Material identification method and material identification device

Abstract

The present disclosure provides a material identification method, comprising: detecting a radiation ray signal by using a plurality of detector modules of a radiation detector in response to scanning a target object by using the radiation ray, the plurality of detector modules being arranged at different positions and the ray signal channels being independent of each other; calculating N ray indexes corresponding to the position of each detector module according to the radiation ray signal detected by each detector module, N being an integer greater than or equal to 1; and identifying the material of the target object according to the index values of each ray index at different positions. The present disclosure also discloses a material identification device.

Description

Technical Field

[0001] This disclosure relates to the fields of security inspection, backscattering, material identification, or other fields, and more specifically, to material identification methods and devices. Background Technology

[0002] When radiation rays enter an object, some of them undergo Compton scattering. During this process, the energy and direction of the radiation rays change. Some of these rays change their direction of flight so much that they return to the side where the radiation source is located. These rays are called backscattered rays, or simply backscattered rays.

[0003] In related technologies, radiation detectors can convert detected rays into a large number of photons through a large area of ​​ray-sensitive medium. Then, photoelectric conversion devices convert the photons into electronic signals. After amplification, ADC (analog-to-digital converter) sampling technology is used to generate the corresponding digital signal sequence. Finally, backscatter scanning results are obtained based on integral (also known as current-based) digital signal processing.

[0004] When scanning one or more points on a target object, transmitted or scattered rays from the same scanning point are detected at multiple locations by the radiation detector's radiation-sensitive medium. Currently, the sum of the detection data from each location is simply used as the radiation signal for the same scanning point. A radiation image is obtained based on the radiation signal obtained from the summation, and material identification results are then derived from the radiation image.

[0005] In realizing the inventive concept disclosed herein, the inventors discovered that obtaining radiation ray signals based on the summation of detection data, and then processing the radiation ray signals to obtain radiation images, results in the loss of some information, which is not conducive to improving the accuracy of material identification. Summary of the Invention

[0006] In view of the above problems, this disclosure provides a material identification method and a material identification device.

[0007] According to a first aspect of this disclosure, a material identification method is provided, comprising: in response to a radiation ray scanning target object, detecting radiation ray signals using multiple detector modules of a radiation detector, the multiple detector modules being arranged at different positions and the ray signal channels being independent of each other; calculating N ray indicators corresponding to the location of each detector module based on the radiation ray signals detected by each detector module, where N is an integer greater than or equal to 1; and identifying the material of the target object based on the indicator values ​​of each ray indicator at different locations.

[0008] In some embodiments, the N ray indicators include a first ray indicator and a second ray indicator. Identifying the material of the target object based on the indicator value of each ray indicator at different positions includes: mapping the indicator values ​​of the first ray indicator and the second ray indicator at different positions onto a coordinate system, wherein the vertical axis of the coordinate system corresponds to the first ray indicator and the horizontal axis of the coordinate system corresponds to the second ray indicator; and identifying the material of the target object based on the distribution of the first ray indicator and the second ray indicator in the coordinate system.

[0009] In some embodiments, detecting radiation signals using multiple detector modules of a radiation detector in response to a radiation ray scanning target object includes: detecting backscattered ray signals reflected by the target object using multiple detector modules in response to a radiation source emitting radiation rays to perform a flying-spot scan of the target object.

[0010] In some embodiments, calculating the N ray indicators corresponding to the location of each detector module includes: for each ray indicator, calculating multiple indicator values ​​corresponding to the location of each detector module; wherein, the multiple indicator values ​​correspond one-to-one with multiple point locations of the target object being scanned by ray radiation.

[0011] In some embodiments, before calculating the N ray indicators corresponding to the location of each detector module, the method further includes: assigning a corresponding location identifier according to the location of each detector module; wherein the N ray indicators corresponding to the location of each detector module are bound to the location identifier of the detector module.

[0012] In some embodiments, before calculating the N radiation indicators corresponding to the location of each detector module, the method further includes: performing energy threshold judgment on multiple sets of radiation signals to filter out radiation signals under different energy ranges from each set of radiation signals, wherein multiple sets of radiation signals correspond one-to-one with multiple detector modules; and obtaining the number of radiation signals under different energy ranges in each set of radiation signals.

[0013] In some embodiments, calculating the N ray indicators corresponding to the location of each detector module includes: for each group of ray signals, obtaining the number of targets in the target energy range of the ray signals in different energy ranges; calculating the proportion of the number of targets to the total number of ray signals to obtain the first ray indicator, wherein the total number of ray signals is obtained based on the sum of the number of all ray signals in different energy ranges.

[0014] In some embodiments, calculating the N radiation indicators corresponding to the location of each detector module includes: calculating the ratio of the total number of radiation signals to the counting period to obtain the second radiation indicator, wherein the total number of radiation signals is obtained based on the sum of the number of all radiation signals under different energy ranges, and the counting period includes the period for acquiring the number.

[0015] In some embodiments, identifying the material of a target object based on the index values ​​of each ray index at different locations includes: matching the index values ​​of each ray index at different locations with the index information of different materials, wherein the index information of different materials includes the pre-calculated index values ​​of different materials at different locations; and identifying the material of the target object based on the matching results.

[0016] In some embodiments, a radiation source emits radiation rays, and two radiation detectors are set on both sides of the radiation source; wherein, detecting the radiation ray signal using multiple detector modules of the radiation detectors includes: detecting the radiation ray signal using multiple detector modules of each of the two radiation detectors.

[0017] In some embodiments, the two radiation detectors distributed on both sides of the radiation source have different structures and each detects radiation signals from different regions of the corresponding target object. The structure of each radiation detector is determined according to the region of the target object being detected, and the detector structure includes the detection area of ​​each of the multiple detector modules.

[0018] In some embodiments, before matching the index values ​​of each ray index at different locations with the index information of different materials, the method further includes: determining the index information of the material to be matched based on the structure of each of the two radiation detectors; wherein the index information of the material to be matched is calculated based on the radiation ray signals of the material to be matched detected by the two preset radiation detectors, and the two preset radiation detectors have a one-to-one correspondence with the two radiation detectors and have approximately the same structure.

[0019] Another aspect of this disclosure provides a material identification device for performing the material identification method as described in any of the preceding claims. The material identification device includes: a radiation detector for detecting radiation signals using multiple detector modules in response to a radiation ray scanning target object. The multiple detector modules are arranged at different locations and their ray signal channels are independent of each other. A processor, communicatively connected to the radiation detector, is configured to perform the following operations: calculating N ray indicators corresponding to the location of each detector module based on the radiation ray signals detected by each detector module, where N is an integer greater than or equal to 1; and identifying the material of the target object based on the indicator values ​​of each ray indicator at different locations.

[0020] The above one or more embodiments have the following beneficial effects:

[0021] The signals generated by detector modules at different locations within a radiation detector differ, and these differences can be compared to obtain additional information. Multiple detector modules distributed at different locations receive radiation rays from a scanned target object using their respective X-ray signal channels, enabling independent calculation of one or more X-ray indices for each location. By analyzing the distribution differences of each X-ray index value across different locations, the material of the target object can be accurately identified. Attached Figure Description

[0022] The foregoing contents, as well as other objects, features, and advantages of this disclosure, will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0023] Figure 1 This diagram illustrates an application scenario of a backscatter detection device in the relevant technology.

[0024] Figure 2 A sequence of ray events for an incident backscatter detector according to an embodiment of the present disclosure is shown;

[0025] Figure 3 A schematic diagram showing the change in the number of photons excited by a single ray over time according to an embodiment of the present disclosure is shown;

[0026] Figure 4 This illustrates pulsed electrical signals with signal stacking and superposition in related technologies;

[0027] Figure 5 This diagram schematically illustrates an application scenario of a backscatter detection device according to an embodiment of the present disclosure.

[0028] Figure 6 A schematic diagram of the layout of the radiation source and backscatter detector according to an embodiment of the present disclosure is shown;

[0029] Figure 7 A schematic diagram of the layout of a radiation source and a backscatter detector according to another embodiment of the present disclosure is shown;

[0030] Figure 8 A schematic diagram of the layout of a radiation source and a backscatter detector according to another embodiment of the present disclosure is shown;

[0031] Figure 9 A schematic diagram comparing the response pulse waveforms of a fast-attenuation crystal (GAGG) and a slow-attenuation crystal (GOS) according to embodiments of the present disclosure is shown.

[0032] Figure 10 A waveform diagram of the pulse electrical signal output by the detector module according to an embodiment of the present disclosure is shown;

[0033] Figure 11This diagram schematically illustrates an application scenario of a material identification device according to an embodiment of the present disclosure;

[0034] Figure 12 A schematic diagram illustrating the data flow between a backscatter detector, electronic devices, and a processor according to an embodiment of the present disclosure is shown.

[0035] Figure 13 A schematic diagram of backscatter detection of detector modules at different locations according to an embodiment of the present disclosure is shown;

[0036] Figure 14 The diagram illustrates the backscattered energy spectra of different materials at different locations after peak normalization.

[0037] Figure 15 This schematically illustrates the relative number of backscattered rays from different materials at different locations;

[0038] Figure 16 A schematic diagram illustrating the data flow between a backscatter detector, electronic devices, and a processor according to another embodiment of the present disclosure is shown;

[0039] Figure 17 The diagram schematically illustrates a set of waveforms of a ray signal containing noise.

[0040] Figure 18 The schematic diagram illustrates the backscattering energy spectra of different materials at different locations;

[0041] Figure 19 The diagram schematically illustrates the distribution of ray indices of different materials in a coordinate system according to embodiments of the present disclosure.

[0042] The reference numerals in the above figures are as follows, and different application scenarios correspond to different embodiments:

[0043] 100. Application scenarios; 110. Radiation sources; 120. Backscatter detectors; 121. Sensitive volume; 122. Photoelectric converters; 130. Electronic devices; 140. Target objects; 150. Networks; 160. Electronic components;

[0044] 500. Application Scenarios; 510. Radiation Sources; 520. Backscatter Detectors; 521. Detector Modules; 530. Electronic Equipment; 540. Target Objects; 550. Networks; 560. Electronic Devices;

[0045] 1100 Application scenario; 1110 Radiation source; 1120 Backscatter detector; 1121 Detector module; 1130 Electronic device; 1131 Processor; 1140 Target object; 1150 Network; 1160 Electronic device.

[0046] It should be noted that, for clarity, the dimensions of the overall / partial structure or the overall / partial region in the drawings used to describe the embodiments of this disclosure may be enlarged or reduced, i.e., these drawings are not drawn to actual scale. Detailed Implementation

[0047] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0048] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0049] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0050] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0051] Figure 1 The diagram illustrates an application scenario of a backscatter detection device in the relevant technology.

[0052] When radiation rays enter an object, some of them undergo Compton scattering. During this process, the energy and direction of the radiation rays change. Some of these rays change their direction of flight so much that they return to the side where the radiation source is located. These rays are called backscattered rays, or simply backscattered rays.

[0053] like Figure 1As shown, the application scenario 100 may include a backscatter detection device and a target object 140. The backscatter detection device may include one or more radiation sources 110, one or more backscatter detectors 120, electronic devices 160, and electronic devices 130.

[0054] For example, radiation source 110 is configured to emit radiation rays to scan target object 140; backscatter detector 120 is located on the same side of target object 140 as radiation source 110, and backscatter detector 120 is configured to receive radiation rays reflected by target object 140.

[0055] For example, radiation source 110 may include an X-ray source that emits X-rays to scan target object 140. Backscatter detector 120 can use its sensitive volume to convert the X-rays reflected from target object 140 into photons, and then use its internally encapsulated photoelectric converter 122 to convert the photons into pulsed electrical signals. Target object 140 may include objects such as vehicles, containers, suitcases, or other items in a security screening scenario, or various materials in a materials analysis scenario. Target object 140 may also include human bodies, such as people passing through security checkpoints in stations, airports, or other public places. In some embodiments, radiation source 110 may also include a gamma-ray source or other radiation sources capable of Compton scattering.

[0056] For example, electronic device 160 may include devices such as amplifiers for amplifying the pulsed electrical signal output by backscatter detector 120. Electronic device 130 may include one or more processors and a memory for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors perform data processing on the electronic signal. Radiation source 110, backscatter detector 120, and electronic device 160 may be communicatively connected to electronic device 130 via network 150 to transmit data. Network 150 may include various connection types, such as wired, wireless communication links, or fiber optic cables, etc. Backscatter detector 120 and electronic device 160 may be communicatively connected to transmit pulsed electrical signals.

[0057] For example, combined Figure 1 This section describes the backscatter detection process of the target object 140 in the relevant technology.

[0058] First, the radiation source 110 includes an X-ray source and a fly-spot forming mechanism (not shown in the figure). The X-ray source emits X-rays, which are modulated by the fly-spot forming mechanism to form fly-spots, thereby performing fly-spot scanning on the target object 140.

[0059] Then, the backscattered ray signal (e.g., the backscattered ray signal with a certain energy distribution and time interval distribution) scattered by the target object 140 Figure 2(The sequence of ray events shown in the incident backscatter detector 120) is within the sensitive volume 121 of the incident backscatter detector 120. The sensitive volume 121 of the backscatter detector 120 refers to the region in the detector that can interact with incident radiation particles and generate photon signals, and this region may include a ray-sensitive medium.

[0060] Figure 2 The horizontal axis is the time axis, t 21 t 22 ...t 29 The scale on the horizontal axis represents time units that can be characterized using nanoseconds (ns), microseconds (µs), milliseconds (ms), or seconds (s). Figure 2 The vertical axis is the energy axis, e 21 e 22 ...e 28 The scale on the vertical axis represents energy units such as joules or volts. Figure 2 Each vertical line in the diagram corresponds to a ray event. The horizontal axis coordinate at the bottom of the vertical line represents the incident time point, and the vertical axis coordinate at the top of the vertical line represents the ray energy.

[0061] Next, the sensitive volume 121 of the backscatter detector 120 absorbs the radiation through the radiation-sensitive medium and converts it into a large number of photons (ultraviolet-visible range), producing... Figure 3 A schematic diagram showing the change in the number of photons excited by a single ray (such as a ray event) over time according to an embodiment of the present disclosure.

[0062] Figure 3 The horizontal axis is the time axis, t 31 t 32 ...t 37 The scale on the horizontal axis represents time units that can be characterized using nanoseconds (ns), microseconds (µs), milliseconds (ms), or seconds (s). Figure 3 The vertical axis is the signal axis, I 31 I 32 ...I 36 The scale on the vertical axis can be represented by a current, such as an ampere (A), or a voltage, such as a volt (V). Figure 3 The signal attenuation shown in the figure is close to exponential attenuation.

[0063] Then, in conjunction with the photoelectric converter 122 of the backscatter detector 120, the photon stream is converted into an electronic signal. The response time of the photoelectric converter 122 can be faster than the time of the photon pulse, and the pulse electrical signal corresponding to a single ray it converts is similar to... Figure 3 .

[0064] When the radiation intensity (such as the radiation count rate) is high, the electron signals generated by a series of radiation events will accumulate and superimpose, forming a continuous pulse waveform using the photoelectric converter 122, such as... Figure 4 The related technology shown is a pulse electrical signal with signal stacking and superposition. Figure 4 This shows the pulsed electrical signal output by the backscatter detector 120 when a large amount of radiation is incident, for the purpose of... Figure 2 Multiple cases of radiation exposure and examples of each case, such as Figure 3 The result of convolving the response waveform.

[0065] Figure 4 The horizontal axis is the time axis, t 41 t 42 ...t 49 The scale on the horizontal axis represents time units that can be characterized using nanoseconds (ns), microseconds (µs), milliseconds (ms), or seconds (s). Figure 4 The vertical axis is the signal axis, I 41 I 42 ...I 46 The scale on the vertical axis can be represented by a current, such as an ampere (A), or a voltage, such as a volt (V).

[0066] Then, the electronic signal output by the backscatter detector 120 (such as...) Figure 4 The pulse electrical signal shown can be sampled by the ADC after passing through the amplifier. The sampled signal generates a corresponding digital signal sequence which is then transmitted to the electronic device 130 for processing.

[0067] In related technologies, the sampled values ​​of ADCs include contributions from multiple X-ray signals, losing information from individual X-ray signals. Consequently, accurate information on different X-ray conditions cannot be obtained, and different X-rays under the same conditions cannot be accurately distinguished. The inventors discovered that at least one reason for this is that the detection area (i.e., the detection area of ​​the sensitive volume) corresponding to a single X-ray transmission channel (such as a photoelectric converter channel) of the backscatter detector is too large. For example, an excessively large detection area corresponds to a single photoelectric converter, and this single X-ray transmission channel leads to an excessively high count rate of the processed X-ray signals. Since pulsed electrical signals have a certain width, under high count rate conditions, a large amount of signal accumulation and superposition will occur (e.g., ...). Figure 4 Therefore, it is impossible to distinguish the signal of a single ray.

[0068] For example, consider two different radiation conditions: 1) energy 10 keV (kiloelectron volts) and count rate 2 Mcps (millions of counts per second) and 2) energy 20 keV and count rate 1 Mcps. The photon flux intensity generated after the signals from the two radiation conditions are stacked is the same, so the results obtained after ADC sampling are also the same, making it impossible to distinguish and obtain accurate information about radiation under different conditions.

[0069] Based on the problem of loss of information from individual X-ray signals due to the accumulation and superposition of a large number of signals, this disclosure provides, for example... Figure 5 The backscatter detection device shown can process data based on either an integrating (also known as a current-based) detection principle or a counting (also known as a pulse-based) detection principle.

[0070] Figure 5 The diagram illustrates an application scenario of a backscatter detection device according to an embodiment of the present disclosure. Figure 6 A schematic diagram illustrating the layout of the radiation source and backscatter detector according to an embodiment of the present disclosure is shown.

[0071] like Figure 5 and Figure 6 As shown, application scenario 500 according to this embodiment may include a backscatter detection device and a target object 540. The backscatter detection device may include one or more radiation sources 510, one or more backscatter detectors 520, electronic devices 560, and electronic devices 530.

[0072] In some embodiments, a radiation source 510 is configured to emit radiation rays to scan a target object 540; at least one backscatter detector 520 is distributed on at least one side of the radiation source 510 (e.g., at least one side of the left and right sides), each configured to detect radiation ray signals, including signals detected after the target object 540 has been scanned by radiation rays. For example, at least one backscatter detector 520 is located on the same side of the target object 540 as the radiation source 510, and the backscatter detector 520 is configured to receive radiation rays reflected by the target object 540. The backscatter detector 520 includes a plurality of detector modules 521 arranged at different locations with independent ray signal channels, each ray signal channel including a channel for transmitting the detected radiation ray signals. At least two first detection modules have different detection area areas, each detection area being adapted to a respective target first count rate.

[0073] For example, the radiation source 510, electronic device 530, target object 540, and network 550 in this embodiment can be referred to the description above. Figure 1 The radiation source 510, electronic equipment 530, target object 540, and network 550 will not be described in detail here.

[0074] For example, the backscatter detector 520 can be a counting detector or an integrating detector. Each detector module 521 can receive X-rays reflected from the target object 540, convert them into a photon stream, and then output a pulsed electrical signal to the electronic device 560 via a corresponding X-ray signal channel. Multiple detector modules 521 can be regularly distributed at different locations to form a detector array, such as a single-row array or a multi-row array, or multiple detector modules 521 can be irregularly distributed at different locations. These different locations can be located on the same plane or on different planes, for example, distributed on the same curved surface.

[0075] Each detector module 521 includes a radiation-sensitive medium and a photoelectric conversion device encapsulated in a light-shielded mechanical housing. Each detector module 521 receives X-rays reflected from the target object 540 using its detection area. The detection area may include a region formed by the radiation-sensitive medium. Specifically, the X-rays interact with the radiation-sensitive medium to generate a certain number of photons with specific decay times. The photon stream is absorbed by the photoelectric converter through a collection cavity to generate a pulsed electrical signal. The collection cavity may be implemented by means of optical guides, direct coupling with optical adhesive, etc.

[0076] Photoelectric conversion devices can have signal amplification capabilities (amplifying a single electron into thousands to millions of electrons) to improve the signal-to-noise ratio. For example, a photoelectric conversion device can be a SiPM (silicon photomultiplier tube). The sensitive area size of a SiPM is typically 4mm × 4mm to 6mm × 6mm to ensure sufficient light collection efficiency, and the number of microcells is generally no less than 3000 to ensure that the number of photons generated by high-energy rays (around 200keV) is within the linear response range of the SiPM. Photoelectric conversion devices can also be PMTs (photomultiplier tubes), APDs (avalanche photodiodes), or HMPTs (hybrid photomultiplier tubes), etc.

[0077] The backscatter detector 520 includes multiple X-ray signal channels corresponding to multiple detector modules 521. Each X-ray signal channel can independently detect and record X-ray events and transmit photon signals and pulsed electrical signals. Each X-ray signal channel corresponds to an independent signal transmission channel, which can process the incident X-rays. For example, each detector module 521 has its own independent detection area and photoelectric conversion device.

[0078] For example, the count rate refers to the number of rays recorded per unit time. The detection area of ​​detector module 521 indicates the size of the detection area. A larger detection area results in a higher overall count rate of received radiation rays, and vice versa.

[0079] The target first count rate is used to indicate the maximum number of rays theoretically recorded by detector module 521 per unit time. The target first count rate can be predetermined for each detector module 521. The detection area of ​​detector modules 521 can be the same or different, and the target first count rate of detector modules 521 can also be the same or different. Any two detector modules 521 with different detection area areas can both be referred to as the first detector module 521.

[0080] The detection area of ​​the first detector module 521 being compatible with its target first count rate means that the detection area of ​​the detector module 521 can meet its designed target first count rate requirements, for example, the maximum number of rays that can actually be recorded per unit time will not exceed the target first count rate.

[0081] According to embodiments of this disclosure, multiple detector modules 521 are distributed at different locations, and their X-ray signal channels are independent of each other, enabling the entire detection area of ​​the backscatter detector 520 to be divided into multiple independent detection areas. At least two first detection modules have different detection area areas, and by combining the detection area area of ​​each first detection module with its own X-ray signal channel, they are adapted to their respective target first count rates. Therefore, the detection area corresponding to each X-ray signal channel is appropriate, allowing the reception and processing of X-ray signals at X-ray count rates within the target range. This effectively overcomes the signal accumulation problem caused by excessively high X-ray count rates, thereby enabling the acquisition of accurate information about individual X-rays.

[0082] Furthermore, since the detection areas of at least the two first detection modules are different from each other, the overall number of X-ray signal channels of the backscatter detector 520 can be reduced, thereby reducing the cost and power consumption of photoelectric conversion devices and electronics.

[0083] In some embodiments, the detection area of ​​each first detection module is positively correlated with its distance to the X-ray beam, which includes radiation emitted by the radiation source 510 toward the target object 540.

[0084] For example, at a location close to the X-ray beam emitted by radiation source 510, the ray count rate is high and varies significantly with spatial location. The first detection module at this location can use a smaller detection area to reduce the count rate of a single module and reduce signal stacking. At a location far from the X-ray beam emitted by radiation source 510, the ray count rate is low and does not vary significantly with spatial location. The first detection module at this location can use a larger detection area.

[0085] Figure 6 Each rectangle corresponds to the detection area of ​​detector module 521, and radiation source 510 emits radiation rays from the radiation emission area. For example... Figure 6 Detector modules 521-1 and 521-2, which use different patterns for filling, are both referred to as the first detection module. The distance between detector module 521-1 and the X-ray beam along the first direction is d. 51 The distance between detector module 521-2 and the X-ray beam along the first direction is greater than d. 51 d 52 The detection area of ​​detector module 521-1 is smaller than that of detector module 521-2.

[0086] The distance between the detector area and the X-ray beam along the first direction in this disclosure refers to the distance between the right edge of the detector area along the first direction and the extension line of the X-ray beam emitting area, where the extension line refers to the center line of the X-ray beam emitting area extending along the second direction. Alternatively, d 51 and d 52 It can also be the straight-line distance between the center of the detection area of ​​detector module 521-1 and detector module 521-2 and the center of the beam emission area.

[0087] According to embodiments of this disclosure, the detection area of ​​each first detection module can be reasonably determined by taking into account the distance between the detector module 521 and the X-ray beam, thereby better adapting to their respective target first count rates.

[0088] In some embodiments, the plurality of detection modules further include at least two second detection modules, the detection areas of the at least two second detection modules being the same, and the distance from each of them along the first direction to the X-ray beam being less than or equal to the target threshold.

[0089] For example, in different regions of the X-ray beam emitted by radiation source 510, the ray count rate is inconsistent. Multiple detector modules 521 with the same detection area can be set in the same region, and multiple detector modules 521 with different detection area areas can be set in different regions. Any two detector modules 521 with the same detection area area can both be referred to as the second detection module. It can be understood that the terms "first detection module" and "second detection module" are used to more clearly illustrate the differences in detection area areas; any detection module can be called either the first detection module or the second detection module.

[0090] like Figure 6 As shown in the diagram, from right to left starting with radiation source 510, detector modules 521-1 and 521-3 in the first column are both referred to as the second detection modules. If the target threshold can be d... 51 Detector modules 521-1 and 521-3 are at the same distance from the X-ray beam along the first direction, which is d. 51Furthermore, the detector modules 521 in each column are at the same distance from the X-ray beam along the first direction, and can be set with the same target threshold. Each column is considered as a region, and the multiple detector modules 521 in it can have the same detection area.

[0091] According to embodiments of this disclosure, multiple second detection modules having the same detection area are provided, which can provide consistent detection performance and detection reliability when detecting radiation in the same area.

[0092] In some embodiments, at least two first detection modules are distributed along a first direction, and at least two second detection modules are distributed along a second direction intersecting the first direction (e.g., ...). Figure 6 Distribution in the y-direction.

[0093] like Figure 6 As shown, detector modules 521-1 and 521-2 are distributed along a first direction, and detector modules 521-3 are distributed along a second direction. The first direction is perpendicular to the second direction. This allows for the targeted arrangement of detector modules, taking into account different count rates near the X-ray beam.

[0094] Figure 7 A schematic diagram illustrating the layout of a radiation source 510 and a backscatter detector 520 according to another embodiment of the present disclosure is shown.

[0095] In some embodiments, two identical backscatter detectors 520 may be symmetrically arranged on both sides (e.g., the left and right sides) of the radiation source 510. For example... Figure 7 As shown, the two backscatter detectors 520 can have symmetrical and identical detector module 521 structures. The backscatter detector structure includes the detection area of ​​each of the multiple detector modules. For example, two detector modules 521 that are identical to the radiation source 510 on both the left and right sides can have the same detection area.

[0096] According to embodiments of this disclosure, by symmetrically arranging two identical backscatter detectors 520 on both sides of the radiation source 510, richer backscatter data can be detected, thereby improving detection accuracy.

[0097] Figure 8 A schematic diagram of the layout of a radiation source 510 and a backscatter detector 520 according to another embodiment of the present disclosure is shown. Figure 8 Each rectangle in the diagram can correspond to the detection area of ​​detector module 521.

[0098] In some embodiments, backscatter detectors 520 may be disposed on both sides or more sides of the radiation source 510. The distance between the backscatter detectors 520 on either side and the radiation source 510 may be the same or different, and the detector module 521 structure of the backscatter detectors 520 on either side may be the same or different. The distance between the backscatter detectors 520 on each side and the radiation source 510, as well as the structure of the detector module 521, may be determined based on a specific region on the target object 540 being detected. For example, different regions on the target object 540 may have different structures and materials, and different Compton scattering distributions; therefore, the structure of the corresponding backscatter detector 520 may be determined based on the characteristics of each region.

[0099] like Figure 8 As shown, two backscatter detectors 520 are arranged on both sides of the radiation source 510. The detector modules 521 of the two backscatter detectors 520 have different structures, and each detects radiation signals from different regions of the corresponding target object. For example, the number and arrangement of the multiple detector modules 521 are different, and the shape, size and area of ​​the detection area of ​​the detector modules 521 are not completely the same.

[0100] According to embodiments of this disclosure, the backscatter detectors 520 on each side are able to detect specific areas on the target object 540, thereby improving detection accuracy.

[0101] In some embodiments, the detection area of ​​at least one of the plurality of detector modules 521 of the backscatter detector 520 is adjustable. For example, the detection area of ​​the first detector module 521, the second detector module 521, or other detector modules 521 is adjustable. For instance, each detector module 521 is configured with a retractable shielding window by means of mechanical adjustment. The material of the shielding window can shield radiation, and the size of the detection area in which each detector module 521 can receive radiation signals is adjusted by changing the size of the window.

[0102] According to embodiments of this disclosure, the adjustability of the detection area enables the detector module 521 to adapt to different target objects 540, different counting rates, and different locations, thus providing greater flexibility.

[0103] In some embodiments, the detection area of ​​each detector module 521 in at least one detector module 521 is adjusted according to the difference between the detected actual count rate and the target first count rate.

[0104] For example, if the actual count rate is lower than the target first count rate by a certain value, such as a difference of more than 20%, the count rate can be increased by increasing the area of ​​the detection region; conversely, the count rate can be decreased to avoid stacking. This can improve the accuracy and efficiency of the detected data. Within a certain range, the target first count rate can be maintained even when the area of ​​the detection region changes.

[0105] In some embodiments, such as Figure 8 The two backscatter detectors 520 shown are distributed on both sides of the radiation source 510. The structure of each backscatter detector 520 is determined according to the region of the target object 540 being detected.

[0106] For example, if one side of the target object 540 experiences more Compton scattering, resulting in a higher count rate on that side, the detection area of ​​the detector module 521 corresponding to that side can be adjusted to be smaller. Conversely, if the other side experiences less Compton scattering, resulting in a lower count rate, the detection area of ​​the detector module 521 corresponding to that side can be increased. This allows for more effective adaptation to detection needs at different locations.

[0107] It should be noted that the arrangement of the plurality of detector modules 521 in the backscatter detector 520 of this embodiment, as well as the shape and detection area of ​​each detector module 521, are not limited to... Figure 6 , Figure 7 and Figure 8 As shown, the invention can be flexibly adjusted within the scope of the present invention concept.

[0108] In some embodiments, the detection area of ​​each detector module 521 is predetermined based on the target second count rate per unit area and the target pulse width of a single ray signal.

[0109] The second target count rate indicates the maximum number of rays recorded per unit area of ​​the detection region per unit time. Unlike the second target count rate, the first target count rate is the maximum number of rays recorded per unit time for the entire detection region. For example, a unit area of ​​one square centimeter and a unit time of one second are used as an example.

[0110] A single ray signal is obtained from a single ray event, for example... Figure 3 The pulse waveform is shown. The target pulse width is used to indicate the pulse width of a single ray signal's pulse waveform when no signal buildup occurs. Different detector modules 521 may have the same or different target second count rates.

[0111] It is understandable that the number of rays recorded per unit area per unit time in the detection area affects the ray count of the entire detection area, while the pulse width of a single ray signal affects whether the pulse waveforms of multiple ray signals are stacked.

[0112] According to embodiments of this disclosure, a suitable detection area can be determined based on the target second count rate per unit area and the target pulse width of a single ray signal, effectively preventing signal accumulation and superposition.

[0113] The decay time and afterglow effect of the X-ray sensitive medium affect the pulse width of a single X-ray signal. For example, some existing technologies use materials with long decay times, such as CsI, GOS, and BaFCl, as X-ray sensitive media, which results in a larger signal pulse width (e.g., ...). Figure 3 As shown in the figure, signal accumulation and superposition are also prone to occur; in addition, materials such as CsI have a more obvious afterglow effect, that is, the first incident X-ray signal will continue to generate photon signals, which in turn affects the discrimination of the later incident X-ray signal.

[0114] In some embodiments, the detection region of each detector module 521 includes a radiation-sensitive medium configured to interact with radiation rays reflected by the target object 540 to generate radiation photons; wherein the decay time of the radiation photons is less than or equal to a first target time, and / or the duration of the afterglow effect is less than or equal to a second target time.

[0115] After receiving radiation, such as Figure 3 The photons generated by the X-ray sensitive medium shown will decay in two steps. The first step is a rapid decay from the peak output to a lower value. This process is called decay. At this value, the decay gradient has essentially shifted to a lower decay rate. The second step is a continued decay at this lower decay rate. This low-intensity decay is generally a long decay period, during which the decaying emission is called afterglow. For example, it can be defined as 1% to 2% below the peak value (for example only). For instance, the initial rapid decay time is called the decay time, for example, from the peak to 1 / e of its peak value. The natural constant e is the base of the natural logarithm. In the embodiments of this disclosure, the duration of the afterglow effect can be calculated based on the time from the peak to 1000 ppm (0.1% to 0.2%).

[0116] For example, the first target time and the second target time are used to prevent multiple X-ray signals from accumulating and overlapping. For instance, this can be achieved by testing various X-ray sensitive media materials, selecting materials with short decay times and minimal afterglow effects to evaluate whether they can prevent the accumulation and overlapping of multiple X-ray signals. For example, the first target time could be 200 nanoseconds, and the second target time could be 10 milliseconds; this is merely an example.

[0117] Figure 9 A schematic diagram illustrating a comparison of the response pulse waveforms of a fast-attenuating crystal (GAGG) and a slow-attenuating crystal (GOS) according to embodiments of the present disclosure is shown.

[0118] Figure 9 The horizontal axis is the time axis, t 91 t 92 ...t 97 The scale on the horizontal axis represents time units that can be characterized using nanoseconds (ns), microseconds (µs), milliseconds (ms), or seconds (s). Figure 9 The vertical axis is the signal axis, I 91 I 92 ...I 96 The scale represents the vertical axis, and its amplitude unit can be expressed in current, such as ampere (A), or in voltage, such as volt (V). GAGG stands for gadolinium aluminum gallium garnet, and GOS stands for gadolinium oxysulfide crystal.

[0119] like Figure 9 As shown, the response pulse waveform of GAGG has a shorter decay time and a smaller afterglow effect compared to the response pulse waveform of GOS. Based on its definition of the first and second target times, it can constrain multiple X-ray signals from signal accumulation and superposition. Therefore, GAGG can be selected as a material for X-ray sensitive media.

[0120] It should be noted that in some embodiments, fast-decaying crystals such as BGO (bismuth germanate), LYSO (yttrium lutetium silicate), or plastic scintillators can also be selected as materials for the radiation-sensitive medium, and this disclosure is not limited thereto.

[0121] In some embodiments, the target second count rate per unit area of ​​each detector module 521 is predetermined based on its relative position to the X-ray beam. For example, the target second count rate is predetermined based on its distance from the X-ray beam and its location in different orientations of the X-ray beam.

[0122] In some embodiments, the target second count rate per unit area of ​​each detector module 521 is negatively correlated with its distance along the first direction to the X-ray beam.

[0123] For example, at locations near the X-ray beam emitted by radiation source 510, the ray count rate is higher, and the target second count rate per unit area of ​​detector module 521 can be higher at these locations; conversely, at locations farther from the X-ray beam emitted by radiation source 510, the ray count rate is lower, and the target second count rate per unit area of ​​detector module 521 can be lower at these locations; (Refer to...) Figure 7 The farther the detector module 521 is from the radiation source 510 along the first direction, the lower the second count rate of the target per unit area, and vice versa. This ensures that the distribution of the second count rate of the target is consistent with the actual detection environment, improving detection accuracy.

[0124] In some embodiments, the detection area of ​​each detector module 521 is predetermined based on the target second count rate per unit area and the target pulse width of a single ray signal, including: multiplying the target second count rate per unit area of ​​each detector module 521 and the target pulse width of a single ray signal to obtain a first value; and determining the detection area based on the reciprocal of the first value.

[0125] The following is a derivation of the calculation process for the area S of the detection region.

[0126] The count rate (i.e., the first count rate of the target) of a single ray signal channel of each detector module 521 satisfies Formula 1:

[0127] Formula 1

[0128] in, The first count rate is the target value, and w is the target pulse width of a single ray signal, for example, the minimum pulse width allowed to prevent signal stacking. 1 represents 1 second.

[0129] The first target count rate is the second target count rate per unit area, r. unit The product of the area S of the detection region:

[0130] Formula 2

[0131] Solve equations 1 and 2 simultaneously to eliminate get:

[0132] Formula 3

[0133] in, The first value is given, and the area S of the detection region is less than or equal to the reciprocal of the first value.

[0134] In some embodiments, determining the detection area based on the reciprocal of the first value includes multiplying the reciprocal of the first value by a safety factor to determine the detection area, wherein the safety factor is less than 1. The safety factor values ​​for different detector modules 521 can be the same or different, thereby allowing for targeted adjustment of the counting rate of the detector module 521.

[0135] Based on Formula 3, by introducing a safety factor, we obtain:

[0136] Formula 4

[0137] Where k is the insurance weight, and the reciprocal of k is the insurance coefficient. For example, the value of k is greater than or equal to 2, and less than or equal to 10.

[0138] Figure 10 The diagram illustrates a waveform of a pulsed electrical signal output by a detector module according to an embodiment of the present disclosure.

[0139] Figure 10 The horizontal axis is the time axis, t 101 t 102 ...t 109 The scale on the horizontal axis represents time units that can be characterized using nanoseconds (ns), microseconds (µs), milliseconds (ms), or seconds (s). Figure 10 The vertical axis is the signal axis, I 101 I 102 ...I 106 The scale on the vertical axis can be represented by a current, such as an ampere (A), or a voltage, such as a volt (V).

[0140] Referring to Formula 4, for example, the target second count rate per unit area. 10 kcps / cm 2 If the target pulse width w of a single X-ray signal is 1 μs, then the detection area S is 100 cm². 2 ,like Figure 10 Most of the pulse signals did not accumulate.

[0141] According to embodiments of this disclosure, by introducing a safety factor, the size of the detection area can be controlled, and the ray count rate of a single ray signal channel can be further controlled to avoid signal accumulation and superposition.

[0142] When scanning one or more points on a target object, transmitted or scattered rays from the same scanning point are detected at multiple locations by the radiation-sensitive medium of the backscatter detector. Currently, the sum of the detection data from each location is simply used as the radiation signal for the same scanning point. A radiation image is obtained based on the radiation signal obtained from the summation result, and material identification results are then obtained from the radiation image.

[0143] The radiation signal is obtained by summing the detection data, and then the radiation image is obtained by processing the radiation signal. However, some information is lost, which is not conducive to improving the accuracy of material identification.

[0144] Figure 11 The illustration shows an application scenario diagram of a material identification device according to an embodiment of the present disclosure. Figure 12 The diagram illustrates the data flow between a backscatter detector, electronic devices, and a processor according to an embodiment of the present disclosure.

[0145] It should be noted that in embodiments of the material identification device or method, a radiation detector comprising multiple detector modules can be used. This radiation detector can be positioned on the same side of the target object as a backscatter detector, or it can be positioned on opposite sides of the target object as a transmission detector. It is understood that when the radiation detector is used as a backscatter detector, it can have a structure, size, detection parameters, etc., adapted to the backscatter scanning scenario. Similarly, when the radiation detector is used as a transmission detector, it can have a structure, detection parameters, etc., adapted to the transmission scanning scenario.

[0146] The following example illustrates that the radiation detector is preferably a backscatter detector.

[0147] like Figure 11 As shown, application scenario 1100 according to this embodiment may include a backscatter detection device and a target object 1140. The backscatter detection device may include one or more radiation sources 1110, one or more backscatter detectors 1120, electronic devices 1160, and electronic devices 1130.

[0148] For example, the radiation source 1110, electronic device 1130, target object 1140, and network 1150 in this embodiment can be referred to the description above. Figure 1 The radiation source 1110, electronic equipment 1130, target object 1140, and network 1150 will not be described in detail here.

[0149] In some embodiments, the backscatter detector 1120 may be the backscatter detector 520 described above, and one or more embodiments of the backscatter detector 520 described above may be applied to the backscatter detector 1120. For example, at locations near the X-ray beam emitted by the radiation source 510, the ray count rate is high and varies significantly with spatial location; the detection module at this location can use a smaller detection area. At locations far from the X-ray beam emitted by the radiation source 510, the ray count rate is low and does not vary significantly with spatial location; the first detection module at this location can use a larger detection area. Thus, while reducing the number of ray signal channels, it is also possible to obtain accurate spatial distribution information of ray indicators.

[0150] In other embodiments, the backscatter detector 1120 is not limited to the backscatter detector 520 described above. For example, it may include multiple detector modules 1121 arranged in different positions, wherein the detection area of ​​each detector module 1121 may be the same or different, and the X-ray signal channels of each detector module 1121 may be independent or multiplexed. This embodiment does not impose specific limitations, as long as the position of each detector can be identified.

[0151] In some embodiments, the backscatter detector 1120 is used to detect radiation signals using multiple detector modules 1121 in response to a radiation ray scanning target object 1140. The multiple detector modules 1121 are arranged at different positions and the ray signal channels are independent of each other.

[0152] Reference Figure 11 and Figure 12 The processor 1131 is configured to perform operations S1201 to S1202. Figure 12 The dashed line is used to represent the corresponding positional relationship.

[0153] In operation S1201, based on the radiation signal detected by each detector module 1121, N ray indicators corresponding to the location of each detector module 1121 are calculated, where N is an integer greater than or equal to 1; in operation S1202, based on the indicator value of each ray indicator at different locations, the material of the target object is identified.

[0154] In backscattered X-ray events, the energy and time interval between events follow a certain statistical distribution. When the same X-ray beam is incident on objects with different properties (material composition, areal density, etc.), the statistical distribution characteristics of the backscattered X-rays will change, which is reflected in the following three aspects:

[0155] 1) Quantity: Lighter materials or materials with higher surface density have a higher probability of backscattering. 2) Energy: Different materials have different backscattering energy spectrum distributions, which are related to surface density. 3) Angular distribution: Backscattering from different directions has different quantity and energy distributions.

[0156] The basic principle of backscatter detection technology is to use a backscatter detector to measure the values ​​and changes of the above three statistical characteristics or their combinations, and then infer the material information and changes of the target object. The signal characteristics corresponding to the above three statistical characteristics within the detector are as follows:

[0157] 1) Count rate, reflecting the number of backscattered rays. 2) Pulse height, reflecting the energy of the backscattered rays. 3) Detector spatial position, reflecting the angular distribution information of the backscattered rays.

[0158] Figure 13 The diagram illustrates a backscatter detection schematic of detector modules at different locations according to embodiments of the present disclosure.

[0159] Combination Figure 13 For example, the statistical characteristics of backscattering produced by two common test objects, an iron plate (hereinafter referred to as Fe, 5 mm thick, representing heavy materials such as metals) and a polyethylene block (hereinafter referred to as PE, 10 cm thick, representing light materials such as plastics), are compared when irradiated by a 200 kVp X-ray machine. Detector module 1121 may include detector module P1 and detector module P2. In Figure 13, detector module P1 represents the detector pixel closer to the X-ray beam, and detector module P2 represents the detector pixel farther away.

[0160] Figure 14 The diagram illustrates the backscattered energy spectra of different materials at different locations after peak normalization. Figure 14 The horizontal axis is the energy axis, e 141 e 142 ...e 149 This represents the scale on the horizontal axis; the energy unit can be keV.

[0161] Reference Figure 14 Regarding energy information, the peak energy spectrum of Fe is tens of keV higher than that of PE; and for energy spectra at different locations, the peak energy spectrum at detector module P2 (far from the X-ray beam) is even higher.

[0162] Figure 15 The illustration shows the relative number of backscattered rays at different locations from different materials. Figure 15 The vertical axis is the quantity axis, n 151 n 152 ...n 159 This represents the scale on the vertical axis.

[0163] Reference Figure 15 Regarding the number of rays, at the same detection location, the relative number of rays in PE is greater than that in Fe; however, for the relative number of rays at different locations, the relative number of rays at P1 (closer to the X-ray beam) is greater.

[0164] Combination Figures 11-15 In operation S1201, processor 1131 can calculate N ray indicators at the location of each detector module 1121 based on the count rate characteristics and pulse height characteristics detected by each detector module 1121. In operation S1202, N ray indicators can be obtained at each location, thereby identifying the material of the target object 1140 through the spatial distribution of each indicator.

[0165] Therefore, by improving the ability to distinguish the energy, count rate, and position of rays, material identification and a better signal-to-noise ratio can be achieved.

[0166] According to embodiments of this disclosure, the signals generated by detector modules at different locations in a backscatter detector differ, and additional information can be obtained by comparing these differences. Multiple detector modules 1121 distributed at different locations receive radiation rays reflected from the target object 1140 using their respective radiation signal channels. By receiving the radiation rays reflected by the target object 1140 through each detector module 1121, one or more radiation indices corresponding to each location can be calculated independently. By analyzing the spatial distribution differences of the index values ​​of each radiation index at different locations, the material of the target object 1140 can be accurately identified.

[0167] Compared to methods that use backscattered images to identify materials, identifying materials by the spatial distribution differences of each ray indicator at different locations provides a different dimension of identification, serving as an effective supplement to backscattered image recognition. It also achieves high accuracy and efficiency when using the spatial distribution of ray indicators independently to identify materials.

[0168] Figure 16 The diagram illustrates a data flow between a backscatter detector, electronic devices, and a processor according to another embodiment of the present disclosure.

[0169] like Figure 16 As shown, the electronic devices include an amplifier, a threshold comparator, a counter, and a channel encoder. In some embodiments, the threshold comparator is used to determine the energy threshold of multiple sets of radiation signals to filter out radiation signals of different energy ranges from each set of radiation signals, wherein each set of radiation signals is obtained based on the radiation received by the corresponding detector module 1121; the counter is communicatively connected to the processor 1131 and is used to obtain the number of radiation signals of different energy ranges in each set of radiation signals.

[0170] It is understandable that different energy ranges refer to multiple energy ranges, and the threshold comparator is used to filter out complete or partial X-ray signals from these energy ranges. When filtering partial X-ray signals, it means that the unselected remaining parts of each group of X-ray signals do not fall within any energy range set by the threshold comparator.

[0171] Under normal circumstances, the pulse electrical signal directly output by the photoelectric conversion device is difficult to transmit directly to the remote processor 1131 for further processing. Therefore, near the output of the photoelectric conversion device, an amplifier amplifies the signal before transmitting it to the remote processor 1131, thereby improving the signal-to-noise ratio after transmission. The signal attenuation time of the amplifier can be slightly less than, or comparable to, the attenuation time of the radiation-sensitive medium (e.g., 200 ns to 1 μs). This is because an excessively short attenuation time will result in insufficient signal-to-noise ratio of the amplified signal, while an excessively long attenuation time will cause severe signal buildup, exceeding the normal operating range of subsequent signal processing circuits.

[0172] The threshold comparator is used to receive the amplified pulse electrical signal. The threshold comparator determines the energy of the signal and generates a corresponding trigger signal. The counter obtains the energy and count rate information of the ray by recording the number of trigger signals per unit time. Combined with the channel code containing position information, the data is packaged and transmitted to the processor 1131 for data analysis.

[0173] Reference Figure 16 The threshold comparator can include a high-energy threshold comparator and a low-energy threshold comparator, which are connected to the high-energy counter and the low-energy counter, respectively. The function of the threshold comparator is to achieve pulse energy discrimination, that is, to filter out X-ray signals from different energy ranges.

[0174] In related technologies, the signal output by the detector's photoelectric conversion device is a stacked signal, and the amplitude of the signal is generally sampled directly using an ADC (analog-to-digital converter). This method is relatively simple and mature, but the amplitude fluctuates significantly when the count rate and radiation energy are low, resulting in a poor signal-to-noise ratio.

[0175] In this embodiment, for example, for an X-ray machine with an energy level of approximately 200 kVp, two energy ranges can be set. A high-energy threshold comparator filters X-ray signals from the high-energy range, and a low-energy threshold comparator filters X-ray signals from the low-energy range. The low-energy range is used to eliminate background and interference signals caused by noise from the photoelectric conversion device to improve the signal-to-noise ratio; for example, it can be set to 5 keV to 10 keV (corresponding to voltage levels). The high-energy range is used to filter high-energy X-ray signals and can be set to 70 keV to 100 keV.

[0176] When a ray signal passes through the threshold comparator, a specific waveform is generated as a trigger signal for counting. For example... Figure 17 The diagram schematically illustrates a set of X-ray signals containing noise, showing multiple low-energy X-ray events and multiple high-energy X-ray events within the signal waveforms.

[0177] Figure 17 The horizontal axis is the time axis, t 171 t 172 ...t 179 The scale on the horizontal axis represents time units that can be characterized using nanoseconds (ns), microseconds (µs), milliseconds (ms), or seconds (s). Figure 17 The vertical axis is the signal axis, V 171 V 172 ...V 177 The scale on the vertical axis can be represented by voltage, such as volt (V), or current, such as ampere (A). Figure 17 The two dashed lines at the intermediate level represent the low threshold and the high threshold, respectively, and are used to divide the low energy range and the high energy range. For example, 5keV is the low threshold and 70keV is the high threshold.

[0178] Figure 18 The diagram illustrates the backscattered energy spectra of different materials at different locations. Figure 18 The pulse waveform shown is unnormalized and includes both energy spectrum and count rate information. For example... Figure 18 Choosing an appropriate energy range can distinguish between high and low energy components in the energy spectra of Fe and PE.

[0179] Figure 18 The horizontal axis is the energy axis, e 181 e 182 ...e 189 The scale on the horizontal axis represents energy units such as joules or volts. Figure 18 The vertical axis is the quantity axis, n 181 n 182 ...n 189 This represents the scale on the vertical axis. Figure 18 The two vertical dashed lines represent the low threshold and the high threshold, respectively.

[0180] It should be noted that threshold comparators are not limited to high-energy and low-energy threshold comparators; one or more threshold comparators can be configured. Similarly, one or more counters can also be configured.

[0181] For example, refer to Figure 16The electronic device may also include at least one of a low-pass filter, a shaping amplifier, and a time discriminator. For example, a low-pass filter (e.g., bandwidth 10MHz to 100MHz) is added before the high-energy threshold comparator and the low-energy threshold comparator to suppress interference signals and single-photon or crosstalk signals; a shaping amplifier is added before the high-energy threshold comparator and the low-energy threshold comparator to reduce the pulse width, thereby increasing the upper limit of the count rate; a hold time discriminator is added between each pair of threshold comparators and the counter, that is, only signals that have passed through the threshold comparator and been held for a certain duration can be sent to the counter, thereby eliminating false cases caused by fluctuations during signal attenuation.

[0182] In some implementations, the processor 1131 is also configured to assign a corresponding location identifier based on the location of each detector module 1121; wherein, N ray indicators corresponding to the location of each detector module 1121 are bound to the location identifier of the detector module 1121, for example, the binding operation is performed by the processor 1131.

[0183] For example, the channel encoder is used to generate a unique channel code for each detector module 1121, which can map the position of the detector module 1121, i.e., the spatial distribution information of the rays. The processor 1131 can assign a corresponding position identifier based on the channel code of each detector module 1121, such as... Figure 18 As shown, position identifier_1, position identifier_2...position identifier_N-1 and position identifier_N each have a corresponding detector module 1121.

[0184] For example, a channel encoder may include a multi-channel data acquisition card. The multi-channel data acquisition card can be used to acquire signals from multiple channels simultaneously. The front end of each channel is connected to the photoelectric converter of each detector module 1121, and the rear end of each channel is connected to an amplifier, forming a radiation signal channel for each detector module 1121 to transmit pulsed electrical signals.

[0185] According to embodiments of this disclosure, binding location identifiers to ray indicators at various locations can help track and associate the output data of detector module 1121, which is beneficial for accurately obtaining the spatial distribution of ray indicators and for material identification based on the spatial distribution of ray indicators.

[0186] In some embodiments, calculating the N radiation indicators corresponding to the location of each detector module 1121 in operation S1201 includes: for each group of radiation signals, obtaining the number of targets of radiation signals under the target energy range in different energy ranges; calculating the proportion of the number of targets to the total number of radiation signals to obtain the first radiation indicator, wherein the total number of radiation signals is obtained based on the sum of the number of all radiation signals under different energy ranges.

[0187] For example, if the target energy range is high energy, the total number of ray signals is the sum of the high-energy count (i.e., the number of targets) in the high-energy range and the low-energy count in the low-energy range. The first ray index can be the proportion of high-energy counts, as shown in Formula 5 below:

[0188] Formula 5

[0189] Where NLE stands for low-energy count (corresponding to...) Figure 18 The area between the two dashed lines), NHE is the high-energy count (corresponding to...). Figure 18 The area of ​​the right half of the dashed line on the right side of the spectrum), ER represents the proportion of high-energy counts. A high ER indicates a greater proportion of high-energy components in the energy spectrum (higher average ray energy), and vice versa.

[0190] In some embodiments, calculating the N radiation indicators corresponding to the location of each detector module 1121 in operation S1201 includes: for each group of radiation signals, calculating the ratio of the total number of radiation signals to the counting period of the counter to obtain the second radiation indicator, wherein the total number of radiation signals is obtained based on the sum of the number of all radiation signals under different energy ranges, and the counting period includes the period for acquiring the number of radiation signals.

[0191] The second ray indicator can be the ray count rate, as shown in Formula 6 below:

[0192] Formula 6

[0193] Where CR represents the ray count rate, N HE For high-energy counting, N LE For low-energy counting, T is the counter's counting period. The total number of X-ray signals is the sum of the high-energy counts and the low-energy counts.

[0194] It should be noted that the energy range can be flexibly set according to requirements, therefore the calculation methods for the first and second ray indices are not limited to formulas 5 and 6 above. Furthermore, the N ray indices disclosed herein are not limited to the first and second ray indices, but may include other ray indices, such as scattering angle, detection efficiency, attenuation coefficient, etc.

[0195] In some embodiments, identifying the material of the target object 1140 in operation S1202 based on the index values ​​of each ray index at different positions includes: mapping the index values ​​of the first ray index and the second ray index at different positions onto a coordinate system, wherein the vertical axis of the coordinate system corresponds to the first ray index and the horizontal axis of the coordinate system corresponds to the second ray index; and identifying the material of the target object 1140 based on the distribution of the first ray index and the second ray index in the coordinate system.

[0196] In some embodiments, the radiation source 1110 of the backscatter detection device is configured to perform a flying-spot scan on the target object 1140, wherein calculating the N ray indicators corresponding to the location of each detector module 1121 includes: for each ray indicator, multiple indicator values ​​corresponding to the location of each detector module 1121, wherein the multiple indicator values ​​correspond one-to-one with the multiple point locations of the flying-spot scan.

[0197] Figure 19 The diagram schematically illustrates the distribution of ray indices of different materials in a coordinate system according to embodiments of the present disclosure. Figure 19 The vertical axis represents the percentage of high-energy counts (ER), p 191 p 192 ...p 196 The vertical axis represents the scale, and the unit can be a percentage. The horizontal axis represents the ray count rate (CR), c. 191 c 192 ...c 196 It is the horizontal axis scale, and the unit can be counts per second (cps).

[0198] Taking the various ray indices of Fe detected at position P1 as an example, their... Figure 19 The markers in the diagram are "○". Each "○" corresponds to a point position on the target object being scanned. The vertical axis coordinate of each "○" is the index value of the first ray indicator, and the horizontal axis coordinate is the index value of the second ray indicator. That is, each "○" can fuse information from multiple ray indicators. All "○" represent all the first ray indicators and all the second ray indicators corresponding to the location of detector module P1. The same applies to Fe at the location of detector module P2, PE at the location of detector module P1, and Fe at the location of detector module P2, which will not be elaborated further here.

[0199] like Figure 19 The first and second ray indices of different materials have different spatial distributions. For example, the ray indices of Fe detected at detector module P1 (see mark "○") and the ray indices of PE detected at detector module P1 (see mark "□") are two clusters of marks distributed at different positions in the coordinate system. Similarly, the ray indices of Fe detected at detector module P1 (see mark "○") and the ray indices of Fe detected at detector module P2 (see mark "●") are two clusters of marks distributed at different positions in the coordinate system. Through preliminary experimental testing, the above information of the test objects of different materials and volumes can be stored as feature data in the database. During equipment operation, appropriate algorithms (table lookup, fitting, pattern matching, neural networks, etc.) can be used to find the material information that is closest to the actual data, thereby realizing the ability of material identification.

[0200] For example, forming as Figure 19The image shown is input into a pre-trained neural network model, which outputs a predicted material. The neural network model can be trained using test samples of different materials and volumes; each test sample includes similar... Figure 19 The image shown and the material label.

[0201] According to embodiments of this disclosure, by mapping to a coordinate system, the spatial distribution of each ray index can be clearly reflected, providing more information to distinguish different materials.

[0202] It should be noted that this disclosure is not limited to Figure 19 The two-dimensional coordinate system shown can be mapped to a more dimensional coordinate system, for example, when calculating more ray indices.

[0203] In some embodiments, in operation S1202, the index values ​​of each ray index at different locations are matched with the index information of different materials, wherein the index information of different materials includes the index values ​​at different locations calculated in advance; and the material of the target object 1140 is identified based on the matching results.

[0204] For example, the index information of different materials includes pre-utilization such as Figure 11 The backscattering detector shown detects various materials, obtaining a set of index values. The index value of each ray index at different locations can be obtained experimentally or by calculation, for example, multiple index values ​​at the same location. Matching refers to the process of comparing the index value of each ray index at different locations with known index information of the material.

[0205] For example, it is possible to obtain Figure 19 The image shown contains relevant markers for Fe, which are then matched with images pre-mapped to the same coordinate system for each material in the database, for example, by calculating similarity. Alternatively, the difference in index values ​​for the same ray at the same location can be directly compared.

[0206] According to embodiments of this disclosure, the accuracy of material identification is improved by matching the actual value of the radiation index with the index information of different materials in a pre-calculated database.

[0207] In some embodiments, during the material identification process, combined with Figure 11 and refer to Figure 7 and Figure 8The radiation source 1110 emits radiation rays, and two backscatter detectors 1120 are set on both sides of the radiation source 1110. The detection of radiation ray signals by multiple detector modules 1121 of the backscatter detectors 1120 includes: detecting radiation ray signals by multiple detector modules 1121 of each of the two backscatter detectors 1120.

[0208] According to embodiments of this disclosure, using two backscatter detectors 1120 can detect more radiation signals and obtain more information for material identification. For example, not only do the radiation signals detected by detector modules 1121 at different positions on the same backscatter detector 1120 have different distributions, but there are also differences in the distribution of radiation signals between the two backscatter detectors 1120.

[0209] In some embodiments, the two backscatter detectors 1120 distributed on both sides of the radiation source 1110 may have the same or different structures, and each detects radiation signals from different regions of the corresponding target object 1140. In the case of different structures, the structure of each backscatter detector 1120 is determined according to the region of the target object 1140 being detected, and the detector structure includes the detection area of ​​each of the multiple detector modules 1121.

[0210] For example, different regions on the target object 1140 have different structures and materials, and the Compton scattering distribution is also different. Therefore, the structure of the corresponding backscatter detector 1120 can be determined according to the characteristics of each region. For example, the number and arrangement of multiple detector modules 1121 are different, and the shape, size and area of ​​the detection area of ​​the detector module 1121 are not completely consistent.

[0211] According to embodiments of this disclosure, the backscatter detectors 1120 on each side are able to detect specific areas on the target object 1140, thereby improving detection accuracy and material identification accuracy.

[0212] In some embodiments, before matching the index value of each ray index at different locations with the index information of different materials, the method further includes: determining the index information of the material to be matched based on the structure of each of the two backscatter detectors 1120; wherein the index information of the material to be matched is calculated based on the radiation ray signal of the material to be matched detected by the two preset backscatter detectors, and the two preset backscatter detectors and the two backscatter detectors 1120 have a one-to-one correspondence and approximately the same structure.

[0213] It is understandable that the detector area of ​​each detector module 1121 is adapted to the target's first count rate to a certain extent, thereby avoiding stacking, achieving a better signal-to-noise ratio, more accurate detection, and more accurate calculated ray index values. Therefore, the different structures of the backscatter detector 1120 will affect the calculation results of the ray index at the same scanning point to some extent.

[0214] For example, various materials can be identified in advance through simulation experiments. Two pre-set backscatter detectors can be set on both sides of a pre-set radiation source, and the optimal structure of each pre-set backscatter detector can be determined according to the characteristics of different regions of the target material. Then, steps such as radiation scanning, radiation detection, and ray index calculation are performed. Based on the accurate identification of the target material according to the distribution of ray index, relevant information (such as ray parameters, ray index, detector structure, etc.) is stored in a database. Taking the detector structure as an example, each detector module in each pre-set detector has a corresponding position code. The position code is stored in a mapping manner to the detector area and bound to the identified material.

[0215] It should be noted that the materials involved in this disclosure may include raw materials or items of the same type as the target object. For example, if the target object is a specific model of luggage from brand A, then "materials" may include that specific model of luggage from brand A.

[0216] During the scanning of target object 1140, the detection area of ​​each detector module 1121 in each backscatter detector 1120 is adjusted according to the difference between the detected actual count rate and the target's first count rate. After adjustment, steps such as radiation scanning, radiation detection, and ray index calculation are performed. Then, the mapping relationship between the position code of each detector module of each backscatter detector 1120 and the detector area is obtained, and one or more materials with the same or similar mapping relationship are retrieved from the database. Then, the index value of each ray index at different locations is matched with the index information of the retrieved materials.

[0217] For example, having roughly the same detector structure can mean that the difference in the area of ​​a certain number of detector regions with the same location encoding is within a certain range.

[0218] According to embodiments of this disclosure, a multi-stage identification method that first screens detector structures and then performs index matching can reduce the workload of matching and improve the accuracy of material identification.

[0219] In some embodiments, a radiation detection method is also provided, the method comprising: causing a radiation source to emit radiation rays to scan a target object, and causing each of at least one backscatter detector to detect radiation ray signals, the radiation ray signals including signals detected after the target object has been scanned by radiation rays.

[0220] It should be noted that for any parts of the radiation detection method not mentioned in this embodiment, please refer to the above. Figures 5-10 This is understood in relation to various embodiments of the backscatter detection device. Specifically, the radiation detection method portion of this embodiment includes the use of methods described above. Figures 5-10 The steps corresponding to each component of the backscatter detection device are described below. Furthermore, the implementation methods, technical problems solved, functions achieved, and technical effects attained are the same as or similar to the implementation methods, technical problems solved, functions achieved, and technical effects attained by the corresponding components in some embodiments of the device, and will not be repeated here.

[0221] In some embodiments, a material identification method is also provided, the method comprising: in response to a radiation ray scanning target object, detecting radiation ray signals using multiple detector modules of a backscatter detector, the multiple detector modules being arranged at different positions and the ray signal channels being independent of each other; calculating N ray indicators corresponding to the location of each detector module based on the radiation ray signals detected by each detector module, where N is an integer greater than or equal to 1; and identifying the material of the target object based on the indicator values ​​of each ray indicator at different locations.

[0222] For example, the material identification method of this embodiment can perform radiation detection using the radiation detection method described above, and then the processor performs the steps of calculating the ray index and identifying the material. Alternatively, the material identification method of this embodiment can perform backscatter detection using a radiation detection method that is already available or will be disclosed in the future in the related art, and then the processor performs the steps of calculating the ray index and identifying the material.

[0223] It should be noted that for any parts of the material identification method not mentioned in this embodiment, please refer to the above. Figures 11-19 The various embodiments of the corresponding material identification device are understood. Specifically, the material identification method portion of this embodiment includes the use of the methods described above. Figures 11-19 The steps for each component of the material identification device are described below. Furthermore, the implementation methods, technical problems solved, functions achieved, and technical effects attained are the same as or similar to the implementation methods, data processing flows, technical problems solved, functions achieved, and technical effects attained for the corresponding components in some embodiments of the device, and will not be repeated here.

[0224] According to embodiments of this disclosure, by acquiring information such as the energy, count rate, and spatial distribution carried by backscattered X-rays, material resolution can be achieved, and the signal-to-noise ratio of radiation detection can be improved.

[0225] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0226] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A material identification method, comprising: In response to a radiation ray scanning target, multiple detector modules of a radiation detector are used to detect radiation ray signals. The multiple detector modules are arranged in different positions and the ray signal channels are independent of each other. At least two detector modules have different detection area areas, and their respective detection area areas are adapted to their respective target first count rates. The radiation rays include backscattered rays, and the radiation detector includes a backscatter detector. Based on the radiation signal detected by each detector module, calculate N radiation indicators corresponding to the location of each detector module, where N is an integer greater than or equal to 1; The material of the target object is identified based on the spatial distribution differences of the index values ​​of each ray index at different locations.

2. The method according to claim 1, characterized in that, The N ray indicators include a first ray indicator and a second ray indicator. Identifying the material of the target object based on the indicator values ​​of each ray indicator at different locations includes: The index values ​​of the first ray index and the second ray index at different positions are mapped onto a coordinate system, wherein the vertical axis of the coordinate system corresponds to the first ray index and the horizontal axis of the coordinate system corresponds to the second ray index. The material of the target object is identified based on the distribution of the first ray index and the second ray index in the coordinate system.

3. The method according to claim 1, characterized in that, The method of detecting radiation signals using multiple detector modules of a radiation detector in response to a radiation ray scanning target object includes: In response to the radiation source emitting radiation rays to perform a flying-spot scan on the target object, the multiple detector modules are used to detect the backscattered ray signal reflected by the target object.

4. The method according to claim 3, characterized in that, The calculation of the N ray indicators corresponding to the location of each detector module includes: For each of the ray indicators, calculate multiple indicator values ​​corresponding to the location of each detector module; Among them, multiple index values ​​correspond one-to-one with multiple point positions of the flying point scan.

5. The method according to claim 1, characterized in that, Before calculating the N ray indices corresponding to the location of each of the detector modules, the method further includes: Each detector module is assigned a corresponding location identifier based on its location. Among them, the N ray indicators corresponding to the location of each detector module are bound to the location identifier of the detector module.

6. The method according to any one of claims 1 to 5, characterized in that, Before calculating the N ray indices corresponding to the location of each of the detector modules, the method further includes: Energy thresholds are determined for multiple sets of X-ray signals to filter out X-ray signals with different energy ranges from each set of X-ray signals, wherein each set of X-ray signals corresponds one-to-one with the multiple detector modules; Obtain the number of X-ray signals in each group of X-ray signals at different energy ranges.

7. The method according to claim 6, characterized in that, The calculation of the N ray indicators corresponding to the location of each detector module includes: for each group of ray signals Obtain the number of targets with X-ray signals within the target energy range in the different energy ranges; The proportion of the target quantity to the total number of radiation signals is calculated to obtain the first radiation index, wherein the total number of radiation signals is obtained by summing the number of radiation signals under the different energy ranges.

8. The method according to claim 6, characterized in that, The calculation of the N ray indicators corresponding to the location of each detector module includes: for each group of ray signals The ratio of the total number of radiation signals to the counting period is calculated to obtain a second radiation index, wherein the total number of radiation signals is obtained based on the sum of the number of radiation signals under the different energy ranges, and the counting period includes the period for obtaining the number.

9. The method according to any one of claims 1 to 5, 7, and 8, characterized in that, The step of identifying the material of the target object based on the index values ​​of each of the ray indices at different locations includes: The index values ​​of each of the ray indices at different locations are matched with the index information of different materials, wherein the index information of the different materials includes the index values ​​of the different materials at different locations that have been calculated in advance. The material of the target object is identified based on the matching results.

10. The material identification method according to claim 9, characterized in that, The radiation source emits the radiation rays, and two radiation detectors are placed on both sides of the radiation source. The method of detecting radiation signals using multiple detector modules of a radiation detector includes: Radiation signals are detected using multiple detector modules in each of the two radiation detectors.

11. The material identification method according to claim 10, characterized in that, The two radiation detectors located on either side of the radiation source have different structures, and each detects radiation signals from different regions corresponding to the target object. The structure of each radiation detector is determined based on the region of the target object being detected, and the structure includes the detection area of ​​each of the multiple detector modules.

12. The material identification method according to claim 11, characterized in that, Before matching the index values ​​of each of the aforementioned radiation indices at different locations with the index information of different materials, the method further includes: The index information of the material to be matched is determined based on the structure of each of the two radiation detectors. The index information of the material to be matched is calculated based on the radiation ray signals of the material to be matched detected by two preset radiation detectors. The two preset radiation detectors have a one-to-one correspondence with the two radiation detectors and have the same structure.

13. A material identification device for performing the material identification method according to any one of claims 1 to 12, the material identification device comprising: A radiation detector is used to detect radiation signals by using multiple detector modules in response to a target object being scanned by radiation rays. The multiple detector modules are arranged in different positions and the radiation signal channels are independent of each other. The processor, communicatively connected to the radiation detector, is used to perform the following operations: Based on the radiation signal detected by each detector module, calculate N radiation indicators corresponding to the location of each detector module, where N is an integer greater than or equal to 1; The material of the target object is identified based on the index value of each of the ray indices at different locations.

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