Radiography

Radiography (X-ray imaging) is an X-ray examination method in which a fixed X-ray image of an object is obtained on a solid carrier, in the overwhelming majority of cases on an X-ray film. In digital X-ray machines, this image can be fixed on paper, in magnetic or magnetic-optical memory, obtained on the display screen.

Objectives of X-rays

X-ray examination is used to diagnose specific lesions in infectious diseases (pneumonia, myocarditis, arthritis) and their complications, detection of diseases of the chest (lungs and heart); for individual indications, the skull, spine, joints, liver, digestive organs and kidneys are examined.

Indications for radiography

• Objective confirmation of lesions of the lungs, heart and other organs.
• Control of the effectiveness of treatment.
• Control of the correct installation of the central catheter and endotracheal tube in the intensive care unit (ICU).

Radiography is used everywhere. It can be performed in all medical institutions, simple and easy for the patient. Pictures can be taken in a stationary X-ray room, ward, operating room, resuscitation department. With the right selection of specifications, small anatomical details are displayed in the image. A radiograph is a document that can be stored for a long time, used for comparison with repeated radiographs, and present an unlimited number of specialists for discussion.

Contraindications to radiography

I trimester of pregnancy (with absolute indications for the study, it is necessary to protect the fetus with a lead apron).

Preparing for X-ray examination

Before the radiography, the patient is informed of the need for this study, explains the procedure (for example, when examining the thoracic organs to improve the quality of the images obtained, it is necessary to take a deep breath and hold your breath at the command). When carrying out the radiography of the digestive organs, they limit the intake of food and drink, it is necessary to check before the examination whether the patient took off all the metal ornaments, watches,

Methodology of research

• The patient is placed in front of an X-ray machine, placed in an armchair or laid on a special table.
• If the patient is intubated, it must be ensured that the tube and hoses are not displaced during the installation process.
• The patient is forbidden to move until the end of the study.
• Before starting radiography, the medical worker should leave the premises or the location of the study, if for various reasons he can not do it, then a lead apron must be put on.
• Snapshots are performed in several projections depending on the goal.
• Photographs show and check their quality before the patient leaves the radiology room; if necessary, take a second shot.

Film radiography is performed either on a universal X-ray machine or on a special tripod designed only for this type of study. The investigated part of the body is located between the X-ray emitter and the cassette. The inner walls of the cassette are covered with reinforcing shields, between which the X-ray film is placed.

The amplifying screens contain a phosphor, which, when exposed to X-rays, glows and, thus, acts on the film, enhances its photochemical action. The main purpose of the amplifying screens is to reduce the exposure, and hence the radiation exposure of the patient.

Depending on the purpose, the reinforcing shields are divided into standard, fine-grained (they have a fine phosphor grain, reduced luminous efficiency, but very high spatial resolution), which are used in osteology, and high-speed (with large phosphor grains, high luminous efficiency but reduced resolution) that are used in the study in children and fast moving objects, such as the heart.

The investigated part of the body is placed as close as possible to the cassette in order to reduce the projection distortion (mainly the increase), which arises from the divergent nature of the X-ray beam.

In addition, this arrangement provides the necessary image sharpness. The emitter is installed so that the central beam passes through the center of the part to be removed and is perpendicular to the film. In some cases, for example, in the study of the temporal bone, the inclined position of the radiator is used.

Radiography can be performed in the vertical, horizontal or oblique position of the patient, as well as in the position on the side. Shooting in different positions allows you to judge the displacement of organs and identify some important diagnostic signs, for example, flow of fluid in the pleural cavity or the presence of fluid levels in the loops of the intestine.

A snapshot of a part of the body (head, pelvis, etc.) or a whole organ (lungs, stomach) is called an overview. Pictures with an image of the part of the organ of interest to the physician in the projection, optimal for the study of a particular part, are called sighting. They are often produced by the doctor himself under the control of translucence. Pictures can be single or serial. The series can consist of 2-3 radiographs, on which various conditions of the organ are fixed (for example, the peristalsis of the stomach). However, more commonly, serial radiography is understood as the production of several X-rays during one study and usually in a short period of time. For example, with arteriography (contrast study of blood vessels) using a special device - a seriograph - produce up to 6 to 8 shots per second.

Of the radiographic options, mention should be made of the direct-magnification imaging, which is usually achieved by moving the X-ray cassette from the subject to a distance of 20-30 cm. As a result, an X-ray shows an image of small details that can not be seen in ordinary photographs. This technology can be used only in the presence of special tubes in which the focal spot has very small dimensions - on the order of 0.1-0.3 mm ². To study the osteoarticular system, an optimal increase is 5-7 times.

On radiographs you can get an image of any part of the body. Some organs are clearly distinguishable in pictures due to natural contrast (bones, heart, lungs). Other organs are fairly clearly displayed only after their artificial contrasting (bronchi, vessels, bile ducts, cavities of the heart, stomach, intestines). In any case, the x-ray picture is formed from light and dark areas. The blackening of the X-ray film, like that of the film, is due to the reduction of metallic silver in its exposed emulsion layer. For this purpose, the film is subjected to chemical and physical treatment: it is developed, fixed, washed, and dried. In modern X-ray rooms, the whole process of film processing is automated due to the presence of developing machines. The use of microprocessor technology, high temperature and fast chemical reagents makes it possible to reduce the time of obtaining an X-ray image to 1-1.5 minutes.

It should be remembered that the X-ray image is negative with respect to the image visible on the fluorescent screen during X-ray transmission, so that the X-ray transparent parts of the body on the X-ray patterns turn out to be dark ("darkening"), and denser - light ("enlightenment"). However, the main feature of the roentgenogram lies in another. Each ray, when passing through the human body, crosses one point, but a huge number of points located both on the surface and in the depths of the tissues. Consequently, each point in the image corresponds to a set of actual points of the object, which are projected on each other, so the x-ray image is a summation, plane image. This circumstance results in the loss of the image of many elements of the object, since the image of some parts is superimposed on the shadow of the others. From this follows the basic rule of x-ray research: the radiographs of any part of the body (organ) must be produced in at least two mutually perpendicular projections - the direct and lateral. In addition to them, you may need to take pictures in oblique and axial (axial) projections.

With electron-optical digital radiography, the X-ray image obtained in a television camera, after amplification, is fed to an analog-to-digital converter. All electrical signals carrying information about the object under investigation turn into a series of numbers. In other words, a digital image of the object is created. Digital information is then fed to the computer, where it is processed according to pre-compiled programs. The program is chosen by the doctor, based on the research tasks. Using a computer, you can improve the image quality, increase its contrast, clear interference, highlight details of the doctor or contours of interest.

In systems in which the technique of scanning an object is used, a moving narrow beam of X-rays is passed through it, i. E. Consistently "shine through" all of its departments. The radiation passing through the object is detected by the detector and converted into an electrical signal, which after digitization in the analog-to-digital converter is transferred to the computer for further processing.

Rapidly developing digital luminescent radiography, in which the spatial X-ray image is perceived as a "memory" luminescent plate, capable of retaining a hidden image in it for several minutes. Then this plate is scanned by a special laser device, and the resulting light flux is converted into a digital signal.

Particularly attracting attention is direct digital radiography, based on the direct conversion of the energy of X-ray photons into free electrons. Such a transformation occurs when an X-ray beam that has passed through the object is applied to plates of amorphous selenium or an amorphous semicrystalline silicone. For a number of reasons, this method of radiography is still used only for the study of the chest.

Regardless of the type of digital radiography, the final image is stored on various magnetic media (floppy disks, hard disks, magnetic tapes) either as a hard copy (reproduced using a multi-format camera on a special film) or using a laser printer on writing paper.

The advantages of digital radiography include high image quality, reduced beam load and the ability to store images on magnetic media with all the ensuing consequences: storage convenience, the ability to create ordered archives with online access to data and image transmission over distances - both inside the hospital and beyond its limits.

Interpretation of X-ray results

When describing chest images, the doctor evaluates the location of the internal organs (displacement of the trachea, mediastinum and heart), the integrity of the ribs and collarbones, the location of the lung roots and their contrast, the distinguishability of the major and minor bronchi, the transparency of the lung tissue, the presence of blackout, its size, shape. All characteristics should correspond to the age of the patient. At a radiography of a skull reveal:

• fractures of the skull bones;
• marked intracranial hypertension with an increase in the size of the brain and the appearance of characteristic finger impressions on the inner plate of the skull;
• pathology of the "Turkish saddle", caused by increased intracranial pressure;
• calcified brain tumors (or they judge the presence of intracranial volumetric formations by displacement of the calcified pineal body relative to the middle cranial cavity).

For the diagnosis to be made it is necessary to analyze and compare the radiographic examination data with the results of the physical examination and functional tests.

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