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Radiography

X-ray is one of the main methods of X-ray examination, consisting in obtaining on the photosensitive layer a permanent negative image of the object under study. On the one hand, radiography is, along with fluoroscopy (see), the main method of X-ray examination and belongs to the competence of the radiologist, that is, it is a method of purely medical research that helps to establish the diagnosis. On the other hand, radiography is a technical process for obtaining an x-ray and is within the competence of the person carrying out this process.

The radiography technique, along with the radiologist, should also be owned by his assistant, the radiographer . With a properly organized process of radiography, the radiologist serves as a manager and consultant. The main work on X-ray is performed by a X-ray examiner, who should be well aware of the placement and installation of patients for radiography of all areas of the body. Only fluent in the technique of obtaining radiographs, you can choose the right exposure and other technical conditions, then ensure the correct photo processing and design of the radiograph (see), making it quite suitable for the purposes of x-ray.

The most important criterion for assessing the degree of qualification of a radiographer is his ability to standardize the X-ray process so as to ensure identical radiographs for repeated X-rays of the same objects of study, as well as standard comparable radiographs of paired anatomical structures of the right and left half of the body. The latter is necessary because in some cases only the radiographically identical and, moreover, projection-correct image of the same parts of the skeleton of the right and left side of the body can serve as the basis for establishing unilateral pathological changes.

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As for obtaining technically identical radiographs with repeated shots in the process of dynamic observation of the course of pathological processes, this requirement is primarily due to the fact that a series of radiographs produced over a long period of time allows us to objectively judge the course of a number of chronic diseases such as pneumosclerosis , pulmonary emphysema, pulmonary tuberculosis , peptic ulcer and duodenal ulcer, rickets , tuberculosis and other chronic bone lesions. This feature of serial radiography can be used not only for the purposes of X-ray diagnostics in the narrow sense of the word, but also as a method of monitoring the effectiveness of treatment.


Fig. 1. Auxiliary devices for patient placement during radiography.

Standardization of the X-ray process in order to obtain technically homogeneous high-quality X-ray photographs is achieved: 1) standardization of the patient’s utensils and installations during x-rays (see X-ray, basic styling and installations with x-rays ); 2) the correct choice of X-ray conditions for images, especially repeated ones; 3) standardization of the process of photographic processing of radiographs. In order to standardize the settings and installations of patients with X-ray, the supports of modern X-ray machines are equipped with appropriate linear measuring scales, protractors and centralizers, as well as devices for fixing patients during X-ray. Along with this, it is advisable to have a set of sandbags with different dimensions and weight, semi-rigid loofah or cotton wool pilots, as well as ancillary devices in the form of a set consisting of squares, benches and plates (Fig. 1), providing more convenient laying of patients and tight fit of the investigated parts of the body to the plane of the cassette. Radiography of children of preschool age and seriously ill patients should not use rigid fixation devices. In these cases, it is preferable to use the support of service personnel in compliance with safety regulations and measures of radioprotection . To reduce the effect of voluntary and involuntary movements of the examined and attendants, fixing patients, on image quality (blurred images), X-ray equipment should be adapted to the forced position of patients and apply the shortest possible exposures.

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Although radiation exposure in images is significantly less than during translucence, it is necessary for radiography of adults and especially children to carefully observe the radiation protection measures through the use of tubes, aluminum filters that absorb the soft part of the radiation, lead diaphragms that limit the radiation field , and maximize the use of protective equipment from diffuse radiation . X-rays ( lead , leaded rubber). Particular attention should be paid to the protection of the gonadal region (gonads).

The correct choice of technical conditions for radiography is greatly facilitated by the fact that modern x-ray machines (see) are supplied with instructions containing detailed tables of exposures for all parts of the body, calculated on a person of average weight, height and build. However, in practical work it is often, for various reasons, it becomes necessary to change certain shooting conditions. In this regard, the radiographic student should know the basic patterns that influence the formation of the technical parameters of X-ray diffraction under various X-ray conditions.

X-ray is one of the main methods of X-ray examination, in which an image of the object under study is obtained using X-rays on a photosensitive film after its photographic processing.

Distinguish between conventional and special radiography. Special radiography includes: tomography (see), targeted, in particular tangential images, the so-called contact radiography, telerogenography, hard or superexposed images, polygraphy, X-ray cinematography, X-ray chemography (see), dry x-ray - xerography.

Conventional radiography is produced in two standard projections (see. Radiodiagnosis). Radiography only in these two projections (Fig. 1) provides a general spatial view of the object, but does not sufficiently reflect individual details of the state of all organs and surfaces of the object (Fig. 2).


Fig. 1. Schemes of chest radiographs in standard projections: 1 - straight; 2 - side.


Fig. 2. Radiography in two projections (displays the state of the surface of the object only in the zones of passage of the beam of rays on a tangent).

For a more detailed study of any area of ​​the object under study, special targeted (targeted) images are sometimes produced. To do this, the area of ​​interest of the object under study is installed with a preliminary translucency (see Roentgenoscopy) in the center of the screen and then take pictures on a film of small size. The value of these images is that with a decrease in the irradiated field, the resolution of the radiograph improves. If, during the production of a targeted image, the central beam of X-rays is directed tangentially to the object area to be examined on the contour, then targeted tangential images are obtained (Figs. 3 and 4).

Fig. 3. The tangential projection of the metal mark (coin), which is located in the form of a strip slightly above the barely visible fracture of the sixth rib.

Fig. 4. Scheme of targeted x-ray: a dotted line indicates the location of the destroyed edge of the alveolar process in a cancer (edge ​​defect).

In those cases when it is necessary to obtain a particularly clear image of the details of the object adjacent to the film, and to eliminate the image of tissues that interfere with the detection of the test organ, a so-called contact X-ray is performed by maximally approaching (before direct contact) the X-ray tube to the surface of the object being examined.

In order to eliminate the projection magnification of the object under study and to obtain a full-size image on the radiograph of its image, teleroentgenography is used, at which the distance between the focus and the object is reduced to 2 m.

To identify more details on radiographs, hard images are produced, increasing the voltage on the tube to 120-125 sq. M.

In the study of the motor function of some organs, polygraphy is used, where, in a short period of time, several images are taken on a single film (usually 3), as well as X-ray chemotherapy.

The method of dry X-ray diffraction (xerography) is a fundamentally new, photo-processing that does not require X-ray diffraction, in which an image is obtained on special plates coated with a metal powder that is sensitive to the effects of X-rays.

In radiography, the amount of x-ray radiation used is of great importance, which is equal to the product of the strength of the secondary current by the exposure time and is measured in milliampere-seconds. Successful radiography depends on the correct choice of exposure, determined by the nature of the object under study (structure, thickness and density of its tissues), voltage on the X-ray tube, focal length, as well as the quality of the intensifying screens and X-ray films, the temperature and activity of the developer and on time manifestations.

Radiography is a research method, not indifferent to the patient. Therefore, when conducting radiography, it is necessary to strive for the maximum reduction of the radiation load on the patient.

The amount of x-ray radiation falling on the photosensitive film layer is directly proportional to the exposure time and inversely proportional to the square of the focus-object distance.

The radiation load on the patient decreases with increasing voltage on the tube and a corresponding decrease in exposure. Increasing the voltage by 10 kV allows for a decrease in the exposure of approximately two times.

The use of reinforcing (fluorescent) screens allows you to reduce the exposure time by 10-20 times, which is especially necessary in the study of moving objects (lungs, heart, stomach, esophagus, duodenum). However, the use of reinforcing screens somewhat reduces the sharpness (clarity) of the X-ray image. Therefore, to obtain structural images of small objects (nasal bones, teeth, phalanges of the fingers), X-rays are taken without reinforcing screens.

Errors in the choice of technical conditions for radiography cause poor quality radiographs. Therefore, it is necessary to keep a strict record of the shooting conditions, focusing on those for which radiograms of good quality can be obtained. In an effort to improve the quality of radiographs during repeated radiography, one should not simultaneously change all the technical conditions of radiography. When overexposure or underexposure, it is necessary to achieve an improvement in the results of X-ray diffraction, primarily by a corresponding change in the exposure time.

In photo lab processing of radiographs, it is necessary to strictly adhere to the conditions recommended by the factory producing photographic materials.

The normal development time at an optimum temperature of 18–20 ° is 5–6 min. Each degree of deviation from this temperature requires a lengthening (or reduction) of the period of manifestation by 0.5 min. The activity of the developer and its quantity gradually decreases as it is used.

To maintain the stability of the developer, use a refreshing solution, which is added to the developer as it diminishes.

X-ray diffraction in standard projections is usually performed by a radiographer. However, to achieve maximum diagnostic results, all types of radiography should be performed under the guidance and with the direct participation of the radiologist.