T2 weighted imaging
In T2 weighted imaging (T2WI) water is bright. For instance, on the provided image, the CSF is bright. This is important because things that cause oedema increase the water concentration in the tissue and make it brighter on T2 weighted imaging.
N.B. when we say a signal is bright we mean it is whiter. Darker signals are blacker.
Dark on T2WI
Things that are dark on T2 include materials that have very little water and, therefore, hydrogen atoms; things that cause susceptibility effect; and anything that is flowing e.g. blood within the dural venous sinuses and arteries.
- blood (depending on age)
- fibrosis / calcium / sclerosis
- “flow voids” created by moving material e.g. blood in dural venous sinuses and arteries and fluid within the CSF spaces
Bright on T2WI
Things that are bright on T2WI contain water or fat or indicate gliosis.
- water
- fat
- gliosis