cylindrical or tubular type

signet appearance due to dilated bronchus in near to

pulmonary artery.

In normal individuals, the adjacent pulmonary artery is the same size, or minimally smaller, than the bronchus. A bronchoarterial ratio >1.2 is indicative of abnormal bronchial dilatation. Substantial dilatation of the bronchus and smooth mural thickening results in a signet ring configuration

Reference:BiblioMed Textbook-Computed Body Tomography

cylindrical or tubular type

arrowhead=bronchial wall thickening in transverse section.
short arrow= in longitudinal section.
Normal bronchi are not visible on CT in the most peripheral areas of the lung, within 2 cm of the costal or paravertebral pleura. The cardinal sign of bronchiectasis on HRCT is dilatation of the bronchus, which usually is accompanied by bronchial wall thickening (internal diameter <80%>1.2 is indicative of abnormal bronchial dilatation.

Reference:BiblioMed Textbook-Computed Body Tomography