Radiograph

Radiograph (synonym x-ray) - constant negative image of the investigated object obtained on a special x-ray film or photo paper with the help of x-ray radiation.
To get x-rays use one of the fundamental properties of x-ray radiation (see) is to penetrate different environments and tissues of the body and to be absorbed by them in various degrees, depending on their physical-chemical properties. Of crucial importance here is the sequence number of the elements on the periodic table)of those or other tissue, the thickness of the subject and its density and wavelength of x-ray radiation, practically defined rigidity, expressed in kilovolts.
It is established that the absorption of x-ray radiation is proportional to the fourth degree sequence number of the item (Z) and third-degree wavelength. Therefore, the atoms of calcium (Z = 20), comprising mostly bone, compared with atoms of oxygen (Z=8)that are part of the so-called soft tissues absorb x-ray radiation stronger: 204:84 =160 000 : 4096=40, i.e. approximately 40 times. It's understandable why the bone in the soft tissues give the x-ray picture is much more intense shade. On this same pattern based the use of contrast agents, such as barium (Z=56), iodine (Z=53) and others, where the natural conditions contrast insufficient or missing. As x-ray effect, in addition to the properties of the object depends on the quality (rigidity) and quantity (in milliamperemeter) x-ray radiation passing through the object of the study and who is intensifying screens and films, it is clear that the more rigidly radiation, in other words, the more its penetrating ability and the longer the exposure, i.e. the amount of radiation, the greater the process of photochemical effects on the photosensitive layer and vyrajenie will degree blackening of the film after its processing.
Main the most important evaluation criteria radiographs that determine its suitability for the purposes of radiology, are: 1) optical contrast; 2) the sharpness of the image , and 3) the lack of artifacts.

Radiograph (synonym x-ray) is obtained using x-rays for a negative image of the object in a special film or paper.
When assessing the quality of x-ray consider the sharpness and contrast. In addition, an x-ray must be free of shadows (artifacts) and adequately to present the study of the anatomical region in properly chosen projection.
Under the sharpness or clarity, x-ray understand the presence of the clearly expressed transition from one degree of blackening to another. The movement of the subject cause dynamic blur. Geometric blur depends on the sharpness of focus x-ray tube (the higher the optical size of tube focus, the higher blur), a distance of x-ray tube film (the higher the percentage, the less is not the sharpness), the distance of the object - film (the it is less, the less blur), grain light-sensitive layer of film and grain intensifying screens (the less, the less blur).
Under optimal contrast of the image there is a clearly defined shades between light and dark x-rays. In the absence of significant shadow difference between the black background around the object and image dense areas of the radiograph is assessed as low contrast. The contrast of the image depends on hardness, i.e. the energy of the radiation. The softer the radiation is, the easier it is to get good contrast x-rays, however, and in hard, i.e. more short-wave radiation, when properly selected shutter speed you can achieve good contrast images. Important as proper processing of the film (subject to applicable regime - time display, the temperature of the developer, its composition and so on). The use of diaphragms, tubes and screening of lattices in radiography reduces the number of scattered radiation that reaches the film, and thus increases the contrast x-ray.
Contrast x-rays also increase intensifying screens with the ability to emit light radiation under the influence of x-rays. The use of intensifying screens can significantly reduce exposure in x-rays, as the picture on the x-ray does not receive as much under the influence of direct absorption of x-ray film, how many (more) under the influence of light radiation screens.
Upon receipt of radiographs use one of the fundamental properties of x-rays to penetrate opaque environment and be absorbed by them in various degrees depending on physical-chemical structure and the density of the medium.
To use x-ray film of standard formats: 13X 18, 18X24, 24X30, 35x35, 15 and 30 X 40 X 40 cm For special studies (angiography) is sometimes used roll film of various sizes. In radiography in dental practice for intraoral images are films size 3X4, 4X5 and see 5X8
The sensitivity of the film according to GOST USSR (2817-50) is measured in so-called reverse the x-rays. It is inversely proportional to the amount of radiant energy roentgen (1/R)necessary for the reference (adopted conditionally) effect blackening film, i.e. the sensitivity of the film is taken into account in the return value of this number
On the box of the film medium sensitivity see figure 200-300 reverse the x-ray. Film sensitivity over 300 reverse CT scans (high sensitivity) allow to produce x-rays at a shorter exposure than the average film and the low sensitivity (less than 200 reverse CT scans).
X-ray film differs from photographic greater thickness of the light-sensitive layer, which increases the shadow image density. Film on the basis of nitrocellulose dangerous in the fire relation, acetate film on the basis of less flammable. Film with bilateral emulsion allows you to use two intensifying screens with a corresponding increase contrast and exposure reduction.
To obtain x-ray of good quality is crucial choice of rational technical conditions (focal length, anode voltage, current, exposure), as well as the correct processing. In large x-ray departments (showing no less than 200 images per shift) cost-effective use of special processing units with automated process of processing of x-rays.
X-rays are considering the negatoscopes, with dense x-ray images with large pozeranie require increased light of negatoscopes.
Need a rigorous documentation of the LMS: each radiograph should be marked with letters labeling of the investigational side (P - right, L - left), surname, name, patronymic name and age of the patient, date and serial number of the study. The best method of certification of x-rays is light labeling with special stencils, otectively the necessary data on the film emulsion.
Cm. also the Contrast of the shadow, Radiography.