Rationale, Updates, and Structure of the Glossary

Apuntes

We hope that this fourth edition of the Fleischner Society Glossary of Terms for Thoracic Imaging will be helpful for both radiologists and the respiratory medicine community at large. Because terminology is evolving, the provided definitions should be understood as a consensus proposal rather than strict rules. It is anticipated that systematic evaluations of the utilization of this glossary will be undertaken. Acinus (Pl. Acini) (Anatomy) The acinus is a structural unit of the lung distal to the terminal bronchiole* and is supplied by a first-order respiratory bronchi- ole, with a diameter of approximately 4-8 mm. The secondary pulmonary lobule* contains between three and 25 acini. Within the acinus, all parts are involved in gas exchange (ie, they contain alveoli). The acinus consists of respiratory bronchioles, alveolar ducts, and alveoli. Normal acini are not visible radiologically but the accumulation of pathologic material within acini may be seen as small ill-defined rounded opacities (opacity*), sometimes called “air space nodules” (9,10). Air Bronchogram (Pathology) [Descriptor] (Fig 1) Air bronchogram is the descriptive term for air-filled airways* within lung parenchyma...