CNS

Question 1

Two main tracers sued for brain SPECT

Answer 1

Tc HMPAO (hexamethylpropyleneamine oxime); Tc ECD (ethyl cysteinate dimer)

Question 2

Difference in kinetics of HMPAO an ECD

Answer 2

HMPAO washout is fast, ECD washout is slow

Question 3

What are the similarities between HMPAO and ECD?

Answer 3

neutral and lipophilic (cross BBB) and both accumulate in the cortex proportional to blood flow

Question 4

distribution of HMPAO

Answer 4

uptake favors the frontal lobe, thalamus, and cerebellum

Question 5

CNS radiotracer with uptake in the frontal lobe, thalamus, and cerebellum

Answer 5

HMPAO

Question 6

distribution of ECD

Answer 6

parietal and occipital lobes

Question 7

CNS radiotracer with uptake in the parietal and occipital lobes

Answer 7

ECD

Question 8

Radiotracer used to evaluate cerebral vascular flow, but not taken up by brain parenchyma

Answer 8

Tc DTPA. does NOT cross the BBB

Question 9

for imaging of a seizure focus, when does the HMPAO or ECD need to be injected?

Answer 9

30 seconds of the seizure to get a good study

Question 10

Answer 10

Question 11

Answer 11

Alzheimer disease

Question 12

Answer 12

corticobasal degeneration

Question 13

Answer 13

Question 14

Answer 14

frontotemporal dementia

Question 15

Answer 15

Question 16

Answer 16

frontotemporal dementia

Question 17

Answer 17

Question 18

Answer 18

lewy body dementia

Question 19

Answer 19

Question 20

Answer 20

Question 21

Answer 21

If the frontal lobe or internal capsule is involved, hypometabolism in the contralateral cerebellum may be seen due to crossed cerebrocerebellar diaschisis

Question 22

Answer 22

misregistration due to patient motion

Question 23

Answer 23

atrophy –> sulcal widening –> artifact of hypometabolism (pitfall for misdiagnosis of neurodegenerative disorder)

Question 24

Which radiopharmaceutical used in the evaluation of brain death does not cross the blood–brain barrier and as such requires an adequate radiotracer bolus?

Answer 24

DTPA

Question 25

Answer 25

ECD SPECT of frontal dementia

Question 26

Answer 26

SPECT ECD of Alzheimer disease (decreased uptake in the posterior temporal lobes)

Question 27

Answer 27

Tc-99m DTPA brain death study, demonstrates hot nose sign [https://radiopaedia.org/articles/brain-death-2?lang=us](https://radiopaedia.org/articles/brain-death-2?lang=us)

Question 28

Answer 28

Question 29

are interictal SPECT or PET superior for detecting complex partial seizures?

Answer 29

PET interictal FDG-PET is very sensitive (80%) in localizing refractory complex partial seizures, which typically originate from the temporal lobe. Interictal SPECT or PET is frequently used to increase the specificity of the findings seen on ictal study.

Question 30

Which of the following procedures is the most sensitive in diagnosing seizures of extratemporal origin?

Answer 30

Ictal perfusion SPECT with ECD or HMPAO is the most sensitive when extratemporal seizure focus is expected. Interictal hypometabolism and hypoperfusion are uncommon with extratemporal epilepsy, and interictal SPECT or PET is not ideal for its evaluation. For ictal studies, the patients are taken off their seizure medications, admitted, and continuously monitored for the onset of seizure. The radiopharmaceutical is kept at the bedside until the seizure occurs. Once seizure is identified, radiotracer is injected during or within 30 seconds after the completion of the seizure.

Question 31

What is responsible for poor diagnostic utility of F-18 FDG during the ictal phase?

Answer 31

poor temporal resolution FDG uptake with the brain is gradual with 95% of the peak uptake occurring around 35 minutes. This is significantly longer than an average seizure focus duration of 1 to 2 minutes. This **causes overlap of increased uptake from ictal phase and relatively decreased uptake during interictal/postictal phases**. Because of this lower temporal resolution, F-18 FDG-PET cannot be performed during the ictal phase. **Interictal FDG-PET is most helpful in patients with complex partial seizures**, which are frequently **secondary to mesial temporal lobe epilepsy**. Compared to SPECT, FDG-PET has higher spatial resolution and lower background activity.

Question 32

A = interictal B = ictal C = interictal PET patient with a clinical history of intractable complex partial seizures. What is your conclusion?

Answer 32

Mesial temporal sclerosis The coronal ictal SPECT–CT image (B) demonstrates increased perfusion to the right temporal lobe compared to the left (arrow). Coronal interictal SPECT–CT (A) and axial F-18 FDG-PET (C) images demonstrate relatively decreased perfusion and metabolism to the right temporal lobe compared to the left, respectively (arrowheads). These findings are most compatible with seizure focus within the right temporal lobe likely from mesial temporal sclerosis. Glioblastoma multiforme is a high-grade primary brain malignancy that would demonstrate increased perfusion and metabolism.

Question 33

imaging agent?

Answer 33

I-123 ioflupane (DaTscan) Three-hour delayed axial images acquired after IV administration of I-123 ioflupane (DaTscan) demonstrate symmetric intense striatal activity with well-delineated borders consistent with normal examination. A normal DaTscan in a patient with movement disorder would suggest essential tremor.

Question 34

what radiopharmaceutical would be most helpful in differentiating between Alzheimer disease and frontotemporal dementia?

Answer 34

F18- flobetapir (amyvid) Beta amyloid imaging would be most helpful in differentiating AD from FTD as it would be markedly abnormal in AD but normal in FTD. The first FDA-approved and most widely used radiotracer for in vivo identification of beta amyloid (Aβ) plaques was F-18 florbetapir (Amyvid). Other FDG-approved agents for imaging beta amyloid include F-18 florbetaben (Neuraceq) and F-18 flutemetamol (Vizamyl). A negative beta amyloid imaging PET scan would show predominant white matter retention, while positive scan would display increasing gray matter retention. Amyloid imaging demonstrates the earliest abnormality in AD, even before F-18 FDG-PET is abnormal.

Question 35

ioflupane critical organ

Answer 35

bladder

Question 36

ioflupane mechanism of action

Answer 36

pre-synapic dopamine transporter

Question 37

should you discontinue L-dopa prior to a DAT scan?

Answer 37

Continue L-dopa!

Question 38

can patients be on cocaine prior to a DaT scan?

Answer 38

No - ioflupane and cocaine both bind to pre-synaptic dopamine transporter protein

Question 39

Answer 39

normal scan Occipital lobe uptake ONLY = closed eyes

Question 40

what is the significance of testicular uptake?

Answer 40

higher chance of CNS metastasis

Question 41

important additional projections in a brain death study

Answer 41

picture of the injection site (make sure that it was actually injected) image of the abdomen to check for normal biodistribution (aka uptake in the liver)

Question 42

Answer 42

In-111 DTPA CSF leak study positive with CSF leaking out the nose

Question 43

depression (TBI) can mimic what patten of dementia on SPECT or FDG-PET?

Answer 43

Fronto-temporal Dementia

Question 44

what part of the brain is classically spared with neurodegenerative disordes?

Answer 44

The motor strip