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PSYC210 > MRI - Olivia Harrison > Flashcards

MRI - Olivia Harrison Flashcards

1
Q

dendrites

A

openings for other cells to communicate

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2
Q

cell body

A

powerhouse, motor of the cell, energy production

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3
Q

axon

A

neurones main way of talking to other cells in other parts of the brain

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4
Q

myelin

A

fatty substance that covers the axons

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5
Q

axon terminals

A

branch onto other dendrites

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6
Q

grey matter

A

grey part of the brain, in a ribbon around the edge of the brain where the cell body sit

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7
Q

white matter

A

axons make up white matter, long projection, myelin makes that projection fast

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8
Q

what is the main difference in human and animal brain

A

animals is much smoother their not as deep folds, don’t have as many folds

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9
Q

what is cerebrospinal fluid important for

A

cushioning the brain, delivering nutrients and taking away waste products

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10
Q

Where and what are the ventricles

A

the holes located in the middle of the brain

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11
Q

T1-weighted structural MRI

A

very common, can see white matter grey matter and CSF
provides information about the relaxation times of tissues. It is widely used in clinical practice to assess the structural characteristics of various organs and tissues.

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12
Q

T2-weighted structural MRI

A

colours are flipped, highlights CSF
provides information about the relaxation times of tissues. It is commonly used in clinical practice to evaluate the structural characteristics of various organs and tissues.

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13
Q

Proton Density structural MRI

A

provides information about the density or concentration of protons in tissues

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14
Q

what are the cons of getting a really good quality image

A

more time consuming, longer patient has to lie completely still

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15
Q

FLAIR

A

specific type of magnetic resonance imaging (MRI) sequence that is particularly useful in assessing certain brain pathologies. It is a T2-weighted sequence that suppresses the signal from fluids, such as cerebrospinal fluid (CSF), while maintaining good contrast for other tissues.

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16
Q

WM nulled

A

specific type of magnetic resonance imaging (MRI) sequence that is designed to suppress the signal from white matter tissue in the brain. It is often used in neuroimaging research to selectively visualize and study other brain structures or pathologies without the interference of white matter signals.

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17
Q

Double Inversion Recovery (DIR)

A

ability to provide improved contrast and better visualization of gray matter structures. It allows for enhanced differentiation between different brain tissues, including gray matter, white matter, and CSF. This can be particularly helpful in detecting subtle gray matter lesions, assessing brain atrophy, and studying neurodegenerative disorders.

higher resolution

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18
Q

what MRI are good for highlighting certain tissues, visualising lessons/pathologies or nuclei and measuring issue types indirectly via magnetic properties

A

FLAIR
WM nulled
Double Inversion Recovery (DIR)

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19
Q

Structural MRI

A

T1-weighted, T2-weighted and Proton Density

20
Q

Structural MRI (2)

A

FLAIR, WM Mulled and Double Inversion Recovery (DIR)

21
Q

Structural MRI (3)

A

SWI/QSI, MT and Veno/Angio-grams

22
Q

Structural MRI Analysis

A

Quantify tissue volumes and structure shape and size
tissue types - GM,WM, CSF
cortical surfaces and thickness
sub-cortical structure and shape
local GM changes

23
Q

Example of a research question based on structural MRI

A

how is the volume of grey matter related to age?
hypothesis: older individuals will have less grey matter as a proportion of head size
null hypothesis: older individuals will not demonstrate any differences in grey matter

24
Q

Structural MRI limitations

A
  • does not measure tissue type (GM,WM,CSF) directly
  • the absolute values are not the same across scanners or sessions
  • measurement is in the order of millimetres - thousands of underlying cells per 3-dimensional pixel
  • does not always distinguish bone from air
  • contrast can be poor/variable in subcortical (deep) brain regions
  • a single sequence does not show all pathologies
  • lots of artefacts and noise
25
Q

Structural MRI complimentary techniques

A
  • CT (with/without contrast) (shows bones/membranes/vessels/tumours)
  • Histology (shows microstructure)
26
Q

Histology

A

postmortem brain-staining for something specific

27
Q

What does diffusion MRI measure

A

measures the direction of WM fibres in the brain
based on movement (diffusion) of water
restricted in some directions than others which gives more information about axon directions in white matter

28
Q

in which direction is there more movement in axons

A

more movement lengthways rather than widthways, water can diffuse along but is hard to diffuse sideways

29
Q

Differences between structural and diffusion MRI

A

structural takes 5 minutes to acquire one image
diffusion takes lots of fast images (one every 1-3 secs) for a total of 5 minutes (100-300+ images)
diffusion has a lower resolution (1-3mm) to make scanning faster compared to structural with (<1mm)

30
Q

Corpus Callosum

A

the highway between the two hemispheres, a dense bundle of white matter

31
Q

3 ways to look at the brain

A

dorsal - looking from the top
sagittal - side on
coronal - front on

32
Q

Corpus Callosum tensors

A

pointier and in the same direction of the diffusion then there is more diffusion
not as pointy and have less diffusion in those areas, which might mean fewer axons or don’t have strong boundaries

33
Q

what kind of tensors would have a higher mean diffusivity

A

the wider ones

34
Q

White Matter tract tracing

A

Fit tensors and trace tracks, follow the tracks and see where we end up

35
Q

2 types of white matter tract tracing

A

tractography traces connections via local directions
probabilistic tractography where the different axons might be projecting to

36
Q

Yang et al. 2017 white matter integrity

A

greater mean diffusivity in patients with trigeminal neuralgia (type of headache when cranial nerves are hypotensive) compared to healthy controls

37
Q

Example research question based on Diffusion MRI

A

how is the mean diffusivity of the corpus callous related to age?
hypothesis: older individuals will have greater mean diffusivity than younger individuals, reflecting age-related decline in structural integrity
null hypothesis: there will be no relationship between age and mean diffusivity of the corpus callous

38
Q

Diffusion MRI limitations

A
  • does not measure axon size/density directly
  • does not measure single fibres (only average groups)
  • more difficult to deal with crossing/kissing fibres
  • more difficult to do in pulsatile regions (brainstem)
  • more restricted by scanner hardware
  • sensitive to fast imaging artefacts
39
Q

Diffusion MRI complimentary techniques

A

Tracer studies (invisible fibres) - inject dye into specific neurone and see where that projection goes on a postmortem brain

histology (myelin/axon dimensions/gila) - really look at structure

40
Q

The Haemodynamic Response

A

When neurons in the brain become active during cognitive or sensory processing, they require an increased supply of oxygen and nutrients to meet their metabolic demands. The hemodynamic response is the complex chain of events that ensures this increased blood flow and oxygen delivery to the activated brain regions.

41
Q

FMRI experiment word generation

A

noun is presented and verb is generated from the word, ball - catch etc

42
Q

FMRI experiment word shadowing

A

just has to repeat the word that is presented, swim - just repeats swim verb presented verb repeated

43
Q

FMRI experiment null event

A

baseline might change depending on different factors which can determine the baseline - we compare the word events to these
- contains a visual component
- no word component

44
Q

Results of functional MRI

A

compare to see where in the brain is actually trying to produce a word rather than just repeating, showing what is in the word generation and not in word showing, found Broca’s area, speech production and fluency

45
Q

Broca’s area

A

contributes to speech production and fluency

46
Q

Functional MRI limitations

A
  • does not measure electrical activity
  • does not measure metabolic activity or neurons
  • does measure changes in blood oxygen levels resulting from the electrical and metabolic activity of active neutrons
  • BOLD-FMRI is qualitative (change from baseline important not baseline itself, or absolute numbers)
  • sensitive to fast imaging artefacts (like diffusion)
47
Q

complimentary techniques for functional MRI

A

Positron Emission Tomography (PET) - inject radioactive glucose, go around the brain and lock onto cells that are more active and radiate back, only can do it once and shouldn’t be to often
- measures brain metabolism directly
- can use radioactive tracers
- slower temporal resolutions vs FMRI
- reduced spacial resolution vs FMRI

Electroencephalography (EEG)
- measures electrical brain activity directly
- much faster temporal resolution vs FMRI (milliseconds)
- reduced spatial resolution vs FMRI
very good at measuring deep structures in the brain
can’t localise where it comes from

PSYC210 (3 decks)

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