Introduction to Neuroradiology

Question 1

Name some conditions affecting the brain and spine

Answer 1

stroke, dementia and brain tumours

Question 2

define Stroke

Answer 2

A stroke is when part of the brain vasculature is blocked which causes the tissue to die.

Question 3

CT scans look from the…

Answer 3

feet up

Question 4

Hypodensity on CT =

Answer 4

irreversible ischaemic damage

Question 5

stroke on CT

Answer 5

• Lateral ventricles (black on CT) are squashed, swelled.
  
  • When you have a stroke you get intracellular water movement, which pushes the brain to the other side
    -not always obvious though

Question 6

what are CT scans based on looking at?

Answer 6

the density of the tissues

Question 7

bone has highest density - True or False?

Answer 7

true - attentuates the the x-ray most = brightest on scan

Question 8

what are the brighter areas lining the brain in X-ray?

Answer 8

• The cerebral cortex.
  -It has more cells than white matter, so attenuates the X-rays.
  
  • More blood supply, iron (attenuates the x-ray).
• Water attenuates the x-ray released hence why it looks black on CT scans

Question 9

why are the Subratinal spaces, middle cerebral arteries densities high?

Answer 9

due to clotting.

Question 10

angiograms

Answer 10

• give you contrast and you look at how the contrast is getting into the vessels.
  
  • You can pick up abrupt blockage
    → needle is passed in groin and wire is passed up to the brain where the clot is located. e.g middle cerebral artery.
  • Blockage is opened up by pulling clot out.
  • Patient ends up with a smaller stroke, as most of cerebral artery was opened up

Question 11

why is CT preferred over MRI

Answer 11

• CT is good at picking up blood, it’s easier to see.
  
  • Could also be calcification but due to acute presentations.
  • It causes swelling and pushes ventricles

Question 12

Cortical ribbon being lost is sign of….

Answer 12

• early stroke.
  -This is because the brain is getting more swollen and more filled with water. Irreversible
• Angiogram gives you further contrast images.
  ->Middle cerebral artery stroke.

Question 13

in MRI scans and diffusion rate image.

Answer 13

• bone less attenuated than on CT
  
  • Sensitised to diffusion within different brain structures.
  • In ventricles diffusion is black, so no diffusion restriction.
  • there’s free diffusion of water but inside a stroke area, you have intracellular movement of water which causes diffusion restriction hence it appears white on MRI.

Question 14

main disadvantage of MRI?

Answer 14

• MRI takes longer.
  
  • For stroke CT is main modality of use in the UK.

Question 15

perfusion CT scans

Answer 15

you give contrast and you get a lot of images in quick succession. what we see is whats happening to the contrast. this tells you which areas are less perfused, at risk, have a stroke.

Question 16

perfusion grade scan

Answer 16

mean transit time it takes to get from arterial to venous system is increased in a larger area of the brain (bigger than stroke area).
=this means the whole area of brain is at risk.

Question 17

core infarct - what is and why important to pick up quickly

Answer 17

definitive risk of stroke
- area of risk is important to pick up so we know which area to save, how much of the brain is left, other wise there’s no point

Question 18

what do you look for in dementia?

Answer 18

• volume loss.
• As alzheimers progresses, volume of hippocampus (medial temporal lobe) is lost.
• Little can be done at later stage, so must be picked up earlier. Future work must be done.

Question 19

T1 scan:

Answer 19

-cortex is grey, white matter is actually white. Good for anatomy of the brain.
- widened sulci seen in alzheimer’s patients.
- different patterns of volume loss seen.
- gyrus is thinner etc.

Question 20

frontotemporal dementia:

Answer 20

• pattern of volume loss in frontal and temporal lobe

Question 21

PET scans:

Answer 21

-radiotracers such as glucose, amyloids (to pick up pathology earlier).
- In alzheimer’s disease, metabolic areas are fewer than in normal.
- In FTD less metabolic areas seen too especially in temporal lobes and also corresponding volume loss.

Question 22

perfusion MRI:

Answer 22

gives idea of cerebral blood flow.
- ASL MRI is cheaper compared to PET scan.

Question 23

Vascular dementia:

Answer 23

• white matter changes in the ventricles. Flair (T2) scan, white matter is grey and grey matter is white.
  
  • Normally, fluid is bright, but fluid could look dark if special sequence called flair is used where fluid is supressed.

Question 24

Severe vascular lesions in the brain:

Answer 24

heart disease, diabetes, small vessel disease → lots of white matter damage due to damage in small vessels of the brain.

Question 25

lacunar infarcts

Answer 25

Small vessels of the brain that cause little infarcts

Question 26

what happens if stroke is in Thalamus

Answer 26

• arries lots of white matter fibres (huge relay centre), so stroke here leads to cognitive impairment.
  
  • so vascular dementia is step-wise as infarcts gradually affect cognitive aspects.

Question 27

small vessel disease

Answer 27

• vessels are few microns in size and can be seen in contrast imaging.
• in older people with dementia, the vessels look shrivelled up = early sign of SVD

Question 28

role of dura in identifying tumours?

Answer 28

• Imaging helps us classify tumours, how aggressive it is.
  
  • to identify tumor is inside or outside?
    -> dura helps to make this identification (called meningioma)

Question 29

most common tumour in brain?

Answer 29

glioblastoma - very aggressive as patient dies within 2 days

Question 30

use of MRI for tumours

Answer 30

• used to delineate the tumour and surgeons to resect (take it out through surgery) enhancing bits.
  
  • Difficult to tell the spread of the tumour on the MRI

Question 31

tumour that appear down the midline…

Answer 31

lymphoma - affects corpus collosum

Question 32

lots of lesions in the brain are…

Answer 32

metastasis
- lung cancer, breast cancer etc. Could also be schwannoma, meningiomas, neurofibromatosis.
- Seeing where lesions are, helps you identify what they are.