle corresponding to the gamma photon detection crystals of the second detector array is 8-10° larger than the center angle corresponding to the gamma photon detection crystals of the first detector array; and the diameter of the first detector array is 1.3-1.6 times that of the second detector array;

[0032] Step 4: Start the rotating cylinder and the positron emission tomography scanner, and the rotating first detector array and the second detector array collect data at any angle in real time on the gamma photon pairs generated by the annihilation of the radionuclide-labeled aviation kerosene mixture in the closed inner cavity of the aircraft engine;

[0033] Step 5: Perform three-dimensional image reconstruction on the γ-photon fan beam data detected by the first detector array and the second detector array based on the filtered back projection algorithm to obtain high-resolution imaging of the closed inner cavity of the aircraft engine; the details are as follows:

[0034] In two-dimensional plane, the projection line can be expressed as:

[0035]

[0036] Where, θ is the projection angle, L is the projection distance;

[0037] The projection of the image function F(x,y) in the projection direction is:

[0038]

[0039] When the projection data is back-projected by fan-beam filtering, R(ω) is obtained by Fourier transform, which is then multiplied by the filter function H(ω) and inverse Fourier transformed to obtain the reconstructed image F′(x,y);

[0040] The formula for reconstructing the image is:

[0041]

[0042] Among them, ω is the filter function frequency, R(ω) is the Fourier transform function of the projection function, and H(ω) is the filter function.

[0043] In this imaging system, the response lines between the detection crystals in the first detector array and all the detection crystals in the second detector array form a fan-shaped beam; the width of the detection crystals in the first detector array is recorded as w1, the width of the detection crystals in the second detector array is recorded as w2, and the distances from the object to be measured to the detector array are recorded as d1 and d2 respectively. Then the magnification factor of the fan-shaped beam is .

[0044] The image resolution of this imaging system is a function of the width of the detector array and the distance from the object to the detector array.

[0045]

[0046] where Rs is the effective source size including positron range effects.

[0047] The method of the patent of the present invention is based on the inherent resolution of the existing detector, and increases the asymmetric cone beam rotating detection crystal to improve the imaging resolution, thereby further improving the resolution based on the inherent resolution.

[0048] The above-mentioned embodiments are only illustrative of the principles and effects of the invention, as well as some embodiments of its application, and are not intended to limit the invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the invention, and all of these belong to the protection scope of the invention.

Claims

1. An asymmetric cone-beam detection method for high-resolution imaging of a closed cavity of an aircraft engine, comprising the following steps: Step 1: Prepare radioactive nuclides and fully mix them with aviation kerosene; Step 2: injecting the mixed radioactive nuclides and aviation kerosene into the closed inner cavity of the aircraft engine; Step 3: the aircraft engine after being perfused with a mixture of radioactive nuclides and aviation kerosene is installed and fixed on a fixed detection table inside a positron emission tomography scanner; a rotating cylinder and a rotating power device for driving the rotating cylinder to rotate are arranged on the outer periphery of the fixed detection table inside the positron emission tomography scanner, and the gamma photon detection device of the positron emission tomography scanner comprises a first detector array composed of a plurality of rows of gamma photon detection crystals arranged in a circular arc shape arranged along the axial direction on the inner wall of the rotating cylinder, and a second detector array composed of a plurality of rows of gamma photon detection crystals arranged in a circular arc shape on the inner wall of the rotating cylinder facing the first detector array; the center angle corresponding to the gamma photon detection crystals of the first detector array is 30-90°; the center angle corresponding to the gamma photon detection crystals of the second detector array is 8-10° larger than the center angle corresponding to the gamma photon detection crystals of the first detector array; and the diameter of the first detector array is 1.3-1.6 times that of the second detector array; Step 4: Start the rotating cylinder and the positron emission tomography scanner, and the rotating first detector array and the second detector array collect data at any angle in real time on the gamma photon pairs generated by the annihilation of the radionuclide-labeled aviation kerosene mixture in the closed inner cavity of the aircraft engine; Step 5: Perform three-dimensional image reconstruction on the γ-photon fan beam data detected by the first detector array and the second detector array to obtain high-resolution imaging of the closed inner cavity of the aircraft engine.

2. The asymmetric cone-beam detection method for high-resolution imaging of an aircraft engine closed cavity according to claim 1, characterized in that: In the step 1, the radionuclide is 64 Cu, mix the radioactive nuclide and aviation kerosene thoroughly in a blender.

3. The asymmetric cone-beam detection method for high-resolution imaging of the closed inner cavity of an aircraft engine according to claim 2, characterized in that: In step 5, the collected γ-photon fan beam data is used to reconstruct a three-dimensional image based on a filtered back-projection algorithm.

4. The asymmetric cone-beam detection method for high-resolution imaging of an aircraft engine closed cavity according to claim 3, characterized in that: In step 5, the fan beam data collected at any angle is used to reconstruct an image based on a filtered back projection algorithm. In two-dimensional plane, the projection line can be expressed as: Where, θ is the projection angle, L is the projection distance; The projection of the image function F(x,y) in the projection direction is: When the projection data is back-projected by fan-beam filtering, R(ω) is obtained by Fourier transform, which is then multiplied by the filter function H(ω) and inverse Fourier transformed to obtain the reconstructed image F′(x,y); The formula for reconstructing the image is: Among them, ω is the filter function frequency, R(ω) is the Fourier transform function of the projection function, and H(ω) is the filter function.

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