Differentiation of etiology of nodular changes in high resolution computed tomography (HRCT) in interstitial lung diseases.

High resolution computed tomography (HRCT) enables imaging of morphological changes invisible on plain chest radiograms or conventional CT. This is related to thin collimations of the scans and sharp (bone) algorithm of image reconstruction. In HRCT the lung interstitium may be evaluated at the level of the smallest functional unit, namely pulmonary lobule. Nodular changes are among the most frequent morphological changes in interstitial lung diseases. The aim of the study is evaluation of frequency and character of nodular changes in HRCT in interstitial lung diseases. HRCT enables imaging of nodular changes in miliary tuberculosis, before they are visible on radiograms. Perilymphatic nodules are typical in sarcoidosis, lymphangitic spread of carcinoma and pneumoconiosis. In sarcoidosis nodules predominate along the peribronchovascular cuffs and in subpleural regions, in lymphangitic spread of carcinoma they are septal and peribronchovascular. In pneumoconiosis nodules are centrilobular and subpleural. The assessment of character and localization of nodules in interstitial lung disease is not sufficient in reliable differentiation, but may be helpful in differential diagnosis in association in other HRCT findings.