Imaging of CNS

Question 1

use of ultrasound in neurology?

Answer 1

• mostly for neonates (fontanelles act as an acoustic window)
• used in adults to measure flow in middle cerebral artery

Question 2

blood oxygenation level dependant (BOLD) imaging purpose?

Answer 2

fMRI (functional mri) to perform tractography. when an area of the cortex becomes active, there is an initial acute increase in CO2 and deoxygenated Hb levels (as O2 gets used in tissue). This is followed by a surge in oxygenated hemoglobin —>surge is detected by fMRI

Question 3

compare/contract SPECT vs PET

Answer 3

both used in combo with MRI to provide functional and metabolic information.

SPECT has less spacial contrast and resolution than PET, but it’s cheaper.

Question 4

what are the advantages of T1 weighted MRI images?

Answer 4

anatomical resolution +++

• good differentiation between white and gray matter
• ability to identify areas of cortical thickening as in migrational disorders (ex. grey matter heterotopia, focal cortical dysplasia)

Question 5

what are the advantages of T2-weighted MRI images?

Answer 5

Water sensitive, best for highlighting physiological problems, such as pathological changes in white matter.

• abnormal metabolism of normal cells (inflammation leading to oedema)
• abnormal cells

Question 6

MRI can be most useful for imaging which area of the Limbic system? perhaps in consideration of surgery for a neurological disease….

Answer 6

Hippocampal sclerosis–>most common cause of temporal lobe focal epilepsy (esp CA1 region)

Question 7

what are watershed strokes?

Answer 7

occur between vascular territories (basilar artery, posterior inferior cerebellar artery, anterior spinal artery branches, posterior spinal artery branches), typically due to hypoperfusion

Question 8

best modes of imaging intracranial veins and dural sinuses?

Answer 8

digital subtraction angiography (DSA), CT venography (CTV), MR venography (MRV)