Radiography

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

Purposes of radiography

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

Indications for radiography

• Objective confirmation of damage to the lungs, heart and other organs.
• Monitoring the effectiveness of treatment.
• Monitoring the correct placement of a central catheter and endotracheal tube in the intensive care unit (ICU).

Radiography is used everywhere. It can be performed in all medical institutions, it is simple and not burdensome for the patient. Images can be taken in a stationary X-ray room, ward, operating room, resuscitation department. With the right choice of technical conditions, the image displays small anatomical details. An X-ray is a document that can be stored for a long time, used for comparison with repeated X-rays and presented for discussion to an unlimited number of specialists.

Contraindications to radiography

First trimester of pregnancy (if there are absolute indications for the examination, it is necessary to protect the fetus with a lead apron).

Preparation for X-ray examination

Before the X-ray, the patient is informed about the necessity of this examination, the method of conducting it is explained (for example, when examining the chest organs, to improve the quality of the obtained images, it is necessary to take a deep breath and hold it on command). When performing X-ray of the digestive organs, food and drink intake is limited, before the examination it is necessary to check whether the patient has removed all metal jewelry, watches, etc.

Research methodology

• The patient is placed in front of the X-ray machine, seated in a chair or laid on a special table.
• If the patient is intubated, care must be taken to ensure that the tube and hoses have not become displaced during placement.
• The patient is prohibited from moving until the end of the study.
• Before the X-ray examination begins, the medical worker must leave the room or the place where the examination is being carried out; if for various reasons he cannot do this, then he must put on a lead apron.
• The images are taken in several projections depending on the goal.
• The images are developed and checked for quality before the patient leaves the X-ray room; if necessary, repeat images are taken.

Film radiography is performed either on a universal X-ray machine or on a special stand designed only for this type of examination. The body part being examined is placed between the X-ray emitter and the cassette. The inner walls of the cassette are covered with intensifying screens, between which the X-ray film is placed.

Intensifying screens contain a phosphor that glows under the influence of X-ray radiation and, thus, affects the film, enhancing its photochemical action. The main purpose of intensifying screens is to reduce exposure, and therefore the radiation exposure of the patient.

Depending on their purpose, intensifying screens are divided into standard, fine-grained (they have a small phosphor grain, reduced light output, but very high spatial resolution), which are used in osteology, and high-speed (with large phosphor grains, high light output, but reduced resolution), which are used when conducting research on children and fast-moving objects, such as the heart.

The body part being examined is placed as close as possible to the cassette to reduce projection distortion (primarily magnification) that occurs due to the divergent nature of the X-ray beam.

In addition, such a position ensures the necessary image sharpness. The emitter is installed so that the central beam passes through the center of the body part being photographed and is perpendicular to the film. In some cases, for example, when examining the temporal bone, an inclined position of the emitter is used.

Radiography can be performed with the patient in a vertical, horizontal, inclined or lateral position. Shooting in different positions allows one to judge the displacement of organs and to identify some important diagnostic signs, such as fluid spreading in the pleural cavity or the presence of fluid levels in intestinal loops.

A picture of a body part (head, pelvis, etc.) or an entire organ (lungs, stomach) is called a survey picture. Pictures with the image of the part of the organ of interest to the doctor in a projection optimal for examining a particular detail are called targeted pictures. They are often taken by the doctor himself under the control of transillumination. Pictures can be single or serial. A series can consist of 2-3 radiographs, which record different states of the organ (for example, peristalsis of the stomach). However, serial radiography is more often understood as the production of several radiographs during one study and usually in a short period of time. For example, during arteriography (contrast study of blood vessels) with the help of a special device - a seriograph - up to 6 - 8 pictures per second are taken.

Of the radiography options, it is worth mentioning shooting with direct image magnification, which is usually achieved by moving the X-ray cassette away from the object being photographed by 20-30 cm. As a result, the radiograph produces an image of small details that are not distinguishable in conventional images. This technology can only be used with special tubes in which the focal spot has very small dimensions - about 0.1-0.3 mm ². For studying the bone and joint system, magnification of 5-7 times is considered optimal.

Radiographs can produce an image of any part of the body. Some organs are clearly visible on images due to natural contrast (bones, heart, lungs). Other organs are clearly visible only after artificial contrast (bronchi, blood vessels, bile ducts, heart cavities, stomach, intestines). In any case, the radiographic picture is formed from light and dark areas. The blackening of X-ray film, like photographic film, occurs due to the restoration of metallic silver in its exposed emulsion layer. To do this, the film is subjected to chemical and physical treatment: it is developed, fixed, washed, and dried. In modern X-ray rooms, the entire film processing process is automated due to the presence of developing machines. The use of microprocessor technology, high temperature and fast-acting chemical reagents allows reducing the time for obtaining an X-ray picture to 1-1.5 minutes.

It should be remembered that an X-ray is a negative in relation to the image visible on a fluorescent screen when illuminated, therefore, areas of the body transparent to X-rays appear dark on X-rays ("darkening"), and denser areas appear light ("clearing"). However, the main feature of an X-ray is different. Each ray, when passing through the human body, crosses not one point, but a huge number of points located both on the surface and deep in the tissues. Consequently, each point on the image corresponds to a set of actual points of the object, which are projected onto each other, therefore, the X-ray image is summative, planar. This circumstance leads to the loss of the image of many elements of the object, since the image of some parts is superimposed on the shadow of others. The main rule of X-ray examination follows from this: X-rays of any part of the body (organ) must be made in at least two mutually perpendicular projections - direct and lateral. In addition to them, images in oblique and axial (axial) projections may be required.

In electron-optical digital radiography, the X-ray image obtained in the television camera is amplified and sent to an analog-to-digital converter. All electrical signals carrying information about the object being examined are converted into a series of numbers. In other words, a digital image of the object is created. The digital information is then sent to the computer, where it is processed according to pre-written programs. The doctor selects the program based on the objectives of the examination. With the help of a computer, it is possible to improve the quality of the image, increase its contrast, clear it of interference, and highlight the details or contours that interest the doctor.

In systems that use object scanning technology, a moving narrow beam of X-rays is passed through the object, i.e. all its sections are successively "illuminated". The radiation that has passed through the object is registered by a detector and converted into an electrical signal, which, after being digitized in an analog-to-digital converter, is transmitted to a computer for subsequent processing.

Digital fluorescent radiography is rapidly developing, in which a spatial X-ray image is perceived by a "memory" fluorescent plate, capable of preserving the image hidden in it for several minutes. This plate is then scanned by a special laser device, and the resulting light flux is converted into a digital signal.

Direct digital radiography, based on the direct transformation of the energy of X-ray photons into free electrons, is particularly attractive. Such a transformation occurs when an X-ray beam, having passed through an object, acts on plates of amorphous selenium or amorphous semicrystalline silicone. For a number of reasons, this method of radiography is currently used only for chest examination.

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

The advantages of digital radiography include high image quality, reduced radiation exposure, and the ability to store images on magnetic media with all the ensuing consequences: ease of storage, the ability to create organized archives with prompt access to data, and the ability to transmit images over distances - both within the hospital and beyond.

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 clavicles, the location of the lung roots and their contrast, the distinguishability of the main and small bronchi, the transparency of the lung tissue, the presence of darkening, its size, shape. All characteristics must correspond to the patient's age. When X-raying the skull, the following is revealed:

• skull fractures;
• pronounced intracranial hypertension with an increase in the size of the brain and the appearance of characteristic digital impressions on the inner plate of the skull;
• pathology of the "Turkish saddle" caused by increased intracranial pressure;
• calcified tumors of the brain (or the presence of intracranial space-occupying lesions is judged by the displacement of the calcified pineal body relative to the middle cavity of the skull).

To make a diagnosis, it is necessary to analyze and compare the data from the X-ray examination with the results of the physical examination and functional tests.

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