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Flashcards in Neuroradiology Deck (4)
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1

CT (computed tomography) vs MRI

-CT uses X-rays, MRI uses NMR
-CT is fast and available, excellent in emergency settings
-MRI is slower and expensive, but shows better tissue contrast
-MRI maps signals from hydrogen atoms in water and fat
-There is no ionizing radiation in MRI and it allows for a more specific Dx
-MRIs can use different sequences to weight the tissues in different ways

2

MRI sequences

-The main two sequences used are: T1 weighted (T1WI) and T2 weighted (T2WI)
-A third type is fat suppressed
-In T1WI the water (and thus CSF) is dark, and on T2WI the water is light
-White matter is slightly bright on T1 and slightly dark on T2
-Vessels are dark on both T1 and T2, but bright on post-contrast T1 (gadolinium)
-Brain lesions are dark on T1 and bright on T2
-Fat is bright on both T1 and T2 and dark on fat suppressed
-Hematomas vary in appearance (acute is usually bright on T1 and dark on T2)

3

Contrast MRI

-Use of gadolinium as contrast agent allows for visualization of many important things
-Use of gadolinium lets you seen vessels (appear bright) and vascular malformations
-It also lets you see intracranial neoplasms and infections, which break down the BBB

4

Density of components of the brain

-CT scans show the most dense things white and least dense things black
-Most to least dense: bone>blood>gray matter>white matter>CSF>fat
-Therefore, grey matter looks lighter than white matter
-Blood looks the lightest of all the non-bone substances so can easily see a hematoma/hemorrhage

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