Thin-section CT of the lungs: the Hinterland of normal

Thin-section computed tomography (CT) of the lungs was introduced more than 20 years ago and has an established role in the assessment of patients who are known to have, or are suspected of having, diffuse lung disease. Thin-section CT can demonstrate very early disease, sometimes in individuals without symptoms or pulmonary function test abnormalities. Such sensitivity comes at a price because it may be difficult to distinguish thin-section CT findings that lie within the normal range from those that represent early, but important, disease. This review examines particular thin-section CT findings that occupy the gray area between unequivocal health and definite disease, with a particular focus on the effects of cigarette smoking and aging.