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Signs & patterns of lung diseases on X-ray and CT: terminology

Added by: Владислав Банников
March 22, 2024

Tram tracks, bull’s eye, buds on a tree, honeycomb… Do you know you can find all these in a lung?

Here is a list of metaphorical terms that describe signs and patterns of lung disease on X-ray or CT images.

➕ Tram-track sign

- thickened non-tapering (parallel) walls of cylindrical bronchiectasis (more info & images on, including differentiation from tram-track signs in other parts of the body)

➕ Mosaic attenuation pattern

- a patchwork of regions of differing pulmonary attenuation on CT imaging (more info & images on

➕ Tree-in-bud

- CT appearance of multiple areas of centrilobular nodules with a linear branching pattern (more info & images on

➕ Ground-glass opacification/opacity (GGO)

- a descriptive term referring to an area of increased attenuation in the lung on computed tomography (CT) with preserved bronchial and vascular markings (more info & images on

➕ Bulls-eye

- central ground glass opacity surrounded by an inner ring of air and an outer ring of ground glass in the right lower lobe (see an example in a scientific publication); a more common name is "pulmonary target sign" (

➕ “Honeycomb” lung / honeycombing

- a CT imaging descriptor referring to clustered cystic air spaces (between 3 and 10 mm in diameter, but occasionally as large as 2.5 cm) that are usually subpleural, peripheral, and basal in distribution (more info & images on

➕ Crazy paving

- ground-glass opacities with superimposed interlobular septal thickening and intralobular septal thickening, seen on chest HRCT or standard CT chest (more info & images on

➕ Bat wing / butterfly / angel wing

- symmetrical perihilar ground-glass opacities with a wing-like shape (see an example in a scientific publication)

➕ Comet tail

- a curvilinear opacity that extends from a subpleural "mass" toward the ipsilateral hilum (more info & images on

➕ Galaxy sign

- a coalescent granuloma seen in a minority of patients with pulmonary sarcoidosis (more info & images on

Have you encountered other metaphorical terms in pulmonology? You're welcome to share them in the comments.

Image by toubibe from Pixabay


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