Overview of Ground-Glass Opacity on CT: A Must for the Diagnostic Radiologist

Ground-glass opacity is a commonly encountered, nonspecific finding in the lung parenchyma on chest CT. Because of increasing and widespread use of CT, an improved understanding of ground-glass opacity will contribute to optimized patient care.1-3 Ground-glass opacity has been described as a potential finding in virtually all pulmonary neoplastic, infectious, and inflammatory conditions; thus, the specificity of this finding in a given case is limited. Even when correlating with the clinical setting, a wide differential diagnosis often is applicable.1-4 Thus, it is important for the radiologist to have a systematic approach and review all relevant data, both imaging and clinical, in order to best assist the referring physician for care of the patient. The objectives of this article are to discuss the etiopathogenesis and characteristic CT imaging appearance of ground-glass opacity; suggest and review methods to classify ground-glass opacity based on distribution, acuity, and cause (to provide the most concise differential diagnosis); and provide an overview of the more frequently encountered and well-known causes of ground-glass opacity in daily radiologic practice.