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