Brain MRI: Difference between revisions
(additional explanation of what flair imaging shows) |
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{{MR studies CVA/TIA}} | {{MR studies CVA/TIA}} | ||
''Contrast only needed if concern for malignancy/mass'' | |||
==MRI Modalities== | ==MRI Modalities== | ||
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===Fluid Attenuation Inversion Recovery (FLAIR)=== | ===Fluid Attenuation Inversion Recovery (FLAIR)=== | ||
[[File:FLAIR Brain.png|150px]] | [[File:FLAIR Brain.png|150px]] | ||
*Appears as T2 images with hypointense CSF | *Appears as T2 images with hypointense CSF- cancels out CSF so you can differentiate CSF from other fluid | ||
*Ideal for identifying tumors/GBS | *Ideal for identifying tumors/GBS | ||
*Also used to identify leptomeningeal enhancement in meningitis | *Also used to identify leptomeningeal enhancement in meningitis | ||
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==See Also== | ==See Also== | ||
*[[MRI (main)]] | *[[MRI (main)]] | ||
==References== | |||
<references/> | |||
[[Category:Neurology]] | [[Category:Neurology]] | ||
[[Category:Radiology]] | [[Category:Radiology]] |
Latest revision as of 15:58, 9 May 2017
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
Ordering Studies
MR Imaging (for Rule-Out CVA or TIA)
- MRI Brain with DWI, ADC (without contrast) AND
- Cervical vascular imaging (ACEP Level B in patients with high short-term risk for stroke):[1]
- MRA brain (without contrast) AND
- MRA neck (without contrast)
- May instead use Carotid CTA or US (Carotid US slightly less sensitive than MRA)[2] (ACEP Level C)
Contrast only needed if concern for malignancy/mass
MRI Modalities
T1 Weighted Imaging
- 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- cancels out CSF so you can differentiate CSF from other fluid
- 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
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 |