5 Intro to Neuronrad II

Question 1

(THESE ARE MOSTLY FROM MIKE SUN’S NOTES)

Answer 1

Thanks!

Question 2

What is MR Spectroscopy?

Answer 2

Used along with conventional MR sequence to narrow in on a pathological proces

Shows different peaks for different substances, e.g.

• 1st peak = choline from membranes; incr in neoplasm
• 2nd peak = creatine; used as a constant ref point
• 3rd peak = N-acetylaspartate, an amino acid in neurons; decr w/ neuron destruction, tumors
• lactate peak = ischemia

Question 3

When do you use fMRI?

Answer 3

used to localize the region of cerebral cortex that controls a specific function

• if the cortex is injured, has it migrated elsewhere?

Question 4

How does fMRI work?

Answer 4

• areas of higher blood flow and therefore [O₂] show up as brighter, therefore ACTIVE cortex is BRIGHTER

Question 5

How do you run an fMRI (i.e. what do you tell the patient to do)?

Answer 5

1. take basline reading
2. have pt. do the specific task you want to evaluate (e.g. reading, tapping foot, etc.)
3. compare these two images

Question 6

What dye does CT contrast use? When is it contraindicated?

Answer 6

iodine; contraindicated if Iodine allergy or renal insuff. b/c can cause renal tubular necrosis

Question 7

What dye does MRI contrast use? When is a possible complication?

Answer 7

gadolinium; won’t harm kidneys, per se, but can build up there and cause nephrogenic systemic fibrosis (NSF)

Question 8

What are different ways of imaging the cerebral vasculature? (3)

Answer 8

Non-Invasive: CT angio, MR angio (MRA)

Invasive: catheter angiography

Question 9

Compare CTA and MRA/MRV

Answer 9

CTA

• PROS:
  
  • good for smaller vessels
  • will show not only narrowing but also lumen characteristic (e.g. is there calcification? dissection, etc.)
  • quick!
• CONS:
  
  • must use contrast and exposes pt to radiation

MRA

• PROS:
  
  • Can visualize veins (MRV), which you can’t really do on CTA and Circle of Willis w/o contrast b/c uses flow velocity to generate image
  • can actually measure flow velocity thru vessels
  • no interference from skull b/c bone doesn’t show up
• CONS:
  
  • only good for larger vessels
  • longer aquisiton times
  • doesn’t show why a lumen is narrow (i.e. cannot show calcifications)

Question 10

What are pros/cons of convention (catheter) angiography?