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Fundamentals of neuroscience > Imaging the NS 2 (anatomy) > Flashcards

Imaging the NS 2 (anatomy) Flashcards

1
Q

What is structural imaging?

A
  • Measures changes in organisation/size
  • 2D &3D images
  • CT, MRI
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2
Q

What is funcitonal imaging?

A
  • Measures physiological activities
  • Blood flow, metabolism, NT function
  • fMRI, PET
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3
Q

What does CT and CAT stand for?

A

CT = Computerised Tomography

CAT = Computerised Axial Tomography

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4
Q

How does a CT scan work?

A
  • Uses X-rays
  • X-ray beam rotates 360 degrees around the patient
  • E-ray detector rotates oppposite to the X-ray source
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5
Q

How do the X-rays used in CT scans produce an image?

A

As X-rays travel through the body they’re absorbed in different amounts by different tissues

Higher DENSITY tissue create whiter img than other tissues against the black background of the film

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6
Q

What are CT scans used for?

A

Good for bones, haemorrhages & blood vessels (with contrast)

Often used on the spine

Important in emergency diagnosis e.g. stroke and tumours

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7
Q

What are CT scans not good to be used for?

A

Not good on soft tissue - not dense enough

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8
Q

How does tomography produce images?

A
  • Takes a series of 2D images through the body
  • 2D images can be computations reconstructed into 3D image

Like little slices of the brain

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9
Q

How does contract CT produce images?

A

Uses contrast agonist agesnt which are generally iodine rich

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10
Q

What is contract CT good for?

A

Blood vessels to determine the morphology of structures

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11
Q

What is computerised tomography angiograph (CTA)?

A

Uses both contract CT and X-ray to produce an image

The X-ray picks up the contrast agents in the blood

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12
Q

Contract CT can also measure perfunction, what is this?

A

Blood flow and blood volume

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13
Q

What was MRI originally developed as?

A

As a means of chemical analysis

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14
Q

What does MRI stand for?

A

Magnetic Resonance Imaging

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15
Q

Who developed MRI scans?

A

Sir Peter Mansfield

  • Nobel prize in 2003
  • By 2003, ~10,000 machines worldwide & 75,000,000 scans per year
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16
Q

How do MRI scans work?

A
  • Uses magnetic field and radio freq waves
  • MAG FIELD generated by very stong magnets
  • Certain atoms have magnetic properties called nuclear sping i.e. 1H and 13C
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17
Q

What does MRI primarily measure?

A

Water

Our body is made up of 60% H2O

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18
Q

How is an image generated using MRI?

(Part 1 - how protons work)

A
  • MAG FIELD aligns protons (H) in water molecules
  • Protons exist in 2 spin states

SPIN UP = aligned parallel to magnetic feild
SPIN DOWN = aligned antiparallel to magnetic field

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19
Q

What are the 2 states that protons exist in?

(Used for MRIs)

A

SPIN UP = aligned parallel to magnetic feild

SPIN DOWN = aligned antiparallel to magnetic field

20
Q

How is an image generated using MRI?

(Part 2 - radio)

A
  • Radio freq pulse applied –> Freq depends on strength of magnet = resonance
  • Proton absorb this energy shifting under their nuclear spin to a different position
  • The radio freq pulse is then turned off & protons release this energy & relax to their original alignments
  • Different protons are affected differently depending on the tissue they’re found iin
  • Energy released is detected by the imaging system
21
Q

What are the 2 types of MRI image you can produce?

A
  • T1 weighted
  • T2 weighted
22
Q

What is a T1 weighted MRI images like?

A
  • H2O appears black
  • Hight fat content appears white
  • VENTRICLES BLACK
23
Q

What are T2 weighted MRI images like?

A
  • H2O appears white
  • High fat content appears black
  • VENTRICLES WHITE
24
Q

What is MRI imaging good for?

A
  • Good for bones & soft tissues
  • Can take a series of images
25
Q

How can you use an MRI to visualise blood vessels?

A

Using contrast enhance MRI

Can be used to show angiography –> to see morphology & perfusion (blood flow & vol)

26
Q

How does contract enhance MRI work?

A

Uses Gadolinium as a contrast agent

Has strong magnetic properties & therefore produces a string MRI signal

27
Q

What does diffusion weighted MRI measure?

A

Measures water mobility within tissue WITHOUT need for contrast agents

28
Q

What condition is diffusion weighted MRI good for identifying?

A

Aids in the determination of acute ischemic stroke

29
Q

How can diffusion weighter MRI measure for ischemic stroke?

A
  • Water would be LESS likely to diffuse across regions that have sustained ischemic damage –> due to cytotoxic oedema (swelling)
  • This generates a hyperintense signal relative to surrounding tissue
30
Q

What does DTI stand for?

A

Diffusion Tensor Imaging

31
Q

What does DTI measure?

A

Measures water molecules that can only diffuse in one direction

32
Q

What is DTI good for measuring?

A

Detecting white matter in the brain

33
Q

What is the Red-green-bluecode used in DTI?

A

This method detects the direction of movement of water

Red = right to left
Green = anterior to posterior
Blue = dorsal to ventral

Colour intesity = magnitude of diffusion

34
Q

What sort of imaging does fMRI use?

A

BOLD imaging

35
Q

What does BOLD imaging stand for?

A

Blood Oxygen Level Dependent imaging

36
Q

How is BOLD imaging used in fMRI?

A
  • Oxyhaemoglin & deoxyhaemoglobin have different mag properties
  • BOLD measures changes in these forms of haemoglobin
  • Areas of inc acftivity = inc blood flow, in particular oxyhamoglobin
  • Low resolution BOLD img combined with highresolution MRI img
37
Q

What does PET scan stand for?

A

Positron Emission Tomography

38
Q

What do PET scans use to produce an image?

A

Use short lived radioactive isotpes - normally injected into the bloodstream

Show up areas where cells are more active

39
Q

How to PET scans produce an image?

A
  • Short lived radioactive isotopes injected
  • SHow up areas where cells are more active
  • As the isotopes decay they emit positron (positive electrons)
  • Positrons collide w electrons in the tissue forming photons
  • SCINTILLATION CRYSTALS in the scanner cameras around the patient detect the photons
  • 3D img of radioactivity constructed
40
Q

What does FDG stand for?

A

Fluorodeoxyglucose

41
Q

How does FDG produce an image?

A
  • Areas of inc activity = inc glucose metabolism
  • FDG glucose tagged w radioactive fluorine atom
  • Taken up but cells but not metabolised - accumulates areas of inc activity
42
Q

What is FDG?

A

It is glucose tagged w radioactive fluorine atom

43
Q

Summarise CT scans

A
  • High dose of X-ray (100x more than standard X-ray)
  • Low res
  • Fast
  • Cheaper than MRI
44
Q

Summarise MRI scans

A
  • Non-invasive (X-rays)
  • High res
  • Slower than CT
  • Expensive - magnets need to be cooled w liquid helium
45
Q

Summarise fMRI

A
  • Good res (2-3mm)
  • Rapid scanning
  • Non-invasive
  • Limitted activity measures - just BOLD
46
Q

Summarise PET scans

A
  • Poor res (5-10mm)
  • Slow scanning
  • Invasive - uses radioactive isotopes
  • Lots of activity measures - metabolism (FDG), blood flow (radioactive oxygen), receptors and NTs

Fundamentals of neuroscience (38 decks)

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