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PATHO 2 > Neuroimaging > Flashcards

Neuroimaging Flashcards

1
Q

CT/ CAT Scanning

A

narrow beam x rays passing through tissue at different angles

used to detect brain disease

small structures cannot be distinguished

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2
Q

What color does bone, gasses/ liquids, and tissues in a CT/CAT scanning?

A

Bone= white (hyper-intensity)

gases and liquids= black (hypo- intensity)

Tissues= grey

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3
Q

CT/ CAT Scan Methodology: How many dimensions?

A

2-D measurement taken in a helical manner

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4
Q

How is x-ray intensity reduced?

A

Attenuation coefficient of the materials it passes through

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5
Q

What can you add to make internal organs more visible in a CT scan?

A

contrast dye

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6
Q

What is a tomographic image?

A

picture of a slab of the patient’s anatomy

2D CT image corresponds to to a 3D section of the patient

Each pixel on the CT image displays the average x-ray attenuation properties of the tissue in the corresponding voxel (volumetric pixel)

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7
Q

What is an MRI?

A

Magnetic Resonance Imaging

contains a magnetic field up to 60,000 times as strong as the Earth’s magnetic field

MRI equipment is VERY expensive

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8
Q

How does an MRI work?

A

Patient is bathed in a magnetic field

  • causes nuclei in the body to line up, spinning on it’s axis
  • atom= HYDROGREN ATOM
  • Protons are strongly affected by the magnetic field

The nuclei are hit by pulsing radio waves -> Resonance bit

  • Nuclei go back to their state induced by the magnet once RF pulses stop
  • Energy now released by the nuclei acts as a mini radio stations
  • The coil now picks up the excess energy and sends the signal to the computer, where the imaging is scanned
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9
Q

Can you inject contrast dye in patients during an MRI scan?

A

Yes. The dye will reach different tissues at different rates.

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10
Q

What can an MRI diagnose?

A
  • MS
  • strokes
  • infections of the brain/ spine/ tendonitis
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11
Q

MRI’s can visualize what?

A

Injuries:

- torn ligaments (wrist, ankle, knee)

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12
Q

What can MRI’s evaluate?

A

Masses in soft tissue

Cysts

Bone tumors

Disc problems

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13
Q

Advantages of an MRI

A
  • does not use ionizing radiation
  • contrast dye has low chance of side effects
  • non- invasive view before surgery
  • provides comparable resolution with far better CONTRAST RESOLUTION (distinguishing two different structures)
  • variable thickness, any plane
  • many details without IV contrast
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14
Q

What is spatial resolution? What type of imaging is good at this?

A

The ability to distinguish two separate structures an arbitrarily small distance from each other

CT

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15
Q

Disadvantages of MRI

A
  • Claustrophobia
  • Weight and size – pt limitations
  • Noise
  • Keeping still
  • Cost
  • Medical contraindications
  • Time consuming
  • not easily available
  • limitations
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16
Q

MRI contraindications

A
  • pace makers

- metal objects in the body

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17
Q

MRI limitations

A
  • bone
  • air pain abdomen?
  • time consuming
  • expertise
18
Q

MRI Safety Concerns

A
  • Internal cardiac pacemakers
  • steel cerebral aneurysm clips (ferromagnetic)
  • small steel silvers embedded in eye
  • cochlear implants
  • stents anywhere in the body

No phones or credit cards!!

19
Q

T1 Weighted MRI

A

Water and fluid containing tissues are dark

Fat containing tissues are bright

20
Q

T2 Weighted MRI

A

Water and fluid containing tissues are bright

Fat containing tissues are dark

  • Damaged tissue tends to develop edema, making T2 weighted sequence sensitive for pathology, and generally able to distinguish pathologic tissue from normal tissue
21
Q

FLAIR (MRI)

A

Fluid Attenuated Inversion Recovery
- achieved by additional manipulations of the magnetic field on a T2 weighted image

free water= dark
edematous tissue= bright

** MOST SENSISTIVE WAY to evaluate the brain for demyelinating diseases (ex: MS)

22
Q

What type of MRI provides good gray matter/ white matter contrast?

A

T1 Weighted Images highlight fat deposition

23
Q

What type of MRI is well suited to edema?

A

T2 Weighted Images light up liquid on the images being visualized— high water content

24
Q

What type of MRI targets blood vessels?

A

Magnetic Resonance Angiography (MRA)

- evaluates arteries for stenosis or aneurysms

25
Q

What type of imaging is used for the spine?

A

MRI, unless contraindicated

First line of investigation in suspected:

  • spinal infection
  • cord compression
  • cauda equina syndrome
  • sciatica
26
Q

What two factors limit functional neuroimaging?

A
  1. physical properties of the recording system

2. physiological constraints of the brain

27
Q

Functional Magnetic Resonance Imaging (fMRI)

A

Looks at function using oxygen uptake
- based on hemoglobin

Hemoglobin– diamagnetic when oxygenated and paramagnetic when deoxygenated

28
Q

fMRI strengths

A

non-invasive
good spatial localization
well validated technique

29
Q

fMRI limitations

A

mediocore temporal resolution
complex, highly variable data analyses
expensive and time consuming

30
Q

EEG

A

Electroencephalograph– detects electrical activity in the brain, using electrodes

Main diagnostic test for epilepsy and sleep disorders

** No risks, but not as spatially accurate as an fMRI

31
Q

Brain mapping for sever epilepsy/ seizure activity

A
  1. Temporal lobectomy (most common)
  2. Cortical Excision
  3. Hemispherectomy

** significant reduction/ complete seizure control

32
Q

MEG

A

Magnetoencephalograph— non-invasive neurophysiological technique that measures the magnetic fields generated by neuronal activity of the brain

  • direct measure of brain function
  • very high temporal resolution
  • no injections required
  • complementary to other modalities
33
Q

PET

A

Position Emission Tomography

  • nuclear medical imgaing technique
  • requires an injection of tracers into body, gamma rays are detected
  • gamma rays are converted into photons of light and electrical signals
  • signals convert into slices of images
34
Q

What can PET Scans show?

A
  • glucose metabolism in the brain
  • detects cancer
  • dementia
  • seizures
  • map brain function
35
Q

PET strengths

A
  • simple physiological mechanism
  • provides absolute, quantitative data
  • allows imaging of anything that can be tagged
36
Q

PET limitations

A
  • poor temporal resolution
  • poor spatial resolution
  • requires injection of radioactive material
37
Q

Wilson’s disease

A

HYPERINTENSITIES due to copper deposition in the bilateral basal ganglia and thalamus as shown by T2 weighted MRI of the brain

38
Q

Glioblastoma multiforme (GBM)

A

Seen as a grossly heterogenous mass

- ring enhancement surrounding necrotic center

39
Q

Basic features of brain lesions

A

Supratentorial space occupying– cerebrum

infratentorial space occupying – cerebellum

40
Q

Multiple sclerosis

A

White matter lesions are bright on T2 Weighted Images

PATHO 2 (4 decks)

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