The T2WI relies upon the transverse relaxation of the net magnetisation vector (NMV). T2 weighting tend to have long TE and TR times.
Paramagnetic contrast agents, e.g. gadolinium-containing compounds, do not have nearly as significant effect as they do in T1WI.
TR: long TE: long fat: intermediate-bright fluid: bright
Quantitative T2'-mapping detects regional changes in the relation of oxygenated and deoxygenated hemoglobin and might reflect areas with increased oxygen extraction.
Motion-corrected T2'-mapping reveals significant and gradually declining values from healthy to perfusion-disturbed to apparent diffusion coefficient-restricted tissue. Current T2'-mapping can differentiate between the ischemic core and the perfusion-impaired areas but not on its own between penumbral and oligemic tissue 1).
The relationship of the presence, absence or extent of intramedullary T2 weighted signal change to clinical myelopathy, and to the likely outcome after surgery, remains complex and controversial.
More recent publications tend to indicate that T2 weighted signal change, particularly if multisegmental, is a poor prognostic feature for response to surgery.