View source for Brain MRI

==Background==
*MRI uses magnetic fields and radiowaves to develop high definition imaging of the brain and excellent tissue contrast
*No radiation associated with imaging
*Ideal for looking at brain parenchyma and midbrain
*Contrast is commented on by signal intensity
**Dark areas are hypointense
**Bright areas are hyperintense

==MRI Modalities==
===T1 Weighted Imaging===
[[File:T1 Brain.png|150px]]
*Ideal for brain parenchyma
*With the addition of contrast, this can differentiate causes of inflammation
*Fluid is hypointense (similar to CT imaging)
*Methemoglobin, fat, and protein are hyperintense

===T2 Weighted Imaging===
*Highlights CSF
*Good for identifying tissue edema around pathologic areas
*Fluid is hyperintense (reverse of T1)
*Tissue tends to be more hypointense

===Fluid Attenuation Inversion Recovery (FLAIR)===
*Appears as T2 images with hypointense CSF
*Ideal for identifying tumors/GBS
*Also used to identify leptomeningeal enhancement in meningitis

===Diffusion Weighted Imaging (DWI)===
*A method of measuring the Brownian motion of water molecules 
*Diffusion within the intracellular fluid, diffusion within extracellular fluid, and between these areas will differ depending on pathology
*Ideal for cellular swelling especially in acute ischemic stroke which will be hyperintense

==Blood==
{| class="wikitable"
|-
! Age of Blood !! T1 Imaging !! T2 Imaging
|-
| Hyperacute || Iso|| Bright 
|-
| Acute || Iso/Dark || Dark 
|-
| 1-3 Days || Bright || Dark 
|-
| 1-2 Wks || Bright || Bright 
|-
| 2-3 Wks || Iso/Dark || Dark 
|}

==See Also==
*[[MRI (main)]]

[[Category:Neurology]]
[[Category:Radiology]]