MRI Imaging for the PA

Question 1

What does an MRI use to create its image?

Answer 1

molecular composition of tissues and a strong magnetic field to manipulate electrical activity of HYDROGEN atoms in the body

Question 2

When a patient enters an MRI machine, what direction does the protons current flow?

Answer 2

protons current will line up parallel to the main superconducting magnet of the MRI

Question 3

What are the coils of the magnet in the MRI responsible for?

Answer 3

Transmitting RF pulses

Receiving the signal or echo

Question 4

What happens when the RF pulse is transmitted by the transmitter coil?

Answer 4

protons are displaced from their original alignment

Question 5

Why is the superconduction magnet kept really cold?

Answer 5

to reduce the heat from the friction of the protons

Question 6

What do transmitter coils send?

Answer 6

a short magnetic pulse = RF pulse

Question 7

What happens when the RF pulse is turned off?

Answer 7

the protons realign in a parallel state to magnet and energy in the form of RF signals are released

Question 8

When the protons realign in a parallel state to the magnet after the RF pulse is turned off, what is this called?

Answer 8

recovery

Question 9

What is T1 relaxation?

Answer 9

Recovery; time it takes for the tissue to recover to parallel state

Question 10

What is the length of time for recovery and the echo called?

Answer 10

T1 and T2

Question 11

What is TE?

Answer 11

echo time

Question 12

What is TR?

Answer 12

repetition time

Question 13

What weighting does T1 have?

Answer 13

short TE of 10-20 s

short TR of 300-700 ms

Question 14

What appears white in T1 image?

Answer 14

Fat
Gadolinium
Proteinaceous Fluid
Melanin

Question 15

What is T2 relaxation?

Answer 15

Decay; time it takes for tissue to return to perpendicular to magnetic field

Question 16

What weighting does T2 have?

Answer 16

Short TE of 20 ms

LONG TR of 2000ms

Question 17

What is the mnemonic to for T2?

Answer 17

WWII - water white in 2

Question 18

What typically appears white in T2?

Answer 18

water
fat
edema
inflammation
infection
cyst
hemorrhage

Question 19

What vascular structures are enhanced with Gadolinium?

Answer 19

Tumors

Areas of inflammation

Question 20

What is the effect of Gadolinium?

Answer 20

shorten the T1 relaxation time of hydrogen nuclei to create a brighter signal

Question 21

How is Gadolinium excreted?

Answer 21

by the kidney

Question 22

What are some advantages of MRIs?

Answer 22

capable of high-resolution images in multiple planes

can provide detailed soft tissue characteristics

non-invasive

No known harmful effects

Question 23

What are some disadvantages of MRIs?

Answer 23

More expensive than xray or CT

Long scan time (30-45 min.)

Limited by multiple things

Question 24

What limits the use of an MRI?

Answer 24

patients body habitus
patient anxiety or pain
ferrous implants
Implanted pumps/electronic devices
contrast issues (allergy)

Question 25

What is the magnetic field strength of most MRIs?

Answer 25

0.5 to 3 Tesla

Question 26

What is Earth's magnetic field strength?

Answer 26

50 microT

Question 27

Which type of MRI machine gives a better quality image?

Answer 27

closed

Question 28

What is the magnetic field strength of open MRI machines?

Answer 28

0.1 to 1 T

Question 29

What procedures require the patient to be placed head first in to machine?

Answer 29

``` Head and Neck Chest Cervical Thoracic and Whole Spine Abdomen Shoulders and Upper Limb ```

Question 30

What procedures require the patient to be placed feet first in to machine?

Answer 30

Pelvis Hips Lower Limbs

Question 31

What are CT scans used for?

Answer 31

trauma to identify and characterize injury patterns and severity

Question 32

What is CT better than xray for diagnosing?

Answer 32

identifies subtle fractures Visualizes articular extension of fracture Assesses for the presence of articular step-off/gap

Question 33

What is MRI most used for?

Answer 33

PRIMARILY EVALUATION OF SOFT TISSUE diagnosing occult fractures concern for associated ligament or articular cartilage injury

Question 34

What is MRI the modality of choice for?

Answer 34

Disc Herniation | To assess "internal derangement" of joints

Question 35

What type of MRI images are occult fractures best visualized on?

Answer 35

T2 images in which the light up as edema of bone marrow

Question 36

Where do bone bruises appear on an MRI image?

Answer 36

In T2 weighted images as hyperintense signal

Question 37

What is an MRI standard for assessing of the spine?

Answer 37

spinal cord anatomy, tumors, or trauma PreOp eval. of pts. with spondylosis or disk herniation = MOC

Question 38

What does Gadolinium help with when used in MRI?

Answer 38

differentiates tissues receiving higher blood flow; infection, tumor, postsurgical scar