x-ray radiation, from the point of view of physics, this is electromagnetic radiation, the wavelength of which varies in the range from 0.001 to 50 nanometers. It was discovered in 1895 by the German physicist W.K. Roentgen.

By nature, these rays are related to solar ultraviolet. Radio waves are the longest in the spectrum. They are followed by infrared light, which our eyes do not perceive, but we feel it as heat. Next come the rays from red to purple. Then - ultraviolet (A, B and C). And right behind it are x-rays and gamma rays.

X-ray can be obtained in two ways: by deceleration in the matter of charged particles passing through it and by the transition of electrons from the upper layers to the internal ones when energy is released.

Unlike visible light, these rays are very long, so they are able to penetrate opaque materials without being reflected, refracted, or accumulated in them.

Bremsstrahlung is easier to obtain. Charged particles emit electromagnetic radiation when braking. The greater the acceleration of these particles and, consequently, the sharper the deceleration, the more X-rays are produced, and the wavelength becomes shorter. In most cases, in practice, they resort to the generation of rays in the process of deceleration of electrons in solids. This allows you to control the source of this radiation, avoiding the danger of radiation exposure, because when the source is turned off, the X-ray emission completely disappears.

The most common source of such radiation - The radiation emitted by it is inhomogeneous. It contains both soft (long-wave) and hard (short-wave) radiation. The soft one is characterized by the fact that it is completely absorbed by the human body, therefore such X-ray radiation does twice as much harm as the hard one. With excessive electromagnetic radiation in the tissues of the human body, ionization can damage cells and DNA.

The tube is with two electrodes - a negative cathode and a positive anode. When the cathode is heated, electrons evaporate from it, then they are accelerated in an electric field. Colliding with the solid matter of the anodes, they begin deceleration, which is accompanied by the emission of electromagnetic radiation.

X-ray radiation, the properties of which are widely used in medicine, is based on obtaining a shadow image of the object under study on a sensitive screen. If the diagnosed organ is illuminated with a beam of rays parallel to each other, then the projection of shadows from this organ will be transmitted without distortion (proportionally). In practice, the radiation source is more like a point source, so it is located at a distance from the person and from the screen.

To receive a person is placed between the x-ray tube and the screen or film, acting as radiation receivers. As a result of irradiation, bone and other dense tissues appear in the image as clear shadows, look more contrast against the background of less expressive areas that transmit tissues with less absorption. On x-rays, a person becomes "translucent".

As X-rays propagate, they can be scattered and absorbed. Before absorption, the rays can travel hundreds of meters in the air. In dense matter, they are absorbed much faster. Human biological tissues are heterogeneous, so their absorption of rays depends on the density of the tissue of the organs. absorbs rays faster than soft tissues, because it contains substances that have large atomic numbers. Photons (individual particles of rays) are absorbed by different tissues of the human body in different ways, which makes it possible to obtain a contrast image using x-rays.

X-ray radiation plays a huge role in modern medicine; the history of the discovery of X-rays dates back to the 19th century.

X-rays are electromagnetic waves, which are formed with the participation of electrons. With strong acceleration of charged particles, artificial x-rays are created. It passes through special equipment:

  • particle accelerators.

Discovery history

These rays were invented in 1895 by the German scientist Roentgen: while working with a cathode ray tube, he discovered the fluorescence effect of barium platinum cyanide. Then there was a description of such rays and their amazing ability to penetrate the tissues of the body. The rays began to be called x-rays (x-rays). Later in Russia they began to be called X-ray.

X-rays are able to penetrate even through walls. So Roentgen realized what he had done greatest discovery in medecine. It was from that time that separate sections in science began to form, such as radiology and radiology.

The rays are able to penetrate soft tissues, but are delayed, their length is determined by the obstacle of a hard surface. soft tissue in human body is the skin, and the hard ones are the bones. In 1901, the scientist was awarded the Nobel Prize.

However, even before the discovery of Wilhelm Conrad Roentgen, other scientists were also interested in a similar topic. In 1853, the French physicist Antoine-Philiber Mason studied a high-voltage discharge between electrodes in a glass tube. The gas contained in it at low pressure began to emit a reddish glow. Pumping out excess gas from the tube led to the decay of the glow into a complex sequence of individual luminous layers, the hue of which depended on the amount of gas.

In 1878, William Crookes (English physicist) suggested that fluorescence occurs due to the impact of rays on the glass surface of the tube. But all these studies were not published anywhere, so Roentgen did not know about such discoveries. After the publication of his discoveries in 1895 in scientific journal, where the scientist wrote that all bodies are transparent to these rays, although to a very different degree, other scientists became interested in similar experiments. They confirmed the invention of Roentgen, and further development and improvement of x-rays began.

Wilhelm Roentgen himself published two more scientific work on the subject of x-rays in 1896 and 1897, after which he took up other activities. Thus, several scientists invented, but it was Roentgen who published scientific papers on this subject.


Imaging Principles

The features of this radiation are determined by the very nature of their appearance. Radiation occurs due to an electromagnetic wave. Its main properties include:

  1. Reflection. If the wave hits the surface perpendicularly, it will not be reflected. In some situations, a diamond has the property of reflection.
  2. The ability to penetrate tissue. In addition, the rays can pass through opaque surfaces of materials such as wood, paper, and the like.
  3. absorbency. Absorption depends on the density of the material: the denser it is, the more X-rays absorb it.
  4. Some substances fluoresce, that is, they glow. As soon as the radiation stops, the glow also disappears. If it continues after the cessation of the action of the rays, then this effect is called phosphorescence.
  5. X-rays can illuminate photographic film, just like visible light.
  6. If the beam passed through the air, then ionization occurs in the atmosphere. This state is called electrically conductive, and it is determined using a dosimeter, which sets the rate of radiation dosage.

Radiation - harm and benefit

When the discovery was made, the physicist Roentgen could not even imagine how dangerous his invention was. In the old days, all devices that produced radiation were far from perfect, and as a result, large doses of emitted rays were obtained. People did not understand the dangers of such radiation. Although some scientists even then put forward versions about the dangers of x-rays.


X-rays, penetrating into tissues, have a biological effect on them. The unit of measurement of radiation dose is roentgen per hour. The main influence is on the ionizing atoms that are inside the tissues. These rays act directly on the DNA structure of a living cell. The consequences of uncontrolled radiation include:

  • cell mutation;
  • the appearance of tumors;
  • radiation burns;
  • radiation sickness.

Contraindications for X-ray examinations:

  1. The patients are in critical condition.
  2. Pregnancy period due to negative effects on the fetus.
  3. Patients with bleeding or open pneumothorax.

How x-rays work and where it is used

  1. In medicine. X-ray diagnostics is used to translucent living tissues in order to identify certain disorders within the body. X-ray therapy is performed to eliminate tumor formations.
  2. In science. The structure of substances and the nature of X-rays are revealed. These issues are dealt with by such sciences as chemistry, biochemistry, crystallography.
  3. In industry. To detect violations in metal products.
  4. For the safety of the population. X-ray beams are installed at airports and other public places to scan luggage.


Medical use of X-ray radiation. X-rays are widely used in medicine and dentistry for the following purposes:

  1. For diagnosing diseases.
  2. For monitoring metabolic processes.
  3. For the treatment of many diseases.

The use of X-rays for medical purposes

In addition to detecting bone fractures, x-rays are widely used in medicinal purposes. The specialized application of x-rays is to achieve the following goals:

  1. To destroy cancer cells.
  2. To reduce the size of the tumor.
  3. To reduce pain.

For example, radioactive iodine, used in endocrinological diseases, is actively used in thyroid cancer, thereby helping many people get rid of this disease. terrible disease. Currently, to diagnose complex diseases, X-rays are connected to computers, as a result, the latest research methods appear, such as computed axial tomography.

These scans provide doctors with color images that show internal organs person. To detect the work of internal organs, a small dose of radiation is sufficient. X-rays are also widely used in physiotherapy.


Basic properties of X-rays

  1. penetrating ability. All bodies are transparent to the x-ray, and the degree of transparency depends on the thickness of the body. It is thanks to this property that the beam began to be used in medicine to detect the functioning of organs, the presence of fractures and foreign bodies in organism.
  2. They are able to cause the glow of some objects. For example, if barium and platinum are applied to cardboard, then, after passing through the beam scanning, it will glow greenish-yellow. If you place your hand between the X-ray tube and the screen, then the light will penetrate more into the bone than into the tissue, so the bone tissue will shine brightest on the screen, and the muscle tissue will be less bright.
  3. Action on film. X-rays can, like light, darken film, which makes it possible to photograph the shadow side that is obtained when objects are examined by x-rays.
  4. X-rays can ionize gases. This makes it possible not only to find rays, but also to reveal their intensity by measuring the ionization current in the gas.
  5. They have a biochemical effect on the body of living beings. Thanks to this property, X-rays have found their wide application in medicine: they can treat both skin diseases and diseases of the internal organs. In this case, the desired dosage of radiation and the duration of the rays are selected. Prolonged and excessive use of such treatment is very harmful and detrimental to the body.

The consequence of the use of X-rays was the salvation of many human lives. X-ray helps not only to diagnose the disease in a timely manner, treatment methods using radiation therapy relieve patients of various pathologies, from hyperfunction of the thyroid gland to malignant tumors of bone tissues.

X-ray radiation (synonymous with X-rays) is with a wide range of wavelengths (from 8·10 -6 to 10 -12 cm). X-ray radiation occurs when charged particles, most often electrons, decelerate in the electric field of the atoms of a substance. The resulting quanta have different energies and form a continuous spectrum. The maximum photon energy in such a spectrum is equal to the energy of incident electrons. In (see) the maximum energy of X-ray quanta, expressed in kiloelectron-volts, is numerically equal to the magnitude of the voltage applied to the tube, expressed in kilovolts. When passing through a substance, X-rays interact with the electrons of its atoms. For X-ray quanta with energies up to 100 keV, the most characteristic type of interaction is the photoelectric effect. As a result of such an interaction, the quantum energy is completely spent on pulling out an electron from the atomic shell and imparting kinetic energy to it. With an increase in the energy of an X-ray quantum, the probability of the photoelectric effect decreases and the process of scattering of quanta on free electrons becomes predominant - the so-called Compton effect. As a result of such an interaction, a secondary electron is also formed and, in addition, a quantum with an energy less than the energy of the primary quantum flies out. If the energy of an X-ray quantum exceeds one megaelectron-volt, a so-called pairing effect can occur, in which an electron and a positron are formed (see). Consequently, when passing through a substance, the energy of X-ray radiation decreases, i.e., its intensity decreases. Since low-energy quanta are more likely to be absorbed in this case, X-ray radiation is enriched with higher-energy quanta. This property of X-ray radiation is used to increase the average energy of quanta, i.e., to increase its rigidity. An increase in the hardness of X-ray radiation is achieved using special filters (see). X-ray radiation is used for X-ray diagnostics (see) and (see). See also Ionizing radiation.

X-ray radiation (synonym: x-rays, x-rays) - quantum electromagnetic radiation with a wavelength of 250 to 0.025 A (or energy quanta from 5 10 -2 to 5 10 2 keV). In 1895, it was discovered by V.K. Roentgen. The spectral region of electromagnetic radiation adjacent to x-rays, whose energy quanta exceed 500 keV, is called gamma radiation (see); radiation, whose energy quanta are below 0.05 keV, is ultraviolet radiation (see).

Thus, representing a relatively small part of the vast spectrum of electromagnetic radiation, which includes both radio waves and visible light, X-ray radiation, like any electromagnetic radiation, propagates at the speed of light (about 300 thousand km / s in a vacuum) and is characterized by a wavelength λ ( the distance over which the radiation propagates in one period of oscillation). X-ray radiation also has a number of other wave properties (refraction, interference, diffraction), but it is much more difficult to observe them than for longer-wavelength radiation: visible light, radio waves.

X-ray spectra: a1 - continuous bremsstrahlung spectrum at 310 kV; a - continuous bremsstrahlung spectrum at 250 kV, a1 - spectrum filtered by 1 mm Cu, a2 - spectrum filtered by 2 mm Cu, b - K-series of the tungsten line.

To generate x-rays, x-ray tubes are used (see), in which radiation occurs when fast electrons interact with atoms of the anode substance. There are two types of x-rays: bremsstrahlung and characteristic. Bremsstrahlung X-ray radiation, which has a continuous spectrum, is similar to ordinary white light. The distribution of intensity depending on the wavelength (Fig.) is represented by a curve with a maximum; in the direction of long waves, the curve falls gently, and in the direction of short waves, it steeply and breaks off at a certain wavelength (λ0), called the short-wavelength boundary of the continuous spectrum. The value of λ0 is inversely proportional to the voltage on the tube. Bremsstrahlung arises from the interaction of fast electrons with atomic nuclei. The bremsstrahlung intensity is directly proportional to the strength of the anode current, the square of the tube voltage, and the atomic number (Z) of the anode material.

If the energy of electrons accelerated in the X-ray tube exceeds the critical value for the anode substance (this energy is determined by the tube voltage Vcr, which is critical for this substance), then characteristic radiation occurs. The characteristic spectrum is line, its spectral lines form a series, denoted by the letters K, L, M, N.

The K series is the shortest wavelength, the L series is longer wavelength, the M and N series are observed only in heavy elements (Vcr of tungsten for the K-series is 69.3 kv, for the L-series - 12.1 kv). Characteristic radiation arises as follows. Fast electrons knock atomic electrons out of the inner shells. The atom is excited and then returns to the ground state. In this case, electrons from the outer, less bound shells fill the spaces vacated in the inner shells, and photons of characteristic radiation with an energy equal to the difference between the energies of the atom in the excited and ground states are emitted. This difference (and hence the energy of the photon) has a certain value, characteristic of each element. This phenomenon underlies the X-ray spectral analysis of elements. The figure shows the line spectrum of tungsten against the background of a continuous spectrum of bremsstrahlung.

The energy of electrons accelerated in the X-ray tube is converted almost entirely into thermal energy (the anode is strongly heated in this case), only an insignificant part (about 1% at a voltage close to 100 kV) is converted into bremsstrahlung energy.

The use of x-rays in medicine is based on the laws of absorption of x-rays by matter. The absorption of x-rays is completely independent of the optical properties of the absorber material. The colorless and transparent lead glass used to protect personnel in x-ray rooms absorbs x-rays almost completely. In contrast, a sheet of paper that is not transparent to light does not attenuate X-rays.

The intensity of a homogeneous (i.e., a certain wavelength) X-ray beam, when passing through an absorber layer, decreases according to an exponential law (e-x), where e is the base of natural logarithms (2.718), and the exponent x is equal to the product of the mass attenuation coefficient (μ / p) cm 2 /g per absorber thickness in g / cm 2 (here p is the density of the substance in g / cm 3). X-rays are attenuated by both scattering and absorption. Accordingly, the mass attenuation coefficient is the sum of the mass absorption and scattering coefficients. The mass absorption coefficient increases sharply with increasing atomic number (Z) of the absorber (proportional to Z3 or Z5) and with increasing wavelength (proportional to λ3). This dependence on the wavelength is observed within the absorption bands, at the boundaries of which the coefficient exhibits jumps.

The mass scattering coefficient increases with increasing atomic number of the substance. For λ≥0,3Å the scattering coefficient does not depend on the wavelength, for λ<0,ЗÅ он уменьшается с уменьшением λ.

The decrease in the absorption and scattering coefficients with decreasing wavelength causes an increase in the penetrating power of X-rays. The mass absorption coefficient for bones [absorption is mainly due to Ca 3 (PO 4) 2 ] is almost 70 times greater than for soft tissues, where absorption is mainly due to water. This explains why the shadow of the bones stands out so sharply on the radiographs against the background of soft tissues.

The propagation of an inhomogeneous X-ray beam through any medium, along with a decrease in intensity, is accompanied by a change in the spectral composition, a change in the quality of the radiation: the long-wave part of the spectrum is absorbed to a greater extent than the short-wave part, the radiation becomes more uniform. Filtering out the long-wavelength part of the spectrum makes it possible to improve the ratio between deep and surface doses during X-ray therapy of foci located deep in the human body (see X-ray filters). To characterize the quality of an inhomogeneous X-ray beam, the concept of "half attenuation layer (L)" is used - a layer of a substance that attenuates the radiation by half. The thickness of this layer depends on the voltage on the tube, the thickness and material of the filter. Cellophane (up to an energy of 12 keV), aluminum (20–100 keV), copper (60–300 keV), lead, and copper (>300 keV) are used to measure half attenuation layers. For X-rays generated at voltages of 80-120 kV, 1 mm of copper is equivalent in filtering capacity to 26 mm of aluminum, 1 mm of lead is equivalent to 50.9 mm of aluminum.

Absorption and scattering of X-rays is due to its corpuscular properties; X-rays interact with atoms as a stream of corpuscles (particles) - photons, each of which has a certain energy (inversely proportional to the wavelength of X-rays). The energy range of X-ray photons is 0.05-500 keV.

The absorption of X-ray radiation is due to the photoelectric effect: the absorption of a photon by the electron shell is accompanied by the ejection of an electron. The atom is excited and, returning to the ground state, emits characteristic radiation. The emitted photoelectron carries away all the energy of the photon (minus the binding energy of the electron in the atom).

Scattering of X-ray radiation is due to the electrons of the scattering medium. There are classical scattering (the wavelength of the radiation does not change, but the direction of propagation changes) and scattering with a change in wavelength - the Compton effect (the wavelength of the scattered radiation is greater than the incident one). In the latter case, the photon behaves like a moving ball, and the scattering of photons occurs, according to the figurative expression of Comnton, like a game of billiards with photons and electrons: colliding with an electron, the photon transfers part of its energy to it and scatters, having already less energy (respectively, the wavelength of the scattered radiation increases), the electron flies out of the atom with a recoil energy (these electrons are called Compton electrons, or recoil electrons). The absorption of X-ray energy occurs during the formation of secondary electrons (Compton and photoelectrons) and the transfer of energy to them. The energy of X-rays transferred to a unit mass of a substance determines the absorbed dose of X-rays. The unit of this dose 1 rad corresponds to 100 erg/g. Due to the absorbed energy in the substance of the absorber, a number of secondary processes occur, which have importance for X-ray dosimetry, since it is on them that X-ray measurement methods are based. (see Dosimetry).

All gases and many liquids, semiconductors and dielectrics, under the action of X-rays, increase electrical conductivity. Conductivity is found by the best insulating materials: paraffin, mica, rubber, amber. The change in conductivity is due to the ionization of the medium, i.e., the separation of neutral molecules into positive and negative ions (ionization is produced by secondary electrons). Ionization in air is used to determine the exposure dose of X-ray radiation (dose in air), which is measured in roentgens (see Ionizing Radiation Doses). At a dose of 1 r, the absorbed dose in air is 0.88 rad.

Under the action of X-rays, as a result of the excitation of the molecules of a substance (and during the recombination of ions), in many cases a visible glow of the substance is excited. At high intensities of X-ray radiation, a visible glow of air, paper, paraffin, etc. is observed (metals are an exception). The highest yield of visible light is given by such crystalline phosphors as Zn·CdS·Ag-phosphorus and others used for screens in fluoroscopy.

Under the action of X-rays, various chemical processes can also take place in a substance: the decomposition of silver halides (a photographic effect used in X-rays), the decomposition of water and aqueous solutions of hydrogen peroxide, a change in the properties of celluloid (clouding and release of camphor), paraffin (clouding and bleaching) .

As a result of complete conversion, all the X-ray energy absorbed by the chemically inert substance is converted into heat. The measurement of very small amounts of heat requires highly sensitive methods, but is the main method for absolute measurements of X-rays.

Secondary biological effects from exposure to x-rays are the basis of medical radiotherapy (see). X-rays, the quanta of which are 6-16 keV (effective wavelengths from 2 to 5 Å), are almost completely absorbed skin tissues of the human body; they are called boundary rays, or sometimes Bucca rays (see Bucca rays). For deep X-ray therapy, hard filtered radiation with effective energy quanta from 100 to 300 keV is used.

The biological effect of x-ray radiation should be taken into account not only in x-ray therapy, but also in x-ray diagnostics, as well as in all other cases of contact with x-rays that require the use of radiation protection (see).

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

IN vivo X-ray beams are rare and are 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 visible to the eye radiation is able to penetrate various barriers: 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 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 chemical element used to make the tube anode.

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 color. 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, archaeology, architecture, construction, restoration work - to detect defects and carry out chemical analysis 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 schools produce narrow-profile 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 of examining organs chest, 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 survey 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 is one of the methods local treatment. 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;
  • norm for annual medical examination– no 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.

Ministry of Education and Science of the Russian Federation

Federal Agency for Education

GOU VPO SUSU

Department of Physical Chemistry

at the KSE course: “X-ray radiation”

Completed:

Naumova Daria Gennadievna

Checked:

Associate Professor, K.T.N.

Tanklevskaya N.M.

Chelyabinsk 2010

Introduction

Chapter I. Discovery of X-rays

Receipt

Interaction with matter

Biological impact

Registration

Application

How an x-ray is taken

natural x-rays

Chapter II. Radiography

Application

Image Acquisition Method

Benefits of radiography

Disadvantages of radiography

Fluoroscopy

Receipt principle

Benefits of Fluoroscopy

Disadvantages of Fluoroscopy

Digital technologies in fluoroscopy

Multiline scanning method

Conclusion

List of used literature

Introduction

X-ray radiation - electromagnetic waves, the photon energy of which is determined by the energy range from ultraviolet to gamma radiation, which corresponds to the wavelength range from 10−4 to 10² Å (from 10−14 to 10−8 m).

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. So, bone tissues 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. X-ray beam passing through chemical compound, causes a characteristic secondary emission, the spectroscopic analysis of which allows the chemist to determine the composition of the compound. When falling on crystalline substance a beam of x-rays 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.

Chapter I. Discovery of X-rays

The discovery of X-rays is attributed to Wilhelm Conrad Roentgen. He was the first to publish an article on X-rays, which he called x-rays (x-ray). An article by Roentgen titled "On a new type of rays" was published on December 28, 1895 in the journal of the Würzburg Physico-Medical Society. It is considered, however, proven that X-rays have already been obtained before. The cathode ray tube that Roentgen used in his experiments was developed by J. Hittorf and W. Kruks. This tube produces X-rays. This was shown in the experiments of Crookes and from 1892 in the experiments of Heinrich Hertz and his student Philipp Lenard through the blackening of photographic plates. However, none of them realized the significance of their discovery and did not publish their results. Also, Nikola Tesla, starting in 1897, experimented with cathode ray tubes, received x-rays, but did not publish his results.

For this reason, Roentgen did not know about the discoveries made before him and discovered the rays, later named after him, independently - while observing the fluorescence that occurs during the operation of a cathode ray tube. Roentgen studied X-rays for a little over a year (from November 8, 1895 to March 1897) and published only three relatively small articles about them, but they provided such an exhaustive description of the new rays that hundreds of papers by his followers, then published over the course of 12 years, could neither add nor change anything essential. Roentgen, who had lost interest in X-rays, told his colleagues: "I already wrote everything, don't waste your time." Roentgen also contributed to the fame famous photo the hands of his wife, which he published in his article (see image on the right). Such fame brought Roentgen in 1901 the first Nobel Prize in Physics, and the Nobel Committee emphasized the practical importance of his discovery. In 1896, the name "X-rays" was first used. In some countries, the old name remains - X-rays. In Russia, the rays began to be called "X-ray" at the suggestion of a student V.K. Roentgen - Abram Fedorovich Ioffe.

Position on the scale of electromagnetic waves

The energy ranges of X-rays and gamma-rays overlap in a wide energy range. Both types of radiation are electromagnetic radiation and at the same photon energy - are equivalent. The terminological difference lies in the mode of occurrence - X-rays are emitted with the participation of electrons (either in atoms or free ones), while gamma radiation is emitted in the processes of de-excitation of atomic nuclei. X-ray photons have energies from 100 eV to 250 keV, which corresponds to radiation with a frequency of 3 1016 Hz to 6 1019 Hz and a wavelength of 0.005 - 10 nm (there is no generally accepted definition of the lower limit of the X-ray range in the wavelength scale). Soft X-rays are characterized by the lowest photon energy and radiation frequency (and the longest wavelength), while hard X-rays have the highest photon energy and radiation frequency (and the shortest wavelength).

(X-ray photograph (roentgenogram) of his wife's hand, taken by V.K. Roentgen)

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Receipt

X-rays are produced by strong acceleration of charged particles (mainly electrons) or by high-energy transitions in the electron shells of atoms or molecules. Both effects are used in X-ray tubes, in which electrons emitted by a hot cathode are accelerated (no X-rays are emitted, because the acceleration is too low) and hit the anode, where they are sharply decelerated (in this case, X-rays are emitted: the so-called . bremsstrahlung) and at the same time knock out electrons from the inner electron shells of the atoms of the metal from which the anode is made. Empty spaces in the shells are occupied by other electrons of the atom. In this case, X-ray radiation is emitted with a certain energy characteristic of the anode material (characteristic radiation, frequencies are determined by the Moseley law:

,

where Z is the atomic number of the anode element, A and B are constants for a certain value of the principal quantum number n of the electron shell). At present, anodes are made mainly of ceramics, and the part where the electrons hit is made of molybdenum. In the process of acceleration-deceleration, only 1% of the kinetic energy of the electron goes to X-rays, 99% of the energy is converted into heat.

X-rays can also be obtained in particle accelerators. so-called. Synchrotron radiation occurs when a beam of particles is deflected in a magnetic field, as a result of which they experience acceleration in a direction perpendicular to their motion. Synchrotron radiation has a continuous spectrum with upper bound. With appropriately chosen parameters (the magnitude of the magnetic field and the energy of the particles), X-rays can also be obtained in the spectrum of synchrotron radiation.

Schematic representation of an x-ray tube. X - X-rays, K - cathode, A - anode (sometimes called anticathode), C - heat sink, Uh - cathode filament voltage, Ua - accelerating voltage, Win - water cooling inlet, Wout - water cooling outlet (see x-ray tube) .

Interaction with matter

The refractive index of almost any substance for x-rays differs little from unity. A consequence of this is the fact that there is no material from which an X-ray lens can be made. In addition, when X-rays are incident perpendicular to the surface, they are almost not reflected. Despite this, in X-ray optics, methods have been found for constructing optical elements for X-rays.

X-rays can penetrate matter, and different substances absorb them differently. The absorption of x-rays is their most important property in x-ray photography. The intensity of X-rays decreases exponentially depending on the path traveled in the absorbing layer (I = I0e-kd, where d is the layer thickness, the coefficient k is proportional to Z3λ3, Z is the atomic number of the element, λ is the wavelength).

Absorption occurs as a result of photoabsorption and Compton scattering:

Photoabsorption is understood as the process of knocking out an electron from the shell of an atom by a photon, which requires that the photon energy be greater than a certain minimum value. If we consider the probability of the act of absorption depending on the energy of the photon, then when a certain energy is reached, it (probability) increases sharply to its maximum value. For higher energies, the probability continuously decreases. Because of this dependence, it is said that there is an absorption limit. The place of the electron knocked out during the act of absorption is occupied by another electron, while radiation with a lower photon energy is emitted, the so-called. fluorescence process.