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Semester 5 PMNM Exam 3 > Diagnostic Imaging > Flashcards

Diagnostic Imaging Flashcards

1
Q

what is an MRI?

A

a diagnostic tool that utilizes a strong magnetic field and radio waves to produce an image

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2
Q

what is the focus of the procedure with MRI?

A

the focus is the hydrogen proton. Hydrogen is a primary constituent of water. Body tissue has a high ratio of water, therefore there is a ready supply of protons that can be manipulated.

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3
Q

MRI units

A

.05-3.0 Tesla (ex: 1.5 T MRI = magnetic field strength 30,000x stronger than the earth’s gravitational pull)

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4
Q

What is a tesla?

A

A unit of measure associated with magnetic fields

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5
Q

step 1 of MRI

A

Positively charged hydrogen protons spin in random directions

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6
Q

step 2 MRI

A

protons wobble in alignment with MF’s of varying intensity

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7
Q

step 3 MRI

A

a brief radio signal knocks the protons out of alignment

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8
Q

step 4 MRI

A

protons snap back into alignment with the MF when the radio signal ceases. this emits a radio signal of their own that announces the presence of a specific tissue

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9
Q

radio frequency info

A

as the protons move back into alignment after the radio wave stops, the protons transmit an energy wave that is unique to a certain type of tissue

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10
Q

“T” in MRI reports

A

based on the time it takes for protons to realign or reach states of equilibrium

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11
Q

T1

A

related to the realignment with the imposed magnetic fields

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12
Q

T2

A

related to 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 2 parameters?

A

1) Time to Echo (TE)

2) Time to Repetition (TR)

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14
Q

define TE

A

time to echo

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

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15
Q

define TR

A

time to repetition

- the time between pulse (RF) sequences

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16
Q

T/F T1 weighted images have a short TE and TR

A

true, meaning tissue that emits energy more quickly tends to have a brighter image

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17
Q

T/F tissues that are slower to release energy will be darker

A

true

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18
Q

these 3 things pick up images of tissues that are slow to release energy

A
  1. T2
  2. longer TE and TR times
  3. tissue with high water content
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19
Q

on T1, what appears bright? what appears dark? (1 thing each)

A

fat appears bright

water appears dark

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20
Q

on T2, what appears bright and what appears dark? (1thing each)

A

fat generates a low signal and will appear dark for T2

water has a high T2 signal and appears bright

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21
Q

6 steps to MRI (summary)

A
  1. pt placed in scanner
  2. MF aligns protons w/ pt
  3. EM pulse is sent into scanner and causes protons to reorient
  4. pulse turns off and protons relax
  5. as protons relax, they emit a RF signal that is picked up by the antenna in the scanner
  6. signal processed by the computer and software creates images
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22
Q

T2 is moderately sensitive for detecting what 2 things?

A

pathology and edema

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23
Q

disadvantage of T1

A

poor demonstration (image) of pathology/edema

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24
Q

advantage of T1

A

provides the best anatomic detail

25
Q

disadvantage of T2

A

decreased soft tissue detail

26
Q

STIR stands for

A

short TI inversion recovery

27
Q

what is STIR

A

a technique used to suppress the signal from fat. it allows improved imaging of inflammatory or neoplastic tissues

28
Q

FLAIR stands for

A

fluid-attenuated inversion recovery

29
Q

what is FLAIR

A

allows fluid signals to be nullified. this is useful in looking at pathologies of the CNS such as MS

30
Q

define gadolinium

A

a non-toxic paramagnetic contrast enhancement agent used in MRI. when injected it will change signal intensities by shortening T1

31
Q

define T1 weighted

A

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

32
Q

define T2 weighted

A

an image created by longer TE and TR times whose contrast and brightness are determined by T2 signals

33
Q

define hyperintense

A

more intense/brighter

34
Q

define hypointense

A

less intense/darker

35
Q

define isotense

A

the same intensity as the ____ (words missing on the PP)

36
Q

indications of MRI

A
  • tumors
  • stroke
  • epilepsy
  • demyelination
  • infection
  • CN palsy
  • chronic headache
  • dementia
37
Q

advantage of MRI (related to tissue)

A
  • exquisite soft tissue contrast between normal tissue (white/gray matter) and pathologic tissue
38
Q

advantage of MRI (image)

A

customize imaging techniques to answer specific questions

39
Q

advantage of MRI (3 more)

A
  • no ionizing radiation
  • directly image in any plane
  • ability to do functional MRI
40
Q

5 disadvantages of MRI

A
  1. high cost, limited access
  2. difficult for unstable pts
  3. claustrophobia
  4. absolute contraindications
  5. not great for bony detail
41
Q

what does MEG stand for

A

magnetoencephalography

42
Q

MEG

A
  • non invasive technique
  • measures cellular activity of the brain based on the detections of MF changes
  • good temporal/spatial resolution
43
Q

MEG is used for what in the clinic and in research?

A

in cognitive research but is useful clinically for evaluating seizures

44
Q

when MEG is combined with MRI what is it used for

A

pre-operative brain mapping

45
Q

cost of MEG?

A

high, therefore accessibility is limited

46
Q

EEG stands for

A

electroencephalography

47
Q

EEG does what

A

records the electoral activity of the brain using electrodes attached to the scalp

48
Q

EEG captures what

A

the electrical currents generated by activated neurons

49
Q

EEG

A
  • good temporal resolution but spatial resolution not as good as MEG
  • EEGs detect superficial activity
50
Q

EEG vs MEG clinically

A

EEG used more often because they cost less

51
Q

PEt stands for

A

positron emission tomography

52
Q

SPET stands for

A

single photon emission tomography

53
Q

PET measures what

A

the metabolism of the tissue. radionuclide is injected into the body

54
Q

PET + CT help with what

A

improve the localization of a lesion. assists with differentiating normal from pathologic tissue

55
Q

fMRI is a measure of what

A

it is an indirect measure of neural activity

56
Q

fMRI based on what

A

the hemodynamic response related to neural activity

57
Q

fMRI uses MRI imaging physics to trace a contrast medium. what does it track

A

the ratio of oxygenated to deoxygenated blood via BOLD contrast

58
Q

what is bold contrast

A

blood oxygen level dependent contrast - uses T2 weighted process

59
Q

advantages of BOLD contrast with fMRI

A

the patient is not exposed to radiation. provides anatomic and function in one procedure and __ (slides cut off again…)

Semester 5 PMNM Exam 3 (1 decks)

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