3.9 X-ray method of diagnosis of tuberculosis


At diagnostics of lung tuberculosis most frequently are applied the following X-ray methods:

  1. rontgenoscopy;
  2. rontgenography (radiography);
  3. tomography;
  4. Fluorography.

Rontgenoscopy – (x-raying, radioscopy) is the cheapest method of x-ray examination used for diagnostics. At radioscopy the image of an organ is examined on the screen at the moment of x-raying. The defect of this method that it does not give the objective documentation of examination, badly reveals fine pathological formations, particular in focuses by the size in 2-3 mm and fine linear components. At lung tuberculosis rontgenoscopy is applied to preliminary, orienting examination. This method is useful for revealing of exudations in pleural cavity, pathological formations hidden on radiograph behind the shadow of mediastinum and diaphragm, vertebra, and also for specification of the process localization.

Rontgenography (radiography, radiographic imaging). This method displays details of pathological process more full. Standard radiograph is a projection of “shadows” of human organ to X-ray film. At passage through chest the X-ray beam is non-uniform is weakened proportionally density of organs and tissues. This changed beam gets on a film containing brome silver, and film changes its property. The picture of restoration of film is seen after display and fixings. At those places where the exposition of X-rays on the film was stronger the more silver was restored, so this places of the film are becoming darker. At those places where the beams penetrate through dense formation – bones, calcifications etc. – is less silver is restored and in this places the film is more transparent. This is mechanism of negative formation; the places treated by X-rays more intensively become DARKER. Therefore tumor, infiltrations, bones – are almost transparent on a film, and empty chest cavity at spontaneous pneumothorax – almost black. The rigidity of x-ray film is estimated on a shadow of the vertebra. On the soft X-ray irradiation of the chest vertebra portion is presented as a continuous shadow. On the intensive irradiation every vertebra is seen well. On optimum X-ray irradiation the first 3-4 chest vertebra are visible. Other shadows of chest cavity in anterior-posterior projection have no decisive importance at an estimation of irradiation intensity. Series of radiographs, made during all time of disease, allow to carry out dynamic supervision of of the process course in lungs. Radiography – is basic X-ray method used now for diagnostics of lung tuberculosis. It is accepted to make direct (anterior-posterior) and left or right profile radiograph depending on prospective localization of the lesion.

Tomography (body section radiography) is obtaining by level-by-level snapshots through special devices to the x-ray installation. Radio-tomography of the chest cavity enables to get X-ray films without summation effect. “Spreading” of interfered tissues is reached by movement X-ray tube and cartridge in opposite directions. Tomography Is applied to specify the character of process, its topography and study of details in the defeat focus, such as deep disintegration, to reveal borders and volume of a defeat more precisely.

Fluorography – is photographing of the x-ray image from fluorescent screen. Fluorograms could be with size of 34X34 mm, 70X70 mm and 100×100 mm and electronic. The electronic fluorograms are made with the help of special fluorography installations, equipped with computer. Basically, fluorography is applied for mass preventive X-ray examinations of the population, with the purpose of revealing of latent forms of lung diseases, first of all lung tuberculosis and tumors.

X-ray appearances of lung tuberculosis.

On radiograph tubercular lesions of lung parenxyma, stroma comes to light as shadows (densities, consolidations). At the description of these shadows it is necessary to take into account their:

  1. Quantity;
  2. Size;
  3. Form;
  4. Contours;
  5. Intensity;
  6. Structure;
  7. Localization

The quantity of a shadow can be single or multiple, its size – fine, average, large, its form – rounded, oval, polygonal, linear, and irregular. The contours of shadows can be precise and indistinct. The intensity of shadows – weak, average, high; structure – homogeneous or no homogeneous.

The changes of lung pattern are to be:

  • rod and
  • Net character.

The rods have appearance as linear shadows going in parallel or of a “fanlike” ar-rangement of the lung markings. Net like lung shadows defined by bound linear shadows. These shadows can be of various widths, from 1-2 up to 5-6 mm. Quite often they merge in wide strips; it is especially in lungs roots areas. Their contours are precise or dim. Intensity average or high. At a net like arrangement of shadows the fine or large loops are formed.

Rod-like and net-like reflections in the lung picture of inflammation processes, the scar and the fibrous lesions in lymph vessels or in interlobular connective tissue. Usually for inflammation process (lymphangitis) large width, illegibility of contours and average intensity of linear shadows are characteristic. For fibrotic and the scars shadows the small width, clearness of contours, high intensity is characteristic. But it is not obligatory attributes. That is why quite often to distinguish fresh changes in a connective lung tissue from old, scarring, it is possible only at dynamic supervision, at repeated radiograph examinations. The fresh changes decrease or increase depending on the course of process (recovering or progressing), but old ones remain stable.

Focus shadows are the most often display of lung tuberculosis. They are defined as densities by size from 2-3 mm up to 1, 5 cm in a diameter. They can be individual, but more often meet multiple. According to their sizes the focuses are divided into three groups: fine – 2-4 mm, average size – up to 5-9 mm and large – up to 1-1.2 cm. The form of the foci – round, polygonal, irregular and wrong. Contours – precise or dim. Linear shadows are visible, rod-like, departing from a contour of the focus into surrounding lung parenchyma. The intensity of the foci could be weak, when it corresponds to intensity of a longitudinal shadow of a vessel, average, appropriate to intensity cross shadow of a vessel, high intensity appropriate to intensity of a rib, mediastinum.

The structure of the foci can be homogeneous and non-uniform. The non-uniform structure is observed usually at their irregular condensation and calcification, and also at presence of disintegration. At non-uniform condensation and calcifications of the focuses the intensity of its shadow will be various in different parts; the intensity of an average degree settles down in closely to the site of the large intensity. The disintegration is defined as enlightenment with a precise contour inside of the focus shadow.

The infiltrations (infiltrative focuses) are shadows with the size more than 1, 5 см in a diameter. Infiltrative focuses, according to their sizes are divided into: fine – 2 cm, medium – up to 3 cm and large 4 cm and more. The large infiltrations are usually formed at merge of the focuses or fine and medium infiltrations. The single infiltration is met more often. The form of infiltrations could be round, oval, and irregular. Large infiltrations usually occupy segments or lobe and repeat the form of the lung subunit. Their contour more often precise, intensity is medium or high, structure more often is non-uniform.

Tuberculous cavities may be classified under three types: the acute cavities (forming), the rounded (fresh) cavities and the old cavities.
X-ray diagnosis of all kinds of cavities is based on detection of two attributes:

  • Presence inside the shadow closed ring-like shadow of the various form and size;
  • This internal contour of a cavity never repeats of its outside contour.

The acute (forming) cavity is defined by enlighten (in the center of focus or of infiltration) with distinct, irregular inlet contour which develops rapidly in the center (or eccentrically) of an area of caseation.

The rounded (fresh) cavity is defined by a smooth thin fibrous wall, which develops more slowly within a small area of tuberculous infiltration. The width of the cavity wall is various, usually 5-10 mm. The fresh cavities could be with rounded, smooth, thin-walled “stamp-like cavities”, may develop as a result of check valve action of granulations at the bronchial communication. If the fresh cavity arises among old tubercular changes (scars, fibrotic focuses), its form can be extended and even irregular. Characteristic sign of fresh cavities is the presence of two wide pair strips, going from its bottom poles to the lung root. This is the condensed wall caused by inflammation of draining bronchus.

The old cavity is defined as ring-like shadow oval or irregular form, with precise internal and outside contours. Its wall width is usually reached several millimeters, with high intensity. The multiple linear and rod-like densities of fibrosis are defined around of a shadow of the cavity. Frequently the walls of draining bronchus are visible, but these shadows are thinner and more intensive, than in fresh cavity.

The described attributes of different kinds of cavities are relative. They meet in significant percent of cases, but not necessarily all. Frequently the possibility to make a final conclusion about freshness or chronicity of a cavity can be done only after dynamic supervision. Statistically more frequently the lesions of secondary lung tuberculosis meet in I, II, VI and sometimes – X segment. Upper and dorsal departments, subclavicular area are the favourite locations of fresh tubercular lesions. In supraclavicular areas and upper parts of lungs old specific tubercular densities are frequently determined.

The artifacts or defects on radiographs are named shadows or enlightenments caused by technical errors and which have been not connected to shadows of body tissues. The linear white strips can be simply scratches, round transparent stain or smudges – consequence of hit on the not shown film of a fixative substance. The branch-like or, similar to figure of lightning black shadows arise at the electrostatic discharge at one about another films friction.

Technique of the description of the x-ray lung shadows.
It is convenient to use the consecutive order of the characteristics and their description at the description of x-ray shadows in lungs.

  1. Localization of process. Specify: distribution on lobes and segments.
  2. Number, quantity of shadows. Specify: individual or multiple.
  3. Form. Specify: rounded, oval, polygonal, linear and irregular.
  4. The size of a shadow. Specify: fine, average, and large.
  5. The intensity. Specify: weak, average and high.
  6. The picture (spotty and linear), structure of a shadow (homogeneous or non-homogenous).
  7. The contours. Specify: precise and indistinct (dim).
  8. Displaysness. Specify: a position deviation of lung structures from a normal arrangement.
  9. Condition of surrounding lung tissue.

Radiographic classification of tubercular lesions in lungs.

In order to come to some common ground of clinical understanding the following classification used mostly in English literature to denote the extent and degree of pulmonary involvement. From the radiograph standpoint the essential features of this classification are as follows:
Extent of Pulmonary Lesions.
1. Minimal.
Slight lesions without demonstrable excavation confined to a small part of one or both lungs. The total extent of the lesions, regardless of distribution, shall not exceed the equivalent of the volume of lung tissue which lies above the second chondrosternal junction and the spine of the fourth or body of the fifth thoracic vertebra on one side.
2. Moderately advanced.
One or both lungs may be involved, but the total extent of the lesions shall not exceed the following limits:
2.1. Slight disseminated lesions which may extend through not more than the volume of one lung, or the equivalent of this in both lungs.
2.2. Dense and confluent lesions that may extend through not more than the equivalent of one-third the volume of one lung.
2.3. Any gradation within the above limits.
2.4. Total diameter of cavities, if present, estimated not to exceed 4 cm.
3. Far Advanced.
Lesions more extensive than moderately advanced.

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