X-ray examination of lung function

The functional system of breathing consists of many links, among which the systems of pulmonary (external) respiration and blood circulation are of particular importance. Efforts of respiratory muscles cause changes in the volume of the chest and lungs, which ensure their ventilation. Inhaled air due to this spreads through the bronchial tree, reaching the alveoli. Naturally, violations of bronchial patency lead to a breakdown in the mechanism of external respiration. In the alveoli, diffusion of gases through the alveolar-capillary membrane occurs. The process of diffusion is disturbed both in the defeat of the walls of the alveoli, and in the violation of capillary blood flow in the lungs.

According to the usual radiographs made in the phases of inspiration and expiration, and with fluoroscopy, an approximate idea of the mechanics of the respiratory act and ventilation of the lungs can be made. When inhaling, the front ends and the body of the ribs rise, the intercostal spaces widen, the diaphragm descends (especially due to its muscular posterior stingray). Pulmonary fields increase, and their transparency increases. If necessary, all these indicators can be measured. More accurate data are obtained with CT. It allows you to determine the size of the chest cavity at any level, the ventilation function of the lungs in general and in any of their departments. On computer tomograms, it is possible to measure the absorption of X-rays at all levels (to produce densitometry) and thereby obtain a summary of ventilation and blood filling of the lungs.

Disorders of bronchial patency due to changes in their tone, sputum accumulation, mucosal edema, organic constrictions are clearly reflected in radiographs and computer tomograms. There are three degrees of violation of bronchial patency - partial, valve, complete and, respectively, three states of the lung - hypoventilation, obturational emphysema, atelectasis. A small persistent constriction of the bronchus is accompanied by a decrease in the air content in the ventilated part of the lung - hypoventilation. On radiographs and tomograms, this part of the lung slightly decreases, becomes less transparent, the pattern in it increases due to the convergence of blood vessels and plethora. Mediastinal inspiration can move slightly towards hypoventilation.

With obturation emphysema, air during inspiration, when the bronchus expands, penetrates into the alveoli, but with an exhalation it can not immediately leave them. The affected part of the lung increases and becomes lighter than the surrounding parts of the lung, especially during the exhalation period. Finally, with complete closure of the bronchus lumen, complete airlessness arises - atelectasis. The air can no longer penetrate the alveoli. The remaining air in them is resorbed and partially replaced by edematous fluid. The airless area decreases and causes an intense uniform shadow on the radiographs and computer tomograms.

At an occlusion of the main bronchium occurs atelectasis of the entire lung. Occlusion of the lobar bronchus leads to atelectasis of the lobe. The obstruction of the segmental bronchus is completed by segment atelectasis. Subsegmentary atelectasis usually has the form of narrow striae in different parts of the pulmonary fields, and lobules - rounded seals with a diameter of 1 - 1.5 cm.

However, radionuclide method - scintigraphy - became the main radiation method of studying physiology and revealing functional pathology of the lungs. It allows you to assess the state of ventilation, perfusion and pulmonary capillary blood flow, and to obtain both qualitative and quantitative indicators characterizing the entry of gases into the lungs and their removal, as well as the exchange of gases between the alveolar air and blood in the pulmonary capillaries.

For the purpose of investigating cough pulmonary blood flow, perfusion scintigraphy, Hungarian and bronchial patency, is performed by inhalation scintigraphy. In both studies, a radionuclide image of the lung is obtained. To perform perfusion scintigraphy, the labeled ^99m Tc particles of al6umine (microspheres or macroaggregates) are intravenously injected to the patient . Getting into the bloodstream, they are carried away to the right atrium, right ventricle and then into the pulmonary artery system. The particle size is 20-40 μm, which prevents their passage through the capillary bed. Almost 100% of the microspheres get stuck in the capillaries and emit gamma quanta, which are recorded with a gamma camera. The study has no effect on the patient's well-being, since only a small part of the capillaries are turned off from the blood flow. There are approximately 280 billion capillaries per person in the lungs, while only 100-500 thousand particles are administered for the study. A few hours after the injection, the protein particles are destroyed by blood enzymes and macrophages.

For the purpose of evaluating perfusion scintigrams, a qualitative and quantitative analysis is carried out. With qualitative analysis, the shape and size of the lungs are determined in 4 projections: anterior and posterior lines, right and left lateral. Distribution of RFP to pulmonary fields should be uniform. In quantitative analysis, both pulmonary fields on the display screen are divided into three equal parts: upper, middle and lower. The total accumulation of RFP in both lungs is taken as 100%. On the computer, relative radioactivity is calculated, i.e. Accumulation of RFP in each department of the pulmonary field, separately left and right. Normally, according to the right pulmonary field, a higher accumulation is recorded - by 5-10%, and the concentration of RFP over the field increases from the top down. Violations of capillary blood flow are accompanied by a change in the above ratios in the accumulation of RFP in the fields and lungs.

Inhalation scintigraphy is carried out using inert gases -Xe or Kr. An air-xenon mixture is introduced into the closed system of the spirograph. Using the mouthpiece and the nasal clamp, create a closed system of the spirograph - the patient. After achieving dynamic equilibrium, a scintigraphic image of the lung is recorded on the gamma camera and then it is carried out qualitatively and quantitatively in the same way as the perfusion. Areas of pulmonary ventilation disorder correspond to places of reduced accumulation of RFP. This is observed with obstructive lung lesions: bronchitis, bronchial asthma, local pneumosclerosis, bronchial cancer, etc.

For inhalation scintigraphy, aerosols of ^99m Tc are also used . In this case, 1 ml of RFP activity of 74-185 MBq is injected into the nebulizer of the inhaler. Dynamic registration is performed at a rate of 1 frame per second for 15 minutes. The curve activity is time. At the first stage of the study, the state of bronchial patency and ventilation is determined, while the level and degree of obstruction can be determined. At the second stage, when RFP diffuses into the bloodstream through the alveolar-capillary membrane, the intensity of capillary blood flow and the state of the membrane are evaluated. Measurement of regional pulmonary perfusion and ventilation can also be performed by intravenous administration of radioactive xenon dissolved in isotonic sodium chloride solution, followed by recording of lung purification from xenon on the gamma camera.