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Advanced Diagnostics > Week 3.1 MRI > Flashcards

Week 3.1 MRI Flashcards

1
Q

an MRI magnetic field is _____x stronger then Earth’s magnetic field

A

90,000x

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2
Q

what does the MRI magnetic field do

A

align the atoms in the body, and the magnetic moment (or spin) aligns with the field (tissue specific based on hydrogen)

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3
Q

the file is lined up based on the tissue specificity which is due to

A

hydrogen and other molecular content

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4
Q

TF: MRI uses radiation

A

false

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5
Q

what is the radio-frequency (RF) pulse

A

emitted at 90 degree angles to the magnetic field. and deflects the spin of hydrogen atoms in the transverse plane

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6
Q

what happens when the RF is turned off

A

detection of rotated spins

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7
Q

what happens when the signal decays due to relaxation

A

subdivided into T1 and T2 phases.

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8
Q

T1 recovery (____)

A

(Longitudinal)

time it takes for spins to realign with original magnetic field (how long to resting state)

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9
Q

T2 decay (_____)

A

(Transverse)

time it takes for the spin to lose energy in the transverse plane

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10
Q

which is longer, T1 or T2

A

T1 is longer, because T2 is like a snap shot

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11
Q

what is TE

A

echo time, this is after the original pulse. A spin echo is created by applying a refocusing RF that flips the spin 180 degrees, and the spin realigns and produces a signal peak at TE.

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12
Q

what is TR

A

repetition time, or the time between successive 90 degree angle RF pulses.

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13
Q

TF: T1 and T2 have the same TE and TR values

A

false, they have different values

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14
Q

RF pulses are repeated ___ of times during a study

A

100s

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15
Q

what creates different types of images

A

varying of pulse timing creates different TE and TR, which produces different types of images

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16
Q

T1 has ___ TR and TE times

A

short

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17
Q

T1 is created at ___ energy levels which means

A

high energy levels, which means good anatomic detail, and the tissues with lower relaxation times

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18
Q

what kind of signal intensity do you get in fat with a T1 view

A

high signal intensity

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19
Q

T2 has ___ TR and TE times

A

long

20
Q

T2 is created at ___ energy levels which means

A

low, which means tissues with longer relaxation times, and grainer and less spatial resolution compared to T1.

21
Q

T2 images have high signal intensity in ___, making it valuable when looking for ____

A

water, inflammation

22
Q

Difference between T1 and T2

A

T1 is detailed, and more anatomic detail, and T2 is grainy, but shows bright white where there is inflammation

23
Q

What is a saying to remember T2 and MRI

A

world war 2: white water type 2

H2O (water is white in Type 2)

24
Q

what has a high intensity in a T1 image

A

fat/yellow marrow

acute hemorrhage

25
Q

what has a high intensity in a T2 image

A 
fluid, CSF, synovial fluid
inflammation 
soft tissue tumors
acute and stress fractures
early and late AVN
26
Q

T1 looks at ____ and T2 looks at _____

A

anatomy

pathology (T2)

27
Q

how does fat look on a T1 vs T2

A

T1 white

T2 grey

28
Q

how does water look on a T1 vs T2

A

T1 grey

T2 white

29
Q

how does marrow look on a T1 vs T2

A

T1 bright

T2 grey

30
Q

how does cortex look on a T1 vs T2

A

T1 and T2 dark

31
Q

MRI sequences: SE

A

spin-echo pulse sequences, that gets T1 and T2

32
Q

GRE

A

gradient recalled echo sequences

33
Q

STIR

A

short T1 inversion recovery which suppresses fat

34
Q

FLAIR

A

fluid attenuation inversion recovery, which suppresses water, so it is good for imaging of the brain and CNS

35
Q

TIRM

A

turbo inversion recovery magnitude, used to assess osteomyelitis in the bone and head and neck tumors.

36
Q

MRI contrast uses…

A

gadolinium, which is an IV injection, that decreases the signal on T2 weighted image, and increases the signal of T1 weighted images.

37
Q

how does implanted hardware or foreign bodies affect an MRI

A

most ortho hardware is not magnetized, so you can still get an MRI, even after TKA/THA, but you will get artifact locally

38
Q

can you get an MRI if you have pedicle screws in your Low back

A

no

39
Q

if you suspect things that will interfere or be bad in an MRI, what can you do

A

pre-MRI x-ray, especially if you suspect shrapnel or metal

40
Q

TF: pacemakers are not affected by an MRI

A

false, they are affected

41
Q

how long does an MRI take

A

30-60 minutes

42
Q

who may not like MRI

A

claustrophobic, pain, obese people

43
Q

how many Newtons of pull does an MRI machine have

A

200-600 N pull

44
Q

what are some MRI types

A

open and seated

45
Q

what are indications to do an MRI

A 
soft tissues
ligaments, tendon, muscle, cartilage, 
vascular demyelinating diseases
neoplasm, infection, inflammation and seizure 
post acute CVA, TIA, dementia
46
Q

what are indications for a CT

A

cortical bone, chest, abdomen or pelvis
fracture, lose bodies,
bony stenosis
occult fractures in patients with osteoporosis
initial eval of CVA, trauma or hemorrhage

Advanced Diagnostics (20 decks)

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