MRI Interpretation

Question 1

What is the physical property used in CT?

Answer 1

x-ray absorption

Question 2

what is the physical property used in ultrasound?

Answer 2

reflected sound

Question 3

what is the physical property used in MRI?

Answer 3

net magnetization

*it does NOT use ionizing radiation

Question 4

what is the term given to the H2 nuclei that align themselves parallel to the magnetic field?

Answer 4

B0 (B-knot)

Question 5

what is the term given for the cumulative magnetic force of H2 nuclei?

Answer 5

M vector

Question 6

As H2 nuclei return to their original energy state, what 2 things happen?

Answer 6

1. they release energy

2. the wobbling in phase becomes more random

Question 7

what happens to the longitudinal magnetization when the energy of protons are released?

Answer 7

long. mag. increases until it reaches its equilibrium value

Question 8

what happens to transverse magnetization as there is a loss of phase coherence?

Answer 8

transverse mag. decays to its equilibrium value of zero

Question 9

What is T1?

Answer 9

“longitudinal relaxation”-how fast a tissue loses its energy and returns to B0

Question 10

what is T2?

Answer 10

“transverse relaxation”- how slow/fast a tissue maintains its transverse magnetization

Question 11

What are the properties of the tissue type and CANNOT be changed by the operator of the MRI unit?

Answer 11

T1, T2, and density

Question 12

what properties can the operator manipulate on the MRI unit?

Answer 12

TR (repetition time)

TE (echo time)

Question 13

what is TR?

Answer 13

(repetition time)- the amt of time in ms allowed to elapse btwn successive 90 degree RF pulses

Question 14

what is TE?

Answer 14

(echo time)- is the time interval that elapses btwn a 90 degree RF pulse and measurement of the first spin echo signal

Question 15

what is spin-echo pulse sequence?

Answer 15

a single 90 degree pulse followed by one or more 180 degree pulses

Question 16

How are T1 images produced?

Answer 16

short TR - these are tissues (like fat) that return to B0 the fastest and gives off the most energy and appears bright (white) on T1 images

Question 17

which is the fat image? which is the water image?

Answer 17

T1- fat

T2- water

Question 18

In a T1 image, what color does fat appear?

Answer 18

fat = white
*water = black

Question 19

how are T2 images produced?

Answer 19

long TE - those tissues that hold their transverse magnetization longest give off the strongest signal and appear bright

Question 20

T1 images give off energy faster. T2 images hold onto energy longer.

Answer 20

true

Question 21

what should you dial in on the MRI to select for a T1 image?

Answer 21

short TR- <30 ms

Question 22

what should you dial in on MRI to select for T2 image?

Answer 22

long TR- >2000 ms

long TE- >60 ms

Question 23

which image is referred to as pathology image? which is anatomical image?

Answer 23

T1= anatomical image
T2= pathology image

Question 24

Describe the properties of tissues with high intensity signal.

Answer 24

• short T1
• long T2
• high proton density

Question 25

DEscribe the properties of tissues with low intensity signal.

Answer 25

- long T1 - short T2 - low proton density

Question 26

what is STIR imaging good for?

Answer 26

(short tau inversion recovery)- when you want the fat suppressed and want a max. highlighting of fluid

Question 27

what is gradient echo used for?

Answer 27

uses only one RF excitation pulse, at less than 90 degrees, when you need to cut down on T2 imaging time *good for ligaments and articular cartilage

Question 28

what disease is gradient echo good to diagnose?

Answer 28

pigmetned villonodular synovitis

Question 29

what can be used to identify fluid filled lesions?

Answer 29

(contrast gadolinium)- produces a rim sign surrounding the lesion

Question 30

the shorter the T1 of tissue, the brighter the image. what tissues does this apply to?

Answer 30

fat, methemoglobin, mucus

Question 31

the longer the T2 of the tissue, the brighter the image. what tissues does this apply to?

Answer 31

water, CSF

Question 32

what substances are always black (void of signal) on images produced by any pulse sequence?

Answer 32

calcium air flowing blood hemosiderin

Question 33

what structures always appear black because fo their relatively low water content?

Answer 33

``` tendons ligaments cartilage cortical bone *skeletal muscle- appears gray ```

Question 34

what color does marrow appear on T1 and T2?

Answer 34

T1- bright T2-dark (marrow has high content of fat)

Question 35

what are the contraindications for MRI?

Answer 35

patients with cardiac pacemakers, defibrillators, or cochlear implants - demagnetizing implants (dental implants, sphincters, stoma plugs, ocular implants) - bone growth stimulators - implantable electronic drug infusion pumps

Question 36

is MRI contraindicated in pregnancy?

Answer 36

no

Question 37

are orthopedic implants contraindicatd in pregnancy?

Answer 37

no

Question 38

intraocular metallic foreign bodies, pellets, and bullets from foreign countries, and shrapnel is contraindicated for use of MRI though

Answer 38

true

Question 39

in what order should you read T1 and T2 images?

Answer 39

read T2 before T1

Question 40

in what order should you read films based on the axis they are cut?

Answer 40

coronal/frontal, followed by transverse, followed by sagittal

Question 41

in what order should you view the different films?

Answer 41

coronal : proximal to distal transverse: inferior to superior sagittal: lateral to medial