Introduction to Neuroradiology Flashcards
Name some conditions affecting the brain and spine
stroke, dementia and brain tumours
define Stroke
A stroke is when part of the brain vasculature is blocked which causes the tissue to die.
CT scans look from the…
feet up
Hypodensity on CT =
irreversible ischaemic damage
stroke on CT
- 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
- When you have a stroke you get intracellular water movement, which pushes the brain to the other side
what are CT scans based on looking at?
the density of the tissues
bone has highest density - True or False?
true - attentuates the the x-ray most = brightest on scan
what are the brighter areas lining the brain in X-ray?
- 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
why are the Subratinal spaces, middle cerebral arteries densities high?
due to clotting.
angiograms
- 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
- You can pick up abrupt blockage
why is CT preferred over MRI
- 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
Cortical ribbon being lost is sign of….
- 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.
in MRI scans and diffusion rate image.
- 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.
main disadvantage of MRI?
- MRI takes longer.
- For stroke CT is main modality of use in the UK.
perfusion CT scans
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.
perfusion grade scan
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.
core infarct - what is and why important to pick up quickly
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
what do you look for in dementia?
- 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.
T1 scan:
-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.
frontotemporal dementia:
- pattern of volume loss in frontal and temporal lobe
PET scans:
-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.
perfusion MRI:
gives idea of cerebral blood flow.
- ASL MRI is cheaper compared to PET scan.
Vascular dementia:
- 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.
Severe vascular lesions in the brain:
heart disease, diabetes, small vessel disease → lots of white matter damage due to damage in small vessels of the brain.
lacunar infarcts
Small vessels of the brain that cause little infarcts
what happens if stroke is in Thalamus
- 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.
small vessel disease
- 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
role of dura in identifying tumours?
- Imaging helps us classify tumours, how aggressive it is.
- to identify tumor is inside or outside?
-> dura helps to make this identification (called meningioma)
- to identify tumor is inside or outside?
most common tumour in brain?
glioblastoma - very aggressive as patient dies within 2 days
use of MRI for tumours
- 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
tumour that appear down the midline…
lymphoma - affects corpus collosum
lots of lesions in the brain are…
metastasis
- lung cancer, breast cancer etc. Could also be schwannoma, meningiomas, neurofibromatosis.
- Seeing where lesions are, helps you identify what they are.
