Penumbra used in a sentence

Penumbra in a sentence as a noun

The penumbra can be visualised using quite clever MRI [2].

This penumbra of tissue dies off over time, and can be saved if the blood supply is reconstituted.

The reason for this is that when part of the brain becomes ischaemic, a central core dies instantly but around this there is a halo or penumbra that is not dead but at risk.