T2 washout
Citation, DOI, disclosures and article data
At the time the article was created Prashant Mudgal had no recorded disclosures.
View Prashant Mudgal's current disclosuresAt the time the article was last revised Henry Knipe had the following disclosures:
- Radiopaedia Events Pty Ltd, Speaker fees (past)
- Integral Diagnostics, Shareholder (ongoing)
- Micro-X Ltd, Shareholder (ongoing)
These were assessed during peer review and were determined to not be relevant to the changes that were made.
View Henry Knipe's current disclosuresT2 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 edema both surrounding tumors and during the subacute phase of ischemic stroke.
T2 washout should not be confused with related phenomena in ischemic stroke; early DWI reversal, seen acutely (typically 3-6 hours) and ADC pseudonormalization seen somewhat later (around 1 week post stroke) but before T2 washout, which occurs between 10-15 days typically.
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References
- 1. Casey S. "T2 washout": an explanation for normal diffusion-weighted images despite abnormal apparent diffusion coefficient maps. AJNR Am J Neuroradiol. 2001;22 (8): 1450-1. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 2. . Diffusion-Weighted MR Imaging of the Brain. Springer. (2009) ISBN:3540787852. Read it at Google Books - Find it at Amazon
- 3. Hiwatashi A, Kinoshita T, Moritani T et-al. Hypointensity on diffusion-weighted MRI of the brain related to T2 shortening and susceptibility effects. AJR Am J Roentgenol. 2003;181 (6): 1705-9. doi:10.2214/ajr.181.6.1811705 - Pubmed citation
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