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

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

Normal tracer uptake Symmetric distribution Higher radioactivity: gray matter, basal ganglion, occipital cortex, cerebellum Lower radioactivity: white matter, ventricles

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

Stroke 1 SPECT: superior to CT/MRI in detecting cerebral ischemia — earlier & larger rCBF imaging: effective in acute phase, less sensitive in the subacute phase -8h: SPECT-80%; CT-20% -72h: SPECT=CT/MRI

Stroke 2 False negative: lacunar infarctions, luxury perfusion(5~20 days) Crossed-cerebellar diaschisis: continues even during luxury perfusion Classifying stroke subtypes for treatment, recurrence, recovery and mortality

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 p ’ t

Cerebrovascular reserve 2 Brain stress test: vasodilatory response to CO 2 or acetazolamide --compare resting images and vasodilated images (20~30min after acetazolamide injection) --diseased or at-risk areas show little or no response

Prognostication SPECT/CT volume defect sizes — larger 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(<1h) — larger with more viable brain tissue and better clinical outcomes

Transient Ischemic Attacks (TIA) Severity of persistent hypoperfusion Response of an ischemic area to medical or surgical intervention Identify p ’ t at high risk for early stroke following a TIA (persistent reduction in rCBF of >30% with high risk of subsequent infarction) Sensitivity declines with time, (24h — 60%, 1wk — 40%) can be enhanced by acetazolamide stress test

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

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 vasospasm — factors of recurrent hemorrhage in the morbidity or mortality of SAH

Arteriovenous malformation (AVM) 1 Complications Intracerebral/intraventricular bleeding Seizure Intracerebral steal due to AV shunting — produce ischemia Cerebrovascular reserve is prognostic for postoperative outcome

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)

Others Vascular disease — migraine, vascular dementia, transient global amnesia Alzheimer ’ s disease Head injury Epilepsy Brain death