[en] The main purpose of this study has been introduction of a new method for alveoli-capillary permeability evaluation. Many reports pointed out to the altered transit of soluble particles through this barrier. From pathophysiological aspect the main interest is the elucidation of permeability's alteration in different pulmonary pathology. We decided to use for lung epithelial permeability measurements ^99mTc-DTPA inhaled aerosols and sequential assessment of its lung clearance. The aerosols were obtained using oxygen flow nebulizers with aerosols' generators Ultra Vent (Malinkrodt) and Venticis II (CIS bio international) that enabled as to get submicron particles. Oxygen flow between 9 and 11 liters per minute was used. Optimum images were obtained with 1480 MBq of inhaled aerosols at least 2 to 3 minutes. DTPA that was used for aerosols labeling had been produced in our Department and the results were compared with DTPA provided by CIS bio international. High correlation between both agents was proven. During the whole study ex tamper prepared radiopharmaceuticals were used and quality control was done using paper chromatography method. Acquisition was done in sitting position with gamma camera interfaced to a ADAC and Scintiview. The measurements lasted for 20 minutes. Data were stored on 64x64 matrices. Regions of interest over both lungs were drown and each one was divided in three segments: apical, medial, and basal. Using computer program curves of ^99mTc-DTPA lung clearance were derived. From the obtained time activity curves half-time of the global and the regional lung clearance was assessed. In the control group comprised of 32 healthy volunteers (non-smokers) we had got values, used after works as reference range. Our normal values for global clearance are: 68±5,5 min. for left whole lung, 68,1±6,5 min for right whole lung, and 49±7,7 min for apical, 66,9±8 min for middle, and 75,9±6,4 min basal regional lung clearance, and they are in keeping with the normals reported by many authors. Standardizing the procedures and establishing the normal range we started to use already proven method in different groups of subjects exposed to harmful agents supposed that alter epithelial integrity. Increased lung clearance of inhaled aerosols were obtained in non-symptomatic smokers, asbestosis suffering patients, and in non-smokers exposed to asbestos with normal lung ventilation studies. Faster clearance was also found in the patients with chronic renal failure on regular haemodialysis program using bio incompatible membrane, longer than 5 years. At the same time normal values were obtained in the group on short term haemodialysis. Abnormal clearance rate was shown in patients with malignant disease, exposed to external and internal lung radiation, and in subjects on long term amiodarone treatment, as well. In patients with cardiac heart failure and lung edema, and first stage of sarcoidosis, lung clearance was normal. It remains now as further challenge comparison of there values with some other investigations, expectantly it would contribute in elucidation of different mechanisms in pulmonary pathology. Assessment of ^99mTc-DTPA lung clearance is a very attractive method, non-invasive, cheap, and widely available. Until now there is no an other alternative procedure that would be able to give us more information about epithelial permeability. (Author)