X-ray radiation by whom and when discovered. Doses of x-ray radiation in x-ray diagnostics. What characterizes this type of radiation

In 1895, the German physicist Roentgen, while conducting experiments on the passage of current between two electrodes in a vacuum, discovered that a screen covered with a luminescent substance (barium salt) glows, although the discharge tube is closed with a black cardboard screen - this is how radiation was discovered that penetrates through opaque barriers, called X-ray X-rays. It was found that X-rays, invisible to humans, are absorbed in opaque objects the stronger, the greater the atomic number (density) of the barrier, so X-rays easily pass through the soft tissues of the human body, but are retained by the bones of the skeleton. Sources of powerful X-rays were designed, which made it possible to shine through metal parts and find internal defects in them.

The German physicist Laue suggested that X-rays are the same electromagnetic radiation as visible light rays, but with a shorter wavelength and all the laws of optics are applicable to them, including diffraction is possible. In visible light optics, diffraction at the elementary level can be represented as the reflection of light from a system of grooves - a diffraction grating, occurring only at certain angles, while the angle of reflection of the rays is related to the angle of incidence, the distance between the grooves of the diffraction grating and the wavelength of the incident radiation. For diffraction, it is necessary that the distance between the strokes be approximately equal to the wavelength of the incident light.

Laue suggested that X-rays have a wavelength close to the distance between individual atoms in crystals, i.e. atoms in a crystal create a diffraction grating for x-rays. X-rays directed at the surface of the crystal were reflected on the photographic plate, as predicted by theory.

Any changes in the position of atoms affect the diffraction pattern, and by studying the diffraction of x-rays, one can find out the arrangement of atoms in a crystal and the change in this arrangement under any physical, chemical and mechanical influences on the crystal.

Now X-ray analysis is used in many areas of science and technology, with its help they learned the arrangement of atoms in existing materials and created new materials with a given structure and properties. Recent advances in this field (nanomaterials, amorphous metals, composite materials) create a field of activity for the next scientific generations.

The occurrence and properties of X-rays

The source of x-rays is an x-ray tube, which has two electrodes - a cathode and an anode. When the cathode is heated, electron emission occurs, the electrons emitted from the cathode are accelerated by the electric field and hit the anode surface. An X-ray tube is distinguished from a conventional radio lamp (diode) mainly by a higher accelerating voltage (more than 1 kV).

When an electron flies out of the cathode, the electric field makes it fly towards the anode, while its speed continuously increases, the electron carries a magnetic field, the strength of which increases with the electron's speed. Reaching the anode surface, the electron is sharply decelerated, and an electromagnetic pulse arises with wavelengths in a certain range (bremsstrahlung). The distribution of radiation intensity over wavelengths depends on the material of the anode of the X-ray tube and the applied voltage, while on the side of short waves this curve starts from a certain threshold minimum wavelength, which depends on the applied voltage. The set of rays with all possible wavelengths forms a continuous spectrum, and the wavelength corresponding to the maximum intensity is 1.5 times the minimum wavelength.

With increasing voltage, the X-ray spectrum changes dramatically due to the interaction of atoms with high-energy electrons and quanta of primary X-rays. An atom contains internal electron shells (energy levels), the number of which depends on the atomic number (denoted by the letters K, L, M, etc.). Electrons and primary X-rays knock out electrons from one energy level to another. A metastable state arises, and a jump of electrons in the opposite direction is necessary for the transition to a stable state. This jump is accompanied by the release of an energy quantum and the appearance of X-rays. Unlike continuous spectrum X-rays, this radiation has a very narrow wavelength range and high intensity (characteristic radiation) ( cm. rice.). The number of atoms that determine the intensity of the characteristic radiation is very large, for example, for an X-ray tube with a copper anode at a voltage of 1 kV, a current of 15 mA, 10 14–10 15 atoms give characteristic radiation for 1 s. This value is calculated as the ratio of the total X-ray power to the energy of the X-ray quantum from the K-shell (K-series of X-ray characteristic radiation). The total power of X-ray radiation in this case is only 0.1% of the power consumed, the rest is lost, mainly due to the transition to heat.

Due to its high intensity and narrow wavelength range, characteristic X-ray radiation is the main type of radiation used in scientific research and process control. Simultaneously with the K-series beams, L and M-series beams are generated, which have much longer wavelengths, but their application is limited. The K-series has two components with close wavelengths a and b, while the intensity of the b-component is 5 times less than a. In turn, the a-component is characterized by two very close wavelengths, the intensity of one of which is 2 times greater than the other. To obtain radiation with a single wavelength (monochromatic radiation), special methods have been developed that use the dependence of the absorption and diffraction of X-rays on the wavelength. An increase in the atomic number of an element is associated with a change in the characteristics of the electron shells, and the larger the atomic number of the X-ray tube anode material, the shorter the K-series wavelength. The most widely used tubes with anodes from elements with atomic numbers from 24 to 42 (Cr, Fe, Co, Cu, Mo) and wavelengths from 2.29 to 0.712 A (0.229 - 0.712 nm).

In addition to the x-ray tube, radioactive isotopes can be sources of x-rays, some can directly emit x-rays, others emit electrons and a-particles that generate x-rays when bombarding metal targets. The X-ray intensity of radioactive sources is usually much less than that of an X-ray tube (with the exception of radioactive cobalt, which is used in flaw detection and gives radiation of a very small wavelength - g-radiation), they are small in size and do not require electricity. Synchrotron X-rays are produced in electron accelerators, the wavelength of this radiation is much higher than that obtained in X-ray tubes (soft X-rays), its intensity is several orders of magnitude higher than the intensity of X-ray tubes. There are also natural sources of X-rays. Radioactive impurities have been found in many minerals, and X-rays from space objects, including stars, have been recorded.

Interaction of X-rays with crystals

In the X-ray study of materials with a crystalline structure, the interference patterns resulting from the scattering of X-rays by electrons belonging to the atoms of the crystal lattice are analyzed. Atoms are considered immobile, their thermal vibrations are not taken into account, and all electrons of the same atom are considered to be concentrated at one point - a node of the crystal lattice.

To derive the basic equations of X-ray diffraction in a crystal, the interference of rays scattered by atoms located along a straight line in the crystal lattice is considered. A plane wave of monochromatic X-ray radiation falls on these atoms at an angle whose cosine is equal to a 0 . The laws of interference of rays scattered by atoms are similar to those existing for a diffraction grating that scatters light radiation in the visible wavelength range. In order for the amplitudes of all vibrations to add up at a great distance from the atomic series, it is necessary and sufficient that the difference in the path of the rays coming from each pair of neighboring atoms contains an integer number of wavelengths. When the distance between atoms A this condition looks like:

A(a – a0) = h l ,

where a is the cosine of the angle between the atomic series and the deflected beam, h- integer. In all directions that do not satisfy this equation, the rays do not propagate. Thus, the scattered beams form a system of coaxial cones, the common axis of which is the atomic row. Traces of cones on a plane parallel to the atomic row are hyperbolas, and on a plane perpendicular to the row, circles.

When rays fall at a constant angle, polychromatic (white) radiation decomposes into a spectrum of rays deflected at fixed angles. Thus, the atomic series is a spectrograph for X-rays.

Generalization to a two-dimensional (flat) atomic lattice, and then to a three-dimensional volumetric (spatial) crystal lattice gives two more similar equations, which include the angles of incidence and reflection of X-rays and the distances between atoms in three directions. These equations are called the Laue equations and underlie X-ray diffraction analysis.

The amplitudes of rays reflected from parallel atomic planes add up, and since the number of atoms is very large, the reflected radiation can be fixed experimentally. The reflection condition is described by the Wulff–Bragg equation2d sinq = nl, where d is the distance between adjacent atomic planes, q is the glancing angle between the direction of the incident beam and these planes in the crystal, l is the X-ray wavelength, and n is an integer called the order of reflection. The angle q is the angle of incidence with respect to the atomic planes, which do not necessarily coincide in direction with the surface of the sample under study.

Several methods of X-ray diffraction analysis have been developed, using both continuous spectrum radiation and monochromatic radiation. In this case, the object under study can be stationary or rotating, can consist of one crystal (single crystal) or many (polycrystal), diffracted radiation can be recorded using a flat or cylindrical X-ray film or an X-ray detector moving around the circumference, however, in all cases, during the experiment and interpretation of the results, the Wulf-Bragg equation is used.

X-ray analysis in science and technology

With the discovery of X-ray diffraction, researchers have at their disposal a method that allows them to study the arrangement of individual atoms and changes in this arrangement under external influences without a microscope.

The main application of X-rays in fundamental science is structural analysis, i.e. establishing the spatial arrangement of individual atoms in a crystal. To do this, single crystals are grown and X-ray analysis is carried out, studying both the location and intensity of the reflections. Now the structures of not only metals, but also complex organic substances, in which elementary cells contain thousands of atoms, have been determined.

In mineralogy, the structures of thousands of minerals have been determined by x-ray analysis and express methods for the analysis of mineral raw materials have been created.

Metals have a relatively simple crystal structure and the X-ray method makes it possible to study its changes during various technological treatments and create the physical foundations of new technologies.

The phase composition of the alloys is determined by the arrangement of lines on the X-ray patterns, the number, size and shape of crystals are determined by their width, the orientation of the crystals (texture) is determined by the intensity distribution in the diffraction cone.

These techniques are used to study the processes during plastic deformation, including the crushing of crystals, the occurrence of internal stresses and imperfections in the crystal structure (dislocations). When deformed materials are heated, stress relief and crystal growth (recrystallization) are studied.

When X-ray analysis of alloys determine the composition and concentration of solid solutions. When a solid solution appears, the interatomic distances and, consequently, the distances between atomic planes change. These changes are small, therefore, special precision methods have been developed for measuring the periods of the crystal lattice with an accuracy of two orders of magnitude higher than the measurement accuracy with conventional x-ray methods of research. The combination of precision measurements of the periods of the crystal lattice and phase analysis makes it possible to plot the boundaries of the phase regions on the state diagram. The X-ray method can also detect intermediate states between solid solutions and chemical compounds - ordered solid solutions in which impurity atoms are not arranged randomly, as in solid solutions, and at the same time not with a three-dimensional order, as in chemical compounds. There are additional lines on the x-ray patterns of ordered solid solutions; the interpretation of the x-ray patterns shows that impurity atoms occupy certain places in the crystal lattice, for example, at the vertices of a cube.

During quenching of an alloy that does not undergo phase transformations, a supersaturated solid solution can occur, and upon further heating or even holding at room temperature, the solid solution decomposes with the release of particles of a chemical compound. This is the effect of aging and it appears on radiographs as a change in the position and width of the lines. The study of aging is especially important for non-ferrous alloys, for example, aging transforms a soft, hardened aluminum alloy into a durable structural material, duralumin.

X-ray studies of steel heat treatment are of the greatest technological importance. During hardening (rapid cooling) of steel, a diffusionless austenite-martensite phase transition occurs, which leads to a change in the structure from cubic to tetragonal, i.e. the unit cell takes the form of a rectangular prism. On radiographs, this appears as an expansion of the lines and the separation of some lines into two. The reasons for this effect are not only a change in the crystal structure, but also the occurrence of large internal stresses due to the thermodynamic nonequilibrium of the martensitic structure and rapid cooling. During tempering (heating of hardened steel), the lines on the X-ray patterns narrow, this is due to the return to the equilibrium structure.

In recent years, X-ray studies of the processing of materials with concentrated energy flows (laser beams, shock waves, neutrons, and electron pulses) have acquired great importance; they required new techniques and produced new X-ray effects. For example, under the action of laser beams on metals, heating and cooling occur so quickly that in the metal, when cooled, the crystals have time to grow only to a size of several unit cells (nanocrystals) or do not have time to form at all. Such a metal after cooling looks like an ordinary one, but does not give clear lines on the X-ray pattern, and the reflected X-rays are distributed over the entire range of glancing angles.

After neutron irradiation, additional spots (diffuse maxima) appear on the X-ray patterns. Radioactive decay also causes specific x-ray effects associated with a change in structure, as well as the fact that the sample under study itself becomes a source of x-rays.

They are emitted with the participation of electrons, in contrast to gamma radiation, which is nuclear. Artificial X-rays are created by strongly accelerating charged particles and by moving electrons from one energy level to another, releasing a large amount of energy. Devices that can be obtained are X-ray tubes and particle accelerators. Its natural sources are radioactively unstable atoms and space objects.

Discovery history

It was made in November 1895 by Roentgen, a German scientist who discovered the fluorescence effect of barium platinum cyanide during the operation of a cathode ray tube. He described the characteristics of these rays in some detail, including the ability to penetrate living tissue. They were called X-rays by the scientist, the name "X-ray" took root in Russia later.

What characterizes this type of radiation

It is logical that the features of this radiation are due to its nature. An electromagnetic wave is what X-rays are. Its properties are the following:

X-ray radiation - harm

Of course, at the time of discovery and for many years after that, no one imagined how dangerous it was.

Where are x-rays used?

1. Medicine. X-ray diagnostics - "transmission" of living organisms. X-ray therapy - the effect on tumor cells.
2. The science. Crystallography, chemistry and biochemistry use them to reveal the structure of matter.
3. Industry. Detection of defects in metal parts.
4. Safety. X-ray equipment is used to detect dangerous items in luggage at airports and other places.

1. 
   High penetrating ability - able to penetrate certain media. X-rays penetrate best through gaseous media (lung tissue), but poorly penetrate through substances with high electron density and large atomic mass (bones in humans).
2. 
   Fluorescence - glow. In this case, the energy of X-rays is converted into the energy of visible light. Currently, the principle of fluorescence underlies the device of intensifying screens designed for additional illumination of X-ray film. This allows you to reduce the radiation load on the body of the patient under study.
3. 
   Photochemical - the ability to induce various chemical reactions.
4. 
   Ionizing ability - under the influence of X-rays, ionization of atoms occurs (decomposition of neutral molecules into positive and negative ions that make up an ion pair.
5. 
   Biological - damage to cells. For the most part, it is due to the ionization of biologically significant structures (DNA, RNA, protein molecules, amino acids, water). Positive biological effects - antitumor, anti-inflammatory.

1. 
   Beam tube device

X-rays are produced in an X-ray tube. An X-ray tube is a glass container with a vacuum inside. There are 2 electrodes - cathode and anode. The cathode is a thin tungsten spiral. The anode in the old tubes was a heavy copper rod, with a bevelled surface facing the cathode. On the beveled surface of the anode, a plate of refractory metal was soldered - the mirror of the anode (the anode is very hot during operation). In the center of the mirror is focus of x-ray tube This is where X-rays are produced. The smaller the focus value, the clearer the contours of the subject being shot are. Small focus is considered 1x1 mm, and even less.

In modern X-ray machines, electrodes are made from refractory metals. Typically, tubes with a rotating anode are used. During operation, the anode is rotated by a special device, and the electrons flying from the cathode fall into the optical focus. Due to the rotation of the anode, the position of the optical focus changes all the time, so such tubes are more durable and do not wear out for a long time.

How are x-rays obtained? First, the cathode filament is heated. To do this, using a step-down transformer, the voltage on the tube is reduced from 220 to 12-15V. The cathode filament heats up, the electrons in it begin to move faster, some of the electrons go beyond the filament and a cloud of free electrons forms around it. After that, a high voltage current is turned on, which is obtained using a step-up transformer. In diagnostic X-ray machines, high voltage current is used from 40 to 125 KV (1KV=1000V). The higher the voltage on the tube, the shorter the wavelength. When a high voltage is turned on, a large potential difference is obtained at the poles of the tube, the electrons “break off” from the cathode and rush to the anode at high speed (the tube is the simplest charged particle accelerator). Thanks to special devices, the electrons do not scatter to the sides, but fall into almost one point of the anode - the focus (focal spot) and are decelerated in the electric field of the anode atoms. When the electrons decelerate, electromagnetic waves arise, i.e. X-rays. Thanks to a special device (in old tubes - the bevel of the anode) x-rays are directed to the patient in the form of a divergent beam of rays, a "cone".

1. 
   X-ray imaging

X-ray film is a layered structure, the main layer is a polyester composition up to 175 microns thick, coated with a photographic emulsion (silver iodide and bromide, gelatin).

1. 
   Film development - silver is restored (where the rays passed through - blackening of the film area, where they lingered - lighter areas)
2. 
   Fixer - washing out silver bromide from areas where the rays passed through and did not linger.

1. 
   The device of a modern radiological room

1. The X-ray room itself, where the apparatus is located and the patients are examined. The area of ​​the X-ray room must be at least 50 m2

2. Control room, where the control panel is located, with the help of which the X-ray laboratory assistant controls the entire operation of the apparatus.

3. A photographic laboratory where cassettes are loaded with film, images are developed and fixed, they are washed and dried. A modern method of photo processing of medical X-ray films is the use of roller-type processors. In addition to undeniable ease of use, processors provide high stability of the photo processing process. The time of a complete cycle from the moment the film enters the processing machine to the receipt of a dry X-ray pattern ("from dry to dry") does not exceed several minutes.

4. Doctor's office, where the radiologist analyzes and describes the radiographs taken.

1. 
   Methods of protection for medical personnel and for patients from x-ray radiation

3 main protection methods: protection by shielding, distance and time.

1 .Shield protection:

X-rays are placed in the path of special devices made of materials that absorb x-rays well. It can be lead, concrete, barite concrete, etc. The walls, floor, ceiling in X-ray rooms are protected, made of materials that do not transmit rays into neighboring rooms. The doors are protected with lead material. The observation windows between the X-ray room and the control room are made of leaded glass. The x-ray tube is placed in a special protective casing that does not let x-rays through, and the rays are directed to the patient through a special "window". A tube is attached to the window, which limits the size of the x-ray beam. In addition, the X-ray machine diaphragm is installed at the exit of the rays from the tube. It consists of 2 pairs of plates perpendicular to each other. These plates can be moved and moved apart like curtains. In this way, the irradiation field can be increased or decreased. The larger the irradiation field, the greater the harm, therefore aperture is an important part of protection, especially in children. In addition, the doctor himself is irradiated less. And the quality of the pictures will be better. Another example of shielding is sewn up - those parts of the body of the subject that are not currently subject to shooting should be covered with sheets of lead rubber. There are also aprons, skirts, gloves made of special protective material.

2 .Protection by time:

The patient should be irradiated during x-ray examination for as little time as possible (hurry, but not to the detriment of diagnosis). In this sense, images give a lower radiation exposure than transillumination, because. very slow shutter speeds (time) are used in the pictures. Time protection is the main way to protect both the patient and the radiologist himself. When examining patients, the doctor, ceteris paribus, tries to choose a research method that takes less time, but not to the detriment of diagnosis. In this sense, fluoroscopy is more harmful, but, unfortunately, it is often impossible to do without fluoroscopy. So in the study of the esophagus, stomach, intestines, both methods are used. When choosing a research method, we are guided by the rule that the benefits of research should be greater than the harm. Sometimes, due to the fear of taking an extra picture, errors in diagnosis occur, treatment is incorrectly prescribed, which sometimes costs the patient's life. It is necessary to remember about the dangers of radiation, but do not be afraid of it, it is worse for the patient.

3 .Protection distance:

According to the quadratic law of light, the illumination of a given surface is inversely proportional to the square of the distance from the light source to the illuminated surface. In relation to X-ray examination, this means that the radiation dose is inversely proportional to the square of the distance from the focus of the X-ray tube to the patient (focal length). With an increase in the focal length by 2 times, the radiation dose decreases by 4 times, with an increase in the focal length by 3 times, the radiation dose decreases by 9 times.

A focal length of less than 35 cm is not allowed for fluoroscopy. The distance from the walls to the X-ray machine must be at least 2 m, otherwise secondary rays are formed that occur when the primary beam of rays hits the surrounding objects (walls, etc.). For the same reason, extra furniture is not allowed in X-ray rooms. Sometimes, when examining seriously ill patients, the personnel of the surgical and therapeutic departments help the patient stand behind the screen for transillumination and stand next to the patient during the examination, supporting him. As an exception, this is allowed. But the radiologist must make sure that the nurses and nurses helping the sick put on a protective apron and gloves and, if possible, do not stand close to the patient (protection by distance). If several patients came to the X-ray room, they are called to the procedural room by 1 person, i.e. There should only be 1 person at a time in the study.

1. 
   Physical bases of radiography and fluorography. Their shortcomings and advantages. Advantages of digital over film.

For diagnostic radiography, it is advisable to take pictures in at least two projections. This is due to the fact that the radiograph is a flat image of a three-dimensional object. And as a consequence, the localization of the detected pathological focus can be established only with the help of 2 projections.

The quality of the resulting X-ray image is determined by 3 main parameters. The voltage applied to the X-ray tube, the current strength and the operating time of the tube. Depending on the studied anatomical formations, and the weight and size data of the patient, these parameters can vary significantly. There are average values ​​for different organs and tissues, but it should be borne in mind that the actual values ​​will differ depending on the apparatus where the examination is performed and the patient who is being X-rayed. An individual table of values ​​is compiled for each device. These values ​​are not absolute and are adjusted as the study progresses. The quality of the images performed is largely dependent on the ability of the radiographer to adequately adapt the table of average values ​​to a particular patient.

The most common way to record an X-ray image is to fix it on an X-ray sensitive film and then develop it. Currently, there are also systems that provide digital data recording. Due to the high cost and complexity of manufacturing, this type of equipment is somewhat inferior to analog equipment in terms of prevalence.

X-ray film is placed in special devices - cassettes (they say - the cassette is loaded). The cassette protects the film from visible light; the latter, like x-rays, has the ability to reduce metallic silver from AgBr. Cassettes are made of a material that does not transmit light, but transmits x-rays. Inside the cassettes are intensifying screens, the film is laid between them; when taking a picture, not only the X-rays themselves fall on the film, but also the light from the screens (the screens are covered with fluorescent salt, so they glow and enhance the action of the X-rays). This allows you to reduce the radiation load on the patient by 10 times.

When taking a picture, x-rays are directed to the center of the object being photographed (centration). After shooting in a photo lab, the film is developed in special chemicals and fixed (fixed). The fact is that on those parts of the film that were not hit by x-rays during the shooting or there were few of them, silver was not restored, and if the film is not placed in a fixer (fixer) solution, then when examining the film, silver is restored under the influence of visible light. Sveta. The entire film will turn black and no image will be visible. When fixing (fixing), unreduced AgBr from the film goes into the fixer solution, so there is a lot of silver in the fixer, and these solutions are not poured out, but surrendered to X-ray centers.

A modern method of photo processing of medical X-ray films is the use of roller-type processors. In addition to undeniable ease of use, processors provide high stability of the photo processing process. The time of a complete cycle from the moment the film enters the processing machine to the receipt of a dry X-ray pattern ("from dry to dry") does not exceed several minutes.
X-rays are an image made in black and white - a negative. Black - areas with low density (lungs, gas bubble of the stomach. White - with high density (bones).
Fluorography- The essence of FOG is that with it, an image of the chest is first obtained on a fluorescent screen, and then a picture is taken not of the patient himself, but of his image on the screen.

Fluorography gives a reduced image of the object. There are small-frame (for example, 24×24 mm or 35×35 mm) and large-frame (in particular, 70×70 mm or 100×100 mm) techniques. The latter, in terms of diagnostic capabilities, approaches radiography. FOG is used for preventive examination of the population(hidden diseases such as cancer and tuberculosis are detected).

Both stationary and mobile fluorographic devices have been developed.

Currently, film fluorography is gradually being replaced by digital. Digital methods make it possible to simplify work with an image (an image can be displayed on a monitor screen, printed, transmitted over a network, stored in a medical database, etc.), reduce radiation exposure to the patient and reduce the cost of additional materials (film, developer for films).

A conventional film chest fluorogram provides the patient with an average individual radiation dose of 0.5 millisievert (mSv) per procedure (digital fluorogram - 0.05 mSv), while a film radiograph - 0.3 mSv per procedure (digital radiograph - 0 .03 mSv), and computed tomography of the chest - 11 mSv per procedure. Magnetic resonance imaging does not carry radiation exposure

Benefits of radiography

1. 
   Wide availability of the method and ease of research.
2. 
   Most studies do not require special patient preparation.
3. 
   Relatively low cost of research.
4. 
   The images can be used for consultation with another specialist or in another institution (unlike ultrasound images, where a second examination is necessary, since the images obtained are operator-dependent).

1. 
   Static image - the complexity of assessing the function of the body.
2. 
   The presence of ionizing radiation that can have a harmful effect on the patient.
3. 
   The information content of classical radiography is much lower than such modern methods of medical imaging as CT, MRI, etc. Conventional x-ray images reflect the projection layering of complex anatomical structures, that is, their summation x-ray shadow, in contrast to the layered series of images obtained by modern tomographic methods.
4. 
   Without the use of contrast agents, radiography is not informative enough to analyze changes in soft tissues that differ little in density (for example, when studying abdominal organs).

1. 
   Physical bases of roentgenoscopy. Disadvantages and advantages of the method

In modern conditions, the use of a fluorescent screen is not justified due to its low luminosity, which makes it necessary to conduct research in a well-darkened room and after a long adaptation of the researcher to the dark (10-15 minutes) to distinguish a low-intensity image.

Now fluorescent screens are used in the design of X-ray image intensifier, which increases the brightness (glow) of the primary image by about 5,000 times. With the help of an electron-optical converter, the image appears on the monitor screen, which significantly improves the quality of diagnostics, does not require darkening of the X-ray room.

Advantages of fluoroscopy
The main advantage over radiography is the fact of the study in real time. This allows you to evaluate not only the structure of the organ, but also its displacement, contractility or extensibility, the passage of a contrast agent, and fullness. The method also allows you to quickly assess the localization of some changes, due to the rotation of the object of study during transillumination (multi-projection study).

Fluoroscopy allows you to control the implementation of some instrumental procedures - catheter placement, angioplasty (see angiography), fistulography.

The resulting images can be placed on a regular CD or network storage.

With the advent of digital technologies, 3 main disadvantages inherent in traditional fluoroscopy have disappeared:

Relatively high radiation dose compared to radiography - modern low-dose devices have left this disadvantage in the past. The use of pulsed scan modes further reduces the dose load by up to 90%.

Low spatial resolution - on modern digital devices, the resolution in scopy mode is only slightly inferior to the resolution in radiographic mode. In this case, the ability to observe the functional state of individual organs (heart, lungs, stomach, intestines) "in dynamics" is of decisive importance.

The impossibility of documenting research - digital imaging technologies make it possible to save research materials, both frame-by-frame and as a video sequence.

Fluoroscopy is performed mainly in the X-ray diagnosis of diseases of the internal organs located in the abdominal and chest cavities, according to the plan that the radiologist draws up before the start of the study. Sometimes, the so-called survey fluoroscopy is used to recognize traumatic bone injuries, to clarify the area to be radiographed.

Contrast fluoroscopic examination

Artificial contrast greatly expands the possibilities of X-ray examination of organs and systems where tissue densities are approximately the same (for example, the abdominal cavity, whose organs transmit X-rays to approximately the same extent and therefore have low contrast). This is achieved by introducing into the lumen of the stomach or intestines an aqueous suspension of barium sulfate, which does not dissolve in digestive juices, is not absorbed by the stomach or intestines and is excreted naturally in a completely unchanged form. The main advantage of barium suspension is that, passing through the esophagus, stomach and intestines, coats their inner walls and gives a complete picture of the nature of elevations, depressions and other features of their mucous membrane on the screen or film. The study of the internal relief of the esophagus, stomach and intestines contributes to the recognition of a number of diseases of these organs. With more tight filling, it is possible to determine the shape, size, position and function of the organ under study.

1. 
   Mammography - the basics of the method, indications. Advantages of digital mammography over film.

2. differential diagnosis between cancer and benign dyshormonal hyperplasia (FAM) of the breast;

3. assessment of the growth of the primary tumor (single node or multicentric cancerous foci);

4.Dynamic dispensary monitoring of the state of the mammary glands after surgery.

The following methods of radiation diagnostics of breast cancer have been introduced into medical practice: mammography, ultrasound, computed tomography, magnetic resonance imaging, color and power Doppler, mammography-guided stereotaxic biopsy, and thermography.

X-ray mammography
Currently, in the world, in the vast majority of cases, X-ray projection mammography, film (analogue) or digital, is used to diagnose female breast cancer (BC).

The procedure takes no more than 10 minutes. For the shot, the chest should be fixed between two planks and slightly compressed. The picture is taken in two projections so that you can accurately determine the location of the neoplasm, if it is found. Because symmetry is one of the diagnostic factors, both breasts should always be examined.

MRI mammography

Complaints about retraction or bulging of any part of the gland

Discharge from the nipple, changing its shape

Soreness of the mammary gland, its swelling, resizing

Benign breast tumors (particularly fibroadenoma)

Inflammatory processes (mastitis)

Mastopathy

Tumors of the genital organs

Diseases of the endocrine glands (thyroid, pancreas)

Infertility

Obesity

History of breast surgery

Advantages of digital mammography over film:

Reduction of dose loads during X-ray studies;

Improving the efficiency of research, allowing to identify previously inaccessible pathological processes (possibility of digital computer image processing);

Possibilities of using telecommunication networks for transmitting images for the purpose of remote consultation;

Achievement of economic effect during mass research.

The discovery and merit in the study of the basic properties of X-rays rightfully belongs to the German scientist Wilhelm Conrad Roentgen. The amazing properties of X-rays discovered by him immediately received a huge response in the scientific world. Although then, back in 1895, the scientist could hardly imagine what benefit, and sometimes harm, X-rays can bring.

Let's find out in this article how this type of radiation affects human health.

What is x-ray radiation

The first question that interested the researcher was what is X-ray radiation? A number of experiments made it possible to verify that this is electromagnetic radiation with a wavelength of 10 -8 cm, which occupies an intermediate position between ultraviolet and gamma radiation.

Application of X-rays

All these aspects of the destructive effects of the mysterious X-rays do not at all exclude surprisingly extensive aspects of their application. Where is X-rays used?

1. Study of the structure of molecules and crystals.
2. X-ray flaw detection (in industry, detection of defects in products).
3. Methods of medical research and therapy.

The most important applications of X-rays have become possible due to the very short wavelengths of the entire range of these waves and their unique properties.

Since we are interested in the impact of X-rays on people who encounter them only during a medical examination or treatment, then we will only consider this area of ​​application of X-rays.

The use of x-rays in medicine

Despite the special significance of his discovery, Roentgen did not take out a patent for its use, making it an invaluable gift for all mankind. Already in the First World War, X-ray units began to be used, which made it possible to quickly and accurately diagnose the wounded. Now we can distinguish two main areas of application of x-rays in medicine:

• X-ray diagnostics;
• x-ray therapy.

X-ray diagnostics

X-ray diagnostics is used in various options:

Let's take a look at the difference between these methods.

All of the above diagnostic methods are based on the ability of X-rays to illuminate photographic film and on their different permeability to tissues and the bone skeleton.

X-ray therapy

The ability of X-rays to have a biological effect on tissues is used in medicine for the treatment of tumors. The ionizing effect of this radiation is most actively manifested in the effect on rapidly dividing cells, which are the cells of malignant tumors.

However, you should also be aware of the side effects that inevitably accompany radiotherapy. The fact is that cells of the hematopoietic, endocrine, and immune systems are also rapidly dividing. A negative impact on them gives rise to signs of radiation sickness.

The effect of X-ray radiation on humans

Shortly after the remarkable discovery of X-rays, it was discovered that X-rays had an effect on humans.

These data were obtained in experiments on experimental animals, however, geneticists suggest that similar effects may apply to the human body.

The study of the effects of X-ray exposure has led to the development of international standards for acceptable radiation doses.

Doses of x-ray radiation in x-ray diagnostics

After visiting the X-ray room, many patients are worried - how will the received dose of radiation affect their health?

The dose of general irradiation of the body depends on the nature of the procedure. For convenience, we will compare the received dose with natural exposure, which accompanies a person throughout his life.

1. X-ray: chest - the received dose of radiation is equivalent to 10 days of background exposure; upper stomach and small intestine - 3 years.
2. Computed tomography of the abdominal cavity and pelvis, as well as the whole body - 3 years.
3. Mammography - 3 months.
4. Radiography of the extremities is practically harmless.
5. With regard to dental x-rays, the radiation dose is minimal, since the patient is exposed to a narrow beam of x-rays with a short radiation duration.

These radiation doses meet acceptable standards, but if the patient feels anxious before the X-ray, he has the right to ask for a special protective apron.

Exposure of X-rays to pregnant women

Each person has to undergo X-ray examination repeatedly. But there is a rule - this diagnostic method cannot be prescribed to pregnant women. The developing embryo is extremely vulnerable. X-rays can cause chromosome abnormalities and, as a result, the birth of children with malformations. The most vulnerable in this regard is the gestational age of up to 16 weeks. Moreover, the most dangerous for the future baby is an x-ray of the spine, pelvic and abdominal regions.

Knowing about the detrimental effect of x-rays on pregnancy, doctors avoid using it in every possible way during this crucial period in a woman's life.

However, there are side sources of X-rays:

• electron microscopes;
• color TV kinescopes, etc.

Expectant mothers should be aware of the danger posed by them.

For nursing mothers, radiodiagnosis is not dangerous.

What to do after an x-ray

To avoid even the minimal effects of X-ray exposure, some simple steps can be taken:

• after an x-ray, drink a glass of milk - it removes small doses of radiation;
• very handy taking a glass of dry wine or grape juice;
• some time after the procedure, it is useful to increase the proportion of foods with a high content of iodine (seafood).

But, no medical procedures or special measures are required to remove radiation after an x-ray!

Despite the undoubtedly serious consequences of exposure to X-rays, one should not overestimate their danger during medical examinations - they are carried out only in certain areas of the body and very quickly. The benefits of them many times exceed the risk of this procedure for the human body.

X-ray radiation - a type of radiation with a frequency in the range from 3 * 10 16 to 3 * 10 20 Hz.

History of the discovery of X-rays

X-rays were discovered in 1895 by the German Wilhelm Roentgen. At the end of the 19th century, scientists were engaged in the study of gas discharge at low pressure. In this case, flows of electrons moving at high speed were created in the gas-discharge tube. V. Roentgen also took up the study of these rays.

He noticed that if a photographic plate is placed next to the gas discharge tube, it will be illuminated, even if it is wrapped in black paper. Continuing to set up experiments, Roentgen wrapped the gas-discharge tube with paper soaked in a solution of barium platinum-cyanide. The paper began to glow.

X-ray was curious, and placed his hand between the paper and the tube, in the hope, probably, that it would begin to glow, but this did not happen. But on the paper screen, the dark shadows of the bones remained visible against the background of the lighter outlines of the hand. Roentgen suggested that this is some unknown radiation that has a very strong penetrating effect.

• He called these rays X-rays. Subsequently, these rays became known as x-rays.

X-ray properties

X-rays are not affected by an electromagnetic field. At the same time, they practically did not experience refraction and were not reflected. There was an assumption that X-rays are electromagnetic waves that are emitted when electrons decelerate.

• They have very short wavelength owing to which they have such a high penetrating power.

Now the attention of scientists was riveted to the study of x-rays. They tried to detect the diffraction of these rays. Passed them through the cracks in the plates, but found no effect. Some time later, the German Max Laue suggested passing X-rays through crystals.

He substantiated this by the fact that perhaps the wavelength of X-ray radiation is comparable to the size of atoms, and therefore it will not be possible to achieve diffraction on artificial slits. Therefore, one should use crystals that have a clear structure and the distance between atoms is approximately equal to the size of the atoms themselves. Laue's assumptions were confirmed.

After passing X-rays through the crystal, approximately the following picture appeared on the screen.

The appearance of additional small spots could only be explained by the phenomenon of X-ray diffraction on the internal structure of the crystal. Upon further investigation, it turned out that the wavelength of X-ray radiation was indeed equal in order of magnitude to the size of atoms.

X-rays are widely used in practice. In medicine, scientific research, technology. With the help of X-rays, flaw detection of various structures, the search for black holes and fractures in the bones of people are carried out.