T2 washout

T2 washout is a phenomenon encountered on diffusion weighted imaging (DWI) which results in DWI images (e.g. B = 1000) appearing normal despite abnormal ADC maps

For the phenomenon to occur a particular combination of ADC and T2 signal intensity is required. 

  • increased T2 signal
  • facilitated diffusion (high ADC values) 

Remembering that the signal of diffusion weighted images is the result of both diffusion and T2 signal, it becomes apparent that if the amount of expected T2 shine through from the increased T2 signal, is balanced by elevated ADC values (which would result in lower DWI signal intensity)  then DWI signal may appear normal 1-3

The phenomenon is most commonly observed with vasogenic oedema both surrounding tumours and during the subacute phase of ischaemic stroke

T2 washout should not be confused with related phenomena in ischaemic stroke; early DWI reversal, seen acutely (typically 3-6 hours) and ADC pseudonormalisation seen somewhat later (around 1 week post stroke) but before T2 washout, which occurs between 10-15 days typically. 

 


Stroke and intracranial haemorrhage
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Article Information

rID: 28356
Section: Physics
Synonyms or Alternate Spellings:

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