Cerebrovascular Imaging

Question 1

What are the different responses to a CVA?

Answer 1

• Ischemic (85%)
  + focal, specific region of the brain
  > causes: Carotid plaque,
  embolus, spasm
• Global
  + encompasses wide areas of brain
  tissue
  > causes: decreased cardiac
  output, congenital heart failure
• Hemorrhagic (15%)
  + hypertension
  > causes: artery rupture,
  aneurysm

Question 2

What is the flip/flop perfusion pattern?

Answer 2

• Decreased flow during arterial phase
• Increased perfusion during venous phase
  -Represents collateral circulation (CVA)

Question 3

What is luxury perfusion?

Answer 3

-Increased perfusion in region of infarct
- Recent stroke, less than five days post stroke
-Due to increased oxygen demand, an increase in perfusion and decrease in metabolism

Question 4

What is diaschisis perfusion?

Answer 4

• Decrease in afferent input due to infarct
• Decrease in metabolism
• seen as decreased activity in the opposite cerebral hemisphere to the infarct
• Stroke, tumour, and trauma patients
  + With luxury perfusion you may miss the infarct therefore, look on the opposite side for diaschisis

Question 5

Subdural Hematoma imaging?

Answer 5

• Rupture of veins bridging cerebral hemisphere entering dural sinus
• Best visualized at 2 weeks post trauma
• CT preferred

Question 6

What are the characteristics of arteriovenous malformation and imaging?

Answer 6

• Congenital or acquired
• Single or multiple
• Flow and pool images

Question 7

Reasons for PET & SPECT cerebrovascular imaging?

Answer 7

• Determine patients at risk for stroke
• Indicate the likelihood of benefit from intervention
• Predict stroke recovery

Question 8

Acute CVA Interpretation?

Answer 8

• 1- 3 days post-event
• Greater sensitivity than CT
• Shows both infarcted and ischemic tissue

Question 9

Sub-acute CVA Interpretation?

Answer 9

-1-3 weeks post-event
- no decrease in activity seen
- may show increase from luxury perfusion
- Variable presentation

Question 10

Chronic CVA Interpretation?

Answer 10

• greater than a month post-event
• perfusion defect stabilize

Question 11

What is a cerebrovascular reserve and why do we assess it?

Answer 11

• Patients with underlying disease have underlying rCBF and rely on collateral circulation
• Beneficial to access the degree of taxed blood supply to asses the possibility of future stroke

Question 12

Why perform a cerebrovascular reserve study?

Answer 12

-Patients may have normal perfusion at rest, but cannot increase perfusion in response to increased demand

Question 13

What are the diseases/pathologies which could rely on collateral circulation involved in a cerebrovascular reserve study?

Answer 13

• Transient ischemic attack
• Stroke
• AVM
• Epilepsy
• Dementia

Question 14

What is a cerebrovascular reserve study?

Answer 14

-It is a pharmacological vascular stress test for the brain
-Makes use of vasodilators to assess the degree of regional cerebral vasodilatation, similar to MIBI persantine tests

Question 15

What is acetazolamide (diamox)?

Answer 15

• carbonic anhydrase inhibitor and antihypertensive
• promotes cerebral vasodilation by decreasing pH and increasing rCBF up to 30-50% at 20 min post injection
• Dose: 1 Gram

Question 16

Normal and abnormal results of a cerebrovascular reserve study?

Answer 16

• Perfusion increases in normal areas after diamox injection
• No response in areas of limited vascular reserve
  + Demonstrates relative decrease in uptake in diseased areas

Question 17

What is brain activation imaging?

Answer 17

• Use of functional stimuli to localize brain areas, visual and auditory (mapping)
• Done to assess patients post cerebral infarction to see if there is any viable tissue present
  Results: area of uptake corresponds to function in most cases