IMAGING OF SMALL AIRWAYS DISEASE

High-resolution computed tomography (HRCT) is the most useful modality for imaging of small airways disease, Direct signs of small airways d isease that appear on HRCT scans are the result of changes in the airw ay wall or lumen. Abnormal small airways can be seen as tubular, nodul ar, or branching linear structures on HRCT scans, Indirect signs of sm all airways disease result from changes in the lung parenchyma distal to the diseased small airway and include air trapping, subsegmental at electasis, centrilobular emphysema, and air-space nodules, Diverse inf lammatory and infectious processes, such as bronchiolitis obliterans ( BO), bronchiolitis obliterans with organizing pneumonia (BOOP), smokin g-related diseases, and asthma affect the small airways of the lungs, HRCT findings of BO include air trapping and bronchiectasis. The predo minant findings of POOP are consolidation and ground-glass attenuation , HRCT can show abnormalities such as small nodules and areas of groun d-glass attenuation even in asymptomatic smokers, but emphysema predom inates in smokers with moderate or severe obstructive disease, Patient s with asthma can have thickened airway walls, plugged large and small airways, subsegmental atelectasis, and air trapping, but emphysema is rarely seen even in severe asthma patients, HRCT scans can often accu rately depict disease processes in the small airways and can occasiona lly lead to a specific diagnosis from among several clinically relevan t possibilities.