PENUMBRA | Definition and Meaning

Definition of Penumbra

Penumbra

pen·um·bra

Definition/Meaning

(noun)

Partial shadow area between light and darkness, especially during an eclipse.

e.g. The penumbra of the moon's shadow fell on the Earth's surface.

(noun)

a space of partial illumination (as in an eclipse) between the perfect shadow on all sides and the full light;

e.g. The day of the solar eclipse, we all left our offices with our viewing devices to stare at the sky in hope of seeing the penumbra.

(noun)

the 'ischemic penumbra' is a very specific region in brain imaging in stroke medicine, referring to a rim of tissue lying just outside the ischemic region, which is that area most severely damaged by the stroke or ischemic event. The 'ischemic penumbra' is medically important because it that area of the brain then that is less damaged, and reveals prognosis, and where treatment may be targeted;

e.g. Time is brain in stroke: get to the hospital as soon as you suspect one, for a good radiographic image of the ischemic penumbra.

(noun)

a blurred area in a radiograph at the edge of an anatomical structure;

e.g. The radiologist was concerned about an area of penumbra on the radiograph, and therefore asked to have the whole series repeated before the patient was allowed to leave the cancer center.

(noun)

body of rights guaranteed by implication in a civil constitution;

e.g. The 'penumbra' is a very specific concept in U.S. constitutional law, defining a group of rights derived by implication from other rights specifically stated in the Bill of Rights.