Topic 3 - structural imaging Flashcards

1
Q

what are the advantages of structural imaging

A

diagnosis (if visible - not common in concussion)
in vivo anatomy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

why is CT the structural imaging of choice

A

speed, availbility, lower cost, and limited contraindications

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how does CT work

A

rotating xray detectors that measure the reduction in xrays and process detector data into grey scale images

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is CT sensitive to (easily see)

A

facial fractures
hemorrhage in all brain spaces
(layers of scans across the brain)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

how many CT scans reveal an abnormality in concussion workups

A

~3%
<1% require neurosurgical intervention

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the canadian CT head rule

A

CT only required for patients with minor head injuires that have other red flag symptom(s)
- allows for much fewer scans because they are not needed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

why is MRI sometimes useful

A

doesn’t use ionising radiation
role in the acute setting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are the downsides of MRI

A

rarely identifies a concussion
- used with more severe TBIs/soft tissue damage but even then it’s tough to differentiate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how does an MRI work

A

uses a strong magentic field and radiofrequency pulse to excite spinning protons in tissues to create imaging with different contrasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

why does MRI work in humans

A

water content (water molecules have a slight positive and slight negative)
- can detect changes in water movement based on the spin put on the molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what does DTI look for

A

expected water mvmt in the brain
- unexpected = probable damage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

why does DTI work

A
  • water molecules move in the brain
  • water motion can be used to infer about neuroanatomy
  • dominated by static anatomy and less influenced by physiology
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is isotropic diffusion

A

water that is free to move in any direction
(lake)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is anisotropic diffusion

A

water that moves along one axis but not others
(river)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how is anisotropic used in the brain to estimate axonal organisation

A

water moves more easily along the axonal bundles rather than perpendicular to the bundles (fewer obstacles to prevent mvmt)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is fractional anisotropy

A

how directional the diffusion of water is and reflects fibre organisation
0-1 scale
large number (close to 1) = high diffusion anisotropy (water is constrained and moving along the axon)

17
Q

what is the change to fractional anisotropy after concussion

A

lower number than expected (<1)
indicates axonal damage

18
Q

what is mean diffusivity

A

general freedom of water mvmt irrespective of direction and provides a notion of how much water is present with a given voxel
doesn’t say what’s happening, just that something is happening

19
Q

how is MD quantified

A

open scale
larger numbers = increase in the amount of water in that part of the white matter tract
should be consistent across the whole axon

20
Q

what happens to MD after a structural injury

A

increase in MD score
- could be caused by swelling, edema, demyelination, decreased plasma/EC matrix viscosity