Cerebrovascular

Question 1

radiotracers

Answer 1

Tc 99 DTPA; HMPAO, ECD

Question 2

Tc99 DTPA

Answer 2

perfusion agent; does not cross BBB

Question 3

Tc99m HMPAO/ECD

Answer 3

perfusion agents that cross BBB

ECD is enzymatically modified, taken up by cells

HMPAO protonated to be trapped

ECD preferred for brain imaging; and has rapid blood pool clearance, better shelf life, more accurate characterization of perfusion

Question 4

brain death study imaging

Answer 4

Tc 99 pertechnetate or DTPA

Question 5

hot nose sign

Answer 5

increased collateral flow in brain death and in nose

Question 6

evaluating cerebral perfusion NM agent

Answer 6

acetazolamide challenge (1g)

increases blood flow

Question 7

seizure imaging

Answer 7

hypermetabolic during seizure (ictal) and hypometabolic (inter-ictal)

image with Tc 99 HMPAO or ECD

Question 8

dementia imaging

Answer 8

Alzheimer: symmetrically decreased SPECT in posterior temporal/parietal lobes

Lewy body: alzheimer + occipital calcarine cortex

Multi-infarct dementia: asymmetric foci of decreased metabolism

Pick: decreased fronal/anterior temporal lobe uptake

Question 9

brain tumor recurrence vs radiation necrosis

Answer 9

Thallium 201: accumulates in malignant gliomas, not in granulation tissue; grade in comparison to scalp activities

F-18 FDG PET: dual phase; early/delayed imaging

Question 10

crossed cerebellar diaschisis

Answer 10

decreased perfusion in contralateral cerebellar hemisphere due to perceived interruption of corticopontine-cerebellar pathways