Anatomy.—Centrilobular describes the region of the bronchiolovascular core of a secondary pulmonary lobule (4,39,40). This term is also used by pathologists to describe the location of lesions beyond the terminal bronchiole that center on respiratory bronchioles or even alveolar ducts.
CT scans.–A small dotlike or linear opacity in the center of a normal secondary pulmonary lobule, most obvious within 1 cm of a pleural surface, represents the intralobular artery (approximately 1 mm in diameter) (41). Centrilobular abnormalities include (a) nodules, (b) a tree-in-bud pattern indicating small-airways disease, (c) increased visibility of centrilobular structures due to thickening or infiltration of the adjacent interstitium, or (d) abnormal areas of low attenuation caused by centrilobular emphysema (4). (See also lobular core structures.) [Fleischner Society]