WO2021169039A1 - Adjustable pulsed flat-panel portable x-ray inspection device and dual-energy material identification method using same - Google Patents

Abstract

Disclosed are an adjustable pulsed flat-panel portable X-ray inspection device, which is a security inspection apparatus, and a dual-energy material identification method using the adjustable pulsed flat-panel portable X-ray inspection device. The inspection device comprises a pulsed ray source (1), a filtering device (2), a flat panel detector (3) and a control device. The filtering device (2) is fixed in front of a beam outlet of the pulsed ray source (1), and the filtering device (2) filters low-energy rays by means of rotation. In the device, the pulsed X-ray source (1) and the flat panel detector (3) are used to implement an X-ray transmission imaging method, in which, by means of controlling the pulse number of the pulsed X-ray source (1) and the filtering device (2) arranged at the front end of the X-ray source, the same inspected object is subjected to transmission imaging under X-rays of two different energies, and two imaging signals of different energies are then subjected to algorithm processing to obtain an equivalent atomic number of the detected object, thereby achieving the identification of substances and implementing the inspection of objects including luggage, parcels or mail.

Description

Adjustable pulse type flat-panel portable X-ray inspection device and its dual-energy material resolution method Technical field

The invention belongs to security inspection equipment, in particular to an adjustable pulse type flat-panel portable X-ray inspection device and a dual-energy material resolution method.

Background technique

There are two ways to distinguish prohibited items from X-ray projection images: 1. From the shape of objects in the image, such as daggers, guns, etc., they can be distinguished from the shape; 2. Using dual-energy technology to analyze the items in the image For the identification of material properties, this method has nothing to do with the shape of the object. It is more effective for organic substances that can be of any shape, such as explosives and drugs.

At present, most portable security inspection equipment are single-energy X-ray security inspection equipment, which can only recognize the shape of the object but not the material of the object; and the patent CN201510701589 requires the use of a portable X-ray source that can provide two different energies to realize the identification of the object material However, this type of ray source can only be a constant potential, not a pulse type. The constant potential X-ray source has the disadvantages of large volume, heavy weight, and high cost.

technical problem

Provided is an adjustable pulse-type flat-panel portable X-ray inspection device and a dual-energy material resolution method to solve the problems involved in the above-mentioned background art.

Technical solutions

The invention provides an adjustable pulse-type flat-panel portable X-ray inspection device, which includes four parts: a pulse-type ray source, a filter device, a flat-panel detector and a control device.

The ray source is a tunable pulsed ray source, which can emit X-rays with different pulse numbers;

The filter device is fixedly installed in front of the beam exit of the pulsed ray source, and includes a filter, and a fixing member for supporting and fixing the filter, and the fixing member can be located at the beam exit along the pin axis Rotate, filter low-energy rays through the rotation of the filter;

Detector, capable of receiving image data of high-energy rays and low-energy rays;

The control device is a portable notebook computer, which is connected to the pulsed ray source, the filter device and the detector with signals, and controls the beam emission and imaging of the pulsed ray source.

As a preferred solution, the ray source is one or a combination of any number of ionizing radiation sources of gamma radiation and X-rays.

As a preferred solution, the signal connection can connect the pulsed ray source and the flat panel detector respectively through a cable, and can also be connected with a wireless communication signal.

As a preferred solution, the filter is a foil made of aluminum, lead, tungsten, copper, iron, antimony, nickel or an alloy material thereof. The present invention also provides a dual-energy material resolution method for an adjustable pulse type flat-panel portable X-ray inspection device, which includes the following steps:

S1, set the number of single exposure pulses in the two states of pulse X-ray machine;

S2. Use dual-energy rays to calibrate test bodies of different materials to obtain dual-energy imaging data of each test body;

S3. Perform cubic spline interpolation according to the low-energy and high-energy data of different materials, and fit and generate the boundary curve of the substance;

S4. Use dual-energy rays to test the probes respectively to obtain dual-energy imaging data of the probes;

S5. Calculate the dual-energy R value of the object to be measured, and assign different colors to the material regions with different R values for display.

As a preferred solution, N ₁ , N ₂ and A ₁ , A _{2 are selected} so that the radiation dose of a single exposure in the two states is approximately equal, N ₁ ·(1-A ₁ )≈N ₂ ·(1-A ₂ ) ; Among them, N ₁ and N ₂ are the number of pulses _{in the low-energy and low-energy states, respectively, and A 1} and A ₂ are the attenuation coefficients of the filter device in the low-energy and low-energy states, respectively. As a preferred solution, the test body is a step shape with different step thicknesses of multiple materials, and the materials of the test body are carbon, aluminum, iron, and copper.

As a preferred solution, perform cubic spline interpolation according to the low-energy and high-energy data of different test materials, and use the high and low energy data to perform polynomial classification on the substance classification curve.

I _h = ∑ ₀ ⁿ a _n · I _l ⁿ

Fit, get the boundary curve of the substance and generate the substance classification file; there are:

I _h = I _oh ·exp(- μ _h l ),

I _h = I _ol · exp(- μ _l l ),

Among them, I _h and I _l are the light intensity of the high and low energy X-rays incident on the detector _{respectively; I oh} and I _ol are the output light intensity of the high and low energy X-ray sources _{respectively; μ h} and μ _l are the high and low levels of the same substance. linear attenuation coefficient upon energy; L is the thickness of the material along the path of the beam irradiation, a _n is the polynomial fit coefficients, for the same X-ray source and the same detector group, a _n is the corresponding constant.

As a preferred solution, since the actual ray source emits multi-chromatographic X-rays, for multi-chromatographic X-rays, the intensity of the low-energy and high-energy signals received by the detector can be expressed by the following formula:

I _L =∫ ₀ ^Em S _L (E)·exp(∫ _s -μ(E,S)sds)dE

I _H =∫ ₀ ^Em S _H (E)·exp(∫ _s -μ(E,S)sds)dE

_{Where, S L (E), S} H (E) of the incident spectral low energy and high energy, μ (E, S) is the linear attenuation coefficient s position on the energy E of the ray casting direction, E _m is the radiation of the highest energy .

As a preferred solution, the correlation between the transmission thickness of different materials and the ray energy under the multi-chromatographic X-ray, that is, the dual energy R value is: R=μ _h /μ _l = (In I _oh / I _h )/ (In I _ol / I _l )

=(a _h1 r _h + a _h2 r _h ² +…+a _hn r _h ⁿ )/(a _l1 r _l + a _l2 r _l ² +…+a _ln r _l ⁿ )

Wherein, r _l, r _h were treated material thickness of the transparent material of different thickness of the transparent object to be measured, and a _n the coefficients of the polynomial is fitted, for the same X-ray source and the same detector group, a _n corresponding to the constant.

Beneficial effect

The invention relates to an adjustable pulse-type flat-panel portable X-ray inspection device, which adopts a pulse-type X-ray source and a flat-panel detector and applies an X-ray transmission imaging method. The imaging principle is to control the pulse number and device of the pulse-type X-ray source The filter device at the front end of the X-ray source allows two X-rays with different energies to perform transmission imaging on the same object under inspection respectively, and then perform algorithmic processing on the two imaging signals with different energies to obtain the equivalent atomic number of the object under inspection. So as to realize the material identification and complete the inspection of objects including luggage, parcels or mail.

Description of the drawings

Figure 1 is a schematic diagram of the structure of the present invention.

Fig. 2 is a schematic diagram of the structure of the filtering device of the present invention.

Fig. 3 is a schematic diagram of the structure of each material step tool in the present invention.

The reference numerals are: X-ray source 1, filter device 2, flat panel detector 3, cable 4, notebook computer 5, fixed ring 6, filter 7, fixed part 8, pin 9.

Embodiments of the present invention

In the following description, a lot of specific details are given in order to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features known in the art are not described.

As shown in FIG. 1, an adjustable pulse type flat-panel portable X-ray inspection device includes: a pulse adjustable X-ray source 1, a filter device 2, a flat-panel detector 3, a cable 4, and a portable notebook computer 5. The portable notebook computer 5 is respectively connected with the pulsed X-ray source 1 and the flat-panel detector through the cable 4, and the pulsed adjustable X-ray source 1 is controlled by software to emit and image. Wherein, the filter device is fixed in front of the beam exit of the ray source by a fixing ring 6, and the filter 7 and its fixing member 8 can rotate around the pin 9. When the filter 7 rotates to a position close to the fixed ring 6, the filter 7 is on the X-ray optical path, and the low-energy part of the X beam emitted by the X-ray source 1 will be filtered by the filter 7, and the flat panel detector 3 receives it. It is high-energy data; when the filter 7 is in the position shown in Figure 2, the flat-panel detector receives a low-energy image. As shown in FIG. 2, the lifting and lowering of the filter 7 is completed manually.

For the convenience of detection, in this embodiment, the automatic motor mode is adopted, and a small servo motor is connected to one end of the pin shaft 9. The rotation of the small servo motor drives the filter 7 and its fixing member 8 to rotate around the pin shaft 9 .

In the further implementation process, for those skilled in the art, the filter 7 uses one of aluminum, lead, tungsten, copper, iron, antimony, nickel and other metals, a metal material alloy, or many of them. A foil made of an alloy of two metal materials can be determined according to the actual situation.

In a further implementation process, the fixed ring and the radiation source are connected in a detachable connection manner. It is convenient to install the filter device and improve portability.

Those skilled in the art should understand that the radiation source in the present invention may be gamma radiation, X-ray or any number of ionizing radiation sources. For example, X-ray transmission, X-ray backscatter, X-ray CT, etc., form a pulsed cone beam; the detector is a flat-panel detector.

In the further implementation process, the signal connection between the pulse-tunable X-ray source 1, the filter device 2, the flat-panel detector 3, and the portable notebook computer 5 is not limited to connecting the pulse-type ray source and the flat-panel detector through cables. Can be connected via wireless communication signals.

First, lift the filter device 2 in front of the X-ray source's beam exit, set the single exposure pulse number N _{1 of the} pulse X-ray machine, and collect the X-ray light intensity I _{o l} . If you remember the filter device in the lifted state The attenuation coefficient is A ₁ , then the radiation dose I _{o l of a} single exposure at this time is proportional to N ₁ ·(1-A ₁ ); then put down the filter device in front of the X-ray source's beam outlet and set different pulse X The number of single exposure pulses of the light machine is N ₂ , the collected X-ray light intensity I _{o l} , if the attenuation coefficient of the filter device in the down state is A ₂ , and A ₂ > A _1. Then the single exposure is The radiation dose is proportional to N ₂ ·(1－A ₂ ); the choice of N ₁ , N ₂ and A ₁ , A ₂ makes the radiation dose of a single exposure roughly equal in the two states, N ₁ ·(1－A ₁ )≈ N ₂ ·(1-A ₂ ) In the embodiment, N ₁ =6, N ₂ =10).

Since the filter device filters a part of low-energy X-rays, the average energy of X-rays in step 2 is higher than the average energy of X-rays in step 1. Hereinafter, the state of step 1 is also referred to as low energy, and the state of step 2 is high energy.

Carry out material calibration: first lift the filter device in front of the X-ray source's beam outlet, set the pulse number N ₁ of the X-ray machine, and place a step-thickness material test body between the X-ray source and the flat panel detector (the shape shows the opinion Figure 3), get the low-energy projection data of each material; then put down the filter device in front of the X-ray source, set the pulse number N _{2 of the} X-ray machine, and get the high-energy projection data of each material. The method of lifting and lowering the filter device can be done manually or by a motor installed on the filter device, which is automatically controlled by software. The materials of the test body are carbon, aluminum, iron, and copper, and the thickness of each S (S=16 in the embodiment) of the steps. The image of each test body is divided into C regions according to the thickness of the steps (C=64 in the embodiment) ), use a T×T Gaussian filter (T=5 in the embodiment) to smooth the area data, and calculate the average value of each area to obtain low-energy imaging data I _l and high-energy imaging data I _{h for} each material step. Carry out cubic spline interpolation according to the low-energy and high-energy data of different materials, and use the high and low energy data to perform polynomials on the substance classification curve

I _h = ∑ ₀ ⁿ a _n · I _l ⁿ

Fitting to get the boundary curve of the substance. If the high and low energy X-rays are approximated by the monochromatic energy spectrum, there are:

I _h = I _oh ·exp(- μ _h l ),

I _h = I _ol · exp(- μ _l l ),

Among them, a _n is the coefficient of the fitting polynomial, I _h and I _l are the light intensity of the high and low energy X-rays incident on the detector; I _oh and I _ol are the output light intensity of the high and low energy X-ray sources, respectively; μ _h and μ _l is the linear attenuation coefficient of the same substance at high and low energies; l is the thickness of the substance along the path of radiation.

However, the actual X-ray source emits multi-chromatograms. For multi-chromatographic X-rays, there are:

I _L =∫ ₀ ^Em S _L (E)·exp(∫ _s -μ(E,S)sds)dE

I _H =∫ ₀ ^Em S _H (E)·exp(∫ _s -μ(E,S)sds)dE

_{Where, S L (E), S} H (E) of the incident spectral low energy and high energy, μ (E, S) is the linear attenuation coefficient s position on the energy E of the ray casting direction, E _m is the radiation of the highest energy ; Here our purpose is to consider the relationship between the transmission thickness of different materials and the ray energy under the continuous energy spectrum, without considering the overlap of multiple types of objects in the ray direction, so the calculation formulas of _{I L} and I _{H are rewritten as:}

I _L =∫ ₀ ^Em S _L (E)·exp(∫ _s -μ(E)l)dE

I _H =∫ ₀ ^Em S _H (E)·exp(∫ _s -μ(E)l)dE

We can approximate the detector value under multi-chromatographic X-ray to the equivalent power spectrum under a certain single chromatogram, so: R=μ _h /μ _l = (In I _oh / I _h )/(In I _ol / I _l )

Let In I _oh / I _h = f®, f® = ∑ ₀ ⁿ a _n · r ⁿ then

R=μ _h /μ _l =(In I _oh / I _h )/(In I _ol / I _l )

=(a _h1 r _h + a _h2 r _h ² +…+a _hn r _h ⁿ )/(a _l1 r _l + a _l2 r _l ² +…+a _ln r _l ⁿ )

(In the example, n generally takes 3). Wherein, r _l, r _h were treated material thickness of the transparent material of different thickness of the transparent object to be measured, and a _n the coefficients of the polynomial is fitted, for the same X-ray source and the same detector group, a _n corresponding to the constant.

For the same X-ray source and the same detector group, a _n is the corresponding constant, the calculated R values are relatively constant. Perform cubic spline interpolation on the obtained high and low energy data of the step thickness of each material to fit and generate a substance classification curve. The data of the curve is saved in the substance classification file of the supporting software of the portable X-ray inspection device. The substance classification file does not need to be regenerated before each shooting; only when the device is not used for a long time or when the device is used too frequently, which causes the emission spectrum of the X-ray source to drift or change, the substance classification file needs to be regenerated.

Photograph the object to be detected: place the object to be detected between the flat panel detector and the ray source, first lift the filter device, emit low-energy X-ray pulses, and collect the low-energy data of the object to be measured; then lower the filter device to collect High-energy data of the measured object. According to the substance classification file obtained above, the dual energy R value of the object to be measured is calculated, and the substance areas with different R values are given different colors for display.

The specific steps are: lift the filter device 2 at the beam exit of the X-ray source, place the object to be detected between the flat panel detector 3 and the pulse-tunable X-ray source 1, operate the software in the portable notebook computer 5, and set the pulse The number of single exposure pulses of the X-ray source 1 is N ₁ , and the beam starts to be emitted. At the same time, the flat-panel detector 3 will receive the X-ray, convert it into a digital image and send it to the portable notebook computer 5. This image is a low-energy image of the object to be measured . Then, the filter device 2 at the beam exit of the X-ray source is put down, the single exposure pulse number N _{2 of the} pulsed X-ray source 1 is set and the beam is emitted, and the flat panel detector 3 receives the high-energy image data of the object to be measured. The low-energy and high-energy images are processed by the substance classification algorithm in the software to generate dual-energy images that can distinguish inorganic substances, mixtures and organic substances by color. Different R corresponds to different equivalent atomic numbers, and lower equivalent atomic numbers have lower R values. On the software display interface of the portable X-ray inspection device, substances with relatively low equivalent atomic numbers (usually non-metals such as plastics, paper, wood, etc., generally R is between 0.9 and 1.2) are displayed in orange, and the equivalent atomic number is displayed. Medium substances (usually light metals such as aluminum and glass and heavy non-metals, generally R is between 1.3 and 1.5) are displayed in green, and substances with higher equivalent atomic numbers (usually metals such as iron and copper, generally R is 1.6 ～1.9) is displayed in blue, and the display brightness is determined according to the gray value of the pixel, so that the user of the device can directly observe the material of the inspected item (ie, the equivalent atomic number) on the software interface.

In addition, it should be noted that the various specific technical features described in the foregoing specific embodiments can be combined in any suitable manner, provided that there is no contradiction. In order to avoid unnecessary repetition, various possible combinations are not described separately in the present invention.

Claims (9)

1. An adjustable pulse type flat-panel portable X-ray inspection device, which is characterized in that it comprises:

   The ray source is a tunable pulsed ray source, which can emit X-rays with different pulse numbers and cone shapes;

   The filter device is installed in front of the beam exit of the pulsed ray source and includes a filter, and a fixing member for supporting and fixing the filter, and the fixing member can be rotated along the pin at the beam exit , Filter low-energy rays through the rotation of the filter to form dual-energy rays;

   Detector, capable of receiving image data of high-energy rays and low-energy rays;

   The control device is a portable notebook computer, which is connected to the pulsed ray source, the filtering device and the detector in signal, and controls the beam emission and imaging of the pulsed ray source.
2. The adjustable pulse-type flat-panel portable X-ray inspection device according to claim 1, wherein the signal connection can respectively connect the pulse-type ray source and the flat-panel detector through a cable, and can also be connected with a wireless communication signal.
3. The adjustable pulse type flat-panel portable X-ray inspection device according to claim 1, wherein the filter is made of aluminum, lead, tungsten, copper, iron, antimony, nickel or an alloy material thereof. piece.
4. A dual-energy material resolution method for an adjustable pulse flat-panel portable X-ray inspection device according to any one of claims 1 to 3, characterized in that it comprises the following steps:

   S1, set the number of single exposure pulses in the two states of pulse X-ray machine;

   S2. Use dual-energy rays to calibrate test bodies of different materials to obtain dual-energy imaging data of each test body;

   S3. Perform cubic spline interpolation according to the low-energy and high-energy data of different materials, and fit and generate the boundary curve of the substance;

   S3. Use dual-energy rays to test the probes respectively to obtain dual-energy imaging data of the probes;

   S4. Calculate the dual-energy R value of the object to be measured, and assign different colors to the material areas with different R values for display.
5. The dual-energy material discrimination method of an adjustable pulse type flat-panel X-ray inspection device according to claim 4, wherein in the S1 step, N ₁ , N ₂ and A ₁ , A _{2 are selected} such that two The radiation dose of a single exposure in the state is equal, N ₁ •(1-A ₁ )=N ₂ •(1-A ₂ ); where N ₁ and N ₂ are the number of pulses in the low-energy and low-energy states, A ₁ , A ₂ are the attenuation coefficients of the filter device in low-energy and low-energy states, respectively.
6. The dual-energy material discrimination method for an adjustable pulse-type flat-panel portable X-ray inspection device according to claim 4, wherein, in the S2 step, the test body is a stepped shape of multiple materials with different step thicknesses. , The materials of the test body are carbon, aluminum, iron, and copper.
7. The dual-energy material discrimination method of the adjustable pulse type flat-panel portable X-ray inspection device according to claim 5, wherein, in the S3 step, cubic spline interpolation is performed according to the low-energy and high-energy data of different test body materials , Using high and low energy data to perform a polynomial on the substance classification curve I _h = ∑ ₀ ⁿ a _n· I _l ⁿ Fit, get the boundary curve of the substance and generate the substance classification file; there are:

   I _h = I _oh ·exp(- μ _h l ),

   I _h = I _ol · exp(- μ _l l ),

   Among them, I _h and I _l are the light intensity of the high and low energy X-rays incident on the detector _{respectively; I oh} and I _ol are the output light intensity of the high and low energy X-ray sources _{respectively; μ h} and μ _l are the high and low levels of the same substance. linear attenuation coefficient upon energy; L is the thickness of the material along the path of the beam irradiation, a _n is the polynomial fit coefficients, for the same X-ray source and the same detector group, a _n is the corresponding constant.
8. The dual-energy material resolution method of an adjustable pulse flat-panel portable X-ray inspection device according to claim 4, characterized in that, in the S4 step, since the actual radiation source emits multi-chromatographic X-rays, For multi-chromatographic X-rays, the low-energy and high-energy signal strength received by the detector can be expressed by the following formula:

   I _L =∫ ₀ ^Em S _L (E)·exp(∫ _s -μ(E,S)sds)dE

   I _H =∫ ₀ ^Em S _H (E)·exp(∫ _s -μ(E,S)sds)dE

   _{Where, S L (E), S} H (E) of the incident spectral low energy and high energy, μ (E, S) is the linear attenuation coefficient s position on the energy E of the ray casting direction, E _m is the radiation of the highest energy .
9. The dual-energy material discrimination method of the adjustable pulse type flat-panel X-ray inspection device according to claim 4, characterized in that, in the step S5, the transmission thickness and ray energy of different materials under the multi-chromatographic X-ray The mutual relationship of the dual energy R value:

   R=μ _h/μ _l= (In I _oh / I _h ) /(In I _ol / I _l )

   =(a _h1r _h+ a _h2r _h ²+...+a _hn r _h ⁿ)/(A _l1r _l+ a _l2r _l ²+...+a _lnr _l ⁿ)

   To

   

   Wherein, r _l, r _h were treated material thickness of the transparent material of different thickness of the transparent object to be measured, and a _n the coefficients of the polynomial is fitted, for the same X-ray source and the same detector group, a _n corresponding to the constant.