X-ray length. What characterizes this type of radiation. Radiation - harm and benefit

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 these diagnostic methods are based on the ability of x-rays to illuminate 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-rays, invisible radiation capable of penetrating, albeit to varying degrees, all substances. It is electromagnetic radiation with a wavelength of about 10-8 cm.

Like visible light, X-rays cause blackening of photographic film. This property is of great importance for medicine, industry and scientific research. Passing through the object under study and then falling on the film, X-ray radiation depicts its internal structure on it. Since the penetrating power of X-ray radiation is different for different materials, parts of the object that are less transparent to it give brighter areas in the photograph than those through which the radiation penetrates well. Thus, bone tissues are less transparent to x-rays than the tissues that make up the skin and internal organs. Therefore, on the radiograph, the bones will be indicated as lighter areas and the fracture site, which is more transparent for radiation, can be quite easily detected. X-ray imaging is also used in dentistry to detect caries and abscesses in the roots of teeth, as well as in industry to detect cracks in castings, plastics and rubbers.

X-rays are used in chemistry to analyze compounds and in physics to study the structure of crystals. An X-ray beam passing through a chemical compound causes a characteristic secondary radiation, the spectroscopic analysis of which allows the chemist to determine the composition of the compound. When falling on a crystalline substance, an X-ray beam is scattered by the atoms of the crystal, giving a clear, regular pattern of spots and stripes on a photographic plate, which makes it possible to establish the internal structure of the crystal.

The use of X-rays in cancer treatment is based on the fact that it kills cancer cells. However, it can also have an undesirable effect on normal cells. Therefore, extreme caution must be exercised in this use of X-rays.

Getting x-rays

X-ray radiation occurs when electrons moving at high speeds interact with matter. When electrons collide with atoms of any substance, they quickly lose their kinetic energy. In this case, most of it is converted into heat, and a small fraction, usually less than 1%, is converted into X-ray energy. This energy is released in the form of quanta - particles called photons that have energy but have zero rest mass. X-ray photons differ in their energy, which is inversely proportional to their wavelength. With the usual method of obtaining X-rays, a wide range of wavelengths is obtained, which is called the X-ray spectrum.

X-ray tubes. In order to obtain X-ray radiation due to the interaction of electrons with matter, it is necessary to have a source of electrons, means of accelerating them to high speeds, and a target capable of withstanding electron bombardment and producing X-ray radiation of the required intensity. The device that has all this is called an x-ray tube. Early explorers used "deep vacuum" tubes such as today's discharge tubes. The vacuum in them was not very high.

Discharge tubes contain a small amount of gas, and when a large potential difference is applied to the electrodes of the tube, the gas atoms turn into positive and negative ions. The positive ones move towards the negative electrode (cathode) and, falling on it, knock electrons out of it, and they, in turn, move towards the positive electrode (anode) and, bombarding it, create a stream of X-ray photons.

In the modern X-ray tube developed by Coolidge (Fig. 11), the source of electrons is a tungsten cathode heated to a high temperature.

Rice. eleven.

The electrons are accelerated to high speeds by the high potential difference between the anode (or anticathode) and the cathode. Since the electrons must reach the anode without colliding with atoms, a very high vacuum is required, for which the tube must be well evacuated. This also reduces the probability of ionization of the remaining gas atoms and the associated side currents.

When bombarded with electrons, the tungsten anticathode emits characteristic x-rays. The cross section of the X-ray beam is less than the actual irradiated area. 1 - electron beam; 2 - cathode with a focusing electrode; 3 - glass shell (tube); 4 - tungsten target (anticathode); 5 - cathode filament; 6 - actually irradiated area; 7 - effective focal spot; 8 - copper anode; 9 - window; 10 - scattered x-rays.

The electrons are focused on the anode by a specially shaped electrode surrounding the cathode. This electrode is called the focusing electrode and, together with the cathode, forms the "electronic spotlight" of the tube. The anode subjected to electron bombardment must be made of a refractory material, since most of the kinetic energy of the bombarding electrons is converted into heat. In addition, it is desirable that the anode be made of a material with a high atomic number, since the x-ray yield increases with increasing atomic number. Tungsten, whose atomic number is 74, is most often chosen as the anode material. The design of X-ray tubes can be different depending on the application conditions and requirements.

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 that has a high melting point, such as tungsten.

Part of the energy that does not dissipate 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 tomography 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.

Modern medicine uses many physicians for diagnosis and therapy. Some of them have been used relatively recently, while others have been practiced for more than a dozen or even hundreds of years. Also, a hundred and ten years ago, William Conrad Roentgen discovered the amazing X-rays, which caused a significant resonance in the scientific and medical world. And now doctors all over the planet use them in their practice. The topic of our today's conversation will be X-rays in medicine, we will discuss their application in a little more detail.

X-rays are one of the varieties of electromagnetic radiation. They are characterized by significant penetrating qualities, which depend on the wavelength of radiation, as well as on the density and thickness of the irradiated materials. In addition, X-rays can cause the glow of a number of substances, affect living organisms, ionize atoms, and also catalyze some photochemical reactions.

The use of X-rays in medicine

To date, the properties of x-rays allow them to be widely used in x-ray diagnostics and x-ray therapy.

X-ray diagnostics

X-ray diagnostics is used when carrying out:

X-ray (transmission);
- radiography (picture);
- fluorography;
- X-ray and computed tomography.

Fluoroscopy

To conduct such a study, the patient needs to position himself between the X-ray tube and a special fluorescent screen. A specialist radiologist selects the required hardness of the X-rays, receiving on the screen a picture of the internal organs, as well as the ribs.

Radiography

For this study, the patient is placed on a cassette containing a special film. The X-ray machine is placed directly above the object. As a result, a negative image of the internal organs appears on the film, which contains a number of fine details, more detailed than during a fluoroscopic examination.

Fluorography

This study is carried out during mass medical examinations of the population, including for the detection of tuberculosis. At the same time, a picture from a large screen is projected onto a special film.

Tomography

When conducting tomography, computer beams help to obtain images of organs in several places at once: in specially selected transverse sections of tissue. This series of x-rays is called a tomogram.

Computed tomogram

Such a study allows you to register sections of the human body by using an X-ray scanner. After the data is entered into the computer, getting one picture in cross section.

Each of the listed diagnostic methods is based on the properties of the X-ray beam to illuminate the film, as well as on the fact that human tissues and bone skeleton differ in different permeability to their effects.

X-ray therapy

The ability of X-rays to influence tissues in a special way is used to treat tumor formations. At the same time, the ionizing qualities of this radiation are especially actively noticeable when exposed to cells that are capable of rapid division. It is these qualities that distinguish the cells of malignant oncological formations.

However, it is worth noting that X-ray therapy can cause a lot of serious side effects. Such an impact aggressively affects the state of the hematopoietic, endocrine and immune systems, the cells of which also divide very quickly. Aggressive influence on them can cause signs of radiation sickness.

The effect of X-ray radiation on humans

During the study of x-rays, doctors found that they can lead to changes in the skin that resemble a sunburn, but are accompanied by deeper damage to the skin. Such ulcers heal for a very long time. Scientists have found that such lesions can be avoided by reducing the time and dose of radiation, as well as using special shielding and remote control methods.

The aggressive influence of X-rays can also manifest itself in the long term: temporary or permanent changes in the composition of the blood, susceptibility to leukemia and early aging.

The effect of x-rays on a person depends on many factors: on which organ is irradiated, and for how long. Irradiation of the hematopoietic organs can lead to blood ailments, and exposure to the genital organs can lead to infertility.

Carrying out systematic irradiation is fraught with the development of genetic changes in the body.

The real harm of x-rays in x-ray diagnostics

During the examination, doctors use the minimum possible amount of x-rays. All radiation doses meet certain acceptable standards and cannot harm a person. X-ray diagnostics poses a significant danger only for the doctors who carry it out. And then modern methods of protection help to reduce the aggression of the rays to a minimum.

The safest methods of radiodiagnosis include radiography of the extremities, as well as dental x-rays. In the next place of this rating is mammography, followed by computed tomography, and after it is radiography.

In order for the use of X-rays in medicine to bring only benefit to a person, it is necessary to conduct research with their help only according to indications.

Modern medical diagnostics and treatment of certain diseases cannot be imagined without devices that use the properties of X-rays. The discovery of X-rays occurred more than 100 years ago, but even now work continues on the creation of new methods and apparatus to minimize the negative effect of radiation on the human body.

Who and how discovered X-rays

Under natural conditions, the flux of X-rays is rare and is emitted only by certain radioactive isotopes. X-rays or X-rays were only discovered in 1895 by the German scientist Wilhelm Röntgen. This discovery happened by chance, during an experiment to study the behavior of light rays under conditions approaching vacuum. The experiment involved a cathode gas discharge tube with reduced pressure and a fluorescent screen, which each time began to glow at the moment when the tube began to act.

Interested in a strange effect, Roentgen conducted a series of studies showing that the resulting radiation, invisible to the eye, is able to penetrate various obstacles: paper, wood, glass, some metals, and even through the human body. Despite the lack of understanding of the very nature of what is happening, whether such a phenomenon is caused by the generation of a stream of unknown particles or waves, the following pattern was noted - radiation easily passes through the soft tissues of the body, and much harder through solid living tissues and inanimate substances.

Roentgen was not the first to study this phenomenon. In the middle of the 19th century, Frenchman Antoine Mason and Englishman William Crookes studied similar possibilities. However, it was Roentgen who first invented the cathode tube and an indicator that could be used in medicine. He was the first to publish a scientific work, which brought him the title of the first Nobel laureate among physicists.

In 1901, a fruitful collaboration began between the three scientists, who became the founding fathers of radiology and radiology.

X-ray properties

X-rays are an integral part of the general spectrum of electromagnetic radiation. The wavelength is between gamma and ultraviolet rays. X-rays have all the usual wave properties:

• diffraction;
• refraction;
• interference;
• propagation speed (it is equal to light).

To artificially generate an X-ray flux, special devices are used - X-ray tubes. X-ray radiation arises from the contact of fast tungsten electrons with substances evaporating from a hot anode. Against the background of interaction, short-length electromagnetic waves arise, which are in the spectrum from 100 to 0.01 nm and in the energy range of 100-0.1 MeV. If the wavelength of the rays is less than 0.2 nm - this is hard radiation, if the wavelength is greater than the specified value, they are called soft x-rays.

It is significant that the kinetic energy arising from the contact of electrons and the anode substance is 99% converted into heat energy and only 1% is X-rays.

X-ray radiation - bremsstrahlung and characteristic

X-radiation is a superposition of two types of rays - bremsstrahlung and characteristic. They are generated in the handset simultaneously. Therefore, X-ray irradiation and the characteristic of each specific X-ray tube - the spectrum of its radiation, depends on these indicators, and represents their superposition.

Bremsstrahlung or continuous X-rays are the result of deceleration of electrons evaporating from a tungsten filament.

Characteristic or line X-rays are formed at the moment of rearrangement of the atoms of the substance of the anode of the X-ray tube. The wavelength of the characteristic rays directly depends on the atomic number of the chemical element used to make the anode of the tube.

The listed properties of X-rays allow them to be used in practice:

• invisible to the ordinary eye;
• high penetrating ability through living tissues and inanimate materials that do not transmit visible light;
• ionization effect on molecular structures.

Principles of X-ray Imaging

The property of x-rays on which imaging is based is the ability to either decompose or cause some substances to glow.

X-ray irradiation causes a fluorescent glow in cadmium and zinc sulfides - green, and in calcium tungstate - blue. This property is used in the technique of medical X-ray transillumination, and also increases the functionality of X-ray screens.

The photochemical effect of X-rays on light-sensitive silver halide materials (illumination) makes it possible to carry out diagnostics - to take X-ray images. This property is also used in measuring the amount of the total dose that laboratory assistants receive in X-ray rooms. Wearable dosimeters have special sensitive tapes and indicators. The ionizing effect of X-ray radiation makes it possible to determine the qualitative characteristics of the obtained X-rays.

A single exposure to conventional X-rays increases the risk of cancer by only 0.001%.

Areas where X-rays are used

The use of X-rays is acceptable in the following industries:

1. Safety. Fixed and portable devices for detecting dangerous and prohibited items at airports, customs or in crowded places.
2. Chemical industry, metallurgy, archeology, architecture, construction, restoration work - to detect defects and conduct chemical analysis of substances.
3. Astronomy. It helps to observe cosmic bodies and phenomena with the help of X-ray telescopes.
4. military industry. For the development of laser weapons.

The main application of X-rays is in the medical field. Today, the section of medical radiology includes: radiodiagnostics, radiotherapy (X-ray therapy), radiosurgery. Medical universities produce highly specialized specialists - radiologists.

X-Radiation - harm and benefit, effects on the body

The high penetrating power and ionizing effect of X-rays can cause a change in the structure of the DNA of the cell, therefore it is dangerous for humans. The harm from X-ray radiation is directly proportional to the received radiation dose. Different organs respond to irradiation to varying degrees. The most susceptible include:

• bone marrow and bone tissue;
• lens of the eye;
• thyroid;
• mammary and sex glands;
• lung tissue.

Uncontrolled use of X-ray radiation can cause reversible and irreversible pathologies.

Consequences of X-ray exposure:

• damage to the bone marrow and the occurrence of pathologies of the hematopoietic system - erythrocytopenia, thrombocytopenia, leukemia;
• damage to the lens, with the subsequent development of cataracts;
• cellular mutations that are inherited;
• development of oncological diseases;
• getting radiation burns;
• development of radiation sickness.

Important! Unlike radioactive substances, X-rays do not accumulate in the tissues of the body, which means that there is no need to remove X-rays from the body. The harmful effect of X-rays ends when the medical device is turned off.

The use of X-rays in medicine is permissible not only for diagnostic (traumatology, dentistry), but also for therapeutic purposes:

• from x-rays in small doses, the metabolism in living cells and tissues is stimulated;
• certain limiting doses are used for the treatment of oncological and benign neoplasms.

Methods for diagnosing pathologies using X-rays

Radiodiagnostics includes the following methods:

1. Fluoroscopy is a study in which an image is obtained on a fluorescent screen in real time. Along with the classical real-time imaging of a body part, today there are X-ray television transillumination technologies - the image is transferred from a fluorescent screen to a television monitor located in another room. Several digital methods have been developed for processing the resulting image, followed by transferring it from the screen to paper.
2. Fluorography is the cheapest method for examining the chest organs, which consists in making a small picture of 7x7 cm. Despite the possibility of error, it is the only way to conduct a mass annual examination of the population. The method is not dangerous and does not require the withdrawal of the received radiation dose from the body.
3. Radiography - obtaining a summary image on film or paper to clarify the shape of an organ, its position or tone. Can be used to assess peristalsis and the condition of the mucous membranes. If there is a choice, then among modern X-ray devices, preference should be given neither to digital devices, where the x-ray flux can be higher than that of old devices, but to low-dose X-ray devices with direct flat semiconductor detectors. They allow you to reduce the load on the body by 4 times.
4. Computed X-ray tomography is a technique that uses x-rays to obtain the required number of images of sections of a selected organ. Among the many varieties of modern CT devices, low-dose high-resolution CT scanners are used for a series of repeated studies.

Radiotherapy

X-ray therapy refers to local treatment methods. Most often, the method is used to destroy cancer cells. Since the effect of exposure is comparable to surgical removal, this treatment method is often called radiosurgery.

Today, x-ray treatment is carried out in the following ways:

1. External (proton therapy) - the radiation beam enters the patient's body from the outside.
2. Internal (brachytherapy) - the use of radioactive capsules by implanting them into the body, with the placement closer to the cancerous tumor. The disadvantage of this method of treatment is that until the capsule is removed from the body, the patient needs to be isolated.

These methods are gentle, and their use is preferable to chemotherapy in some cases. Such popularity is due to the fact that the rays do not accumulate and do not require removal from the body, they have a selective effect, without affecting other cells and tissues.

Safe X-ray exposure rate

This indicator of the norm of permissible annual exposure has its own name - a genetically significant equivalent dose (GED). There are no clear quantitative values ​​for this indicator.

1. This indicator depends on the age and desire of the patient to have children in the future.
2. It depends on which organs were examined or treated.
3. The GZD is affected by the level of natural radioactive background of the region where a person lives.

Today, the following average GZD standards are in effect:

• the level of exposure from all sources, with the exception of medical ones, and without taking into account the natural radiation background - 167 mRem per year;
• the norm for an annual medical examination is not more than 100 mRem per year;
• the total safe value is 392 mRem per year.

X-ray radiation does not require excretion from the body, and is dangerous only in case of intense and prolonged exposure. Modern medical equipment uses low-energy radiation of short duration, so its use is considered relatively harmless.