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Semester 5 PMNM Exam 3 > Neuroimaging > Flashcards

Neuroimaging Flashcards

1
Q

Magnetic Resonance Imaging - diagnostic tool that utilizes

A

a strong magnetic field and radio waves to produce an image

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2
Q

Focus of MRI is

A

hydrogen proton

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3
Q

Hydrogen is a primary constituent of

A

water

body tissue has high ratio of water - there is a supply of protons that can be manipulated with MRI

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4
Q

MRI units in a clinical setting are in the ___ to __ range

A

.5 to 3.0 Tesla

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5
Q

A MRI that is 1.5 T has a magnetic field strength that is how many times stronger than earth’s gravitational pull

A

30,000

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6
Q

what is a tesla

A

unit of magnetic field intensity equal to the magnitude of the magnetic field vector needed to produce a force of 1 newton on a charge of one coulomb moving perpendicular to the direction of the magnetic field vector with a velocity of 1 meter per second

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7
Q

Basis steps of what happens during an MRI - step 1 - 4

A
  1. hydrogen protons normally spin in random directions
    2 protons wobble in alignment with magnetic fields
    3 radio signal knocks the protons out of alignment
    4 when radio signal ceases, the protons snap back into alignment emitting a radio signal of their own - announces presence of a specific tissue
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8
Q

Basis steps of what happens during an MRI - step 1 - 4

radio signal soundwave frequency matches

A

the frequency of wobble of certain protons

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9
Q

How do radio frequencies work

A

radio wave moves protons out of alignment and then when stopped, protons go back and as they align they transmit an energy wave unique to that type of tissue

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10
Q

What is the T you read on an MRI report

A

based on time it takes for protons to realign or reach a state of equilibrium

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11
Q

T1 is related to

A

realignment with imposed magnetic fields

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12
Q

T2 is related to

A

the transverse energy pulses that are delivered and the spin dephasing that occurs

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13
Q

T1 and T2 weighted images differ based on what two parameters

A

time to echo (TE)

time to repetition (TR)

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14
Q

TE

A

time to echo - time from the application of a pulse (RF) to when the spin signal is picked up

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15
Q

TR

A

time to repetition - time between pulse (RF) frequencies

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16
Q

T1 weighted images have a ___ TE and TR

A

Short

Hence the tissue that emit energy more quickly tend to have a brighter image

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17
Q

Tissues that are slower to release (longer TE and TR) will appear

A

darker on T1?

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18
Q

T2 has ___ TE and TR times

A

longer

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19
Q

T2 picks up images of tissues that are slow to release energy - what falls in this category

A

tissue with high water content

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20
Q

Fat will appear ___ on a T1

A

bright

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21
Q

Water will appear __ on a T1

A

dark

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22
Q

On a T2 image fat will generate what kind of signal

A

a very low signal and will be dark

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23
Q

On a T2 image water will generate what kind of signal

A

high and will appear bright

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24
Q

Different MRI techniques - short T1 inversion recovery (STIR) - used to

A

used to suppress the signal from fat

25
Q

Different MRI techniques - short T1 inversion recovery (STIR) - allows improved imaging of what issues

A

inflammatory or neoplastic issues

26
Q

Different MRI techniques - Fluid attenuated inversion recovery (FLAIR) - allows for what

A

fluid signals to be nullified

27
Q

Different MRI techniques - Fluid attenuated inversion recovery (FLAIR) - useful in look at pathologies of the

A

CNS such as MS

28
Q

Gadolinium (Gd) - define

A

nontoxic paramagnetic contrast enhancement agent utilized in MRI
when injected will change signal intensities by shortening T1 in its surroundings

29
Q

T1 weighted - define

A

an image created typically by using short TE and TR times whose contrast and brightness are predominantly determined by T1 signals

30
Q

T2 weighted - define

A

image created typically by using longer TE and TR times whose contrast brightness are predominantly determined by T2 signals

31
Q

TAU (t) - define

A

the interpulse times used in a spin echo pulse sequence

32
Q

interpulse times

A

time between the 90 and 180 pulse, and between the 180 pulse and the echo

33
Q

TE define

A

echo time - time in milliseconds between the application of the 90 degre pulse and the peak of the echo signal in spin ech and inversion recovery pulse sequences

34
Q

Hyperintese

A

more intense, brighter

35
Q

hypointense

A

less intense, darker

36
Q

Isointense

A

the same intensity

37
Q

MRI indications

A 
Tumors
Stroke
Epilepsy
Demyelination
Infection
Cranial nerve palsy
Chronic HA
Dementia
38
Q

MRI advantages

A

1 good soft tissue contrast with normal tissue
2 customize imaging technique to answer a specific question
3 no ionizing radiation
4 directly image in any plane
5 ability to do functionl MRI

39
Q

MRI disadvantages

A 
1 high cost, limited access
2 difficult for unstable pt
3 clausrophobia
4 absolute contraindications
5 not great for bony detail
40
Q

Functional neuroimaging techniques

A

MEG
EEG
fMRI
PET

41
Q

MEG (Magnetoencephalography)
what is it
temporal and spatial resolution

A

Non invasive
measure cellular activity of the brain based on detection of magnetic field changes secondary to ion flow
Good temporal and spatial resolution

42
Q

MEG - used primarily with

A

cognitive research but can be used clinically for evaluation of seizures

43
Q

MEG combined with MRI

A

known as magnetic source imaging (MSI)

Used for pre-operative mapping

44
Q

Cost of MEG

A

high - limits the accessibility

45
Q

EEG (electroencephalography)

what is it

A

Records electrical activity of the brain using electrodes that are attached to the scalp
Captures electrical currents generated by activated neurons

46
Q

EEG temporal and spatial resolution

A

temporal is good but spatial is not as good as MEG

47
Q

Multichannel EEG

A

improved lacalization of events, particularly the more superficial activity

48
Q

EEG - cost

A

less than MEG so are more regularly used in clinical situations

49
Q

PET (positron emission tomography) and SPET (single photon emission tomography)

A

PET measures the metabolism of the tissue

as tissue activity inc there is an inc in demand for energy

50
Q

PET and SPET injects what into the body

A

radionuclide - 2 fluoro 2 deoxy D glucose (FDG)

This metabolizes and releases a beta particle called a positron

51
Q

Combination of PET and CT can improve what

A

localization of a lesion

52
Q

PET CT fusion imagine assists in differentiation of

A

pathologic tissue from normal tissue

53
Q

fMRI

A

indirect measure of neural activity

54
Q

fMRI is based on the

A

hemodynamic response related to neural activity

55
Q

fMRI makes use of MRI imaging physics to

A

trace a contrast medium
tracks the ratio of oxygenated to deoxygenated blood
this method is known as blood oxygen level dependent (BOLD) contrast

56
Q

BOLD contrast fMRI is based on fact that

A

magentic signal of oxygenated hemoglobin differs from deoxygenated

57
Q

fMRI BOLD contrast method uses the __ weighted process

A

T2

58
Q

Benefits to the BOLD contrast fMRI method

A

patient is not exposed to radiaion

provides both anatomic and function in one procedure

Semester 5 PMNM Exam 3 (2 decks)

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