CNS PET/CT

Question 1

What are the indications of PET in neurology?

Answer 1

-Dementia- Alzheimer’s vs. others
-Epilepsy- Localization for surgery
-Parkinson’s- assessment for movement disorders

Question 2

Why PET?

Answer 2

-Allows imaging at the metabolic level
-Advantages: Improved image quality, quantification
-Improved radiopharmaceuticals: Able to label numerous compound which are physiologic compounds, and there is a variety
-Fusion of PET data with CT and now MRI

Question 3

PET and dementia

Answer 3

-Same concepts as with SPECT
-Improved images with PET
-Improved resolution and sensitivity

Question 4

Describe Amyloid imaging for Alzheimer’s

Answer 4

-It is an in vivo assessment of amyloid pathology in patients with suspected Alzheimer’s
-Must use: Radiopharmaceuticals that cross the blood brain barrier and bind to B amyloid
-Uptake correlates accurately,>90% of patients with Alzheimer’s pathology when confirmed with autopsy

Question 5

What are some B amyloid RPs?

Answer 5

-F-18 Florbetapir
-F-18 Florbetapin
-F-18 Flumtamol

Question 6

What are indications for B amyloid imaging?

Answer 6

-Confirmed cognitive impairment
-Cause of impairment remains uncertain after expert evaluation by dementia specialists
-Knowledge of the presence or absence of plaques will increase diagnostic certainty and alter patient management

Question 7

Dose characteristics of florbetapir?

Answer 7

• 370 MBq
  -Wait 30-50 min before imaging
  -10 Min acquisition

Question 8

Dose characteristics of flutemetabol?

Answer 8

-185 MBq
-Wait 60-120 mins before imaging
-10-20 min acquisition

Question 9

Dose characteristics for florbetapin?

Answer 9

-300 MBq
-45-130 min before imaging
- 20 min acquisition

Question 10

What is the normal distribution for amyloid imaging?

Answer 10

-Little to no binding in the cerebral cortex
-definitive right and left hemispheres
-grey and white matter separation is clear
-white matter lacks grey matter cortex
-Low nonspecific uptake in white matter
-clear definition of the cerebellum

Question 11

What is the difference between Ictal vs inter-ictal PET?

Answer 11

Ictal: Not as good as SPECT
-Uptake of f-18 FDG over 30-45 minutes vs couple minutes
-short half life
Inter-Ictal: Shows same decreased uptake in seizure focus as SPECT
-PET images are better
-Better resolution to demonstrate photopenic areas

Question 12

Describe PET in brain tumours and its challenges

Answer 12

-Tumours have high uptake and retention of f-18 FDG
Challenges: Normal brain has high f-18 FDG uptake as well
-Many tumours will still be visualized because FDG uptake is higher
-Uptake amount corresponds with tumour grade, low grade tumours may not be discerned from brain

Question 13

What is brain mapping in PET?

Answer 13

-Dopamine D2 cells are reduced in individuals with drug addiction
-Assess progression and improvement of brain function over time

Question 14

What are craniopharyingiomas?

Answer 14

-Uncommon, benign, cystic tumours
-Located in the craniopharyngeal duct and/or Rathkes’ cleft
-62% recurrence rate

Question 15

What is the use of PET/CT in the diagnosis of craniopharyngiomas?

Answer 15

-Uses Y-90 for localization and to confirm the cyst is not leaking
- Y-90 (B) Zr-89
-Positron emitter, coincidence photons 511 KeV