Neuroradiology Flashcards
1
Q
CT (computed tomography) vs MRI
A
- 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
Q
MRI sequences
A
- 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
Q
Contrast MRI
A
- 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
Q
Density of components of the brain
A
- 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
