Neuroimaging

Question 1

How do important materials look on CT?

Answer 1

Air is VERY black
water less black
brain is grey
edema is darker grey (at least 6-8 hrs post-event)
blood, and contrast are the same housefield unit- so you need to know if you have contrast CT! Both are quite white
bone is whitest of all.

Question 2

What kind of abnormalites can you see on CT?

Answer 2

BIG things. good for blood (stroke, head trauma) contrast helps you see massess/abscesses.

Question 3

How do you describe findings on CT

Answer 3

in terms of density. (NOT intensity)

Question 4

What are disadvantages of CT? Advantage?

Answer 4

LOTS of X-ray radiation
axial and coronal view only
new stuff less likely to show up.
not very sensitive
Advantage: much faster, less claustrophobic. relatively specific.

Question 5

What do epidural hematomas look like?

Answer 5

concave white thing

Question 6

What are common characteristics of epidural hematoma?

Answer 6

convex white thing; midline shift common

Question 7

In addition to hematomas, what is another finding that can be seen on CT?

Answer 7

intracerebral hemorrhage

Question 8

What is contrast? What can it help us see?

Answer 8

IV iodinated dye that highlights breakdown of blood brain barrier
helps us see tumors, abscesses, and vascular malformations

Question 9

What are contraindications for CT contrast?

Answer 9

renal insufficiency, allergies

Question 10

What are the early ischemic signs on CT?

Answer 10

sulcal effacement and loss of cortical ribbon (ie the color looks normal but the brain is too smooth looking)
and hyperdense arteries (acute clot)

Question 11

What is CT angiography?

Answer 11

contrasted study with time series of images to track bolus. you can reconstruct vessels in 3D

Question 12

What is CT perfusion?

Answer 12

contrasted study that measures tissue viability. It can measure blood volume and blood transit time (without blood volume, tissue will start to die. if there isn’t a change in blood volume, but transit time is slow, you can still potentially save tissue with surgery or something similar)

Question 13

What are advantages of MRI? Disadvantage?

Answer 13

advantage: can order axial, sagittal, or coronal cuts; magnetic- so no radiation exposure, no bone artifacts, more sensitive and more contrast btw gray and white matter
but, slow and expensive. Also arteries don’t show up, because blood is flowing too much. can’t do in ppl with pacemakers.

Question 14

What are T1, T2, and FLAIR MRI views?

Answer 14

T1: white matter white, grey matter grey CSF dark
T2: white matter grey, grey matter white. CSF bright
FLAIR: white matter grey, grey matter white, CSF dark. abnormal white matter is hyperintense (but be careful about abnormalities that are too close to the ventricles)

Question 15

What is MRI contrast?

Answer 15

gadolinium DTPA. also shows BBB breakdown (abscesses, neoplasms, subacute cerebral infarctions.

Question 16

What is DWI and ADC?

Answer 16

useful for evaluation of acute strokes (stroke area = white on DWI and dark on ADC. Dark ADC indicates cortical white matter tract disorganization.

Question 17

What is GRE>

Answer 17

Gradient recall echo- good for finding microhemorrhages (look like little dark holes in brain) (example showed was amyloid angiopathy

Question 18

What is MRA/ MR angiography?

Answer 18

visualize blood vessels. much safer than CT angiography (no radiation, no arterial puncture, no contrast). overestimates stenosis and may suggest arterial occlusion in cases of high grade stenosis. good for cerebral aneurysms, arteriovenous malformations, arterial dissection, CNS vasculitis, and arterial stenosis. CT is btter for cerebral aneurysms and cartodi stenosis- slightly more sensitive.

Question 19

What is SPECT>

Answer 19

labels metabolic substrates- good for detecting areas of altered metab like cancer or seizure

Question 20

What is fMRI?

Answer 20

meausures brain activity by detecting associated changes in blood flow based on nearby deoxygenated Hb- not used much clinically

Question 21

What types of blood abnormalities can we see on CT and MRI?

Answer 21

CT: hemorrhage
MRI: GRE shows microhemorrhages

Question 22

What kinds of ischemia abnormalities can we see on CT and MRI?

Answer 22

CT: early ischemic changes are sucal effacement and hyperdence MCA
MRI: acute ischemic areas with DWI/ADC

Question 23

What masses/abscesses can we see on CT/MRI?

Answer 23

CT: parenchyma changes; enhancements post contrast
MRI: T1 pre and post contrast

Question 24

What demyelination lesions can we see on CT/MRI?

Answer 24

CT: hard to assess. white matter may be hypodense
MRI; FLAIR to assess for hyperintensities. contrast enhancement if lesions are active. Dawson’s fingers seen in saggital MRI of MS in many cases.

Question 25

What small vessel disease can we see on CT/MRI?

Answer 25

CT: hypodense white matter

MRI” flair to assess for cortical hyperintensities.