The distribution of nodules shown on HRCT is the most important factor in making an accurate diagnosis in the nodular pattern. In most cases small nodules can be placed into one of three categories: perilymphatic, centrilobular or random distribution. Random refers to no preference for a specific location in the secondary lobule. Perilymphatic distribution In patients with a perilymphatic distribution, nodules are seen in relation to pleural surfaces, interlobular septa and the peribronchovascular interstitium. Nodules are almost always visible in a subpleural location, particularly in relation to the fissures. Centrilobular distribution In certain diseases, nodules are limited to the centrilobular region. Unlike perilymphatic and random nodules, centrilobular nodules spare the pleural surfaces. The most peripheral nodules are centered 5-10mm from fissures or the pleural surface. Random distribution Nodules are randomly distributed relative to structures of the lung and secondary lobule. Nodules can usually be seen to involve the pleural surfaces and fissures, but lack the subpleural predominance often seen in patients with a perilymphatic distribution. #Diagnosis #Radiology #Pulmonary #HRCT #NodularPattern #Nodular #Pattern #Distribution #Random #Centrilobular #Perilymphatic #Comparison #Diagram #RadiologyAssistant
