SPECT imaging in cerebrovascular disease

1
SPECT imaging in cerebrovascular disease

• Measurement of regional cerebral blood flow
  (rCBF)
• Sensitive indicator of perfusion
• Diagnosis and prognosis of cerebro-vascular
  disease
• Tc-99m HMPAO brain SPECT

2
SPECT perfusion image

• Acute brain ischemia
• Perfusion defects after resolution of TIA
• Cerebral infarction
• Delayed ischemic deficits after SAH
• Determine pathophysiological mechanisms of stroke
• Monitor medical and surgical therapies

3
Normal tracer uptake

• Symmetric distribution
• Higher radioactivity gray matter, basal
  ganglion, occipital cortex, cerebellum
• Lower radioactivity white matter, ventricles

4
Abnormal tracer uptake

• Absent
• infarction, trauma, surgical resection
• Reduced
• ischemia, dementia, depression,
  seizure(interictal)
• Increased
• luxury perfusion, seizure(ictal)

5
Stroke 1

• SPECT superior to CT/MRI in detecting cerebral
  ischemiaearlier larger
• rCBF imaging effective in acute phase, less
  sensitive in the subacute phase
• -8h SPECT-80 CT-20
• -72h SPECTCT/MRI

6
Stroke 2

• False negative lacunar infarctions, luxury
  perfusion(520 days)
• Crossed-cerebellar diaschisis continues even
  during luxury perfusion
• Classifying stroke subtypes for treatment,
  recurrence, recovery and mortality

7
Cerebrovascular reserve 1

• Increase the sensitivity of detecting perfusion
  failure
• Assess the need for acute interventions following
  stroke or the risk status for secondary strokes
• Useful in detecting ischemic sequelae in TIA,
  stroke, AVM, SAH pt

8
Cerebrovascular reserve 2

• Brain stress test vasodilatory response to CO2
  or acetazolamide
• --compare resting images and vasodilated images
  (2030min after acetazolamide injection)
• --diseased or at-risk areas show little or
  no response

9
Prognostication

• SPECT/CT volume defect sizeslarger ratios with
  better outcomes
• Flow index, density of counts/volume of defect on
  SPECT correlates clinical recovery at 1 month
• IMP uptake delayed(4h)/early(lt1h)larger with
  more viable brain tissue and better clinical
  outcomes

10
Transient Ischemic Attacks (TIA)

• Severity of persistent hypoperfusion
• Response of an ischemic area to medical or
  surgical intervention
• Identify pt at high risk for early stroke
  following a TIA (persistent reduction in rCBF of
  gt30 with high risk of subsequent infarction)
• Sensitivity declines with time, (24h60,
  1wk40) can be enhanced by acetazolamide stress
  test

11
Monitoring therapies

• Determine pathophysiology after successful
  therapy
• In thrombolytic and anticoagulant treatments,
  changes in artery patency and recanalization can
  be evaluated.

12
Subarachnoid hemorrhage (SAH)

• Provide early evidence of cerebral ischemia due
  to vasospasm after SAH
• Vasospasm decrease rCBF, increase cerebral blood
  volume
• Delayed cerebral ischemia with vasospasmfactors
  of recurrent hemorrhage in the morbidity or
  mortality of SAH

13
Arteriovenous malformation (AVM) 1

• Complications
• Intracerebral/intraventricular bleeding
• Seizure
• Intracerebral steal due to AV shuntingproduce
  ischemia
• Cerebrovascular reserve is prognostic for
  postoperative outcome

14
Arteriovenous malformation (AVM) 2

• Reserve categorization
• Normal
• Increased (pathological vasodilatation)
• hyper-responsiveness to acetazolamide in
  regions of steal in the resting state
• Failed (no vasodilatory reserve in steal areas)

15
Others

• Vascular diseasemigraine, vascular dementia,
  transient global amnesia
• Alzheimers disease
• Head injury
• Epilepsy
• Brain death