X-ray radiation. What is x-ray radiation, its properties and application

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.

X-ray radiation, from the point of view of physics, 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 inner 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 radiation 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.

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.

Although scientists have only discovered the effect of X-rays since the 1890s, the use of X-rays in medicine for this natural force passed quickly. Today, for the benefit of mankind, X-ray electromagnetic radiation is used in medicine, academia and industry, as well as for the generation of electricity.

In addition, radiation has useful applications in areas such as agriculture, archeology, space, law enforcement, geology (including mining) and many other activities, even cars are being developed using the phenomenon of nuclear fission.

Medical uses of x-rays

In healthcare settings, physicians and dentists use a variety of nuclear materials and procedures to diagnose, monitor, and treat a wide range of metabolic processes and diseases in the human body. As a result, medical procedures using rays have saved thousands of lives by identifying and treating conditions ranging from overactive thyroid to bone cancer.

The most common of these medical procedures involve the use of rays that can pass through our skin. When an image is taken, our bones and other structures seem to cast shadows because they are denser than our skin, and these shadows can be detected on film or on a monitor screen. The effect is similar to placing a pencil between a piece of paper and a light. The shadow from the pencil will be visible on the sheet of paper. The difference is that the rays are invisible, so a recording element is needed, something like photographic film. This allows doctors and dentists to evaluate the application of X-rays by seeing broken bones or dental problems.

The use of X-rays for medicinal purposes

The use of X-ray radiation in a targeted manner for medical purposes, not only to detect damage. When used specifically, it is intended to kill cancerous tissue, reduce the size of a tumor, or relieve pain. For example, radioactive iodine (specifically iodine-131) is often used to treat thyroid cancer, a condition that many people suffer from.

Devices that use this property are also connected to computers and scan, called: computed axial tomography or computed tomography.

These instruments provide doctors with a color image that shows outlines and details of internal organs. This helps physicians detect and identify tumors, abnormal size, or other physiological or functional organ problems.
In addition, hospitals and radiological centers perform millions of procedures annually. In such procedures, doctors fire slightly radioactive substances into the body of patients to look at certain internal organs, such as the pancreas, kidneys, thyroid, liver, or brain, to diagnose clinical conditions.

In 1895, the German physicist W. Roentgen discovered a new, previously unknown type of electromagnetic radiation, which was named X-ray in honor of its discoverer. W. Roentgen became the author of his discovery at the age of 50, holding the post of rector of the University of Würzburg and having a reputation as one of the best experimenters of his time. One of the first to find a technical application for Roentgen's discovery was the American Edison. He created a handy demonstration apparatus and already in May 1896 organized an X-ray exhibition in New York, where visitors could look at their own hand on a luminous screen. After Edison's assistant died from the severe burns he received from constant demonstrations, the inventor stopped further experiments with X-rays.

X-ray radiation began to be used in medicine due to its high penetrating power. Initially, X-rays were used to examine bone fractures and locate foreign bodies in the human body. Currently, there are several methods based on X-rays. But these methods have their drawbacks: radiation can cause deep damage to the skin. Appearing ulcers often turned into cancer. In many cases, fingers or hands had to be amputated. Fluoroscopy(synonymous with translucence) is one of the main methods of X-ray examination, which consists in obtaining a planar positive image of the object under study on a translucent (fluorescent) screen. During fluoroscopy, the subject is between a translucent screen and an x-ray tube. On modern X-ray translucent screens, the image appears at the moment the X-ray tube is turned on and disappears immediately after it is turned off. Fluoroscopy makes it possible to study the function of the organ - heart pulsation, respiratory movements of the ribs, lungs, diaphragm, peristalsis of the digestive tract, etc. Fluoroscopy is used in the treatment of diseases of the stomach, gastrointestinal tract, duodenum, diseases of the liver, gallbladder and biliary tract. At the same time, the medical probe and manipulators are inserted without tissue damage, and the actions during the operation are controlled by fluoroscopy and are visible on the monitor.
Radiography - method of X-ray diagnostics with the registration of a fixed image on a photosensitive material - special. photographic film (X-ray film) or photographic paper with subsequent photo processing; With digital radiography, the image is fixed in the computer's memory. It is performed on X-ray diagnostic devices - stationary, installed in specially equipped X-ray rooms, or mobile and portable - at the patient's bedside or in the operating room. On radiographs, the elements of the structures of various organs are displayed much more clearly than on a fluorescent screen. Radiography is performed in order to detect and prevent various diseases, its main goal is to help doctors of various specialties correctly and quickly make a diagnosis. An x-ray image captures the state of an organ or tissue only at the time of exposure. However, a single radiograph captures only anatomical changes at a certain moment, it gives the statics of the process; through a series of radiographs taken at certain intervals, it is possible to study the dynamics of the process, that is, functional changes. Tomography. The word tomography can be translated from Greek as slice image. This means that the purpose of tomography is to obtain a layered image of the internal structure of the object of study. Computed tomography 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.
Fluorography- a diagnostic method that allows you to get an image of organs and tissues, was developed at the end of the 20th century, a year after X-rays were discovered. In the pictures you can see sclerosis, fibrosis, foreign objects, neoplasms, inflammations that have a developed degree, the presence of gases and infiltrate in the cavities, abscesses, cysts, and so on. Most often, a chest x-ray is performed, which allows to detect tuberculosis, a malignant tumor in the lungs or chest, and other pathologies.
X-ray therapy- This is a modern method with which the treatment of certain pathologies of the joints is performed. The main directions of treatment of orthopedic diseases by this method are: Chronic. Inflammatory processes of the joints (arthritis, polyarthritis); Degenerative (osteoarthritis, osteochondrosis, deforming spondylosis). The purpose of radiotherapy is the inhibition of the vital activity of cells of pathologically altered tissues or their complete destruction. In non-tumor diseases, X-ray therapy is aimed at suppressing the inflammatory reaction, inhibiting proliferative processes, reducing pain sensitivity and secretory activity of the glands. It should be borne in mind that the sex glands, hematopoietic organs, leukocytes, and malignant tumor cells are most sensitive to X-rays. The radiation dose in each case is determined individually.

For the discovery of X-rays, Roentgen was awarded the first Nobel Prize in Physics in 1901, and the Nobel Committee emphasized the practical importance of his discovery.
Thus, X-rays are invisible electromagnetic radiation with a wavelength of 105 - 102 nm. X-rays can penetrate some materials that are opaque to visible light. They are emitted during the deceleration of fast electrons in matter (continuous spectrum) and during transitions of electrons from the outer electron shells of the atom to the inner ones (linear spectrum). Sources of X-ray radiation are: X-ray tube, some radioactive isotopes, accelerators and accumulators of electrons (synchrotron radiation). Receivers - film, luminescent screens, nuclear radiation detectors. X-rays are used in X-ray diffraction analysis, medicine, flaw detection, X-ray spectral analysis, etc.