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Whole Brain Neuroscience > Neuroimaging > Flashcards

Neuroimaging Flashcards

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1
Q

What is the purpose of structural neuroimaging?

A

To study the architecture of the brain and detect any distortions to its structure.

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2
Q

Which materials appear hypodense (dark) on a CT scan, and why?

A

Air and fluid because they are passed through easily by x-rays.

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3
Q

Which materials appear hyperdense (bright) on a CT scan, and why?

A

Bone and metal because they are dense, so x-rays cannot easily pass through.

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4
Q

What does CT stand for?

A

Computed tomography.

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5
Q

How does a CT scan work?

A

X-rays create 2D images.

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6
Q

Why is CT useful for detecting acute haemorrhage?

A

Haemorrhage appear hyperdense due to the x-ray absorption of iron within the haemoglobin of the blood.

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7
Q

What does MRI stand for?

A

Magnetic resonance imaging.

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8
Q

How does MRI work?

A

A magnetic field and radiofrequency pulses cause hydrogen atoms within the tissues to align and then relax.
The energy emitted by the hydrogen nuclei as they realign is detected and reconstructed into 2D images.
The 2D images are displayed as contiguous slices.

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9
Q

Why is MRI the preferred structural neuroimaging modality over CT?

A

MRI provides much higher resolution images of soft tissue.

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10
Q

What is the purpose of T1-weighted MRI images?

A

It uses specific radiofrequency pulses to highlight hydrogen atoms in more hydrophobic environments, such as myelin.

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11
Q

How does white matter appear in T1-weighted images?

A

Bright/hyperintense.

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12
Q

How does grey matter appear in T1-weighted images?

A

Dark/hypointense.

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13
Q

How do lesions appear in T1-weighted images?

A

Dark/hypointense.

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14
Q

What is the purpose of T2-weighted MRI images?

A

It uses specific radiofrequency pulses to highlight structures containing water rather than lipids.

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15
Q

How does grey matter in T2-weighted images?

A

Bright/hyperintense.

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16
Q

How does white matter appear in T2-weighted images?

A

Dark/hypointense.

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17
Q

How do lesions appear in T2-weighted images?

A

Bright/hyperintense.

18
Q

What does MRS stand for?

A

Magnetic resonance spectroscopy.

19
Q

How is data from MRS represented?

A

As a waveform with peaks representing the presence and concentration of various metabolites in brain tissue.

20
Q

Why is MRS frequently used in neuro-oncology?

A

Neoplastic tissue is metabolically different from normal brain tissue.

21
Q

How can MRS be used clinically in neurodegenerative disorders?

A

Neurodegenerative disorders can cause abnormal ratios of certain brain metabolites.

22
Q

What does DTI stand for?

A

Diffusion tensor imaging.

23
Q

What is the purpose of DTI?

A

To assess the integrity of subcortical white matter pathways.

24
Q

What happens to subcortical white matter pathways when somebody has a destructive lesion (e.g. stroke) or a condition like Alzheimer’s?

A

They are disrupted or degraded.

25
Q

How does DTI work?

A

It combines voxel-based measurements of diffusion with information about the directionality or vector of restricted diffusion to create probabilistic maps of expected locations of white matter pathways.

26
Q

Why are fMRI and DTI important tools in neuropsychiatric research?

A

They provide information on the functional and structural connectivity of neural circuits involved in a variety of neurocognitive tasks.

27
Q

What does PET stand for?

A

Positron emission tomography.

28
Q

What does SPECT stand for?

A

Single photon emission computed tomography.

29
Q

What is a tracer?

A

A radioisotope that is coupled to a molecule of interest.

30
Q

How does PET work?

A

A tracer is injected into the bloodstream.
It crosses the BBB into the brain.
As the radioisotope decays, it emits radioactive particles (positrons) that can be detected.
This allows areas of the brain in which the tracer has accumulated to be mapped.

31
Q

Name the two most commonly used radioisotopes.

A

(18F) fluorine.
(11C) carbon.

32
Q

What is the most commonly used PET tracer?

A

18F-fluorodeoxyglucose (FDG).

33
Q

How does FDG work?

A

It is a radioactive analogue of glucose, so it is taken up and utilised by metabolically active neurons and other cells.

34
Q

What is the purpose of FDG-PET?

A

To provide a map of glucose utilisation of the brain.

35
Q

How do neurodegenerative diseases present in an FDG-PET?

A

They result in a reduced FDG-PET signal because they produce patterns of hypometabolism.

36
Q

Name the two abnormal proteins that accumulate in Alzheimer’s.

A

Beta-amyloid.
Tau.

37
Q

Why is 11C-Pittsburgh Compound-B (PiB) used as a tracer to detect Alzheimer’s?

A

The radioisotope carbon-11 is coupled to a molecule that binds to beta-amyloid.

38
Q

What is the purpose of SPECT?

A

To detect cerebral blood flow.

39
Q

Which radiomolecule is used in SPECT?

A

Technetium.

40
Q

How does SPECT work?

A

A radiomolecule travels via the bloodstream to well-perfused areas of the brain.
It emits gamma rays as it decays.
This allows area of increased and decreased perfusion to be mapped.

41
Q

How does dementia present in SPECT?

A

There is reduced blood flow to atrophic regions.

42
Q

How can Parkinson’s be detected using SPECT?

A

In Parkinson’s, there is a decreased presence of dopamine transporters (DaTs) in the striatum and basal ganglia.
Ioflupane-123 can be taken up by DaTs.
There will be reduced tracer uptake in the striatum and basal ganglia.

Whole Brain Neuroscience (3 decks)

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