[Phenomenology of pulmonary HRCT. Definitions, differential diagnosis and clinical relevance].

High-resolution computed tomography (HRCT) has proved to be the imaging technique of choice for the lung in numerous studies, allowing precise depiction of normal pulmonary anatomy-including the lobular architecture-as well as relevant pathologic changes. Its sensitivity, specificity and accuracy in this respect are markedly superior, not only to chest radiography, but also to conventional CT. Guidelines for standardized assessment and interpretation of HRCT findings have not been established in the German literature. The purpose of this paper was to develop a systematic classification of pulmonary HRCT findings based on the appearance of morphologic abnormalities (descriptive classification) and their relationship to anatomic structures of pulmonary parenchyma (anatomic classification). Reticular, nodular, and non-reticular/non-nodular densities, as well as lucencies, can be differentiated. Abnormalities of the pleural space are discussed separately. Following the presentation of typical CT findings, morphologic correlation and differential diagnosis are discussed. In addition, we point out indications and specific features of the clinical value of the technique.