High-resolution computed tomography of the lungs: the borderlands of normality.

High-resolution computed tomography (HRCT) is now widely used in the assessment of airways and diffuse lung disease. Considerable literature on pathologic correlation has increased the understanding of the signs of disease seen on HRCT. However, neither the significance of subtle individual signs nor the spectrum of HRCT appearances in healthy lungs is well documented. HRCT signs that cause diagnostic uncertainty and the spectrum of findings that exist between definite normality and definite abnormality are discussed.