0 Diffusion MRI

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Diffusion MRI is a magnetic resonance imaging (MRI) technique that exploits characteristics of water diffusion. 

Diffusion weighted imaging (DWI) helps to image changes in the random motion (brownian) of water molecules.

There is inverse relation of water diffusion in ECF (extracellular) and ICF (intracellular). Cells having high NC ratio (nucleus-to-cytoplasm ratio) and high cellurarity tissues have large IC volume, therefore reduced EC volume which result in reduced diffusion of water molecules -- termed Restricted diffusion.

Restricted diffusion: increased signal intensity (hyperintensity) on DWI and low signal intensity (hypointense) on apparent diffusion coefficient (ADC) maps.

Points to remember for MCQs

Restricted diffusion is seen in :

1. Acute Infarct (because of Cytotoxic edema)
2. Epidermoid
3. Abcess
4. High cellularity tumors

Mimic:
T2 shine through: Hyperintense on both DWI and ADC, is not Restricted diffusion.

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References:
1. Haaga JR, Boll D. CT and MRI of the whole body. Mosby. (2009) ISBN:0323053750. Read it at Google Books - Find it at Amazon

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