The nature of X-rays and their main properties. Detection and measurement of radiation

X-rays were discovered by accident in 1895 by the famous German physicist Wilhelm Roentgen. He studied cathode rays in a low-pressure gas-discharge tube with a high voltage between its electrodes. Despite the fact that the tube was in a black box, Roentgen noticed that a fluorescent screen, which happened to be nearby, glowed every time the tube was in operation. The tube turned out to be a source of radiation that could penetrate paper, wood, glass, and even a half-centimeter-thick aluminum plate.

X-ray determined that the gas discharge tube is a source of a new type of invisible radiation with a high penetrating power. The scientist could not determine whether this radiation was a stream of particles or waves, and he decided to give it the name X-rays. Later they were called X-rays.

It is now known that X-rays are a form of electromagnetic radiation having a shorter wavelength than ultraviolet electromagnetic waves. The wavelength of X-rays ranges from 70 nm up to 10 -5 nm. The shorter the wavelength of the X-rays, the greater the energy of their photons and the greater the penetrating power. X-rays with a relatively long wavelength (more than 10 nm), are called soft. Wavelength 1 - 10 nm characterizes tough X-rays. They have great penetrating power.

Getting x-rays

X-rays are produced when fast electrons, or cathode rays, collide with the walls or anode of a low-pressure discharge tube. A modern X-ray tube is an evacuated glass container with a cathode and an anode located in it. The potential difference between the cathode and the anode (anticathode) reaches several hundred kilovolts. The cathode is a tungsten filament heated by an electric current. This leads to the emission of electrons by the cathode as a result of thermionic emission. Electrons are accelerated by an electric field in an x-ray tube. Since there is a very small number of gas molecules in the tube, the electrons practically do not lose their energy on their way to the anode. They reach the anode at a very high speed.

X-rays are always produced when high speed electrons are retarded by the anode material. Most of the electron energy is dissipated as heat. Therefore, the anode must be artificially cooled. The anode in the x-ray tube must be made of a metal having a high melting point, such as tungsten.

Part of the energy that is not dissipated in the form of heat is converted into electromagnetic wave energy (X-rays). Thus, X-rays are the result of electron bombardment of the anode material. There are two types of X-rays: bremsstrahlung and characteristic.

Bremsstrahlung X-ray

Bremsstrahlung occurs when electrons moving at high speed are decelerated by the electric fields of anode atoms. The deceleration conditions of individual electrons are not the same. As a result, various parts of their kinetic energy pass into the energy of X-rays.

The bremsstrahlung spectrum is independent of the nature of the anode material. As you know, the energy of X-ray photons determines their frequency and wavelength. Therefore, bremsstrahlung X-rays are not monochromatic. It is characterized by a variety of wavelengths that can be represented continuous (continuous) spectrum.

X-rays cannot have an energy greater than the kinetic energy of the electrons that form them. The shortest X-ray wavelength corresponds to the maximum kinetic energy of decelerating electrons. The greater the potential difference in the x-ray tube, the smaller the x-ray wavelengths can be obtained.

Characteristic X-rays

The characteristic X-ray radiation is not continuous, but line spectrum. This type of radiation occurs when a fast electron, on reaching the anode, enters the inner orbitals of atoms and knocks out one of their electrons. As a result, a free space appears, which can be filled by another electron descending from one of the upper atomic orbitals. This transition of an electron from a higher to a lower energy level causes x-rays of a certain discrete wavelength. Therefore, the characteristic X-ray radiation has line spectrum. The frequency of the characteristic radiation lines depends entirely on the structure of the electron orbitals of the anode atoms.

The spectral lines of the characteristic radiation of different chemical elements have the same form, since the structure of their internal electron orbits is identical. But their wavelength and frequency are due to the energy differences between the inner orbitals of heavy and light atoms.

The frequency of the lines of the characteristic X-ray spectrum changes in accordance with the atomic number of the metal and is determined by the Moseley equation: v 1/2 = A(Z-B), where Z- atomic number of a chemical element, A and B- constants.

Primary physical mechanisms of interaction of X-rays with matter

The primary interaction between X-rays and matter is characterized by three mechanisms:

1. Coherent scattering. This form of interaction occurs when X-ray photons have less energy than the binding energy of electrons to the nucleus of an atom. In this case, the energy of the photon is not sufficient to release electrons from the atoms of matter. The photon is not absorbed by the atom, but changes the direction of propagation. In this case, the wavelength of X-ray radiation remains unchanged.

2. Photoelectric effect (photoelectric effect). When an X-ray photon reaches an atom of matter, it can knock out one of the electrons. This occurs when the photon energy exceeds the binding energy of the electron with the nucleus. In this case, the photon is absorbed, and the electron is released from the atom. If a photon carries more energy than is needed to release an electron, it will transfer the remaining energy to the released electron in the form of kinetic energy. This phenomenon, called the photoelectric effect, occurs when relatively low-energy X-rays are absorbed.

An atom that loses one of its electrons becomes a positive ion. The lifetime of free electrons is very short. They are absorbed by neutral atoms, which turn into negative ions. The result of the photoelectric effect is intense ionization of matter.

If the energy of an X-ray photon is less than the ionization energy of atoms, then the atoms go into an excited state, but are not ionized.

3. Incoherent scattering (Compton effect). This effect was discovered by the American physicist Compton. It occurs when a substance absorbs X-rays of small wavelength. The photon energy of such X-rays is always greater than the ionization energy of the atoms of the substance. The Compton effect is the result of the interaction of a high-energy X-ray photon with one of the electrons in the outer shell of an atom, which has a relatively weak bond to the atomic nucleus.

A high-energy photon transfers some of its energy to the electron. The excited electron is released from the atom. The rest of the energy of the original photon is emitted as an X-ray photon of a longer wavelength at some angle to the direction of the primary photon. A secondary photon can ionize another atom, and so on. These changes in the direction and wavelength of X-rays are known as the Compton effect.

Some effects of the interaction of X-rays with matter

As mentioned above, X-rays are able to excite the atoms and molecules of matter. This may cause fluorescence of certain substances (eg zinc sulfate). If a parallel beam of x-rays is directed at opaque objects, then the rays can be observed to pass through the object by placing a screen coated with a fluorescent substance.

The fluorescent screen can be replaced with photographic film. X-rays have the same effect on photographic emulsion as light does. Both methods are used in practical medicine.

Another important effect of X-rays is their ionizing ability. It depends on their wavelength and energy. This effect provides a method for measuring X-ray intensity. When X-rays pass through the ionization chamber, an electric current is generated, the magnitude of which is proportional to the intensity of the X-rays.

Absorption of X-rays by matter

When X-rays pass through matter, their energy decreases due to absorption and scattering. The weakening of the intensity of a parallel beam of X-rays passing through a substance is determined by Bouguer's law: I = I0 e -μd, where I 0- initial intensity of X-ray radiation; I is the intensity of X-rays passing through the layer of matter, d- absorbing layer thickness , μ - linear attenuation coefficient. It is equal to the sum of two quantities: t- linear absorption coefficient and σ - linear scattering coefficient: μ = τ+ σ

In experiments, it was found that the linear absorption coefficient depends on the atomic number of the substance and the wavelength of X-rays:

τ = kρZ 3 λ 3, where k- coefficient of direct proportionality, ρ - the density of the substance, Z is the atomic number of the element, λ is the wavelength of the X-rays.

The dependence on Z is very important from a practical point of view. For example, the absorption coefficient of bones, which are composed of calcium phosphate, is almost 150 times higher than the absorption coefficient of soft tissues ( Z=20 for calcium and Z=15 for phosphorus). When X-rays pass through the human body, the bones stand out clearly against the background of muscles, connective tissue, etc.

It is known that the digestive organs have the same absorption coefficient as other soft tissues. But the shadow of the esophagus, stomach and intestines can be distinguished if the patient ingests a contrast agent - barium sulfate ( Z= 56 for barium). Barium sulphate is very opaque to x-rays and is often used for x-ray examinations of the gastrointestinal tract. Certain opaque mixtures are injected into the bloodstream in order to examine the condition of the blood vessels, kidneys, and the like. In this case, iodine is used as a contrast agent, the atomic number of which is 53.

Dependence of X-ray absorption on Z also used to protect against the possible harmful effects of x-rays. For this purpose, lead is used, the value Z for which is 82.

The use of x-rays in medicine

The reason for the use of X-rays in diagnostics was their high penetrating power, one of the main X-ray properties. In the early days of discovery, X-rays were mainly used to examine bone fractures and locate foreign bodies (such as bullets) in the human body. Currently, several diagnostic methods are used using X-rays (X-ray diagnostics).

Fluoroscopy . An X-ray device consists of an X-ray source (X-ray tube) and a fluorescent screen. After the X-rays pass through the patient's body, the doctor observes a shadow image of the patient. A lead window should be installed between the screen and the doctor's eyes in order to protect the doctor from the harmful effects of x-rays. This method makes it possible to study the functional state of some organs. For example, a doctor can directly observe the movements of the lungs, the passage of a contrast agent through the gastrointestinal tract. The disadvantages of this method are insufficient contrast images and relatively high doses of radiation received by the patient during the procedure.

Fluorography . This method consists of taking a photograph of a part of the patient's body. They are used, as a rule, for a preliminary study of the condition of the internal organs of patients using low doses of X-rays.

Radiography. (X-ray radiography). This is a method of research using x-rays, during which the image is recorded on photographic film. Photographs are usually taken in two perpendicular planes. This method has some advantages. X-ray photographs contain more detail than an image on a fluorescent screen, and therefore they are more informative. They can be saved for further analysis. The total radiation dose is less than that used in fluoroscopy.

Computed X-ray tomography . The computerized axial tomographic scanner is the most modern X-ray diagnostic device that allows you to get a clear image of any part of the human body, including the soft tissues of organs.

The first generation of computed tomography (CT) scanners include a special X-ray tube that is attached to a cylindrical frame. A thin beam of x-rays is directed at the patient. Two x-ray detectors are attached to the opposite side of the frame. The patient is in the center of the frame, which can rotate 180 0 around his body.

An x-ray beam passes through a stationary object. The detectors receive and record the absorption values of various tissues. Recordings are made 160 times while the x-ray tube moves linearly along the scanned plane. Then the frame is rotated by 1 0 and the procedure is repeated. Recording continues until the frame rotates 180 0 . Each detector records 28800 frames (180x160) during the study. The information is processed by a computer, and an image of the selected layer is formed by means of a special computer program.

The second generation of CT uses multiple X-ray beams and up to 30 X-ray detectors. This makes it possible to speed up the research process up to 18 seconds.

The third generation of CT uses a new principle. A wide beam of X-rays in the form of a fan covers the object under study, and the X-ray radiation that has passed through the body is recorded by several hundred detectors. The time required for research is reduced to 5-6 seconds.

CT has many advantages over earlier X-ray diagnostic methods. It is characterized by high resolution, which makes it possible to distinguish subtle changes in soft tissues. CT allows to detect such pathological processes that cannot be detected by other methods. In addition, the use of CT makes it possible to reduce the dose of X-ray radiation received by patients during the diagnostic process.

Introduction

The subject of radiography is the solution of the main problem of structural analysis using X-ray scattering (diffraction). The main task of structural analysis is to determine the unknown microdistribution function of a material object (crystal, amorphous body, liquid, gas). The scattering phenomenon produces a Fourier analysis of the microdistribution function. Using the inverse operation - Fourier synthesis, you can restore the desired microdistribution function. Structural analysis can be used to determine:

a) the periodic atomic structure of the crystal;

b) defects (dynamic and static) of real crystals;

c) short-range order in amorphous bodies and liquids;

d) structure of gas molecules;

e) phase composition of the substance.

The aim of this work is to study the experimental and theoretical methods of X-ray diffraction analysis and their application to determine the parameters of the crystal lattices of bismuth-containing perovskites. The main tasks that were solved in the course of the work were as follows: a literature review on the research topic, studying the basics of X-ray diffraction analysis methods, searching and studying software tools for theoretical calculations, processing experimental X-ray patterns of Nd x Bi 1-x FeO 3, theoretical calculation of X-ray patterns, building unit cells and refinement of their parameters.

The nature of x-rays

X-rays are electromagnetic waves with a relatively short wavelength from 10 -4 to 10 2 A. The refractive index of X-rays differs little from unity. Just like light rays, x-rays can be linearly polarized. A continuous spectrum of X-rays arises from the sharp deceleration of electrons incident on the anode. When an electron decelerates, its kinetic energy E=eU, where e is the charge of the electron, and U is the voltage, can completely transform into the energy of one photon. At the same time or from where

The characteristic spectrum of X-rays arises when the accelerating voltage on the tube is increased. At a certain voltage, determined for each material, the maxima of the linear spectrum appear against the background of the continuous spectrum, which is a characteristic of the anode material. The characteristic spectrum contains lines of several series. For heavy elements, the presence of K-, L-, M-, N-, O- series has been established. The radiation of each series appears in the spectrum only when a certain voltage value is reached, called the excitation potential. The appearance of lines of the characteristic spectrum is due to the transitions of electrons to the inner shells of atoms. So the transition of electrons from the L to the K shell leads to the appearance of K b1 and K b2 lines, and the transition from M to K - K in -lines.

Crystal structure and diffraction

A crystal is a discrete three-dimensional periodic spatial system of particles. Macroscopically, this manifests itself in the homogeneity of the crystal and its ability to self-cut into flat faces with strictly constant dihedral angles. Microscopically, a crystal can be described as a crystal lattice, i.e. a correctly periodically repeating system of points (centers of gravity of the particles that make up the crystal), described by three non-coplanar axial translations and three axial angles (Fig. 1).

Rice. one

Distinguishing translations equal and unequal in absolute value, equal, unequal, direct indirect axial angles, it is possible to distribute all crystal lattices over seven crystal systems (syngonies) as follows:

Triclinica?b?cb?c?d?90 0

Monoclinica?b?cb=r= 90 0 c?90 0

Rhombic a? b? cb \u003d c \u003d d \u003d 90 0

Trigonala=b=sat=v=d? 90 0

Tetragonal a \u003d b? sb \u003d c \u003d d \u003d 90 0

Hexagonala=b?sb=v=90 0 r= 120 0

Cubic a=b=sb=v=g= 90 0

However, if translational symmetry is taken into account, then 14 translational groups arise, each of which forms a Bravais lattice.

The Bravais lattice is an infinite system of points formed by the translational repetition of one point. Any crystal structure can be represented by one of the 14 Bravais lattices. At low nucleation and growth rates, large single single crystals arise. Example: minerals. At high speeds, a polycrystalline conglomerate is formed. Example: metals and alloys. The long-range order inherent in crystals disappears in the transition to amorphous bodies and liquids, in which there is only short-range order in the arrangement of particles.

An experimental study of the arrangement of atoms in crystals became possible only after the discovery by Roentgen in 1895 of X-rays. In order to check whether this radiation was indeed a type of electromagnetic radiation, Laue in 1912 advised Friedrich and Knipping to pass an X-ray beam through a crystal and see if a diffraction pattern would appear. The experience has been positive. The experiment was based on an analogy with the well-known phenomenon of diffraction in ordinary optics. When a beam of light passes through a series of small holes separated from each other by distances comparable to the wavelength of light, an interference (or, in this case, the same, diffraction) pattern of alternating light and dark areas is observed on the screen. Similarly, when X-rays, whose wavelength is comparable to the distances between the atoms of a crystal, are scattered by these atoms, a diffraction pattern appears on the photographic plate.

The essence of the phenomenon of diffraction is explained in Fig. 2, which shows plane waves incident on a series of scattering centers. Under the action of the incident beam, each such center emits spherical waves; these waves interfere with each other, which leads to the formation of wave fronts propagating not only in the direction of the original incident beam, but also in some other directions.

Fig.2

The so-called Laue diffraction pattern (Lauegram), obtained when an X-ray beam passes through a thin crystalline plate of the beryl mineral, is shown in Fig. 3.

Rice. 3

The diffraction pattern shows the presence of a rotational axis of symmetry of the 6th order, which is typical for a hexagonal crystal structure. Thus, this picture carries important information about the structure of the crystal on which diffraction occurs, which was, in particular, the subject of research by W. Bragg and his son W. Bragg.

Based on the phenomenon of X-ray diffraction, father and son Braggy created an extremely valuable experimental method for X-ray diffraction analysis of crystals. Their work marks the beginning of the development of the foundations of modern X-ray diffraction analysis. Sophisticated automated equipment is now commonplace in solid state physics laboratories. Thanks to X-ray machines and computers, determining the arrangement of atoms, even in a complex crystal, has become almost a chore.

The advantage of X-ray diffraction analysis is its high selectivity. If a monochromatic X-ray beam is incident in an arbitrary direction on a single crystal, one can observe the emerging (but not diffracted) beam in the same direction. Diffracted beams appear only at several strictly defined (discrete) angles of incidence relative to the crystallographic axes. This condition underlies the method of crystal rotation, in which the rotation of a single crystal about a certain axis is allowed, and the directions for which diffraction is observed are precisely determined.

Other experiments may use powdered crystalline samples and a monochromatic beam; - this method is called Debye - Scherrer. In this case, there is a continuous spectrum of orientations of individual crystallites, but sufficiently intense diffracted beams give only crystallites with a certain orientation. The powder method does not require the growth of large single crystals, which is its advantage over the Laue and crystal rotation methods. The Laue method uses a single crystal and an X-ray beam that has a continuous spectrum, so that the crystal itself chooses the appropriate wavelengths for the formation of diffraction patterns.

X-rays are electromagnetic waves whose electric fields interact with charged particles, namely electrons and atoms of a solid body. Since the mass of electrons is much less than the mass of the nucleus, X-rays are effectively scattered only by electrons. Thus, the X-ray pattern provides information about the distribution of electrons. Knowing the directions in which the radiation diffracted, one can determine the type of crystal symmetry or crystal class (cubic, tetragonal, etc.), as well as the lengths of the sides of the unit cell. The relative intensity of the diffraction maxima can be used to determine the position of atoms in the unit cell.

In essence, the diffraction pattern is a mathematically transformed picture of the distribution of electrons in a crystal - its so-called Fourier image. Consequently, it also carries information about the structure of chemical bonds between atoms. The intensity distribution in one diffraction peak provides information about lattice defects, mechanical stresses, and other features of the crystal structure.

Although X-ray diffraction analysis is the oldest method for studying solids at the atomic level, it continues to develop and improve. One of these improvements is the use of electron accelerators as powerful sources of x-rays - synchrotron radiation. The synchrotron is an accelerator commonly used in nuclear physics to accelerate electrons to very high energies. Electrons create electromagnetic radiation ranging from ultraviolet to X-rays. In combination with the developed solid-state particle detectors, these new sources are expected to provide many new detailed information about solids.

In research in the field of solid state physics, diffraction is used not only for X-rays, but also for electrons and neutrons. The possibility of electron and neutron diffraction is based on the fact that a particle moving at a speed v behaves like a wave with a de Broglie wavelength l = h/mv, where h is Planck's constant, m is the mass of the particle. Since the electrons are charged, they interact intensely with the electrons and nuclei of the solid. Therefore, unlike X-rays, they penetrate only into a thin surface layer of a solid. But it is precisely this limitation that makes them very suitable for studying precisely the surface properties of a solid. Neutrons were discovered in 1932. Four years later, their wave nature was confirmed by diffraction experiments. The use of neutrons as a means of studying solids became possible after the creation of nuclear reactors, in which, starting from about 1950, neutron flux densities of the order of 10 12 neutrons/cm 2 ·s were created. Modern reactors provide flows thousands of times more intense. Neutrons, being neutral particles, interact only with the nuclei of a solid body (at least in non-magnetic materials). This property is significant for a number of reasons. Since nuclei are extremely small compared to the size of an atom, and the interaction between nuclei and incident neutrons is short-range, the neutron beam has a high penetrating power and can be used to study crystals up to several centimeters thick. In addition, neutrons are intensively scattered by the nuclei of both heavy and light elements. In contrast, X-ray radiation is scattered by electrons, and therefore for it the scattering power of atoms increases with an increase in the number of electrons, i.e. the atomic number of the element. Consequently, the position of atoms of light elements in a crystal can be determined much more accurately by neutron rather than x-ray diffraction.

The method of producing X-rays clearly indicates that their formation is associated with stopping (or braking) fast-flying electrons. A flying electron is surrounded by electric and magnetic fields, because a moving electron is a current. Stopping (deceleration) of an electron means a change in the magnetic field around it, and a change in the magnetic or electric field causes (see § 54) the emission of electromagnetic waves. These electromagnetic waves are observed in the form of X-rays.

Roentgen already had such an idea of X-rays (although other researchers defended it more insistently). To establish the wave nature of X-rays, it was necessary to make experiments, but their interference or diffraction. However, the implementation of such experiments turned out to be a very difficult task, and the solution to the problem was obtained only in 1912, when the German physicist Max Laue (1879 - 1960) proposed using a natural crystal as a diffraction grating, in which the atoms are arranged in the correct order at a distance of the order of each from a friend (see Vol. I, § 266).

Experience performed by W. Friedrich. P. Knipping and Laue, was carried out as follows. A narrow beam of X-rays, isolated with the help of lead diaphragms 2, 3 (Fig. 304), fell on crystal 4. An image of the beam trace was obtained on a photographic plate 5. In the absence of a crystal, the image on the plate was a dark spot - a trace of the beam transmitted by the diaphragms. When a crystal was placed in the path of the beam, a complex pattern was obtained on the plate (Fig. 305), which is the result of X-ray diffraction on a crystal lattice. The picture obtained not only gave direct evidence of the wave nature of X-rays, but also made it possible to draw important conclusions about the structure of crystals, which determine the form of the observed diffraction pattern. At present, the use of X-rays to study the structure of crystals and other bodies has acquired enormous practical and scientific significance.

Rice. 304. Arrangement in the first experiments on the observation of X-ray diffraction: 1 - X-ray tube, 2, 3 - lead diaphragms emitting a narrow beam of X-rays, 4 - crystal in which diffraction occurs, 5 - photographic plate

Rice. 305. Photograph depicting the X-ray diffraction pattern in a zinc blende crystal

Further improvements made it possible, with the help of careful experiments, to determine the wavelengths of x-rays. The radiation of an ordinary X-ray tube turned out to be, like white light, containing waves of various lengths with an average value from hundredths to tenths of a nanometer, depending on the voltage between the cathode and anode of the tube. Subsequently, X-ray waves with a length of several tens of nanometers were obtained, i.e. longer than the shortest known ultraviolet wavelengths. It was also possible to obtain and observe very short waves (the length of which is thousandths and ten thousandths of a nanometer).

By determining the wavelengths of X-rays, it was possible to establish that the waves are absorbed the less, the shorter they are. Roentgen called weakly absorbed rays hard. Thus, an increase in hardness corresponds to a decrease in wavelength.

The rays, which are now called X-rays, were discovered on November 7, 1895 by the physicist V.K. Roentgen. The official date of the discovery of these rays is December 28, 1895, when Roentgen, after studying the X-rays discovered by him, published the first report on their properties.

These X-rays began to be called X-rays from January 23, 1896, when V.K. Roentgen made a public report on X-rays at a meeting of the Physico-Medical Society. At this meeting, it was unanimously decided to call X-rays X-rays.

The nature of X-rays remained little studied for 17 years from the date of their discovery by VK Roentgen, although soon after the discovery of these rays, the scientist himself and a number of other researchers noted their similarity with visible rays.

The similarity was confirmed by the straightness of propagation, the absence of their deviation in electric and magnetic fields. But, on the other hand, it was not possible to detect either the phenomenon of refraction by a prism, or reflection from mirrors, and a number of other properties characteristic of visible light, which has a wave nature.

And only in 1912, initially our compatriot, the famous Russian physicist A. I. Lebedev, and then the German physicist Laue, managed to prove that X-rays have the same nature as the rays of visible light, i.e., they are electromagnetic waves. Thus, X-rays are inherently the same as radio waves, infrared rays, visible light rays, and ultraviolet rays.

The only difference between these beams is that they have different wavelengths of electromagnetic oscillations. Among the above X-rays have a very short wavelength. Therefore, they required special conditions for the production of experience to reveal refraction or reflection.

The wavelength of X-rays is measured in a very small unit called "angstrom" (1Å = 10–8 cm, that is, equal to one hundred millionth of a centimeter). In practice, diagnostic devices produce rays with a wavelength of 0.1–0.8 Å.

Properties of x-rays

X-rays pass through opaque bodies and objects, such as, for example, paper, matter, wood, tissues of the human and animal body, and even through metals of a certain thickness. Moreover, the shorter the wavelength of radiation, the easier they pass through the listed bodies and objects.

In turn, when these rays pass through bodies and objects with different densities, they are partially absorbed. Dense bodies absorb X-rays more intensely than low-density bodies.

X-rays have the ability to excite the visible glow of certain chemicals. For example: crystals of platinum-cyanide barium, when X-rays hit them, begin to glow with a bright greenish-yellowish light. The glow continues only at the moment of exposure to X-rays and immediately stops with the cessation of irradiation. Barium platinum cyanide thus fluoresces under the action of X-rays. (This phenomenon led to the discovery of x-rays.)

When illuminated with X-rays, calcium tungsten also glows, but with blue light, and the glow of this salt continues for some time after the cessation of irradiation, i.e. phosphorescent.

The property of causing fluorescence is used to produce translucence using x-rays. The property of causing phosphorescence in some substances is used to produce x-rays.

X-rays also have the ability to act on the photosensitive layer of photographic plates and films like visible light, causing the decomposition of silver bromide. In other words, these rays have a photo-chemical effect. This circumstance makes it possible to produce images using X-rays from various parts of the body in humans and animals.

X-rays have a biological effect on the body. Passing through a certain part of the body, they produce corresponding changes in tissues and cells, depending on the type of tissue and the amount of rays absorbed by them, i.e., the dose.

This property is used to treat a number of human and animal diseases. When exposed to large doses of X-rays in the body, a number of functional and morphological changes are obtained, and a specific disease occurs - radiation sickness .

X-rays, in addition, have the ability to ionize the air, that is, to split the constituent parts of the air into separate, electrically charged particles.

As a result, air becomes an electrical conductor. This property is used to determine the amount of X-rays emitted by an X-ray tube per unit of time using special instruments - dosimeters.

Knowing the radiation dose of the x-ray tube is important when x-ray therapy is performed. Without knowledge of the radiation dose of the tube with appropriate rigidity, it is impossible to carry out treatment with X-rays, since it is easy to worsen the entire process of the disease instead of improving. Improper use of x-rays for treatment can destroy healthy tissue and even cause serious damage throughout the body.

X-ray diagnostics is based on the use of the remarkable property of X-rays to penetrate through the opaque tissues of the body. This makes it possible to see during the life of the animal what is inaccessible to the eyes - morphological and functional changes in various internal organs.

It is not for nothing that an x-ray study is rightly called “lifetime autopsy without a knife” or “lifetime pathological anatomy”. X-ray normal and pathoanatomical picture, of course, is unique and in many respects does not resemble the picture that we observed during the autopsy of dead animals.

Therefore, a veterinarian performing X-ray examination of animals must be well aware of the normal X-ray picture, both species and age. Only under this condition can he find and distinguish between certain pathological changes and correctly evaluate them.

The value of X-ray examination in the most diverse diseases in animals, especially in diseases of the internal organs, is very great.

In some cases, an X-ray examination clarifies and supplements the clinical diagnosis, in others it is the main method by which only one can determine the disease, and thirdly, it is of great help in differential diagnosis. For example, a sign of illness - vomiting during or immediately after eating in dogs and gradual emaciation are common in many diseases of the gastrointestinal tract.

These signs have to be observed with partial obstruction of the thoracic esophagus, with stomach ulcers, with idiopathic esophageal dilatation and with diverticula of the esophagus. X-ray examination immediately becomes clear the main cause of the disease.

X-ray diagnostics is carried out in two ways: fluoroscopy and radiography.

Fluoroscopy- this is such a method of X-ray examination, in which changes in various organs are determined according to the shadow X-ray image obtained on a luminous screen.

Radiography- this is such a method of X-ray examination, when changes in various organs are determined according to the shadow X-ray image obtained on a photosensitive film.

Despite its enormous advantages, X-ray diagnostics cannot in any way replace other diagnostic methods, especially clinical examination. X-ray diagnostics to a large extent complements other research methods with objective pathological and anatomical data of the disease and thus contributes to a faster diagnosis. In some cases, it protects clinicians from possible and inevitable errors in the diagnosis, and sometimes reveals changes that could not be detected clinically.

However, it must be borne in mind that, like other research methods, X-ray diagnostics has its own advantages and disadvantages. Along with the x-ray picture, characteristic of a particular pathological process, or even pathognomonic, in the study, almost the same x-ray image is found in various diseases. So, for example, a lung tumor, an increase in bifurcation lymph nodes, and a blockage in the thoracic esophagus, when coinciding in place with the bifurcation area on the screen or radiograph, are difficult to differentiate. The same happens with pneumonia and diaphragmatic hernia, if you do not see the patient and do not examine him clinically.

Therefore, any x-ray examination should always be preceded by a careful collection of anamnestic data and a comprehensive thorough clinical examination. The final diagnosis is always required when comparing the data of all research methods.

Based on all this, X-ray examination, as a very important method, should neither be underestimated nor overestimated.

This section of this book deals with a number of general issues of X-ray diagnostics, characterizing the methods and capabilities of X-ray studies, as well as low-power X-ray machines suitable for examining dogs.

The nature of x-rays

The wavelength of X-rays is measured in a very small unit called "angstrom" (1Å = 10 -8 cm, that is, equal to one hundred millionth of a centimeter). In practice, diagnostic devices produce rays with a wavelength of 0.1–0.8 Å.

Properties of x-rays

In turn, when these rays pass through bodies and objects with different densities, they are partially absorbed. Dense bodies absorb X-rays more intensely than low-density bodies.

When illuminated with X-rays, calcium tungsten also glows, but with blue light, and the glow of this salt continues for some time after the cessation of irradiation, i.e. phosphorescent.

The property of causing fluorescence is used to produce translucence using x-rays. The property of causing phosphorescence in some substances is used to produce x-rays.

X-rays, in addition, have the ability to ionize the air, that is, to split the constituent parts of the air into separate, electrically charged particles.

As a result, air becomes an electrical conductor. This property is used to determine the amount of X-rays emitted by an X-ray tube per unit of time using special instruments - dosimeters.

X-ray methods

a) Transillumination (fluoroscopy). X-rays in veterinary practice are used to study and recognize various diseases in farm animals. This method of studying sick animals is an auxiliary tool for establishing or clarifying the diagnosis, along with other methods. Therefore, the data of x-ray examination should always be linked with the data of clinical and other studies. Only in this case can we come to a correct conclusion and an accurate diagnosis. As mentioned above, there are two methods of X-ray examination: the first method is transillumination or fluoroscopy, the second method is the production of x-rays or radiography.

Let us dwell on the question of the substantiation of transillumination, the possibilities of this method, its advantages and disadvantages.

In order to produce translucence with invisible X-rays and obtain a visible shadow picture of the body area under study, certain properties of X-rays and body tissues are used.

1. The ability of X-rays to: a) penetrate body tissues, and b) cause the visible glow of certain chemicals.

2. The ability of tissues to absorb X-rays to some extent, depending on their density.

As already mentioned, X-rays have a very short wavelength of electromagnetic oscillations, as a result of which these rays have a penetrating ability through opaque bodies, in contrast to visible light. But in order for the X-rays that have passed through the area of the body to be examined give a visible image, special screens are used for transillumination. They are arranged as follows: they usually take white cardboard measuring 30 X 40 cm (sometimes smaller) and on one side of it a layer of a chemical is applied, which, when X-rays hit it, is capable of producing visible light. The most commonly used platinum-cyanogen barium. When x-rays hit this substance, it begins to glow with a visible yellowish-greenish light. It must be emphasized that crystals of platinum-cyanogen barium glow here as a result of exposure to X-rays, but not the X-rays themselves. They still remain invisible and, having passed through the screen, spread further. The screen has the property to glow the brighter, the more x-rays hit it.

On the other hand, the screen glows only at the moment of exposure to X-rays. As soon as the supply of X-rays to the screen stops, it stops glowing. Thus, a screen made of barium platinum-cyanogen has the ability to fluoresce. Therefore, a screen for translucence or a translucent screen is called a fluorescent screen.

In contrast to translucent screens used in radiology, other screens are capable of phosphorescence. They are used for the production of images and are called intensifying. These screens will be discussed in more detail below.

If now between the X-ray tube and the translucent screen we put some object or place some part of the animal's body, then the rays, having passed through the body, will fall on the screen. The screen will begin to glow with visible light, but not equally intense in its various parts. This is because the tissues through which the x-rays have passed have different density or specific gravity. The higher the density of the tissue, the more it absorbs X-rays and, conversely, the lower its density, the less it absorbs the rays.

As a result, the same number of rays travel from the X-ray tube to the object under study over the entire surface of the illuminated area of the body. Having passed through the body, from its opposite surface, a much smaller amount of x-rays comes out, and their intensity in different areas will be different. This is due to the fact that, in particular, bone tissue absorbs rays very strongly compared to soft tissues. As a result of this, when X-rays that have passed through the body in an unequal number hit the screen, we will have different intensity or degree of luminescence of individual sections of the screen. The areas of the screen where the bone tissue is projected will either not glow at all, or very weakly. This means that the rays do not reach this place as a result of their absorption by the bone tissue. This is how the shadow is made.

The same areas of the screen where soft tissues are projected glow brighter, since soft tissues retain a small amount of X-rays that have passed through them, and more rays will reach the screen. Thus, soft tissues, when translucent, give partial shade. And finally, areas of the screen that are outside the border of the object under study glow very brightly. This is due to the hit of rays that passed by the object under study and were not delayed by anything.

As a result of transillumination, thus, we get a differentiated shadow picture of the area of the body under study, and this differentiated picture on the screen is obtained from the different transparency of tissues in relation to X-rays.

To save the screen from mechanical damage, it is placed in a wooden frame with two handles. When assembled, the translucent screen consists of the following parts, when viewed from behind.

The first layer is a thin celluloid or plastic plate to protect the screen from mechanical damage.

The second layer is the translucent screen itself, that is, that cardboard rectangle, which is coated on one side with platinum-cyanogen barium. The back side of the screen adjoins a protective plastic plate.

The third layer is leaded glass 5–6 mm thick. This glass serves to protect the working surface of the cardboard screen (fluorescent layer), on the other hand, it is a means of protecting the radiologist from getting x-rays on it. All this is reinforced in a wooden frame. In this form, the screen is used for work.

Translucence of both humans and animals is carried out in a completely darkened room. The need for dimming follows from the following considerations: firstly, the luminous intensity of a translucent screen is much weaker than both daylight and electric lighting. Therefore, the image received on the screen is interrupted by daylight and our eye does not catch this image. And it does not catch because our pupils are sharply constricted, and the number of rays emanating from the screen is not able to cause light irritation compared to daylight.

Secondly, in order to detect various pathological changes, it is necessary to train the eye to see subtle changes in tissues and organs, which sometimes give very weak and delicate shadows. These changes can only be seen when the pupils are maximally dilated in the dark and the eye is able to perceive these weak light stimuli. In order for the eyes to become accustomed to distinguishing small details of the shadow picture, it is necessary to stay in the dark before the start of translucence from 5 to 10 minutes, depending on the person. Some adapt faster, others slower.

When translucent, the translucent screen is applied to the surface of the animal's body with the back side, and the front side (with lead glass) should be facing the radiologist.

The x-ray tube is placed on the opposite side of the animal's body. The tube should be in such a position that the hole for the exit of x-rays was directed towards the object under study and the screen (Fig. 162).

Rice. 162. Transillumination of the chest of a dog

The distance from the tube to the screen should be such that the cone of rays illuminates almost the entire screen measuring 30X40 cm. In practice, this distance is 60–65 cm. divergent X-rays illuminated only this area. This is achieved by reducing the distance between the tube and the screen, or by choosing an appropriate sheath size.

It must be remembered that when the distance between the screen and the tube doubles, the illuminated area quadruples, and the degree of screen luminescence decreases by a factor of four, and vice versa. When this distance is reduced by 2 times, the illumination area decreases by 4 times and the screen glow increases by the same amount.

In the production of translucence of various parts of the body in animals on the screen, we observe the most diverse shadow picture.

Transillumination of the extremities gives the simplest shadow image, since the density of tissues in these areas has a large difference between them. On the one hand, there is very dense bone tissue, on the other hand, the soft tissue surrounding it has a much lower and uniform density. When translucent, thus, a dense shadow of the bone and a uniform penumbra of soft tissues are obtained (Fig. 163).

Rice. 163. X-ray in the area of the knee joint of a dog

Transillumination of the head gives a complex shadow pattern, where the shadows of individual sections of bones of varying intensity are mixed with the shadows of soft tissues, and the pattern is heterogeneous (Fig. 164). Separate, more intense stripes of bones on the general background of the pattern have different directions. In order to understand this complex interweaving of shadows, it is necessary to know not only normal anatomy, but also normal X-ray anatomy, that is, the X-ray picture of this part of the body in healthy animals. And only in this case it will be possible to judge the presence of pathological changes in the x-ray picture.

Rice. 164. X-ray from the head of a dog

We get the most complex shadow pattern on the screen when transilluminating the chest (Fig. 165).

Rice. 165. X-ray of the lungs of a dog in the chest position

When transilluminating the lungs, the screen is placed on one side of the chest, and the tube is on the opposite side. Therefore, the image of the total shadow pattern from the object, which has a significant thickness, is obtained on the screen. But since almost the entire bulk of the fabric has a low density, with the exception of the ribs, the shadow pattern on the screen is very delicate, openwork, with many different intensities of penumbra. This pattern is created both by the lung tissue and by the interlacing of the vascular-bronchial branches. It is even more difficult to understand this drawing. You need to have a lot of experience to establish the presence of subtle structural changes in the lung tissue.

What are the advantages and disadvantages of this research method?

The main advantage of transillumination in the study of sick animals is the fact that we can see in a living animal those changes in tissues or organs that cannot be established by external examination.

The second advantage is the ability to follow the work of individual internal organs in dynamics, in particular, the lungs, heart, intestines, during the production of transillumination on a living animal.

Thirdly, this research method is painless, fast, and does not cause discomfort to the patient.

The main disadvantage of transillumination is the absence of an objective document, except for a record of the results of the study produced by the radiologist.

The second disadvantage should be considered the need to work only in a darkened room. This makes it difficult to observe the behavior of the animal during the study. Always be on the lookout for distracting radiologists from the screen.

In order to have a correct idea of the shadow picture of an x-ray image, it is necessary to dwell on some points of the projection laws in x-ray examination.

It must be remembered that the closer the tube is to the object, the larger the shadow on the screen will be. This is because the x-rays come from a narrow section of the anode plate and diverge in the form of a wide cone. As a result of this, the shadow of the translucent object will be much larger than the true size.

The farther we move the tube from the object under study with the screen, the more the shadow will decrease and approach the true size, since the farther the tube, the more parallel the rays passing through the object.

The second position is no less important. The closer an object is to the screen, the smaller, denser and sharper its shadow. And, conversely, the farther the screen is from the object, the larger its shadow will be, less clear and dense. For this reason, even during transillumination, it is necessary to bring the screen close to the surface of the body, otherwise we will not get a clear image of the shadow pattern of the area under study.

When transilluminating, it is also important to position the tube relative to the screen so that the central beam falls perpendicular to the screen surface. This will give the most correct shadow image of the area under study. If this rule is not observed, the image of the true picture is distorted and will give an idea of the presence of a pathology, although there is none. When translucent (head, neck, torso), it is necessary to attach the screen to the body of the animal from the diseased side, and install an X-ray tube on the opposite side. Thus, the above areas of the body will be translucent during the course of the rays from left to right or vice versa from right to left, depending on the localization of the disease process. Less often it is necessary to shine through the limbs of animals; they take pictures more often.

b) X-rays (radiography). For the production of radiography, in addition to the above properties of x-rays, the ability of these rays to cause a photochemical effect on a photosensitive emulsion is used.

We now know that for translucence it is required to have a darkened room and a screen for translucence. On this screen, when transilluminated, we see a positive image of the translucent part of the body. The possibility of obtaining a differentiated shadow pattern in this case is explained by the different degree of absorption of X-rays by the tissues and, therefore, the different brightness of the glow of individual sections of the screen for transillumination.

In order to take an x-ray, we must have instead of a translucent screen - x-ray film, x-ray cassettes and paired intensifying screens. Moreover, unlike transillumination, the images are taken without darkening the X-ray room..

X-ray film is very sensitive to visible light, so it is stored in special cardboard boxes that do not transmit visible light. The film is packed into these boxes at the factory where it is produced. Typically, a box of any size contains 20 pieces of films. Between each film there is a gasket made of black or tissue paper.

At present, our industry produces two types of x-ray film - "X" type and "XX" type film. The first type of film is designed for shots with special intensifying screens, the second - for shots without them.

What are intensifying screens and what is their purpose, will be discussed later.

Factories produce both types of films in standard sizes: 13X18 cm, 18X24, 24X30 and 30X40 cm. The films are packed in boxes.

Unlike photographic film, X-ray film is double-sided, i.e., the photosensitive layer is applied both on one side and on the other. The composition of the photosensitive layer includes gelatin and silver bromide. The basis of the film is a celluloid plate.

As already mentioned, the production of x-rays does not require darkening the room. Therefore, the film must be protected from visible light. For this purpose, there are special x-ray cassettes. The industry produces cassettes in the same standard sizes as films.

The cassette is a flat metal box. Its front wall is shiny and consists of an aluminum plate 1 mm thick. The back wall is painted black and consists of a thick iron plate. The rear wall is attached to the cassette on one side with hinges, and on the other - with two latches. By pressing the latch buttons, the cassette can be opened. The entire interior of the cassette is painted black so that the walls are not reflective to visible light.

There is a recess on the side of the front wall in the cassette, and on the inside of the back cover there is a felt pad, which, when the cassette is closed, enters the recess in the front wall of the cassette. Such a device prevents visible light from entering inside it.

The front wall of the cassette freely transmits X-rays, while the back wall delays them.

Before taking the picture, the cassette is loaded with x-ray film in a special photo room, under red light. Moreover, the cassette must be taken the same size as the film. In this case, the film completely occupies the recessed area of the cassette.

The cassette is loaded as follows: a box with films of the required size is opened, the cassette is opened, one film is pulled out of the box and placed in the recess of the cassette, then the cassette is closed. In this form, a loaded cassette can be brought into the light. In the cassette, the film is reliably protected from visible light.

In order to take a picture, the X-ray tube, the object and the loaded cassette must be properly positioned. Their mutual arrangement is the same as during transillumination. Only instead of a translucent screen, a charged cassette is applied with its front side to the part of the body being removed.

In the process of taking a picture, which lasts either a fraction of a second or several seconds, depending on the thickness of the object, we will not see any image, since X-rays are invisible, and on the other hand, there is no screen here.

When taking a picture, X-rays, having passed through the body and the front wall of the cassette, act on the double-sided X-ray film, causing corresponding changes in its light-sensitive layers. Silver bromide molecules undergo changes under the action of X-rays. Silver bromide turns into subbromide. Since the number of rays that hit different parts of the film will be different, the amount of subbromide silver on them will also be different. Moreover, in those areas where more rays hit, there will be more of it; on the same, where fewer rays hit, less.

These changes are not visible to the eye, and if after the picture the x-ray film is removed from the cassette in the photo room, then the film will be exactly the same as before the picture, i.e., a latent image of the area being filmed is obtained on the film. To make the resulting image visible, the removed film must be processed in a special way - this will be discussed later.

In order to reduce exposure in x-rays, so-called intensifying screens. Intensifying screens, unlike translucent ones, are paired. They are produced in the same standard sizes as the film (13X18; 18X24; 24X30; 30X40 cm).

Intensifying screens are cardboard rectangles of the indicated dimensions. One side of the cardboard has a layer of calcium tungsten. This side of the screen is smooth and shiny. This screen must be handled with care, not bent, as the luminous layer is fragile. When X-rays hit such a screen, it glows with a bluish light. Moreover, with prolonged action, the screen glows even after the X-rays stop hitting it.

These paired intensifying screens are inserted into an appropriately sized X-ray cassette. One of the paired screens is thinner, the other is 2–3 times thicker. This means that the luminous layer of one of them is thinner than that of the other. The thickness of the cardboard in both screens is the same. To put these screens in the cassette, open it. A thin screen is placed in the recess of the front wall with the shiny side up, then X-ray film is placed on it. A thicker screen is placed on the film with the shiny side down - to the film, and then the back wall of the cassette is closed. Thus, a cassette with intensifying screens is loaded with a film (Fig. 166).

Rice. 166. X-ray cassette with intensifying screens

The thin screen is called in front of him, but thick rear. In order not to confuse them and not to put them into the cassette vice versa, on the reverse side of each screen there is a corresponding inscription: “front”, “rear”.

Quite legitimate questions arise: why are two intensifying screens required? Why is the front thinner and why are they reinforcing?

This device has one goal - to reduce exposure time when taking a picture.

Two intensifying screens are required because they act by visible light, which is unable to penetrate the thick emulsion layer. Therefore, each screen acts with its glow, caused by X-rays, only on the side of the film layer with which it is located. And since the film is double-sided, in order to obtain the same intensity pattern on both sides of the film, it is necessary to have two intensifying screens in the cassette.

They are called intensifying because their visible glow greatly increases the light effect of X-rays on the film. Modern intensifying screens have such an intensity of luminescence that they increase the light effect on the film up to 20 times on average. Special screens amplify even up to 40 times. This means that if it takes 10-20 seconds to take a picture of any part of the body on a cassette without intensifying screens, then using these screens, we can reduce the shutter speed when taking a picture to 0.5-1 second or less.

It should be noted that the different thicknesses of the front and rear intensifying screens also have a certain ground under them. This takes into account the property of the screens themselves to absorb a certain amount of X-rays that have passed through them.

If we assume that the thickness of the front and rear intensifying screens is the same, then as a result of the absorption of a certain number of rays by the front screen, a smaller number of rays will fall on the rear screen. And if this is so, then its glow will be weaker and the pattern on the photosensitive layer on this side of the film will be paler. It is not profitable. When the thickness of the luminous layer of the rear screen is 2 times greater, then this screen will glow the same as the front one, even if the number of rays falling on its surface is 2 times less.

A greater glow of the rear screen is obtained due to a greater amount of luminous, from the action of X-rays, calcium tungsten.

X-ray studies using contrast agents

When X-ray examination of various parts of the animal's body, where, along with soft tissues, there is bone tissue, a natural differentiated shadow picture of the X-ray pattern of this area is created.

Bones give a dense shadow, as they absorb a significant amount of X-rays passing through it. Soft tissues absorb less rays and create shadows of less density. Therefore, against the background of the shadow of soft tissues, the shadow of the bone stands out well. Because of this, to detect bone pathology, there is no need to resort to the creation of artificial contrast.

When examining areas of the body where all surrounding tissues and organs have approximately the same density, it is practically impossible to distinguish the boundaries of some organs from others and detect changes in them. In particular, this applies to all organs of the abdominal cavity (liver, stomach, intestines, daughters, bladder, etc.).

In search of means to overcome this obstacle, the idea arose of creating an artificial contrast of individual organs under study, i.e., the idea arose of using various substances in radiological practice that create an artificially significant difference in density between the tissues and organs under study and the surrounding tissues.

Currently, a wide variety of artificial contrast agents are widely used to study various organs. All of them can be divided into two groups: low atomic weight contrast agents and high atomic weight contrast agents.

Creation of contrast by substances with low atomic weight based on the pushing back or straightening of individual organs. Due to this, the total thickness of all tissues in the area where such a contrast agent is located will be less compared to the surrounding tissues. X-rays in this area will be absorbed to a lesser extent, and this place will stand out more sharply (lighter areas).

High atomic weight contrast agents on the contrary, they create a contrast image of an organ or individual parts of an organ due to their significantly greater ability to absorb X-rays than the surrounding tissues. As a result, those organs and tissues in which such contrast agents are located will stand out against the general background of surrounding tissues (darker areas).

To contrast agents of the first group include: air, oxygen. These contrast agents are usually injected into natural cavities to expand them or to push back tissues that interfere with the study.

In the practice of X-ray diagnostics in dogs, these contrast agents are used to study: 1) the liver by introducing a certain amount of air into the stomach; 2) kidneys, spleen, liver by introducing air or oxygen into the abdominal cavity, and in the study of the kidneys by introducing air or oxygen into the perirenal parenchyma.

The method of dosed pneumatization of the stomach for the study of the liver is as follows: after a 12-hour starvation diet, an esophageal probe is inserted into the stomach, at the front end of which a thin rubber bladder is fixed with a thread or rubber glue, a rubber pear is attached to the opposite end of the probe to inject air.

Air is pumped into the stomach under control on a translucent screen. At the moment when the balloon with air completely fills the stomach and the shadow of the liver will stand out clearly against a very light background of the distended stomach at the back and on the light lung field in front, further air injection is stopped and the pear valve is closed (Fig. 167).

Rice. 167. Pneumoperitonium in a dog

In case of anxiety of the animal caused by excessive distension of the stomach, it is necessary to release part of the air through the valve. In this way, it is possible to establish the dose of air that the animal can comfortably tolerate.

This research technique can detect an increase in the liver, a change in the configuration of the posterior surface of the liver as a result of a number of pathological processes, tumors of the liver and diaphragm.

Method of administration of gaseous contrast medium into the abdominal cavity to study its individual organs or pneumoperitoneum is as follows:

For 1-2 days, the dog's diet is reduced and a laxative is given. On the day of the study, do not feed and do a deep enema. The most convenient place for a puncture of the abdominal wall in order to introduce air or oxygen is a hungry hole. The puncture site is prepared according to all the rules of surgery (hair removal, skin disinfection). It is better to disinfect the skin with alcohol-formalin.

When punctured, they take a needle for taking blood, a rubber tube 60–80 cm long with a filter mounted in the middle (a glass canister with sterile cotton), an injection pump. The sterilized needle is connected to one end of the rubber tube with a filter. The pump is attached to its other end.

The dog is fixed in a lateral position and the abdominal wall is punctured with a needle. When puncturing, it is necessary to monitor the moment the end of the needle enters the abdominal cavity. This moment is determined by the gentle characteristic crunch felt by the hand during a puncture. The needle should not be inserted too deeply to avoid puncture of the intestinal wall.

Then proceed to pumping air with a pump with smooth movements. The pumped air goes into the abdominal cavity without much resistance. The degree of filling of the abdominal cavity is determined by the filling of the hungry fossa. As soon as the wall of the hungry fossa begins to spring somewhat when pressed, the amount of air is usually sufficient to push the intestines out. The final check of the degree of squeezing out of the intestine in them is carried out under the screen during transillumination. To do this, without pulling out the needle, the dog is raised to its feet and placed under the screen. When translucent, it is immediately clear whether enough air has been introduced. If it is not enough, then they pump it up. After that, the needle is removed, and the puncture site is treated with tincture of iodine. Instead of air, oxygen can be introduced into the abdominal cavity. For this purpose, oxygen devices designed for inhalation or subcutaneous administration of oxygen are used. In this case, having adjusted the slow flow of oxygen from the apparatus, the outlet cannula of the oxygen device is connected to a rubber tube with a filter instead of a pressure pump. The introduced air is completely absorbed from the abdominal cavity within a few days.

Pneumopsritoneum allows you to establish a number of pathological changes in the kidneys, in the abdominal aorta, in the liver, in the spleen, in the diaphragm.

Contraindications to the use of pneumoperitoneum are: peritonitis, weakness of cardiac activity, persistent flatulence.

X-ray technique with the introduction of a gaseous contrast agent into the perirenal adipose tissue or pneumothorax is as follows: preliminary preparation of the animal is not required here; air or oxygen is injected into the peritoneal tissue from the back to the left or right of the spine, depending on the kidney being examined.

To introduce air, use the same device as for pumping air into the abdominal cavity. A puncture needle is taken with an injection needle with a large diameter and a length of at least 7-8 cm.

The puncture site is prepared accordingly (hair removal, disinfection).

To examine the left kidney, an injection is made at the level of the end of the transverse process of the second lumbar vertebra, and for the study of the right kidney, at the level of the end of the transverse process of the first lumbar vertebra, 3–5 cm away from the midline of the lower back.

The needle is inserted in a perpendicular direction to the bone, then it is displaced from the transverse process and advanced further by 0.5–1 cm.

Air is blown under the screen to monitor the correct entry of air into the perirenal region and the amount of air or oxygen introduced.

It should be pointed out that the introduction of filtered air to dogs both in the abdominal cavity and in the perirenal region has not yet caused any complications. Therefore, oxygen does not have any great advantage in this respect. Pneumoren is used to establish a tumor in the kidney, kidney stones, especially in the presence of uric acid and cystine stones, which weakly absorb x-rays and are not visible with normal transillumination or a picture.

The use of pnsvmoren is contraindicated in purulent processes in the lumbar region, in pyonephrosis and hydronephrosis.

To contrast agents of the second group includes a number of different chemical compounds, which include substances with a heavy atomic weight, and these contrast agents are not universal. Each of them is designed to study or several organs, or even just one. For the study of dogs, the following are more often used.

barium sulfate. For x-ray studies, a chemically pure, completely harmless, insoluble, odorless and tasteless white powder is produced in a special package of 100 g. It is used to study the digestive organs (esophagus, stomach and intestines). Indirectly, when examining the stomach and intestines, it is possible to determine the presence of intra-abdominal tumors (by shifting the shadow of the stomach or intestines from its usual place) (Fig. 168 and 169).

Rice. 168. X-ray from the stomach of a dog with barium sulfate

The amount of barium sulphate required for one study of a dog ranges from 25 to 100–150 grams, depending on the size of the dog and the study song. If, for example, it is required to examine the patency of the esophagus in a large dog, then 25-50 g is sufficient.

Rice. 169. X-ray from the intestines of a dog with a contrast agent

To study the stomach and intestines for a large dog, 100–150 g is required.

When examining the stomach and posterior intestines, preliminary preparation of the dog is necessary, and when examining the stomach, a 10-12-hour fasting diet is sufficient, and when examining the intestines, in addition, a cleansing enema is given the day before and on the day of the study (Fig. 161).

A portion of barium is mixed with milk or curdled milk in an amount of 250-500 ml, depending on the size of the dog and the purpose of the study. The prepared suspension is given to the dog. Usually the dog willingly eats such a portion of the barium suspension. If you refuse to accept this food, a barium suspension is poured into the buccal space with a spoon.

Yodolipol- iodized oil, transparent brownish-yellow oily liquid. Chemical compound of iodine with sunflower oil. Contains 30% iodine. In combination with oil, iodine loses its cauterizing property and is absorbed slightly. Iodolipol is produced in sterile sealed yellow glass ampoules of 10 and 20 ml and in 100 ml vials. Applied for the study of the bronchi and the study of fistulous passages.

Bronchial examination technique(according to Kashintsev) - bronchography is as follows. To release the lumen of the bronchi from the pathological secret, atropine 1: 1000 is administered intratracheally at a dose of 1–3 ml, then morphine 1: 1000 is intratracheally administered intratracheally at a dose of 0.5–1 ml per 1 kg of live weight and a 5% solution novocaine (5–10 ml per dog). It is necessary to enter in small portions slowly (anesthesia lasts 15-20 minutes), the contrast agent is injected through the probe - (the best way to insert the probe into the trachea) - through the nasal opening.

Before inserting the probe, the nasopharyngeal mucosa is anesthetized by instillation into the nasal cavity of a 5% solution of novocaine in an amount of up to 2 ml. After that, a probe (4 mm rubber tube) is inserted 40-50 cm into one of the nasal cavities up to the larynx (cough, exhaled air stream). Up to 5 ml of a 5% solution of novocaine is poured through the probe to anesthetize the trachea. Then, under the control of the screen, the probe is advanced further, and, giving the animal a right or left lateral position, the end of the probe is inserted into the corresponding bronchus. A contrast agent is injected from a syringe through a probe into the bronchi, periodically controlling their filling under the screen. Instead of iodolipol, Kashintsev suggested using a 50% suspension of barium sulfate.

The contrast method of research can establish a number of morphological and functional changes in the bronchi (bronchiectasia, bronchospasm, strictures, weakening of the ciliated epithelium, etc.), which are not visible with normal transillumination and a picture.

Methodology for the study of fistulous passages - fistulography. The dog is placed on the x-ray table. The skin is processed in the fistula area (hair cutting, removal of crusts, etc.). If possible, the contents of the fistulous passage are removed as completely as possible.

Filling the fistulous passage with iodolipol should be done in such a position of the animal that the contrast agent does not spill out of the fistula. A contrast agent is injected into the fistulous tract from a syringe connected by a thin elastic catheter, which is lowered to the bottom of the fistulous tract. As the fistulous canal fills, the catheter is gradually pulled out, and the external opening of the fistula is sealed with a sticky plaster. After that, an x-ray of this area is made (Fig. 170).

Rice. 170. Fistulography with barium sulfate

By the same method, a barium mixture with oil can be used for fistulography.

Sergozin- sodium monoiodomethanesulfonic acid. White crystalline powder, odorless. Contains at least 50% iodine. It dissolves in two parts of water, in 40 parts of alcohol. Aqueous solution of neutral reaction. Withstands sterilization.

Sergozin is used in the study of the renal pelvis, ureters, bladder and vascular studies. The dose of dry matter for small dogs is 8–10 g, for large dogs - 15–18 g. Usually, a 30–40% solution is taken for intravenous administration (intravenous pyelography), and for examining the bladder and urethra, a 10–20% solution (cysto- and urethrography). The solution is prepared on the day of application (shortly before application).

Method of intravenous pyelography. Preliminary preparation of the patient consists in removing urine from the bladder before the study and setting a cleansing enema for 1-2 hours. A sample of 20 g of sergosin powder is diluted in 50 ml of warm saline. The liquid is filtered twice through filter paper. Then boil for 20 minutes in a water bath and cool to body temperature. The resulting solution is injected into the vein slowly (3-4 minutes). After 7-10 minutes, they begin to produce translucence, and if necessary, take a picture. In the future, every 10–15 minutes, repeated studies are used to see the dynamics of the flow of a contrast agent from the bloodstream into the renal pelvis and its movement through the ureters into the bladder.

Usually, after 35–45 minutes, clearly visible contours of the pelvis, ureters, and even the bladder can be seen in the picture.

Excretory pyelography makes it possible to establish congenital anomalies, displacement of the kidneys, hydro- and pyonephrosis, kidney tumors, kidney stones. The method of excretory (intravenous) pyelography makes it possible to recognize not only the listed macroscopic changes, but at the same time to identify the functional state of each kidney separately.

The pelvis of a diseased kidney with reduced function is filled with a contrast mass later and less intensively compared to a healthy one. If, 15 minutes after the administration of Sergosin, there is no shadow of the pelvis on the radiograph, this indicates a loss of the ability of the kidney to remove toxins.

The advantage of intravenous pyelography is that, in addition to the kidneys, a picture of the state of the ureters and even the bladder is simultaneously revealed.

Method of examination of the bladder. Preliminary preparation of the animal is the same as for intravenous pyelography. A 10–20% aqueous solution of sergosin is prepared and a contrast agent is injected from a syringe through a urinary catheter into the bladder.

In this way, it is possible to establish a change in the size and shape of the bladder, its displacement from compression by a tumor or an organ of the uterus with fetuses, the presence of a tumor of the bladder or stones. If urinary stones or the presence of a tumor are suspected, it is necessary to re-examine after emptying the bladder from the contrast mass. The fact is that the contrast mass is deposited on the surface of the tumor or absorbed by urinary stones of low density, and therefore, after the removal of the contrast mass from the bladder, both the tumor and the stones stand out better. They can be detected especially well if, after removing sergosin from the bladder, gas (filtered air or oxygen) is introduced there to straighten the bladder.

Vessel study technique - vasography. In practice, it becomes necessary to examine the peripheral vessels of dogs with a contrast method.

For the study of veins and arteries, a 40% solution of sergozin is used. A solution prepared according to the above method is injected into the lumen of the vessel with a needle of the appropriate diameter from a syringe. With arteriography, a contrast agent is injected into the lumen of the artery above the diseased area, and with venography - below.

Vasography makes it possible to establish the presence and degree of circulatory disorders in the diseased area, the presence of thrombosis, the development of callaterals. This method of studying peripheral vessels is still little used in practice.

Processing of the removed x-ray film

To process the removed X-ray film or to develop the latent image, it is necessary to have a specially equipped room. The photo room should be well darkened. The minimum that you need to have to work in the photo room: 1) a lantern with red glass, 2) at least three baths for solution and water. The dimensions of the trays produced by the industry correspond to the dimensions of the film; 3) dishes for solutions - 2 glass jars with a volume of 2 liters.

In addition, appropriate chemicals are needed to prepare developer solutions (repair solution) and fixer solutions.

Any developer must have the following composition:

1) developing agents - metol, hydroquinone,

2) preservatives - sodium sulfite,

3) a substance that accelerates the manifestation - soda, potash,

4) anti-veiling agent - potassium bromide.

The ratio of the individual components of the developer is indicated by the film manufacturing factory (the recipe is attached to the box or enclosed in the film bag).

In order to develop, i.e. make visible the latent x-ray image, the exposed film must be treated with a developer solution. The developing substances included in it - metol, hydroquinone and some others - in the presence of gelatin selectively act on the silver bromide grains that make up the emulsion layer. The developer first of all restores - turns into metallic silver those grains of silver bromide that have been affected by radiation from screens or X-rays. On unlit grains of silver bromide, the developer acts much more slowly; their decomposition occurs only after a long stay of the film in solution, when using solutions with an abnormally high temperature, or solutions in the manufacture of which mistakes were made when weighing the chemicals.

When developing a latent image, it should be ensured that all grains of silver bromide exposed to light or X-rays are converted into metallic silver by the action of the developer; at the same time unlit grains of silver bromide should remain unchanged.

Development is a chemical reaction of decomposition of grains of silver bromide and, like any chemical reaction, depends on temperature.

An increase in temperature enhances the activity of the developer and accelerates the decomposition of silver bromide. Lowering the temperature slows down the reaction and therefore takes longer to get the full effect.

The duration of development also depends on the composition of the developer - mainly on the concentration of its constituent substances. Reducing the concentration of developing substances and alkali prolongs the development.

Recall that the duration of manifestation should be understood as the time required for the almost complete transformation of the illuminated grains of silver bromide into metallic silver; unilluminated grains with such a duration of manifestation remain unchanged (the image is not veiled).

There are two ways to perform the development process:

a) standard development over time, taking into account the temperature of the solution and

b) development with visual control of the process.

The data of research work and practice convincingly show that the process of manifestation must always be carried out, controlling its duration by the clock (of any system - sand and spring, etc.). Only under this condition, the light sensitivity of the photographic material is fully used, maximum contrast is obtained, minimum veil is obtained, and at the same time the necessary standardization of the results is ensured.

When developing in time with deviations from normal exposure (within 50% of normal), radiographs of a sufficiently high quality are obtained with the study of all details. With large errors in the conditions of exposure of the manifestation in time, it is possible to establish what kind of error - overexposure or underexposure - was made.

When developing with visual control of the process, the moment of the end of the development is set according to the visual subjective impression of the worker who, in the weak light of a laboratory lamp, tries to consider whether all the necessary image details have appeared on the radiograph and whether the development process has gone too far.

At the end of development, the emulsion layer, along with metallic silver, which forms the image, still contains a fairly significant amount of silver bromide. In order for the radiograph to acquire the necessary stability and invariability during storage, silver bromide must be removed from the emulsion layer. This process is called capturing or pinning the image. Fixing consists in the fact that the emulsion layer is immersed in a solution of such chemicals, which, by dissolving the unchanged silver bromide, do not affect the metallic silver of the image. Of the rather large number of different substances used for this purpose, practically only an aqueous solution of sodium sulphate (sodium hyposulfite or, even shorter, hyposulfite) is used.

Solutions containing from 5 to 40% hyposulfite have a sufficient dissolution rate of silver bromide. However, a neutral aqueous solution of hyposulfite is unstable with respect to traces of the developer in the emulsion layer and quickly turns brown. To increase the stability of fixing solutions, they are acidified with some acid that does not decompose hyposulfite - boric, acetic. Sulfuric acid can also be used with some precautions. Acidified solutions of hyposulfite can be used for a long time, and at the same time they almost do not stain.

A) Fixer with boric acid

Hot water - 500 ml

Hyposulfite - 400 g

Boric acid - 40 g

Water up to volume - 1 l

B) Fixer with acetic acid

Hot water - 500 ml

Hyposulfite - 400 g

Crystalline sodium sulfite - 50 g

Acetic acid (30%) - 40 ml

Water up to volume - 1 l

The rate of fixation, as well as the rate of development, depends on the temperature and concentration of the solution. Solutions with 30–40% hyposulfite content have practically the highest dissolution rate of silver bromide and at the same time a long duration of use. To determine the minimum duration of fixation, the following rule should be applied: "the duration of fixation should not be less than twice the development time at a given temperature."

Exceeding this time does no harm. The film can be left in the fixative solution for several hours without any visible weakening of the image. Only after 18–24 hours of the fixing solution may there be a slight dissolution of the silver and a weakening of the image.

Reducing fixation time beyond what is necessary always brings irreparable harm. The often observed deterioration of very important radiographs during storage depends on insufficient and incomplete fixation. The dissolution of silver bromide in hyposulfite solutions has several transitions - initially a complex complex compound of silver sulphate and sodium is formed, which is sparingly soluble in water and therefore not completely removed from the layer during subsequent washing. The formation of this compound is accompanied by a lightening of the layer and the disappearance of the characteristic color of the photosensitive layer. If the fixing process is interrupted at this stage, it is necessary to wash the layer for a very long time in order to completely remove traces of the sparingly soluble compound. If it is not completely removed, then after about 2–3 months, under the action of moisture and oxygen in the air, it decomposes in a layer with the release of silver sulfide, which stains the X-ray pattern in a yellow-brown color. The resulting stains cannot be removed. Long-term fixation converts the sparingly soluble complex compound of silver sulphate into a readily soluble one and is completely removed from the layer during subsequent washing.

The emulsion layer does not lose its photosensitivity immediately after transferring the film to the fixer solution. Only after 3-4 minutes the process of dissolution of silver bromide reaches a stage at which the light sensitivity of the film almost completely disappears and the film can be viewed without harm in white light.

Washing the fixed emulsion layer is the last step in the wet treatment. It can be carried out in two ways: 1) - in running water and 2) - in periodically replaced water.

Rinsing in running water is carried out easily only in cases where there are no difficulties with the inflow and outflow of water. When using the special wash tank (included in the photo lab film processing kit) for rinsing, the water speed should be between 2 and 4 liters per minute. For a complete flush with a water flow of 2 liters per minute, 25–30 minutes are required. Increasing the exchange rate to 4 liters per minute makes it possible to reduce the flushing time to 20 minutes. It is not advisable to increase the water flow rate by more than 4 liters per minute, since the removal of salts contained in the gelatinous layer depends not only on the rate of water exchange, but also on diffusion processes in the gelatinous layer. If a factory flush tank is not available, one can be easily fabricated on site.

If there is not enough water for flushing or if there is no good flow, flushing with periodic water changes should be recommended. To do this, it is necessary to have two cuvettes measuring 30X40 or 40X50 cm. All films are placed in one of the cuvettes filled with clean water for 5 minutes. After this time, one by one, the films are transferred into another cuvette with pure water. When transferring, one should strive to remove as much contaminated water as possible from the surface of the film. To do this, the radiographs are raised vertically above the cuvette and shaken several times. The location of the films after transfer from one cell to another will change - the upper films will take the lower position, while the lower ones will become the upper ones. This completely eliminates the possibility of film adhesion and prevents the formation of poorly washed areas. After 5 minutes, the films from the second cuvette are again transferred one by one to the first, the hearth in it is replaced with a clean one. Alternate transfer from one cuvette to another with a change of water is repeated 5–6 times. Each time the films are kept in clean water for 5 minutes. During this time, a practical equilibrium occurs between the concentration of salts that remain in the gelatin layer and pass into the wash water, and therefore a longer exposure of the films to the same wash water is not only useless, but also harmful. The amount of salts removed from the gelatin trees after 5-minute washing does not increase, only the swelling of the gelatin increases.

The water consumption with this method of washing is less than when washing in running water, while contaminants are removed from the gelatinous layer very well. Therefore, radiographs that need to be stored for a long time (materials for dissertations, rare cases of illness, etc.) should only be washed in this way.

The final operation in radiography is the drying of the washed radiographs. To do this, they are hung at 1 or 2 corners in a vertical position in a dry, dust-free room so that if the films accidentally fluctuate with air currents, they cannot touch and stick together. To speed up drying and prevent the appearance of stains, after 15-20 minutes, after the films are suspended and the main part of the water covering the surface of the film, glass, it is recommended to collect as much moisture as possible by touching the lower edge of the film with a well-wrung, slightly damp cloth.

This simple procedure significantly reduces the complete drying of the film.

Acceleration of drying of a partially dried film should be avoided, since rapid, uneven drying leads to the formation of local darkening of the radiograph and, as a result, in some cases, to errors in the diagnosis.

Drying radiographs in a darkroom is impractical, since insufficient ventilation slows down drying and at the same time increases dampness in the laboratory. In emergency cases, the drying of the film can be greatly accelerated by the use of an alcohol bath. To do this, the washed x-ray image is shaken several times to free it from large drops of water and then immersed in an alcohol bath for 5 minutes. The strength of the alcohol should be in the range of 75–80 ° (i.e., the alcohol should be diluted approximately 1/4 with water). X-rays removed from the alcohol bath dry completely within 5-8 minutes. With a longer action of the alcohol bath (10–15 minutes), the drying process practically does not accelerate, but the danger of clouding the celluloid base increases greatly.

In order for the alcohol bath to be reused, the alcohol is poured into a bottle, on the bottom of which a layer of dry potassium carbonate (potash) 1–2 cm thick should be poured. Potash is insoluble in alcohol. Its hygroscopicity is very high, and it quite easily takes away excess moisture from alcohol. Two layers of liquid are formed in the bottle, the bottom layer is a saturated aqueous solution of potash with mushy particles of dry salt, the top layer is alcohol with a strength of 80–82 °, that is, approximately the strength that will be needed for drying in the future. When using this top layer for drying, it is carefully, without shaking, drained from the potash solution, and then poured back into the bottle after use. So you can use the same portion of alcohol repeatedly, periodically changing the solution of potash in the bottle, when the particles of dry salt are completely dissolved and the lower layer of the liquid becomes homogeneous.

X-ray machines

E. I. Lipina

Each X-ray apparatus, regardless of its purpose, must necessarily have the following main components: an autotransformer, a step-up transformer, an X-ray tube helix filament transformer (step-down) and an X-ray tube. Without these basic parts, obtaining and controlling the quantity and quality of rays is almost impossible.

autotransformer is the main source of power for all units of the X-ray machine. It allows you to connect the X-ray machine to a network with a voltage of 90 to 220 volts, and thus ensures its normal operation. In addition, the autotransformer makes it possible to take current from it to power individual components of the apparatus in a wide voltage range. So, for example, the autotransformer is used to power both a small signal light on the control table, which requires only a few volts, and the main X-ray step-up transformer, which is supplied not only by tens, but by hundreds of volts.

step-up transformer in an x-ray machine it serves to increase the voltage supplied to the x-ray tube to many tens of thousands of volts. Usually the transformation ratio reaches 400-500. This means that if 120 volts is supplied to the primary winding of the step-up transformer of the x-ray machine, then a current of 60,000 volts appears in its secondary winding. This high voltage current is applied to the x-ray tube and produces x-rays.

Incandescent transformer (step-down) serves to reduce the voltage of the current coming from the autotransformer to 5-8 volts. The low voltage current in the secondary winding of the step-down transformer enters the X-ray tube helix and provides a certain degree of its incandescence.

x-ray tube is an X-ray generator. Depending on the power and purpose, X-ray tubes have a variety of external shapes and sizes. But, despite external differences, any X-ray tube must have the following three main components:

1. glass bottle in the form of a cylinder or with a swelling in the middle, from which air is completely removed using a special vacuum pump.

2. tungsten spiral rectilinear shape, which is fixed in the groove-like recess of the spiral holder. The spiral and the wires feeding it are located on one side of the tube's glass bottle. When an incandescent transformer is connected to the wires coming out of the tube from the side of the spiral, the spiral glows. This side of the tube is called the cathode.

3. Massive metal rod with a beveled end, which is located on the other side of the glass cylinder of the tube. The bevelled surface of the metal rod and the tungsten spiral of the tube are located in the central part of the glass container at a small distance from each other. The end of the metal rod, facing the spiral of the tube, has a rectangular tungsten plate (refractory metal) on its beveled surface. This side of the X-ray tube is called the anode.

During operation, the anode of the X-ray tube becomes very hot and, if it is not cooled, the anode plate may melt and the tube fails. Therefore, the x-ray tube must have a cooling system. There are three types of anode cooling - air, water and oil.

Types of x-ray machines

Our domestic industry produces a whole range of X-ray units. Of these, for the study of dogs, it is most advisable to use the following devices: x-ray machine RU-760 (suitcase), x-ray machine RU-725-B (ward).

X-ray apparatus RU-760 (suitcase). The apparatus is kenotronless, half-wave. Consists of the following parts:

Rice. 171. X-ray machine RU-760

1. High-voltage device - a metal tank where: a) a high voltage transformer, b) a step-down incandescent transformer and c) an X-ray tube 2BDM-75. The tank is filled with transformer oil. The oil serves to insulate these parts from high voltage and to absorb the heat generated during the operation of the X-ray tube and transformers.

2. The control device is a small metal box, inside of which there are: a) an autotransformer, b) a stepped switch for adjusting high voltage (hardness) and c) a milliammeter to control the radiation intensity of the tube in milliamps, d) panels with five pin contacts.

On the top cover of the box are displayed: a milliammeter, a switch handle, a plug socket for connecting a time relay and 5 holes for connecting the mains supply. They have the designations: 0, 120, 127, 210, 220, on the front wall there is a terminal with the designation “E”, to which the ground wire of the device is connected. Below this terminal, a four-wire cable enters from the control device, which at the other end has a block with four sockets. The block serves to connect the control device to the high-voltage device. To do this, there are 4 pin contacts on one side of the casing of the high-voltage device.

3. The tripod of the device consists of a wooden base, a collapsible metal stand and a fork for fastening a high-voltage device. The tripod device allows you to give the high-voltage device different positions.

4. Manual time switch - made of mechanical type plastic. It has a crank with divisions from 0.5 to 10 seconds, a starting lever at the transition point of the round part of the watch to the handle on the right and a setting button on the right side of the round part of the watch.

5. Tube - conical, metal, to limit the x-ray beam. The tube is dressed on the hole for the exit of x-rays in the housing of the high-voltage device.

To connect the device to the network, a two-core cable 5 m long is attached to it. At one end it has a plug, and at the other - two plug sleeves for connecting to a pin in the control device corresponding to the mains voltage.

There is also a cryptoscope with a screen of 18X24 cm for transillumination in an unobscured room or in a field.

The device fits into two suitcases. Total weight - 43 kg. The device is assembled according to the instructions sent with the device.

The power of this device is small. The device has been successfully used to study small animals (dogs, pigs) and to take pictures of the tail vertebrae of cows in order to determine the presence of mineral deficiency.

X-ray apparatus ward RU-725-B. Semi-headless, kenotron-free diagnostic apparatus. It has the following main parts:

Rice. 172. X-ray apparatus RU-725-B

1. High-voltage block - a metal cylindrical tank, inside of which are placed: a high-voltage transformer, giving 95 kilovolts, an incandescent transformer, giving 4 volts, an x-ray tube of the 4-BDM-100 ″ type, metal oil atomizers (2 pcs.), Providing a constant pressure inside the tank at oil volume difference due to temperature change.

2. Control table (switchgear) - a quadrangular metal box with collapsible walls. On the top cover of the control table are placed:

a) milliammeter for measuring high voltage current (left);

b) a 250 volt voltmeter (on the right), showing the voltage in the network or at the terminals of the primary winding of the step-up transformer, depending on the position of the voltmeter switch located under the device;

c) the handle of the network corrector (bottom left), which has 8 positions from 0 to 7, and when the corrector is at zero, no current enters the device. Therefore, the network corrector is also the device's power switch;

d) voltage regulator knob, which has 8 steps from 1 to 8 (bottom right). This regulator changes the voltage supplied to the high-voltage transformer, i.e., the hardness of the x-ray radiation is regulated. Each position of the hardness knob has the following meaning:

(* Voltages in kilovolts in the table are given with rounding).

e) Mode switch - has four positions: two "off", one "pictures" (SI), one "transmission" (PR).

f) Switch for the lighting of the cabinet and the illumination of measuring instruments (voltmeter and milliammeter when translucent).

g) Voltmeter switch to mains or transformer.

h) Red signal lamp that lights up when the high voltage current is turned on (via the mode switch).

i) Regulator of the anode tech (rheostat for heating the tube helix during transillumination).

Inside the control table there are: an autotransformer, a contactor and a terminal panel located to the rear wall of the table box. The back wall is hinged and easy to open, providing access to the terminal panel, contactor and sockets for connecting cables to power the machine from the mains.

The terminal board has terminals numbered from 78 to 220, for a total of 9 terminals. There is a short reversible wire that is connected to a terminal that has an equal or slightly lower voltage value of the electrical network to which the device is to be connected. On the same panel there are sockets for connecting a time relay and a foot switch. They are included after the assembly of the device.

3. The tripod of the device consists of three parts: a) a trolley on four wheels, b) a column of a tripod with a counterweight - a spring to balance the weight of the high-voltage unit, c) a movable bracket for horizontal movement of the high-voltage unit (X-ray tube).

In addition, the machine is supplied with a three-wire network cable for connecting the control table power supply, a six-wire short cable for connecting the control table with a high-voltage unit, manual timers, a foot switch, a 24 X 34 cryptoscope and a number of other small spare parts, including three special plug sockets.

The total weight of the entire X-ray unit is 190 kg. The power consumed by the device during transillumination is 1 kilowatt, while taking pictures - about 3 kilowatts. Assembly of the device is not difficult and is carried out according to the instructions attached to the device.

The power of this device allows you to shoot all areas of the dog's body.

Working with apparatus RU-725-B

Preparing the Machine for Operation. As soon as the device is assembled, connect the high-voltage unit with the control table with a short six-wire cable (the right group of pins labeled "transformer"). Then the network cable block is connected to the control table (the left group of pins labeled "network").

Install the adjustable wire of the terminal panel on the terminal corresponding in number to the mains voltage. The network corrector knob is set to position 0, and the stiffness knob is set to 1. The mode switch with the spout is turned to the “off” position. Connect the three-prong plug of the mains cable (one of which is marked with the letter E for grounding) into a special socket. The mains current is connected to the socket (the socket is attached to the device).

translucence. For translucence, the following manipulations are required.

1. Set the voltmeter switch to the "mains" position.

2. Turn the knob of the network corrector from zero to one and look at the voltmeter (the right instrument on the cover of the control table). If its arrow does not reach 220 volts, then by turning the knob of the network corrector clockwise, the voltage is brought to 220 volts.

3. Turn the mode switch to "transmission" (PR), while the spiral of the X-ray tube in the high-voltage unit should glow.

5. Press the high voltage footswitch button. At the same time, the red signal light on the cover of the control table should light up. The milliammeter should show 2-4 milliamps (left instrument). If the arrow does not move away from zero when the pedal is pressed, it is necessary to rotate the tube helix filament rheostat clockwise until the milliammeter shows a current value of several milliamps.

6. Set the stiffness regulator to the required value (see the table above), and when moving from one position to another (adjacent), the high voltage current must be turned off (release the foot pedal button).

In addition, here it is also necessary to remember that the X-ray tube of this apparatus is designed to operate when a current is supplied to it from a step-up transformer of not more than 100 kilovolts. Therefore, when translucent, it is forbidden to set the voltage regulator to the eighth position.

The regulator can be set to the seventh position only if, according to the voltmeter reading, no more than 230 volts are supplied to the step-up transformer.

Having directed the high-voltage block with a hole for the exit of rays to the area of the body to be X-rayed, the foot pedal is pressed and transillumination is performed.

Snapshots. In order to be able to take x-rays, you must:

1. Set the voltmeter switch to the “mains” position, if no transillumination has been performed before, and immediately start taking pictures.

2. Turn the mode switch to the “images” (SN) position, and the X-ray tube should glow (visible through the window of the high-voltage unit).

3. Turn the network corrector knob from position 0 to 1, if this was not done before during transillumination. Then, turning the corrector knob clockwise, we bring the mains voltage to 220 volts on the voltmeter.

4. Set the voltmeter switch to the "transformer" position.

5. Set the voltage regulator knob to the desired position to obtain the appropriate stiffness (see table above).

6. Set the time switch to the proper shutter speed for the area of the animal's body being filmed.

7. Press the lever of the time relay and after the exposure the picture is ready.

In snapshot mode, the anode current is not adjustable. It is always equal to 20 mA for all voltages that the device gives.

With wheels, this X-ray unit can be easily transported from one room to another. In addition, it can also be quickly disassembled into 4 parts and transported from the clinic to the farm for examination of a sick animal on the spot.

X-ray protection measures

In production, especially transillumination, X-rays are directed not only to the object under study, but also to the radiologist, since he is forced to face towards the rays. Prolonged exposure to X-rays has a harmful effect on the body.

In order to avoid hitting x-rays on the radiologist and attendants, there are special protective devices. These include:

1. Filter, which is installed in front of the hole in the x-ray tube for the exit of rays. The filter is a metal plate made of aluminum with a thickness of 0.5–1 mm. The presence of this filter is strictly required for each tube. The purpose of this filter is to absorb the very soft X-rays generated in the tube. It is necessary to delay these rays because they are the most harmful to the skin. Having too little penetrating power, soft X-rays are completely absorbed by the skin. As a result of prolonged exposure to such rays (over a number of years), dermatitis may first occur, and then skin cancer may form. The aluminum filter absorbs all these rays upon exiting the tube, and passes all the other more rigid ones.

2. metal tube, which is dressed directly on the tube. The purpose of the tube is to limit the width of the x-ray beam. The wide metal base of the tube with the presence of lead absorbs the rays falling on it, and only those that fall into the window at the base of the tube pass through. In this way, a reduction in the number of unnecessary rays directed towards the patient is achieved.

3. leaded glass is the most important device for protection from rays. It is located on the front side of the screen for transmission and has a slightly yellowish color, as it contains a large percentage of lead. This glass is completely transparent to visible light and opaque to x-rays.

X-rays, passing through the screen, fall on the leaded glass and are absorbed by it. Thus, the head and upper body of the radiologist thanks to this glass are reliably protected from x-rays.

In addition, there are metal visors on the screen for translucence, where the handles are attached. These visors protect the radiographer's hands from rays passing by the lead glass screen.

4. Lead apron; it is designed to protect the torso and legs of the radiographer. The basis of the apron is rubber, which contains a certain amount of lead.

To protect the radiologist or attendants during fixation of the animal during transillumination, when the hands fall directly into the field of direct X-rays, apply lead gloves. Gloves are made of lead rubber. In appearance, they are somewhat larger and rougher than chemical gloves.

In addition to the above remedies, there is one more - protective screen. It is a wooden shield 1.5 m long and 1 m high. For ease of movement from place to place, this shield is mounted on small wheels. The screen is lined with lead rubber on one side and serves to protect the lower torso and legs.

As a result of the use of these protective devices, exposure of the radiologist to direct rays and harmful effects is minimized (permissible dose of 0.03 roentgen per day).

In addition, during transillumination, a small amount of scattered rays are formed, which are formed as a result of their refraction by the tissues and cells of the translucent area.

Both direct and scattered beams have the ability to ionize the air, resulting in the accumulation of ozone and a number of nitrogenous compounds in the X-ray room during a 5-6 hour working day at full load. A significant amount of these gases during daily stay in such an atmosphere will have a harmful effect on the body through the respiratory tract, so the X-ray room must always be well ventilated after work.