Ring-enhancing lesion
Encyclopedia
A ring-enhancing lesion is an abnormal finding on CT scan obtained using radiocontrast
. On the image there is an area of decreased density (see radiodensity
) surrounded by a bright rim from concentration of the enhancing contrast dye. This can be a finding in numerous disease states. In the brain, it can occur with an early brain abscess
as well as in Nocardia
infections associated with lung cavitary lesions. In patients with HIV the major differential is between CNS lymphoma and CNS Toxoplasmosis
.
Radiocontrast
Radiocontrast agents are a type of medical contrast medium used to improve the visibility of internal bodily structures in an X-ray based imaging techniques such as computed tomography or radiography...
. On the image there is an area of decreased density (see radiodensity
Radiodensity
Radiodensity refers to the relative inability of electromagnetic radiation, particularly X-rays, to pass through a particular material. Radiolucency indicates greater transparency or "transradiancy" to X-ray photons...
) surrounded by a bright rim from concentration of the enhancing contrast dye. This can be a finding in numerous disease states. In the brain, it can occur with an early brain abscess
Brain abscess
Brain abscess is an abscess caused by inflammation and collection of infected material, coming from local or remote infectious sources, within the brain tissue...
as well as in Nocardia
Nocardia
Nocardia is a genus of weakly staining Gram-positive, catalase-positive, rod-shaped bacteria. It forms partially acid-fast beaded branching filaments . It has a total of 85 species. Some species are non-pathogenic while others are responsible for nocardiosis. Nocardia are found worldwide in soil...
infections associated with lung cavitary lesions. In patients with HIV the major differential is between CNS lymphoma and CNS Toxoplasmosis
Toxoplasmosis
Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii. The parasite infects most genera of warm-blooded animals, including humans, but the primary host is the felid family. Animals are infected by eating infected meat, by ingestion of feces of a cat that has itself...
.