Voltage regulation and control X-ray subtraction imaging method

Abstract

The invention discloses a voltage regulation and control X-ray subtraction imaging method, which is characterized in that high-energy and low-energy X-ray photons are absorbed by designing a high-thickness X-ray direct detector. The internal electric field distribution of the detector is adjusted by changing the bias voltage, and part of photon-generated carriers are selectively absorbed. X-rays obtained under different voltages are used for subtraction according to a certain algorithm, different substance attributes in an X-ray image can be judged, and images of substances with different attributes are separately displayed. According to the invention, a set of different energy spectrum X-ray image separation and subtraction algorithm is provided, and the spatial distribution of different density parts of a detected object is obtained by using X-ray transmission images under different bias voltages; and according to the spatial distribution of different densities of the detected object, separating to obtain independent X-ray images of different substance attribute components of the detected object.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection, and in particular to the field of X-ray subtraction detection imaging. Background Technology

[0002] Since Röntgen discovered X-rays, X-ray detection and imaging has been an important means for people to obtain the internal structure of the object being detected. It has important applications in medical diagnosis, industrial non-destructive testing, and safety monitoring.

[0003] Most existing X-ray detection imaging methods employ intensity imaging. When X-rays penetrate an object being detected, areas with higher density absorb more X-rays, while areas with lower density absorb less. Therefore, the internal structure of the object can be obtained from the grayscale image formed by transmitted X-rays. The intensity change of X-rays after penetrating an object satisfies the Lambert-Beer theorem: I = I₀e⁻¹. -μL Where I0 is the intensity of the incident X-rays, I is the intensity of the transmitted X-rays, μ is the absorption coefficient of the object, and L is the thickness of the object. This formula shows that both the absorption coefficient μ (closely related to the object's density) and the object's thickness affect the intensity of the transmitted X-rays. Therefore, changes in the intensity of transmitted X-rays alone cannot distinguish whether a change in grayscale represents a change in the density or thickness of the object being examined. Furthermore, the object being examined may be a combination of multiple materials (with different densities), and these different materials overlap. Therefore, the resulting grayscale image of transmitted X-rays reflects the average effect of these overlapping materials. To more accurately analyze the internal structure of the object being examined, it is necessary to understand the internal structure of each different material within the object individually. Therefore, researchers are constantly exploring new X-ray imaging methods to meet the growing technological demands.

[0004] X-ray subtraction imaging is an important method for separating and imaging materials of different densities. X-ray subtraction imaging can generally be divided into two main categories: template subtraction (time subtraction) and dual-energy subtraction. In template X-ray subtraction imaging, the original object is first imaged with X-rays and used as a subtraction template. Then, a contrast agent is injected into the object being investigated, such as a patient's blood vessel, and an X-ray image of the object after the injection is taken. Because the contrast agent significantly absorbs X-rays, subtracting the template image from the image after the injection yields a relatively clear image of the blood vessel. However, template subtraction imaging requires two exposures before and after the injection of the contrast agent, increasing the X-ray dose to the patient. Furthermore, changes in the patient's spatial position during the two X-ray imaging processes can cause inaccuracies in the two images, resulting in subtraction imaging errors. Therefore, this invention focuses on dual-energy subtraction imaging.

[0005] The technical approach of dual-energy subtraction imaging (DSE) is to acquire low-energy and high-energy X-ray images separately, and then use subtraction algorithms to obtain separate X-ray images of low-density and high-density objects. Existing dual-energy X-ray subtraction imaging techniques include... Figure 1a , Figure 1b , Figure 1c The following are some of the working modes shown.

[0006] exist Figure 1a In the working mode, people use the high-voltage X-ray source 3 and the low-voltage X-ray source 4 (typically the high voltage is 140kV and the low voltage is 80kV) installed on the slide rail 2 to image the object 1 being detected, and the corresponding high-energy X-ray detector 8 and low-energy X-ray detector 7 obtain the image of the high-energy X-ray beam 5 and the low-energy X-ray beam 6, respectively. Figure 1b The working mode shown is the same as Figure 1a Very similar, but it uses an X-ray tube with two anodes. A high voltage is applied to the high-voltage anode 9 of the dual-energy X-ray tube, and a low voltage is applied to the low-voltage anode 10. Because the two anodes are located very close together within the tube, only one low-energy X-ray detector 7 is needed. Both operating modes still require two X-ray exposures at high and low voltages, so the problem of excessive X-ray dose to the patient is not solved. Figure 1c In this operating mode, only one high-voltage X-ray source 3 is used. Since the X-ray tube generates X-rays using bremsstrahlung, assuming a high voltage of 140 kV is applied to the anode, it will produce a broad spectrum of X-rays from 20 keV to 140 keV. Figure 1c The low-energy X-ray detector 7 first receives X-rays. Because high-energy X-rays have strong penetrating power, the low-energy X-ray detector 7 primarily deposits low-energy X-ray energy, forming a low-energy X-ray image of the object. The bottom-layer X-ray detector 11 is located below detector 7. Generally, some filter plates are placed between the two detectors. In this way, the bottom-layer X-ray detector 11 only deposits energy for high-energy X-rays, forming a high-energy X-ray image of the object. Figure 1c In this operating mode, only one high-voltage broadband X-ray exposure is needed on the object, thus effectively reducing the X-ray dose received by the patient. However, in Figure 1c This requires two detectors, increasing cost and making the imaging system more complex. Furthermore, the two vertically stacked detectors can cause image crosstalk, affecting the subtraction quality. Thirdly... Figure 1c The operating mode can only provide X-ray image subtraction at two energies, and cannot provide X-ray image subtraction at three or more energies. Summary of the Invention

[0007] The purpose of this invention is to address the problems of existing dual-energy X-ray subtraction imaging, which requires two X-ray tubes or two detectors and can only provide image information of two energy levels, by proposing a voltage-controlled X-ray subtraction imaging method. This method involves designing a very thick X-ray direct detector to absorb both high-energy and low-energy X-ray photons. By changing the bias voltage to adjust the electric field distribution inside the detector, a portion of photogenerated carriers are selectively absorbed. By subtracting X-rays obtained at different voltages according to a specific algorithm, different material properties in the X-ray image can be determined, and images of materials with different properties can be displayed separately.

[0008] The technical solution adopted in this invention is: a voltage-controlled X-ray subtraction imaging method, comprising the following steps:

[0009] 1) Determine the various bias voltage values ​​applied to the detector based on the number of material types to be identified by the subtraction imaging;

[0010] The detector includes an X-ray photon absorber made of semiconductor material; one end of the X-ray photon absorber is epitaxially layered with an n-type or p-type semiconductor layer to form a pn junction with the photon absorber, and the dark current and noise of the detector are suppressed by the depletion layer barrier of the junction region; an epitaxial layer with the same semiconductor properties is epitaxially layered on the other side of the X-ray photon absorber to form an npn or pnp photodiode X-ray detection structure; metal electrodes are deposited on the two junction end faces of the detector, and different bias voltages are applied to the detector through the metal electrodes to collect the detection current;

[0011] Suppose an X-ray imaging system wants to identify n different materials, and the number of bias voltages is m, where m ≥ n; the value of the i-th bias voltage is V. i =V threshold / m×i, where V threshold It is the maximum bias voltage that the detector can apply;

[0012] 2) Apply V1, V2, ..., V to the detector respectively. m By adjusting the bias voltage, images of X-rays with different energy spectra were obtained. Espectrum_1 ,I Espectrum_2 ,…,I Espectrum_m ;

[0013] 3) Based on the X-ray image obtained in step 2), obtain projection images P of X-rays with different energy spectra. Espectrum_1 ,P Espectrum_2 ,…,P Espectrum_m ;

[0014] 4) Calculate the ratio of any two spectral projection images based on the projection images of X-rays with different energy spectra (P). Espectrum_1 / P Espectrum_2 ),(PEspectrum_1 / P Espectrum_3 ),…,,(P Espectrum_m-1 / P Espectrum_m If these ratios are the same, it means that the objects have the same density; otherwise, it means that they have different densities.

[0015] 5) Based on the results of step 4), pixels of the same density are used to form regions of this type of material, resulting in partitions for different materials;

[0016] 6) The highest bias voltage X-ray image I obtained from step 2) Espectrum_m And the material partition map obtained in step 5) separates and displays the X-ray images of different material components.

[0017] Preferably, the X-ray photon absorber in the detector is made of a semiconductor material with a high average atomic number, high material density, and high thickness.

[0018] Preferably, the semiconductor material is a perovskite crystal.

[0019] Preferably, the thickness of the X-ray photon absorber is greater than 1 cm.

[0020] This invention obtains X-ray images after X-ray irradiation with different energy spectra by changing the bias voltage of the X-ray photodiode array; according to this invention, a set of X-ray image separation and subtraction algorithms with different energy spectra are proposed, and the spatial distribution of different density parts of the detected object is obtained by using X-ray transmission images under different bias voltages; based on the spatial distribution of different densities of the detected object, independent X-ray images of different material property components of the detected object are separated.

[0021] Most X-ray imaging systems use a X-ray tube as the X-ray source. Electrons emitted from the cathode are accelerated to very high energies in a vacuum by the anode voltage, and then bombard a metal target to produce X-ray radiation. The X-ray beam produced by an X-ray tube has a very broad energy spectrum. Figure 2 This is a typical energy spectrum of an X-ray beam emitted by an X-ray tube with an anode voltage of 150 kV. It mainly consists of two parts: the X-ray bremsstrahlung spectrum 12, which is the energy spectrum produced by bremsstrahlung, and the X-ray characteristic radiation spectrum 13, which is produced by characteristic radiation. The maximum X-ray photon energy 14 is determined by the anode voltage of the tube.

[0022] To simplify the analysis process, we will Figure 2The X-ray energy spectrum shown is divided into three energy levels: low-energy X-rays (photon energy < 50 keV), medium-energy X-rays (photon energy 50–100 keV), and high-energy X-rays (photon energy greater than 100 keV). Assume that the detector we use is a very thick all-hole detector, meaning that X-ray photons of all energy levels can be completely absorbed by the detector, and only photogenerated holes can move within the detector to form a detection current. Figure 2 In the X-ray test, the incident depth for low-energy X-rays is L1, for medium-energy X-rays it is L2, and for high-energy X-rays it is L3. Three bias voltages, V1, V2, and V3, are applied to the detector from low to high using an adjustable power supply. When the bias voltage is V1, only photogenerated carriers within a distance of L1 can be effectively collected and form a photocurrent; when the bias voltage is V2, only photogenerated carriers within a distance of L2 can be effectively collected and form a photocurrent; and when the bias voltage is V3, only photogenerated carriers within a distance of L3 can be effectively collected and form a photocurrent. Thus, the X-ray energy spectrum range detected by the detector under different bias voltages is shown in Figure 4.

[0023] This invention proposes to adopt Figure 3 The detector shown is configured with bias voltages V1, V2, and V3. Figure 5 Objects 1, 2, and 3 shown were detected as follows: Figure 4a , Figure 4b , Figure 4c The images produced by X-rays in the three energy spectrum bands are shown. For object 1...

[0024]

[0025]

[0026]

[0027] For object 2,

[0028]

[0029]

[0030]

[0031] For object 3

[0032]

[0033]

[0034]

[0035] In the formula E spectrum_1 Espectrum_2 E spectrum_3 Represent Figure 4a The three X-ray energy spectra of 4b and 4c; I0(E spectrum_1 ),I0(E spectrum_2 ),I0(E spectrum_3 ) represent the intensity distribution of these three energy spectrum X-rays before they pass through the object; I(E) spectrum_1 )1,I(E spectrum_1 )2,I(E spectrum_1 )3 respectively represent the energy spectrum of E spectrum_1 X-ray intensity distribution after passing through objects 1, 2, and 3; I(E) spectrum_2 )1,I(E spectrum_2 )2,I(E spectrum_2 )3 respectively represent the energy spectrum of E spectrum_2 X-ray intensity distribution after passing through objects 1, 2, and 3; I(E) spectrum_3 )1,I(E spectrum_3 )2,I(E spectrum_3 )3 respectively represent the energy spectrum of E spectrum_3 The intensity distribution of X-rays after passing through objects 1, 2, and 3; μ1, μ2, and μ3 are the absorption coefficients of objects 1, 2, and 3 (related to the density of the material); d1, d2, and d3 are the thicknesses of objects 1, 2, and 3. Based on formulas 1, 2, and 3, the projection images of these objects under X-ray irradiation with different energy spectra can be obtained. Formula (4) is the intensity distribution of object 1 under E... spectrum_1 E spectrum_2 E spectrum_3 Projection image under energy spectrum X-ray irradiation

[0036]

[0037]

[0038]

[0039] Formula (5) is the equation for object 2 at point E. spectrum_1 E spectrum_2 E spectrum_3 Projection image under energy spectrum X-ray irradiation

[0040]

[0041]

[0042]

[0043] Formula (6) is the equation for object 3 in E. spectrum_1 E spectrum_2 E spectrum_3Projection image under energy spectrum X-ray irradiation

[0044]

[0045]

[0046]

[0047] Based on the projected images from formulas 4, 5, and 6, we can obtain the following for object 1:

[0048]

[0049]

[0050]

[0051] As can be seen from the formula above, object 1 exists in both energy spectra E. spectrum_1 E spectrum_2 The ratio of X-ray irradiation projection images Only related to the absorption coefficient μ1(E of object 1) spectrum_1 ) and μ1(E spectrum_2 It is related to the thickness d1 of object 1, but not to the thickness d1 of object 1. Therefore, we can... Figure 5 Calculation of projection images of different objects under X-ray irradiation of different energy spectra and If these ratios are the same in different regions, it means they have the same material density. Conversely, if they are different, it means the material densities in these spatial regions are different. Similar to formula (7), we can obtain the discriminant for the density of object 2.

[0052]

[0053]

[0054]

[0055] Formula (9) is the discriminant for the density of an object.

[0056]

[0057]

[0058]

[0059] Based on formulas (7), (8), and (9), we can... Figure 6a , Figure 6b , Figure 6cThe distribution regions of different material densities were calculated from X-ray images obtained under different bias voltages, and then the distribution regions of different material properties were estimated. The following is an example of different material distributions obtained using the above method.

[0060] Figure 7 We are based on Figure 6a , Figure 6b , Figure 6c The X-ray images shown illustrate the distribution of different material zones obtained through formulas 7, 8, and 9. Figure 8a , Figure 8b , Figure 8c These are individual X-ray images of different materials obtained by separating them into different material zones.

[0061] The beneficial effects of this invention are:

[0062] (1) In conventional X-ray images, the gray level is determined by the object's density and is also affected by its thickness. It is difficult to determine which areas have a higher object density and which have a lower object density from the gray level image alone. The voltage-controlled X-ray subtraction imaging method proposed in this invention can identify the object density in different areas and thus distinguish the composition of the material.

[0063] (2). Conventional dual-energy X-ray subtraction imaging can only provide two energy spectrum X-ray image information, while the voltage-controlled X-ray subtraction imaging method proposed in this invention can obtain multiple energy spectrum X-ray image information;

[0064] (3). Based on the previously identified density distribution of objects in different regions, the present invention can also separate individual images of different material regions of an object, thereby improving the identification capability of X-ray images;

[0065] (4). The X-ray subtraction imaging method and detector structure proposed in this invention help to enable machine intelligent recognition of X-ray images. Attached Figure Description

[0066] Figure 1a This is a subtraction imaging image from two X-ray tubes; Figure 1b This is a single-tube, dual-anode X-ray subtraction imaging image; Figure 1c This is an X-ray subtraction imaging image of a single X-ray tube with dual detectors;

[0067] Figure 2 The X-ray energy spectrum of radiation from a X-ray tube with an anode voltage of 150 kV;

[0068] Figure 3 Schematic diagram of X-ray photons of different energies incident on the detector;

[0069] Figure 4a This represents the range of X-ray energy spectrum detected by the detector under bias voltage V1. Figure 4bThis represents the range of X-ray energy spectrum detected by the detector under bias voltage V2. Figure 4c This represents the range of X-ray energy spectrum detected by the detector under bias voltage V3.

[0070] Figure 5 Imaging three objects with different densities and thicknesses using X-rays of three different energy spectra;

[0071] Figure 6a The X-ray image is obtained directly from the detector with a bias voltage of -10V. Figure 6b The X-ray image is obtained directly from the detector with a bias voltage of -15V. Figure 6c The X-ray image is obtained directly from the detector with a bias voltage of -20V.

[0072] Figure 7 Different materials are distributed in zones;

[0073] Figure 8a To separate individual images of different material components (images of metal parts) based on material partitioning;

[0074] Figure 8b To separate individual images of different material components (images of plastic parts) based on material partitioning;

[0075] Figure 8c To separate individual images (tape images) of different material components based on material partitioning;

[0076] In the diagram: 1. Object being detected; 2. Sliding rail; 3. High-voltage X-ray source; 4. Low-voltage X-ray source; 5. High-energy X-ray beam; 6. Low-energy X-ray beam; 7. Low-energy X-ray detector; 8. High-energy X-ray detector; 9. High-voltage anode of dual-energy X-ray tube; 10. Low-voltage anode of dual-energy X-ray tube; 11. Bottom-layer X-ray detector; 12. X-ray bremsstrahlung spectrum; 13. Characteristic X-ray radiation spectrum; 14. Maximum X-ray photon energy. Detailed Implementation

[0077] The present invention will now be described in detail. This embodiment is implemented based on the technical solution of the present invention, and provides detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiment.

[0078] The voltage-controlled X-ray subtraction imaging method proposed in this invention comprises the following steps:

[0079] 1) Determine the bias voltage values ​​applied to the detector based on the number of material types to be identified by subtraction imaging. Assume the X-ray imaging system wants to identify n different materials, and the number of bias voltages is m, where m ≥ n. The i-th bias voltage value is V. i =Vthreshold / m×i, where V threshold It is the maximum bias voltage that the detector can apply;

[0080] 2) Apply V1, V2, ..., V to the detector respectively. m By adjusting the bias voltage, images of X-rays with different energy spectra were obtained. Espectrum_1 ,I Espectrum_2 ,…,I Espectrum_m ;

[0081] 3) Based on the X-ray image obtained in step 2, obtain projection images P of X-rays with different energy spectra. Espectrum_1 ,P Espectrum_2 ,…,P Espectrum_m ;

[0082] 4) Calculate the ratio of any two spectral projection images based on the projection images of X-rays with different energy spectra (P). Espectrum_1 / P Espectrum_2 ),(P Espectrum_1 / P Espectrum_3 ),…,,(P Espectrum_m-1 / P Espectrum_m If these ratios are the same, it means the objects have the same density. Conversely, if they are different, it means they have different densities.

[0083] 5) Based on the results of step 4, pixels of the same density are used to form regions of this type of material, resulting in partitions for different materials;

[0084] 6) Based on the highest bias voltage X-ray image I obtained in step 2 Espectrum_m The material partition map obtained in step 5 separates and displays the X-ray images of different material components.

[0085] The voltage-controlled X-ray subtraction imaging detector proposed in this invention has the following structure:

[0086] The detector uses a semiconductor material with a high average atomic number and high material density as the X-ray photon absorber. To fully deposit high-energy X-rays (~140 keV), the thickness of the semiconductor photon absorber is greater than 1 cm. Junction regions with different semiconductor properties from the absorber are prepared at both ends of the semiconductor photon absorber by epitaxy or doping, and the depletion layer of the junction region is used to suppress dark current and noise. The carrier transport of the detector is made unipolar by doping the photon absorber or modulating the junction barrier. Metal electrodes are deposited on the two junction end faces of the detector, and different bias voltages are applied to the detector through the metal electrodes to collect the detection current.

[0087] The fabrication process of this detector is illustrated below using MAPbBr3 crystal as an example:

[0088] 1) Mix aqueous methylamine and aqueous hydrobromic acid at a molar ratio of 1:1.2 in a water bath at 0°C. After the reaction is complete, let it stand for 10 minutes. Pour the solution into a rotary evaporator and evaporate to dryness, collecting the precipitated white powder. Wash the white powder with diethyl ether, remove excess ether, and add excess ethanol. Pour the ethanol suspension into a rotary evaporator and evaporate to dryness again to obtain CH3NH3Br powder. Dissolve the CH3NH3Br powder obtained in the reaction solution at a concentration of 1 mol / L in dimethylformamide (DMF), stirring and sonicating with a glass rod until completely dissolved. Weigh out PbBr2 in a 1:1 molar ratio and slowly pour it into the solution prepared in the previous step. Stir and sonicate until completely dissolved to obtain a clear and transparent reaction precursor solution.

[0089] 2) Heat the precursor solution in a water bath, with an initial temperature not exceeding 20°C. Perform the first stage of heating at a rate of 0.5°C / min until the solution reaches 60°C. Maintain this temperature at 60°C until single crystal nuclei begin to appear in the solution. After the appearance of single crystal nuclei, allow them to grow slowly for 30 minutes. Increase the heating power for the second stage of heating at a rate of 0.2°C / min until the solution reaches 65°C. Maintain this temperature at 65°C for 30 minutes, then increase the heating power again for the third stage of heating at a rate of 0.2°C / min until the solution reaches 70°C, at which point the single crystals enter the rapid growth stage. Maintain this temperature at 70°C for 30 minutes, then increase the heating power again for the fourth stage of heating at a rate of 0.1°C / min until the solution reaches 80°C. Allow the reaction to proceed at this temperature for a sufficient time until the crystal size meets the design requirements.

[0090] Because MAPbBr3 crystal is a weakly p-type crystal, we grow an n-type epitaxial layer on the crystal to form an npn structure.

[0091] Taking the MAPbCl3 epitaxial layer as an example, its growth process is as follows:

[0092] 1) 1 mol L -1 methylammonium chloride (MACl), 1 mol L -1 PbCl2 was dissolved in a mixture of 60 ml DMF and 60 ml DMSO in sequence, and then filtered through a 35 μm organic filter to obtain the precursor solution, which was then placed in a quantitative culture dish.

[0093] 2) The MAPbBr3 substrate prepared above was immersed in the precursor solution, and the temperature was raised from 40 degrees to 70 degrees at a rate of 0.5 degrees / hour using a heating stage to grow a high-quality MAPbCl3 single crystal epitaxial layer.

[0094] 3) If the n-row epitaxial layer is designed to be relatively thick, some MAPbBr3 layers need to be inserted between the MAPbBr3 substrate and the MAPbCl3 epitaxial layer. x Cl (3-x) Buffer layer. The precursor solution for the buffer layer can be obtained by dissolving MABr and PbCl2 in a mixed solution of DMF and DMSO. By adjusting the ratio of MABr and PbCl2, the MABr / PbCl2 concentration can be changed. x Cl (3-x) The x-value of the buffer layer;

[0095] 4) The MAPbBr3 substrate and the upper and lower surfaces of MAPbCl3 are exposed by mechanical cutting and polishing, respectively. Then, the same method as in step (3) is used to deposit a MAPbCl3 n-type epitaxial layer on the upper surface of MAPbBr3.

[0096] 5) Deposit metal electrodes on the end faces of the upper and lower n-type layers to form an X-ray detection photodiode.

[0097] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A voltage-controlled X-ray subtraction imaging method, characterized in that: Includes the following steps: 1) Determine the various bias voltage values ​​applied to the detector based on the number of material types to be identified by subtraction imaging; The detector includes an X-ray photon absorber made of semiconductor material; one end of the X-ray photon absorber is epitaxially layered with an n-type or p-type semiconductor layer to form a pn junction with the photon absorber, and the dark current and noise of the detector are suppressed by the depletion layer barrier of the junction region; an epitaxial layer with the same semiconductor properties is epitaxially layered on the other side of the X-ray photon absorber to form an npn or pnp photodiode X-ray detection structure; metal electrodes are deposited on the two junction end faces of the detector, and different bias voltages are applied to the detector through the metal electrodes to collect the detection current; Suppose that an X-ray imaging system wants to identify n different materials, and the number of bias voltages is m, where m ≥ n; The i-th bias voltage value is V i =V threshold / m×i, where V threshold It is the maximum bias voltage that the detector can apply; 2) Apply V1, V2, ..., V to the detector respectively. m By adjusting the bias voltage, images of X-rays with different energy spectra were obtained. Espectrum_1 ,I Espectrum_2 ,…,I Espectrum_m ; 3) Based on the X-ray image obtained in step 2), obtain projection images P of X-rays with different energy spectra. Espectrum_1 ,P Espectrum_2 ,…,P Espectrum_m ; 4) Calculate the ratio of any two spectral projection images based on the projection images of X-rays with different energy spectra (P). Espectrum_1 / P Espectrum_2 ),(P Espectrum_1 / P Espectrum_3 ),…,,(P Espectrum_m-1 / P Espectrum_m If these ratios are the same, it means that the objects have the same density; otherwise, it means that they have different densities. 5) Based on the results of step 4), pixels of the same density are used to form regions of this type of material, resulting in partitions for different materials; 6) The highest bias voltage X-ray image I obtained from step 2) Espectrum_m And the material partition map obtained in step 5) separates and displays the X-ray images of different material components.

2. The voltage-controlled X-ray subtraction imaging method according to claim 1, characterized in that: The X-ray photon absorber in the detector is made of semiconductor material with high average atomic number, high material density, and high thickness.

3. The voltage-controlled X-ray subtraction imaging method according to claim 2, characterized in that: The semiconductor material is a perovskite crystal.

4. The voltage-controlled X-ray subtraction imaging method according to claim 2, characterized in that: The thickness of the X-ray photon absorber is greater than 1 cm.

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