Rapid Review of Radiology by Hussain Shahid & Latif Sherif Aaron Abdel & Hall Adrian David

Author:Hussain, Shahid & Latif, Sherif Aaron Abdel & Hall, Adrian David [Hussain, Shahid]
Language: eng
Format: mobi
Publisher: Manson Publishing
Published: 2010-05-29T16:00:00+00:00

Practical tips

• These are examples of comparatively rare and very specific infarcts but they do make for an interesting test of neuroanatomy understanding!

• DWI depicts reduction in Brownian motion of water molecules. Cytotoxic oedema in acute infarction will produce this and present high signal on the DWI scan. It is very sensitive, depicting infarcts just 30 min or so from onset.

• The DWI image also has inherent T2 weighting (T2 ‘shine through’), that is, the signal is a combination of T2 weighted and reduced diffusion. As such, it may not distinguish an older infarct (T2 hyperintense) from a recent one (reduced diffusion) as both will appear bright. An alternative depiction that can differentiate acute and nonacute infarcts is the apparent diffusion coefficient (ADC) map. This has no T2 component and shows reduced diffusion (i.e. acute infarct) as low signal. An older infarct that is also bright on DWI by virtue of T2 ‘shine through’ will be bright on ADC.

• Ischaemia is not the only cause of reduced diffusion. Others include seizure, trauma, hypoglycaemia, abscess.

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