CT signs and patterns of lung disease

A "sign" on CT scanning of the lung refers to a radiologic finding that suggests a specific disease process. Understanding the meaning of a sign implies an understanding of the findings on the CT scan. Knowing the name of the sign is not as important as recognizing the radiologic findings, and understanding the meaning of the findings, but is useful when communicating with clinicians and radiologists who may use the term. A CT "pattern" refers to a nonspecific finding or collection of findings suggesting one or more specific disease processes. This article reviews some of the more common and useful CT signs and patterns of focal and diffuse lung disease.