RU2426102C1 - Method to identify materials by radiographic re-irradiation - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: analysed objected is subjected to radiographic inspection at various angles to define attenuation coefficients of materials incorporated with said object. Note here that irradiation is performed at preset power levels and for preset materials to be identified. Possible error 6 in coefficient of attenuation is defined for every power level and every inclusion by means of computer program that corresponds to selected error 5. Thereafter, obtained data is processed by computer program to identify materials.

EFFECT: higher accuracy and reliability of identification.

12 tbl

Description

The invention relates to the study of the internal structure or analysis of objects by radiation methods, namely through multi-energy radiography, and can be used, for example, to inspect illegally transported goods or non-destructive testing of materials in determining their internal structure and chemical composition.

The problem of finding the chemical composition of inhomogeneous bodies by radiation methods is very relevant. In this case, radiographic methods for determining the chemical composition of a substance are a rather effective means of studying objects in cases where, for example, it is necessary to perform non-destructive testing of the product or when direct access to the body or its individual parts is difficult or undesirable.

A known x-ray method for determining the mass fractions of substances that make up the body under study (US 2009/0208084 (A1), publ. 08/20/2009). The method includes irradiating the medium at two energy levels, determining the value of the absorption coefficient for each pixel of the body under study and determining the mass fractions of substances entering the body. The disadvantage of this method is the possibility of its use only for ternary media with a predetermined composition.

The known x-ray method of checking an object using multi-energy radiation (RF patent No. 2351921, publ. 10.04.2009). The method includes the interaction of multi-energy radiation with the test object, measuring and recording the measured values after the interaction of multi-energy radiation with the test object, substituting part of the measured values in a predetermined calibration function to obtain information containing the main value of the object’s characteristics, and more accurately determining the characteristics of the material of the object by applying a set of functions suitable for the energy band corresponding to the obtained inf ments The disadvantage of the proposed method is the lack of a clear criterion that allows you to compare the functional dependence of the measured values of a particular material.

Closest to the proposed invention in technical essence and the achieved result is a method of radiation monitoring of liquid objects (RF patent No. 2372610, publ. 10.08.2009). The method is as follows. Get the initial information about the environment of the liquid object; translucent liquid object at various angles; calculate the absorption coefficient of radiation of a liquid object by performing the reverse operation on the data array of the object's translucency at different angles, taking into account the initial information about the environment of the liquid object and its uniformity; comparing the absorption coefficient of radiation with pre-recorded data to obtain relevant information on the liquid object to be checked.

The main disadvantage of the prototype method is its lack of reliability, due to the fact that the exact identification of the object by the value of the absorption coefficient found by this method is not always possible. This is due to the fact that the radiation characteristics of the medium, determined by various methods of computed tomography, are usually found with significant errors and a situation is possible where several substances will correspond to one detected value of the absorption coefficient.

The task of the invention is to increase the accuracy and reliability of identification of materials that make up the heterogeneous body.

The solution to this problem is provided by the method of multiple radiographic exposure. Radiographic methods are quite effective in determining the radiation characteristics of the medium, including the attenuation coefficient of radiation, based on approximate values of which the substances that make up the object under study can be identified.

The inventive method includes the following steps:

1. set a set of values of energies E ₁ , E ₂ , ..., E _N , at which radiographic irradiation of the medium will occur;

2. form a set of M substances, among which a search will be conducted;

3. set the value of the possible relative error of the measurement and method (δ);

4. determine the internal structure of the test object using a multi-energy x-ray apparatus and a computer program to identify homogeneous inclusions G ₁ , G ₂ , ..., G _q in the test object and approximate values of μ _jk attenuation coefficients for each inclusion G _j for each energy value E _k , k = 1, ..., N;

5. form a set of substances S _jk (δ) (for each homogeneous inclusion G _j , j = 1, ..., q, and for each energy level E _k , k = 1, ..., N), the attenuation coefficients of which on the energy E _k have relative deviations from µ _jk less than δ.

6. determine the intersection of these sets for all energies E _k , k = 1, ..., N, for each inclusion G _j , j = 1, ..., q, using a computer program.

If the intersection corresponding to the jth inclusion contains only one substance, then the problem of identifying the substance filling this inclusion is solved. Otherwise, transillumination is carried out at additional energy levels and steps 4-6 are repeated. This approach to the implementation of the claimed invention is confirmed by computer experiments and is based on methods of mathematical modeling.

The problem is optimally solved by performing the above steps as follows.

A set of values of the energies E ₁ , E ₂ , ..., E _{N is set} , at which radiographic irradiation of the medium will occur.

Many M substances are formed, among which a search will be conducted.

- истинные значения коэффициента ослабления во включении G_j для энергии E_k, a µ_jk - значения с ошибками, найденные после всех необходимых измерений и расчетов, то их относительная разница

по модулю не превосходит δ.The value of the maximum relative error δ of determining the coefficient μ _j (E _k ) is set. That is, if

are the true values of the attenuation coefficient in the inclusion G _j for energy E _k , and μ _jk are the values with errors found after all necessary measurements and calculations, then their relative difference

modulo does not exceed δ.

The internal structure of the body is determined in a certain section of the body and the approximate values of μ _jk radiation attenuation coefficients μ (E) for a given set of energy values E _k , k = 1, ..., N, and for each inclusion G _j , j = 1, ..., q , by radiating the body at different angles at given energies using a multi-energy X-ray machine and subsequently processing the results of radiography using a computer program that implements the inverse of the Radon transform [1, 2]. If possible, calibrate the obtained values of μ _jk according to the known values of the attenuation coefficient of the external material. In this case, as a rule, for each energy value there are several substances that, due to the available measurement error and the method, can correspond to the indicated approximate value of the attenuation coefficient. In this case, a direct comparison of the values of the attenuation coefficients determined experimentally and theoretical, presented in tables [3], does not allow to unambiguously identify the substances filling the medium under study.

The sets S _jk (δ) of substances from M are built, the relative difference of which with the approximate value of the attenuation coefficient µ _jk does not exceed δ, using a computer program for each j-th inclusion and for each energy.

, являющиеся пересечениями множеств S_jk(δ) по всем энергиям для каждого j-го включения, то есть

представляет собой множество всех веществ, одновременно принадлежащих всем S_jk(δ). Задача определения химического состава тела G решена однозначно, если все множества

состоят из единственного вещества. В противном случае для однозначной идентификации анализируемого материала требуются его дополнительные просвечивания.Build sets

which are the intersections of the sets S _jk (δ) over all energies for each j-th inclusion, i.e.

represents the set of all substances simultaneously belonging to all S _jk (δ). The problem of determining the chemical composition of the body G is uniquely solved if all the sets

consist of a single substance. Otherwise, for unambiguous identification of the analyzed material, additional transillumination is required.

Thus, the proposed method allows by multiple radiographic irradiation to identify the materials that make up the investigated object.

, являющееся пересечением множеств T_nk(ε) по всем энергиям, то есть

состоит из веществ, которые входят в каждый набор T_nk(ε). Значение ε подбирают таким образом, чтобы множество

содержало только одно вещество, то есть

. Тогда дляThe value of δ can be determined by pre-calibrating the x-ray unit on test objects. In the case when the purpose of the study is to check the presence or absence of substances from a certain predetermined subset M 'in the object under study (for example, explosive, poisonous substances), it is possible to determine the quantity δ, which guarantees the identification of substances from the set M'⊂M if they are present in the studied object. For this purpose, from the set M, all substances from M 'are taken in turn, then, for each substance M _n from M' and some positive number ε, the sets T _nk (ε) are constructed from the tables [3], which consist of all substances for which the relative difference between the attenuation coefficients at energies E _k , k = 1, ..., N, does not exceed ε. Build a lot

, which is the intersection of the sets T _nk (ε) over all energies, i.e.

consists of substances that are included in each set T _nk (ε). The value of ε is chosen so that the set

contained only one substance, i.e.

. Then for

также содержит только одно вещество и

Использование значения δ, найденного по формуле (1), гарантирует идентификацию вещества M_n в случае его присутствия в исследуемом объекте. В случае если требуется идентифицировать вещества из некоторой группы M', то для каждого вещества группы находится свое δ и затем из них выбирается минимальное.a bunch of

also contains only one substance and

Using the value of δ, found by the formula (1), guarantees the identification of the substance M _n if it is present in the studied object. If it is required to identify substances from a certain group M ', then for each substance of the group there is its own δ and then the minimum is selected from them.

содержат единственное вещество, то задача выявления веществ, заполняющих включения G₁, G₂, …, G_q, решена однозначно. Если же какие-то множества

оказываются пустыми, это означает, что материалов из множества M' в соответствующих включениях не содержится. Такая ситуация может быть типичной в случае, когда цель рентгеновского просвечивания состоит, в первую очередь, не в том, чтобы определить, какое именно вещество находится в подобласти G_j, а в том, чтобы убедиться, что в G_j отсутствуют вещества из некоторого множества M'⊂M (включающее, например, конкретные отравляющие, взрывоопасные вещества).If all sets

contain a single substance, then the task of identifying substances filling the inclusions G ₁ , G ₂ , ..., G _q , is solved uniquely. If some sets

turn out to be empty, this means that materials from the set M 'are not contained in the corresponding inclusions. Such a situation may be typical in the case when the purpose of X-ray diffraction is, first of all, not to determine which substance is in the subregion G _j , but to make sure that there are no substances from a certain set in G _j M'⊂M (including, for example, specific toxic, explosive substances).

содержат более одного вещества, и это означает, что для соответствующего включения G_j допускается несколько возможных вариантов его химического состава. В этом случае требуется расширить множество энергий, на которых происходит облучение среды (этап 1), и повторить процедуру идентификации.It should be noted that for δ values greater than δ = ε / (ε + 2), a unique identification of the substance is also possible. However, in this case, a situation is possible when some of the sets

contain more than one substance, and this means that for the corresponding inclusion of G _j several possible variants of its chemical composition are allowed. In this case, it is required to expand the set of energies at which the medium is irradiated (step 1) and repeat the identification procedure.

Thus, the claimed method of identifying materials by multiple radiographic irradiation has several advantages compared with the known:

- the method allows to identify substances of different phase states;

- the method allows to identify materials that are part of a body that is heterogeneous in chemical composition;

- the method allows to identify materials with a high degree of reliability, regardless of the possible measurement errors that occur during radiographic examination of the body;

- the proposed method for identifying materials can be easily automated.

The possibility of practical implementation of the claimed method of identification of materials is shown by a specific example.

EXAMPLE

A sealed cylindrical glass vessel (inclusion G ₂ ) containing an unknown substance (inclusion G ₁ ) is taken, which is hydrochloric acid. It is required using the proposed method to find out if its contents are one of the following acids: sulfuric, hydrochloric, nitric, phosphoric, hydrocyanic, acetic, methane, benzoic, carbolic or stearic. To identify the substance based on the proposed method, the following steps are taken.

1. Choose the following set of energy values on which the translucency of the vessel will be carried out:

2. As M, take the set of 436 substances containing all chemical elements from hydrogen to fermium (Z = 100), inclusive, and substances of complex chemical composition, the names of which are given below. In particular, M included substances represented on the information resource [4]. For all substances M _i from the set M, their attenuation coefficients μ (M _i , E _k ) are calculated on the set of energy values (2). The calculations are carried out according to the scheme described in [3], using the formula

where ρ _i is the density of the substance M _i , μ _xi1 (E), ..., μ _xir (E) are the attenuation coefficients of the chemical elements X _i1 , ..., X _ir that are part of the substance M _i , ρ _xi1 , ..., ρ _xir - density, w _i1 , ..., w _ir - mass fraction of elements X _i1 , ..., X _ir .

будет содержать только одно вещество. Получают следующие предельные значения величины ε для веществ из множества M': для соляной кислоты ε≤0.15, для синильной кислоты ε≤0.13, для азотной, серной, фосфорной, уксусной, метановой, бензойной, карболовой и стеариновой кислот соответстствующие значения ε будут ограничены соответственно величинами 0.088; 0.0802; 0.089; 0.092; 0.0809; 0.099; 0.091; 0.094. Таким образом, минимальное значение ε, при котором гарантируется идентификация любой из этих кислот, составляет 0.0802. По формуле (1) находят соответствующее ему значение δ, равное 0.03855.3. Define many substances M 'subject to guaranteed identification. It includes nitric, sulfuric, hydrochloric, phosphoric, hydrocyanic, acetic, methanoic, benzoic, carbolic and stearic acids. To determine the relative error δ for each substance from the set M 'and for each energy from the set (2), tables of all substances from M are constructed whose attenuation coefficient is close to the attenuation coefficient for substances of the set M'. Detailed results of constructing the sets T _nk (ε) for hydrochloric acid (n = 1) are given in Tables 1-6. For each substance from the set M ', the values of ε are found for which the set

will contain only one substance. The following limit values of ε are obtained for substances from the set M ': for hydrochloric acid ε≤0.15, for hydrocyanic acid ε≤0.13, for nitric, sulfuric, phosphoric, acetic, methanoic, benzoic, carbolic and stearic acids, the corresponding values of ε will be limited, respectively values of 0.088; 0.0802; 0.089; 0.092; 0.0809; 0.099; 0.091; 0.094. Thus, the minimum value of ε at which the identification of any of these acids is guaranteed is 0.0802. By the formula (1) find the corresponding value of δ equal to 0.03855.

4. The glass vessel is illuminated at energies (2) using an X-ray apparatus RAP 150/300. Transmission data is processed using a computer program that implements the convolution algorithm and the inverse projection of the inverse of the Radon transform. As a result, the approximate values of the attenuation coefficients for the energies (2) are calculated. To improve accuracy, calibrate the data on the known material of the vessel (glass - material G ₂ ). As a result of data processing based on the above mathematical methods, the following attenuation coefficients μ _1k were obtained for the substance from inclusion G ₁ and their relative deviations δ _1k from the tabulated values for hydrochloric acid at given energies:

µ ₁₁ = 2.910000E + 00 δ ₁₁ = -2.52022E-02 for E ₁ = 30 keV µ ₁₂ = 1.269000E + 00 δ ₁₂ = 3.43772E-02 for E ₂ = 40 keV µ ₁₃ = 7.440000E-01 δ ₁₃ = 2.99786E-02 for E ₃ = 50 keV µ ₁₄ = 5.290000E-01 δ ₁₄ = -1.17920E-02 for E ₄ = 60 keV µ ₁₅ = 3.150000E-01 δ ₁₅ = 2.94889E-02 for E ₅ = 80 keV µ ₁₆ = 2.550000E-01 δ ₁₆ = -2.52912E-02 for E ₆ = 100 keV

5. For the relative error value obtained in Section 3, δ = 0.03855 and based on the approximate values of μ _1k, sets S _lk (δ) are constructed from Section 4, consisting of substances for which the relative deviation of the attenuation coefficient from μ _1k modulo less than δ. The resulting sets S _lk (δ) are presented in Tables 7-12.

6. Take the intersection of all the sets S _lk (δ), as a result, get the set consisting of a single substance - hydrochloric acid. Thus, the identification of the substance in the inclusion of G ₁ .

When identifying a substance, a set of 436 substances was taken, containing all chemical elements from hydrogen to fermium (Z = 100) inclusively and substances of complex chemical composition shown in the following list:

1,3-butadiene (divinyl), 1,4-butanedicarboxylic acid, B-100 plastic, VX (Vi-X), Adamsit (DM), Nitric acid, Azurite, Alanya, Diamond, Albit, Almandine, Anataz, Andalusite, Andradite, Anorthite, Iridium Antimonide, Anthracene, Apatite, Apophyllite, Aragonite, Gallium Arsenide, Iridium Arsenide, Cobalt Arsenide, Acetone, Benzoic acid, Benzene, Benitoite, Beryl (emerald, aquamarine), Beronetonite, boronitronite, boronitonite, , Turquoise, Barium Boride, Tungsten Boride, Molybdenum Boride, Tantalum Boride, Titanium Boride, Thorium Boride, Cerium Boride, Brasilianite, Brome lithium, Potassium bromide, Tin bromide, Tin (IV) bromide, Thallium (I) bromide, Titanium bromide (IV), Brookite, Wardite, Variscite, Willemite, Water, Gambergit, Hexadecanoic acid, Hexogen, Hematite, Hemimorphite, Magnesium germanide, Sodium bicarbonate, Calcium hydroxide, Gypsum, Ophthalmic lens, Graphite, Grossular, D-2,3-dioxibutanoic acid, Danburite, Datolite, Diopside, Dioptase, Difosgen, Jadeite, Adipose tissue, Zarin, Zoman, Ilmenite (titanium iron), Iprit , Beryllium iodide, Tin (II) iodide, Tin (IV) iodide, Mercury iodide, Thallium (I) iodide, Titanium (IV) iodide, Cerium iodide, Yo Potassium Dide, Calcite, Carbamide (Urea), Tungsten Carbide, Tungsten Carbide (II), Tungsten Carbide (IV), Hafnium Carbide, Silicon Carbide, Molybdenum Carbide, Niobium Carbide, Tantalum Carbide, Titanium Carbide, Thorium Carbide, Carbide Thorium, Carbide cerium, Zirconium carbide, Calcium carbonate, Sodium carbonate, Cassiterite, Quartz, Kyanite, Cocaine, Cornerupin, Corundum, Bone tissue, Blood in general, Lazulit, Luizit (L), Malachite, Potassium manganate (VII), Metanal (formaldehyde), Methanic acid, Methanol (methyl alcohol), Microcline, Silicon monosulfide, Mullite, Soap (laundry), M soft fabric, Naphthalene, lithium niobate, potassium nitrate (potassium nitrate), sodium nitrate, silver nitrate (lapis), aluminum nitride, beryllium nitride, vanadium nitride, tungsten nitride, gallium nitride, hafnium nitride, indium nitride, calcium nitride, nit , Lithium Nitride, Molybdenum Nitride, Niobium Nitride, Plutonium Nitride, Tantalum Nitride, Titanium Nitride, Thorium Nitride, Uranium Nitride, Chromium Nitride, Cerium Nitride, Zirconium Nitride, Nosean, Nitric Oxide (V), Alumina, Silica, Beryllium oxide, Boron oxide, Vanadium (II) oxide, Vanadium (III) oxide, Oxide nadium (IV), vanadium (V) oxide, tungsten (VI) oxide, hafnium oxide, dysprosium oxide, ytterbium oxide, cadmium oxide, calcium oxide, lanthanum aluminum oxide, lithium aluminum oxide, lithium gallium oxide, magnesium oxide, Gallium Neodymium Oxide, Tin (IV) Oxide, Thallium (I) Oxide, Thallium (III) Oxide, Titanium Oxide (II), Titanium Oxide (III), Titanium Oxide (III, IV), Thorium Oxide, Zinc Oxide, Oxide zirconium, Erbium oxide, Octadecanoic acid, Olivine (fayalit), Olivine (forsterite), Orthoclase, Orthoplumbate lead (II), Periclase, Ammonium picrate, Picric acid (2,4,6-Trinitrophenol), Pyrite, Pyrope, eraser Mular, Plastic C-552, Magnesium plumbid, Polyvinyl chloride, Pollutsit, Prehnit, Pseudophytum, Rhodicite, Rhodonite, Rhodochrosite, Rutile, Sapphire, Sucrose, Aluminum selenide, Copper-aluminum selenide, Copper-thallium selenide, Selenide, tin (II) Tin (IV) selenide, Lead selenide, Silver-aluminum selenide, Silver-antimony selenide, Sulfuric acid, Gadolinium sulfate, Serpentine, Vanadium silicide, Tungsten silicide, Magnesium silicide, Molybdenum silicide, Niobium silicide, Syngalit Smitin, hydrocyanic acid , Hydrochloric acid, spessartine, ethyl alcohol, spodumene, sta Magnesium Nnide, Glass, Lead Glass, Stichtite, Iron Sulfate, Calcium Sulphate, Sodium Sulphate-Water, Aluminum Sulphide, Boron Sulphide, Calcium Sulphide, Calcium Gadolinium Sulphide, Calcium Lanthanum Sulphide, Calcium Neodymium Sulphide, Calcium Praseodymium Sulphide, Calcium Samarium Sulfide, Lithium Sulfide, Copper-Cadmium Tin Sulfide, Sodium Sulfide, Lead Sulfide, Strontium-Gadolinium Sulfide, Strontium-Holmium Sulfide, Strontium-Lanthanum Sulfide, Strontium-Neodymium Sulfide, Strontium-Sodium Praseodymium Sulfide, , Strontium Erbium Sulfide, Sulfide d thallium (I), titanium (II) sulfide, zinc-gallium sulfide, zirconium sulfide, dry air, sphene, talc, taffeite, tungsten (IV) telluride, cadmium telluride, tin (II) telluride, lead telluride, silver telluride- aluminum, Lithium tetraborate, Magnesium tetraborate, Sodium tetraborate-water (Borax), Teflon, Strontium titanate, Textile equivalent. gas, Gonadal tissue, Lung tissue, Brain tissue, Muscle tissue, Ovarian tissue, Tol, TNT (cast), Triiodomethane (iodoform), Trichloromethane (chloroform), Uvarovit, Acetic acid, Kodak f / emulsion, Standard f / emulsion, Phenacite, Phenylmethanal (benzaldehyde), Phenol, Fibrolite, Fluorite, Phosgene, Aluminum Phosphide, Iridium Phosphide, Calcium Phosphide, Phosphoric Acid, Fructose (Fruit Sugar), Beryllium Fluoride, Vanadium (III) Fluoride, Potassium Fluoride, Magnesium Copper Fluoride, Magnesium Fluoride , Tin (II) Fluoride, Thallium (I) Fluoride, Titanium (III) Fluoride, Titanium (IV) Fluoride, Calcium Fluoride, Fluorine lithium chloride, Chalcedony, Chalcosine (copper luster), Chalcopyrite (copper pyrites), Chlorobenzene, Beryllium chloride, Tungsten (VI) chloride, Potassium chloride, Sodium chloride (sodium chloride), Tin (II) chloride, Thallium chloride (I), Thallium (III) Chloride, Titanium (II) Chloride, Thorium Chloride, Ammonium Chloride (ammonia), Chlorocyan (cyclotrimethylenetrinoitroamine), Chrysoberyl, Tsv. pl. radiochromic, Cellulose, Potassium cyanide, Zinc, Zinc blende, Zircon (metamict), Zircon (normal), Zoisite (tulite), Shellac, Spinel, Epidote, Ethylamine (aminoethane), Ethylbenzene, Ethyl chloride (chloroethane), Ethyl ethoxy .

LITERATURE

1. Anikonov D.S., Kovtanyuk A.E., Prokhorov I.V. Using the transport equation in tomography. M .: Logos, 2000, 224 p.

2. Naterrer F. Mathematical aspects of computed tomography. M.: Mir, 1990, 288 p.

3. Hubbell J.H., Seltzer S.M. Tables of X-ray mass attenuation coefficients and mass energy-absorption coefficients 1 Kev to 20 Mev for elements Z = 1 to 92 and 48 addslional substances of dosimetric interest. NISTIR 5632, 1995.

4. Anikonov D.S., Kovtanyuk A.E., Nazarov V.G., Prokhorov I.V., Surovenko N.S., Yarovenko I.P. Database of radiation characteristics of substances of interest in x-ray diagnostics. Certificate of state registration of the database No. 20099620348, 06/19/2009. Internet resource: http://imcs.dvgu.ru/struc/kmf/dbase.

Claims (1)

A method for identifying materials by repeated radiographic irradiation, including radiographic scanning of the test object at different angles, determining attenuation coefficients for the materials included in the object, characterized in that the irradiation is carried out on a predetermined set of energies, a set of substances to be guaranteed are specified, then it is determined possible error (δ) of finding the attenuation coefficients for each energy level and for each inclusion with by means of a computer program, a possible set of substances corresponding to the selected error δ is determined, after which the data obtained is processed using a computer program to identify materials.