Week 3.1 MRI

Question 1

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

Answer 1

90,000x

Question 2

what does the MRI magnetic field do

Answer 2

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

Question 3

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

Answer 3

hydrogen and other molecular content

Question 4

TF: MRI uses radiation

Answer 4

false

Question 5

what is the radio-frequency (RF) pulse

Answer 5

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

Question 6

what happens when the RF is turned off

Answer 6

detection of rotated spins

Question 7

what happens when the signal decays due to relaxation

Answer 7

subdivided into T1 and T2 phases.

Question 8

T1 recovery (____)

Answer 8

(Longitudinal)

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

Question 9

T2 decay (_____)

Answer 9

(Transverse)

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

Question 10

which is longer, T1 or T2

Answer 10

T1 is longer, because T2 is like a snap shot

Question 11

what is TE

Answer 11

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.

Question 12

what is TR

Answer 12

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

Question 13

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

Answer 13

false, they have different values

Question 14

RF pulses are repeated ___ of times during a study

Answer 14

100s

Question 15

what creates different types of images

Answer 15

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

Question 16

T1 has ___ TR and TE times

Answer 16

short

Question 17

T1 is created at ___ energy levels which means

Answer 17

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

Question 18

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

Answer 18

high signal intensity

Question 19

T2 has ___ TR and TE times

Answer 19

long

Question 20

T2 is created at ___ energy levels which means

Answer 20

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

Question 21

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

Answer 21

water, inflammation

Question 22

Difference between T1 and T2

Answer 22

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

Question 23

What is a saying to remember T2 and MRI

Answer 23

world war 2: white water type 2

H2O (water is white in Type 2)

Question 24

what has a high intensity in a T1 image

Answer 24

fat/yellow marrow

acute hemorrhage

Question 25

what has a high intensity in a T2 image

Answer 25

``` fluid, CSF, synovial fluid inflammation soft tissue tumors acute and stress fractures early and late AVN ```

Question 26

T1 looks at ____ and T2 looks at _____

Answer 26

anatomy | pathology (T2)

Question 27

how does fat look on a T1 vs T2

Answer 27

T1 white | T2 grey

Question 28

how does water look on a T1 vs T2

Answer 28

T1 grey | T2 white

Question 29

how does marrow look on a T1 vs T2

Answer 29

T1 bright | T2 grey

Question 30

how does cortex look on a T1 vs T2

Answer 30

T1 and T2 dark

Question 31

MRI sequences: SE

Answer 31

spin-echo pulse sequences, that gets T1 and T2

Question 32

GRE

Answer 32

gradient recalled echo sequences

Question 33

STIR

Answer 33

short T1 inversion recovery which suppresses fat

Question 34

FLAIR

Answer 34

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

Question 35

TIRM

Answer 35

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

Question 36

MRI contrast uses...

Answer 36

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

Question 37

how does implanted hardware or foreign bodies affect an MRI

Answer 37

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

Question 38

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

Answer 38

no

Question 39

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

Answer 39

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

Question 40

TF: pacemakers are not affected by an MRI

Answer 40

false, they are affected

Question 41

how long does an MRI take

Answer 41

30-60 minutes

Question 42

who may not like MRI

Answer 42

claustrophobic, pain, obese people

Question 43

how many Newtons of pull does an MRI machine have

Answer 43

200-600 N pull

Question 44

what are some MRI types

Answer 44

open and seated

Question 45

what are indications to do an MRI

Answer 45

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

Question 46

what are indications for a CT

Answer 46

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