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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
disadvantage of T2
decreased soft tissue detail
26
STIR stands for
short TI inversion recovery
27
what is STIR
a technique used to suppress the signal from fat. it allows improved imaging of inflammatory or neoplastic tissues
28
FLAIR stands for
fluid-attenuated inversion recovery
29
what is FLAIR
allows fluid signals to be nullified. this is useful in looking at pathologies of the CNS such as MS
30
define gadolinium
a non-toxic paramagnetic contrast enhancement agent used in MRI. when injected it will change signal intensities by shortening T1
31
define T1 weighted
an image created by using short TE and TR times whose contrast and brightness are determined by T1 signals
32
define T2 weighted
an image created by longer TE and TR times whose contrast and brightness are determined by T2 signals
33
define hyperintense
more intense/brighter
34
define hypointense
less intense/darker
35
define isotense
the same intensity as the ____ (words missing on the PP)
36
indications of MRI
- tumors - stroke - epilepsy - demyelination - infection - CN palsy - chronic headache - dementia
37
advantage of MRI (related to tissue)
- exquisite soft tissue contrast between normal tissue (white/gray matter) and pathologic tissue
38
advantage of MRI (image)
customize imaging techniques to answer specific questions
39
advantage of MRI (3 more)
- no ionizing radiation - directly image in any plane - ability to do functional MRI
40
5 disadvantages of MRI
1. high cost, limited access 2. difficult for unstable pts 3. claustrophobia 4. absolute contraindications 5. not great for bony detail
41
what does MEG stand for
magnetoencephalography
42
MEG
- non invasive technique - measures cellular activity of the brain based on the detections of MF changes - good temporal/spatial resolution
43
MEG is used for what in the clinic and in research?
in cognitive research but is useful clinically for evaluating seizures
44
when MEG is combined with MRI what is it used for
pre-operative brain mapping
45
cost of MEG?
high, therefore accessibility is limited
46
EEG stands for
electroencephalography
47
EEG does what
records the electoral activity of the brain using electrodes attached to the scalp
48
EEG captures what
the electrical currents generated by activated neurons
49
EEG
- good temporal resolution but spatial resolution not as good as MEG - EEGs detect superficial activity
50
EEG vs MEG clinically
EEG used more often because they cost less
51
PEt stands for
positron emission tomography
52
SPET stands for
single photon emission tomography
53
PET measures what
the metabolism of the tissue. radionuclide is injected into the body
54
PET + CT help with what
improve the localization of a lesion. assists with differentiating normal from pathologic tissue
55
fMRI is a measure of what
it is an indirect measure of neural activity
56
fMRI based on what
the hemodynamic response related to neural activity
57
fMRI uses MRI imaging physics to trace a contrast medium. what does it track
the ratio of oxygenated to deoxygenated blood via BOLD contrast
58
what is bold contrast
blood oxygen level dependent contrast - uses T2 weighted process
59
advantages of BOLD contrast with fMRI
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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