Neurological Imaging & Neurointervention-Rangaswamy Flashcards
What is the physics of an X-ray?
current thru filament.
heat happens & electron beam hits tungsten
tungsten produces X-rays.
**based on density
What are the 2 types of X-rays?
electron deviates b/c of nucleus & loses energy…energy left comes out as X-ray. Most common–called bremsstrahlung X-ray.
**characteristic xray: electron comes into atom & displaces another atom. less common
Why does bone look white on X-ray?
b/c the calcium blocks the passage of the X-ray.
How does catheter angiography work?
iodine in dye injected into vessels.
this blocks the X-rays. can visualize
How does an ultrasound work?
sound! not dangerous
bounces back & forms an image
things that block the sound waves produce white images.
based on echoic. Hyperechoic: white
How does the doppler work?
try to get blood vessel information
figure out velocity of blood & direction of blood flow
high velocity-narrow blood vessel, possible stenosis.
How does a CT work?
gets a 3D view
cube rotates around the patient
X-rays in many different directions. rotational X-ray source w/ a ring of detectors
What does bone look like on a CT?
white
Can you inject dye & make an angiogram w/ a CT too?
Yes! But inject dye into the vein.
also iodine-based
How does an FDG PET work?
inject labeled glucose
this is nuclear medicine
anything w/ high metabolic activity, like a pathologic tumor will light up.
How does an MRI work?
all of our natural makeup has hydrogen atoms–its magnetic properties are used to give the MRI image
Explain how magnets are involved in MRI.
Each atom has its own magnetic vector.
if you are put into an external magnet–hydrogen atoms align in upward or downward direction. They cancel each other out.
Bo is what is left.
What gives you the image in MRI?
when the atoms go back to their original magnetic vector, release energy that is sensed, each hydrogen’s reaction is unique to its surrounding. Fat adjusts back more quickly than water.
Which MRI shows water as white?
T1 or T2 weighted image?
T2 lights up H2O
What is diffusion tractography?
take a look at a small tract of brain, brain fibers
What are the common neurointerventional surgeries?
angioplasty-to widen a narrowed blood vessel
stent placement
thrombolysis & thrombectomy
coiling-to fix an aneurysm
embolization-to fix vascular malformations, block off unnecessary loops.
What do you look at w/ nuclear medicine & MRI? equivalent to radio density in X-ray & CT?
nuclear medicine: increased activity
MRI: hyperintense v. hypointense
WHat is the def of an acute ischemic stroke?
deficits last more than 24 hours
less than 24 hours–>TIA
Why do you need to do a CT when you suspect a stroke?
see if there is already damage to the brain-completed stroke will show hypo density b/c more water there
look for bleed
How is ischemia different from infarct?
ischemia–not permanent deficits, collateral blood flow saves the tissue
infarct-dead tissue no blood supply for long enough to get cell death
How do you treat ischemic stroke from clot?
TPA (small vessel occlusion)
or CT angiography-get rid of the clot that way! (large vessel occlusion)
Close to the time of stroke…will you see evidence on CT?
no, better on MRI
Where do you usu see aneurysms in the brain?
usu in blood vessels at the base of the brain
can turn into a subarachnoid hemorrhage if it bursts
When would you be more worried about SAH…headache following trauma? Not following trauma?
More worried if headache is unprovoked
Why does blood appear bright even on T1?
ferritin shines white
T/F Meningioma is vascular tumor.
True.
also, it arises commonly from dura mater.
What are bad signs for a tumor?
edema necrosis enhancement hemorrhage bad signs for tumor-could point to glioblastoma multiform
What is the characteristic morphology of MS on imaging?
Dawson Finger
white radiation off of corpus callosum
lose oligodendrocytes-demyelination
