====== T2-weighted magnetic resonance imaging sequence ======

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(also referred to as [[T2WI]]) is one of the basic pulse sequences in [[MRI]] and demonstrates the differences in the [[T2]] relaxation time of tissues.

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.

Summary

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
((Bauer S, Wagner M, Seiler A, Hattingen E, Deichmann R, Nöth U, Singer OC.
Quantitative T2'-mapping in acute ischemic stroke. Stroke. 2014
Nov;45(11):3280-6. doi: 10.1161/STROKEAHA.114.006530. Epub 2014 Oct 2. PubMed
PMID: 25278559.
)).

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The relationship of the presence, absence or extent of intramedullary [[T2 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.