Neuroradiology 2 Flashcards
functional MRI
active areas have higher local blood flow and higher concentration of oxygenated hemoglobin- creates a higher MR signal than inactivated cortex
MRI technique
subject given a specific task (paradigm)
take a pre-MRI and a during MRI to find differences in activity levels
fMRI applications
preop localization of cortical function
selection of awake vs non awake craniotomy
research- NFL, working memory
angiograms
non invasive- CT angiography, MR angiography
invasive- catheter angiography
CTA
iv iodine contrast given rapidly
start scan after IV contrast
arteries brightly enhancing
veins wont yet be enhanced
anatomic coverage- aortic arch, neck, brain
displayed with 2D techniques that can be shown in any plane
OR
3D- high density structures- not used for stenoses or occlusions- used for aneurism
strengths and limitations of CTA
fast
large scan area
shows lumens
shows wall characteristics
need contrast
allergies to contrast
contrast renal failure
radiation exposure
MRA
uses gadollinium contrast (sometimes)
evaluates the arch, neck, and brain
IV contrast injected rapidly
start scans 20 seconds later- only arteries visualized
other tissues subtracted
w/o contrast- can be done on brain on small anatomic areas- circle of willis
takes a long time
uses differences in flow to generate image
capitalizes on
what info does MRI give you about the vessel wall?
none- lumen only
MRA strengths and weaknesses
no radiation- good follow up
bones not imaged-less artifact at skull base
IV contrast not needed
weak:
long acquisition time
contrast required for carotid arteries
no wall info
risk/benefits for angiography
highest spatial resolutoin- gold standard
flow dynamics
most sensitive for small aneurysms and small vessel apthology
risk
expense
only lumen visualized
risks: transient neurologic deficit, stroke, puncture site
cerebral angiogram interventions
aneurysm coiling
removal of lysis of intraarterial blood clots
embolization of vascular malformations
treatment of vasospasms
bone breaks are easier visualized on what?
CT
spinal cord is better visualized on?
MRI
syrinx
fluid filled cavity in spinal cord
contraindicatoins to MRI
pacemaker
certain metallic implants
vascular clips
metal foreign body in/around eye
