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MD4001 Clinical > Neuroimaging > Flashcards

Neuroimaging Flashcards

1
Q

What factors should you consider in imaging?

A
  • Anatomy and structure
  • Symmetry
  • Incidentalomas (something that is a surprise/not meant to be there)
  • Availability (e.g rural areas)
  • Practicality and cost (cheaper and quicker to acquire than MRIs)
  • Side effects
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2
Q

WHat are the different planes of the body?

A
  • Sagittal
  • Transverse
  • Coronal
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3
Q

What is the increase in dosage of radiation in a CT scan of the head in comparison with a CXR?

A

200x more

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4
Q

What view is a CT?

A

Caudal view

  • Looking from feet
  • L/R are opposite
  • Slightly diagonal
  • Orbitomeatal line
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5
Q

What is the age affect?

A
  • Normal atrophy of the brain with age
  • Alcohol and trauma can accelerate
  • May be disproportionate for age - neurodegenerative disorders
  • Ventricles become larger
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6
Q

What is denser/lighter on a CT; white or grey matter?

A
  • Grey is denser/lighter than white
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7
Q

What is denser/lighter on a CT; CSF or water?

A

CSF

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8
Q

What is the darker shade on a CT in and around the eye?

A

Retrobulbar fat

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9
Q

What does the falx cerebri do?

A

Divides frontal lobe into left and right

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10
Q

What is at risk of herniating down into the foramen magnum when the intracranial pressure is raised?

A

Uncus of temporal lobe

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11
Q

What does the tentorium cerebelli do?

A

Extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes

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12
Q

What does the cerebellar vermis do?

A

Connects left and right sides of cerebellum

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13
Q

What structure divides the lateral ventricles?

A

Septum pellucidum

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14
Q

What do the sylvian/lateral fissures do?

A

Divide temporal lobes from the frontal and parietal lobes

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15
Q

Where is the CSf filled quadrigeminal cistern located?

A

Dorsal wall of midbrain

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16
Q

What is the head of the caudate nucleus and lentiform nucleus divided by?

A

Internal capsule

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17
Q

What does ABCS refer to when interpreting MRIs and CTs of the brain?

A
  • A - adequacy, alignment, artefact
  • B - bones, blood, brain
  • C - cisterns and ventricles
  • S - subcutaneous and surfaces, symmetry
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18
Q

What does artefact apply to?

A
  • Beam hardening artefact - posterior fossa particularly , streaking like from bone
  • Motion - confused patient, children causes a mass of grey often
  • Medical - metal clips, intraventricular shunts can cause a bright glare around the tissue
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19
Q

What does a bone window mean?

A
  • Allows us to get a clearer view of the bones in the skull (focus on higher range of Hounsfield Units/HU)
  • Good when looking at trauma to the skull
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20
Q

What does a extradural haematoma look like on a CT?

A
  • Between skull and outer layer of dura

- Biconvex - limited by cranial sutures forms lens like shape

21
Q

What does a subdural haematoma look like?

A
  • Between dura and arachnoid
  • Crescent - limited only by dural reflections (falx/tentorium)
  • Can be chronic or acute
22
Q

What can cause a subdural haematoma?

A

A fall (elderly patient, sports injury)

23
Q

What is a diffuse axonal injury?

A
  • Traumatic brain injury, due to shearing forces
  • Poor grey-white matter differentiation, loss of sulci
  • Brain expands
  • May be associated with haemorrhage
  • Management largely supportive
24
Q

Where does the blood collect in a subarachnoid haemorrhage?

A

Cisterns (looks like a star)

25
Q

What does obstructive hydrocephalus look like?

A

Blockage in ventricular system causing huge enlargement of lateral ventricles

26
Q

How is hydrocephalus treated surgically?

A

Interventricular shunt (hole in skull and tube in ventricle to drain off the excess CSF)

27
Q

What do you look for when looking at S - subcutaneous and soft tissue?

A
  • Skin/subcutaneous lesions (e.g epidermal cyst)
  • Orbit (e.g melanoma mestastasis, greyish structure behind globe)
  • Sinuses (e.g maxillary sinusitis)
  • Nasopharynx and oropharynx
28
Q

What is a ring-enhancing lesion?

A
  • Abnormal radiologic sign on MRI or CT scans obtained using radiocontrast
  • Tumour or abscess?
  • MRI required to differntiate further
29
Q

What can a ring-enhancing lesion with a thick and solid part on the ring?

A

Tumour

30
Q

Describe a meningioma?

A
  • Typically benign
  • slow-growing
  • Patient often asymptomatic - tumour discovered incidentally
  • Good prognosis following surgical removal
  • Homogenous, well circumscribed, broad dural base
31
Q

What percentage of strokes are haemorrhagic?

A

~15%

32
Q

What are the risk factors for a stroke?

A
  • Hypertension
  • Ischaemic stroke (haemorrhagic transformation)
  • Anticoagulation
  • Amyloid angiopathy
33
Q

What percentage of strokes are ischaemic?

A

~ 85%

34
Q

What is an ischaemic stroke?

A
  • Blockage of cerebral arteries causes ischaemia of brain tissue
  • Thrombus may be seen as hyperdensity on scan
35
Q

What is the Monroe-Kellie doctrine?

A

The sum of volumes of brain, CSF and intracerebral blood is constant

36
Q

Is the age affect more marked in CT or MRI?

A

MRI

  • Superior soft tissue contrast - much more detail
  • White matter hyperintensities allowed ~1 per decade (more suggests neurodegenerative disorder)
37
Q

What plane can an MRI be looked at though?

A

Any plane (usually looked at caudal view)

38
Q

What should be considered before an MRI?

A

Safety

  • Pacemakers
  • Cochlear implants
  • Metal around eyes/head
39
Q

What does a scanner measure in an MRI?

A

The speed at which protons return to their initial axis along the magnetic field. Different levels of speed = different contrasts

40
Q

What are the different weights for an MRI?

A

T1: best for structural imaging,
- Water is dark, grey matter is darker than white matter
T2: good for identifying pathology - inflammation, oedema
- Water is light, white matter is darker than grey matter
- WW2 - Water White T2

41
Q

What are DWI - diffusion weighted MRI and ADC - apparent diffusion coefficient?

A
  • For acute strokes - show highlighted area that stroke has affected (less diffusion)
  • DWI - T2-based sequence that measures diffusion of water within tissues
  • ADC - calculated from DWI, shows pure diffusion
  • Acute stroke - highlighted
42
Q

What is better at looking at bone MRI and CT?

A

CT

43
Q

What can a venous sinus thrombosis be seen on?

A

MR venogram

44
Q

What can increase the chances of a venous sinus thrombosis?

A

Pregnancy and oral contraceptive pill use

45
Q

What does MS look like on imaging?

A
  • White matter plaques can appear anywhere in CNS (brain or spinal cord)
  • T2/FLAIR - Hyperintense
  • T1 - Hypointense black holes, hyper in advanced disease
46
Q

What can an MRI scan of the spinal cord be useful for ?

A

Diagnosing caudia equina syndrome

47
Q

What is tractography?

A
  • Shows direction of travel of white matter tracts using color imaging
  • Mostly used in research to see how different lesions can affect the brain
48
Q

WHat does nuclear imaging (SPECT and PET) show?

A
  • Involves injecing the patient with a radioactive substance
  • Radioactive substance highlights areas of biological activity (high blood flow)

MD4001 Clinical (4 decks)

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